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
1013 fn visit_fn(&mut self, _: intravisit::FnKind<'tcx>, _: &'tcx hir::FnDecl,
1014 _: hir::BodyId, _: Span, _: hir::HirId) { }
1017 /// When `check_fn` is invoked on a generator (i.e., a body that
1018 /// includes yield), it returns back some information about the yield
1020 struct GeneratorTypes<'tcx> {
1021 /// Type of value that is yielded.
1024 /// Types that are captured (see `GeneratorInterior` for more).
1027 /// Indicates if the generator is movable or static (immovable).
1028 movability: hir::GeneratorMovability,
1031 /// Helper used for fns and closures. Does the grungy work of checking a function
1032 /// body and returns the function context used for that purpose, since in the case of a fn item
1033 /// there is still a bit more to do.
1036 /// * inherited: other fields inherited from the enclosing fn (if any)
1037 fn check_fn<'a, 'tcx>(inherited: &'a Inherited<'a, 'tcx>,
1038 param_env: ty::ParamEnv<'tcx>,
1039 fn_sig: ty::FnSig<'tcx>,
1040 decl: &'tcx hir::FnDecl,
1042 body: &'tcx hir::Body,
1043 can_be_generator: Option<hir::GeneratorMovability>)
1044 -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>)
1046 let mut fn_sig = fn_sig.clone();
1048 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1050 // Create the function context. This is either derived from scratch or,
1051 // in the case of closures, based on the outer context.
1052 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1053 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1055 let declared_ret_ty = fn_sig.output();
1056 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1057 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(fn_id, &declared_ret_ty);
1058 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1059 fn_sig = fcx.tcx.mk_fn_sig(
1060 fn_sig.inputs().iter().cloned(),
1067 let span = body.value.span;
1069 if body.is_generator && can_be_generator.is_some() {
1070 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
1071 kind: TypeVariableOriginKind::TypeInference,
1074 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1075 fcx.yield_ty = Some(yield_ty);
1078 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id_from_hir_id(fn_id));
1079 let outer_hir_id = fcx.tcx.hir().as_local_hir_id(outer_def_id).unwrap();
1080 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id, }.visit_body(body);
1082 // Add formal parameters.
1083 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
1084 // Check the pattern.
1085 let binding_mode = ty::BindingMode::BindByValue(hir::Mutability::MutImmutable);
1086 fcx.check_pat_walk(&arg.pat, arg_ty, binding_mode, None);
1088 // Check that argument is Sized.
1089 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1090 // for simple cases like `fn foo(x: Trait)`,
1091 // where we would error once on the parameter as a whole, and once on the binding `x`.
1092 if arg.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1093 fcx.require_type_is_sized(arg_ty, decl.output.span(), traits::SizedArgumentType);
1096 fcx.write_ty(arg.hir_id, arg_ty);
1099 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1101 fcx.check_return_expr(&body.value);
1103 // We insert the deferred_generator_interiors entry after visiting the body.
1104 // This ensures that all nested generators appear before the entry of this generator.
1105 // resolve_generator_interiors relies on this property.
1106 let gen_ty = if can_be_generator.is_some() && body.is_generator {
1107 let interior = fcx.next_ty_var(TypeVariableOrigin {
1108 kind: TypeVariableOriginKind::MiscVariable,
1111 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior));
1112 Some(GeneratorTypes {
1113 yield_ty: fcx.yield_ty.unwrap(),
1115 movability: can_be_generator.unwrap(),
1121 // Finalize the return check by taking the LUB of the return types
1122 // we saw and assigning it to the expected return type. This isn't
1123 // really expected to fail, since the coercions would have failed
1124 // earlier when trying to find a LUB.
1126 // However, the behavior around `!` is sort of complex. In the
1127 // event that the `actual_return_ty` comes back as `!`, that
1128 // indicates that the fn either does not return or "returns" only
1129 // values of type `!`. In this case, if there is an expected
1130 // return type that is *not* `!`, that should be ok. But if the
1131 // return type is being inferred, we want to "fallback" to `!`:
1133 // let x = move || panic!();
1135 // To allow for that, I am creating a type variable with diverging
1136 // fallback. This was deemed ever so slightly better than unifying
1137 // the return value with `!` because it allows for the caller to
1138 // make more assumptions about the return type (e.g., they could do
1140 // let y: Option<u32> = Some(x());
1142 // which would then cause this return type to become `u32`, not
1144 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1145 let mut actual_return_ty = coercion.complete(&fcx);
1146 if actual_return_ty.is_never() {
1147 actual_return_ty = fcx.next_diverging_ty_var(
1148 TypeVariableOrigin {
1149 kind: TypeVariableOriginKind::DivergingFn,
1154 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1156 // Check that the main return type implements the termination trait.
