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, Res, DefKind};
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_target::spec::abi::Abi;
101 use rustc::infer::opaque_types::OpaqueTypeDecl;
102 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
103 use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
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, Const, 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};
120 use syntax_pos::hygiene::CompilerDesugaringKind;
123 use syntax::feature_gate::{GateIssue, emit_feature_err};
125 use syntax::source_map::{DUMMY_SP, original_sp};
126 use syntax::symbol::{Symbol, LocalInternedString, kw, sym};
127 use syntax::util::lev_distance::find_best_match_for_name;
129 use std::cell::{Cell, RefCell, Ref, RefMut};
130 use std::collections::hash_map::Entry;
132 use std::fmt::Display;
134 use std::mem::replace;
135 use std::ops::{self, Deref};
138 use crate::require_c_abi_if_c_variadic;
139 use crate::session::Session;
140 use crate::session::config::EntryFnType;
141 use crate::TypeAndSubsts;
143 use crate::util::captures::Captures;
144 use crate::util::common::{ErrorReported, indenter};
145 use crate::util::nodemap::{DefIdMap, DefIdSet, FxHashMap, FxHashSet, HirIdMap};
147 pub use self::Expectation::*;
148 use self::autoderef::Autoderef;
149 use self::callee::DeferredCallResolution;
150 use self::coercion::{CoerceMany, DynamicCoerceMany};
151 pub use self::compare_method::{compare_impl_method, compare_const_impl};
152 use self::method::{MethodCallee, SelfSource};
153 use self::TupleArgumentsFlag::*;
155 /// The type of a local binding, including the revealed type for anon types.
156 #[derive(Copy, Clone)]
157 pub struct LocalTy<'tcx> {
159 revealed_ty: Ty<'tcx>
162 /// A wrapper for `InferCtxt`'s `in_progress_tables` field.
163 #[derive(Copy, Clone)]
164 struct MaybeInProgressTables<'a, 'tcx: 'a> {
165 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
168 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
169 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
170 match self.maybe_tables {
171 Some(tables) => tables.borrow(),
173 bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables")
178 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
179 match self.maybe_tables {
180 Some(tables) => tables.borrow_mut(),
182 bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables")
188 /// Closures defined within the function. For example:
191 /// bar(move|| { ... })
194 /// Here, the function `foo()` and the closure passed to
195 /// `bar()` will each have their own `FnCtxt`, but they will
196 /// share the inherited fields.
197 pub struct Inherited<'a, 'tcx: 'a> {
198 infcx: InferCtxt<'a, 'tcx>,
200 tables: MaybeInProgressTables<'a, 'tcx>,
202 locals: RefCell<HirIdMap<LocalTy<'tcx>>>,
204 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
206 // Some additional `Sized` obligations badly affect type inference.
207 // These obligations are added in a later stage of typeck.
208 deferred_sized_obligations: RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
210 // When we process a call like `c()` where `c` is a closure type,
211 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
212 // `FnOnce` closure. In that case, we defer full resolution of the
213 // call until upvar inference can kick in and make the
214 // decision. We keep these deferred resolutions grouped by the
215 // def-id of the closure, so that once we decide, we can easily go
216 // back and process them.
217 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
219 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
221 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>)>>,
223 // Opaque types found in explicit return types and their
224 // associated fresh inference variable. Writeback resolves these
225 // variables to get the concrete type, which can be used to
226 // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
227 opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
229 /// Each type parameter has an implicit region bound that
230 /// indicates it must outlive at least the function body (the user
231 /// may specify stronger requirements). This field indicates the
232 /// region of the callee. If it is `None`, then the parameter
233 /// environment is for an item or something where the "callee" is
235 implicit_region_bound: Option<ty::Region<'tcx>>,
237 body_id: Option<hir::BodyId>,
240 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
241 type Target = InferCtxt<'a, 'tcx>;
242 fn deref(&self) -> &Self::Target {
247 /// When type-checking an expression, we propagate downward
248 /// whatever type hint we are able in the form of an `Expectation`.
249 #[derive(Copy, Clone, Debug)]
250 pub enum Expectation<'tcx> {
251 /// We know nothing about what type this expression should have.
254 /// This expression should have the type given (or some subtype).
255 ExpectHasType(Ty<'tcx>),
257 /// This expression will be cast to the `Ty`.
258 ExpectCastableToType(Ty<'tcx>),
260 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
261 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
262 ExpectRvalueLikeUnsized(Ty<'tcx>),
265 impl<'a, 'tcx> Expectation<'tcx> {
266 // Disregard "castable to" expectations because they
267 // can lead us astray. Consider for example `if cond
268 // {22} else {c} as u8` -- if we propagate the
269 // "castable to u8" constraint to 22, it will pick the
270 // type 22u8, which is overly constrained (c might not
271 // be a u8). In effect, the problem is that the
272 // "castable to" expectation is not the tightest thing
273 // we can say, so we want to drop it in this case.
274 // The tightest thing we can say is "must unify with
275 // else branch". Note that in the case of a "has type"
276 // constraint, this limitation does not hold.
278 // If the expected type is just a type variable, then don't use
279 // an expected type. Otherwise, we might write parts of the type
280 // when checking the 'then' block which are incompatible with the
282 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
284 ExpectHasType(ety) => {
285 let ety = fcx.shallow_resolve(ety);
286 if !ety.is_ty_var() {
292 ExpectRvalueLikeUnsized(ety) => {
293 ExpectRvalueLikeUnsized(ety)
299 /// Provides an expectation for an rvalue expression given an *optional*
300 /// hint, which is not required for type safety (the resulting type might
301 /// be checked higher up, as is the case with `&expr` and `box expr`), but
302 /// is useful in determining the concrete type.
304 /// The primary use case is where the expected type is a fat pointer,
305 /// like `&[isize]`. For example, consider the following statement:
307 /// let x: &[isize] = &[1, 2, 3];
309 /// In this case, the expected type for the `&[1, 2, 3]` expression is
310 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
311 /// expectation `ExpectHasType([isize])`, that would be too strong --
312 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
313 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
314 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
315 /// which still is useful, because it informs integer literals and the like.
316 /// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
317 /// for examples of where this comes up,.
318 fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
319 match fcx.tcx.struct_tail(ty).sty {
320 ty::Slice(_) | ty::Str | ty::Dynamic(..) => {
321 ExpectRvalueLikeUnsized(ty)
323 _ => ExpectHasType(ty)
327 // Resolves `expected` by a single level if it is a variable. If
328 // there is no expected type or resolution is not possible (e.g.,
329 // no constraints yet present), just returns `None`.
330 fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
332 NoExpectation => NoExpectation,
333 ExpectCastableToType(t) => {
334 ExpectCastableToType(fcx.resolve_vars_if_possible(&t))
336 ExpectHasType(t) => {
337 ExpectHasType(fcx.resolve_vars_if_possible(&t))
339 ExpectRvalueLikeUnsized(t) => {
340 ExpectRvalueLikeUnsized(fcx.resolve_vars_if_possible(&t))
345 fn to_option(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
346 match self.resolve(fcx) {
347 NoExpectation => None,
348 ExpectCastableToType(ty) |
350 ExpectRvalueLikeUnsized(ty) => Some(ty),
354 /// It sometimes happens that we want to turn an expectation into
355 /// a **hard constraint** (i.e., something that must be satisfied
356 /// for the program to type-check). `only_has_type` will return
357 /// such a constraint, if it exists.
358 fn only_has_type(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
359 match self.resolve(fcx) {
360 ExpectHasType(ty) => Some(ty),
361 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
365 /// Like `only_has_type`, but instead of returning `None` if no
366 /// hard constraint exists, creates a fresh type variable.
367 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> Ty<'tcx> {
368 self.only_has_type(fcx)
370 fcx.next_ty_var(TypeVariableOrigin {
371 kind: TypeVariableOriginKind::MiscVariable,
378 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
385 fn maybe_mut_place(m: hir::Mutability) -> Self {
387 hir::MutMutable => Needs::MutPlace,
388 hir::MutImmutable => Needs::None,
393 #[derive(Copy, Clone)]
394 pub struct UnsafetyState {
396 pub unsafety: hir::Unsafety,
397 pub unsafe_push_count: u32,
402 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
403 UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
406 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
407 match self.unsafety {
408 // If this unsafe, then if the outer function was already marked as
409 // unsafe we shouldn't attribute the unsafe'ness to the block. This
410 // way the block can be warned about instead of ignoring this
411 // extraneous block (functions are never warned about).
412 hir::Unsafety::Unsafe if self.from_fn => *self,
415 let (unsafety, def, count) = match blk.rules {
416 hir::PushUnsafeBlock(..) =>
417 (unsafety, blk.hir_id, self.unsafe_push_count.checked_add(1).unwrap()),
418 hir::PopUnsafeBlock(..) =>
419 (unsafety, blk.hir_id, self.unsafe_push_count.checked_sub(1).unwrap()),
420 hir::UnsafeBlock(..) =>
421 (hir::Unsafety::Unsafe, blk.hir_id, self.unsafe_push_count),
423 (unsafety, self.def, self.unsafe_push_count),
427 unsafe_push_count: count,
434 #[derive(Debug, Copy, Clone)]
440 /// Tracks whether executing a node may exit normally (versus
441 /// return/break/panic, which "diverge", leaving dead code in their
442 /// wake). Tracked semi-automatically (through type variables marked
443 /// as diverging), with some manual adjustments for control-flow
444 /// primitives (approximating a CFG).
445 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
447 /// Potentially unknown, some cases converge,
448 /// others require a CFG to determine them.
451 /// Definitely known to diverge and therefore
452 /// not reach the next sibling or its parent.
455 /// Same as `Always` but with a reachability
456 /// warning already emitted.
460 // Convenience impls for combinig `Diverges`.
462 impl ops::BitAnd for Diverges {
464 fn bitand(self, other: Self) -> Self {
465 cmp::min(self, other)
469 impl ops::BitOr for Diverges {
471 fn bitor(self, other: Self) -> Self {
472 cmp::max(self, other)
476 impl ops::BitAndAssign for Diverges {
477 fn bitand_assign(&mut self, other: Self) {
478 *self = *self & other;
482 impl ops::BitOrAssign for Diverges {
483 fn bitor_assign(&mut self, other: Self) {
484 *self = *self | other;
489 fn always(self) -> bool {
490 self >= Diverges::Always
494 pub struct BreakableCtxt<'tcx> {
497 // this is `null` for loops where break with a value is illegal,
498 // such as `while`, `for`, and `while let`
499 coerce: Option<DynamicCoerceMany<'tcx>>,
502 pub struct EnclosingBreakables<'tcx> {
503 stack: Vec<BreakableCtxt<'tcx>>,
504 by_id: HirIdMap<usize>,
507 impl<'tcx> EnclosingBreakables<'tcx> {
508 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
509 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
510 bug!("could not find enclosing breakable with id {}", target_id);
516 pub struct FnCtxt<'a, 'tcx: 'a> {
519 /// The parameter environment used for proving trait obligations
520 /// in this function. This can change when we descend into
521 /// closures (as they bring new things into scope), hence it is
522 /// not part of `Inherited` (as of the time of this writing,
523 /// closures do not yet change the environment, but they will
525 param_env: ty::ParamEnv<'tcx>,
527 /// Number of errors that had been reported when we started
528 /// checking this function. On exit, if we find that *more* errors
529 /// have been reported, we will skip regionck and other work that
530 /// expects the types within the function to be consistent.
531 err_count_on_creation: usize,
533 ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
534 ret_coercion_span: RefCell<Option<Span>>,
536 yield_ty: Option<Ty<'tcx>>,
538 ps: RefCell<UnsafetyState>,
540 /// Whether the last checked node generates a divergence (e.g.,
541 /// `return` will set this to `Always`). In general, when entering
542 /// an expression or other node in the tree, the initial value
543 /// indicates whether prior parts of the containing expression may
544 /// have diverged. It is then typically set to `Maybe` (and the
545 /// old value remembered) for processing the subparts of the
546 /// current expression. As each subpart is processed, they may set
547 /// the flag to `Always`, etc. Finally, at the end, we take the
548 /// result and "union" it with the original value, so that when we
549 /// return the flag indicates if any subpart of the parent
550 /// expression (up to and including this part) has diverged. So,
551 /// if you read it after evaluating a subexpression `X`, the value
552 /// you get indicates whether any subexpression that was
553 /// evaluating up to and including `X` diverged.
555 /// We currently use this flag only for diagnostic purposes:
557 /// - To warn about unreachable code: if, after processing a
558 /// sub-expression but before we have applied the effects of the
559 /// current node, we see that the flag is set to `Always`, we
560 /// can issue a warning. This corresponds to something like
561 /// `foo(return)`; we warn on the `foo()` expression. (We then
562 /// update the flag to `WarnedAlways` to suppress duplicate
563 /// reports.) Similarly, if we traverse to a fresh statement (or
564 /// tail expression) from a `Always` setting, we will issue a
565 /// warning. This corresponds to something like `{return;
566 /// foo();}` or `{return; 22}`, where we would warn on the
569 /// An expression represents dead code if, after checking it,
570 /// the diverges flag is set to something other than `Maybe`.
571 diverges: Cell<Diverges>,
573 /// Whether any child nodes have any type errors.
574 has_errors: Cell<bool>,
576 enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
578 inh: &'a Inherited<'a, 'tcx>,
581 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
582 type Target = Inherited<'a, 'tcx>;
583 fn deref(&self) -> &Self::Target {
588 /// Helper type of a temporary returned by `Inherited::build(...)`.
589 /// Necessary because we can't write the following bound:
590 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
591 pub struct InheritedBuilder<'tcx> {
592 infcx: infer::InferCtxtBuilder<'tcx>,
596 impl Inherited<'_, 'tcx> {
597 pub fn build(tcx: TyCtxt<'tcx>, def_id: DefId) -> InheritedBuilder<'tcx> {
598 let hir_id_root = if def_id.is_local() {
599 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
600 DefId::local(hir_id.owner)
606 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
612 impl<'tcx> InheritedBuilder<'tcx> {
613 fn enter<F, R>(&mut self, f: F) -> R
615 F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
617 let def_id = self.def_id;
618 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
622 impl Inherited<'a, 'tcx> {
623 fn new(infcx: InferCtxt<'a, 'tcx>, def_id: DefId) -> Self {
625 let item_id = tcx.hir().as_local_hir_id(def_id);
626 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by_by_hir_id(id));
627 let implicit_region_bound = body_id.map(|body_id| {
628 let body = tcx.hir().body(body_id);
629 tcx.mk_region(ty::ReScope(region::Scope {
630 id: body.value.hir_id.local_id,
631 data: region::ScopeData::CallSite
636 tables: MaybeInProgressTables {
637 maybe_tables: infcx.in_progress_tables,
640 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
641 locals: RefCell::new(Default::default()),
642 deferred_sized_obligations: RefCell::new(Vec::new()),
643 deferred_call_resolutions: RefCell::new(Default::default()),
644 deferred_cast_checks: RefCell::new(Vec::new()),
645 deferred_generator_interiors: RefCell::new(Vec::new()),
646 opaque_types: RefCell::new(Default::default()),
647 implicit_region_bound,
652 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
653 debug!("register_predicate({:?})", obligation);
654 if obligation.has_escaping_bound_vars() {
655 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}",
660 .register_predicate_obligation(self, obligation);
663 fn register_predicates<I>(&self, obligations: I)
664 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>>
666 for obligation in obligations {
667 self.register_predicate(obligation);
671 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
672 self.register_predicates(infer_ok.obligations);
676 fn normalize_associated_types_in<T>(&self,
679 param_env: ty::ParamEnv<'tcx>,
681 where T : TypeFoldable<'tcx>
683 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
684 self.register_infer_ok_obligations(ok)
688 struct CheckItemTypesVisitor<'tcx> {
692 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
693 fn visit_item(&mut self, i: &'tcx hir::Item) {
694 check_item_type(self.tcx, i);
696 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
697 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
700 pub fn check_wf_new<'tcx>(tcx: TyCtxt<'tcx>) -> Result<(), ErrorReported> {
701 tcx.sess.track_errors(|| {
702 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
703 tcx.hir().krate().par_visit_all_item_likes(&mut visit);
707 fn check_mod_item_types<'tcx>(tcx: TyCtxt<'tcx>, module_def_id: DefId) {
708 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
711 fn typeck_item_bodies<'tcx>(tcx: TyCtxt<'tcx>, crate_num: CrateNum) {
712 debug_assert!(crate_num == LOCAL_CRATE);
713 tcx.par_body_owners(|body_owner_def_id| {
714 tcx.ensure().typeck_tables_of(body_owner_def_id);
718 fn check_item_well_formed<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) {
719 wfcheck::check_item_well_formed(tcx, def_id);
722 fn check_trait_item_well_formed<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) {
723 wfcheck::check_trait_item(tcx, def_id);
726 fn check_impl_item_well_formed<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) {
727 wfcheck::check_impl_item(tcx, def_id);
730 pub fn provide(providers: &mut Providers<'_>) {
731 method::provide(providers);
732 *providers = Providers {
738 check_item_well_formed,
739 check_trait_item_well_formed,
740 check_impl_item_well_formed,
741 check_mod_item_types,
746 fn adt_destructor<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<ty::Destructor> {
747 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
750 /// If this `DefId` is a "primary tables entry", returns `Some((body_id, decl))`
751 /// with information about it's body-id and fn-decl (if any). Otherwise,
754 /// If this function returns "some", then `typeck_tables(def_id)` will
755 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
756 /// may not succeed. In some cases where this function returns `None`
757 /// (notably closures), `typeck_tables(def_id)` would wind up
758 /// redirecting to the owning function.
