1 // ignore-tidy-filelength
7 Within the check phase of type check, we check each item one at a time
8 (bodies of function expressions are checked as part of the containing
9 function). Inference is used to supply types wherever they are unknown.
11 By far the most complex case is checking the body of a function. This
12 can be broken down into several distinct phases:
14 - gather: creates type variables to represent the type of each local
15 variable and pattern binding.
17 - main: the main pass does the lion's share of the work: it
18 determines the types of all expressions, resolves
19 methods, checks for most invalid conditions, and so forth. In
20 some cases, where a type is unknown, it may create a type or region
21 variable and use that as the type of an expression.
23 In the process of checking, various constraints will be placed on
24 these type variables through the subtyping relationships requested
25 through the `demand` module. The `infer` module is in charge
26 of resolving those constraints.
28 - regionck: after main is complete, the regionck pass goes over all
29 types looking for regions and making sure that they did not escape
30 into places they are not in scope. This may also influence the
31 final assignments of the various region variables if there is some
34 - vtable: find and records the impls to use for each trait bound that
35 appears on a type parameter.
37 - writeback: writes the final types within a function body, replacing
38 type variables with their final inferred types. These final types
39 are written into the `tcx.node_types` table, which should *never* contain
40 any reference to a type variable.
44 While type checking a function, the intermediate types for the
45 expressions, blocks, and so forth contained within the function are
46 stored in `fcx.node_types` and `fcx.node_substs`. These types
47 may contain unresolved type variables. After type checking is
48 complete, the functions in the writeback module are used to take the
49 types from this table, resolve them, and then write them into their
50 permanent home in the type context `tcx`.
52 This means that during inferencing you should use `fcx.write_ty()`
53 and `fcx.expr_ty()` / `fcx.node_ty()` to write/obtain the types of
54 nodes within the function.
56 The types of top-level items, which never contain unbound type
57 variables, are stored directly into the `tcx` tables.
59 N.B., a type variable is not the same thing as a type parameter. A
60 type variable is rather an "instance" of a type parameter: that is,
61 given a generic function `fn foo<T>(t: T)`: while checking the
62 function `foo`, the type `ty_param(0)` refers to the type `T`, which
63 is treated in abstract. When `foo()` is called, however, `T` will be
64 substituted for a fresh type variable `N`. This variable will
65 eventually be resolved to some concrete type (which might itself be
84 mod generator_interior;
88 use crate::astconv::{AstConv, PathSeg};
89 use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
90 use rustc::hir::{self, ExprKind, GenericArg, ItemKind, Node, PatKind, QPath};
91 use rustc::hir::def::{CtorOf, CtorKind, Def};
92 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
93 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
94 use rustc::hir::itemlikevisit::ItemLikeVisitor;
95 use crate::middle::lang_items;
96 use crate::namespace::Namespace;
97 use rustc::infer::{self, InferCtxt, InferOk, InferResult};
98 use rustc::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
99 use rustc_data_structures::indexed_vec::Idx;
100 use rustc_data_structures::sync::Lrc;
101 use rustc_target::spec::abi::Abi;
102 use rustc::infer::opaque_types::OpaqueTypeDecl;
103 use rustc::infer::type_variable::{TypeVariableOrigin};
104 use rustc::middle::region;
105 use rustc::mir::interpret::{ConstValue, GlobalId};
106 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
108 self, AdtKind, CanonicalUserType, Ty, TyCtxt, GenericParamDefKind, Visibility,
109 ToPolyTraitRef, ToPredicate, RegionKind, UserType
111 use rustc::ty::adjustment::{
112 Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast
114 use rustc::ty::fold::TypeFoldable;
115 use rustc::ty::query::Providers;
116 use rustc::ty::subst::{UnpackedKind, Subst, InternalSubsts, SubstsRef, UserSelfTy, UserSubsts};
117 use rustc::ty::util::{Representability, IntTypeExt, Discr};
118 use rustc::ty::layout::VariantIdx;
119 use syntax_pos::{self, BytePos, Span, MultiSpan};
122 use syntax::feature_gate::{GateIssue, emit_feature_err};
124 use syntax::source_map::{DUMMY_SP, original_sp};
125 use syntax::symbol::{Symbol, LocalInternedString, keywords};
126 use syntax::util::lev_distance::find_best_match_for_name;
128 use std::cell::{Cell, RefCell, Ref, RefMut};
129 use std::collections::hash_map::Entry;
131 use std::fmt::Display;
133 use std::mem::replace;
134 use std::ops::{self, Deref};
137 use crate::require_c_abi_if_c_variadic;
138 use crate::session::Session;
139 use crate::session::config::EntryFnType;
140 use crate::TypeAndSubsts;
142 use crate::util::captures::Captures;
143 use crate::util::common::{ErrorReported, indenter};
144 use crate::util::nodemap::{DefIdMap, DefIdSet, FxHashMap, FxHashSet, HirIdMap};
146 pub use self::Expectation::*;
147 use self::autoderef::Autoderef;
148 use self::callee::DeferredCallResolution;
149 use self::coercion::{CoerceMany, DynamicCoerceMany};
150 pub use self::compare_method::{compare_impl_method, compare_const_impl};
151 use self::method::{MethodCallee, SelfSource};
152 use self::TupleArgumentsFlag::*;
154 /// The type of a local binding, including the revealed type for anon types.
155 #[derive(Copy, Clone)]
156 pub struct LocalTy<'tcx> {
158 revealed_ty: Ty<'tcx>
161 /// A wrapper for `InferCtxt`'s `in_progress_tables` field.
162 #[derive(Copy, Clone)]
163 struct MaybeInProgressTables<'a, 'tcx: 'a> {
164 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
167 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
168 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
169 match self.maybe_tables {
170 Some(tables) => tables.borrow(),
172 bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables")
177 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
178 match self.maybe_tables {
179 Some(tables) => tables.borrow_mut(),
181 bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables")
187 /// Closures defined within the function. For example:
190 /// bar(move|| { ... })
193 /// Here, the function `foo()` and the closure passed to
194 /// `bar()` will each have their own `FnCtxt`, but they will
195 /// share the inherited fields.
196 pub struct Inherited<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
197 infcx: InferCtxt<'a, 'gcx, 'tcx>,
199 tables: MaybeInProgressTables<'a, 'tcx>,
201 locals: RefCell<HirIdMap<LocalTy<'tcx>>>,
203 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
205 // Some additional `Sized` obligations badly affect type inference.
206 // These obligations are added in a later stage of typeck.
207 deferred_sized_obligations: RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
209 // When we process a call like `c()` where `c` is a closure type,
210 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
211 // `FnOnce` closure. In that case, we defer full resolution of the
212 // call until upvar inference can kick in and make the
213 // decision. We keep these deferred resolutions grouped by the
214 // def-id of the closure, so that once we decide, we can easily go
215 // back and process them.
216 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'gcx, 'tcx>>>>,
218 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
220 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>)>>,
222 // Opaque types found in explicit return types and their
223 // associated fresh inference variable. Writeback resolves these
224 // variables to get the concrete type, which can be used to
225 // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
226 opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
228 /// Each type parameter has an implicit region bound that
229 /// indicates it must outlive at least the function body (the user
230 /// may specify stronger requirements). This field indicates the
231 /// region of the callee. If it is `None`, then the parameter
232 /// environment is for an item or something where the "callee" is
234 implicit_region_bound: Option<ty::Region<'tcx>>,
236 body_id: Option<hir::BodyId>,
239 impl<'a, 'gcx, 'tcx> Deref for Inherited<'a, 'gcx, 'tcx> {
240 type Target = InferCtxt<'a, 'gcx, 'tcx>;
241 fn deref(&self) -> &Self::Target {
246 /// When type-checking an expression, we propagate downward
247 /// whatever type hint we are able in the form of an `Expectation`.
248 #[derive(Copy, Clone, Debug)]
249 pub enum Expectation<'tcx> {
250 /// We know nothing about what type this expression should have.
253 /// This expression should have the type given (or some subtype).
254 ExpectHasType(Ty<'tcx>),
256 /// This expression will be cast to the `Ty`.
257 ExpectCastableToType(Ty<'tcx>),
259 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
260 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
261 ExpectRvalueLikeUnsized(Ty<'tcx>),
264 impl<'a, 'gcx, 'tcx> Expectation<'tcx> {
265 // Disregard "castable to" expectations because they
266 // can lead us astray. Consider for example `if cond
267 // {22} else {c} as u8` -- if we propagate the
268 // "castable to u8" constraint to 22, it will pick the
269 // type 22u8, which is overly constrained (c might not
270 // be a u8). In effect, the problem is that the
271 // "castable to" expectation is not the tightest thing
272 // we can say, so we want to drop it in this case.
273 // The tightest thing we can say is "must unify with
274 // else branch". Note that in the case of a "has type"
275 // constraint, this limitation does not hold.
277 // If the expected type is just a type variable, then don't use
278 // an expected type. Otherwise, we might write parts of the type
279 // when checking the 'then' block which are incompatible with the
281 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
283 ExpectHasType(ety) => {
284 let ety = fcx.shallow_resolve(ety);
285 if !ety.is_ty_var() {
291 ExpectRvalueLikeUnsized(ety) => {
292 ExpectRvalueLikeUnsized(ety)
298 /// Provides an expectation for an rvalue expression given an *optional*
299 /// hint, which is not required for type safety (the resulting type might
300 /// be checked higher up, as is the case with `&expr` and `box expr`), but
301 /// is useful in determining the concrete type.
303 /// The primary use case is where the expected type is a fat pointer,
304 /// like `&[isize]`. For example, consider the following statement:
306 /// let x: &[isize] = &[1, 2, 3];
308 /// In this case, the expected type for the `&[1, 2, 3]` expression is
309 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
310 /// expectation `ExpectHasType([isize])`, that would be too strong --
311 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
312 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
313 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
314 /// which still is useful, because it informs integer literals and the like.
315 /// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
316 /// for examples of where this comes up,.
317 fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
318 match fcx.tcx.struct_tail(ty).sty {
319 ty::Slice(_) | ty::Str | ty::Dynamic(..) => {
320 ExpectRvalueLikeUnsized(ty)
322 _ => ExpectHasType(ty)
326 // Resolves `expected` by a single level if it is a variable. If
327 // there is no expected type or resolution is not possible (e.g.,
328 // no constraints yet present), just returns `None`.
329 fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
331 NoExpectation => NoExpectation,
332 ExpectCastableToType(t) => {
333 ExpectCastableToType(fcx.resolve_type_vars_if_possible(&t))
335 ExpectHasType(t) => {
336 ExpectHasType(fcx.resolve_type_vars_if_possible(&t))
338 ExpectRvalueLikeUnsized(t) => {
339 ExpectRvalueLikeUnsized(fcx.resolve_type_vars_if_possible(&t))
344 fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
345 match self.resolve(fcx) {
346 NoExpectation => None,
347 ExpectCastableToType(ty) |
349 ExpectRvalueLikeUnsized(ty) => Some(ty),
353 /// It sometimes happens that we want to turn an expectation into
354 /// a **hard constraint** (i.e., something that must be satisfied
355 /// for the program to type-check). `only_has_type` will return
356 /// such a constraint, if it exists.
357 fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
358 match self.resolve(fcx) {
359 ExpectHasType(ty) => Some(ty),
360 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
364 /// Like `only_has_type`, but instead of returning `None` if no
365 /// hard constraint exists, creates a fresh type variable.
366 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>, span: Span) -> Ty<'tcx> {
367 self.only_has_type(fcx)
368 .unwrap_or_else(|| fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span)))
372 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
379 fn maybe_mut_place(m: hir::Mutability) -> Self {
381 hir::MutMutable => Needs::MutPlace,
382 hir::MutImmutable => Needs::None,
387 #[derive(Copy, Clone)]
388 pub struct UnsafetyState {
390 pub unsafety: hir::Unsafety,
391 pub unsafe_push_count: u32,
396 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
397 UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
400 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
401 match self.unsafety {
402 // If this unsafe, then if the outer function was already marked as
403 // unsafe we shouldn't attribute the unsafe'ness to the block. This
404 // way the block can be warned about instead of ignoring this
405 // extraneous block (functions are never warned about).
406 hir::Unsafety::Unsafe if self.from_fn => *self,
409 let (unsafety, def, count) = match blk.rules {
410 hir::PushUnsafeBlock(..) =>
411 (unsafety, blk.hir_id, self.unsafe_push_count.checked_add(1).unwrap()),
412 hir::PopUnsafeBlock(..) =>
413 (unsafety, blk.hir_id, self.unsafe_push_count.checked_sub(1).unwrap()),
414 hir::UnsafeBlock(..) =>
415 (hir::Unsafety::Unsafe, blk.hir_id, self.unsafe_push_count),
417 (unsafety, self.def, self.unsafe_push_count),
421 unsafe_push_count: count,
428 #[derive(Debug, Copy, Clone)]
434 /// Tracks whether executing a node may exit normally (versus
435 /// return/break/panic, which "diverge", leaving dead code in their
436 /// wake). Tracked semi-automatically (through type variables marked
437 /// as diverging), with some manual adjustments for control-flow
438 /// primitives (approximating a CFG).
439 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
441 /// Potentially unknown, some cases converge,
442 /// others require a CFG to determine them.
445 /// Definitely known to diverge and therefore
446 /// not reach the next sibling or its parent.
449 /// Same as `Always` but with a reachability
450 /// warning already emitted.
454 // Convenience impls for combinig `Diverges`.
456 impl ops::BitAnd for Diverges {
458 fn bitand(self, other: Self) -> Self {
459 cmp::min(self, other)
463 impl ops::BitOr for Diverges {
465 fn bitor(self, other: Self) -> Self {
466 cmp::max(self, other)
470 impl ops::BitAndAssign for Diverges {
471 fn bitand_assign(&mut self, other: Self) {
472 *self = *self & other;
476 impl ops::BitOrAssign for Diverges {
477 fn bitor_assign(&mut self, other: Self) {
478 *self = *self | other;
483 fn always(self) -> bool {
484 self >= Diverges::Always
488 pub struct BreakableCtxt<'gcx: 'tcx, 'tcx> {
491 // this is `null` for loops where break with a value is illegal,
492 // such as `while`, `for`, and `while let`
493 coerce: Option<DynamicCoerceMany<'gcx, 'tcx>>,
496 pub struct EnclosingBreakables<'gcx: 'tcx, 'tcx> {
497 stack: Vec<BreakableCtxt<'gcx, 'tcx>>,
498 by_id: HirIdMap<usize>,
501 impl<'gcx, 'tcx> EnclosingBreakables<'gcx, 'tcx> {
502 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'gcx, 'tcx> {
503 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
504 bug!("could not find enclosing breakable with id {}", target_id);
510 pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
513 /// The parameter environment used for proving trait obligations
514 /// in this function. This can change when we descend into
515 /// closures (as they bring new things into scope), hence it is
516 /// not part of `Inherited` (as of the time of this writing,
517 /// closures do not yet change the environment, but they will
519 param_env: ty::ParamEnv<'tcx>,
521 // Number of errors that had been reported when we started
522 // checking this function. On exit, if we find that *more* errors
523 // have been reported, we will skip regionck and other work that
524 // expects the types within the function to be consistent.
525 err_count_on_creation: usize,
527 ret_coercion: Option<RefCell<DynamicCoerceMany<'gcx, 'tcx>>>,
528 ret_coercion_span: RefCell<Option<Span>>,
530 yield_ty: Option<Ty<'tcx>>,
532 ps: RefCell<UnsafetyState>,
534 /// Whether the last checked node generates a divergence (e.g.,
535 /// `return` will set this to `Always`). In general, when entering
536 /// an expression or other node in the tree, the initial value
537 /// indicates whether prior parts of the containing expression may
538 /// have diverged. It is then typically set to `Maybe` (and the
539 /// old value remembered) for processing the subparts of the
540 /// current expression. As each subpart is processed, they may set
541 /// the flag to `Always`, etc. Finally, at the end, we take the
542 /// result and "union" it with the original value, so that when we
543 /// return the flag indicates if any subpart of the parent
544 /// expression (up to and including this part) has diverged. So,
545 /// if you read it after evaluating a subexpression `X`, the value
546 /// you get indicates whether any subexpression that was
547 /// evaluating up to and including `X` diverged.
549 /// We currently use this flag only for diagnostic purposes:
551 /// - To warn about unreachable code: if, after processing a
552 /// sub-expression but before we have applied the effects of the
553 /// current node, we see that the flag is set to `Always`, we
554 /// can issue a warning. This corresponds to something like
555 /// `foo(return)`; we warn on the `foo()` expression. (We then
556 /// update the flag to `WarnedAlways` to suppress duplicate
557 /// reports.) Similarly, if we traverse to a fresh statement (or
558 /// tail expression) from a `Always` setting, we will issue a
559 /// warning. This corresponds to something like `{return;
560 /// foo();}` or `{return; 22}`, where we would warn on the
563 /// An expression represents dead code if, after checking it,
564 /// the diverges flag is set to something other than `Maybe`.
565 diverges: Cell<Diverges>,
567 /// Whether any child nodes have any type errors.
568 has_errors: Cell<bool>,
570 enclosing_breakables: RefCell<EnclosingBreakables<'gcx, 'tcx>>,
572 inh: &'a Inherited<'a, 'gcx, 'tcx>,
575 impl<'a, 'gcx, 'tcx> Deref for FnCtxt<'a, 'gcx, 'tcx> {
576 type Target = Inherited<'a, 'gcx, 'tcx>;
577 fn deref(&self) -> &Self::Target {
582 /// Helper type of a temporary returned by `Inherited::build(...)`.
583 /// Necessary because we can't write the following bound:
584 /// `F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(Inherited<'b, 'gcx, 'tcx>)`.