1157 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1158 if let Some((def_id, EntryFnType::Main)) = fcx.tcx.entry_fn(LOCAL_CRATE) {
1159 let main_id = fcx.tcx.hir().as_local_hir_id(def_id).unwrap();
1160 if main_id == fn_id {
1161 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1162 let trait_ref = ty::TraitRef::new(term_id, substs);
1163 let return_ty_span = decl.output.span();
1164 let cause = traits::ObligationCause::new(
1165 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1167 inherited.register_predicate(
1168 traits::Obligation::new(
1169 cause, param_env, trait_ref.to_predicate()));
1174 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1175 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1176 if panic_impl_did == fcx.tcx.hir().local_def_id_from_hir_id(fn_id) {
1177 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1178 // at this point we don't care if there are duplicate handlers or if the handler has
1179 // the wrong signature as this value we'll be used when writing metadata and that
1180 // only happens if compilation succeeded
1181 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1183 if declared_ret_ty.sty != ty::Never {
1184 fcx.tcx.sess.span_err(
1186 "return type should be `!`",
1190 let inputs = fn_sig.inputs();
1191 let span = fcx.tcx.hir().span_by_hir_id(fn_id);
1192 if inputs.len() == 1 {
1193 let arg_is_panic_info = match inputs[0].sty {
1194 ty::Ref(region, ty, mutbl) => match ty.sty {
1195 ty::Adt(ref adt, _) => {
1196 adt.did == panic_info_did &&
1197 mutbl == hir::Mutability::MutImmutable &&
1198 *region != RegionKind::ReStatic
1205 if !arg_is_panic_info {
1206 fcx.tcx.sess.span_err(
1207 decl.inputs[0].span,
1208 "argument should be `&PanicInfo`",
1212 if let Node::Item(item) = fcx.tcx.hir().get_by_hir_id(fn_id) {
1213 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1214 if !generics.params.is_empty() {
1215 fcx.tcx.sess.span_err(
1217 "should have no type parameters",
1223 let span = fcx.tcx.sess.source_map().def_span(span);
1224 fcx.tcx.sess.span_err(span, "function should have one argument");
1227 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1232 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1233 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1234 if alloc_error_handler_did == fcx.tcx.hir().local_def_id_from_hir_id(fn_id) {
1235 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1236 if declared_ret_ty.sty != ty::Never {
1237 fcx.tcx.sess.span_err(
1239 "return type should be `!`",
1243 let inputs = fn_sig.inputs();
1244 let span = fcx.tcx.hir().span_by_hir_id(fn_id);
1245 if inputs.len() == 1 {
1246 let arg_is_alloc_layout = match inputs[0].sty {
1247 ty::Adt(ref adt, _) => {
1248 adt.did == alloc_layout_did
1253 if !arg_is_alloc_layout {
1254 fcx.tcx.sess.span_err(
1255 decl.inputs[0].span,
1256 "argument should be `Layout`",
1260 if let Node::Item(item) = fcx.tcx.hir().get_by_hir_id(fn_id) {
1261 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1262 if !generics.params.is_empty() {
1263 fcx.tcx.sess.span_err(
1265 "`#[alloc_error_handler]` function should have no type \
1272 let span = fcx.tcx.sess.source_map().def_span(span);
1273 fcx.tcx.sess.span_err(span, "function should have one argument");
1276 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1284 fn check_struct<'tcx>(tcx: TyCtxt<'tcx>, id: hir::HirId, span: Span) {
1285 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1286 let def = tcx.adt_def(def_id);
1287 def.destructor(tcx); // force the destructor to be evaluated
1288 check_representable(tcx, span, def_id);
1290 if def.repr.simd() {
1291 check_simd(tcx, span, def_id);
1294 check_transparent(tcx, span, def_id);
1295 check_packed(tcx, span, def_id);
1298 fn check_union<'tcx>(tcx: TyCtxt<'tcx>, id: hir::HirId, span: Span) {
1299 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1300 let def = tcx.adt_def(def_id);
1301 def.destructor(tcx); // force the destructor to be evaluated
1302 check_representable(tcx, span, def_id);
1303 check_transparent(tcx, span, def_id);
1304 check_packed(tcx, span, def_id);
1307 fn check_opaque<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, substs: SubstsRef<'tcx>, span: Span) {
1308 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1309 let mut err = struct_span_err!(
1310 tcx.sess, span, E0720,
1311 "opaque type expands to a recursive type",
1313 err.span_label(span, "expands to self-referential type");
1314 if let ty::Opaque(..) = partially_expanded_type.sty {
1315 err.note("type resolves to itself");
1317 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1323 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
1325 "check_item_type(it.hir_id={}, it.name={})",
1327 tcx.def_path_str(tcx.hir().local_def_id_from_hir_id(it.hir_id))
1329 let _indenter = indenter();
1331 // Consts can play a role in type-checking, so they are included here.