759 fn primary_body_of<'tcx>(
762 ) -> Option<(hir::BodyId, Option<&'tcx hir::FnDecl>)> {
763 match tcx.hir().get_by_hir_id(id) {
764 Node::Item(item) => {
766 hir::ItemKind::Const(_, body) |
767 hir::ItemKind::Static(_, _, body) =>
769 hir::ItemKind::Fn(ref decl, .., body) =>
770 Some((body, Some(decl))),
775 Node::TraitItem(item) => {
777 hir::TraitItemKind::Const(_, Some(body)) =>
779 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
780 Some((body, Some(&sig.decl))),
785 Node::ImplItem(item) => {
787 hir::ImplItemKind::Const(_, body) =>
789 hir::ImplItemKind::Method(ref sig, body) =>
790 Some((body, Some(&sig.decl))),
795 Node::AnonConst(constant) => Some((constant.body, None)),
800 fn has_typeck_tables<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
801 // Closures' tables come from their outermost function,
802 // as they are part of the same "inference environment".
803 let outer_def_id = tcx.closure_base_def_id(def_id);
804 if outer_def_id != def_id {
805 return tcx.has_typeck_tables(outer_def_id);
808 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
809 primary_body_of(tcx, id).is_some()
812 fn used_trait_imports<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx DefIdSet {
813 &*tcx.typeck_tables_of(def_id).used_trait_imports
816 fn typeck_tables_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'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<'tcx>(tcx: TyCtxt<'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, 'tcx: 'a> {
924 fcx: &'a FnCtxt<'a, 'tcx>,
925 parent_id: hir::HirId,
928 impl<'a, 'tcx> GatherLocalsVisitor<'a, '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 {
934 kind: TypeVariableOriginKind::TypeInference,
937 self.fcx.locals.borrow_mut().insert(nid, LocalTy {
944 // take type that the user specified
945 self.fcx.locals.borrow_mut().insert(nid, typ);
952 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
953 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
954 NestedVisitorMap::None
957 // Add explicitly-declared locals.
958 fn visit_local(&mut self, local: &'tcx hir::Local) {
959 let local_ty = match local.ty {
961 let o_ty = self.fcx.to_ty(&ty);
963 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
964 self.fcx.instantiate_opaque_types_from_value(
972 let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(
973 &UserType::Ty(revealed_ty)
975 debug!("visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
976 ty.hir_id, o_ty, revealed_ty, c_ty);
977 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
979 Some(LocalTy { decl_ty: o_ty, revealed_ty })
983 self.assign(local.span, local.hir_id, local_ty);
985 debug!("Local variable {:?} is assigned type {}",
987 self.fcx.ty_to_string(
988 self.fcx.locals.borrow().get(&local.hir_id).unwrap().clone().decl_ty));
989 intravisit::walk_local(self, local);
992 // Add pattern bindings.
993 fn visit_pat(&mut self, p: &'tcx hir::Pat) {
994 if let PatKind::Binding(_, _, ident, _) = p.node {
995 let var_ty = self.assign(p.span, p.hir_id, None);
997 let node_id = self.fcx.tcx.hir().hir_to_node_id(p.hir_id);
998 if !self.fcx.tcx.features().unsized_locals {
999 self.fcx.require_type_is_sized(var_ty, p.span,
1000 traits::VariableType(node_id));
1003 debug!("Pattern binding {} is assigned to {} with type {:?}",
1005 self.fcx.ty_to_string(
1006 self.fcx.locals.borrow().get(&p.hir_id).unwrap().clone().decl_ty),
1009 intravisit::walk_pat(self, p);
1012 // Don't descend into the bodies of nested closures
1015 _: intravisit::FnKind<'tcx>,
1016 _: &'tcx hir::FnDecl,
1023 /// When `check_fn` is invoked on a generator (i.e., a body that
1024 /// includes yield), it returns back some information about the yield
1026 struct GeneratorTypes<'tcx> {
1027 /// Type of value that is yielded.
1030 /// Types that are captured (see `GeneratorInterior` for more).
1033 /// Indicates if the generator is movable or static (immovable).
1034 movability: hir::GeneratorMovability,
1037 /// Helper used for fns and closures. Does the grungy work of checking a function
1038 /// body and returns the function context used for that purpose, since in the case of a fn item
1039 /// there is still a bit more to do.
1042 /// * inherited: other fields inherited from the enclosing fn (if any)
1043 fn check_fn<'a, 'tcx>(
1044 inherited: &'a Inherited<'a, 'tcx>,
1045 param_env: ty::ParamEnv<'tcx>,
1046 fn_sig: ty::FnSig<'tcx>,
1047 decl: &'tcx hir::FnDecl,
1049 body: &'tcx hir::Body,
1050 can_be_generator: Option<hir::GeneratorMovability>,
1051 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
1052 let mut fn_sig = fn_sig.clone();
1054 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1056 // Create the function context. This is either derived from scratch or,
1057 // in the case of closures, based on the outer context.
1058 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1059 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1061 let declared_ret_ty = fn_sig.output();
1062 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1063 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(fn_id, &declared_ret_ty);
1064 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1065 fn_sig = fcx.tcx.mk_fn_sig(
1066 fn_sig.inputs().iter().cloned(),
1073 let span = body.value.span;
1075 if body.is_generator && can_be_generator.is_some() {
1076 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
1077 kind: TypeVariableOriginKind::TypeInference,
1080 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1081 fcx.yield_ty = Some(yield_ty);
1084 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id_from_hir_id(fn_id));
1085 let outer_hir_id = fcx.tcx.hir().as_local_hir_id(outer_def_id).unwrap();
1086 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id, }.visit_body(body);
1088 // Add formal parameters.
1089 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
1090 // Check the pattern.
1091 let binding_mode = ty::BindingMode::BindByValue(hir::Mutability::MutImmutable);
1092 fcx.check_pat_walk(&arg.pat, arg_ty, binding_mode, None);
1094 // Check that argument is Sized.
1095 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1096 // for simple cases like `fn foo(x: Trait)`,
1097 // where we would error once on the parameter as a whole, and once on the binding `x`.
1098 if arg.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1099 fcx.require_type_is_sized(arg_ty, decl.output.span(), traits::SizedArgumentType);
1102 fcx.write_ty(arg.hir_id, arg_ty);
1105 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1107 fcx.check_return_expr(&body.value);
1109 // We insert the deferred_generator_interiors entry after visiting the body.
1110 // This ensures that all nested generators appear before the entry of this generator.
1111 // resolve_generator_interiors relies on this property.
1112 let gen_ty = if can_be_generator.is_some() && body.is_generator {
1113 let interior = fcx.next_ty_var(TypeVariableOrigin {
1114 kind: TypeVariableOriginKind::MiscVariable,
1117 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior));
1118 Some(GeneratorTypes {
1119 yield_ty: fcx.yield_ty.unwrap(),
1121 movability: can_be_generator.unwrap(),
1127 // Finalize the return check by taking the LUB of the return types
1128 // we saw and assigning it to the expected return type. This isn't
1129 // really expected to fail, since the coercions would have failed
1130 // earlier when trying to find a LUB.
1132 // However, the behavior around `!` is sort of complex. In the
1133 // event that the `actual_return_ty` comes back as `!`, that
1134 // indicates that the fn either does not return or "returns" only
1135 // values of type `!`. In this case, if there is an expected
1136 // return type that is *not* `!`, that should be ok. But if the
1137 // return type is being inferred, we want to "fallback" to `!`:
1139 // let x = move || panic!();
1141 // To allow for that, I am creating a type variable with diverging
1142 // fallback. This was deemed ever so slightly better than unifying
1143 // the return value with `!` because it allows for the caller to
1144 // make more assumptions about the return type (e.g., they could do
1146 // let y: Option<u32> = Some(x());
1148 // which would then cause this return type to become `u32`, not
1150 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1151 let mut actual_return_ty = coercion.complete(&fcx);
1152 if actual_return_ty.is_never() {
1153 actual_return_ty = fcx.next_diverging_ty_var(
1154 TypeVariableOrigin {
1155 kind: TypeVariableOriginKind::DivergingFn,
1160 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1162 // Check that the main return type implements the termination trait.
1163 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1164 if let Some((def_id, EntryFnType::Main)) = fcx.tcx.entry_fn(LOCAL_CRATE) {
1165 let main_id = fcx.tcx.hir().as_local_hir_id(def_id).unwrap();
1166 if main_id == fn_id {
1167 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1168 let trait_ref = ty::TraitRef::new(term_id, substs);
1169 let return_ty_span = decl.output.span();
1170 let cause = traits::ObligationCause::new(
1171 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1173 inherited.register_predicate(
1174 traits::Obligation::new(
1175 cause, param_env, trait_ref.to_predicate()));
1180 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1181 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1182 if panic_impl_did == fcx.tcx.hir().local_def_id_from_hir_id(fn_id) {
1183 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1184 // at this point we don't care if there are duplicate handlers or if the handler has
1185 // the wrong signature as this value we'll be used when writing metadata and that
1186 // only happens if compilation succeeded
1187 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1189 if declared_ret_ty.sty != ty::Never {
1190 fcx.tcx.sess.span_err(
1192 "return type should be `!`",
1196 let inputs = fn_sig.inputs();
1197 let span = fcx.tcx.hir().span_by_hir_id(fn_id);
1198 if inputs.len() == 1 {
1199 let arg_is_panic_info = match inputs[0].sty {
1200 ty::Ref(region, ty, mutbl) => match ty.sty {
1201 ty::Adt(ref adt, _) => {
1202 adt.did == panic_info_did &&
1203 mutbl == hir::Mutability::MutImmutable &&
1204 *region != RegionKind::ReStatic
1211 if !arg_is_panic_info {
1212 fcx.tcx.sess.span_err(
1213 decl.inputs[0].span,
1214 "argument should be `&PanicInfo`",
1218 if let Node::Item(item) = fcx.tcx.hir().get_by_hir_id(fn_id) {
1219 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1220 if !generics.params.is_empty() {
1221 fcx.tcx.sess.span_err(
1223 "should have no type parameters",
1229 let span = fcx.tcx.sess.source_map().def_span(span);
1230 fcx.tcx.sess.span_err(span, "function should have one argument");
1233 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1238 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1239 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1240 if alloc_error_handler_did == fcx.tcx.hir().local_def_id_from_hir_id(fn_id) {
1241 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1242 if declared_ret_ty.sty != ty::Never {
1243 fcx.tcx.sess.span_err(
1245 "return type should be `!`",
1249 let inputs = fn_sig.inputs();
1250 let span = fcx.tcx.hir().span_by_hir_id(fn_id);
1251 if inputs.len() == 1 {
1252 let arg_is_alloc_layout = match inputs[0].sty {
1253 ty::Adt(ref adt, _) => {
1254 adt.did == alloc_layout_did
1259 if !arg_is_alloc_layout {
1260 fcx.tcx.sess.span_err(
1261 decl.inputs[0].span,
1262 "argument should be `Layout`",
1266 if let Node::Item(item) = fcx.tcx.hir().get_by_hir_id(fn_id) {
1267 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1268 if !generics.params.is_empty() {
1269 fcx.tcx.sess.span_err(
1271 "`#[alloc_error_handler]` function should have no type \
1278 let span = fcx.tcx.sess.source_map().def_span(span);
1279 fcx.tcx.sess.span_err(span, "function should have one argument");
1282 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1290 fn check_struct<'tcx>(tcx: TyCtxt<'tcx>, id: hir::HirId, span: Span) {
1291 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1292 let def = tcx.adt_def(def_id);
1293 def.destructor(tcx); // force the destructor to be evaluated
1294 check_representable(tcx, span, def_id);
1296 if def.repr.simd() {
1297 check_simd(tcx, span, def_id);
1300 check_transparent(tcx, span, def_id);
1301 check_packed(tcx, span, def_id);
1304 fn check_union<'tcx>(tcx: TyCtxt<'tcx>, id: hir::HirId, span: Span) {
1305 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1306 let def = tcx.adt_def(def_id);
1307 def.destructor(tcx); // force the destructor to be evaluated
1308 check_representable(tcx, span, def_id);
1309 check_transparent(tcx, span, def_id);
1310 check_packed(tcx, span, def_id);
1313 fn check_opaque<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, substs: SubstsRef<'tcx>, span: Span) {
1314 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1315 let mut err = struct_span_err!(
1316 tcx.sess, span, E0720,
1317 "opaque type expands to a recursive type",
1319 err.span_label(span, "expands to self-referential type");
1320 if let ty::Opaque(..) = partially_expanded_type.sty {
1321 err.note("type resolves to itself");
1323 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1329 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
1331 "check_item_type(it.hir_id={}, it.name={})",
1333 tcx.def_path_str(tcx.hir().local_def_id_from_hir_id(it.hir_id))
1335 let _indenter = indenter();
1337 // Consts can play a role in type-checking, so they are included here.
1338 hir::ItemKind::Static(..) => {
1339 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1340 tcx.typeck_tables_of(def_id);
1341 maybe_check_static_with_link_section(tcx, def_id, it.span);
1343 hir::ItemKind::Const(..) => {
1344 tcx.typeck_tables_of(tcx.hir().local_def_id_from_hir_id(it.hir_id));
1346 hir::ItemKind::Enum(ref enum_definition, _) => {
1347 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1349 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1350 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1351 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1352 let impl_def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1353 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1354 check_impl_items_against_trait(
1361 let trait_def_id = impl_trait_ref.def_id;
1362 check_on_unimplemented(tcx, trait_def_id, it);
1365 hir::ItemKind::Trait(..) => {
1366 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1367 check_on_unimplemented(tcx, def_id, it);
1369 hir::ItemKind::Struct(..) => {
1370 check_struct(tcx, it.hir_id, it.span);
1372 hir::ItemKind::Union(..) => {
1373 check_union(tcx, it.hir_id, it.span);
1375 hir::ItemKind::Existential(..) => {
1376 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1378 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1379 check_opaque(tcx, def_id, substs, it.span);
1381 hir::ItemKind::Ty(..) => {
1382 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1383 let pty_ty = tcx.type_of(def_id);
1384 let generics = tcx.generics_of(def_id);
1385 check_bounds_are_used(tcx, &generics, pty_ty);
1387 hir::ItemKind::ForeignMod(ref m) => {
1388 check_abi(tcx, it.span, m.abi);
1390 if m.abi == Abi::RustIntrinsic {
1391 for item in &m.items {
1392 intrinsic::check_intrinsic_type(tcx, item);
1394 } else if m.abi == Abi::PlatformIntrinsic {
1395 for item in &m.items {
1396 intrinsic::check_platform_intrinsic_type(tcx, item);
1399 for item in &m.items {
1400 let generics = tcx.generics_of(tcx.hir().local_def_id_from_hir_id(item.hir_id));
1401 if generics.params.len() - generics.own_counts().lifetimes != 0 {
1402 let mut err = struct_span_err!(
1406 "foreign items may not have type parameters"
1408 err.span_label(item.span, "can't have type parameters");
1409 // FIXME: once we start storing spans for type arguments, turn this into a
1412 "use specialization instead of type parameters by replacing them \
1413 with concrete types like `u32`",
1418 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.node {
1419 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1424 _ => { /* nothing to do */ }
1428 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1429 // Only restricted on wasm32 target for now
1430 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1434 // If `#[link_section]` is missing, then nothing to verify
1435 let attrs = tcx.codegen_fn_attrs(id);
1436 if attrs.link_section.is_none() {
1440 // For the wasm32 target statics with #[link_section] are placed into custom
1441 // sections of the final output file, but this isn't link custom sections of
1442 // other executable formats. Namely we can only embed a list of bytes,
1443 // nothing with pointers to anything else or relocations. If any relocation
1444 // show up, reject them here.
1445 let instance = ty::Instance::mono(tcx, id);
1446 let cid = GlobalId {
1450 let param_env = ty::ParamEnv::reveal_all();
1451 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1452 let alloc = if let ConstValue::ByRef(_, allocation) = static_.val {
1455 bug!("Matching on non-ByRef static")
1457 if alloc.relocations.len() != 0 {
1458 let msg = "statics with a custom `#[link_section]` must be a \
1459 simple list of bytes on the wasm target with no \
1460 extra levels of indirection such as references";
1461 tcx.sess.span_err(span, msg);
1466 fn check_on_unimplemented<'tcx>(tcx: TyCtxt<'tcx>, trait_def_id: DefId, item: &hir::Item) {
1467 let item_def_id = tcx.hir().local_def_id_from_hir_id(item.hir_id);
1468 // an error would be reported if this fails.
1469 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1472 fn report_forbidden_specialization<'tcx>(
1474 impl_item: &hir::ImplItem,
1477 let mut err = struct_span_err!(
1478 tcx.sess, impl_item.span, E0520,
1479 "`{}` specializes an item from a parent `impl`, but \
1480 that item is not marked `default`",
1482 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1485 match tcx.span_of_impl(parent_impl) {
1487 err.span_label(span, "parent `impl` is here");
1488 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1492 err.note(&format!("parent implementation is in crate `{}`", cname));
1499 fn check_specialization_validity<'tcx>(
1501 trait_def: &ty::TraitDef,
1502 trait_item: &ty::AssocItem,
1504 impl_item: &hir::ImplItem,
1506 let ancestors = trait_def.ancestors(tcx, impl_id);
1508 let kind = match impl_item.node {
1509 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1510 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1511 hir::ImplItemKind::Existential(..) => ty::AssocKind::Existential,
1512 hir::ImplItemKind::Type(_) => ty::AssocKind::Type
1515 let parent = ancestors.defs(tcx, trait_item.ident, kind, trait_def.def_id).nth(1)
1516 .map(|node_item| node_item.map(|parent| parent.defaultness));
1518 if let Some(parent) = parent {
1519 if tcx.impl_item_is_final(&parent) {
1520 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1526 fn check_impl_items_against_trait<'tcx>(
1530 impl_trait_ref: ty::TraitRef<'tcx>,
1531 impl_item_refs: &[hir::ImplItemRef],
1533 let impl_span = tcx.sess.source_map().def_span(impl_span);
1535 // If the trait reference itself is erroneous (so the compilation is going
1536 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1537 // isn't populated for such impls.