585 pub struct InheritedBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
586 infcx: infer::InferCtxtBuilder<'a, 'gcx, 'tcx>,
590 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
591 pub fn build(tcx: TyCtxt<'a, 'gcx, 'gcx>, def_id: DefId)
592 -> InheritedBuilder<'a, 'gcx, 'tcx> {
593 let hir_id_root = if def_id.is_local() {
594 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
595 DefId::local(hir_id.owner)
601 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
607 impl<'a, 'gcx, 'tcx> InheritedBuilder<'a, 'gcx, 'tcx> {
608 fn enter<F, R>(&'tcx mut self, f: F) -> R
609 where F: for<'b> FnOnce(Inherited<'b, 'gcx, 'tcx>) -> R
611 let def_id = self.def_id;
612 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
616 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
617 fn new(infcx: InferCtxt<'a, 'gcx, 'tcx>, def_id: DefId) -> Self {
619 let item_id = tcx.hir().as_local_hir_id(def_id);
620 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by_by_hir_id(id));
621 let implicit_region_bound = body_id.map(|body_id| {
622 let body = tcx.hir().body(body_id);
623 tcx.mk_region(ty::ReScope(region::Scope {
624 id: body.value.hir_id.local_id,
625 data: region::ScopeData::CallSite
630 tables: MaybeInProgressTables {
631 maybe_tables: infcx.in_progress_tables,
634 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
635 locals: RefCell::new(Default::default()),
636 deferred_sized_obligations: RefCell::new(Vec::new()),
637 deferred_call_resolutions: RefCell::new(Default::default()),
638 deferred_cast_checks: RefCell::new(Vec::new()),
639 deferred_generator_interiors: RefCell::new(Vec::new()),
640 opaque_types: RefCell::new(Default::default()),
641 implicit_region_bound,
646 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
647 debug!("register_predicate({:?})", obligation);
648 if obligation.has_escaping_bound_vars() {
649 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}",
654 .register_predicate_obligation(self, obligation);
657 fn register_predicates<I>(&self, obligations: I)
658 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>>
660 for obligation in obligations {
661 self.register_predicate(obligation);
665 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
666 self.register_predicates(infer_ok.obligations);
670 fn normalize_associated_types_in<T>(&self,
673 param_env: ty::ParamEnv<'tcx>,
675 where T : TypeFoldable<'tcx>
677 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
678 self.register_infer_ok_obligations(ok)
682 struct CheckItemTypesVisitor<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx> }
684 impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'a, 'tcx> {
685 fn visit_item(&mut self, i: &'tcx hir::Item) {
686 check_item_type(self.tcx, i);
688 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
689 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
692 pub fn check_wf_new<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Result<(), ErrorReported> {
693 tcx.sess.track_errors(|| {
694 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
695 tcx.hir().krate().par_visit_all_item_likes(&mut visit);
699 fn check_mod_item_types<'tcx>(tcx: TyCtxt<'_, 'tcx, 'tcx>, module_def_id: DefId) {
700 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
703 fn typeck_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum) {
704 debug_assert!(crate_num == LOCAL_CRATE);
705 tcx.par_body_owners(|body_owner_def_id| {
706 tcx.ensure().typeck_tables_of(body_owner_def_id);
710 fn check_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
711 wfcheck::check_item_well_formed(tcx, def_id);
714 fn check_trait_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
715 wfcheck::check_trait_item(tcx, def_id);
718 fn check_impl_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
719 wfcheck::check_impl_item(tcx, def_id);
722 pub fn provide(providers: &mut Providers<'_>) {
723 method::provide(providers);
724 *providers = Providers {
730 check_item_well_formed,
731 check_trait_item_well_formed,
732 check_impl_item_well_formed,
733 check_mod_item_types,
738 fn adt_destructor<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
740 -> Option<ty::Destructor> {
741 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
744 /// If this `DefId` is a "primary tables entry", returns `Some((body_id, decl))`
745 /// with information about it's body-id and fn-decl (if any). Otherwise,
748 /// If this function returns "some", then `typeck_tables(def_id)` will
749 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
750 /// may not succeed. In some cases where this function returns `None`
751 /// (notably closures), `typeck_tables(def_id)` would wind up
752 /// redirecting to the owning function.
753 fn primary_body_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
755 -> Option<(hir::BodyId, Option<&'tcx hir::FnDecl>)>
757 match tcx.hir().get_by_hir_id(id) {
758 Node::Item(item) => {
760 hir::ItemKind::Const(_, body) |
761 hir::ItemKind::Static(_, _, body) =>
763 hir::ItemKind::Fn(ref decl, .., body) =>
764 Some((body, Some(decl))),
769 Node::TraitItem(item) => {
771 hir::TraitItemKind::Const(_, Some(body)) =>
773 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
774 Some((body, Some(&sig.decl))),
779 Node::ImplItem(item) => {
781 hir::ImplItemKind::Const(_, body) =>
783 hir::ImplItemKind::Method(ref sig, body) =>
784 Some((body, Some(&sig.decl))),
789 Node::AnonConst(constant) => Some((constant.body, None)),
794 fn has_typeck_tables<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
797 // Closures' tables come from their outermost function,
798 // as they are part of the same "inference environment".
799 let outer_def_id = tcx.closure_base_def_id(def_id);
800 if outer_def_id != def_id {
801 return tcx.has_typeck_tables(outer_def_id);
804 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
805 primary_body_of(tcx, id).is_some()
808 fn used_trait_imports<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
811 tcx.typeck_tables_of(def_id).used_trait_imports.clone()
814 fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
816 -> &'tcx ty::TypeckTables<'tcx> {
817 // Closures' tables come from their outermost function,
818 // as they are part of the same "inference environment".
819 let outer_def_id = tcx.closure_base_def_id(def_id);
820 if outer_def_id != def_id {
821 return tcx.typeck_tables_of(outer_def_id);
824 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
825 let span = tcx.hir().span_by_hir_id(id);
827 // Figure out what primary body this item has.
828 let (body_id, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
829 span_bug!(span, "can't type-check body of {:?}", def_id);
831 let body = tcx.hir().body(body_id);
833 let tables = Inherited::build(tcx, def_id).enter(|inh| {
834 let param_env = tcx.param_env(def_id);
835 let fcx = if let Some(decl) = fn_decl {
836 let fn_sig = tcx.fn_sig(def_id);
838 check_abi(tcx, span, fn_sig.abi());
840 // Compute the fty from point of view of inside the fn.
842 tcx.liberate_late_bound_regions(def_id, &fn_sig);
844 inh.normalize_associated_types_in(body.value.span,
849 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
852 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
853 let expected_type = tcx.type_of(def_id);
854 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
855 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
857 let revealed_ty = if tcx.features().impl_trait_in_bindings {
858 fcx.instantiate_opaque_types_from_value(
866 // Gather locals in statics (because of block expressions).
867 GatherLocalsVisitor { fcx: &fcx, parent_id: id, }.visit_body(body);
869 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
871 fcx.write_ty(id, revealed_ty);
876 // All type checking constraints were added, try to fallback unsolved variables.
877 fcx.select_obligations_where_possible(false);
878 let mut fallback_has_occurred = false;
879 for ty in &fcx.unsolved_variables() {
880 fallback_has_occurred |= fcx.fallback_if_possible(ty);
882 fcx.select_obligations_where_possible(fallback_has_occurred);
884 // Even though coercion casts provide type hints, we check casts after fallback for
885 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
888 // Closure and generator analysis may run after fallback
889 // because they don't constrain other type variables.
890 fcx.closure_analyze(body);
891 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
892 fcx.resolve_generator_interiors(def_id);
894 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
895 let ty = fcx.normalize_ty(span, ty);
896 fcx.require_type_is_sized(ty, span, code);
898 fcx.select_all_obligations_or_error();
900 if fn_decl.is_some() {
901 fcx.regionck_fn(id, body);
903 fcx.regionck_expr(body);
906 fcx.resolve_type_vars_in_body(body)
909 // Consistency check our TypeckTables instance can hold all ItemLocalIds
910 // it will need to hold.
911 assert_eq!(tables.local_id_root, Some(DefId::local(id.owner)));
916 fn check_abi<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, abi: Abi) {
917 if !tcx.sess.target.target.is_abi_supported(abi) {
918 struct_span_err!(tcx.sess, span, E0570,
919 "The ABI `{}` is not supported for the current target", abi).emit()
923 struct GatherLocalsVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
924 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
925 parent_id: hir::HirId,
928 impl<'a, 'gcx, 'tcx> GatherLocalsVisitor<'a, 'gcx, 'tcx> {
929 fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
932 // infer the variable's type
933 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
934 self.fcx.locals.borrow_mut().insert(nid, LocalTy {
941 // take type that the user specified
942 self.fcx.locals.borrow_mut().insert(nid, typ);
949 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for GatherLocalsVisitor<'a, 'gcx, 'tcx> {
950 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
951 NestedVisitorMap::None
954 // Add explicitly-declared locals.
955 fn visit_local(&mut self, local: &'gcx hir::Local) {
956 let local_ty = match local.ty {
958 let o_ty = self.fcx.to_ty(&ty);
960 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
961 self.fcx.instantiate_opaque_types_from_value(
969 let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(
970 &UserType::Ty(revealed_ty)
972 debug!("visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
973 ty.hir_id, o_ty, revealed_ty, c_ty);
974 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
976 Some(LocalTy { decl_ty: o_ty, revealed_ty })
980 self.assign(local.span, local.hir_id, local_ty);
982 debug!("Local variable {:?} is assigned type {}",
984 self.fcx.ty_to_string(
985 self.fcx.locals.borrow().get(&local.hir_id).unwrap().clone().decl_ty));
986 intravisit::walk_local(self, local);
989 // Add pattern bindings.
990 fn visit_pat(&mut self, p: &'gcx hir::Pat) {
991 if let PatKind::Binding(_, _, ident, _) = p.node {
992 let var_ty = self.assign(p.span, p.hir_id, None);
994 let node_id = self.fcx.tcx.hir().hir_to_node_id(p.hir_id);
995 if !self.fcx.tcx.features().unsized_locals {
996 self.fcx.require_type_is_sized(var_ty, p.span,
997 traits::VariableType(node_id));
1000 debug!("Pattern binding {} is assigned to {} with type {:?}",
1002 self.fcx.ty_to_string(
1003 self.fcx.locals.borrow().get(&p.hir_id).unwrap().clone().decl_ty),
1006 intravisit::walk_pat(self, p);
1009 // Don't descend into the bodies of nested closures
1010 fn visit_fn(&mut self, _: intravisit::FnKind<'gcx>, _: &'gcx hir::FnDecl,
1011 _: hir::BodyId, _: Span, _: hir::HirId) { }
1013 fn visit_argument_source(&mut self, s: &'gcx hir::ArgSource) {
1015 // Don't visit the pattern in `ArgSource::AsyncFn`, it contains a pattern which has
1016 // a `NodeId` w/out a type, as it is only used for getting the name of the original
1017 // pattern for diagnostics where only an `hir::Arg` is present.
1018 hir::ArgSource::AsyncFn(..) => {},
1019 _ => intravisit::walk_argument_source(self, s),
1024 /// When `check_fn` is invoked on a generator (i.e., a body that
1025 /// includes yield), it returns back some information about the yield
1027 struct GeneratorTypes<'tcx> {
1028 /// Type of value that is yielded.
1029 yield_ty: ty::Ty<'tcx>,
1031 /// Types that are captured (see `GeneratorInterior` for more).
1032 interior: ty::Ty<'tcx>,
1034 /// Indicates if the generator is movable or static (immovable).
1035 movability: hir::GeneratorMovability,
1038 /// Helper used for fns and closures. Does the grungy work of checking a function
1039 /// body and returns the function context used for that purpose, since in the case of a fn item
1040 /// there is still a bit more to do.
1043 /// * inherited: other fields inherited from the enclosing fn (if any)
1044 fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
1045 param_env: ty::ParamEnv<'tcx>,
1046 fn_sig: ty::FnSig<'tcx>,
1047 decl: &'gcx hir::FnDecl,
1049 body: &'gcx hir::Body,
1050 can_be_generator: Option<hir::GeneratorMovability>)
1051 -> (FnCtxt<'a, 'gcx, 'tcx>, Option<GeneratorTypes<'tcx>>)
1053 let mut fn_sig = fn_sig.clone();
1055 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1057 // Create the function context. This is either derived from scratch or,
1058 // in the case of closures, based on the outer context.
1059 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1060 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1062 let declared_ret_ty = fn_sig.output();
1063 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1064 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(fn_id, &declared_ret_ty);
1065 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1066 fn_sig = fcx.tcx.mk_fn_sig(
1067 fn_sig.inputs().iter().cloned(),
1074 let span = body.value.span;
1076 if body.is_generator && can_be_generator.is_some() {
1077 let yield_ty = fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
1078 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1079 fcx.yield_ty = Some(yield_ty);
1082 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id_from_hir_id(fn_id));
1083 let outer_hir_id = fcx.tcx.hir().as_local_hir_id(outer_def_id).unwrap();
1084 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id, }.visit_body(body);
1086 // Add formal parameters.
1087 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
1088 // Check the pattern.
1092 ty::BindingMode::BindByValue(hir::Mutability::MutImmutable),
1096 // Check that argument is Sized.
1097 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1098 // for simple cases like `fn foo(x: Trait)`,
1099 // where we would error once on the parameter as a whole, and once on the binding `x`.
1100 if arg.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1101 fcx.require_type_is_sized(arg_ty, decl.output.span(), traits::SizedArgumentType);
1104 fcx.write_ty(arg.hir_id, arg_ty);
1107 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1109 fcx.check_return_expr(&body.value);
1111 // We insert the deferred_generator_interiors entry after visiting the body.
1112 // This ensures that all nested generators appear before the entry of this generator.
1113 // resolve_generator_interiors relies on this property.
1114 let gen_ty = if can_be_generator.is_some() && body.is_generator {
1115 let interior = fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span));
1116 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior));
1117 Some(GeneratorTypes {
1118 yield_ty: fcx.yield_ty.unwrap(),
1120 movability: can_be_generator.unwrap(),
1126 // Finalize the return check by taking the LUB of the return types
1127 // we saw and assigning it to the expected return type. This isn't
1128 // really expected to fail, since the coercions would have failed
1129 // earlier when trying to find a LUB.
1131 // However, the behavior around `!` is sort of complex. In the
1132 // event that the `actual_return_ty` comes back as `!`, that
1133 // indicates that the fn either does not return or "returns" only
1134 // values of type `!`. In this case, if there is an expected
1135 // return type that is *not* `!`, that should be ok. But if the
1136 // return type is being inferred, we want to "fallback" to `!`:
1138 // let x = move || panic!();
1140 // To allow for that, I am creating a type variable with diverging
1141 // fallback. This was deemed ever so slightly better than unifying
1142 // the return value with `!` because it allows for the caller to
1143 // make more assumptions about the return type (e.g., they could do
1145 // let y: Option<u32> = Some(x());
1147 // which would then cause this return type to become `u32`, not
1149 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1150 let mut actual_return_ty = coercion.complete(&fcx);
1151 if actual_return_ty.is_never() {
1152 actual_return_ty = fcx.next_diverging_ty_var(
1153 TypeVariableOrigin::DivergingFn(span));
1155 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1157 // Check that the main return type implements the termination trait.
1158 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1159 if let Some((def_id, EntryFnType::Main)) = fcx.tcx.entry_fn(LOCAL_CRATE) {
1160 let main_id = fcx.tcx.hir().as_local_hir_id(def_id).unwrap();
1161 if main_id == fn_id {
1162 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1163 let trait_ref = ty::TraitRef::new(term_id, substs);
1164 let return_ty_span = decl.output.span();
1165 let cause = traits::ObligationCause::new(
1166 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1168 inherited.register_predicate(
1169 traits::Obligation::new(
1170 cause, param_env, trait_ref.to_predicate()));
1175 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1176 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1177 if panic_impl_did == fcx.tcx.hir().local_def_id_from_hir_id(fn_id) {
1178 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1179 // at this point we don't care if there are duplicate handlers or if the handler has
1180 // the wrong signature as this value we'll be used when writing metadata and that
1181 // only happens if compilation succeeded
1182 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1184 if declared_ret_ty.sty != ty::Never {
1185 fcx.tcx.sess.span_err(
1187 "return type should be `!`",
1191 let inputs = fn_sig.inputs();
1192 let span = fcx.tcx.hir().span_by_hir_id(fn_id);
1193 if inputs.len() == 1 {
1194 let arg_is_panic_info = match inputs[0].sty {
1195 ty::Ref(region, ty, mutbl) => match ty.sty {
1196 ty::Adt(ref adt, _) => {
1197 adt.did == panic_info_did &&
1198 mutbl == hir::Mutability::MutImmutable &&
1199 *region != RegionKind::ReStatic
1206 if !arg_is_panic_info {
1207 fcx.tcx.sess.span_err(
1208 decl.inputs[0].span,
1209 "argument should be `&PanicInfo`",
1213 if let Node::Item(item) = fcx.tcx.hir().get_by_hir_id(fn_id) {
1214 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1215 if !generics.params.is_empty() {
1216 fcx.tcx.sess.span_err(
1218 "should have no type parameters",
1224 let span = fcx.tcx.sess.source_map().def_span(span);
1225 fcx.tcx.sess.span_err(span, "function should have one argument");
1228 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1233 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1234 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1235 if alloc_error_handler_did == fcx.tcx.hir().local_def_id_from_hir_id(fn_id) {
1236 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1237 if declared_ret_ty.sty != ty::Never {
1238 fcx.tcx.sess.span_err(
1240 "return type should be `!`",
1244 let inputs = fn_sig.inputs();
1245 let span = fcx.tcx.hir().span_by_hir_id(fn_id);
1246 if inputs.len() == 1 {
1247 let arg_is_alloc_layout = match inputs[0].sty {
1248 ty::Adt(ref adt, _) => {
1249 adt.did == alloc_layout_did
1254 if !arg_is_alloc_layout {
1255 fcx.tcx.sess.span_err(
1256 decl.inputs[0].span,
1257 "argument should be `Layout`",
1261 if let Node::Item(item) = fcx.tcx.hir().get_by_hir_id(fn_id) {
1262 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1263 if !generics.params.is_empty() {
1264 fcx.tcx.sess.span_err(
1266 "`#[alloc_error_handler]` function should have no type \
1273 let span = fcx.tcx.sess.source_map().def_span(span);
1274 fcx.tcx.sess.span_err(span, "function should have one argument");
1277 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1285 fn check_struct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1288 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1289 let def = tcx.adt_def(def_id);
1290 def.destructor(tcx); // force the destructor to be evaluated
1291 check_representable(tcx, span, def_id);
1293 if def.repr.simd() {
1294 check_simd(tcx, span, def_id);
1297 check_transparent(tcx, span, def_id);
1298 check_packed(tcx, span, def_id);
1301 fn check_union<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1304 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1305 let def = tcx.adt_def(def_id);
1306 def.destructor(tcx); // force the destructor to be evaluated
1307 check_representable(tcx, span, def_id);
1309 check_packed(tcx, span, def_id);
1312 fn check_opaque<'a, 'tcx>(
1313 tcx: TyCtxt<'a, 'tcx, 'tcx>,
1315 substs: SubstsRef<'tcx>,
1318 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1319 let mut err = struct_span_err!(
1320 tcx.sess, span, E0720,
1321 "opaque type expands to a recursive type",
1323 err.span_label(span, "expands to self-referential type");
1324 if let ty::Opaque(..) = partially_expanded_type.sty {
1325 err.note("type resolves to itself");
1327 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1333 pub fn check_item_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item) {
1335 "check_item_type(it.hir_id={}, it.name={})",
1337 tcx.def_path_str(tcx.hir().local_def_id_from_hir_id(it.hir_id))
1339 let _indenter = indenter();
1341 // Consts can play a role in type-checking, so they are included here.
1342 hir::ItemKind::Static(..) => {
1343 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1344 tcx.typeck_tables_of(def_id);
1345 maybe_check_static_with_link_section(tcx, def_id, it.span);
1347 hir::ItemKind::Const(..) => {
1348 tcx.typeck_tables_of(tcx.hir().local_def_id_from_hir_id(it.hir_id));
1350 hir::ItemKind::Enum(ref enum_definition, _) => {
1351 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1353 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1354 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1355 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1356 let impl_def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1357 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1358 check_impl_items_against_trait(
1365 let trait_def_id = impl_trait_ref.def_id;
1366 check_on_unimplemented(tcx, trait_def_id, it);
1369 hir::ItemKind::Trait(..) => {
1370 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1371 check_on_unimplemented(tcx, def_id, it);
1373 hir::ItemKind::Struct(..) => {
1374 check_struct(tcx, it.hir_id, it.span);
1376 hir::ItemKind::Union(..) => {
1377 check_union(tcx, it.hir_id, it.span);
1379 hir::ItemKind::Existential(..) => {
1380 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1382 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1383 check_opaque(tcx, def_id, substs, it.span);
1385 hir::ItemKind::Ty(..) => {
1386 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1387 let pty_ty = tcx.type_of(def_id);
1388 let generics = tcx.generics_of(def_id);
1389 check_bounds_are_used(tcx, &generics, pty_ty);
1391 hir::ItemKind::ForeignMod(ref m) => {
1392 check_abi(tcx, it.span, m.abi);
1394 if m.abi == Abi::RustIntrinsic {
1395 for item in &m.items {
1396 intrinsic::check_intrinsic_type(tcx, item);
1398 } else if m.abi == Abi::PlatformIntrinsic {
1399 for item in &m.items {
1400 intrinsic::check_platform_intrinsic_type(tcx, item);
1403 for item in &m.items {
1404 let generics = tcx.generics_of(tcx.hir().local_def_id_from_hir_id(item.hir_id));
1405 if generics.params.len() - generics.own_counts().lifetimes != 0 {
1406 let mut err = struct_span_err!(
1410 "foreign items may not have type parameters"
1412 err.span_label(item.span, "can't have type parameters");
1413 // FIXME: once we start storing spans for type arguments, turn this into a
1416 "use specialization instead of type parameters by replacing them \
1417 with concrete types like `u32`",
1422 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.node {
1423 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1428 _ => { /* nothing to do */ }
1432 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_, '_, '_>, id: DefId, span: Span) {
1433 // Only restricted on wasm32 target for now
1434 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1438 // If `#[link_section]` is missing, then nothing to verify
1439 let attrs = tcx.codegen_fn_attrs(id);
1440 if attrs.link_section.is_none() {
1444 // For the wasm32 target statics with #[link_section] are placed into custom
1445 // sections of the final output file, but this isn't link custom sections of
1446 // other executable formats. Namely we can only embed a list of bytes,
1447 // nothing with pointers to anything else or relocations. If any relocation
1448 // show up, reject them here.