1332 hir::ItemKind::Static(..) => {
1333 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1334 tcx.typeck_tables_of(def_id);
1335 maybe_check_static_with_link_section(tcx, def_id, it.span);
1337 hir::ItemKind::Const(..) => {
1338 tcx.typeck_tables_of(tcx.hir().local_def_id_from_hir_id(it.hir_id));
1340 hir::ItemKind::Enum(ref enum_definition, _) => {
1341 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1343 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1344 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1345 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1346 let impl_def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1347 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1348 check_impl_items_against_trait(
1355 let trait_def_id = impl_trait_ref.def_id;
1356 check_on_unimplemented(tcx, trait_def_id, it);
1359 hir::ItemKind::Trait(..) => {
1360 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1361 check_on_unimplemented(tcx, def_id, it);
1363 hir::ItemKind::Struct(..) => {
1364 check_struct(tcx, it.hir_id, it.span);
1366 hir::ItemKind::Union(..) => {
1367 check_union(tcx, it.hir_id, it.span);
1369 hir::ItemKind::Existential(..) => {
1370 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1372 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1373 check_opaque(tcx, def_id, substs, it.span);
1375 hir::ItemKind::Ty(..) => {
1376 let def_id = tcx.hir().local_def_id_from_hir_id(it.hir_id);
1377 let pty_ty = tcx.type_of(def_id);
1378 let generics = tcx.generics_of(def_id);
1379 check_bounds_are_used(tcx, &generics, pty_ty);
1381 hir::ItemKind::ForeignMod(ref m) => {
1382 check_abi(tcx, it.span, m.abi);
1384 if m.abi == Abi::RustIntrinsic {
1385 for item in &m.items {
1386 intrinsic::check_intrinsic_type(tcx, item);
1388 } else if m.abi == Abi::PlatformIntrinsic {
1389 for item in &m.items {
1390 intrinsic::check_platform_intrinsic_type(tcx, item);
1393 for item in &m.items {
1394 let generics = tcx.generics_of(tcx.hir().local_def_id_from_hir_id(item.hir_id));
1395 if generics.params.len() - generics.own_counts().lifetimes != 0 {
1396 let mut err = struct_span_err!(
1400 "foreign items may not have type parameters"
1402 err.span_label(item.span, "can't have type parameters");
1403 // FIXME: once we start storing spans for type arguments, turn this into a
1406 "use specialization instead of type parameters by replacing them \
1407 with concrete types like `u32`",
1412 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.node {
1413 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1418 _ => { /* nothing to do */ }
1422 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1423 // Only restricted on wasm32 target for now
1424 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1428 // If `#[link_section]` is missing, then nothing to verify
1429 let attrs = tcx.codegen_fn_attrs(id);
1430 if attrs.link_section.is_none() {
1434 // For the wasm32 target statics with #[link_section] are placed into custom
1435 // sections of the final output file, but this isn't link custom sections of
1436 // other executable formats. Namely we can only embed a list of bytes,
1437 // nothing with pointers to anything else or relocations. If any relocation
1438 // show up, reject them here.
1439 let instance = ty::Instance::mono(tcx, id);
1440 let cid = GlobalId {
1444 let param_env = ty::ParamEnv::reveal_all();
1445 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1446 let alloc = if let ConstValue::ByRef(_, allocation) = static_.val {
1449 bug!("Matching on non-ByRef static")
1451 if alloc.relocations.len() != 0 {
1452 let msg = "statics with a custom `#[link_section]` must be a \
1453 simple list of bytes on the wasm target with no \
1454 extra levels of indirection such as references";
1455 tcx.sess.span_err(span, msg);
1460 fn check_on_unimplemented<'tcx>(tcx: TyCtxt<'tcx>, trait_def_id: DefId, item: &hir::Item) {
1461 let item_def_id = tcx.hir().local_def_id_from_hir_id(item.hir_id);
1462 // an error would be reported if this fails.
1463 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1466 fn report_forbidden_specialization<'tcx>(
1468 impl_item: &hir::ImplItem,
1471 let mut err = struct_span_err!(
1472 tcx.sess, impl_item.span, E0520,
1473 "`{}` specializes an item from a parent `impl`, but \
1474 that item is not marked `default`",
1476 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1479 match tcx.span_of_impl(parent_impl) {
1481 err.span_label(span, "parent `impl` is here");
1482 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1486 err.note(&format!("parent implementation is in crate `{}`", cname));
1493 fn check_specialization_validity<'tcx>(
1495 trait_def: &ty::TraitDef,
1496 trait_item: &ty::AssocItem,
1498 impl_item: &hir::ImplItem,
1500 let ancestors = trait_def.ancestors(tcx, impl_id);
1502 let kind = match impl_item.node {
1503 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1504 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1505 hir::ImplItemKind::Existential(..) => ty::AssocKind::Existential,
1506 hir::ImplItemKind::Type(_) => ty::AssocKind::Type
1509 let parent = ancestors.defs(tcx, trait_item.ident, kind, trait_def.def_id).nth(1)
1510 .map(|node_item| node_item.map(|parent| parent.defaultness));
1512 if let Some(parent) = parent {
1513 if tcx.impl_item_is_final(&parent) {
1514 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1520 fn check_impl_items_against_trait<'tcx>(
1524 impl_trait_ref: ty::TraitRef<'tcx>,
1525 impl_item_refs: &[hir::ImplItemRef],
1527 let impl_span = tcx.sess.source_map().def_span(impl_span);
1529 // If the trait reference itself is erroneous (so the compilation is going
1530 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1531 // isn't populated for such impls.