1538 if impl_trait_ref.references_error() { return; }
1540 // Locate trait definition and items
1541 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1542 let mut overridden_associated_type = None;
1544 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1546 // Check existing impl methods to see if they are both present in trait
1547 // and compatible with trait signature
1548 for impl_item in impl_items() {
1549 let ty_impl_item = tcx.associated_item(
1550 tcx.hir().local_def_id_from_hir_id(impl_item.hir_id));
1551 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1552 .find(|ac| Namespace::from(&impl_item.node) == Namespace::from(ac.kind) &&
1553 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1555 // Not compatible, but needed for the error message
1556 tcx.associated_items(impl_trait_ref.def_id)
1557 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1560 // Check that impl definition matches trait definition
1561 if let Some(ty_trait_item) = ty_trait_item {
1562 match impl_item.node {
1563 hir::ImplItemKind::Const(..) => {
1564 // Find associated const definition.
1565 if ty_trait_item.kind == ty::AssocKind::Const {
1566 compare_const_impl(tcx,
1572 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1573 "item `{}` is an associated const, \
1574 which doesn't match its trait `{}`",
1577 err.span_label(impl_item.span, "does not match trait");
1578 // We can only get the spans from local trait definition
1579 // Same for E0324 and E0325
1580 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1581 err.span_label(trait_span, "item in trait");
1586 hir::ImplItemKind::Method(..) => {
1587 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1588 if ty_trait_item.kind == ty::AssocKind::Method {
1589 compare_impl_method(tcx,
1596 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1597 "item `{}` is an associated method, \
1598 which doesn't match its trait `{}`",
1601 err.span_label(impl_item.span, "does not match trait");
1602 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1603 err.span_label(trait_span, "item in trait");
1608 hir::ImplItemKind::Existential(..) |
1609 hir::ImplItemKind::Type(_) => {
1610 if ty_trait_item.kind == ty::AssocKind::Type {
1611 if ty_trait_item.defaultness.has_value() {
1612 overridden_associated_type = Some(impl_item);
1615 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1616 "item `{}` is an associated type, \
1617 which doesn't match its trait `{}`",
1620 err.span_label(impl_item.span, "does not match trait");
1621 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1622 err.span_label(trait_span, "item in trait");
1629 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1633 // Check for missing items from trait
1634 let mut missing_items = Vec::new();
1635 let mut invalidated_items = Vec::new();
1636 let associated_type_overridden = overridden_associated_type.is_some();
1637 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1638 let is_implemented = trait_def.ancestors(tcx, impl_id)
1639 .defs(tcx, trait_item.ident, trait_item.kind, impl_trait_ref.def_id)
1641 .map(|node_item| !node_item.node.is_from_trait())
1644 if !is_implemented && !tcx.impl_is_default(impl_id) {
1645 if !trait_item.defaultness.has_value() {
1646 missing_items.push(trait_item);
1647 } else if associated_type_overridden {
1648 invalidated_items.push(trait_item.ident);
1653 if !missing_items.is_empty() {
1654 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1655 "not all trait items implemented, missing: `{}`",
1656 missing_items.iter()
1657 .map(|trait_item| trait_item.ident.to_string())
1658 .collect::<Vec<_>>().join("`, `"));
1659 err.span_label(impl_span, format!("missing `{}` in implementation",
1660 missing_items.iter()
1661 .map(|trait_item| trait_item.ident.to_string())
1662 .collect::<Vec<_>>().join("`, `")));
1663 for trait_item in missing_items {
1664 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1665 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1667 err.note_trait_signature(trait_item.ident.to_string(),
1668 trait_item.signature(tcx));
1674 if !invalidated_items.is_empty() {
1675 let invalidator = overridden_associated_type.unwrap();
1676 span_err!(tcx.sess, invalidator.span, E0399,
1677 "the following trait items need to be reimplemented \
1678 as `{}` was overridden: `{}`",
1680 invalidated_items.iter()
1681 .map(|name| name.to_string())
1682 .collect::<Vec<_>>().join("`, `"))
1686 /// Checks whether a type can be represented in memory. In particular, it
1687 /// identifies types that contain themselves without indirection through a
1688 /// pointer, which would mean their size is unbounded.
1689 fn check_representable<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, item_def_id: DefId) -> bool {
1690 let rty = tcx.type_of(item_def_id);
1692 // Check that it is possible to represent this type. This call identifies
1693 // (1) types that contain themselves and (2) types that contain a different
1694 // recursive type. It is only necessary to throw an error on those that
1695 // contain themselves. For case 2, there must be an inner type that will be
1696 // caught by case 1.
1697 match rty.is_representable(tcx, sp) {
1698 Representability::SelfRecursive(spans) => {
1699 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1701 err.span_label(span, "recursive without indirection");
1706 Representability::Representable | Representability::ContainsRecursive => (),
1711 pub fn check_simd<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, def_id: DefId) {
1712 let t = tcx.type_of(def_id);
1713 if let ty::Adt(def, substs) = t.sty {
1714 if def.is_struct() {
1715 let fields = &def.non_enum_variant().fields;
1716 if fields.is_empty() {
1717 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1720 let e = fields[0].ty(tcx, substs);
1721 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1722 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1723 .span_label(sp, "SIMD elements must have the same type")
1728 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1729 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1731 span_err!(tcx.sess, sp, E0077,
1732 "SIMD vector element type should be machine type");
1740 fn check_packed<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, def_id: DefId) {
1741 let repr = tcx.adt_def(def_id).repr;
1743 for attr in tcx.get_attrs(def_id).iter() {
1744 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
1745 if let attr::ReprPacked(pack) = r {
1746 if pack != repr.pack {
1747 struct_span_err!(tcx.sess, sp, E0634,
1748 "type has conflicting packed representation hints").emit();
1754 struct_span_err!(tcx.sess, sp, E0587,
1755 "type has conflicting packed and align representation hints").emit();
1757 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1758 struct_span_err!(tcx.sess, sp, E0588,
1759 "packed type cannot transitively contain a `[repr(align)]` type").emit();
1764 fn check_packed_inner<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, stack: &mut Vec<DefId>) -> bool {
1765 let t = tcx.type_of(def_id);
1766 if stack.contains(&def_id) {
1767 debug!("check_packed_inner: {:?} is recursive", t);
1770 if let ty::Adt(def, substs) = t.sty {
1771 if def.is_struct() || def.is_union() {
1772 if tcx.adt_def(def.did).repr.align > 0 {
1775 // push struct def_id before checking fields
1777 for field in &def.non_enum_variant().fields {
1778 let f = field.ty(tcx, substs);
1779 if let ty::Adt(def, _) = f.sty {
1780 if check_packed_inner(tcx, def.did, stack) {
1785 // only need to pop if not early out
1792 fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, def_id: DefId) {
1793 let adt = tcx.adt_def(def_id);
1794 if !adt.repr.transparent() {
1799 if !tcx.features().transparent_enums {
1800 emit_feature_err(&tcx.sess.parse_sess,
1801 sym::transparent_enums,
1803 GateIssue::Language,
1804 "transparent enums are unstable");
1806 if adt.variants.len() != 1 {
1807 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
1808 tcx.hir().span_if_local(variant.def_id).unwrap()
1810 let mut err = struct_span_err!(tcx.sess, sp, E0731,
1811 "transparent enum needs exactly one variant, but has {}",
1812 adt.variants.len());
1813 if !variant_spans.is_empty() {
1814 err.span_note(variant_spans, &format!("the following variants exist on `{}`",
1815 tcx.def_path_str(def_id)));
1818 if adt.variants.is_empty() {
1819 // Don't bother checking the fields. No variants (and thus no fields) exist.
1825 if adt.is_union() && !tcx.features().transparent_unions {
1826 emit_feature_err(&tcx.sess.parse_sess,
1827 sym::transparent_unions,
1829 GateIssue::Language,
1830 "transparent unions are unstable");
1833 // For each field, figure out if it's known to be a ZST and align(1)
1834 let field_infos = adt.all_fields().map(|field| {
1835 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
1836 let param_env = tcx.param_env(field.did);
1837 let layout = tcx.layout_of(param_env.and(ty));
1838 // We are currently checking the type this field came from, so it must be local
1839 let span = tcx.hir().span_if_local(field.did).unwrap();
1840 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
1841 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
1845 let non_zst_fields = field_infos.clone().filter(|(_span, zst, _align1)| !*zst);
1846 let non_zst_count = non_zst_fields.clone().count();
1847 if non_zst_count != 1 {
1848 let field_spans: Vec<_> = non_zst_fields.map(|(span, _zst, _align1)| span).collect();
1850 let mut err = struct_span_err!(tcx.sess, sp, E0690,
1851 "{}transparent {} needs exactly one non-zero-sized field, but has {}",
1852 if adt.is_enum() { "the variant of a " } else { "" },
1855 if !field_spans.is_empty() {
1856 err.span_note(field_spans,
1857 &format!("the following non-zero-sized fields exist on `{}`:",
1858 tcx.def_path_str(def_id)));
1862 for (span, zst, align1) in field_infos {
1864 span_err!(tcx.sess, span, E0691,
1865 "zero-sized field in transparent {} has alignment larger than 1",
1871 #[allow(trivial_numeric_casts)]
1872 pub fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, vs: &'tcx [hir::Variant], id: hir::HirId) {
1873 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1874 let def = tcx.adt_def(def_id);
1875 def.destructor(tcx); // force the destructor to be evaluated
1878 let attributes = tcx.get_attrs(def_id);
1879 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
1881 tcx.sess, attr.span, E0084,
1882 "unsupported representation for zero-variant enum")
1883 .span_label(sp, "zero-variant enum")
1888 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1889 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1890 if !tcx.features().repr128 {
1891 emit_feature_err(&tcx.sess.parse_sess,
1894 GateIssue::Language,
1895 "repr with 128-bit type is unstable");
1900 if let Some(ref e) = v.node.disr_expr {
1901 tcx.typeck_tables_of(tcx.hir().local_def_id_from_hir_id(e.hir_id));
1905 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
1906 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
1907 // Check for duplicate discriminant values
1908 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
1909 let variant_did = def.variants[VariantIdx::new(i)].def_id;
1910 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
1911 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
1912 let i_span = match variant_i.node.disr_expr {
1913 Some(ref expr) => tcx.hir().span_by_hir_id(expr.hir_id),
1914 None => tcx.hir().span_by_hir_id(variant_i_hir_id)
1916 let span = match v.node.disr_expr {
1917 Some(ref expr) => tcx.hir().span_by_hir_id(expr.hir_id),
1920 struct_span_err!(tcx.sess, span, E0081,
1921 "discriminant value `{}` already exists", disr_vals[i])
1922 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1923 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
1926 disr_vals.push(discr);
1929 check_representable(tcx, sp, def_id);
1930 check_transparent(tcx, sp, def_id);
1933 fn report_unexpected_variant_res<'tcx>(tcx: TyCtxt<'tcx>, res: Res, span: Span, qpath: &QPath) {
1934 span_err!(tcx.sess, span, E0533,
1935 "expected unit struct/variant or constant, found {} `{}`",
1937 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
1940 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
1941 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1945 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1946 -> &'tcx ty::GenericPredicates<'tcx>
1949 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1950 let item_id = tcx.hir().ty_param_owner(hir_id);
1951 let item_def_id = tcx.hir().local_def_id_from_hir_id(item_id);
1952 let generics = tcx.generics_of(item_def_id);
1953 let index = generics.param_def_id_to_index[&def_id];
1954 tcx.arena.alloc(ty::GenericPredicates {
1956 predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
1958 ty::Predicate::Trait(ref data)
1959 if data.skip_binder().self_ty().is_param(index) => {
1960 // HACK(eddyb) should get the original `Span`.
1961 let span = tcx.def_span(def_id);
1962 Some((predicate, span))
1972 def: Option<&ty::GenericParamDef>,
1974 ) -> Option<ty::Region<'tcx>> {
1976 Some(def) => infer::EarlyBoundRegion(span, def.name),
1977 None => infer::MiscVariable(span)
1979 Some(self.next_region_var(v))
1982 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
1983 if let Some(param) = param {
1984 if let UnpackedKind::Type(ty) = self.var_for_def(span, param).unpack() {
1989 self.next_ty_var(TypeVariableOrigin {
1990 kind: TypeVariableOriginKind::TypeInference,
1999 param: Option<&ty::GenericParamDef>,
2001 ) -> &'tcx Const<'tcx> {
2002 if let Some(param) = param {
2003 if let UnpackedKind::Const(ct) = self.var_for_def(span, param).unpack() {
2008 self.next_const_var(ty, ConstVariableOrigin {
2009 kind: ConstVariableOriginKind::ConstInference,
2015 fn projected_ty_from_poly_trait_ref(&self,
2018 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2021 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2023 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2027 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2030 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2031 if ty.has_escaping_bound_vars() {
2032 ty // FIXME: normalization and escaping regions
2034 self.normalize_associated_types_in(span, &ty)
2038 fn set_tainted_by_errors(&self) {
2039 self.infcx.set_tainted_by_errors()
2042 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2043 self.write_ty(hir_id, ty)
2047 /// Controls whether the arguments are tupled. This is used for the call
2050 /// Tupling means that all call-side arguments are packed into a tuple and
2051 /// passed as a single parameter. For example, if tupling is enabled, this
2054 /// fn f(x: (isize, isize))
2056 /// Can be called as:
2063 #[derive(Clone, Eq, PartialEq)]
2064 enum TupleArgumentsFlag {
2069 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2071 inh: &'a Inherited<'a, 'tcx>,
2072 param_env: ty::ParamEnv<'tcx>,
2073 body_id: hir::HirId,
2074 ) -> FnCtxt<'a, 'tcx> {
2078 err_count_on_creation: inh.tcx.sess.err_count(),
2080 ret_coercion_span: RefCell::new(None),
2082 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2083 hir::CRATE_HIR_ID)),
2084 diverges: Cell::new(Diverges::Maybe),
2085 has_errors: Cell::new(false),
2086 enclosing_breakables: RefCell::new(EnclosingBreakables {
2088 by_id: Default::default(),
2094 pub fn sess(&self) -> &Session {
2098 pub fn err_count_since_creation(&self) -> usize {
2099 self.tcx.sess.err_count() - self.err_count_on_creation
2102 /// Produces warning on the given node, if the current point in the
2103 /// function is unreachable, and there hasn't been another warning.
2104 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2105 if self.diverges.get() == Diverges::Always &&
2106 // If span arose from a desugaring of `if` then it is the condition itself,
2107 // which diverges, that we are about to lint on. This gives suboptimal diagnostics
2108 // and so we stop here and allow the block of the `if`-expression to be linted instead.
2109 !span.is_compiler_desugaring(CompilerDesugaringKind::IfTemporary) {
2110 self.diverges.set(Diverges::WarnedAlways);
2112 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2114 let msg = format!("unreachable {}", kind);
2115 self.tcx().lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg);
2121 code: ObligationCauseCode<'tcx>)
2122 -> ObligationCause<'tcx> {
2123 ObligationCause::new(span, self.body_id, code)
2126 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2127 self.cause(span, ObligationCauseCode::MiscObligation)
2130 /// Resolves type variables in `ty` if possible. Unlike the infcx
2131 /// version (resolve_vars_if_possible), this version will
2132 /// also select obligations if it seems useful, in an effort
2133 /// to get more type information.
2134 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2135 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2137 // No Infer()? Nothing needs doing.
2138 if !ty.has_infer_types() {
2139 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2143 // If `ty` is a type variable, see whether we already know what it is.
2144 ty = self.resolve_vars_if_possible(&ty);
2145 if !ty.has_infer_types() {
2146 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2150 // If not, try resolving pending obligations as much as
2151 // possible. This can help substantially when there are
2152 // indirect dependencies that don't seem worth tracking
2154 self.select_obligations_where_possible(false);
2155 ty = self.resolve_vars_if_possible(&ty);
2157 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2161 fn record_deferred_call_resolution(
2163 closure_def_id: DefId,
2164 r: DeferredCallResolution<'tcx>,
2166 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2167 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2170 fn remove_deferred_call_resolutions(
2172 closure_def_id: DefId,
2173 ) -> Vec<DeferredCallResolution<'tcx>> {
2174 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2175 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2178 pub fn tag(&self) -> String {
2179 format!("{:p}", self)
2182 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2183 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2184 span_bug!(span, "no type for local variable {}",
2185 self.tcx.hir().hir_to_string(nid))
2190 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2191 debug!("write_ty({:?}, {:?}) in fcx {}",
2192 id, self.resolve_vars_if_possible(&ty), self.tag());
2193 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2195 if ty.references_error() {
2196 self.has_errors.set(true);
2197 self.set_tainted_by_errors();
2201 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2202 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2205 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2206 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2209 pub fn write_method_call(&self,
2211 method: MethodCallee<'tcx>) {
2212 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2213 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2214 self.write_substs(hir_id, method.substs);
2216 // When the method is confirmed, the `method.substs` includes
2217 // parameters from not just the method, but also the impl of
2218 // the method -- in particular, the `Self` type will be fully
2219 // resolved. However, those are not something that the "user
2220 // specified" -- i.e., those types come from the inferred type
2221 // of the receiver, not something the user wrote. So when we
2222 // create the user-substs, we want to replace those earlier
2223 // types with just the types that the user actually wrote --
2224 // that is, those that appear on the *method itself*.
2226 // As an example, if the user wrote something like
2227 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2228 // type of `foo` (possibly adjusted), but we don't want to
2229 // include that. We want just the `[_, u32]` part.
2230 if !method.substs.is_noop() {
2231 let method_generics = self.tcx.generics_of(method.def_id);
2232 if !method_generics.params.is_empty() {
2233 let user_type_annotation = self.infcx.probe(|_| {
2234 let user_substs = UserSubsts {
2235 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2236 let i = param.index as usize;
2237 if i < method_generics.parent_count {
2238 self.infcx.var_for_def(DUMMY_SP, param)
2243 user_self_ty: None, // not relevant here
2246 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2252 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2253 self.write_user_type_annotation(hir_id, user_type_annotation);
2258 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2259 if !substs.is_noop() {
2260 debug!("write_substs({:?}, {:?}) in fcx {}",
2265 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2269 /// Given the substs that we just converted from the HIR, try to
2270 /// canonicalize them and store them as user-given substitutions
2271 /// (i.e., substitutions that must be respected by the NLL check).