1449 let instance = ty::Instance::mono(tcx, id);
1450 let cid = GlobalId {
1454 let param_env = ty::ParamEnv::reveal_all();
1455 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1456 let alloc = if let ConstValue::ByRef(_, allocation) = static_.val {
1459 bug!("Matching on non-ByRef static")
1461 if alloc.relocations.len() != 0 {
1462 let msg = "statics with a custom `#[link_section]` must be a \
1463 simple list of bytes on the wasm target with no \
1464 extra levels of indirection such as references";
1465 tcx.sess.span_err(span, msg);
1470 fn check_on_unimplemented<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1471 trait_def_id: DefId,
1473 let item_def_id = tcx.hir().local_def_id_from_hir_id(item.hir_id);
1474 // an error would be reported if this fails.
1475 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1478 fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1479 impl_item: &hir::ImplItem,
1482 let mut err = struct_span_err!(
1483 tcx.sess, impl_item.span, E0520,
1484 "`{}` specializes an item from a parent `impl`, but \
1485 that item is not marked `default`",
1487 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1490 match tcx.span_of_impl(parent_impl) {
1492 err.span_label(span, "parent `impl` is here");
1493 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1497 err.note(&format!("parent implementation is in crate `{}`", cname));
1504 fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1505 trait_def: &ty::TraitDef,
1506 trait_item: &ty::AssociatedItem,
1508 impl_item: &hir::ImplItem)
1510 let ancestors = trait_def.ancestors(tcx, impl_id);
1512 let kind = match impl_item.node {
1513 hir::ImplItemKind::Const(..) => ty::AssociatedKind::Const,
1514 hir::ImplItemKind::Method(..) => ty::AssociatedKind::Method,
1515 hir::ImplItemKind::Existential(..) => ty::AssociatedKind::Existential,
1516 hir::ImplItemKind::Type(_) => ty::AssociatedKind::Type
1519 let parent = ancestors.defs(tcx, trait_item.ident, kind, trait_def.def_id).nth(1)
1520 .map(|node_item| node_item.map(|parent| parent.defaultness));
1522 if let Some(parent) = parent {
1523 if tcx.impl_item_is_final(&parent) {
1524 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1530 fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1533 impl_trait_ref: ty::TraitRef<'tcx>,
1534 impl_item_refs: &[hir::ImplItemRef]) {
1535 let impl_span = tcx.sess.source_map().def_span(impl_span);
1537 // If the trait reference itself is erroneous (so the compilation is going
1538 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1539 // isn't populated for such impls.
1540 if impl_trait_ref.references_error() { return; }
1542 // Locate trait definition and items
1543 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1544 let mut overridden_associated_type = None;
1546 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1548 // Check existing impl methods to see if they are both present in trait
1549 // and compatible with trait signature
1550 for impl_item in impl_items() {
1551 let ty_impl_item = tcx.associated_item(
1552 tcx.hir().local_def_id_from_hir_id(impl_item.hir_id));
1553 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1554 .find(|ac| Namespace::from(&impl_item.node) == Namespace::from(ac.kind) &&
1555 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1557 // Not compatible, but needed for the error message
1558 tcx.associated_items(impl_trait_ref.def_id)
1559 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1562 // Check that impl definition matches trait definition
1563 if let Some(ty_trait_item) = ty_trait_item {
1564 match impl_item.node {
1565 hir::ImplItemKind::Const(..) => {
1566 // Find associated const definition.
1567 if ty_trait_item.kind == ty::AssociatedKind::Const {
1568 compare_const_impl(tcx,
1574 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1575 "item `{}` is an associated const, \
1576 which doesn't match its trait `{}`",
1579 err.span_label(impl_item.span, "does not match trait");
1580 // We can only get the spans from local trait definition
1581 // Same for E0324 and E0325
1582 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1583 err.span_label(trait_span, "item in trait");
1588 hir::ImplItemKind::Method(..) => {
1589 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1590 if ty_trait_item.kind == ty::AssociatedKind::Method {
1591 compare_impl_method(tcx,
1598 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1599 "item `{}` is an associated method, \
1600 which doesn't match its trait `{}`",
1603 err.span_label(impl_item.span, "does not match trait");
1604 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1605 err.span_label(trait_span, "item in trait");
1610 hir::ImplItemKind::Existential(..) |
1611 hir::ImplItemKind::Type(_) => {
1612 if ty_trait_item.kind == ty::AssociatedKind::Type {
1613 if ty_trait_item.defaultness.has_value() {
1614 overridden_associated_type = Some(impl_item);
1617 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1618 "item `{}` is an associated type, \
1619 which doesn't match its trait `{}`",
1622 err.span_label(impl_item.span, "does not match trait");
1623 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1624 err.span_label(trait_span, "item in trait");
1631 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1635 // Check for missing items from trait
1636 let mut missing_items = Vec::new();
1637 let mut invalidated_items = Vec::new();
1638 let associated_type_overridden = overridden_associated_type.is_some();
1639 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1640 let is_implemented = trait_def.ancestors(tcx, impl_id)
1641 .defs(tcx, trait_item.ident, trait_item.kind, impl_trait_ref.def_id)
1643 .map(|node_item| !node_item.node.is_from_trait())
1646 if !is_implemented && !tcx.impl_is_default(impl_id) {
1647 if !trait_item.defaultness.has_value() {
1648 missing_items.push(trait_item);
1649 } else if associated_type_overridden {
1650 invalidated_items.push(trait_item.ident);
1655 if !missing_items.is_empty() {
1656 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1657 "not all trait items implemented, missing: `{}`",
1658 missing_items.iter()
1659 .map(|trait_item| trait_item.ident.to_string())
1660 .collect::<Vec<_>>().join("`, `"));
1661 err.span_label(impl_span, format!("missing `{}` in implementation",
1662 missing_items.iter()
1663 .map(|trait_item| trait_item.ident.to_string())
1664 .collect::<Vec<_>>().join("`, `")));
1665 for trait_item in missing_items {
1666 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1667 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1669 err.note_trait_signature(trait_item.ident.to_string(),
1670 trait_item.signature(&tcx));
1676 if !invalidated_items.is_empty() {
1677 let invalidator = overridden_associated_type.unwrap();
1678 span_err!(tcx.sess, invalidator.span, E0399,
1679 "the following trait items need to be reimplemented \
1680 as `{}` was overridden: `{}`",
1682 invalidated_items.iter()
1683 .map(|name| name.to_string())
1684 .collect::<Vec<_>>().join("`, `"))
1688 /// Checks whether a type can be represented in memory. In particular, it
1689 /// identifies types that contain themselves without indirection through a
1690 /// pointer, which would mean their size is unbounded.
1691 fn check_representable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1695 let rty = tcx.type_of(item_def_id);
1697 // Check that it is possible to represent this type. This call identifies
1698 // (1) types that contain themselves and (2) types that contain a different
1699 // recursive type. It is only necessary to throw an error on those that
1700 // contain themselves. For case 2, there must be an inner type that will be
1701 // caught by case 1.
1702 match rty.is_representable(tcx, sp) {
1703 Representability::SelfRecursive(spans) => {
1704 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1706 err.span_label(span, "recursive without indirection");
1711 Representability::Representable | Representability::ContainsRecursive => (),
1716 pub fn check_simd<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1717 let t = tcx.type_of(def_id);
1718 if let ty::Adt(def, substs) = t.sty {
1719 if def.is_struct() {
1720 let fields = &def.non_enum_variant().fields;
1721 if fields.is_empty() {
1722 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1725 let e = fields[0].ty(tcx, substs);
1726 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1727 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1728 .span_label(sp, "SIMD elements must have the same type")
1733 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1734 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1736 span_err!(tcx.sess, sp, E0077,
1737 "SIMD vector element type should be machine type");
1745 fn check_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1746 let repr = tcx.adt_def(def_id).repr;
1748 for attr in tcx.get_attrs(def_id).iter() {
1749 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
1750 if let attr::ReprPacked(pack) = r {
1751 if pack != repr.pack {
1752 struct_span_err!(tcx.sess, sp, E0634,
1753 "type has conflicting packed representation hints").emit();
1759 struct_span_err!(tcx.sess, sp, E0587,
1760 "type has conflicting packed and align representation hints").emit();
1762 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1763 struct_span_err!(tcx.sess, sp, E0588,
1764 "packed type cannot transitively contain a `[repr(align)]` type").emit();
1769 fn check_packed_inner<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1771 stack: &mut Vec<DefId>) -> bool {
1772 let t = tcx.type_of(def_id);
1773 if stack.contains(&def_id) {
1774 debug!("check_packed_inner: {:?} is recursive", t);
1777 if let ty::Adt(def, substs) = t.sty {
1778 if def.is_struct() || def.is_union() {
1779 if tcx.adt_def(def.did).repr.align > 0 {
1782 // push struct def_id before checking fields
1784 for field in &def.non_enum_variant().fields {
1785 let f = field.ty(tcx, substs);
1786 if let ty::Adt(def, _) = f.sty {
1787 if check_packed_inner(tcx, def.did, stack) {
1792 // only need to pop if not early out
1799 fn check_transparent<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1800 let adt = tcx.adt_def(def_id);
1801 if !adt.repr.transparent() {
1805 // For each field, figure out if it's known to be a ZST and align(1)
1806 let field_infos = adt.non_enum_variant().fields.iter().map(|field| {
1807 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
1808 let param_env = tcx.param_env(field.did);
1809 let layout = tcx.layout_of(param_env.and(ty));
1810 // We are currently checking the type this field came from, so it must be local
1811 let span = tcx.hir().span_if_local(field.did).unwrap();
1812 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
1813 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
1817 let non_zst_fields = field_infos.clone().filter(|(_span, zst, _align1)| !*zst);
1818 let non_zst_count = non_zst_fields.clone().count();
1819 if non_zst_count != 1 {
1820 let field_spans: Vec<_> = non_zst_fields.map(|(span, _zst, _align1)| span).collect();
1821 struct_span_err!(tcx.sess, sp, E0690,
1822 "transparent struct needs exactly one non-zero-sized field, but has {}",
1824 .span_note(field_spans, "non-zero-sized field")
1827 for (span, zst, align1) in field_infos {
1829 span_err!(tcx.sess, span, E0691,
1830 "zero-sized field in transparent struct has alignment larger than 1");
1835 #[allow(trivial_numeric_casts)]
1836 pub fn check_enum<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1838 vs: &'tcx [hir::Variant],
1840 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1841 let def = tcx.adt_def(def_id);
1842 def.destructor(tcx); // force the destructor to be evaluated
1845 let attributes = tcx.get_attrs(def_id);
1846 if let Some(attr) = attr::find_by_name(&attributes, "repr") {
1848 tcx.sess, attr.span, E0084,
1849 "unsupported representation for zero-variant enum")
1850 .span_label(sp, "zero-variant enum")
1855 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1856 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1857 if !tcx.features().repr128 {
1858 emit_feature_err(&tcx.sess.parse_sess,
1861 GateIssue::Language,
1862 "repr with 128-bit type is unstable");
1867 if let Some(ref e) = v.node.disr_expr {
1868 tcx.typeck_tables_of(tcx.hir().local_def_id_from_hir_id(e.hir_id));
1872 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
1873 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
1874 // Check for duplicate discriminant values
1875 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
1876 let variant_did = def.variants[VariantIdx::new(i)].def_id;
1877 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
1878 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
1879 let i_span = match variant_i.node.disr_expr {
1880 Some(ref expr) => tcx.hir().span_by_hir_id(expr.hir_id),
1881 None => tcx.hir().span_by_hir_id(variant_i_hir_id)
1883 let span = match v.node.disr_expr {
1884 Some(ref expr) => tcx.hir().span_by_hir_id(expr.hir_id),
1887 struct_span_err!(tcx.sess, span, E0081,
1888 "discriminant value `{}` already exists", disr_vals[i])
1889 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1890 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
1893 disr_vals.push(discr);
1896 check_representable(tcx, sp, def_id);
1899 fn report_unexpected_variant_def<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1903 span_err!(tcx.sess, span, E0533,
1904 "expected unit struct/variant or constant, found {} `{}`",
1906 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
1909 impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
1910 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.tcx }
1912 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1913 -> Lrc<ty::GenericPredicates<'tcx>>
1916 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1917 let item_id = tcx.hir().ty_param_owner(hir_id);
1918 let item_def_id = tcx.hir().local_def_id_from_hir_id(item_id);
1919 let generics = tcx.generics_of(item_def_id);
1920 let index = generics.param_def_id_to_index[&def_id];
1921 Lrc::new(ty::GenericPredicates {
1923 predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
1925 ty::Predicate::Trait(ref data)
1926 if data.skip_binder().self_ty().is_param(index) => {
1927 // HACK(eddyb) should get the original `Span`.
1928 let span = tcx.def_span(def_id);
1929 Some((predicate, span))
1937 fn re_infer(&self, span: Span, def: Option<&ty::GenericParamDef>)
1938 -> Option<ty::Region<'tcx>> {
1940 Some(def) => infer::EarlyBoundRegion(span, def.name),
1941 None => infer::MiscVariable(span)
1943 Some(self.next_region_var(v))
1946 fn ty_infer(&self, span: Span) -> Ty<'tcx> {
1947 self.next_ty_var(TypeVariableOrigin::TypeInference(span))
1950 fn ty_infer_for_def(&self,
1951 ty_param_def: &ty::GenericParamDef,
1952 span: Span) -> Ty<'tcx> {
1953 if let UnpackedKind::Type(ty) = self.var_for_def(span, ty_param_def).unpack() {
1959 fn projected_ty_from_poly_trait_ref(&self,
1962 poly_trait_ref: ty::PolyTraitRef<'tcx>)
1965 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
1967 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
1971 self.tcx().mk_projection(item_def_id, trait_ref.substs)
1974 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
1975 if ty.has_escaping_bound_vars() {
1976 ty // FIXME: normalization and escaping regions
1978 self.normalize_associated_types_in(span, &ty)
1982 fn set_tainted_by_errors(&self) {
1983 self.infcx.set_tainted_by_errors()
1986 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
1987 self.write_ty(hir_id, ty)
1991 /// Controls whether the arguments are tupled. This is used for the call
1994 /// Tupling means that all call-side arguments are packed into a tuple and
1995 /// passed as a single parameter. For example, if tupling is enabled, this
1998 /// fn f(x: (isize, isize))
2000 /// Can be called as:
2007 #[derive(Clone, Eq, PartialEq)]
2008 enum TupleArgumentsFlag {
2013 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
2014 pub fn new(inh: &'a Inherited<'a, 'gcx, 'tcx>,
2015 param_env: ty::ParamEnv<'tcx>,
2016 body_id: hir::HirId)
2017 -> FnCtxt<'a, 'gcx, 'tcx> {
2021 err_count_on_creation: inh.tcx.sess.err_count(),
2023 ret_coercion_span: RefCell::new(None),
2025 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2026 hir::CRATE_HIR_ID)),
2027 diverges: Cell::new(Diverges::Maybe),
2028 has_errors: Cell::new(false),
2029 enclosing_breakables: RefCell::new(EnclosingBreakables {
2031 by_id: Default::default(),
2037 pub fn sess(&self) -> &Session {
2041 pub fn err_count_since_creation(&self) -> usize {
2042 self.tcx.sess.err_count() - self.err_count_on_creation
2045 /// Produces warning on the given node, if the current point in the
2046 /// function is unreachable, and there hasn't been another warning.
2047 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2048 if self.diverges.get() == Diverges::Always {
2049 self.diverges.set(Diverges::WarnedAlways);
2051 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2053 self.tcx().lint_hir(
2054 lint::builtin::UNREACHABLE_CODE,
2056 &format!("unreachable {}", kind));
2062 code: ObligationCauseCode<'tcx>)
2063 -> ObligationCause<'tcx> {
2064 ObligationCause::new(span, self.body_id, code)
2067 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2068 self.cause(span, ObligationCauseCode::MiscObligation)
2071 /// Resolves type variables in `ty` if possible. Unlike the infcx
2072 /// version (resolve_type_vars_if_possible), this version will
2073 /// also select obligations if it seems useful, in an effort
2074 /// to get more type information.
2075 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2076 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2078 // No Infer()? Nothing needs doing.
2079 if !ty.has_infer_types() {
2080 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2084 // If `ty` is a type variable, see whether we already know what it is.
2085 ty = self.resolve_type_vars_if_possible(&ty);
2086 if !ty.has_infer_types() {
2087 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2091 // If not, try resolving pending obligations as much as
2092 // possible. This can help substantially when there are
2093 // indirect dependencies that don't seem worth tracking
2095 self.select_obligations_where_possible(false);
2096 ty = self.resolve_type_vars_if_possible(&ty);
2098 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2102 fn record_deferred_call_resolution(&self,
2103 closure_def_id: DefId,
2104 r: DeferredCallResolution<'gcx, 'tcx>) {
2105 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2106 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2109 fn remove_deferred_call_resolutions(&self,
2110 closure_def_id: DefId)
2111 -> Vec<DeferredCallResolution<'gcx, 'tcx>>
2113 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2114 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2117 pub fn tag(&self) -> String {
2118 let self_ptr: *const FnCtxt<'_, '_, '_> = self;
2119 format!("{:?}", self_ptr)
2122 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2123 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2124 span_bug!(span, "no type for local variable {}",
2125 self.tcx.hir().hir_to_string(nid))
2130 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2131 debug!("write_ty({:?}, {:?}) in fcx {}",
2132 id, self.resolve_type_vars_if_possible(&ty), self.tag());
2133 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2135 if ty.references_error() {
2136 self.has_errors.set(true);
2137 self.set_tainted_by_errors();
2141 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2142 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2145 pub fn write_method_call(&self,
2147 method: MethodCallee<'tcx>) {
2148 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2151 .type_dependent_defs_mut()
2152 .insert(hir_id, Def::Method(method.def_id));
2154 self.write_substs(hir_id, method.substs);
2156 // When the method is confirmed, the `method.substs` includes
2157 // parameters from not just the method, but also the impl of
2158 // the method -- in particular, the `Self` type will be fully
2159 // resolved. However, those are not something that the "user
2160 // specified" -- i.e., those types come from the inferred type
2161 // of the receiver, not something the user wrote. So when we
2162 // create the user-substs, we want to replace those earlier
2163 // types with just the types that the user actually wrote --
2164 // that is, those that appear on the *method itself*.