1532 if impl_trait_ref.references_error() { return; }
1534 // Locate trait definition and items
1535 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1536 let mut overridden_associated_type = None;
1538 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1540 // Check existing impl methods to see if they are both present in trait
1541 // and compatible with trait signature
1542 for impl_item in impl_items() {
1543 let ty_impl_item = tcx.associated_item(
1544 tcx.hir().local_def_id_from_hir_id(impl_item.hir_id));
1545 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1546 .find(|ac| Namespace::from(&impl_item.node) == Namespace::from(ac.kind) &&
1547 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1549 // Not compatible, but needed for the error message
1550 tcx.associated_items(impl_trait_ref.def_id)
1551 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1554 // Check that impl definition matches trait definition
1555 if let Some(ty_trait_item) = ty_trait_item {
1556 match impl_item.node {
1557 hir::ImplItemKind::Const(..) => {
1558 // Find associated const definition.
1559 if ty_trait_item.kind == ty::AssocKind::Const {
1560 compare_const_impl(tcx,
1566 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1567 "item `{}` is an associated const, \
1568 which doesn't match its trait `{}`",
1571 err.span_label(impl_item.span, "does not match trait");
1572 // We can only get the spans from local trait definition
1573 // Same for E0324 and E0325
1574 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1575 err.span_label(trait_span, "item in trait");
1580 hir::ImplItemKind::Method(..) => {
1581 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1582 if ty_trait_item.kind == ty::AssocKind::Method {
1583 compare_impl_method(tcx,
1590 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1591 "item `{}` is an associated method, \
1592 which doesn't match its trait `{}`",
1595 err.span_label(impl_item.span, "does not match trait");
1596 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1597 err.span_label(trait_span, "item in trait");
1602 hir::ImplItemKind::Existential(..) |
1603 hir::ImplItemKind::Type(_) => {
1604 if ty_trait_item.kind == ty::AssocKind::Type {
1605 if ty_trait_item.defaultness.has_value() {
1606 overridden_associated_type = Some(impl_item);
1609 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1610 "item `{}` is an associated type, \
1611 which doesn't match its trait `{}`",
1614 err.span_label(impl_item.span, "does not match trait");
1615 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1616 err.span_label(trait_span, "item in trait");
1623 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1627 // Check for missing items from trait
1628 let mut missing_items = Vec::new();
1629 let mut invalidated_items = Vec::new();
1630 let associated_type_overridden = overridden_associated_type.is_some();
1631 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1632 let is_implemented = trait_def.ancestors(tcx, impl_id)
1633 .defs(tcx, trait_item.ident, trait_item.kind, impl_trait_ref.def_id)
1635 .map(|node_item| !node_item.node.is_from_trait())
1638 if !is_implemented && !tcx.impl_is_default(impl_id) {
1639 if !trait_item.defaultness.has_value() {
1640 missing_items.push(trait_item);
1641 } else if associated_type_overridden {
1642 invalidated_items.push(trait_item.ident);
1647 if !missing_items.is_empty() {
1648 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1649 "not all trait items implemented, missing: `{}`",
1650 missing_items.iter()
1651 .map(|trait_item| trait_item.ident.to_string())
1652 .collect::<Vec<_>>().join("`, `"));
1653 err.span_label(impl_span, format!("missing `{}` in implementation",
1654 missing_items.iter()
1655 .map(|trait_item| trait_item.ident.to_string())
1656 .collect::<Vec<_>>().join("`, `")));
1657 for trait_item in missing_items {
1658 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1659 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1661 err.note_trait_signature(trait_item.ident.to_string(),
1662 trait_item.signature(tcx));
1668 if !invalidated_items.is_empty() {
1669 let invalidator = overridden_associated_type.unwrap();
1670 span_err!(tcx.sess, invalidator.span, E0399,
1671 "the following trait items need to be reimplemented \
1672 as `{}` was overridden: `{}`",
1674 invalidated_items.iter()
1675 .map(|name| name.to_string())
1676 .collect::<Vec<_>>().join("`, `"))
1680 /// Checks whether a type can be represented in memory. In particular, it
1681 /// identifies types that contain themselves without indirection through a
1682 /// pointer, which would mean their size is unbounded.
1683 fn check_representable<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, item_def_id: DefId) -> bool {
1684 let rty = tcx.type_of(item_def_id);
1686 // Check that it is possible to represent this type. This call identifies
1687 // (1) types that contain themselves and (2) types that contain a different
1688 // recursive type. It is only necessary to throw an error on those that
1689 // contain themselves. For case 2, there must be an inner type that will be
1690 // caught by case 1.