2273 /// This should be invoked **before any unifications have
2274 /// occurred**, so that annotations like `Vec<_>` are preserved
2276 pub fn write_user_type_annotation_from_substs(
2280 substs: SubstsRef<'tcx>,
2281 user_self_ty: Option<UserSelfTy<'tcx>>,
2284 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2285 user_self_ty={:?} in fcx {}",
2286 hir_id, def_id, substs, user_self_ty, self.tag(),
2289 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2290 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2291 &UserType::TypeOf(def_id, UserSubsts {
2296 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2297 self.write_user_type_annotation(hir_id, canonicalized);
2301 pub fn write_user_type_annotation(
2304 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2307 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2308 hir_id, canonical_user_type_annotation, self.tag(),
2311 if !canonical_user_type_annotation.is_identity() {
2312 self.tables.borrow_mut().user_provided_types_mut().insert(
2313 hir_id, canonical_user_type_annotation
2316 debug!("write_user_type_annotation: skipping identity substs");
2320 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2321 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2327 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2328 Entry::Vacant(entry) => { entry.insert(adj); },
2329 Entry::Occupied(mut entry) => {
2330 debug!(" - composing on top of {:?}", entry.get());
2331 match (&entry.get()[..], &adj[..]) {
2332 // Applying any adjustment on top of a NeverToAny
2333 // is a valid NeverToAny adjustment, because it can't
2335 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2337 Adjustment { kind: Adjust::Deref(_), .. },
2338 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2340 Adjustment { kind: Adjust::Deref(_), .. },
2341 .. // Any following adjustments are allowed.
2343 // A reborrow has no effect before a dereference.
2345 // FIXME: currently we never try to compose autoderefs
2346 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2348 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2349 expr, entry.get(), adj)
2351 *entry.get_mut() = adj;
2356 /// Basically whenever we are converting from a type scheme into
2357 /// the fn body space, we always want to normalize associated
2358 /// types as well. This function combines the two.
2359 fn instantiate_type_scheme<T>(&self,
2361 substs: SubstsRef<'tcx>,
2364 where T : TypeFoldable<'tcx>
2366 let value = value.subst(self.tcx, substs);
2367 let result = self.normalize_associated_types_in(span, &value);
2368 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2375 /// As `instantiate_type_scheme`, but for the bounds found in a
2376 /// generic type scheme.
2377 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: SubstsRef<'tcx>)
2378 -> ty::InstantiatedPredicates<'tcx> {
2379 let bounds = self.tcx.predicates_of(def_id);
2380 let result = bounds.instantiate(self.tcx, substs);
2381 let result = self.normalize_associated_types_in(span, &result);
2382 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
2389 /// Replaces the opaque types from the given value with type variables,
2390 /// and records the `OpaqueTypeMap` for later use during writeback. See
2391 /// `InferCtxt::instantiate_opaque_types` for more details.
2392 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2394 parent_id: hir::HirId,
2397 let parent_def_id = self.tcx.hir().local_def_id_from_hir_id(parent_id);
2398 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2402 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2403 self.instantiate_opaque_types(
2411 let mut opaque_types = self.opaque_types.borrow_mut();
2412 for (ty, decl) in opaque_type_map {
2413 let old_value = opaque_types.insert(ty, decl);
2414 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2420 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2421 where T : TypeFoldable<'tcx>
2423 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2426 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2428 where T : TypeFoldable<'tcx>
2430 self.inh.partially_normalize_associated_types_in(span,
2436 pub fn require_type_meets(&self,
2439 code: traits::ObligationCauseCode<'tcx>,
2442 self.register_bound(
2445 traits::ObligationCause::new(span, self.body_id, code));
2448 pub fn require_type_is_sized(&self,
2451 code: traits::ObligationCauseCode<'tcx>)
2453 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
2454 self.require_type_meets(ty, span, code, lang_item);
2457 pub fn require_type_is_sized_deferred(&self,
2460 code: traits::ObligationCauseCode<'tcx>)
2462 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2465 pub fn register_bound(&self,
2468 cause: traits::ObligationCause<'tcx>)
2470 self.fulfillment_cx.borrow_mut()
2471 .register_bound(self, self.param_env, ty, def_id, cause);
2474 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2475 let t = AstConv::ast_ty_to_ty(self, ast_t);
2476 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2480 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2481 let ty = self.to_ty(ast_ty);
2482 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2484 if Self::can_contain_user_lifetime_bounds(ty) {
2485 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2486 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2487 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2493 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2494 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2495 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2498 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2499 AstConv::ast_const_to_const(self, ast_c, ty)
2502 // If the type given by the user has free regions, save it for later, since
2503 // NLL would like to enforce those. Also pass in types that involve
2504 // projections, since those can resolve to `'static` bounds (modulo #54940,
2505 // which hopefully will be fixed by the time you see this comment, dear
2506 // reader, although I have my doubts). Also pass in types with inference
2507 // types, because they may be repeated. Other sorts of things are already
2508 // sufficiently enforced with erased regions. =)
2509 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2511 T: TypeFoldable<'tcx>
2513 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2516 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2517 match self.tables.borrow().node_types().get(id) {
2519 None if self.is_tainted_by_errors() => self.tcx.types.err,
2521 let node_id = self.tcx.hir().hir_to_node_id(id);
2522 bug!("no type for node {}: {} in fcx {}",
2523 node_id, self.tcx.hir().node_to_string(node_id),
2529 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2530 /// outlive the region `r`.
2531 pub fn register_wf_obligation(&self,
2534 code: traits::ObligationCauseCode<'tcx>)
2536 // WF obligations never themselves fail, so no real need to give a detailed cause:
2537 let cause = traits::ObligationCause::new(span, self.body_id, code);
2538 self.register_predicate(traits::Obligation::new(cause,
2540 ty::Predicate::WellFormed(ty)));
2543 /// Registers obligations that all types appearing in `substs` are well-formed.
2544 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2545 for ty in substs.types() {
2546 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2550 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2551 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2552 /// trait/region obligations.
2554 /// For example, if there is a function:
2557 /// fn foo<'a,T:'a>(...)
2560 /// and a reference:
2566 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2567 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2568 pub fn add_obligations_for_parameters(&self,
2569 cause: traits::ObligationCause<'tcx>,
2570 predicates: &ty::InstantiatedPredicates<'tcx>)
2572 assert!(!predicates.has_escaping_bound_vars());
2574 debug!("add_obligations_for_parameters(predicates={:?})",
2577 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2578 self.register_predicate(obligation);
2582 // FIXME(arielb1): use this instead of field.ty everywhere
2583 // Only for fields! Returns <none> for methods>
2584 // Indifferent to privacy flags
2585 pub fn field_ty(&self,
2587 field: &'tcx ty::FieldDef,
2588 substs: SubstsRef<'tcx>)
2591 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2594 fn check_casts(&self) {
2595 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2596 for cast in deferred_cast_checks.drain(..) {
2601 fn resolve_generator_interiors(&self, def_id: DefId) {
2602 let mut generators = self.deferred_generator_interiors.borrow_mut();
2603 for (body_id, interior) in generators.drain(..) {
2604 self.select_obligations_where_possible(false);
2605 generator_interior::resolve_interior(self, def_id, body_id, interior);
2609 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2610 // Non-numerics get replaced with ! or () (depending on whether
2611 // feature(never_type) is enabled, unconstrained ints with i32,
2612 // unconstrained floats with f64.
2613 // Fallback becomes very dubious if we have encountered type-checking errors.
2614 // In that case, fallback to Error.
2615 // The return value indicates whether fallback has occurred.
2616 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2617 use rustc::ty::error::UnconstrainedNumeric::Neither;
2618 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2620 assert!(ty.is_ty_infer());
2621 let fallback = match self.type_is_unconstrained_numeric(ty) {
2622 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2623 UnconstrainedInt => self.tcx.types.i32,
2624 UnconstrainedFloat => self.tcx.types.f64,
2625 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2626 Neither => return false,
2628 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2629 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2633 fn select_all_obligations_or_error(&self) {
2634 debug!("select_all_obligations_or_error");
2635 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2636 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2640 /// Select as many obligations as we can at present.
2641 fn select_obligations_where_possible(&self, fallback_has_occurred: bool) {
2642 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2643 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2647 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2648 /// returns a type of `&T`, but the actual type we assign to the
2649 /// *expression* is `T`. So this function just peels off the return
2650 /// type by one layer to yield `T`.
2651 fn make_overloaded_place_return_type(&self,
2652 method: MethodCallee<'tcx>)
2653 -> ty::TypeAndMut<'tcx>
2655 // extract method return type, which will be &T;
2656 let ret_ty = method.sig.output();
2658 // method returns &T, but the type as visible to user is T, so deref
2659 ret_ty.builtin_deref(true).unwrap()
2665 base_expr: &'tcx hir::Expr,
2669 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2670 // FIXME(#18741) -- this is almost but not quite the same as the
2671 // autoderef that normal method probing does. They could likely be
2674 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2675 let mut result = None;
2676 while result.is_none() && autoderef.next().is_some() {
2677 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2679 autoderef.finalize(self);
2683 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2684 /// (and otherwise adjust) `base_expr`, looking for a type which either
2685 /// supports builtin indexing or overloaded indexing.
2686 /// This loop implements one step in that search; the autoderef loop
2687 /// is implemented by `lookup_indexing`.
2691 base_expr: &hir::Expr,
2692 autoderef: &Autoderef<'a, 'tcx>,
2695 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2696 let adjusted_ty = autoderef.unambiguous_final_ty(self);
2697 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2704 for &unsize in &[false, true] {
2705 let mut self_ty = adjusted_ty;
2707 // We only unsize arrays here.
2708 if let ty::Array(element_ty, _) = adjusted_ty.sty {
2709 self_ty = self.tcx.mk_slice(element_ty);
2715 // If some lookup succeeds, write callee into table and extract index/element
2716 // type from the method signature.
2717 // If some lookup succeeded, install method in table
2718 let input_ty = self.next_ty_var(TypeVariableOrigin {
2719 kind: TypeVariableOriginKind::AutoDeref,
2720 span: base_expr.span,
2722 let method = self.try_overloaded_place_op(
2723 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
2725 let result = method.map(|ok| {
2726 debug!("try_index_step: success, using overloaded indexing");
2727 let method = self.register_infer_ok_obligations(ok);
2729 let mut adjustments = autoderef.adjust_steps(self, needs);
2730 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].sty {
2731 let mutbl = match r_mutbl {
2732 hir::MutImmutable => AutoBorrowMutability::Immutable,
2733 hir::MutMutable => AutoBorrowMutability::Mutable {
2734 // Indexing can be desugared to a method call,
2735 // so maybe we could use two-phase here.
2736 // See the documentation of AllowTwoPhase for why that's
2737 // not the case today.
2738 allow_two_phase_borrow: AllowTwoPhase::No,
2741 adjustments.push(Adjustment {
2742 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
2743 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2750 adjustments.push(Adjustment {
2751 kind: Adjust::Pointer(PointerCast::Unsize),
2752 target: method.sig.inputs()[0]
2755 self.apply_adjustments(base_expr, adjustments);
2757 self.write_method_call(expr.hir_id, method);
2758 (input_ty, self.make_overloaded_place_return_type(method).ty)
2760 if result.is_some() {
2768 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
2769 let (tr, name) = match (op, is_mut) {
2770 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
2771 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
2772 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
2773 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
2775 (tr, ast::Ident::with_empty_ctxt(name))
2778 fn try_overloaded_place_op(&self,
2781 arg_tys: &[Ty<'tcx>],
2784 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
2786 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
2792 // Try Mut first, if needed.
2793 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
2794 let method = match (needs, mut_tr) {
2795 (Needs::MutPlace, Some(trait_did)) => {
2796 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
2801 // Otherwise, fall back to the immutable version.
2802 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
2803 let method = match (method, imm_tr) {
2804 (None, Some(trait_did)) => {
2805 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
2807 (method, _) => method,
2813 fn check_method_argument_types(
2817 method: Result<MethodCallee<'tcx>, ()>,
2818 args_no_rcvr: &'tcx [hir::Expr],
2819 tuple_arguments: TupleArgumentsFlag,
2820 expected: Expectation<'tcx>,
2822 let has_error = match method {
2824 method.substs.references_error() || method.sig.references_error()
2829 let err_inputs = self.err_args(args_no_rcvr.len());
2831 let err_inputs = match tuple_arguments {
2832 DontTupleArguments => err_inputs,
2833 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
2836 self.check_argument_types(sp, expr_sp, &err_inputs[..], &[], args_no_rcvr,
2837 false, tuple_arguments, None);
2838 return self.tcx.types.err;
2841 let method = method.unwrap();
2842 // HACK(eddyb) ignore self in the definition (see above).
2843 let expected_arg_tys = self.expected_inputs_for_expected_output(
2846 method.sig.output(),
2847 &method.sig.inputs()[1..]
2849 self.check_argument_types(sp, expr_sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2850 args_no_rcvr, method.sig.c_variadic, tuple_arguments,
2851 self.tcx.hir().span_if_local(method.def_id));
2855 fn self_type_matches_expected_vid(
2857 trait_ref: ty::PolyTraitRef<'tcx>,
2858 expected_vid: ty::TyVid,
2860 let self_ty = self.shallow_resolve(trait_ref.self_ty());
2862 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
2863 trait_ref, self_ty, expected_vid
2866 ty::Infer(ty::TyVar(found_vid)) => {
2867 // FIXME: consider using `sub_root_var` here so we
2868 // can see through subtyping.
2869 let found_vid = self.root_var(found_vid);
2870 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
2871 expected_vid == found_vid
2877 fn obligations_for_self_ty<'b>(
2880 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
2883 // FIXME: consider using `sub_root_var` here so we
2884 // can see through subtyping.
2885 let ty_var_root = self.root_var(self_ty);
2886 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
2887 self_ty, ty_var_root,
2888 self.fulfillment_cx.borrow().pending_obligations());
2892 .pending_obligations()
2894 .filter_map(move |obligation| match obligation.predicate {
2895 ty::Predicate::Projection(ref data) =>
2896 Some((data.to_poly_trait_ref(self.tcx), obligation)),
2897 ty::Predicate::Trait(ref data) =>
2898 Some((data.to_poly_trait_ref(), obligation)),
2899 ty::Predicate::Subtype(..) => None,
2900 ty::Predicate::RegionOutlives(..) => None,
2901 ty::Predicate::TypeOutlives(..) => None,
2902 ty::Predicate::WellFormed(..) => None,
2903 ty::Predicate::ObjectSafe(..) => None,
2904 ty::Predicate::ConstEvaluatable(..) => None,
2905 // N.B., this predicate is created by breaking down a
2906 // `ClosureType: FnFoo()` predicate, where
2907 // `ClosureType` represents some `Closure`. It can't
2908 // possibly be referring to the current closure,
2909 // because we haven't produced the `Closure` for
2910 // this closure yet; this is exactly why the other
2911 // code is looking for a self type of a unresolved
2912 // inference variable.
2913 ty::Predicate::ClosureKind(..) => None,
2914 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
2917 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
2918 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
2919 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
2923 /// Generic function that factors out common logic from function calls,
2924 /// method calls and overloaded operators.
2925 fn check_argument_types(
2929 fn_inputs: &[Ty<'tcx>],
2930 expected_arg_tys: &[Ty<'tcx>],
2931 args: &'tcx [hir::Expr],
2933 tuple_arguments: TupleArgumentsFlag,
2934 def_span: Option<Span>,
2938 // Grab the argument types, supplying fresh type variables
2939 // if the wrong number of arguments were supplied
2940 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2946 // All the input types from the fn signature must outlive the call
2947 // so as to validate implied bounds.
2948 for &fn_input_ty in fn_inputs {
2949 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2952 let expected_arg_count = fn_inputs.len();
2954 let param_count_error = |expected_count: usize,
2959 let mut err = tcx.sess.struct_span_err_with_code(sp,
2960 &format!("this function takes {}{} but {} {} supplied",
2961 if c_variadic { "at least " } else { "" },
2962 potentially_plural_count(expected_count, "parameter"),
2963 potentially_plural_count(arg_count, "parameter"),
2964 if arg_count == 1 {"was"} else {"were"}),
2965 DiagnosticId::Error(error_code.to_owned()));
2967 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
2968 err.span_label(def_s, "defined here");
2971 let sugg_span = tcx.sess.source_map().end_point(expr_sp);
2972 // remove closing `)` from the span
2973 let sugg_span = sugg_span.shrink_to_lo();
2974 err.span_suggestion(
2976 "expected the unit value `()`; create it with empty parentheses",
2978 Applicability::MachineApplicable);
2980 err.span_label(sp, format!("expected {}{}",
2981 if c_variadic { "at least " } else { "" },
2982 potentially_plural_count(expected_count, "parameter")));
2987 let mut expected_arg_tys = expected_arg_tys.to_vec();
2989 let formal_tys = if tuple_arguments == TupleArguments {
2990 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2991 match tuple_type.sty {
2992 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
2993 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
2994 expected_arg_tys = vec![];
2995 self.err_args(args.len())
2997 ty::Tuple(arg_types) => {
2998 expected_arg_tys = match expected_arg_tys.get(0) {
2999 Some(&ty) => match ty.sty {
3000 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3005 arg_types.iter().map(|k| k.expect_ty()).collect()
3008 span_err!(tcx.sess, sp, E0059,
3009 "cannot use call notation; the first type parameter \
3010 for the function trait is neither a tuple nor unit");
3011 expected_arg_tys = vec![];
3012 self.err_args(args.len())
3015 } else if expected_arg_count == supplied_arg_count {
3017 } else if c_variadic {
3018 if supplied_arg_count >= expected_arg_count {
3021 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3022 expected_arg_tys = vec![];
3023 self.err_args(supplied_arg_count)
3026 // is the missing argument of type `()`?