2166 // As an example, if the user wrote something like
2167 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2168 // type of `foo` (possibly adjusted), but we don't want to
2169 // include that. We want just the `[_, u32]` part.
2170 if !method.substs.is_noop() {
2171 let method_generics = self.tcx.generics_of(method.def_id);
2172 if !method_generics.params.is_empty() {
2173 let user_type_annotation = self.infcx.probe(|_| {
2174 let user_substs = UserSubsts {
2175 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2176 let i = param.index as usize;
2177 if i < method_generics.parent_count {
2178 self.infcx.var_for_def(DUMMY_SP, param)
2183 user_self_ty: None, // not relevant here
2186 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2192 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2193 self.write_user_type_annotation(hir_id, user_type_annotation);
2198 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2199 if !substs.is_noop() {
2200 debug!("write_substs({:?}, {:?}) in fcx {}",
2205 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2209 /// Given the substs that we just converted from the HIR, try to
2210 /// canonicalize them and store them as user-given substitutions
2211 /// (i.e., substitutions that must be respected by the NLL check).
2213 /// This should be invoked **before any unifications have
2214 /// occurred**, so that annotations like `Vec<_>` are preserved
2216 pub fn write_user_type_annotation_from_substs(
2220 substs: SubstsRef<'tcx>,
2221 user_self_ty: Option<UserSelfTy<'tcx>>,
2224 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2225 user_self_ty={:?} in fcx {}",
2226 hir_id, def_id, substs, user_self_ty, self.tag(),
2229 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2230 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2231 &UserType::TypeOf(def_id, UserSubsts {
2236 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2237 self.write_user_type_annotation(hir_id, canonicalized);
2241 pub fn write_user_type_annotation(
2244 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2247 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2248 hir_id, canonical_user_type_annotation, self.tag(),
2251 if !canonical_user_type_annotation.is_identity() {
2252 self.tables.borrow_mut().user_provided_types_mut().insert(
2253 hir_id, canonical_user_type_annotation
2256 debug!("write_user_type_annotation: skipping identity substs");
2260 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2261 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2267 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2268 Entry::Vacant(entry) => { entry.insert(adj); },
2269 Entry::Occupied(mut entry) => {
2270 debug!(" - composing on top of {:?}", entry.get());
2271 match (&entry.get()[..], &adj[..]) {
2272 // Applying any adjustment on top of a NeverToAny
2273 // is a valid NeverToAny adjustment, because it can't
2275 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2277 Adjustment { kind: Adjust::Deref(_), .. },
2278 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2280 Adjustment { kind: Adjust::Deref(_), .. },
2281 .. // Any following adjustments are allowed.
2283 // A reborrow has no effect before a dereference.
2285 // FIXME: currently we never try to compose autoderefs
2286 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2288 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2289 expr, entry.get(), adj)
2291 *entry.get_mut() = adj;
2296 /// Basically whenever we are converting from a type scheme into
2297 /// the fn body space, we always want to normalize associated
2298 /// types as well. This function combines the two.
2299 fn instantiate_type_scheme<T>(&self,
2301 substs: SubstsRef<'tcx>,
2304 where T : TypeFoldable<'tcx>
2306 let value = value.subst(self.tcx, substs);
2307 let result = self.normalize_associated_types_in(span, &value);
2308 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2315 /// As `instantiate_type_scheme`, but for the bounds found in a
2316 /// generic type scheme.
2317 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: SubstsRef<'tcx>)
2318 -> ty::InstantiatedPredicates<'tcx> {
2319 let bounds = self.tcx.predicates_of(def_id);
2320 let result = bounds.instantiate(self.tcx, substs);
2321 let result = self.normalize_associated_types_in(span, &result);
2322 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
2329 /// Replaces the opaque types from the given value with type variables,
2330 /// and records the `OpaqueTypeMap` for later use during writeback. See
2331 /// `InferCtxt::instantiate_opaque_types` for more details.
2332 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2334 parent_id: hir::HirId,
2337 let parent_def_id = self.tcx.hir().local_def_id_from_hir_id(parent_id);
2338 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2342 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2343 self.instantiate_opaque_types(
2351 let mut opaque_types = self.opaque_types.borrow_mut();
2352 for (ty, decl) in opaque_type_map {
2353 let old_value = opaque_types.insert(ty, decl);
2354 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2360 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2361 where T : TypeFoldable<'tcx>
2363 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2366 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2368 where T : TypeFoldable<'tcx>
2370 self.inh.partially_normalize_associated_types_in(span,
2376 pub fn require_type_meets(&self,
2379 code: traits::ObligationCauseCode<'tcx>,
2382 self.register_bound(
2385 traits::ObligationCause::new(span, self.body_id, code));
2388 pub fn require_type_is_sized(&self,
2391 code: traits::ObligationCauseCode<'tcx>)
2393 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
2394 self.require_type_meets(ty, span, code, lang_item);
2397 pub fn require_type_is_sized_deferred(&self,
2400 code: traits::ObligationCauseCode<'tcx>)
2402 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2405 pub fn register_bound(&self,
2408 cause: traits::ObligationCause<'tcx>)
2410 self.fulfillment_cx.borrow_mut()
2411 .register_bound(self, self.param_env, ty, def_id, cause);
2414 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2415 let t = AstConv::ast_ty_to_ty(self, ast_t);
2416 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2420 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2421 let ty = self.to_ty(ast_ty);
2422 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2424 if Self::can_contain_user_lifetime_bounds(ty) {
2425 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2426 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2427 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2433 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2434 AstConv::ast_const_to_const(self, ast_c, ty)
2437 // If the type given by the user has free regions, save it for later, since
2438 // NLL would like to enforce those. Also pass in types that involve
2439 // projections, since those can resolve to `'static` bounds (modulo #54940,
2440 // which hopefully will be fixed by the time you see this comment, dear
2441 // reader, although I have my doubts). Also pass in types with inference
2442 // types, because they may be repeated. Other sorts of things are already
2443 // sufficiently enforced with erased regions. =)
2444 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2446 T: TypeFoldable<'tcx>
2448 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2451 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2452 match self.tables.borrow().node_types().get(id) {
2454 None if self.is_tainted_by_errors() => self.tcx.types.err,
2456 let node_id = self.tcx.hir().hir_to_node_id(id);
2457 bug!("no type for node {}: {} in fcx {}",
2458 node_id, self.tcx.hir().node_to_string(node_id),
2464 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2465 /// outlive the region `r`.
2466 pub fn register_wf_obligation(&self,
2469 code: traits::ObligationCauseCode<'tcx>)
2471 // WF obligations never themselves fail, so no real need to give a detailed cause:
2472 let cause = traits::ObligationCause::new(span, self.body_id, code);
2473 self.register_predicate(traits::Obligation::new(cause,
2475 ty::Predicate::WellFormed(ty)));
2478 /// Registers obligations that all types appearing in `substs` are well-formed.
2479 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2480 for ty in substs.types() {
2481 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2485 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2486 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2487 /// trait/region obligations.
2489 /// For example, if there is a function:
2492 /// fn foo<'a,T:'a>(...)
2495 /// and a reference:
2501 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2502 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2503 pub fn add_obligations_for_parameters(&self,
2504 cause: traits::ObligationCause<'tcx>,
2505 predicates: &ty::InstantiatedPredicates<'tcx>)
2507 assert!(!predicates.has_escaping_bound_vars());
2509 debug!("add_obligations_for_parameters(predicates={:?})",
2512 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2513 self.register_predicate(obligation);
2517 // FIXME(arielb1): use this instead of field.ty everywhere
2518 // Only for fields! Returns <none> for methods>
2519 // Indifferent to privacy flags
2520 pub fn field_ty(&self,
2522 field: &'tcx ty::FieldDef,
2523 substs: SubstsRef<'tcx>)
2526 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2529 fn check_casts(&self) {
2530 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2531 for cast in deferred_cast_checks.drain(..) {
2536 fn resolve_generator_interiors(&self, def_id: DefId) {
2537 let mut generators = self.deferred_generator_interiors.borrow_mut();
2538 for (body_id, interior) in generators.drain(..) {
2539 self.select_obligations_where_possible(false);
2540 generator_interior::resolve_interior(self, def_id, body_id, interior);
2544 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2545 // Non-numerics get replaced with ! or () (depending on whether
2546 // feature(never_type) is enabled, unconstrained ints with i32,
2547 // unconstrained floats with f64.
2548 // Fallback becomes very dubious if we have encountered type-checking errors.
2549 // In that case, fallback to Error.
2550 // The return value indicates whether fallback has occurred.
2551 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2552 use rustc::ty::error::UnconstrainedNumeric::Neither;
2553 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2555 assert!(ty.is_ty_infer());
2556 let fallback = match self.type_is_unconstrained_numeric(ty) {
2557 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2558 UnconstrainedInt => self.tcx.types.i32,
2559 UnconstrainedFloat => self.tcx.types.f64,
2560 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2561 Neither => return false,
2563 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2564 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2568 fn select_all_obligations_or_error(&self) {
2569 debug!("select_all_obligations_or_error");
2570 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2571 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2575 /// Select as many obligations as we can at present.
2576 fn select_obligations_where_possible(&self, fallback_has_occurred: bool) {
2577 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2578 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2582 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2583 /// returns a type of `&T`, but the actual type we assign to the
2584 /// *expression* is `T`. So this function just peels off the return
2585 /// type by one layer to yield `T`.
2586 fn make_overloaded_place_return_type(&self,
2587 method: MethodCallee<'tcx>)
2588 -> ty::TypeAndMut<'tcx>
2590 // extract method return type, which will be &T;
2591 let ret_ty = method.sig.output();
2593 // method returns &T, but the type as visible to user is T, so deref
2594 ret_ty.builtin_deref(true).unwrap()
2597 fn lookup_indexing(&self,
2599 base_expr: &'gcx hir::Expr,
2603 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2605 // FIXME(#18741) -- this is almost but not quite the same as the
2606 // autoderef that normal method probing does. They could likely be
2609 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2610 let mut result = None;
2611 while result.is_none() && autoderef.next().is_some() {
2612 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2614 autoderef.finalize(self);
2618 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2619 /// (and otherwise adjust) `base_expr`, looking for a type which either
2620 /// supports builtin indexing or overloaded indexing.
2621 /// This loop implements one step in that search; the autoderef loop
2622 /// is implemented by `lookup_indexing`.
2623 fn try_index_step(&self,
2625 base_expr: &hir::Expr,
2626 autoderef: &Autoderef<'a, 'gcx, 'tcx>,
2629 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2631 let adjusted_ty = autoderef.unambiguous_final_ty(self);
2632 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2639 for &unsize in &[false, true] {
2640 let mut self_ty = adjusted_ty;
2642 // We only unsize arrays here.
2643 if let ty::Array(element_ty, _) = adjusted_ty.sty {
2644 self_ty = self.tcx.mk_slice(element_ty);
2650 // If some lookup succeeds, write callee into table and extract index/element
2651 // type from the method signature.
2652 // If some lookup succeeded, install method in table
2653 let input_ty = self.next_ty_var(TypeVariableOrigin::AutoDeref(base_expr.span));
2654 let method = self.try_overloaded_place_op(
2655 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
2657 let result = method.map(|ok| {
2658 debug!("try_index_step: success, using overloaded indexing");
2659 let method = self.register_infer_ok_obligations(ok);
2661 let mut adjustments = autoderef.adjust_steps(self, needs);
2662 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].sty {
2663 let mutbl = match r_mutbl {
2664 hir::MutImmutable => AutoBorrowMutability::Immutable,
2665 hir::MutMutable => AutoBorrowMutability::Mutable {
2666 // Indexing can be desugared to a method call,
2667 // so maybe we could use two-phase here.
2668 // See the documentation of AllowTwoPhase for why that's
2669 // not the case today.
2670 allow_two_phase_borrow: AllowTwoPhase::No,
2673 adjustments.push(Adjustment {
2674 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
2675 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2682 adjustments.push(Adjustment {
2683 kind: Adjust::Pointer(PointerCast::Unsize),
2684 target: method.sig.inputs()[0]
2687 self.apply_adjustments(base_expr, adjustments);
2689 self.write_method_call(expr.hir_id, method);
2690 (input_ty, self.make_overloaded_place_return_type(method).ty)
2692 if result.is_some() {
2700 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
2701 let (tr, name) = match (op, is_mut) {
2702 (PlaceOp::Deref, false) =>
2703 (self.tcx.lang_items().deref_trait(), "deref"),
2704 (PlaceOp::Deref, true) =>
2705 (self.tcx.lang_items().deref_mut_trait(), "deref_mut"),
2706 (PlaceOp::Index, false) =>
2707 (self.tcx.lang_items().index_trait(), "index"),
2708 (PlaceOp::Index, true) =>
2709 (self.tcx.lang_items().index_mut_trait(), "index_mut"),
2711 (tr, ast::Ident::from_str(name))
2714 fn try_overloaded_place_op(&self,
2717 arg_tys: &[Ty<'tcx>],
2720 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
2722 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
2728 // Try Mut first, if needed.
2729 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
2730 let method = match (needs, mut_tr) {
2731 (Needs::MutPlace, Some(trait_did)) => {
2732 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
2737 // Otherwise, fall back to the immutable version.
2738 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
2739 let method = match (method, imm_tr) {
2740 (None, Some(trait_did)) => {
2741 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
2743 (method, _) => method,
2749 fn check_method_argument_types(&self,
2752 method: Result<MethodCallee<'tcx>, ()>,
2753 args_no_rcvr: &'gcx [hir::Expr],
2754 tuple_arguments: TupleArgumentsFlag,
2755 expected: Expectation<'tcx>)
2757 let has_error = match method {
2759 method.substs.references_error() || method.sig.references_error()
2764 let err_inputs = self.err_args(args_no_rcvr.len());
2766 let err_inputs = match tuple_arguments {
2767 DontTupleArguments => err_inputs,
2768 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
2771 self.check_argument_types(sp, expr_sp, &err_inputs[..], &[], args_no_rcvr,
2772 false, tuple_arguments, None);
2773 return self.tcx.types.err;
2776 let method = method.unwrap();
2777 // HACK(eddyb) ignore self in the definition (see above).
2778 let expected_arg_tys = self.expected_inputs_for_expected_output(
2781 method.sig.output(),
2782 &method.sig.inputs()[1..]
2784 self.check_argument_types(sp, expr_sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2785 args_no_rcvr, method.sig.c_variadic, tuple_arguments,
2786 self.tcx.hir().span_if_local(method.def_id));
2790 fn self_type_matches_expected_vid(
2792 trait_ref: ty::PolyTraitRef<'tcx>,
2793 expected_vid: ty::TyVid,
2795 let self_ty = self.shallow_resolve(trait_ref.self_ty());
2797 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
2798 trait_ref, self_ty, expected_vid
2801 ty::Infer(ty::TyVar(found_vid)) => {
2802 // FIXME: consider using `sub_root_var` here so we
2803 // can see through subtyping.
2804 let found_vid = self.root_var(found_vid);
2805 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
2806 expected_vid == found_vid
2812 fn obligations_for_self_ty<'b>(&'b self, self_ty: ty::TyVid)
2813 -> impl Iterator<Item=(ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
2814 + Captures<'gcx> + 'b
2816 // FIXME: consider using `sub_root_var` here so we
2817 // can see through subtyping.
2818 let ty_var_root = self.root_var(self_ty);
2819 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
2820 self_ty, ty_var_root,
2821 self.fulfillment_cx.borrow().pending_obligations());
2825 .pending_obligations()
2827 .filter_map(move |obligation| match obligation.predicate {
2828 ty::Predicate::Projection(ref data) =>
2829 Some((data.to_poly_trait_ref(self.tcx), obligation)),
2830 ty::Predicate::Trait(ref data) =>
2831 Some((data.to_poly_trait_ref(), obligation)),
2832 ty::Predicate::Subtype(..) => None,
2833 ty::Predicate::RegionOutlives(..) => None,
2834 ty::Predicate::TypeOutlives(..) => None,
2835 ty::Predicate::WellFormed(..) => None,
2836 ty::Predicate::ObjectSafe(..) => None,
2837 ty::Predicate::ConstEvaluatable(..) => None,
2838 // N.B., this predicate is created by breaking down a
2839 // `ClosureType: FnFoo()` predicate, where
2840 // `ClosureType` represents some `Closure`. It can't
2841 // possibly be referring to the current closure,
2842 // because we haven't produced the `Closure` for
2843 // this closure yet; this is exactly why the other
2844 // code is looking for a self type of a unresolved
2845 // inference variable.
2846 ty::Predicate::ClosureKind(..) => None,
2847 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
2850 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
2851 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
2852 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
2856 /// Generic function that factors out common logic from function calls,
2857 /// method calls and overloaded operators.
2858 fn check_argument_types(&self,
2861 fn_inputs: &[Ty<'tcx>],
2862 mut expected_arg_tys: &[Ty<'tcx>],
2863 args: &'gcx [hir::Expr],
2865 tuple_arguments: TupleArgumentsFlag,
2866 def_span: Option<Span>) {
2869 // Grab the argument types, supplying fresh type variables
2870 // if the wrong number of arguments were supplied
2871 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2877 // All the input types from the fn signature must outlive the call
2878 // so as to validate implied bounds.
2879 for &fn_input_ty in fn_inputs {
2880 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2883 let expected_arg_count = fn_inputs.len();
2885 let param_count_error = |expected_count: usize,
2890 let mut err = tcx.sess.struct_span_err_with_code(sp,
2891 &format!("this function takes {}{} but {} {} supplied",
2892 if c_variadic { "at least " } else { "" },
2893 potentially_plural_count(expected_count, "parameter"),
2894 potentially_plural_count(arg_count, "parameter"),
2895 if arg_count == 1 {"was"} else {"were"}),
2896 DiagnosticId::Error(error_code.to_owned()));
2898 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
2899 err.span_label(def_s, "defined here");
2902 let sugg_span = tcx.sess.source_map().end_point(expr_sp);
2903 // remove closing `)` from the span
2904 let sugg_span = sugg_span.shrink_to_lo();
2905 err.span_suggestion(
2907 "expected the unit value `()`; create it with empty parentheses",
2909 Applicability::MachineApplicable);
2911 err.span_label(sp, format!("expected {}{}",
2912 if c_variadic { "at least " } else { "" },
2913 potentially_plural_count(expected_count, "parameter")));
2918 let formal_tys = if tuple_arguments == TupleArguments {
2919 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2920 match tuple_type.sty {
2921 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
2922 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
2923 expected_arg_tys = &[];
2924 self.err_args(args.len())
2926 ty::Tuple(arg_types) => {
2927 expected_arg_tys = match expected_arg_tys.get(0) {
2928 Some(&ty) => match ty.sty {
2929 ty::Tuple(ref tys) => &tys,
2937 span_err!(tcx.sess, sp, E0059,
2938 "cannot use call notation; the first type parameter \
2939 for the function trait is neither a tuple nor unit");
2940 expected_arg_tys = &[];
2941 self.err_args(args.len())
2944 } else if expected_arg_count == supplied_arg_count {
2946 } else if c_variadic {
2947 if supplied_arg_count >= expected_arg_count {
2950 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
2951 expected_arg_tys = &[];
2952 self.err_args(supplied_arg_count)
2955 // is the missing argument of type `()`?
2956 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
2957 self.resolve_type_vars_if_possible(&expected_arg_tys[0]).is_unit()
2958 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
2959 self.resolve_type_vars_if_possible(&fn_inputs[0]).is_unit()
2963 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
2965 expected_arg_tys = &[];
2966 self.err_args(supplied_arg_count)
2968 // If there is no expectation, expect formal_tys.