1691 match rty.is_representable(tcx, sp) {
1692 Representability::SelfRecursive(spans) => {
1693 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1695 err.span_label(span, "recursive without indirection");
1700 Representability::Representable | Representability::ContainsRecursive => (),
1705 pub fn check_simd<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, def_id: DefId) {
1706 let t = tcx.type_of(def_id);
1707 if let ty::Adt(def, substs) = t.sty {
1708 if def.is_struct() {
1709 let fields = &def.non_enum_variant().fields;
1710 if fields.is_empty() {
1711 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1714 let e = fields[0].ty(tcx, substs);
1715 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1716 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1717 .span_label(sp, "SIMD elements must have the same type")
1722 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1723 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1725 span_err!(tcx.sess, sp, E0077,
1726 "SIMD vector element type should be machine type");
1734 fn check_packed<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, def_id: DefId) {
1735 let repr = tcx.adt_def(def_id).repr;
1737 for attr in tcx.get_attrs(def_id).iter() {
1738 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
1739 if let attr::ReprPacked(pack) = r {
1740 if pack != repr.pack {
1741 struct_span_err!(tcx.sess, sp, E0634,
1742 "type has conflicting packed representation hints").emit();
1748 struct_span_err!(tcx.sess, sp, E0587,
1749 "type has conflicting packed and align representation hints").emit();
1751 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1752 struct_span_err!(tcx.sess, sp, E0588,
1753 "packed type cannot transitively contain a `[repr(align)]` type").emit();
1758 fn check_packed_inner<'tcx>(
1761 stack: &mut Vec<DefId>,
1763 let t = tcx.type_of(def_id);
1764 if stack.contains(&def_id) {
1765 debug!("check_packed_inner: {:?} is recursive", t);
1768 if let ty::Adt(def, substs) = t.sty {
1769 if def.is_struct() || def.is_union() {
1770 if tcx.adt_def(def.did).repr.align > 0 {
1773 // push struct def_id before checking fields
1775 for field in &def.non_enum_variant().fields {
1776 let f = field.ty(tcx, substs);
1777 if let ty::Adt(def, _) = f.sty {
1778 if check_packed_inner(tcx, def.did, stack) {
1783 // only need to pop if not early out
1790 fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, def_id: DefId) {
1791 let adt = tcx.adt_def(def_id);
1792 if !adt.repr.transparent() {
1797 if !tcx.features().transparent_enums {
1798 emit_feature_err(&tcx.sess.parse_sess,
1799 sym::transparent_enums,
1801 GateIssue::Language,
1802 "transparent enums are unstable");
1804 if adt.variants.len() != 1 {
1805 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
1806 tcx.hir().span_if_local(variant.def_id).unwrap()
1808 let mut err = struct_span_err!(tcx.sess, sp, E0731,
1809 "transparent enum needs exactly one variant, but has {}",
1810 adt.variants.len());
1811 if !variant_spans.is_empty() {
1812 err.span_note(variant_spans, &format!("the following variants exist on `{}`",
1813 tcx.def_path_str(def_id)));
1816 if adt.variants.is_empty() {
1817 // Don't bother checking the fields. No variants (and thus no fields) exist.
1823 if adt.is_union() && !tcx.features().transparent_unions {
1824 emit_feature_err(&tcx.sess.parse_sess,
1825 sym::transparent_unions,
1827 GateIssue::Language,
1828 "transparent unions are unstable");
1831 // For each field, figure out if it's known to be a ZST and align(1)
1832 let field_infos = adt.all_fields().map(|field| {
1833 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
1834 let param_env = tcx.param_env(field.did);
1835 let layout = tcx.layout_of(param_env.and(ty));
1836 // We are currently checking the type this field came from, so it must be local
1837 let span = tcx.hir().span_if_local(field.did).unwrap();
1838 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
1839 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
1843 let non_zst_fields = field_infos.clone().filter(|(_span, zst, _align1)| !*zst);
1844 let non_zst_count = non_zst_fields.clone().count();
1845 if non_zst_count != 1 {
1846 let field_spans: Vec<_> = non_zst_fields.map(|(span, _zst, _align1)| span).collect();
1848 let mut err = struct_span_err!(tcx.sess, sp, E0690,
1849 "{}transparent {} needs exactly one non-zero-sized field, but has {}",
1850 if adt.is_enum() { "the variant of a " } else { "" },
1853 if !field_spans.is_empty() {
1854 err.span_note(field_spans,
1855 &format!("the following non-zero-sized fields exist on `{}`:",
1856 tcx.def_path_str(def_id)));
1860 for (span, zst, align1) in field_infos {
1862 span_err!(tcx.sess, span, E0691,
1863 "zero-sized field in transparent {} has alignment larger than 1",
1869 #[allow(trivial_numeric_casts)]
1870 pub fn check_enum<'tcx>(
1873 vs: &'tcx [hir::Variant],
1876 let def_id = tcx.hir().local_def_id_from_hir_id(id);
1877 let def = tcx.adt_def(def_id);
1878 def.destructor(tcx); // force the destructor to be evaluated
1881 let attributes = tcx.get_attrs(def_id);
1882 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
1884 tcx.sess, attr.span, E0084,
1885 "unsupported representation for zero-variant enum")
1886 .span_label(sp, "zero-variant enum")
1891 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1892 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1893 if !tcx.features().repr128 {
1894 emit_feature_err(&tcx.sess.parse_sess,
1897 GateIssue::Language,
1898 "repr with 128-bit type is unstable");
1903 if let Some(ref e) = v.node.disr_expr {
1904 tcx.typeck_tables_of(tcx.hir().local_def_id_from_hir_id(e.hir_id));
1908 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