3027 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3028 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3029 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3030 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3034 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3036 expected_arg_tys = vec![];
3037 self.err_args(supplied_arg_count)
3040 debug!("check_argument_types: formal_tys={:?}",
3041 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3043 // If there is no expectation, expect formal_tys.
3044 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3050 // Check the arguments.
3051 // We do this in a pretty awful way: first we type-check any arguments
3052 // that are not closures, then we type-check the closures. This is so
3053 // that we have more information about the types of arguments when we
3054 // type-check the functions. This isn't really the right way to do this.
3055 for &check_closures in &[false, true] {
3056 debug!("check_closures={}", check_closures);
3058 // More awful hacks: before we check argument types, try to do
3059 // an "opportunistic" vtable resolution of any trait bounds on
3060 // the call. This helps coercions.
3062 self.select_obligations_where_possible(false);
3065 // For C-variadic functions, we don't have a declared type for all of
3066 // the arguments hence we only do our usual type checking with
3067 // the arguments who's types we do know.
3068 let t = if c_variadic {
3070 } else if tuple_arguments == TupleArguments {
3075 for (i, arg) in args.iter().take(t).enumerate() {
3076 // Warn only for the first loop (the "no closures" one).
3077 // Closure arguments themselves can't be diverging, but
3078 // a previous argument can, e.g., `foo(panic!(), || {})`.
3079 if !check_closures {
3080 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3083 let is_closure = match arg.node {
3084 ExprKind::Closure(..) => true,
3088 if is_closure != check_closures {
3092 debug!("checking the argument");
3093 let formal_ty = formal_tys[i];
3095 // The special-cased logic below has three functions:
3096 // 1. Provide as good of an expected type as possible.
3097 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3099 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3101 // 2. Coerce to the most detailed type that could be coerced
3102 // to, which is `expected_ty` if `rvalue_hint` returns an
3103 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3104 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3105 // We're processing function arguments so we definitely want to use
3106 // two-phase borrows.
3107 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3109 // 3. Relate the expected type and the formal one,
3110 // if the expected type was used for the coercion.
3111 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3115 // We also need to make sure we at least write the ty of the other
3116 // arguments which we skipped above.
3118 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3119 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3120 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3123 for arg in args.iter().skip(expected_arg_count) {
3124 let arg_ty = self.check_expr(&arg);
3126 // There are a few types which get autopromoted when passed via varargs
3127 // in C but we just error out instead and require explicit casts.
3128 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3130 ty::Float(ast::FloatTy::F32) => {
3131 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3133 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3134 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3136 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3137 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3140 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3141 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3142 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3150 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3151 vec![self.tcx.types.err; len]
3154 // AST fragment checking
3157 expected: Expectation<'tcx>)
3163 ast::LitKind::Str(..) => tcx.mk_static_str(),
3164 ast::LitKind::ByteStr(ref v) => {
3165 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3166 tcx.mk_array(tcx.types.u8, v.len() as u64))
3168 ast::LitKind::Byte(_) => tcx.types.u8,
3169 ast::LitKind::Char(_) => tcx.types.char,
3170 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3171 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3172 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3173 let opt_ty = expected.to_option(self).and_then(|ty| {
3175 ty::Int(_) | ty::Uint(_) => Some(ty),
3176 ty::Char => Some(tcx.types.u8),
3177 ty::RawPtr(..) => Some(tcx.types.usize),
3178 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3182 opt_ty.unwrap_or_else(|| self.next_int_var())
3184 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3185 ast::LitKind::FloatUnsuffixed(_) => {
3186 let opt_ty = expected.to_option(self).and_then(|ty| {
3188 ty::Float(_) => Some(ty),
3192 opt_ty.unwrap_or_else(|| self.next_float_var())
3194 ast::LitKind::Bool(_) => tcx.types.bool,
3195 ast::LitKind::Err(_) => tcx.types.err,
3199 fn check_expr_eq_type(&self, expr: &'tcx hir::Expr, expected: Ty<'tcx>) {
3200 let ty = self.check_expr_with_hint(expr, expected);
3201 self.demand_eqtype(expr.span, expected, ty);
3204 pub fn check_expr_has_type_or_error(
3206 expr: &'tcx hir::Expr,
3209 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected))
3212 fn check_expr_meets_expectation_or_error(
3214 expr: &'tcx hir::Expr,
3215 expected: Expectation<'tcx>,
3217 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
3218 let mut ty = self.check_expr_with_expectation(expr, expected);
3220 // While we don't allow *arbitrary* coercions here, we *do* allow
3221 // coercions from ! to `expected`.
3223 assert!(!self.tables.borrow().adjustments().contains_key(expr.hir_id),
3224 "expression with never type wound up being adjusted");
3225 let adj_ty = self.next_diverging_ty_var(
3226 TypeVariableOrigin {
3227 kind: TypeVariableOriginKind::AdjustmentType,
3231 self.apply_adjustments(expr, vec![Adjustment {
3232 kind: Adjust::NeverToAny,
3238 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
3239 let expr = match &expr.node {
3240 ExprKind::DropTemps(expr) => expr,
3243 // Error possibly reported in `check_assign` so avoid emitting error again.
3244 err.emit_unless(self.is_assign_to_bool(expr, expected_ty));
3249 fn check_expr_coercable_to_type(&self, expr: &'tcx hir::Expr, expected: Ty<'tcx>) -> Ty<'tcx> {
3250 let ty = self.check_expr_with_hint(expr, expected);
3251 // checks don't need two phase
3252 self.demand_coerce(expr, ty, expected, AllowTwoPhase::No)
3255 fn check_expr_with_hint(&self, expr: &'tcx hir::Expr, expected: Ty<'tcx>) -> Ty<'tcx> {
3256 self.check_expr_with_expectation(expr, ExpectHasType(expected))
3259 fn check_expr_with_expectation(
3261 expr: &'tcx hir::Expr,
3262 expected: Expectation<'tcx>,
3264 self.check_expr_with_expectation_and_needs(expr, expected, Needs::None)
3267 fn check_expr(&self, expr: &'tcx hir::Expr) -> Ty<'tcx> {
3268 self.check_expr_with_expectation(expr, NoExpectation)
3271 fn check_expr_with_needs(&self, expr: &'tcx hir::Expr, needs: Needs) -> Ty<'tcx> {
3272 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
3275 // Determine the `Self` type, using fresh variables for all variables
3276 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3277 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3279 pub fn impl_self_ty(&self,
3280 span: Span, // (potential) receiver for this impl
3282 -> TypeAndSubsts<'tcx> {
3283 let ity = self.tcx.type_of(did);
3284 debug!("impl_self_ty: ity={:?}", ity);
3286 let substs = self.fresh_substs_for_item(span, did);
3287 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3289 TypeAndSubsts { substs: substs, ty: substd_ty }
3292 /// Unifies the output type with the expected type early, for more coercions
3293 /// and forward type information on the input expressions.
3294 fn expected_inputs_for_expected_output(&self,
3296 expected_ret: Expectation<'tcx>,
3297 formal_ret: Ty<'tcx>,
3298 formal_args: &[Ty<'tcx>])
3300 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3301 let ret_ty = match expected_ret.only_has_type(self) {
3303 None => return Vec::new()
3305 let expect_args = self.fudge_inference_if_ok(|| {
3306 // Attempt to apply a subtyping relationship between the formal
3307 // return type (likely containing type variables if the function
3308 // is polymorphic) and the expected return type.
3309 // No argument expectations are produced if unification fails.
3310 let origin = self.misc(call_span);
3311 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3313 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3314 // to identity so the resulting type is not constrained.
3317 // Process any obligations locally as much as
3318 // we can. We don't care if some things turn
3319 // out unconstrained or ambiguous, as we're
3320 // just trying to get hints here.
3321 self.save_and_restore_in_snapshot_flag(|_| {
3322 let mut fulfill = TraitEngine::new(self.tcx);
3323 for obligation in ok.obligations {
3324 fulfill.register_predicate_obligation(self, obligation);
3326 fulfill.select_where_possible(self)
3327 }).map_err(|_| ())?;
3329 Err(_) => return Err(()),
3332 // Record all the argument types, with the substitutions
3333 // produced from the above subtyping unification.
3334 Ok(formal_args.iter().map(|ty| {
3335 self.resolve_vars_if_possible(ty)
3337 }).unwrap_or_default();
3338 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3339 formal_args, formal_ret,
3340 expect_args, expected_ret);
3344 // Checks a method call.
3345 fn check_method_call(
3347 expr: &'tcx hir::Expr,
3348 segment: &hir::PathSegment,
3350 args: &'tcx [hir::Expr],
3351 expected: Expectation<'tcx>,
3354 let rcvr = &args[0];
3355 let rcvr_t = self.check_expr_with_needs(&rcvr, needs);
3356 // no need to check for bot/err -- callee does that
3357 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
3359 let method = match self.lookup_method(rcvr_t,
3365 self.write_method_call(expr.hir_id, method);
3369 if segment.ident.name != kw::Invalid {
3370 self.report_method_error(span,
3373 SelfSource::MethodCall(rcvr),
3381 // Call the generic checker.
3382 self.check_method_argument_types(span,
3390 fn check_return_expr(&self, return_expr: &'tcx hir::Expr) {
3394 .unwrap_or_else(|| span_bug!(return_expr.span,
3395 "check_return_expr called outside fn body"));
3397 let ret_ty = ret_coercion.borrow().expected_ty();
3398 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty.clone());
3399 ret_coercion.borrow_mut()
3401 &self.cause(return_expr.span,
3402 ObligationCauseCode::ReturnType(return_expr.hir_id)),
3407 // Check field access expressions
3410 expr: &'tcx hir::Expr,
3412 base: &'tcx hir::Expr,
3415 let expr_t = self.check_expr_with_needs(base, needs);
3416 let expr_t = self.structurally_resolved_type(base.span,
3418 let mut private_candidate = None;
3419 let mut autoderef = self.autoderef(expr.span, expr_t);
3420 while let Some((base_t, _)) = autoderef.next() {
3422 ty::Adt(base_def, substs) if !base_def.is_enum() => {
3423 debug!("struct named {:?}", base_t);
3424 let (ident, def_scope) =
3425 self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
3426 let fields = &base_def.non_enum_variant().fields;
3427 if let Some(index) = fields.iter().position(|f| f.ident.modern() == ident) {
3428 let field = &fields[index];
3429 let field_ty = self.field_ty(expr.span, field, substs);
3430 // Save the index of all fields regardless of their visibility in case
3431 // of error recovery.
3432 self.write_field_index(expr.hir_id, index);
3433 if field.vis.is_accessible_from(def_scope, self.tcx) {
3434 let adjustments = autoderef.adjust_steps(self, needs);
3435 self.apply_adjustments(base, adjustments);
3436 autoderef.finalize(self);
3438 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span);
3441 private_candidate = Some((base_def.did, field_ty));
3444 ty::Tuple(ref tys) => {
3445 let fstr = field.as_str();
3446 if let Ok(index) = fstr.parse::<usize>() {
3447 if fstr == index.to_string() {
3448 if let Some(field_ty) = tys.get(index) {
3449 let adjustments = autoderef.adjust_steps(self, needs);
3450 self.apply_adjustments(base, adjustments);
3451 autoderef.finalize(self);
3453 self.write_field_index(expr.hir_id, index);
3454 return field_ty.expect_ty();
3462 autoderef.unambiguous_final_ty(self);
3464 if let Some((did, field_ty)) = private_candidate {
3465 let struct_path = self.tcx().def_path_str(did);
3466 let mut err = struct_span_err!(self.tcx().sess, expr.span, E0616,
3467 "field `{}` of struct `{}` is private",
3468 field, struct_path);
3469 // Also check if an accessible method exists, which is often what is meant.
3470 if self.method_exists(field, expr_t, expr.hir_id, false)
3471 && !self.expr_in_place(expr.hir_id)
3473 self.suggest_method_call(
3475 &format!("a method `{}` also exists, call it with parentheses", field),
3483 } else if field.name == kw::Invalid {
3484 self.tcx().types.err
3485 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
3486 let mut err = type_error_struct!(self.tcx().sess, field.span, expr_t, E0615,
3487 "attempted to take value of method `{}` on type `{}`",
3490 if !self.expr_in_place(expr.hir_id) {
3491 self.suggest_method_call(
3493 "use parentheses to call the method",
3499 err.help("methods are immutable and cannot be assigned to");
3503 self.tcx().types.err
3505 if !expr_t.is_primitive_ty() {
3506 let mut err = self.no_such_field_err(field.span, field, expr_t);
3509 ty::Adt(def, _) if !def.is_enum() => {
3510 if let Some(suggested_field_name) =
3511 Self::suggest_field_name(def.non_enum_variant(),
3512 &field.as_str(), vec![]) {
3513 err.span_suggestion(
3515 "a field with a similar name exists",
3516 suggested_field_name.to_string(),
3517 Applicability::MaybeIncorrect,
3520 err.span_label(field.span, "unknown field");
3521 let struct_variant_def = def.non_enum_variant();
3522 let field_names = self.available_field_names(struct_variant_def);
3523 if !field_names.is_empty() {
3524 err.note(&format!("available fields are: {}",
3525 self.name_series_display(field_names)));
3529 ty::Array(_, len) => {
3530 if let (Some(len), Ok(user_index)) = (
3531 len.assert_usize(self.tcx),
3532 field.as_str().parse::<u64>()
3534 let base = self.tcx.sess.source_map()
3535 .span_to_snippet(base.span)
3537 self.tcx.hir().hir_to_pretty_string(base.hir_id));
3538 let help = "instead of using tuple indexing, use array indexing";
3539 let suggestion = format!("{}[{}]", base, field);
3540 let applicability = if len < user_index {
3541 Applicability::MachineApplicable
3543 Applicability::MaybeIncorrect
3545 err.span_suggestion(
3546 expr.span, help, suggestion, applicability
3551 let base = self.tcx.sess.source_map()
3552 .span_to_snippet(base.span)
3553 .unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
3554 let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
3555 let suggestion = format!("(*{}).{}", base, field);
3556 err.span_suggestion(
3560 Applicability::MaybeIncorrect,
3567 type_error_struct!(self.tcx().sess, field.span, expr_t, E0610,
3568 "`{}` is a primitive type and therefore doesn't have fields",
3571 self.tcx().types.err
3575 // Return an hint about the closest match in field names
3576 fn suggest_field_name(variant: &'tcx ty::VariantDef,
3578 skip: Vec<LocalInternedString>)
3580 let names = variant.fields.iter().filter_map(|field| {
3581 // ignore already set fields and private fields from non-local crates
3582 if skip.iter().any(|x| *x == field.ident.as_str()) ||
3583 (!variant.def_id.is_local() && field.vis != Visibility::Public)
3587 Some(&field.ident.name)
3591 find_best_match_for_name(names, field, None)
3594 fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<ast::Name> {
3595 variant.fields.iter().filter(|field| {
3597 self.tcx.adjust_ident_and_get_scope(field.ident, variant.def_id, self.body_id).1;
3598 field.vis.is_accessible_from(def_scope, self.tcx)
3600 .map(|field| field.ident.name)
3604 fn name_series_display(&self, names: Vec<ast::Name>) -> String {
3605 // dynamic limit, to never omit just one field
3606 let limit = if names.len() == 6 { 6 } else { 5 };
3607 let mut display = names.iter().take(limit)
3608 .map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
3609 if names.len() > limit {
3610 display = format!("{} ... and {} others", display, names.len() - limit);
3615 fn no_such_field_err<T: Display>(&self, span: Span, field: T, expr_t: &ty::TyS<'_>)
3616 -> DiagnosticBuilder<'_> {
3617 type_error_struct!(self.tcx().sess, span, expr_t, E0609,
3618 "no field `{}` on type `{}`",
3622 fn report_unknown_field(
3625 variant: &'tcx ty::VariantDef,
3627 skip_fields: &[hir::Field],
3630 if variant.recovered {
3633 let mut err = self.type_error_struct_with_diag(
3635 |actual| match ty.sty {
3636 ty::Adt(adt, ..) if adt.is_enum() => {
3637 struct_span_err!(self.tcx.sess, field.ident.span, E0559,
3638 "{} `{}::{}` has no field named `{}`",
3639 kind_name, actual, variant.ident, field.ident)
3642 struct_span_err!(self.tcx.sess, field.ident.span, E0560,
3643 "{} `{}` has no field named `{}`",
3644 kind_name, actual, field.ident)
3648 // prevent all specified fields from being suggested
3649 let skip_fields = skip_fields.iter().map(|ref x| x.ident.as_str());
3650 if let Some(field_name) = Self::suggest_field_name(variant,
3651 &field.ident.as_str(),
3652 skip_fields.collect()) {
3653 err.span_suggestion(
3655 "a field with a similar name exists",
3656 field_name.to_string(),
3657 Applicability::MaybeIncorrect,
3661 ty::Adt(adt, ..) => {
3663 err.span_label(field.ident.span,
3664 format!("`{}::{}` does not have this field",
3665 ty, variant.ident));
3667 err.span_label(field.ident.span,
3668 format!("`{}` does not have this field", ty));
3670 let available_field_names = self.available_field_names(variant);
3671 if !available_field_names.is_empty() {
3672 err.note(&format!("available fields are: {}",
3673 self.name_series_display(available_field_names)));
3676 _ => bug!("non-ADT passed to report_unknown_field")
3682 fn check_expr_struct_fields(
3685 expected: Expectation<'tcx>,
3686 expr_id: hir::HirId,
3688 variant: &'tcx ty::VariantDef,
3689 ast_fields: &'tcx [hir::Field],
3690 check_completeness: bool,
3695 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3696 .get(0).cloned().unwrap_or(adt_ty);
3697 // re-link the regions that EIfEO can erase.