2969 let expected_arg_tys = if !expected_arg_tys.is_empty() {
2975 debug!("check_argument_types: formal_tys={:?}",
2976 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
2978 // Check the arguments.
2979 // We do this in a pretty awful way: first we type-check any arguments
2980 // that are not closures, then we type-check the closures. This is so
2981 // that we have more information about the types of arguments when we
2982 // type-check the functions. This isn't really the right way to do this.
2983 for &check_closures in &[false, true] {
2984 debug!("check_closures={}", check_closures);
2986 // More awful hacks: before we check argument types, try to do
2987 // an "opportunistic" vtable resolution of any trait bounds on
2988 // the call. This helps coercions.
2990 self.select_obligations_where_possible(false);
2993 // For C-variadic functions, we don't have a declared type for all of
2994 // the arguments hence we only do our usual type checking with
2995 // the arguments who's types we do know.
2996 let t = if c_variadic {
2998 } else if tuple_arguments == TupleArguments {
3003 for (i, arg) in args.iter().take(t).enumerate() {
3004 // Warn only for the first loop (the "no closures" one).
3005 // Closure arguments themselves can't be diverging, but
3006 // a previous argument can, e.g., `foo(panic!(), || {})`.
3007 if !check_closures {
3008 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3011 let is_closure = match arg.node {
3012 ExprKind::Closure(..) => true,
3016 if is_closure != check_closures {
3020 debug!("checking the argument");
3021 let formal_ty = formal_tys[i];
3023 // The special-cased logic below has three functions:
3024 // 1. Provide as good of an expected type as possible.
3025 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3027 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3029 // 2. Coerce to the most detailed type that could be coerced
3030 // to, which is `expected_ty` if `rvalue_hint` returns an
3031 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3032 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3033 // We're processing function arguments so we definitely want to use
3034 // two-phase borrows.
3035 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3037 // 3. Relate the expected type and the formal one,
3038 // if the expected type was used for the coercion.
3039 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3043 // We also need to make sure we at least write the ty of the other
3044 // arguments which we skipped above.
3046 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3047 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3048 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3051 for arg in args.iter().skip(expected_arg_count) {
3052 let arg_ty = self.check_expr(&arg);
3054 // There are a few types which get autopromoted when passed via varargs
3055 // in C but we just error out instead and require explicit casts.
3056 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3058 ty::Float(ast::FloatTy::F32) => {
3059 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3061 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3062 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3064 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3065 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3068 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3069 let ptr_ty = self.resolve_type_vars_if_possible(&ptr_ty);
3070 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3078 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3079 vec![self.tcx.types.err; len]
3082 // AST fragment checking
3085 expected: Expectation<'tcx>)
3091 ast::LitKind::Str(..) => tcx.mk_static_str(),
3092 ast::LitKind::ByteStr(ref v) => {
3093 tcx.mk_imm_ref(tcx.types.re_static,
3094 tcx.mk_array(tcx.types.u8, v.len() as u64))
3096 ast::LitKind::Byte(_) => tcx.types.u8,
3097 ast::LitKind::Char(_) => tcx.types.char,
3098 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3099 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3100 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3101 let opt_ty = expected.to_option(self).and_then(|ty| {
3103 ty::Int(_) | ty::Uint(_) => Some(ty),
3104 ty::Char => Some(tcx.types.u8),
3105 ty::RawPtr(..) => Some(tcx.types.usize),
3106 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3110 opt_ty.unwrap_or_else(|| self.next_int_var())
3112 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3113 ast::LitKind::FloatUnsuffixed(_) => {
3114 let opt_ty = expected.to_option(self).and_then(|ty| {
3116 ty::Float(_) => Some(ty),
3120 opt_ty.unwrap_or_else(|| self.next_float_var())
3122 ast::LitKind::Bool(_) => tcx.types.bool,
3123 ast::LitKind::Err(_) => tcx.types.err,
3127 fn check_expr_eq_type(&self,
3128 expr: &'gcx hir::Expr,
3129 expected: Ty<'tcx>) {
3130 let ty = self.check_expr_with_hint(expr, expected);
3131 self.demand_eqtype(expr.span, expected, ty);
3134 pub fn check_expr_has_type_or_error(&self,
3135 expr: &'gcx hir::Expr,
3136 expected: Ty<'tcx>) -> Ty<'tcx> {
3137 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected))
3140 fn check_expr_meets_expectation_or_error(&self,
3141 expr: &'gcx hir::Expr,
3142 expected: Expectation<'tcx>) -> Ty<'tcx> {
3143 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
3144 let mut ty = self.check_expr_with_expectation(expr, expected);
3146 // While we don't allow *arbitrary* coercions here, we *do* allow
3147 // coercions from ! to `expected`.
3149 assert!(!self.tables.borrow().adjustments().contains_key(expr.hir_id),
3150 "expression with never type wound up being adjusted");
3151 let adj_ty = self.next_diverging_ty_var(
3152 TypeVariableOrigin::AdjustmentType(expr.span));
3153 self.apply_adjustments(expr, vec![Adjustment {
3154 kind: Adjust::NeverToAny,
3160 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
3161 if self.is_assign_to_bool(expr, expected_ty) {
3162 // Error reported in `check_assign` so avoid emitting error again.
3163 // FIXME(centril): Consider removing if/when `if` desugars to `match`.
3172 fn check_expr_coercable_to_type(&self,
3173 expr: &'gcx hir::Expr,
3174 expected: Ty<'tcx>) -> Ty<'tcx> {
3175 let ty = self.check_expr_with_hint(expr, expected);
3176 // checks don't need two phase
3177 self.demand_coerce(expr, ty, expected, AllowTwoPhase::No)
3180 fn check_expr_with_hint(&self,
3181 expr: &'gcx hir::Expr,
3182 expected: Ty<'tcx>) -> Ty<'tcx> {
3183 self.check_expr_with_expectation(expr, ExpectHasType(expected))
3186 fn check_expr_with_expectation(&self,
3187 expr: &'gcx hir::Expr,
3188 expected: Expectation<'tcx>) -> Ty<'tcx> {
3189 self.check_expr_with_expectation_and_needs(expr, expected, Needs::None)
3192 fn check_expr(&self, expr: &'gcx hir::Expr) -> Ty<'tcx> {
3193 self.check_expr_with_expectation(expr, NoExpectation)
3196 fn check_expr_with_needs(&self, expr: &'gcx hir::Expr, needs: Needs) -> Ty<'tcx> {
3197 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
3200 // Determine the `Self` type, using fresh variables for all variables
3201 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3202 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3204 pub fn impl_self_ty(&self,
3205 span: Span, // (potential) receiver for this impl
3207 -> TypeAndSubsts<'tcx> {
3208 let ity = self.tcx.type_of(did);
3209 debug!("impl_self_ty: ity={:?}", ity);
3211 let substs = self.fresh_substs_for_item(span, did);
3212 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3214 TypeAndSubsts { substs: substs, ty: substd_ty }
3217 /// Unifies the output type with the expected type early, for more coercions
3218 /// and forward type information on the input expressions.
3219 fn expected_inputs_for_expected_output(&self,
3221 expected_ret: Expectation<'tcx>,
3222 formal_ret: Ty<'tcx>,
3223 formal_args: &[Ty<'tcx>])
3225 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3226 let ret_ty = match expected_ret.only_has_type(self) {
3228 None => return Vec::new()
3230 let expect_args = self.fudge_inference_if_ok(|| {
3231 // Attempt to apply a subtyping relationship between the formal
3232 // return type (likely containing type variables if the function
3233 // is polymorphic) and the expected return type.
3234 // No argument expectations are produced if unification fails.
3235 let origin = self.misc(call_span);
3236 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3238 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3239 // to identity so the resulting type is not constrained.
3242 // Process any obligations locally as much as
3243 // we can. We don't care if some things turn
3244 // out unconstrained or ambiguous, as we're
3245 // just trying to get hints here.
3246 self.save_and_restore_in_snapshot_flag(|_| {
3247 let mut fulfill = TraitEngine::new(self.tcx);
3248 for obligation in ok.obligations {
3249 fulfill.register_predicate_obligation(self, obligation);
3251 fulfill.select_where_possible(self)
3252 }).map_err(|_| ())?;
3254 Err(_) => return Err(()),
3257 // Record all the argument types, with the substitutions
3258 // produced from the above subtyping unification.
3259 Ok(formal_args.iter().map(|ty| {
3260 self.resolve_type_vars_if_possible(ty)
3262 }).unwrap_or_default();
3263 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3264 formal_args, formal_ret,
3265 expect_args, expected_ret);
3269 // Checks a method call.
3270 fn check_method_call(&self,
3271 expr: &'gcx hir::Expr,
3272 segment: &hir::PathSegment,
3274 args: &'gcx [hir::Expr],
3275 expected: Expectation<'tcx>,
3276 needs: Needs) -> Ty<'tcx> {
3277 let rcvr = &args[0];
3278 let rcvr_t = self.check_expr_with_needs(&rcvr, needs);
3279 // no need to check for bot/err -- callee does that
3280 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
3282 let method = match self.lookup_method(rcvr_t,
3288 self.write_method_call(expr.hir_id, method);
3292 if segment.ident.name != keywords::Invalid.name() {
3293 self.report_method_error(span,
3296 SelfSource::MethodCall(rcvr),
3304 // Call the generic checker.
3305 self.check_method_argument_types(span,
3313 fn check_return_expr(&self, return_expr: &'gcx hir::Expr) {
3317 .unwrap_or_else(|| span_bug!(return_expr.span,
3318 "check_return_expr called outside fn body"));
3320 let ret_ty = ret_coercion.borrow().expected_ty();
3321 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty.clone());
3322 ret_coercion.borrow_mut()
3324 &self.cause(return_expr.span,
3325 ObligationCauseCode::ReturnType(return_expr.hir_id)),
3330 // A generic function for checking the 'then' and 'else' clauses in an 'if'
3331 // or 'if-else' expression.
3332 fn check_then_else(&self,
3333 cond_expr: &'gcx hir::Expr,
3334 then_expr: &'gcx hir::Expr,
3335 opt_else_expr: Option<&'gcx hir::Expr>,
3337 expected: Expectation<'tcx>) -> Ty<'tcx> {
3338 let cond_ty = self.check_expr_has_type_or_error(cond_expr, self.tcx.types.bool);
3339 let cond_diverges = self.diverges.get();
3340 self.diverges.set(Diverges::Maybe);
3342 let expected = expected.adjust_for_branches(self);
3343 let then_ty = self.check_expr_with_expectation(then_expr, expected);
3344 let then_diverges = self.diverges.get();
3345 self.diverges.set(Diverges::Maybe);
3347 // We've already taken the expected type's preferences
3348 // into account when typing the `then` branch. To figure
3349 // out the initial shot at a LUB, we thus only consider
3350 // `expected` if it represents a *hard* constraint
3351 // (`only_has_type`); otherwise, we just go with a
3352 // fresh type variable.
3353 let coerce_to_ty = expected.coercion_target_type(self, sp);
3354 let mut coerce: DynamicCoerceMany<'_, '_> = CoerceMany::new(coerce_to_ty);
3356 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
3358 if let Some(else_expr) = opt_else_expr {
3359 let else_ty = self.check_expr_with_expectation(else_expr, expected);
3360 let else_diverges = self.diverges.get();
3362 let mut outer_sp = if self.tcx.sess.source_map().is_multiline(sp) {
3363 // The `if`/`else` isn't in one line in the output, include some context to make it
3364 // clear it is an if/else expression:
3366 // LL | let x = if true {
3369 // || ----- expected because of this
3372 // || ^^^^^ expected i32, found u32
3374 // ||_____- if and else have incompatible types
3378 // The entire expression is in one line, only point at the arms
3380 // LL | let x = if true { 10i32 } else { 10u32 };
3381 // | ----- ^^^^^ expected i32, found u32
3383 // | expected because of this
3387 let mut remove_semicolon = None;
3388 let error_sp = if let ExprKind::Block(block, _) = &else_expr.node {
3389 if let Some(expr) = &block.expr {
3391 } else if let Some(stmt) = block.stmts.last() {
3392 // possibly incorrect trailing `;` in the else arm
3393 remove_semicolon = self.could_remove_semicolon(block, then_ty);
3395 } else { // empty block, point at its entirety
3396 // Avoid overlapping spans that aren't as readable:
3398 // 2 | let x = if true {
3401 // | | - expected because of this
3408 // | |______if and else have incompatible types
3409 // | expected integer, found ()
3411 // by not pointing at the entire expression:
3413 // 2 | let x = if true {
3414 // | ------- if and else have incompatible types
3416 // | - expected because of this
3421 // | |_____^ expected integer, found ()
3423 if outer_sp.is_some() {
3424 outer_sp = Some(self.tcx.sess.source_map().def_span(sp));
3428 } else { // shouldn't happen unless the parser has done something weird
3431 let then_sp = if let ExprKind::Block(block, _) = &then_expr.node {
3432 if let Some(expr) = &block.expr {
3434 } else if let Some(stmt) = block.stmts.last() {
3435 // possibly incorrect trailing `;` in the else arm
3436 remove_semicolon = remove_semicolon.or(
3437 self.could_remove_semicolon(block, else_ty));
3439 } else { // empty block, point at its entirety
3440 outer_sp = None; // same as in `error_sp`, cleanup output
3443 } else { // shouldn't happen unless the parser has done something weird
3447 let if_cause = self.cause(error_sp, ObligationCauseCode::IfExpression {
3450 semicolon: remove_semicolon,
3453 coerce.coerce(self, &if_cause, else_expr, else_ty);
3455 // We won't diverge unless both branches do (or the condition does).
3456 self.diverges.set(cond_diverges | then_diverges & else_diverges);
3458 // If this `if` expr is the parent's function return expr, the cause of the type
3459 // coercion is the return type, point at it. (#25228)
3460 let ret_reason = self.maybe_get_coercion_reason(then_expr.hir_id, sp);
3462 let else_cause = self.cause(sp, ObligationCauseCode::IfExpressionWithNoElse);
3463 coerce.coerce_forced_unit(self, &else_cause, &mut |err| {
3464 if let Some((sp, msg)) = &ret_reason {
3465 err.span_label(*sp, msg.as_str());
3466 } else if let ExprKind::Block(block, _) = &then_expr.node {
3467 if let Some(expr) = &block.expr {
3468 err.span_label(expr.span, "found here".to_string());
3471 err.note("`if` expressions without `else` evaluate to `()`");
3472 err.help("consider adding an `else` block that evaluates to the expected type");
3473 }, ret_reason.is_none());
3475 // If the condition is false we can't diverge.
3476 self.diverges.set(cond_diverges);
3479 let result_ty = coerce.complete(self);
3480 if cond_ty.references_error() {
3487 fn maybe_get_coercion_reason(&self, hir_id: hir::HirId, sp: Span) -> Option<(Span, String)> {
3488 let node = self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_node_by_hir_id(
3489 self.tcx.hir().get_parent_node_by_hir_id(hir_id),
3491 if let Node::Block(block) = node {
3492 // check that the body's parent is an fn
3493 let parent = self.tcx.hir().get_by_hir_id(
3494 self.tcx.hir().get_parent_node_by_hir_id(
3495 self.tcx.hir().get_parent_node_by_hir_id(block.hir_id),
3498 if let (Some(expr), Node::Item(hir::Item {
3499 node: hir::ItemKind::Fn(..), ..
3500 })) = (&block.expr, parent) {
3501 // check that the `if` expr without `else` is the fn body's expr
3502 if expr.span == sp {
3503 return self.get_fn_decl(hir_id).map(|(fn_decl, _)| (
3504 fn_decl.output.span(),
3505 format!("expected `{}` because of this return type", fn_decl.output),
3510 if let Node::Local(hir::Local {
3511 ty: Some(_), pat, ..
3513 return Some((pat.span, "expected because of this assignment".to_string()));
3518 // Check field access expressions
3519 fn check_field(&self,
3520 expr: &'gcx hir::Expr,
3522 base: &'gcx hir::Expr,
3523 field: ast::Ident) -> Ty<'tcx> {
3524 let expr_t = self.check_expr_with_needs(base, needs);
3525 let expr_t = self.structurally_resolved_type(base.span,
3527 let mut private_candidate = None;
3528 let mut autoderef = self.autoderef(expr.span, expr_t);
3529 while let Some((base_t, _)) = autoderef.next() {
3531 ty::Adt(base_def, substs) if !base_def.is_enum() => {
3532 debug!("struct named {:?}", base_t);
3533 let (ident, def_scope) =
3534 self.tcx.adjust_ident(field, base_def.did, self.body_id);
3535 let fields = &base_def.non_enum_variant().fields;
3536 if let Some(index) = fields.iter().position(|f| f.ident.modern() == ident) {
3537 let field = &fields[index];
3538 let field_ty = self.field_ty(expr.span, field, substs);
3539 // Save the index of all fields regardless of their visibility in case
3540 // of error recovery.
3541 self.write_field_index(expr.hir_id, index);
3542 if field.vis.is_accessible_from(def_scope, self.tcx) {
3543 let adjustments = autoderef.adjust_steps(self, needs);
3544 self.apply_adjustments(base, adjustments);
3545 autoderef.finalize(self);
3547 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span);
3550 private_candidate = Some((base_def.did, field_ty));
3553 ty::Tuple(ref tys) => {
3554 let fstr = field.as_str();
3555 if let Ok(index) = fstr.parse::<usize>() {
3556 if fstr == index.to_string() {
3557 if let Some(field_ty) = tys.get(index) {
3558 let adjustments = autoderef.adjust_steps(self, needs);
3559 self.apply_adjustments(base, adjustments);
3560 autoderef.finalize(self);
3562 self.write_field_index(expr.hir_id, index);
3571 autoderef.unambiguous_final_ty(self);
3573 if let Some((did, field_ty)) = private_candidate {
3574 let struct_path = self.tcx().def_path_str(did);
3575 let mut err = struct_span_err!(self.tcx().sess, expr.span, E0616,
3576 "field `{}` of struct `{}` is private",
3577 field, struct_path);
3578 // Also check if an accessible method exists, which is often what is meant.