1909 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
1910 // Check for duplicate discriminant values
1911 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
1912 let variant_did = def.variants[VariantIdx::new(i)].def_id;
1913 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
1914 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
1915 let i_span = match variant_i.node.disr_expr {
1916 Some(ref expr) => tcx.hir().span_by_hir_id(expr.hir_id),
1917 None => tcx.hir().span_by_hir_id(variant_i_hir_id)
1919 let span = match v.node.disr_expr {
1920 Some(ref expr) => tcx.hir().span_by_hir_id(expr.hir_id),
1923 struct_span_err!(tcx.sess, span, E0081,
1924 "discriminant value `{}` already exists", disr_vals[i])
1925 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1926 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
1929 disr_vals.push(discr);
1932 check_representable(tcx, sp, def_id);
1933 check_transparent(tcx, sp, def_id);
1936 fn report_unexpected_variant_res<'tcx>(
1942 span_err!(tcx.sess, span, E0533,
1943 "expected unit struct/variant or constant, found {} `{}`",
1945 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
1948 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
1949 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1953 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1954 -> &'tcx ty::GenericPredicates<'tcx>
1957 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1958 let item_id = tcx.hir().ty_param_owner(hir_id);
1959 let item_def_id = tcx.hir().local_def_id_from_hir_id(item_id);
1960 let generics = tcx.generics_of(item_def_id);
1961 let index = generics.param_def_id_to_index[&def_id];
1962 tcx.arena.alloc(ty::GenericPredicates {
1964 predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
1966 ty::Predicate::Trait(ref data)
1967 if data.skip_binder().self_ty().is_param(index) => {
1968 // HACK(eddyb) should get the original `Span`.
1969 let span = tcx.def_span(def_id);
1970 Some((predicate, span))
1980 def: Option<&ty::GenericParamDef>,
1982 ) -> Option<ty::Region<'tcx>> {
1984 Some(def) => infer::EarlyBoundRegion(span, def.name),
1985 None => infer::MiscVariable(span)
1987 Some(self.next_region_var(v))
1990 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
1991 if let Some(param) = param {
1992 if let UnpackedKind::Type(ty) = self.var_for_def(span, param).unpack() {
1997 self.next_ty_var(TypeVariableOrigin {
1998 kind: TypeVariableOriginKind::TypeInference,
2007 param: Option<&ty::GenericParamDef>,
2009 ) -> &'tcx Const<'tcx> {
2010 if let Some(param) = param {
2011 if let UnpackedKind::Const(ct) = self.var_for_def(span, param).unpack() {
2016 self.next_const_var(ty, ConstVariableOrigin {
2017 kind: ConstVariableOriginKind::ConstInference,
2023 fn projected_ty_from_poly_trait_ref(&self,
2026 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2029 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2031 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2035 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2038 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2039 if ty.has_escaping_bound_vars() {
2040 ty // FIXME: normalization and escaping regions
2042 self.normalize_associated_types_in(span, &ty)
2046 fn set_tainted_by_errors(&self) {
2047 self.infcx.set_tainted_by_errors()
2050 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2051 self.write_ty(hir_id, ty)
2055 /// Controls whether the arguments are tupled. This is used for the call
2058 /// Tupling means that all call-side arguments are packed into a tuple and
2059 /// passed as a single parameter. For example, if tupling is enabled, this
2062 /// fn f(x: (isize, isize))
2064 /// Can be called as:
2071 #[derive(Clone, Eq, PartialEq)]
2072 enum TupleArgumentsFlag {
2077 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2078 pub fn new(inh: &'a Inherited<'a, 'tcx>,
2079 param_env: ty::ParamEnv<'tcx>,
2080 body_id: hir::HirId)
2081 -> FnCtxt<'a, 'tcx> {
2085 err_count_on_creation: inh.tcx.sess.err_count(),
2087 ret_coercion_span: RefCell::new(None),
2089 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2090 hir::CRATE_HIR_ID)),
2091 diverges: Cell::new(Diverges::Maybe),
2092 has_errors: Cell::new(false),
2093 enclosing_breakables: RefCell::new(EnclosingBreakables {
2095 by_id: Default::default(),
2101 pub fn sess(&self) -> &Session {
2105 pub fn err_count_since_creation(&self) -> usize {
2106 self.tcx.sess.err_count() - self.err_count_on_creation
2109 /// Produces warning on the given node, if the current point in the
2110 /// function is unreachable, and there hasn't been another warning.
2111 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2112 if self.diverges.get() == Diverges::Always &&
2113 // If span arose from a desugaring of `if` then it is the condition itself,
2114 // which diverges, that we are about to lint on. This gives suboptimal diagnostics
2115 // and so we stop here and allow the block of the `if`-expression to be linted instead.
2116 !span.is_compiler_desugaring(CompilerDesugaringKind::IfTemporary) {
2117 self.diverges.set(Diverges::WarnedAlways);
2119 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2121 let msg = format!("unreachable {}", kind);
2122 self.tcx().lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg);
2128 code: ObligationCauseCode<'tcx>)
2129 -> ObligationCause<'tcx> {
2130 ObligationCause::new(span, self.body_id, code)
2133 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2134 self.cause(span, ObligationCauseCode::MiscObligation)
2137 /// Resolves type variables in `ty` if possible. Unlike the infcx
2138 /// version (resolve_vars_if_possible), this version will
2139 /// also select obligations if it seems useful, in an effort
2140 /// to get more type information.