3698 self.demand_eqtype(span, adt_ty_hint, adt_ty);
3700 let (substs, adt_kind, kind_name) = match &adt_ty.sty {
3701 &ty::Adt(adt, substs) => {
3702 (substs, adt.adt_kind(), adt.variant_descr())
3704 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3707 let mut remaining_fields = variant.fields.iter().enumerate().map(|(i, field)|
3708 (field.ident.modern(), (i, field))
3709 ).collect::<FxHashMap<_, _>>();
3711 let mut seen_fields = FxHashMap::default();
3713 let mut error_happened = false;
3715 // Type-check each field.
3716 for field in ast_fields {
3717 let ident = tcx.adjust_ident(field.ident, variant.def_id);
3718 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
3719 seen_fields.insert(ident, field.span);
3720 self.write_field_index(field.hir_id, i);
3722 // We don't look at stability attributes on
3723 // struct-like enums (yet...), but it's definitely not
3724 // a bug to have constructed one.
3725 if adt_kind != AdtKind::Enum {
3726 tcx.check_stability(v_field.did, Some(expr_id), field.span);
3729 self.field_ty(field.span, v_field, substs)
3731 error_happened = true;
3732 if let Some(prev_span) = seen_fields.get(&ident) {
3733 let mut err = struct_span_err!(self.tcx.sess,
3736 "field `{}` specified more than once",
3739 err.span_label(field.ident.span, "used more than once");
3740 err.span_label(*prev_span, format!("first use of `{}`", ident));
3744 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3750 // Make sure to give a type to the field even if there's
3751 // an error, so we can continue type-checking.
3752 self.check_expr_coercable_to_type(&field.expr, field_type);
3755 // Make sure the programmer specified correct number of fields.
3756 if kind_name == "union" {
3757 if ast_fields.len() != 1 {
3758 tcx.sess.span_err(span, "union expressions should have exactly one field");
3760 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3761 let len = remaining_fields.len();
3763 let mut displayable_field_names = remaining_fields
3765 .map(|ident| ident.as_str())
3766 .collect::<Vec<_>>();
3768 displayable_field_names.sort();
3770 let truncated_fields_error = if len <= 3 {
3773 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3776 let remaining_fields_names = displayable_field_names.iter().take(3)
3777 .map(|n| format!("`{}`", n))
3778 .collect::<Vec<_>>()
3781 struct_span_err!(tcx.sess, span, E0063,
3782 "missing field{} {}{} in initializer of `{}`",
3783 if remaining_fields.len() == 1 { "" } else { "s" },
3784 remaining_fields_names,
3785 truncated_fields_error,
3787 .span_label(span, format!("missing {}{}",
3788 remaining_fields_names,
3789 truncated_fields_error))
3795 fn check_struct_fields_on_error(
3797 fields: &'tcx [hir::Field],
3798 base_expr: &'tcx Option<P<hir::Expr>>,
3800 for field in fields {
3801 self.check_expr(&field.expr);
3803 if let Some(ref base) = *base_expr {
3804 self.check_expr(&base);
3808 pub fn check_struct_path(&self,
3811 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3812 let path_span = match *qpath {
3813 QPath::Resolved(_, ref path) => path.span,
3814 QPath::TypeRelative(ref qself, _) => qself.span
3816 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3817 let variant = match def {
3819 self.set_tainted_by_errors();
3822 Res::Def(DefKind::Variant, _) => {
3824 ty::Adt(adt, substs) => {
3825 Some((adt.variant_of_res(def), adt.did, substs))
3827 _ => bug!("unexpected type: {:?}", ty)
3830 Res::Def(DefKind::Struct, _)
3831 | Res::Def(DefKind::Union, _)
3832 | Res::Def(DefKind::TyAlias, _)
3833 | Res::Def(DefKind::AssocTy, _)
3834 | Res::SelfTy(..) => {
3836 ty::Adt(adt, substs) if !adt.is_enum() => {
3837 Some((adt.non_enum_variant(), adt.did, substs))
3842 _ => bug!("unexpected definition: {:?}", def)
3845 if let Some((variant, did, substs)) = variant {
3846 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3847 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3849 // Check bounds on type arguments used in the path.
3850 let bounds = self.instantiate_bounds(path_span, did, substs);
3851 let cause = traits::ObligationCause::new(path_span, self.body_id,
3852 traits::ItemObligation(did));
3853 self.add_obligations_for_parameters(cause, &bounds);
3857 struct_span_err!(self.tcx.sess, path_span, E0071,
3858 "expected struct, variant or union type, found {}",
3859 ty.sort_string(self.tcx))
3860 .span_label(path_span, "not a struct")
3866 fn check_expr_struct(
3869 expected: Expectation<'tcx>,
3871 fields: &'tcx [hir::Field],
3872 base_expr: &'tcx Option<P<hir::Expr>>,
3874 // Find the relevant variant
3875 let (variant, adt_ty) =
3876 if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id) {
3879 self.check_struct_fields_on_error(fields, base_expr);
3880 return self.tcx.types.err;
3883 let path_span = match *qpath {
3884 QPath::Resolved(_, ref path) => path.span,
3885 QPath::TypeRelative(ref qself, _) => qself.span
3888 // Prohibit struct expressions when non-exhaustive flag is set.
3889 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
3890 if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
3891 span_err!(self.tcx.sess, expr.span, E0639,
3892 "cannot create non-exhaustive {} using struct expression",
3893 adt.variant_descr());
3896 let error_happened = self.check_expr_struct_fields(adt_ty, expected, expr.hir_id, path_span,
3897 variant, fields, base_expr.is_none());
3898 if let &Some(ref base_expr) = base_expr {
3899 // If check_expr_struct_fields hit an error, do not attempt to populate
3900 // the fields with the base_expr. This could cause us to hit errors later
3901 // when certain fields are assumed to exist that in fact do not.
3902 if !error_happened {
3903 self.check_expr_has_type_or_error(base_expr, adt_ty);
3905 ty::Adt(adt, substs) if adt.is_struct() => {
3906 let fru_field_types = adt.non_enum_variant().fields.iter().map(|f| {
3907 self.normalize_associated_types_in(expr.span, &f.ty(self.tcx, substs))
3912 .fru_field_types_mut()
3913 .insert(expr.hir_id, fru_field_types);
3916 span_err!(self.tcx.sess, base_expr.span, E0436,
3917 "functional record update syntax requires a struct");
3922 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
3928 /// If an expression has any sub-expressions that result in a type error,
3929 /// inspecting that expression's type with `ty.references_error()` will return
3930 /// true. Likewise, if an expression is known to diverge, inspecting its
3931 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3932 /// strict, _|_ can appear in the type of an expression that does not,
3933 /// itself, diverge: for example, fn() -> _|_.)
3934 /// Note that inspecting a type's structure *directly* may expose the fact
3935 /// that there are actually multiple representations for `Error`, so avoid
3936 /// that when err needs to be handled differently.
3937 fn check_expr_with_expectation_and_needs(
3939 expr: &'tcx hir::Expr,
3940 expected: Expectation<'tcx>,
3943 debug!(">> type-checking: expr={:?} expected={:?}",
3946 // Warn for expressions after diverging siblings.
3947 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
3949 // Hide the outer diverging and has_errors flags.
3950 let old_diverges = self.diverges.get();
3951 let old_has_errors = self.has_errors.get();
3952 self.diverges.set(Diverges::Maybe);
3953 self.has_errors.set(false);
3955 let ty = self.check_expr_kind(expr, expected, needs);
3957 // Warn for non-block expressions with diverging children.
3959 ExprKind::Block(..) |
3960 ExprKind::Loop(..) | ExprKind::While(..) |
3961 ExprKind::Match(..) => {}
3963 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression")
3966 // Any expression that produces a value of type `!` must have diverged
3968 self.diverges.set(self.diverges.get() | Diverges::Always);
3971 // Record the type, which applies it effects.
3972 // We need to do this after the warning above, so that
3973 // we don't warn for the diverging expression itself.
3974 self.write_ty(expr.hir_id, ty);
3976 // Combine the diverging and has_error flags.
3977 self.diverges.set(self.diverges.get() | old_diverges);
3978 self.has_errors.set(self.has_errors.get() | old_has_errors);
3980 debug!("type of {} is...", self.tcx.hir().hir_to_string(expr.hir_id));
3981 debug!("... {:?}, expected is {:?}", ty, expected);
3988 expr: &'tcx hir::Expr,
3989 expected: Expectation<'tcx>,
3993 "check_expr_kind(expr={:?}, expected={:?}, needs={:?})",
4000 let id = expr.hir_id;
4002 ExprKind::Box(ref subexpr) => {
4003 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
4005 ty::Adt(def, _) if def.is_box()
4006 => Expectation::rvalue_hint(self, ty.boxed_ty()),
4010 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
4011 tcx.mk_box(referent_ty)
4014 ExprKind::Lit(ref lit) => {
4015 self.check_lit(&lit, expected)
4017 ExprKind::Binary(op, ref lhs, ref rhs) => {
4018 self.check_binop(expr, op, lhs, rhs)
4020 ExprKind::AssignOp(op, ref lhs, ref rhs) => {
4021 self.check_binop_assign(expr, op, lhs, rhs)
4023 ExprKind::Unary(unop, ref oprnd) => {
4024 let expected_inner = match unop {
4025 hir::UnNot | hir::UnNeg => {
4032 let needs = match unop {
4033 hir::UnDeref => needs,
4036 let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd,
4040 if !oprnd_t.references_error() {
4041 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
4044 if let Some(mt) = oprnd_t.builtin_deref(true) {
4046 } else if let Some(ok) = self.try_overloaded_deref(
4047 expr.span, oprnd_t, needs) {
4048 let method = self.register_infer_ok_obligations(ok);
4049 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].sty {
4050 let mutbl = match mutbl {
4051 hir::MutImmutable => AutoBorrowMutability::Immutable,
4052 hir::MutMutable => AutoBorrowMutability::Mutable {
4053 // (It shouldn't actually matter for unary ops whether
4054 // we enable two-phase borrows or not, since a unary
4055 // op has no additional operands.)
4056 allow_two_phase_borrow: AllowTwoPhase::No,
4059 self.apply_adjustments(oprnd, vec![Adjustment {
4060 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
4061 target: method.sig.inputs()[0]
4064 oprnd_t = self.make_overloaded_place_return_type(method).ty;
4065 self.write_method_call(expr.hir_id, method);
4067 let mut err = type_error_struct!(
4072 "type `{}` cannot be dereferenced",
4075 let sp = tcx.sess.source_map().start_point(expr.span);
4076 if let Some(sp) = tcx.sess.parse_sess.ambiguous_block_expr_parse
4079 tcx.sess.parse_sess.expr_parentheses_needed(
4086 oprnd_t = tcx.types.err;
4090 let result = self.check_user_unop(expr, oprnd_t, unop);
4091 // If it's builtin, we can reuse the type, this helps inference.
4092 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::Bool) {
4097 let result = self.check_user_unop(expr, oprnd_t, unop);
4098 // If it's builtin, we can reuse the type, this helps inference.
4099 if !oprnd_t.is_numeric() {
4107 ExprKind::AddrOf(mutbl, ref oprnd) => {
4108 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
4110 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
4111 if oprnd.is_place_expr() {
4112 // Places may legitimately have unsized types.
4113 // For example, dereferences of a fat pointer and
4114 // the last field of a struct can be unsized.
4117 Expectation::rvalue_hint(self, ty)
4123 let needs = Needs::maybe_mut_place(mutbl);
4124 let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs);
4126 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
4127 if tm.ty.references_error() {
4130 // Note: at this point, we cannot say what the best lifetime
4131 // is to use for resulting pointer. We want to use the
4132 // shortest lifetime possible so as to avoid spurious borrowck
4133 // errors. Moreover, the longest lifetime will depend on the
4134 // precise details of the value whose address is being taken
4135 // (and how long it is valid), which we don't know yet until type
4136 // inference is complete.
4138 // Therefore, here we simply generate a region variable. The
4139 // region inferencer will then select the ultimate value.
4140 // Finally, borrowck is charged with guaranteeing that the
4141 // value whose address was taken can actually be made to live
4142 // as long as it needs to live.
4143 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
4144 tcx.mk_ref(region, tm)
4147 ExprKind::Path(ref qpath) => {
4148 let (res, opt_ty, segs) = self.resolve_ty_and_res_ufcs(qpath, expr.hir_id,
4150 let ty = match res {
4152 self.set_tainted_by_errors();
4155 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
4156 report_unexpected_variant_res(tcx, res, expr.span, qpath);
4159 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, id).0,
4162 if let ty::FnDef(..) = ty.sty {
4163 let fn_sig = ty.fn_sig(tcx);
4164 if !tcx.features().unsized_locals {
4165 // We want to remove some Sized bounds from std functions,
4166 // but don't want to expose the removal to stable Rust.
4167 // i.e., we don't want to allow
4173 // to work in stable even if the Sized bound on `drop` is relaxed.
4174 for i in 0..fn_sig.inputs().skip_binder().len() {
4175 // We just want to check sizedness, so instead of introducing
4176 // placeholder lifetimes with probing, we just replace higher lifetimes
4178 let input = self.replace_bound_vars_with_fresh_vars(
4180 infer::LateBoundRegionConversionTime::FnCall,
4181 &fn_sig.input(i)).0;
4182 self.require_type_is_sized_deferred(input, expr.span,
4183 traits::SizedArgumentType);
4186 // Here we want to prevent struct constructors from returning unsized types.
4187 // There were two cases this happened: fn pointer coercion in stable
4188 // and usual function call in presense of unsized_locals.
4189 // Also, as we just want to check sizedness, instead of introducing
4190 // placeholder lifetimes with probing, we just replace higher lifetimes
4192 let output = self.replace_bound_vars_with_fresh_vars(
4194 infer::LateBoundRegionConversionTime::FnCall,
4195 &fn_sig.output()).0;
4196 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
4199 // We always require that the type provided as the value for
4200 // a type parameter outlives the moment of instantiation.
4201 let substs = self.tables.borrow().node_substs(expr.hir_id);
4202 self.add_wf_bounds(substs, expr);
4206 ExprKind::InlineAsm(_, ref outputs, ref inputs) => {
4207 for expr in outputs.iter().chain(inputs.iter()) {
4208 self.check_expr(expr);
4212 ExprKind::Break(destination, ref expr_opt) => {
4213 if let Ok(target_id) = destination.target_id {
4215 if let Some(ref e) = *expr_opt {
4216 // If this is a break with a value, we need to type-check
4217 // the expression. Get an expected type from the loop context.
4218 let opt_coerce_to = {
4219 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4220 enclosing_breakables.find_breakable(target_id)
4223 .map(|coerce| coerce.expected_ty())
4226 // If the loop context is not a `loop { }`, then break with
4227 // a value is illegal, and `opt_coerce_to` will be `None`.
4228 // Just set expectation to error in that case.
4229 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
4231 // Recurse without `enclosing_breakables` borrowed.
4232 e_ty = self.check_expr_with_hint(e, coerce_to);
4233 cause = self.misc(e.span);
4235 // Otherwise, this is a break *without* a value. That's
4236 // always legal, and is equivalent to `break ()`.
4237 e_ty = tcx.mk_unit();
4238 cause = self.misc(expr.span);
4241 // Now that we have type-checked `expr_opt`, borrow
4242 // the `enclosing_loops` field and let's coerce the
4243 // type of `expr_opt` into what is expected.
4244 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4245 let ctxt = enclosing_breakables.find_breakable(target_id);
4246 if let Some(ref mut coerce) = ctxt.coerce {
4247 if let Some(ref e) = *expr_opt {
4248 coerce.coerce(self, &cause, e, e_ty);
4250 assert!(e_ty.is_unit());
4251 coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
4254 // If `ctxt.coerce` is `None`, we can just ignore
4255 // the type of the expresison. This is because
4256 // either this was a break *without* a value, in
4257 // which case it is always a legal type (`()`), or
4258 // else an error would have been flagged by the
4259 // `loops` pass for using break with an expression
4260 // where you are not supposed to.
4261 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
4264 ctxt.may_break = true;
4266 // the type of a `break` is always `!`, since it diverges
4269 // Otherwise, we failed to find the enclosing loop;
4270 // this can only happen if the `break` was not
4271 // inside a loop at all, which is caught by the
4272 // loop-checking pass.
4273 if self.tcx.sess.err_count() == 0 {
4274 self.tcx.sess.delay_span_bug(expr.span,
4275 "break was outside loop, but no error was emitted");
4278 // We still need to assign a type to the inner expression to
4279 // prevent the ICE in #43162.
4280 if let Some(ref e) = *expr_opt {
4281 self.check_expr_with_hint(e, tcx.types.err);
4283 // ... except when we try to 'break rust;'.
4284 // ICE this expression in particular (see #43162).
4285 if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.node {
4286 if path.segments.len() == 1 &&
4287 path.segments[0].ident.name == sym::rust {
4288 fatally_break_rust(self.tcx.sess);
4292 // There was an error; make type-check fail.
4297 ExprKind::Continue(destination) => {
4298 if destination.target_id.is_ok() {
4301 // There was an error; make type-check fail.
4305 ExprKind::Ret(ref expr_opt) => {
4306 if self.ret_coercion.is_none() {
4307 struct_span_err!(self.tcx.sess, expr.span, E0572,
4308 "return statement outside of function body").emit();
4309 } else if let Some(ref e) = *expr_opt {
4310 if self.ret_coercion_span.borrow().is_none() {
4311 *self.ret_coercion_span.borrow_mut() = Some(e.span);
4313 self.check_return_expr(e);
4315 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
4316 if self.ret_coercion_span.borrow().is_none() {
4317 *self.ret_coercion_span.borrow_mut() = Some(expr.span);
4319 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
4320 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
4321 coercion.coerce_forced_unit(
4326 fn_decl.output.span(),
4328 "expected `{}` because of this return type",
4336 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
4341 ExprKind::Assign(ref lhs, ref rhs) => {
4342 self.check_assign(expr, expected, lhs, rhs)
4344 ExprKind::While(ref cond, ref body, _) => {
4345 let ctxt = BreakableCtxt {
4346 // cannot use break with a value from a while loop
4348 may_break: false, // Will get updated if/when we find a `break`.