3579 if self.method_exists(field, expr_t, expr.hir_id, false)
3580 && !self.expr_in_place(expr.hir_id)
3582 self.suggest_method_call(
3584 &format!("a method `{}` also exists, call it with parentheses", field),
3592 } else if field.name == keywords::Invalid.name() {
3593 self.tcx().types.err
3594 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
3595 let mut err = type_error_struct!(self.tcx().sess, field.span, expr_t, E0615,
3596 "attempted to take value of method `{}` on type `{}`",
3599 if !self.expr_in_place(expr.hir_id) {
3600 self.suggest_method_call(
3602 "use parentheses to call the method",
3608 err.help("methods are immutable and cannot be assigned to");
3612 self.tcx().types.err
3614 if !expr_t.is_primitive_ty() {
3615 let mut err = self.no_such_field_err(field.span, field, expr_t);
3618 ty::Adt(def, _) if !def.is_enum() => {
3619 if let Some(suggested_field_name) =
3620 Self::suggest_field_name(def.non_enum_variant(),
3621 &field.as_str(), vec![]) {
3622 err.span_suggestion(
3624 "a field with a similar name exists",
3625 suggested_field_name.to_string(),
3626 Applicability::MaybeIncorrect,
3629 err.span_label(field.span, "unknown field");
3630 let struct_variant_def = def.non_enum_variant();
3631 let field_names = self.available_field_names(struct_variant_def);
3632 if !field_names.is_empty() {
3633 err.note(&format!("available fields are: {}",
3634 self.name_series_display(field_names)));
3638 ty::Array(_, len) => {
3639 if let (Some(len), Ok(user_index)) = (
3640 len.assert_usize(self.tcx),
3641 field.as_str().parse::<u64>()
3643 let base = self.tcx.sess.source_map()
3644 .span_to_snippet(base.span)
3646 self.tcx.hir().hir_to_pretty_string(base.hir_id));
3647 let help = "instead of using tuple indexing, use array indexing";
3648 let suggestion = format!("{}[{}]", base, field);
3649 let applicability = if len < user_index {
3650 Applicability::MachineApplicable
3652 Applicability::MaybeIncorrect
3654 err.span_suggestion(
3655 expr.span, help, suggestion, applicability
3660 let base = self.tcx.sess.source_map()
3661 .span_to_snippet(base.span)
3662 .unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
3663 let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
3664 let suggestion = format!("(*{}).{}", base, field);
3665 err.span_suggestion(
3669 Applicability::MaybeIncorrect,
3676 type_error_struct!(self.tcx().sess, field.span, expr_t, E0610,
3677 "`{}` is a primitive type and therefore doesn't have fields",
3680 self.tcx().types.err
3684 // Return an hint about the closest match in field names
3685 fn suggest_field_name(variant: &'tcx ty::VariantDef,
3687 skip: Vec<LocalInternedString>)
3689 let names = variant.fields.iter().filter_map(|field| {
3690 // ignore already set fields and private fields from non-local crates
3691 if skip.iter().any(|x| *x == field.ident.as_str()) ||
3692 (!variant.def_id.is_local() && field.vis != Visibility::Public)
3696 Some(&field.ident.name)
3700 find_best_match_for_name(names, field, None)
3703 fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<ast::Name> {
3704 variant.fields.iter().filter(|field| {
3705 let def_scope = self.tcx.adjust_ident(field.ident, variant.def_id, self.body_id).1;
3706 field.vis.is_accessible_from(def_scope, self.tcx)
3708 .map(|field| field.ident.name)
3712 fn name_series_display(&self, names: Vec<ast::Name>) -> String {
3713 // dynamic limit, to never omit just one field
3714 let limit = if names.len() == 6 { 6 } else { 5 };
3715 let mut display = names.iter().take(limit)
3716 .map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
3717 if names.len() > limit {
3718 display = format!("{} ... and {} others", display, names.len() - limit);
3723 fn no_such_field_err<T: Display>(&self, span: Span, field: T, expr_t: &ty::TyS<'_>)
3724 -> DiagnosticBuilder<'_> {
3725 type_error_struct!(self.tcx().sess, span, expr_t, E0609,
3726 "no field `{}` on type `{}`",
3730 fn report_unknown_field(
3733 variant: &'tcx ty::VariantDef,
3735 skip_fields: &[hir::Field],
3738 if variant.recovered {
3741 let mut err = self.type_error_struct_with_diag(
3743 |actual| match ty.sty {
3744 ty::Adt(adt, ..) if adt.is_enum() => {
3745 struct_span_err!(self.tcx.sess, field.ident.span, E0559,
3746 "{} `{}::{}` has no field named `{}`",
3747 kind_name, actual, variant.ident, field.ident)
3750 struct_span_err!(self.tcx.sess, field.ident.span, E0560,
3751 "{} `{}` has no field named `{}`",
3752 kind_name, actual, field.ident)
3756 // prevent all specified fields from being suggested
3757 let skip_fields = skip_fields.iter().map(|ref x| x.ident.as_str());
3758 if let Some(field_name) = Self::suggest_field_name(variant,
3759 &field.ident.as_str(),
3760 skip_fields.collect()) {
3761 err.span_suggestion(
3763 "a field with a similar name exists",
3764 field_name.to_string(),
3765 Applicability::MaybeIncorrect,
3769 ty::Adt(adt, ..) => {
3771 err.span_label(field.ident.span,
3772 format!("`{}::{}` does not have this field",
3773 ty, variant.ident));
3775 err.span_label(field.ident.span,
3776 format!("`{}` does not have this field", ty));
3778 let available_field_names = self.available_field_names(variant);
3779 if !available_field_names.is_empty() {
3780 err.note(&format!("available fields are: {}",
3781 self.name_series_display(available_field_names)));
3784 _ => bug!("non-ADT passed to report_unknown_field")
3790 fn check_expr_struct_fields(&self,
3792 expected: Expectation<'tcx>,
3793 expr_id: hir::HirId,
3795 variant: &'tcx ty::VariantDef,
3796 ast_fields: &'gcx [hir::Field],
3797 check_completeness: bool) -> bool {
3801 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3802 .get(0).cloned().unwrap_or(adt_ty);
3803 // re-link the regions that EIfEO can erase.
3804 self.demand_eqtype(span, adt_ty_hint, adt_ty);
3806 let (substs, adt_kind, kind_name) = match &adt_ty.sty {
3807 &ty::Adt(adt, substs) => {
3808 (substs, adt.adt_kind(), adt.variant_descr())
3810 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3813 let mut remaining_fields = variant.fields.iter().enumerate().map(|(i, field)|
3814 (field.ident.modern(), (i, field))
3815 ).collect::<FxHashMap<_, _>>();
3817 let mut seen_fields = FxHashMap::default();
3819 let mut error_happened = false;
3821 // Type-check each field.
3822 for field in ast_fields {
3823 let ident = tcx.adjust_ident(field.ident, variant.def_id, self.body_id).0;
3824 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
3825 seen_fields.insert(ident, field.span);
3826 self.write_field_index(field.hir_id, i);
3828 // We don't look at stability attributes on
3829 // struct-like enums (yet...), but it's definitely not
3830 // a bug to have constructed one.
3831 if adt_kind != AdtKind::Enum {
3832 tcx.check_stability(v_field.did, Some(expr_id), field.span);
3835 self.field_ty(field.span, v_field, substs)
3837 error_happened = true;
3838 if let Some(prev_span) = seen_fields.get(&ident) {
3839 let mut err = struct_span_err!(self.tcx.sess,
3842 "field `{}` specified more than once",
3845 err.span_label(field.ident.span, "used more than once");
3846 err.span_label(*prev_span, format!("first use of `{}`", ident));
3850 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3856 // Make sure to give a type to the field even if there's
3857 // an error, so we can continue type-checking.
3858 self.check_expr_coercable_to_type(&field.expr, field_type);
3861 // Make sure the programmer specified correct number of fields.
3862 if kind_name == "union" {
3863 if ast_fields.len() != 1 {
3864 tcx.sess.span_err(span, "union expressions should have exactly one field");
3866 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3867 let len = remaining_fields.len();
3869 let mut displayable_field_names = remaining_fields
3871 .map(|ident| ident.as_str())
3872 .collect::<Vec<_>>();
3874 displayable_field_names.sort();
3876 let truncated_fields_error = if len <= 3 {
3879 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3882 let remaining_fields_names = displayable_field_names.iter().take(3)
3883 .map(|n| format!("`{}`", n))
3884 .collect::<Vec<_>>()
3887 struct_span_err!(tcx.sess, span, E0063,
3888 "missing field{} {}{} in initializer of `{}`",
3889 if remaining_fields.len() == 1 { "" } else { "s" },
3890 remaining_fields_names,
3891 truncated_fields_error,
3893 .span_label(span, format!("missing {}{}",
3894 remaining_fields_names,
3895 truncated_fields_error))
3901 fn check_struct_fields_on_error(&self,
3902 fields: &'gcx [hir::Field],
3903 base_expr: &'gcx Option<P<hir::Expr>>) {
3904 for field in fields {
3905 self.check_expr(&field.expr);
3907 if let Some(ref base) = *base_expr {
3908 self.check_expr(&base);
3912 pub fn check_struct_path(&self,
3915 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3916 let path_span = match *qpath {
3917 QPath::Resolved(_, ref path) => path.span,
3918 QPath::TypeRelative(ref qself, _) => qself.span
3920 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3921 let variant = match def {
3923 self.set_tainted_by_errors();
3926 Def::Variant(..) => {
3928 ty::Adt(adt, substs) => {
3929 Some((adt.variant_of_def(def), adt.did, substs))
3931 _ => bug!("unexpected type: {:?}", ty)
3934 Def::Struct(..) | Def::Union(..) | Def::TyAlias(..) |
3935 Def::AssociatedTy(..) | Def::SelfTy(..) => {
3937 ty::Adt(adt, substs) if !adt.is_enum() => {
3938 Some((adt.non_enum_variant(), adt.did, substs))
3943 _ => bug!("unexpected definition: {:?}", def)
3946 if let Some((variant, did, substs)) = variant {
3947 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3948 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3950 // Check bounds on type arguments used in the path.
3951 let bounds = self.instantiate_bounds(path_span, did, substs);
3952 let cause = traits::ObligationCause::new(path_span, self.body_id,
3953 traits::ItemObligation(did));
3954 self.add_obligations_for_parameters(cause, &bounds);
3958 struct_span_err!(self.tcx.sess, path_span, E0071,
3959 "expected struct, variant or union type, found {}",
3960 ty.sort_string(self.tcx))
3961 .span_label(path_span, "not a struct")
3967 fn check_expr_struct(&self,
3969 expected: Expectation<'tcx>,
3971 fields: &'gcx [hir::Field],
3972 base_expr: &'gcx Option<P<hir::Expr>>) -> Ty<'tcx>
3974 // Find the relevant variant
3975 let (variant, adt_ty) =
3976 if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id) {
3979 self.check_struct_fields_on_error(fields, base_expr);
3980 return self.tcx.types.err;
3983 let path_span = match *qpath {
3984 QPath::Resolved(_, ref path) => path.span,
3985 QPath::TypeRelative(ref qself, _) => qself.span
3988 // Prohibit struct expressions when non-exhaustive flag is set.
3989 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
3990 if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
3991 span_err!(self.tcx.sess, expr.span, E0639,
3992 "cannot create non-exhaustive {} using struct expression",
3993 adt.variant_descr());
3996 let error_happened = self.check_expr_struct_fields(adt_ty, expected, expr.hir_id, path_span,
3997 variant, fields, base_expr.is_none());
3998 if let &Some(ref base_expr) = base_expr {
3999 // If check_expr_struct_fields hit an error, do not attempt to populate
4000 // the fields with the base_expr. This could cause us to hit errors later
4001 // when certain fields are assumed to exist that in fact do not.
4002 if !error_happened {
4003 self.check_expr_has_type_or_error(base_expr, adt_ty);
4005 ty::Adt(adt, substs) if adt.is_struct() => {
4006 let fru_field_types = adt.non_enum_variant().fields.iter().map(|f| {
4007 self.normalize_associated_types_in(expr.span, &f.ty(self.tcx, substs))
4012 .fru_field_types_mut()
4013 .insert(expr.hir_id, fru_field_types);
4016 span_err!(self.tcx.sess, base_expr.span, E0436,
4017 "functional record update syntax requires a struct");
4022 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
4028 /// If an expression has any sub-expressions that result in a type error,
4029 /// inspecting that expression's type with `ty.references_error()` will return
4030 /// true. Likewise, if an expression is known to diverge, inspecting its
4031 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
4032 /// strict, _|_ can appear in the type of an expression that does not,
4033 /// itself, diverge: for example, fn() -> _|_.)
4034 /// Note that inspecting a type's structure *directly* may expose the fact
4035 /// that there are actually multiple representations for `Error`, so avoid
4036 /// that when err needs to be handled differently.
4037 fn check_expr_with_expectation_and_needs(&self,
4038 expr: &'gcx hir::Expr,
4039 expected: Expectation<'tcx>,
4040 needs: Needs) -> Ty<'tcx> {
4041 debug!(">> type-checking: expr={:?} expected={:?}",
4044 // Warn for expressions after diverging siblings.
4045 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
4047 // Hide the outer diverging and has_errors flags.
4048 let old_diverges = self.diverges.get();
4049 let old_has_errors = self.has_errors.get();
4050 self.diverges.set(Diverges::Maybe);
4051 self.has_errors.set(false);
4053 let ty = self.check_expr_kind(expr, expected, needs);
4055 // Warn for non-block expressions with diverging children.
4057 ExprKind::Block(..) |
4058 ExprKind::Loop(..) | ExprKind::While(..) |
4059 ExprKind::If(..) | ExprKind::Match(..) => {}
4061 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression")
4064 // Any expression that produces a value of type `!` must have diverged
4066 self.diverges.set(self.diverges.get() | Diverges::Always);
4069 // Record the type, which applies it effects.
4070 // We need to do this after the warning above, so that
4071 // we don't warn for the diverging expression itself.
4072 self.write_ty(expr.hir_id, ty);
4074 // Combine the diverging and has_error flags.
4075 self.diverges.set(self.diverges.get() | old_diverges);
4076 self.has_errors.set(self.has_errors.get() | old_has_errors);
4078 debug!("type of {} is...", self.tcx.hir().hir_to_string(expr.hir_id));
4079 debug!("... {:?}, expected is {:?}", ty, expected);
4086 expr: &'gcx hir::Expr,
4087 expected: Expectation<'tcx>,
4091 "check_expr_kind(expr={:?}, expected={:?}, needs={:?})",
4098 let id = expr.hir_id;
4100 ExprKind::Box(ref subexpr) => {
4101 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
4103 ty::Adt(def, _) if def.is_box()
4104 => Expectation::rvalue_hint(self, ty.boxed_ty()),
4108 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
4109 tcx.mk_box(referent_ty)
4112 ExprKind::Lit(ref lit) => {
4113 self.check_lit(&lit, expected)
4115 ExprKind::Binary(op, ref lhs, ref rhs) => {
4116 self.check_binop(expr, op, lhs, rhs)
4118 ExprKind::AssignOp(op, ref lhs, ref rhs) => {
4119 self.check_binop_assign(expr, op, lhs, rhs)
4121 ExprKind::Unary(unop, ref oprnd) => {
4122 let expected_inner = match unop {
4123 hir::UnNot | hir::UnNeg => {
4130 let needs = match unop {
4131 hir::UnDeref => needs,
4134 let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd,
4138 if !oprnd_t.references_error() {
4139 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
4142 if let Some(mt) = oprnd_t.builtin_deref(true) {
4144 } else if let Some(ok) = self.try_overloaded_deref(
4145 expr.span, oprnd_t, needs) {
4146 let method = self.register_infer_ok_obligations(ok);
4147 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].sty {
4148 let mutbl = match mutbl {
4149 hir::MutImmutable => AutoBorrowMutability::Immutable,
4150 hir::MutMutable => AutoBorrowMutability::Mutable {
4151 // (It shouldn't actually matter for unary ops whether
4152 // we enable two-phase borrows or not, since a unary
4153 // op has no additional operands.)
4154 allow_two_phase_borrow: AllowTwoPhase::No,
4157 self.apply_adjustments(oprnd, vec![Adjustment {
4158 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
4159 target: method.sig.inputs()[0]
4162 oprnd_t = self.make_overloaded_place_return_type(method).ty;
4163 self.write_method_call(expr.hir_id, method);
4165 type_error_struct!(tcx.sess, expr.span, oprnd_t, E0614,
4166 "type `{}` cannot be dereferenced",
4168 oprnd_t = tcx.types.err;
4172 let result = self.check_user_unop(expr, oprnd_t, unop);
4173 // If it's builtin, we can reuse the type, this helps inference.
4174 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::Bool) {
4179 let result = self.check_user_unop(expr, oprnd_t, unop);
4180 // If it's builtin, we can reuse the type, this helps inference.
4181 if !(oprnd_t.is_integral() || oprnd_t.is_fp()) {
4189 ExprKind::AddrOf(mutbl, ref oprnd) => {
4190 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
4192 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
4193 if oprnd.is_place_expr() {
4194 // Places may legitimately have unsized types.
4195 // For example, dereferences of a fat pointer and
4196 // the last field of a struct can be unsized.
4199 Expectation::rvalue_hint(self, ty)
4205 let needs = Needs::maybe_mut_place(mutbl);
4206 let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs);
4208 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
4209 if tm.ty.references_error() {
4212 // Note: at this point, we cannot say what the best lifetime
4213 // is to use for resulting pointer. We want to use the
4214 // shortest lifetime possible so as to avoid spurious borrowck
4215 // errors. Moreover, the longest lifetime will depend on the
4216 // precise details of the value whose address is being taken
4217 // (and how long it is valid), which we don't know yet until type
4218 // inference is complete.
4220 // Therefore, here we simply generate a region variable. The
4221 // region inferencer will then select the ultimate value.
4222 // Finally, borrowck is charged with guaranteeing that the
4223 // value whose address was taken can actually be made to live
4224 // as long as it needs to live.
4225 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
4226 tcx.mk_ref(region, tm)
4229 ExprKind::Path(ref qpath) => {
4230 let (def, opt_ty, segs) = self.resolve_ty_and_def_ufcs(qpath, expr.hir_id,
4232 let ty = match def {
4234 self.set_tainted_by_errors();
4237 Def::Ctor(_, _, CtorKind::Fictive) => {
4238 report_unexpected_variant_def(tcx, &def, expr.span, qpath);
4241 _ => self.instantiate_value_path(segs, opt_ty, def, expr.span, id).0,
4244 if let ty::FnDef(..) = ty.sty {
4245 let fn_sig = ty.fn_sig(tcx);
4246 if !tcx.features().unsized_locals {
4247 // We want to remove some Sized bounds from std functions,
4248 // but don't want to expose the removal to stable Rust.
4249 // i.e., we don't want to allow
4255 // to work in stable even if the Sized bound on `drop` is relaxed.
4256 for i in 0..fn_sig.inputs().skip_binder().len() {
4257 // We just want to check sizedness, so instead of introducing
4258 // placeholder lifetimes with probing, we just replace higher lifetimes
4260 let input = self.replace_bound_vars_with_fresh_vars(
4262 infer::LateBoundRegionConversionTime::FnCall,
4263 &fn_sig.input(i)).0;
4264 self.require_type_is_sized_deferred(input, expr.span,
4265 traits::SizedArgumentType);
4268 // Here we want to prevent struct constructors from returning unsized types.
4269 // There were two cases this happened: fn pointer coercion in stable
4270 // and usual function call in presense of unsized_locals.
4271 // Also, as we just want to check sizedness, instead of introducing
4272 // placeholder lifetimes with probing, we just replace higher lifetimes
4274 let output = self.replace_bound_vars_with_fresh_vars(
4276 infer::LateBoundRegionConversionTime::FnCall,
4277 &fn_sig.output()).0;
4278 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
4281 // We always require that the type provided as the value for
4282 // a type parameter outlives the moment of instantiation.
4283 let substs = self.tables.borrow().node_substs(expr.hir_id);
4284 self.add_wf_bounds(substs, expr);
4288 ExprKind::InlineAsm(_, ref outputs, ref inputs) => {
4289 for expr in outputs.iter().chain(inputs.iter()) {
4290 self.check_expr(expr);
4294 ExprKind::Break(destination, ref expr_opt) => {
4295 if let Ok(target_id) = destination.target_id {
4297 if let Some(ref e) = *expr_opt {
4298 // If this is a break with a value, we need to type-check
4299 // the expression. Get an expected type from the loop context.
4300 let opt_coerce_to = {
4301 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4302 enclosing_breakables.find_breakable(target_id)
4305 .map(|coerce| coerce.expected_ty())
4308 // If the loop context is not a `loop { }`, then break with
4309 // a value is illegal, and `opt_coerce_to` will be `None`.
4310 // Just set expectation to error in that case.
4311 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
4313 // Recurse without `enclosing_breakables` borrowed.
4314 e_ty = self.check_expr_with_hint(e, coerce_to);
4315 cause = self.misc(e.span);
4317 // Otherwise, this is a break *without* a value. That's
4318 // always legal, and is equivalent to `break ()`.