2141 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2142 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2144 // No Infer()? Nothing needs doing.
2145 if !ty.has_infer_types() {
2146 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2150 // If `ty` is a type variable, see whether we already know what it is.
2151 ty = self.resolve_vars_if_possible(&ty);
2152 if !ty.has_infer_types() {
2153 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2157 // If not, try resolving pending obligations as much as
2158 // possible. This can help substantially when there are
2159 // indirect dependencies that don't seem worth tracking
2161 self.select_obligations_where_possible(false);
2162 ty = self.resolve_vars_if_possible(&ty);
2164 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2168 fn record_deferred_call_resolution(&self,
2169 closure_def_id: DefId,
2170 r: DeferredCallResolution<'tcx>) {
2171 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2172 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2175 fn remove_deferred_call_resolutions(&self,
2176 closure_def_id: DefId)
2177 -> Vec<DeferredCallResolution<'tcx>>
2179 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2180 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2183 pub fn tag(&self) -> String {
2184 format!("{:p}", self)
2187 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2188 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2189 span_bug!(span, "no type for local variable {}",
2190 self.tcx.hir().hir_to_string(nid))
2195 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2196 debug!("write_ty({:?}, {:?}) in fcx {}",
2197 id, self.resolve_vars_if_possible(&ty), self.tag());
2198 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2200 if ty.references_error() {
2201 self.has_errors.set(true);
2202 self.set_tainted_by_errors();
2206 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2207 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2210 pub fn write_method_call(&self,
2212 method: MethodCallee<'tcx>) {
2213 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2216 .type_dependent_defs_mut()
2217 .insert(hir_id, Ok((DefKind::Method, method.def_id)));
2219 self.write_substs(hir_id, method.substs);
2221 // When the method is confirmed, the `method.substs` includes
2222 // parameters from not just the method, but also the impl of
2223 // the method -- in particular, the `Self` type will be fully
2224 // resolved. However, those are not something that the "user
2225 // specified" -- i.e., those types come from the inferred type
2226 // of the receiver, not something the user wrote. So when we
2227 // create the user-substs, we want to replace those earlier
2228 // types with just the types that the user actually wrote --
2229 // that is, those that appear on the *method itself*.
2231 // As an example, if the user wrote something like
2232 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2233 // type of `foo` (possibly adjusted), but we don't want to
2234 // include that. We want just the `[_, u32]` part.
2235 if !method.substs.is_noop() {
2236 let method_generics = self.tcx.generics_of(method.def_id);
2237 if !method_generics.params.is_empty() {
2238 let user_type_annotation = self.infcx.probe(|_| {
2239 let user_substs = UserSubsts {
2240 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2241 let i = param.index as usize;
2242 if i < method_generics.parent_count {
2243 self.infcx.var_for_def(DUMMY_SP, param)
2248 user_self_ty: None, // not relevant here
2251 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2257 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2258 self.write_user_type_annotation(hir_id, user_type_annotation);
2263 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2264 if !substs.is_noop() {
2265 debug!("write_substs({:?}, {:?}) in fcx {}",
2270 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2274 /// Given the substs that we just converted from the HIR, try to
2275 /// canonicalize them and store them as user-given substitutions
2276 /// (i.e., substitutions that must be respected by the NLL check).
2278 /// This should be invoked **before any unifications have
2279 /// occurred**, so that annotations like `Vec<_>` are preserved
2281 pub fn write_user_type_annotation_from_substs(
2285 substs: SubstsRef<'tcx>,
2286 user_self_ty: Option<UserSelfTy<'tcx>>,
2289 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2290 user_self_ty={:?} in fcx {}",
2291 hir_id, def_id, substs, user_self_ty, self.tag(),
2294 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2295 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2296 &UserType::TypeOf(def_id, UserSubsts {
2301 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2302 self.write_user_type_annotation(hir_id, canonicalized);
2306 pub fn write_user_type_annotation(
2309 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2312 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2313 hir_id, canonical_user_type_annotation, self.tag(),
2316 if !canonical_user_type_annotation.is_identity() {
2317 self.tables.borrow_mut().user_provided_types_mut().insert(
2318 hir_id, canonical_user_type_annotation
2321 debug!("write_user_type_annotation: skipping identity substs");
2325 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2326 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2332 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2333 Entry::Vacant(entry) => { entry.insert(adj); },
2334 Entry::Occupied(mut entry) => {
2335 debug!(" - composing on top of {:?}", entry.get());
2336 match (&entry.get()[..], &adj[..]) {
2337 // Applying any adjustment on top of a NeverToAny
2338 // is a valid NeverToAny adjustment, because it can't
2340 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2342 Adjustment { kind: Adjust::Deref(_), .. },
2343 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2345 Adjustment { kind: Adjust::Deref(_), .. },
2346 .. // Any following adjustments are allowed.