4351 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
4352 self.check_expr_has_type_or_error(&cond, tcx.types.bool);
4353 let cond_diverging = self.diverges.get();
4354 self.check_block_no_value(&body);
4356 // We may never reach the body so it diverging means nothing.
4357 self.diverges.set(cond_diverging);
4361 // No way to know whether it's diverging because
4362 // of a `break` or an outer `break` or `return`.
4363 self.diverges.set(Diverges::Maybe);
4368 ExprKind::Loop(ref body, _, source) => {
4369 let coerce = match source {
4370 // you can only use break with a value from a normal `loop { }`
4371 hir::LoopSource::Loop => {
4372 let coerce_to = expected.coercion_target_type(self, body.span);
4373 Some(CoerceMany::new(coerce_to))
4376 hir::LoopSource::WhileLet |
4377 hir::LoopSource::ForLoop => {
4382 let ctxt = BreakableCtxt {
4384 may_break: false, // Will get updated if/when we find a `break`.
4387 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
4388 self.check_block_no_value(&body);
4392 // No way to know whether it's diverging because
4393 // of a `break` or an outer `break` or `return`.
4394 self.diverges.set(Diverges::Maybe);
4397 // If we permit break with a value, then result type is
4398 // the LUB of the breaks (possibly ! if none); else, it
4399 // is nil. This makes sense because infinite loops
4400 // (which would have type !) are only possible iff we
4401 // permit break with a value [1].
4402 if ctxt.coerce.is_none() && !ctxt.may_break {
4404 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
4406 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
4408 ExprKind::Match(ref discrim, ref arms, match_src) => {
4409 self.check_match(expr, &discrim, arms, expected, match_src)
4411 ExprKind::Closure(capture, ref decl, body_id, _, gen) => {
4412 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
4414 ExprKind::Block(ref body, _) => {
4415 self.check_block_with_expected(&body, expected)
4417 ExprKind::Call(ref callee, ref args) => {
4418 self.check_call(expr, &callee, args, expected)
4420 ExprKind::MethodCall(ref segment, span, ref args) => {
4421 self.check_method_call(expr, segment, span, args, expected, needs)
4423 ExprKind::Cast(ref e, ref t) => {
4424 // Find the type of `e`. Supply hints based on the type we are casting to,
4426 let t_cast = self.to_ty_saving_user_provided_ty(t);
4427 let t_cast = self.resolve_vars_if_possible(&t_cast);
4428 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
4429 let t_cast = self.resolve_vars_if_possible(&t_cast);
4431 // Eagerly check for some obvious errors.
4432 if t_expr.references_error() || t_cast.references_error() {
4435 // Defer other checks until we're done type checking.
4436 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
4437 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
4439 deferred_cast_checks.push(cast_check);
4442 Err(ErrorReported) => {
4448 ExprKind::Type(ref e, ref t) => {
4449 let ty = self.to_ty_saving_user_provided_ty(&t);
4450 self.check_expr_eq_type(&e, ty);
4453 ExprKind::DropTemps(ref e) => {
4454 self.check_expr_with_expectation(e, expected)
4456 ExprKind::Array(ref args) => {
4457 let uty = expected.to_option(self).and_then(|uty| {
4459 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
4464 let element_ty = if !args.is_empty() {
4465 let coerce_to = uty.unwrap_or_else(|| {
4466 self.next_ty_var(TypeVariableOrigin {
4467 kind: TypeVariableOriginKind::TypeInference,
4471 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
4472 assert_eq!(self.diverges.get(), Diverges::Maybe);
4474 let e_ty = self.check_expr_with_hint(e, coerce_to);
4475 let cause = self.misc(e.span);
4476 coerce.coerce(self, &cause, e, e_ty);
4478 coerce.complete(self)
4480 self.next_ty_var(TypeVariableOrigin {
4481 kind: TypeVariableOriginKind::TypeInference,
4485 tcx.mk_array(element_ty, args.len() as u64)
4487 ExprKind::Repeat(ref element, ref count) => {
4488 let count_def_id = tcx.hir().local_def_id_from_hir_id(count.hir_id);
4489 let count = if self.const_param_def_id(count).is_some() {
4490 Ok(self.to_const(count, self.tcx.type_of(count_def_id)))
4492 let param_env = ty::ParamEnv::empty();
4493 let substs = InternalSubsts::identity_for_item(tcx.global_tcx(), count_def_id);
4494 let instance = ty::Instance::resolve(
4500 let global_id = GlobalId {
4505 tcx.const_eval(param_env.and(global_id))
4508 let uty = match expected {
4509 ExpectHasType(uty) => {
4511 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
4518 let (element_ty, t) = match uty {
4520 self.check_expr_coercable_to_type(&element, uty);
4524 let ty = self.next_ty_var(TypeVariableOrigin {
4525 kind: TypeVariableOriginKind::MiscVariable,
4528 let element_ty = self.check_expr_has_type_or_error(&element, ty);
4533 if let Ok(count) = count {
4534 let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1);
4536 // For [foo, ..n] where n > 1, `foo` must have
4538 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
4539 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
4543 if element_ty.references_error() {
4545 } else if let Ok(count) = count {
4546 tcx.mk_ty(ty::Array(t, count))
4551 ExprKind::Tup(ref elts) => {
4552 let flds = expected.only_has_type(self).and_then(|ty| {
4553 let ty = self.resolve_type_vars_with_obligations(ty);
4555 ty::Tuple(ref flds) => Some(&flds[..]),
4560 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
4561 let t = match flds {
4562 Some(ref fs) if i < fs.len() => {
4563 let ety = fs[i].expect_ty();
4564 self.check_expr_coercable_to_type(&e, ety);
4568 self.check_expr_with_expectation(&e, NoExpectation)
4573 let tuple = tcx.mk_tup(elt_ts_iter);
4574 if tuple.references_error() {
4577 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
4581 ExprKind::Struct(ref qpath, ref fields, ref base_expr) => {
4582 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
4584 ExprKind::Field(ref base, field) => {
4585 self.check_field(expr, needs, &base, field)
4587 ExprKind::Index(ref base, ref idx) => {
4588 let base_t = self.check_expr_with_needs(&base, needs);
4589 let idx_t = self.check_expr(&idx);
4591 if base_t.references_error() {
4593 } else if idx_t.references_error() {
4596 let base_t = self.structurally_resolved_type(base.span, base_t);
4597 match self.lookup_indexing(expr, base, base_t, idx_t, needs) {
4598 Some((index_ty, element_ty)) => {
4599 // two-phase not needed because index_ty is never mutable
4600 self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No);
4605 type_error_struct!(tcx.sess, expr.span, base_t, E0608,
4606 "cannot index into a value of type `{}`",
4608 // Try to give some advice about indexing tuples.
4609 if let ty::Tuple(..) = base_t.sty {
4610 let mut needs_note = true;
4611 // If the index is an integer, we can show the actual
4612 // fixed expression:
4613 if let ExprKind::Lit(ref lit) = idx.node {
4614 if let ast::LitKind::Int(i,
4615 ast::LitIntType::Unsuffixed) = lit.node {
4616 let snip = tcx.sess.source_map().span_to_snippet(base.span);
4617 if let Ok(snip) = snip {
4618 err.span_suggestion(
4620 "to access tuple elements, use",
4621 format!("{}.{}", snip, i),
4622 Applicability::MachineApplicable,
4629 err.help("to access tuple elements, use tuple indexing \
4630 syntax (e.g., `tuple.0`)");
4639 ExprKind::Yield(ref value) => {
4640 match self.yield_ty {
4642 self.check_expr_coercable_to_type(&value, ty);
4645 struct_span_err!(self.tcx.sess, expr.span, E0627,
4646 "yield statement outside of generator literal").emit();
4651 hir::ExprKind::Err => {
4657 /// Type check assignment expression `expr` of form `lhs = rhs`.
4658 /// The expected type is `()` and is passsed to the function for the purposes of diagnostics.
4661 expr: &'tcx hir::Expr,
4662 expected: Expectation<'tcx>,
4663 lhs: &'tcx hir::Expr,
4664 rhs: &'tcx hir::Expr,
4666 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
4667 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
4669 let expected_ty = expected.coercion_target_type(self, expr.span);
4670 if expected_ty == self.tcx.types.bool {
4671 // The expected type is `bool` but this will result in `()` so we can reasonably
4672 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
4673 // The likely cause of this is `if foo = bar { .. }`.
4674 let actual_ty = self.tcx.mk_unit();
4675 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
4676 let msg = "try comparing for equality";
4677 let left = self.tcx.sess.source_map().span_to_snippet(lhs.span);
4678 let right = self.tcx.sess.source_map().span_to_snippet(rhs.span);
4679 if let (Ok(left), Ok(right)) = (left, right) {
4680 let help = format!("{} == {}", left, right);
4681 err.span_suggestion(expr.span, msg, help, Applicability::MaybeIncorrect);
4686 } else if !lhs.is_place_expr() {
4687 struct_span_err!(self.tcx.sess, expr.span, E0070,
4688 "invalid left-hand side expression")
4689 .span_label(expr.span, "left-hand of expression not valid")
4693 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
4695 if lhs_ty.references_error() || rhs_ty.references_error() {
4702 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4703 // The newly resolved definition is written into `type_dependent_defs`.
4704 fn finish_resolving_struct_path(&self,
4711 QPath::Resolved(ref maybe_qself, ref path) => {
4712 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4713 let ty = AstConv::res_to_ty(self, self_ty, path, true);
4716 QPath::TypeRelative(ref qself, ref segment) => {
4717 let ty = self.to_ty(qself);
4719 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.node {
4724 let result = AstConv::associated_path_to_ty(
4733 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
4734 let result = result.map(|(_, kind, def_id)| (kind, def_id));
4736 // Write back the new resolution.
4737 self.write_resolution(hir_id, result);
4739 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
4744 /// Resolves an associated value path into a base type and associated constant, or method
4745 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
4746 pub fn resolve_ty_and_res_ufcs<'b>(&self,
4750 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
4752 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
4753 let (ty, qself, item_segment) = match *qpath {
4754 QPath::Resolved(ref opt_qself, ref path) => {
4756 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4757 &path.segments[..]);
4759 QPath::TypeRelative(ref qself, ref segment) => {
4760 (self.to_ty(qself), qself, segment)
4763 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
4764 // Return directly on cache hit. This is useful to avoid doubly reporting
4765 // errors with default match binding modes. See #44614.
4766 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
4767 .unwrap_or(Res::Err);
4768 return (def, Some(ty), slice::from_ref(&**item_segment));
4770 let item_name = item_segment.ident;
4771 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
4772 let result = match error {
4773 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
4774 _ => Err(ErrorReported),
4776 if item_name.name != kw::Invalid {
4777 self.report_method_error(
4781 SelfSource::QPath(qself),
4789 // Write back the new resolution.
4790 self.write_resolution(hir_id, result);
4792 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
4794 slice::from_ref(&**item_segment),
4798 pub fn check_decl_initializer(
4800 local: &'tcx hir::Local,
4801 init: &'tcx hir::Expr,
4803 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
4804 // for #42640 (default match binding modes).
4807 let ref_bindings = local.pat.contains_explicit_ref_binding();
4809 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
4810 if let Some(m) = ref_bindings {
4811 // Somewhat subtle: if we have a `ref` binding in the pattern,
4812 // we want to avoid introducing coercions for the RHS. This is
4813 // both because it helps preserve sanity and, in the case of
4814 // ref mut, for soundness (issue #23116). In particular, in
4815 // the latter case, we need to be clear that the type of the
4816 // referent for the reference that results is *equal to* the
4817 // type of the place it is referencing, and not some
4818 // supertype thereof.
4819 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4820 self.demand_eqtype(init.span, local_ty, init_ty);
4823 self.check_expr_coercable_to_type(init, local_ty)
4827 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
4828 let t = self.local_ty(local.span, local.hir_id).decl_ty;
4829 self.write_ty(local.hir_id, t);
4831 if let Some(ref init) = local.init {
4832 let init_ty = self.check_decl_initializer(local, &init);
4833 if init_ty.references_error() {
4834 self.write_ty(local.hir_id, init_ty);
4838 self.check_pat_walk(
4841 ty::BindingMode::BindByValue(hir::Mutability::MutImmutable),
4844 let pat_ty = self.node_ty(local.pat.hir_id);
4845 if pat_ty.references_error() {
4846 self.write_ty(local.hir_id, pat_ty);
4850 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
4851 // Don't do all the complex logic below for `DeclItem`.
4853 hir::StmtKind::Item(..) => return,
4854 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
4857 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
4859 // Hide the outer diverging and `has_errors` flags.
4860 let old_diverges = self.diverges.get();
4861 let old_has_errors = self.has_errors.get();
4862 self.diverges.set(Diverges::Maybe);
4863 self.has_errors.set(false);
4866 hir::StmtKind::Local(ref l) => {
4867 self.check_decl_local(&l);
4870 hir::StmtKind::Item(_) => {}
4871 hir::StmtKind::Expr(ref expr) => {
4872 // Check with expected type of `()`.
4873 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit());
4875 hir::StmtKind::Semi(ref expr) => {
4876 self.check_expr(&expr);
4880 // Combine the diverging and `has_error` flags.
4881 self.diverges.set(self.diverges.get() | old_diverges);
4882 self.has_errors.set(self.has_errors.get() | old_has_errors);
4885 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
4886 let unit = self.tcx.mk_unit();
4887 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4889 // if the block produces a `!` value, that can always be
4890 // (effectively) coerced to unit.
4892 self.demand_suptype(blk.span, unit, ty);
4896 fn check_block_with_expected(
4898 blk: &'tcx hir::Block,
4899 expected: Expectation<'tcx>,
4902 let mut fcx_ps = self.ps.borrow_mut();
4903 let unsafety_state = fcx_ps.recurse(blk);
4904 replace(&mut *fcx_ps, unsafety_state)
4907 // In some cases, blocks have just one exit, but other blocks
4908 // can be targeted by multiple breaks. This can happen both
4909 // with labeled blocks as well as when we desugar
4910 // a `try { ... }` expression.
4914 // 'a: { if true { break 'a Err(()); } Ok(()) }
4916 // Here we would wind up with two coercions, one from
4917 // `Err(())` and the other from the tail expression
4918 // `Ok(())`. If the tail expression is omitted, that's a
4919 // "forced unit" -- unless the block diverges, in which
4920 // case we can ignore the tail expression (e.g., `'a: {
4921 // break 'a 22; }` would not force the type of the block
4923 let tail_expr = blk.expr.as_ref();
4924 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4925 let coerce = if blk.targeted_by_break {
4926 CoerceMany::new(coerce_to_ty)
4928 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4929 Some(e) => slice::from_ref(e),
4932 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4935 let prev_diverges = self.diverges.get();
4936 let ctxt = BreakableCtxt {
4937 coerce: Some(coerce),
4941 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4942 for s in &blk.stmts {
4946 // check the tail expression **without** holding the
4947 // `enclosing_breakables` lock below.
4948 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4950 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4951 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4952 let coerce = ctxt.coerce.as_mut().unwrap();
4953 if let Some(tail_expr_ty) = tail_expr_ty {
4954 let tail_expr = tail_expr.unwrap();
4955 let cause = self.cause(tail_expr.span,
4956 ObligationCauseCode::BlockTailExpression(blk.hir_id));
4962 // Subtle: if there is no explicit tail expression,
4963 // that is typically equivalent to a tail expression
4964 // of `()` -- except if the block diverges. In that
4965 // case, there is no value supplied from the tail
4966 // expression (assuming there are no other breaks,
4967 // this implies that the type of the block will be
4970 // #41425 -- label the implicit `()` as being the
4971 // "found type" here, rather than the "expected type".
4972 if !self.diverges.get().always() {
4973 // #50009 -- Do not point at the entire fn block span, point at the return type
4974 // span, as it is the cause of the requirement, and
4975 // `consider_hint_about_removing_semicolon` will point at the last expression
4976 // if it were a relevant part of the error. This improves usability in editors
4977 // that highlight errors inline.
4978 let mut sp = blk.span;
4979 let mut fn_span = None;
4980 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4981 let ret_sp = decl.output.span();
4982 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4983 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4984 // output would otherwise be incorrect and even misleading. Make sure
4985 // the span we're aiming at correspond to a `fn` body.
4986 if block_sp == blk.span {
4988 fn_span = Some(ident.span);
4992 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4993 if let Some(expected_ty) = expected.only_has_type(self) {
4994 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4996 if let Some(fn_span) = fn_span {
4997 err.span_label(fn_span, "this function's body doesn't return");
5005 // If we can break from the block, then the block's exit is always reachable
5006 // (... as long as the entry is reachable) - regardless of the tail of the block.
5007 self.diverges.set(prev_diverges);
5010 let mut ty = ctxt.coerce.unwrap().complete(self);
5012 if self.has_errors.get() || ty.references_error() {
5013 ty = self.tcx.types.err
5016 self.write_ty(blk.hir_id, ty);
5018 *self.ps.borrow_mut() = prev;
5022 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
5023 let node = self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_item(id));
5025 Node::Item(&hir::Item {
5026 node: hir::ItemKind::Fn(_, _, _, body_id), ..
5028 Node::ImplItem(&hir::ImplItem {
5029 node: hir::ImplItemKind::Method(_, body_id), ..
5031 let body = self.tcx.hir().body(body_id);
5032 if let ExprKind::Block(block, _) = &body.value.node {
5033 return Some(block.span);
5041 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
5042 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(hir::FnDecl, ast::Ident)> {
5043 let parent = self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_item(blk_id));
5044 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
5047 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
5048 fn get_node_fn_decl(&self, node: Node<'_>) -> Option<(hir::FnDecl, ast::Ident, bool)> {
5050 Node::Item(&hir::Item {
5051 ident, node: hir::ItemKind::Fn(ref decl, ..), ..