4319 e_ty = tcx.mk_unit();
4320 cause = self.misc(expr.span);
4323 // Now that we have type-checked `expr_opt`, borrow
4324 // the `enclosing_loops` field and let's coerce the
4325 // type of `expr_opt` into what is expected.
4326 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4327 let ctxt = enclosing_breakables.find_breakable(target_id);
4328 if let Some(ref mut coerce) = ctxt.coerce {
4329 if let Some(ref e) = *expr_opt {
4330 coerce.coerce(self, &cause, e, e_ty);
4332 assert!(e_ty.is_unit());
4333 coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
4336 // If `ctxt.coerce` is `None`, we can just ignore
4337 // the type of the expresison. This is because
4338 // either this was a break *without* a value, in
4339 // which case it is always a legal type (`()`), or
4340 // else an error would have been flagged by the
4341 // `loops` pass for using break with an expression
4342 // where you are not supposed to.
4343 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
4346 ctxt.may_break = true;
4348 // the type of a `break` is always `!`, since it diverges
4351 // Otherwise, we failed to find the enclosing loop;
4352 // this can only happen if the `break` was not
4353 // inside a loop at all, which is caught by the
4354 // loop-checking pass.
4355 if self.tcx.sess.err_count() == 0 {
4356 self.tcx.sess.delay_span_bug(expr.span,
4357 "break was outside loop, but no error was emitted");
4360 // We still need to assign a type to the inner expression to
4361 // prevent the ICE in #43162.
4362 if let Some(ref e) = *expr_opt {
4363 self.check_expr_with_hint(e, tcx.types.err);
4365 // ... except when we try to 'break rust;'.
4366 // ICE this expression in particular (see #43162).
4367 if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.node {
4368 if path.segments.len() == 1 && path.segments[0].ident.name == "rust" {
4369 fatally_break_rust(self.tcx.sess);
4373 // There was an error; make type-check fail.
4378 ExprKind::Continue(destination) => {
4379 if destination.target_id.is_ok() {
4382 // There was an error; make type-check fail.
4386 ExprKind::Ret(ref expr_opt) => {
4387 if self.ret_coercion.is_none() {
4388 struct_span_err!(self.tcx.sess, expr.span, E0572,
4389 "return statement outside of function body").emit();
4390 } else if let Some(ref e) = *expr_opt {
4391 if self.ret_coercion_span.borrow().is_none() {
4392 *self.ret_coercion_span.borrow_mut() = Some(e.span);
4394 self.check_return_expr(e);
4396 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
4397 if self.ret_coercion_span.borrow().is_none() {
4398 *self.ret_coercion_span.borrow_mut() = Some(expr.span);
4400 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
4401 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
4402 coercion.coerce_forced_unit(
4407 fn_decl.output.span(),
4409 "expected `{}` because of this return type",
4417 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
4422 ExprKind::Assign(ref lhs, ref rhs) => {
4423 self.check_assign(expr, expected, lhs, rhs)
4425 ExprKind::If(ref cond, ref then_expr, ref opt_else_expr) => {
4426 self.check_then_else(&cond, then_expr, opt_else_expr.as_ref().map(|e| &**e),
4427 expr.span, expected)
4429 ExprKind::While(ref cond, ref body, _) => {
4430 let ctxt = BreakableCtxt {
4431 // cannot use break with a value from a while loop
4433 may_break: false, // Will get updated if/when we find a `break`.
4436 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
4437 self.check_expr_has_type_or_error(&cond, tcx.types.bool);
4438 let cond_diverging = self.diverges.get();
4439 self.check_block_no_value(&body);
4441 // We may never reach the body so it diverging means nothing.
4442 self.diverges.set(cond_diverging);
4446 // No way to know whether it's diverging because
4447 // of a `break` or an outer `break` or `return`.
4448 self.diverges.set(Diverges::Maybe);
4453 ExprKind::Loop(ref body, _, source) => {
4454 let coerce = match source {
4455 // you can only use break with a value from a normal `loop { }`
4456 hir::LoopSource::Loop => {
4457 let coerce_to = expected.coercion_target_type(self, body.span);
4458 Some(CoerceMany::new(coerce_to))
4461 hir::LoopSource::WhileLet |
4462 hir::LoopSource::ForLoop => {
4467 let ctxt = BreakableCtxt {
4469 may_break: false, // Will get updated if/when we find a `break`.
4472 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
4473 self.check_block_no_value(&body);
4477 // No way to know whether it's diverging because
4478 // of a `break` or an outer `break` or `return`.
4479 self.diverges.set(Diverges::Maybe);
4482 // If we permit break with a value, then result type is
4483 // the LUB of the breaks (possibly ! if none); else, it
4484 // is nil. This makes sense because infinite loops
4485 // (which would have type !) are only possible iff we
4486 // permit break with a value [1].
4487 if ctxt.coerce.is_none() && !ctxt.may_break {
4489 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
4491 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
4493 ExprKind::Match(ref discrim, ref arms, match_src) => {
4494 self.check_match(expr, &discrim, arms, expected, match_src)
4496 ExprKind::Closure(capture, ref decl, body_id, _, gen) => {
4497 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
4499 ExprKind::Block(ref body, _) => {
4500 self.check_block_with_expected(&body, expected)
4502 ExprKind::Call(ref callee, ref args) => {
4503 self.check_call(expr, &callee, args, expected)
4505 ExprKind::MethodCall(ref segment, span, ref args) => {
4506 self.check_method_call(expr, segment, span, args, expected, needs)
4508 ExprKind::Cast(ref e, ref t) => {
4509 // Find the type of `e`. Supply hints based on the type we are casting to,
4511 let t_cast = self.to_ty_saving_user_provided_ty(t);
4512 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
4513 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
4514 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
4516 // Eagerly check for some obvious errors.
4517 if t_expr.references_error() || t_cast.references_error() {
4520 // Defer other checks until we're done type checking.
4521 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
4522 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
4524 deferred_cast_checks.push(cast_check);
4527 Err(ErrorReported) => {
4533 ExprKind::Type(ref e, ref t) => {
4534 let ty = self.to_ty_saving_user_provided_ty(&t);
4535 self.check_expr_eq_type(&e, ty);
4538 ExprKind::Array(ref args) => {
4539 let uty = expected.to_option(self).and_then(|uty| {
4541 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
4546 let element_ty = if !args.is_empty() {
4547 let coerce_to = uty.unwrap_or_else(
4548 || self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span)));
4549 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
4550 assert_eq!(self.diverges.get(), Diverges::Maybe);
4552 let e_ty = self.check_expr_with_hint(e, coerce_to);
4553 let cause = self.misc(e.span);
4554 coerce.coerce(self, &cause, e, e_ty);
4556 coerce.complete(self)
4558 self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span))
4560 tcx.mk_array(element_ty, args.len() as u64)
4562 ExprKind::Repeat(ref element, ref count) => {
4563 let count_def_id = tcx.hir().local_def_id_from_hir_id(count.hir_id);
4564 let param_env = ty::ParamEnv::empty();
4565 let substs = InternalSubsts::identity_for_item(tcx.global_tcx(), count_def_id);
4566 let instance = ty::Instance::resolve(
4572 let global_id = GlobalId {
4576 let count = tcx.const_eval(param_env.and(global_id));
4578 let uty = match expected {
4579 ExpectHasType(uty) => {
4581 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
4588 let (element_ty, t) = match uty {
4590 self.check_expr_coercable_to_type(&element, uty);
4594 let ty = self.next_ty_var(TypeVariableOrigin::MiscVariable(element.span));
4595 let element_ty = self.check_expr_has_type_or_error(&element, ty);
4600 if let Ok(count) = count {
4601 let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1);
4603 // For [foo, ..n] where n > 1, `foo` must have
4605 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
4606 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
4610 if element_ty.references_error() {
4612 } else if let Ok(count) = count {
4613 tcx.mk_ty(ty::Array(t, tcx.mk_const(count)))
4618 ExprKind::Tup(ref elts) => {
4619 let flds = expected.only_has_type(self).and_then(|ty| {
4620 let ty = self.resolve_type_vars_with_obligations(ty);
4622 ty::Tuple(ref flds) => Some(&flds[..]),
4627 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
4628 let t = match flds {
4629 Some(ref fs) if i < fs.len() => {
4631 self.check_expr_coercable_to_type(&e, ety);
4635 self.check_expr_with_expectation(&e, NoExpectation)
4640 let tuple = tcx.mk_tup(elt_ts_iter);
4641 if tuple.references_error() {
4644 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
4648 ExprKind::Struct(ref qpath, ref fields, ref base_expr) => {
4649 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
4651 ExprKind::Field(ref base, field) => {
4652 self.check_field(expr, needs, &base, field)
4654 ExprKind::Index(ref base, ref idx) => {
4655 let base_t = self.check_expr_with_needs(&base, needs);
4656 let idx_t = self.check_expr(&idx);
4658 if base_t.references_error() {
4660 } else if idx_t.references_error() {
4663 let base_t = self.structurally_resolved_type(base.span, base_t);
4664 match self.lookup_indexing(expr, base, base_t, idx_t, needs) {
4665 Some((index_ty, element_ty)) => {
4666 // two-phase not needed because index_ty is never mutable
4667 self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No);
4672 type_error_struct!(tcx.sess, expr.span, base_t, E0608,
4673 "cannot index into a value of type `{}`",
4675 // Try to give some advice about indexing tuples.
4676 if let ty::Tuple(..) = base_t.sty {
4677 let mut needs_note = true;
4678 // If the index is an integer, we can show the actual
4679 // fixed expression:
4680 if let ExprKind::Lit(ref lit) = idx.node {
4681 if let ast::LitKind::Int(i,
4682 ast::LitIntType::Unsuffixed) = lit.node {
4683 let snip = tcx.sess.source_map().span_to_snippet(base.span);
4684 if let Ok(snip) = snip {
4685 err.span_suggestion(
4687 "to access tuple elements, use",
4688 format!("{}.{}", snip, i),
4689 Applicability::MachineApplicable,
4696 err.help("to access tuple elements, use tuple indexing \
4697 syntax (e.g., `tuple.0`)");
4706 ExprKind::Yield(ref value) => {
4707 match self.yield_ty {
4709 self.check_expr_coercable_to_type(&value, ty);
4712 struct_span_err!(self.tcx.sess, expr.span, E0627,
4713 "yield statement outside of generator literal").emit();
4718 hir::ExprKind::Err => {
4724 /// Type check assignment expression `expr` of form `lhs = rhs`.
4725 /// The expected type is `()` and is passsed to the function for the purposes of diagnostics.
4728 expr: &'gcx hir::Expr,
4729 expected: Expectation<'tcx>,
4730 lhs: &'gcx hir::Expr,
4731 rhs: &'gcx hir::Expr,
4733 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
4734 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
4736 let expected_ty = expected.coercion_target_type(self, expr.span);
4737 if expected_ty == self.tcx.types.bool {
4738 // The expected type is `bool` but this will result in `()` so we can reasonably
4739 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
4740 // The likely cause of this is `if foo = bar { .. }`.
4741 let actual_ty = self.tcx.mk_unit();
4742 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
4743 let msg = "try comparing for equality";
4744 let left = self.tcx.sess.source_map().span_to_snippet(lhs.span);
4745 let right = self.tcx.sess.source_map().span_to_snippet(rhs.span);
4746 if let (Ok(left), Ok(right)) = (left, right) {
4747 let help = format!("{} == {}", left, right);
4748 err.span_suggestion(expr.span, msg, help, Applicability::MaybeIncorrect);
4753 } else if !lhs.is_place_expr() {
4754 struct_span_err!(self.tcx.sess, expr.span, E0070,
4755 "invalid left-hand side expression")
4756 .span_label(expr.span, "left-hand of expression not valid")
4760 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
4762 if lhs_ty.references_error() || rhs_ty.references_error() {
4769 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4770 // The newly resolved definition is written into `type_dependent_defs`.
4771 fn finish_resolving_struct_path(&self,
4778 QPath::Resolved(ref maybe_qself, ref path) => {
4779 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4780 let ty = AstConv::def_to_ty(self, self_ty, path, true);
4783 QPath::TypeRelative(ref qself, ref segment) => {
4784 let ty = self.to_ty(qself);
4786 let def = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.node {
4791 let (ty, def) = AstConv::associated_path_to_ty(self, hir_id, path_span,
4792 ty, def, segment, true);
4794 // Write back the new resolution.
4795 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, def);
4802 /// Resolves associated value path into a base type and associated constant or method
4803 /// definition. The newly resolved definition is written into `type_dependent_defs`.
4804 pub fn resolve_ty_and_def_ufcs<'b>(&self,
4808 -> (Def, Option<Ty<'tcx>>, &'b [hir::PathSegment])
4810 debug!("resolve_ty_and_def_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
4811 let (ty, qself, item_segment) = match *qpath {
4812 QPath::Resolved(ref opt_qself, ref path) => {
4814 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4815 &path.segments[..]);
4817 QPath::TypeRelative(ref qself, ref segment) => {
4818 (self.to_ty(qself), qself, segment)
4821 if let Some(cached_def) = self.tables.borrow().type_dependent_def(hir_id) {
4822 // Return directly on cache hit. This is useful to avoid doubly reporting
4823 // errors with default match binding modes. See #44614.
4824 return (cached_def, Some(ty), slice::from_ref(&**item_segment))
4826 let item_name = item_segment.ident;
4827 let def = match self.resolve_ufcs(span, item_name, ty, hir_id) {
4830 let def = match error {
4831 method::MethodError::PrivateMatch(def, _) => def,
4834 if item_name.name != keywords::Invalid.name() {
4835 self.report_method_error(span,
4838 SelfSource::QPath(qself),
4846 // Write back the new resolution.
4847 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, def);
4848 (def, Some(ty), slice::from_ref(&**item_segment))
4851 pub fn check_decl_initializer(&self,
4852 local: &'gcx hir::Local,
4853 init: &'gcx hir::Expr) -> Ty<'tcx>
4855 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
4856 // for #42640 (default match binding modes).
4859 let ref_bindings = local.pat.contains_explicit_ref_binding();
4861 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
4862 if let Some(m) = ref_bindings {
4863 // Somewhat subtle: if we have a `ref` binding in the pattern,
4864 // we want to avoid introducing coercions for the RHS. This is
4865 // both because it helps preserve sanity and, in the case of
4866 // ref mut, for soundness (issue #23116). In particular, in
4867 // the latter case, we need to be clear that the type of the
4868 // referent for the reference that results is *equal to* the
4869 // type of the place it is referencing, and not some
4870 // supertype thereof.
4871 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4872 self.demand_eqtype(init.span, local_ty, init_ty);
4875 self.check_expr_coercable_to_type(init, local_ty)
4879 pub fn check_decl_local(&self, local: &'gcx hir::Local) {
4880 let t = self.local_ty(local.span, local.hir_id).decl_ty;
4881 self.write_ty(local.hir_id, t);
4883 if let Some(ref init) = local.init {
4884 let init_ty = self.check_decl_initializer(local, &init);
4885 if init_ty.references_error() {
4886 self.write_ty(local.hir_id, init_ty);
4890 self.check_pat_walk(
4893 ty::BindingMode::BindByValue(hir::Mutability::MutImmutable),
4896 let pat_ty = self.node_ty(local.pat.hir_id);
4897 if pat_ty.references_error() {
4898 self.write_ty(local.hir_id, pat_ty);
4902 pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
4903 // Don't do all the complex logic below for `DeclItem`.
4905 hir::StmtKind::Item(..) => return,
4906 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
4909 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
4911 // Hide the outer diverging and `has_errors` flags.
4912 let old_diverges = self.diverges.get();
4913 let old_has_errors = self.has_errors.get();
4914 self.diverges.set(Diverges::Maybe);
4915 self.has_errors.set(false);
4918 hir::StmtKind::Local(ref l) => {
4919 self.check_decl_local(&l);
4922 hir::StmtKind::Item(_) => {}
4923 hir::StmtKind::Expr(ref expr) => {
4924 // Check with expected type of `()`.
4925 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit());
4927 hir::StmtKind::Semi(ref expr) => {
4928 self.check_expr(&expr);
4932 // Combine the diverging and `has_error` flags.
4933 self.diverges.set(self.diverges.get() | old_diverges);
4934 self.has_errors.set(self.has_errors.get() | old_has_errors);
4937 pub fn check_block_no_value(&self, blk: &'gcx hir::Block) {
4938 let unit = self.tcx.mk_unit();
4939 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4941 // if the block produces a `!` value, that can always be
4942 // (effectively) coerced to unit.
4944 self.demand_suptype(blk.span, unit, ty);
4948 fn check_block_with_expected(&self,
4949 blk: &'gcx hir::Block,
4950 expected: Expectation<'tcx>) -> Ty<'tcx> {
4952 let mut fcx_ps = self.ps.borrow_mut();
4953 let unsafety_state = fcx_ps.recurse(blk);
4954 replace(&mut *fcx_ps, unsafety_state)
4957 // In some cases, blocks have just one exit, but other blocks
4958 // can be targeted by multiple breaks. This can happen both
4959 // with labeled blocks as well as when we desugar
4960 // a `try { ... }` expression.
4964 // 'a: { if true { break 'a Err(()); } Ok(()) }
4966 // Here we would wind up with two coercions, one from
4967 // `Err(())` and the other from the tail expression
4968 // `Ok(())`. If the tail expression is omitted, that's a
4969 // "forced unit" -- unless the block diverges, in which
4970 // case we can ignore the tail expression (e.g., `'a: {
4971 // break 'a 22; }` would not force the type of the block
4973 let tail_expr = blk.expr.as_ref();
4974 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4975 let coerce = if blk.targeted_by_break {
4976 CoerceMany::new(coerce_to_ty)
4978 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4979 Some(e) => slice::from_ref(e),
4982 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4985 let prev_diverges = self.diverges.get();
4986 let ctxt = BreakableCtxt {
4987 coerce: Some(coerce),
4991 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4992 for s in &blk.stmts {
4996 // check the tail expression **without** holding the
4997 // `enclosing_breakables` lock below.
4998 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
5000 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5001 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
5002 let coerce = ctxt.coerce.as_mut().unwrap();
5003 if let Some(tail_expr_ty) = tail_expr_ty {
5004 let tail_expr = tail_expr.unwrap();
5005 let cause = self.cause(tail_expr.span,
5006 ObligationCauseCode::BlockTailExpression(blk.hir_id));
5012 // Subtle: if there is no explicit tail expression,
5013 // that is typically equivalent to a tail expression
5014 // of `()` -- except if the block diverges. In that
5015 // case, there is no value supplied from the tail
5016 // expression (assuming there are no other breaks,
5017 // this implies that the type of the block will be
5020 // #41425 -- label the implicit `()` as being the
5021 // "found type" here, rather than the "expected type".
5022 if !self.diverges.get().always() {
5023 // #50009 -- Do not point at the entire fn block span, point at the return type
5024 // span, as it is the cause of the requirement, and
5025 // `consider_hint_about_removing_semicolon` will point at the last expression
5026 // if it were a relevant part of the error. This improves usability in editors
5027 // that highlight errors inline.
5028 let mut sp = blk.span;
5029 let mut fn_span = None;
5030 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
5031 let ret_sp = decl.output.span();
5032 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
5033 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
5034 // output would otherwise be incorrect and even misleading. Make sure
5035 // the span we're aiming at correspond to a `fn` body.
5036 if block_sp == blk.span {
5038 fn_span = Some(ident.span);
5042 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
5043 if let Some(expected_ty) = expected.only_has_type(self) {
5044 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
5046 if let Some(fn_span) = fn_span {
5047 err.span_label(fn_span, "this function's body doesn't return");
5055 // If we can break from the block, then the block's exit is always reachable
5056 // (... as long as the entry is reachable) - regardless of the tail of the block.