5052 }) => decl.clone().and_then(|decl| {
5053 // This is less than ideal, it will not suggest a return type span on any
5054 // method called `main`, regardless of whether it is actually the entry point,
5055 // but it will still present it as the reason for the expected type.
5056 Some((decl, ident, ident.name != sym::main))
5058 Node::TraitItem(&hir::TraitItem {
5059 ident, node: hir::TraitItemKind::Method(hir::MethodSig {
5062 }) => decl.clone().and_then(|decl| Some((decl, ident, true))),
5063 Node::ImplItem(&hir::ImplItem {
5064 ident, node: hir::ImplItemKind::Method(hir::MethodSig {
5067 }) => decl.clone().and_then(|decl| Some((decl, ident, false))),
5072 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
5073 /// suggestion can be made, `None` otherwise.
5074 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(hir::FnDecl, bool)> {
5075 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
5076 // `while` before reaching it, as block tail returns are not available in them.
5077 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
5078 let parent = self.tcx.hir().get_by_hir_id(blk_id);
5079 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
5083 /// On implicit return expressions with mismatched types, provides the following suggestions:
5085 /// - Points out the method's return type as the reason for the expected type.
5086 /// - Possible missing semicolon.
5087 /// - Possible missing return type if the return type is the default, and not `fn main()`.
5088 pub fn suggest_mismatched_types_on_tail(
5090 err: &mut DiagnosticBuilder<'tcx>,
5091 expression: &'tcx hir::Expr,
5097 self.suggest_missing_semicolon(err, expression, expected, cause_span);
5098 let mut pointing_at_return_type = false;
5099 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
5100 pointing_at_return_type = self.suggest_missing_return_type(
5101 err, &fn_decl, expected, found, can_suggest);
5103 self.suggest_ref_or_into(err, expression, expected, found);
5104 pointing_at_return_type
5107 pub fn suggest_ref_or_into(
5109 err: &mut DiagnosticBuilder<'tcx>,
5114 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
5115 err.span_suggestion(
5119 Applicability::MachineApplicable,
5121 } else if !self.check_for_cast(err, expr, found, expected) {
5122 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
5126 let methods = self.get_conversion_methods(expr.span, expected, found);
5127 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
5128 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
5129 .filter_map(|(receiver, method)| {
5130 let method_call = format!(".{}()", method.ident);
5131 if receiver.ends_with(&method_call) {
5132 None // do not suggest code that is already there (#53348)
5134 let method_call_list = [".to_vec()", ".to_string()"];
5135 let sugg = if receiver.ends_with(".clone()")
5136 && method_call_list.contains(&method_call.as_str()) {
5137 let max_len = receiver.rfind(".").unwrap();
5138 format!("{}{}", &receiver[..max_len], method_call)
5140 format!("{}{}", receiver, method_call)
5142 Some(if is_struct_pat_shorthand_field {
5143 format!("{}: {}", receiver, sugg)
5149 if suggestions.peek().is_some() {
5150 err.span_suggestions(
5152 "try using a conversion method",
5154 Applicability::MaybeIncorrect,
5161 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
5165 /// bar_that_returns_u32()
5169 /// This routine checks if the return expression in a block would make sense on its own as a
5170 /// statement and the return type has been left as default or has been specified as `()`. If so,
5171 /// it suggests adding a semicolon.
5172 fn suggest_missing_semicolon(
5174 err: &mut DiagnosticBuilder<'tcx>,
5175 expression: &'tcx hir::Expr,
5179 if expected.is_unit() {
5180 // `BlockTailExpression` only relevant if the tail expr would be
5181 // useful on its own.
5182 match expression.node {
5183 ExprKind::Call(..) |
5184 ExprKind::MethodCall(..) |
5185 ExprKind::While(..) |
5186 ExprKind::Loop(..) |
5187 ExprKind::Match(..) |
5188 ExprKind::Block(..) => {
5189 let sp = self.tcx.sess.source_map().next_point(cause_span);
5190 err.span_suggestion(
5192 "try adding a semicolon",
5194 Applicability::MachineApplicable);
5201 /// A possible error is to forget to add a return type that is needed:
5205 /// bar_that_returns_u32()
5209 /// This routine checks if the return type is left as default, the method is not part of an
5210 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
5212 fn suggest_missing_return_type(
5214 err: &mut DiagnosticBuilder<'tcx>,
5215 fn_decl: &hir::FnDecl,
5220 // Only suggest changing the return type for methods that
5221 // haven't set a return type at all (and aren't `fn main()` or an impl).
5222 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
5223 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
5224 err.span_suggestion(
5226 "try adding a return type",
5227 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
5228 Applicability::MachineApplicable);
5231 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
5232 err.span_label(span, "possibly return type missing here?");
5235 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
5236 // `fn main()` must return `()`, do not suggest changing return type
5237 err.span_label(span, "expected `()` because of default return type");
5240 // expectation was caused by something else, not the default return
5241 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
5242 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
5243 // Only point to return type if the expected type is the return type, as if they
5244 // are not, the expectation must have been caused by something else.
5245 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.node);
5247 let ty = AstConv::ast_ty_to_ty(self, ty);
5248 debug!("suggest_missing_return_type: return type {:?}", ty);
5249 debug!("suggest_missing_return_type: expected type {:?}", ty);
5250 if ty.sty == expected.sty {
5251 err.span_label(sp, format!("expected `{}` because of return type",
5260 /// A common error is to add an extra semicolon:
5263 /// fn foo() -> usize {
5268 /// This routine checks if the final statement in a block is an
5269 /// expression with an explicit semicolon whose type is compatible
5270 /// with `expected_ty`. If so, it suggests removing the semicolon.
5271 fn consider_hint_about_removing_semicolon(
5273 blk: &'tcx hir::Block,
5274 expected_ty: Ty<'tcx>,
5275 err: &mut DiagnosticBuilder<'_>,
5277 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
5278 err.span_suggestion(
5280 "consider removing this semicolon",
5282 Applicability::MachineApplicable,
5287 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
5288 // Be helpful when the user wrote `{... expr;}` and
5289 // taking the `;` off is enough to fix the error.
5290 let last_stmt = blk.stmts.last()?;
5291 let last_expr = match last_stmt.node {
5292 hir::StmtKind::Semi(ref e) => e,
5295 let last_expr_ty = self.node_ty(last_expr.hir_id);
5296 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
5299 let original_span = original_sp(last_stmt.span, blk.span);
5300 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
5303 // Rewrite `SelfCtor` to `Ctor`
5304 pub fn rewrite_self_ctor(
5308 ) -> Result<Res, ErrorReported> {
5310 if let Res::SelfCtor(impl_def_id) = res {
5311 let ty = self.impl_self_ty(span, impl_def_id).ty;
5312 let adt_def = ty.ty_adt_def();
5315 Some(adt_def) if adt_def.has_ctor() => {
5316 let variant = adt_def.non_enum_variant();
5317 let ctor_def_id = variant.ctor_def_id.unwrap();
5318 Ok(Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id))
5321 let mut err = tcx.sess.struct_span_err(span,
5322 "the `Self` constructor can only be used with tuple or unit structs");
5323 if let Some(adt_def) = adt_def {
5324 match adt_def.adt_kind() {
5326 err.help("did you mean to use one of the enum's variants?");
5330 err.span_suggestion(
5332 "use curly brackets",
5333 String::from("Self { /* fields */ }"),
5334 Applicability::HasPlaceholders,
5349 // Instantiates the given path, which must refer to an item with the given
5350 // number of type parameters and type.
5351 pub fn instantiate_value_path(&self,
5352 segments: &[hir::PathSegment],
5353 self_ty: Option<Ty<'tcx>>,
5357 -> (Ty<'tcx>, Res) {
5359 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
5368 let res = match self.rewrite_self_ctor(res, span) {
5370 Err(ErrorReported) => return (tcx.types.err, res),
5372 let path_segs = match res {
5373 Res::Local(_) => vec![],
5374 Res::Def(kind, def_id) =>
5375 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
5376 _ => bug!("instantiate_value_path on {:?}", res),
5379 let mut user_self_ty = None;
5380 let mut is_alias_variant_ctor = false;
5382 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
5383 if let Some(self_ty) = self_ty {
5384 let adt_def = self_ty.ty_adt_def().unwrap();
5385 user_self_ty = Some(UserSelfTy {
5386 impl_def_id: adt_def.did,
5389 is_alias_variant_ctor = true;
5392 Res::Def(DefKind::Method, def_id)
5393 | Res::Def(DefKind::AssocConst, def_id) => {
5394 let container = tcx.associated_item(def_id).container;
5395 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
5397 ty::TraitContainer(trait_did) => {
5398 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
5400 ty::ImplContainer(impl_def_id) => {
5401 if segments.len() == 1 {
5402 // `<T>::assoc` will end up here, and so
5403 // can `T::assoc`. It this came from an
5404 // inherent impl, we need to record the
5405 // `T` for posterity (see `UserSelfTy` for
5407 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
5408 user_self_ty = Some(UserSelfTy {
5419 // Now that we have categorized what space the parameters for each
5420 // segment belong to, let's sort out the parameters that the user
5421 // provided (if any) into their appropriate spaces. We'll also report
5422 // errors if type parameters are provided in an inappropriate place.
5424 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
5425 let generics_has_err = AstConv::prohibit_generics(
5426 self, segments.iter().enumerate().filter_map(|(index, seg)| {
5427 if !generic_segs.contains(&index) || is_alias_variant_ctor {
5434 if let Res::Local(hid) = res {
5435 let ty = self.local_ty(span, hid).decl_ty;
5436 let ty = self.normalize_associated_types_in(span, &ty);
5437 self.write_ty(hir_id, ty);
5441 if generics_has_err {
5442 // Don't try to infer type parameters when prohibited generic arguments were given.
5443 user_self_ty = None;
5446 // Now we have to compare the types that the user *actually*
5447 // provided against the types that were *expected*. If the user
5448 // did not provide any types, then we want to substitute inference
5449 // variables. If the user provided some types, we may still need
5450 // to add defaults. If the user provided *too many* types, that's
5453 let mut infer_args_for_err = FxHashSet::default();
5454 for &PathSeg(def_id, index) in &path_segs {
5455 let seg = &segments[index];
5456 let generics = tcx.generics_of(def_id);
5457 // Argument-position `impl Trait` is treated as a normal generic
5458 // parameter internally, but we don't allow users to specify the
5459 // parameter's value explicitly, so we have to do some error-
5461 let suppress_errors = AstConv::check_generic_arg_count_for_call(
5466 false, // `is_method_call`
5468 if suppress_errors {
5469 infer_args_for_err.insert(index);
5470 self.set_tainted_by_errors(); // See issue #53251.
5474 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
5475 tcx.generics_of(*def_id).has_self
5476 }).unwrap_or(false);
5478 let def_id = res.def_id();
5480 // The things we are substituting into the type should not contain
5481 // escaping late-bound regions, and nor should the base type scheme.
5482 let ty = tcx.type_of(def_id);
5484 let substs = AstConv::create_substs_for_generic_args(
5490 // Provide the generic args, and whether types should be inferred.
5492 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
5495 // If we've encountered an `impl Trait`-related error, we're just
5496 // going to infer the arguments for better error messages.
5497 if !infer_args_for_err.contains(&index) {
5498 // Check whether the user has provided generic arguments.
5499 if let Some(ref data) = segments[index].args {
5500 return (Some(data), segments[index].infer_args);
5503 return (None, segments[index].infer_args);
5508 // Provide substitutions for parameters for which (valid) arguments have been provided.
5510 match (¶m.kind, arg) {
5511 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
5512 AstConv::ast_region_to_region(self, lt, Some(param)).into()
5514 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
5515 self.to_ty(ty).into()
5517 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
5518 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
5520 _ => unreachable!(),
5523 // Provide substitutions for parameters for which arguments are inferred.
5524 |substs, param, infer_args| {
5526 GenericParamDefKind::Lifetime => {
5527 self.re_infer(Some(param), span).unwrap().into()
5529 GenericParamDefKind::Type { has_default, .. } => {
5530 if !infer_args && has_default {
5531 // If we have a default, then we it doesn't matter that we're not
5532 // inferring the type arguments: we provide the default where any
5534 let default = tcx.type_of(param.def_id);
5537 default.subst_spanned(tcx, substs.unwrap(), Some(span))
5540 // If no type arguments were provided, we have to infer them.
5541 // This case also occurs as a result of some malformed input, e.g.
5542 // a lifetime argument being given instead of a type parameter.
5543 // Using inference instead of `Error` gives better error messages.
5544 self.var_for_def(span, param)
5547 GenericParamDefKind::Const => {
5548 // FIXME(const_generics:defaults)
5549 // No const parameters were provided, we have to infer them.
5550 self.var_for_def(span, param)
5555 assert!(!substs.has_escaping_bound_vars());
5556 assert!(!ty.has_escaping_bound_vars());
5558 // First, store the "user substs" for later.
5559 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
5561 // Add all the obligations that are required, substituting and
5562 // normalized appropriately.
5563 let bounds = self.instantiate_bounds(span, def_id, &substs);
5564 self.add_obligations_for_parameters(
5565 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
5568 // Substitute the values for the type parameters into the type of
5569 // the referenced item.
5570 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
5572 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
5573 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
5574 // is inherent, there is no `Self` parameter; instead, the impl needs
5575 // type parameters, which we can infer by unifying the provided `Self`
5576 // with the substituted impl type.
5577 // This also occurs for an enum variant on a type alias.
5578 let ty = tcx.type_of(impl_def_id);
5580 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
5581 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
5582 Ok(ok) => self.register_infer_ok_obligations(ok),
5584 self.tcx.sess.delay_span_bug(span, &format!(
5585 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
5593 self.check_rustc_args_require_const(def_id, hir_id, span);
5595 debug!("instantiate_value_path: type of {:?} is {:?}",
5598 self.write_substs(hir_id, substs);
5600 (ty_substituted, res)
5603 fn check_rustc_args_require_const(&self,
5607 // We're only interested in functions tagged with
5608 // #[rustc_args_required_const], so ignore anything that's not.
5609 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5613 // If our calling expression is indeed the function itself, we're good!
5614 // If not, generate an error that this can only be called directly.
5615 if let Node::Expr(expr) = self.tcx.hir().get_by_hir_id(
5616 self.tcx.hir().get_parent_node_by_hir_id(hir_id))
5618 if let ExprKind::Call(ref callee, ..) = expr.node {
5619 if callee.hir_id == hir_id {
5625 self.tcx.sess.span_err(span, "this function can only be invoked \
5626 directly, not through a function pointer");
5629 // Resolves `typ` by a single level if `typ` is a type variable.
5630 // If no resolution is possible, then an error is reported.
5631 // Numeric inference variables may be left unresolved.
5632 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5633 let ty = self.resolve_type_vars_with_obligations(ty);
5634 if !ty.is_ty_var() {
5637 if !self.is_tainted_by_errors() {
5638 self.need_type_info_err((**self).body_id, sp, ty)
5639 .note("type must be known at this point")
5642 self.demand_suptype(sp, self.tcx.types.err, ty);
5647 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5650 ctxt: BreakableCtxt<'tcx>,
5652 ) -> (BreakableCtxt<'tcx>, R) {
5655 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5656 index = enclosing_breakables.stack.len();
5657 enclosing_breakables.by_id.insert(id, index);
5658 enclosing_breakables.stack.push(ctxt);
5662 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5663 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5664 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5665 enclosing_breakables.stack.pop().expect("missing breakable context")
5670 /// Instantiate a QueryResponse in a probe context, without a
5671 /// good ObligationCause.
5672 fn probe_instantiate_query_response(
5675 original_values: &OriginalQueryValues<'tcx>,
5676 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5677 ) -> InferResult<'tcx, Ty<'tcx>>
5679 self.instantiate_query_response_and_region_obligations(
5680 &traits::ObligationCause::misc(span, self.body_id),
5686 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5687 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5688 let mut contained_in_place = false;
5690 while let hir::Node::Expr(parent_expr) =
5691 self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_node_by_hir_id(expr_id))
5693 match &parent_expr.node {
5694 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5695 if lhs.hir_id == expr_id {
5696 contained_in_place = true;
5702 expr_id = parent_expr.hir_id;
5709 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5710 let own_counts = generics.own_counts();
5712 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5718 if own_counts.types == 0 {
5722 // Make a vector of booleans initially false, set to true when used.
5723 let mut types_used = vec![false; own_counts.types];
5725 for leaf_ty in ty.walk() {
5726 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.sty {
5727 debug!("Found use of ty param num {}", index);
5728 types_used[index as usize - own_counts.lifetimes] = true;
5729 } else if let ty::Error = leaf_ty.sty {
5730 // If there is already another error, do not emit
5731 // an error for not using a type Parameter.
5732 assert!(tcx.sess.err_count() > 0);
5737 let types = generics.params.iter().filter(|param| match param.kind {
5738 ty::GenericParamDefKind::Type { .. } => true,
5741 for (&used, param) in types_used.iter().zip(types) {
5743 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5744 let span = tcx.hir().span_by_hir_id(id);
5745 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5746 .span_label(span, "unused type parameter")
5752 fn fatally_break_rust(sess: &Session) {
5753 let handler = sess.diagnostic();
5754 handler.span_bug_no_panic(
5756 "It looks like you're trying to break rust; would you like some ICE?",
5758 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5759 handler.note_without_error(
5760 "we would appreciate a joke overview: \
5761 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5763 handler.note_without_error(&format!("rustc {} running on {}",
5764 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5765 crate::session::config::host_triple(),
5769 fn potentially_plural_count(count: usize, word: &str) -> String {
5770 format!("{} {}{}", count, word, if count == 1 { "" } else { "s" })