5057 self.diverges.set(prev_diverges);
5060 let mut ty = ctxt.coerce.unwrap().complete(self);
5062 if self.has_errors.get() || ty.references_error() {
5063 ty = self.tcx.types.err
5066 self.write_ty(blk.hir_id, ty);
5068 *self.ps.borrow_mut() = prev;
5072 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
5073 let node = self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_item(id));
5075 Node::Item(&hir::Item {
5076 node: hir::ItemKind::Fn(_, _, _, body_id), ..
5078 Node::ImplItem(&hir::ImplItem {
5079 node: hir::ImplItemKind::Method(_, body_id), ..
5081 let body = self.tcx.hir().body(body_id);
5082 if let ExprKind::Block(block, _) = &body.value.node {
5083 return Some(block.span);
5091 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
5092 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(hir::FnDecl, ast::Ident)> {
5093 let parent = self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_item(blk_id));
5094 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
5097 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
5098 fn get_node_fn_decl(&self, node: Node<'_>) -> Option<(hir::FnDecl, ast::Ident, bool)> {
5100 Node::Item(&hir::Item {
5101 ident, node: hir::ItemKind::Fn(ref decl, ..), ..
5102 }) => decl.clone().and_then(|decl| {
5103 // This is less than ideal, it will not suggest a return type span on any
5104 // method called `main`, regardless of whether it is actually the entry point,
5105 // but it will still present it as the reason for the expected type.
5106 Some((decl, ident, ident.name != Symbol::intern("main")))
5108 Node::TraitItem(&hir::TraitItem {
5109 ident, node: hir::TraitItemKind::Method(hir::MethodSig {
5112 }) => decl.clone().and_then(|decl| Some((decl, ident, true))),
5113 Node::ImplItem(&hir::ImplItem {
5114 ident, node: hir::ImplItemKind::Method(hir::MethodSig {
5117 }) => decl.clone().and_then(|decl| Some((decl, ident, false))),
5122 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
5123 /// suggestion can be made, `None` otherwise.
5124 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(hir::FnDecl, bool)> {
5125 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
5126 // `while` before reaching it, as block tail returns are not available in them.
5127 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
5128 let parent = self.tcx.hir().get_by_hir_id(blk_id);
5129 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
5133 /// On implicit return expressions with mismatched types, provides the following suggestions:
5135 /// - Points out the method's return type as the reason for the expected type.
5136 /// - Possible missing semicolon.
5137 /// - Possible missing return type if the return type is the default, and not `fn main()`.
5138 pub fn suggest_mismatched_types_on_tail(
5140 err: &mut DiagnosticBuilder<'tcx>,
5141 expression: &'gcx hir::Expr,
5147 self.suggest_missing_semicolon(err, expression, expected, cause_span);
5148 let mut pointing_at_return_type = false;
5149 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
5150 pointing_at_return_type = self.suggest_missing_return_type(
5151 err, &fn_decl, expected, found, can_suggest);
5153 self.suggest_ref_or_into(err, expression, expected, found);
5154 pointing_at_return_type
5157 pub fn suggest_ref_or_into(
5159 err: &mut DiagnosticBuilder<'tcx>,
5164 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
5165 err.span_suggestion(
5169 Applicability::MachineApplicable,
5171 } else if !self.check_for_cast(err, expr, found, expected) {
5172 let methods = self.get_conversion_methods(expr.span, expected, found);
5173 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
5174 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
5175 .filter_map(|(receiver, method)| {
5176 let method_call = format!(".{}()", method.ident);
5177 if receiver.ends_with(&method_call) {
5178 None // do not suggest code that is already there (#53348)
5180 let method_call_list = [".to_vec()", ".to_string()"];
5181 if receiver.ends_with(".clone()")
5182 && method_call_list.contains(&method_call.as_str()) {
5183 let max_len = receiver.rfind(".").unwrap();
5184 Some(format!("{}{}", &receiver[..max_len], method_call))
5187 Some(format!("{}{}", receiver, method_call))
5191 if suggestions.peek().is_some() {
5192 err.span_suggestions(
5194 "try using a conversion method",
5196 Applicability::MaybeIncorrect,
5203 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
5207 /// bar_that_returns_u32()
5211 /// This routine checks if the return expression in a block would make sense on its own as a
5212 /// statement and the return type has been left as default or has been specified as `()`. If so,
5213 /// it suggests adding a semicolon.
5214 fn suggest_missing_semicolon(&self,
5215 err: &mut DiagnosticBuilder<'tcx>,
5216 expression: &'gcx hir::Expr,
5219 if expected.is_unit() {
5220 // `BlockTailExpression` only relevant if the tail expr would be
5221 // useful on its own.
5222 match expression.node {
5223 ExprKind::Call(..) |
5224 ExprKind::MethodCall(..) |
5226 ExprKind::While(..) |
5227 ExprKind::Loop(..) |
5228 ExprKind::Match(..) |
5229 ExprKind::Block(..) => {
5230 let sp = self.tcx.sess.source_map().next_point(cause_span);
5231 err.span_suggestion(
5233 "try adding a semicolon",
5235 Applicability::MachineApplicable);
5242 /// A possible error is to forget to add a return type that is needed:
5246 /// bar_that_returns_u32()
5250 /// This routine checks if the return type is left as default, the method is not part of an
5251 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
5253 fn suggest_missing_return_type(
5255 err: &mut DiagnosticBuilder<'tcx>,
5256 fn_decl: &hir::FnDecl,
5261 // Only suggest changing the return type for methods that
5262 // haven't set a return type at all (and aren't `fn main()` or an impl).
5263 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
5264 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
5265 err.span_suggestion(
5267 "try adding a return type",
5268 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
5269 Applicability::MachineApplicable);
5272 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
5273 err.span_label(span, "possibly return type missing here?");
5276 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
5277 // `fn main()` must return `()`, do not suggest changing return type
5278 err.span_label(span, "expected `()` because of default return type");
5281 // expectation was caused by something else, not the default return
5282 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
5283 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
5284 // Only point to return type if the expected type is the return type, as if they
5285 // are not, the expectation must have been caused by something else.
5286 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.node);
5288 let ty = AstConv::ast_ty_to_ty(self, ty);
5289 debug!("suggest_missing_return_type: return type {:?}", ty);
5290 debug!("suggest_missing_return_type: expected type {:?}", ty);
5291 if ty.sty == expected.sty {
5292 err.span_label(sp, format!("expected `{}` because of return type",
5301 /// A common error is to add an extra semicolon:
5304 /// fn foo() -> usize {
5309 /// This routine checks if the final statement in a block is an
5310 /// expression with an explicit semicolon whose type is compatible
5311 /// with `expected_ty`. If so, it suggests removing the semicolon.
5312 fn consider_hint_about_removing_semicolon(
5314 blk: &'gcx hir::Block,
5315 expected_ty: Ty<'tcx>,
5316 err: &mut DiagnosticBuilder<'_>,
5318 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
5319 err.span_suggestion(
5321 "consider removing this semicolon",
5323 Applicability::MachineApplicable,
5328 fn could_remove_semicolon(
5330 blk: &'gcx hir::Block,
5331 expected_ty: Ty<'tcx>,
5333 // Be helpful when the user wrote `{... expr;}` and
5334 // taking the `;` off is enough to fix the error.
5335 let last_stmt = blk.stmts.last()?;
5336 let last_expr = match last_stmt.node {
5337 hir::StmtKind::Semi(ref e) => e,
5340 let last_expr_ty = self.node_ty(last_expr.hir_id);
5341 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
5344 let original_span = original_sp(last_stmt.span, blk.span);
5345 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
5348 // Rewrite `SelfCtor` to `Ctor`
5349 pub fn rewrite_self_ctor(&self, def: Def, span: Span) -> (Def, DefId, Ty<'tcx>) {
5351 if let Def::SelfCtor(impl_def_id) = def {
5352 let ty = self.impl_self_ty(span, impl_def_id).ty;
5353 let adt_def = ty.ty_adt_def();
5356 Some(adt_def) if adt_def.has_ctor() => {
5357 let variant = adt_def.non_enum_variant();
5358 let ctor_def_id = variant.ctor_def_id.unwrap();
5359 let def = Def::Ctor(ctor_def_id, CtorOf::Struct, variant.ctor_kind);
5360 (def, ctor_def_id, tcx.type_of(ctor_def_id))
5363 let mut err = tcx.sess.struct_span_err(span,
5364 "the `Self` constructor can only be used with tuple or unit structs");
5365 if let Some(adt_def) = adt_def {
5366 match adt_def.adt_kind() {
5368 err.help("did you mean to use one of the enum's variants?");
5372 err.span_suggestion(
5374 "use curly brackets",
5375 String::from("Self { /* fields */ }"),
5376 Applicability::HasPlaceholders,
5383 (def, impl_def_id, tcx.types.err)
5387 let def_id = def.def_id();
5389 // The things we are substituting into the type should not contain
5390 // escaping late-bound regions, and nor should the base type scheme.
5391 let ty = tcx.type_of(def_id);
5396 // Instantiates the given path, which must refer to an item with the given
5397 // number of type parameters and type.
5398 pub fn instantiate_value_path(&self,
5399 segments: &[hir::PathSegment],
5400 self_ty: Option<Ty<'tcx>>,
5404 -> (Ty<'tcx>, Def) {
5406 "instantiate_value_path(segments={:?}, self_ty={:?}, def={:?}, hir_id={})",
5416 Def::Local(hid) | Def::Upvar(hid, ..) => {
5417 let ty = self.local_ty(span, hid).decl_ty;
5418 let ty = self.normalize_associated_types_in(span, &ty);
5419 self.write_ty(hir_id, ty);
5425 let (def, def_id, ty) = self.rewrite_self_ctor(def, span);
5426 let path_segs = AstConv::def_ids_for_path_segments(self, segments, self_ty, def);
5428 let mut user_self_ty = None;
5429 let mut is_alias_variant_ctor = false;
5431 Def::Ctor(_, CtorOf::Variant, _) => {
5432 if let Some(self_ty) = self_ty {
5433 let adt_def = self_ty.ty_adt_def().unwrap();
5434 user_self_ty = Some(UserSelfTy {
5435 impl_def_id: adt_def.did,
5438 is_alias_variant_ctor = true;
5441 Def::Method(def_id) |
5442 Def::AssociatedConst(def_id) => {
5443 let container = tcx.associated_item(def_id).container;
5444 debug!("instantiate_value_path: def={:?} container={:?}", def, container);
5446 ty::TraitContainer(trait_did) => {
5447 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
5449 ty::ImplContainer(impl_def_id) => {
5450 if segments.len() == 1 {
5451 // `<T>::assoc` will end up here, and so
5452 // can `T::assoc`. It this came from an
5453 // inherent impl, we need to record the
5454 // `T` for posterity (see `UserSelfTy` for
5456 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
5457 user_self_ty = Some(UserSelfTy {
5468 // Now that we have categorized what space the parameters for each
5469 // segment belong to, let's sort out the parameters that the user
5470 // provided (if any) into their appropriate spaces. We'll also report
5471 // errors if type parameters are provided in an inappropriate place.
5473 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
5474 let generics_has_err = AstConv::prohibit_generics(
5475 self, segments.iter().enumerate().filter_map(|(index, seg)| {
5476 if !generic_segs.contains(&index) || is_alias_variant_ctor {
5482 if generics_has_err {
5483 // Don't try to infer type parameters when prohibited generic arguments were given.
5484 user_self_ty = None;
5487 // Now we have to compare the types that the user *actually*
5488 // provided against the types that were *expected*. If the user
5489 // did not provide any types, then we want to substitute inference
5490 // variables. If the user provided some types, we may still need
5491 // to add defaults. If the user provided *too many* types, that's
5494 let mut infer_args_for_err = FxHashSet::default();
5495 for &PathSeg(def_id, index) in &path_segs {
5496 let seg = &segments[index];
5497 let generics = tcx.generics_of(def_id);
5498 // Argument-position `impl Trait` is treated as a normal generic
5499 // parameter internally, but we don't allow users to specify the
5500 // parameter's value explicitly, so we have to do some error-
5502 let suppress_errors = AstConv::check_generic_arg_count_for_call(
5507 false, // `is_method_call`
5509 if suppress_errors {
5510 infer_args_for_err.insert(index);
5511 self.set_tainted_by_errors(); // See issue #53251.
5515 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
5516 tcx.generics_of(*def_id).has_self
5517 }).unwrap_or(false);
5519 let substs = AstConv::create_substs_for_generic_args(
5525 // Provide the generic args, and whether types should be inferred.
5527 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
5530 // If we've encountered an `impl Trait`-related error, we're just
5531 // going to infer the arguments for better error messages.
5532 if !infer_args_for_err.contains(&index) {
5533 // Check whether the user has provided generic arguments.
5534 if let Some(ref data) = segments[index].args {
5535 return (Some(data), segments[index].infer_types);
5538 return (None, segments[index].infer_types);
5543 // Provide substitutions for parameters for which (valid) arguments have been provided.
5545 match (¶m.kind, arg) {
5546 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
5547 AstConv::ast_region_to_region(self, lt, Some(param)).into()
5549 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
5550 self.to_ty(ty).into()
5552 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
5553 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
5555 _ => unreachable!(),
5558 // Provide substitutions for parameters for which arguments are inferred.
5559 |substs, param, infer_types| {
5561 GenericParamDefKind::Lifetime => {
5562 self.re_infer(span, Some(param)).unwrap().into()
5564 GenericParamDefKind::Type { has_default, .. } => {
5565 if !infer_types && has_default {
5566 // If we have a default, then we it doesn't matter that we're not
5567 // inferring the type arguments: we provide the default where any
5569 let default = tcx.type_of(param.def_id);
5572 default.subst_spanned(tcx, substs.unwrap(), Some(span))
5575 // If no type arguments were provided, we have to infer them.
5576 // This case also occurs as a result of some malformed input, e.g.
5577 // a lifetime argument being given instead of a type parameter.
5578 // Using inference instead of `Error` gives better error messages.
5579 self.var_for_def(span, param)
5582 GenericParamDefKind::Const => {
5583 // FIXME(const_generics:defaults)
5584 // No const parameters were provided, we have to infer them.
5585 self.var_for_def(span, param)
5590 assert!(!substs.has_escaping_bound_vars());
5591 assert!(!ty.has_escaping_bound_vars());
5593 // First, store the "user substs" for later.
5594 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
5596 // Add all the obligations that are required, substituting and
5597 // normalized appropriately.
5598 let bounds = self.instantiate_bounds(span, def_id, &substs);
5599 self.add_obligations_for_parameters(
5600 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
5603 // Substitute the values for the type parameters into the type of
5604 // the referenced item.
5605 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
5607 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
5608 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
5609 // is inherent, there is no `Self` parameter; instead, the impl needs
5610 // type parameters, which we can infer by unifying the provided `Self`
5611 // with the substituted impl type.
5612 // This also occurs for an enum variant on a type alias.
5613 let ty = tcx.type_of(impl_def_id);
5615 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
5616 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
5617 Ok(ok) => self.register_infer_ok_obligations(ok),
5620 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
5627 self.check_rustc_args_require_const(def_id, hir_id, span);
5629 debug!("instantiate_value_path: type of {:?} is {:?}",
5632 self.write_substs(hir_id, substs);
5634 (ty_substituted, def)
5637 fn check_rustc_args_require_const(&self,
5641 // We're only interested in functions tagged with
5642 // #[rustc_args_required_const], so ignore anything that's not.
5643 if !self.tcx.has_attr(def_id, "rustc_args_required_const") {
5647 // If our calling expression is indeed the function itself, we're good!
5648 // If not, generate an error that this can only be called directly.
5649 if let Node::Expr(expr) = self.tcx.hir().get_by_hir_id(
5650 self.tcx.hir().get_parent_node_by_hir_id(hir_id))
5652 if let ExprKind::Call(ref callee, ..) = expr.node {
5653 if callee.hir_id == hir_id {
5659 self.tcx.sess.span_err(span, "this function can only be invoked \
5660 directly, not through a function pointer");
5663 // Resolves `typ` by a single level if `typ` is a type variable.
5664 // If no resolution is possible, then an error is reported.
5665 // Numeric inference variables may be left unresolved.
5666 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5667 let ty = self.resolve_type_vars_with_obligations(ty);
5668 if !ty.is_ty_var() {
5671 if !self.is_tainted_by_errors() {
5672 self.need_type_info_err((**self).body_id, sp, ty)
5673 .note("type must be known at this point")
5676 self.demand_suptype(sp, self.tcx.types.err, ty);
5681 fn with_breakable_ctxt<F: FnOnce() -> R, R>(&self, id: hir::HirId,
5682 ctxt: BreakableCtxt<'gcx, 'tcx>, f: F)
5683 -> (BreakableCtxt<'gcx, 'tcx>, R) {
5686 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5687 index = enclosing_breakables.stack.len();
5688 enclosing_breakables.by_id.insert(id, index);
5689 enclosing_breakables.stack.push(ctxt);
5693 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5694 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5695 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5696 enclosing_breakables.stack.pop().expect("missing breakable context")
5701 /// Instantiate a QueryResponse in a probe context, without a
5702 /// good ObligationCause.
5703 fn probe_instantiate_query_response(
5706 original_values: &OriginalQueryValues<'tcx>,
5707 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5708 ) -> InferResult<'tcx, Ty<'tcx>>
5710 self.instantiate_query_response_and_region_obligations(
5711 &traits::ObligationCause::misc(span, self.body_id),
5717 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5718 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5719 let mut contained_in_place = false;
5721 while let hir::Node::Expr(parent_expr) =
5722 self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_node_by_hir_id(expr_id))
5724 match &parent_expr.node {
5725 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5726 if lhs.hir_id == expr_id {
5727 contained_in_place = true;
5733 expr_id = parent_expr.hir_id;
5740 pub fn check_bounds_are_used<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
5741 generics: &ty::Generics,
5743 let own_counts = generics.own_counts();
5745 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5751 // FIXME(const_generics): we probably want to check the bounds for const parameters too.
5753 if own_counts.types == 0 {
5757 // Make a vector of booleans initially false, set to true when used.
5758 let mut types_used = vec![false; own_counts.types];
5760 for leaf_ty in ty.walk() {
5761 if let ty::Param(ty::ParamTy { idx, .. }) = leaf_ty.sty {
5762 debug!("Found use of ty param num {}", idx);
5763 types_used[idx as usize - own_counts.lifetimes] = true;
5764 } else if let ty::Error = leaf_ty.sty {
5765 // If there is already another error, do not emit
5766 // an error for not using a type Parameter.
5767 assert!(tcx.sess.err_count() > 0);
5772 let types = generics.params.iter().filter(|param| match param.kind {
5773 ty::GenericParamDefKind::Type { .. } => true,
5776 for (&used, param) in types_used.iter().zip(types) {
5778 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5779 let span = tcx.hir().span_by_hir_id(id);
5780 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5781 .span_label(span, "unused type parameter")
5787 fn fatally_break_rust(sess: &Session) {
5788 let handler = sess.diagnostic();
5789 handler.span_bug_no_panic(
5791 "It looks like you're trying to break rust; would you like some ICE?",
5793 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5794 handler.note_without_error(
5795 "we would appreciate a joke overview: \
5796 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5798 handler.note_without_error(&format!("rustc {} running on {}",
5799 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5800 crate::session::config::host_triple(),
5804 fn potentially_plural_count(count: usize, word: &str) -> String {
5805 format!("{} {}{}", count, word, if count == 1 { "" } else { "s" })