2348 // A reborrow has no effect before a dereference.
2350 // FIXME: currently we never try to compose autoderefs
2351 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2353 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2354 expr, entry.get(), adj)
2356 *entry.get_mut() = adj;
2361 /// Basically whenever we are converting from a type scheme into
2362 /// the fn body space, we always want to normalize associated
2363 /// types as well. This function combines the two.
2364 fn instantiate_type_scheme<T>(&self,
2366 substs: SubstsRef<'tcx>,
2369 where T : TypeFoldable<'tcx>
2371 let value = value.subst(self.tcx, substs);
2372 let result = self.normalize_associated_types_in(span, &value);
2373 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2380 /// As `instantiate_type_scheme`, but for the bounds found in a
2381 /// generic type scheme.
2382 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: SubstsRef<'tcx>)
2383 -> ty::InstantiatedPredicates<'tcx> {
2384 let bounds = self.tcx.predicates_of(def_id);
2385 let result = bounds.instantiate(self.tcx, substs);
2386 let result = self.normalize_associated_types_in(span, &result);
2387 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
2394 /// Replaces the opaque types from the given value with type variables,
2395 /// and records the `OpaqueTypeMap` for later use during writeback. See
2396 /// `InferCtxt::instantiate_opaque_types` for more details.
2397 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2399 parent_id: hir::HirId,
2402 let parent_def_id = self.tcx.hir().local_def_id_from_hir_id(parent_id);
2403 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2407 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2408 self.instantiate_opaque_types(
2416 let mut opaque_types = self.opaque_types.borrow_mut();
2417 for (ty, decl) in opaque_type_map {
2418 let old_value = opaque_types.insert(ty, decl);
2419 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2425 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2426 where T : TypeFoldable<'tcx>
2428 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2431 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2433 where T : TypeFoldable<'tcx>
2435 self.inh.partially_normalize_associated_types_in(span,
2441 pub fn require_type_meets(&self,
2444 code: traits::ObligationCauseCode<'tcx>,
2447 self.register_bound(
2450 traits::ObligationCause::new(span, self.body_id, code));
2453 pub fn require_type_is_sized(&self,
2456 code: traits::ObligationCauseCode<'tcx>)
2458 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
2459 self.require_type_meets(ty, span, code, lang_item);
2462 pub fn require_type_is_sized_deferred(&self,
2465 code: traits::ObligationCauseCode<'tcx>)
2467 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2470 pub fn register_bound(&self,
2473 cause: traits::ObligationCause<'tcx>)
2475 self.fulfillment_cx.borrow_mut()
2476 .register_bound(self, self.param_env, ty, def_id, cause);
2479 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2480 let t = AstConv::ast_ty_to_ty(self, ast_t);
2481 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2485 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2486 let ty = self.to_ty(ast_ty);
2487 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2489 if Self::can_contain_user_lifetime_bounds(ty) {
2490 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2491 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2492 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2498 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2499 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2500 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2503 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2504 AstConv::ast_const_to_const(self, ast_c, ty)
2507 // If the type given by the user has free regions, save it for later, since
2508 // NLL would like to enforce those. Also pass in types that involve
2509 // projections, since those can resolve to `'static` bounds (modulo #54940,
2510 // which hopefully will be fixed by the time you see this comment, dear
2511 // reader, although I have my doubts). Also pass in types with inference
2512 // types, because they may be repeated. Other sorts of things are already
2513 // sufficiently enforced with erased regions. =)
2514 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2516 T: TypeFoldable<'tcx>
2518 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2521 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2522 match self.tables.borrow().node_types().get(id) {
2524 None if self.is_tainted_by_errors() => self.tcx.types.err,
2526 let node_id = self.tcx.hir().hir_to_node_id(id);
2527 bug!("no type for node {}: {} in fcx {}",
2528 node_id, self.tcx.hir().node_to_string(node_id),
2534 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2535 /// outlive the region `r`.
2536 pub fn register_wf_obligation(&self,
2539 code: traits::ObligationCauseCode<'tcx>)
2541 // WF obligations never themselves fail, so no real need to give a detailed cause:
2542 let cause = traits::ObligationCause::new(span, self.body_id, code);
2543 self.register_predicate(traits::Obligation::new(cause,
2545 ty::Predicate::WellFormed(ty)));
2548 /// Registers obligations that all types appearing in `substs` are well-formed.
2549 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2550 for ty in substs.types() {
2551 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2555 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2556 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2557 /// trait/region obligations.
2559 /// For example, if there is a function:
2562 /// fn foo<'a,T:'a>(...)
2565 /// and a reference:
2571 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2572 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2573 pub fn add_obligations_for_parameters(&self,
2574 cause: traits::ObligationCause<'tcx>,
2575 predicates: &ty::InstantiatedPredicates<'tcx>)
2577 assert!(!predicates.has_escaping_bound_vars());
2579 debug!("add_obligations_for_parameters(predicates={:?})",
2582 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2583 self.register_predicate(obligation);
2587 // FIXME(arielb1): use this instead of field.ty everywhere
2588 // Only for fields! Returns <none> for methods>
2589 // Indifferent to privacy flags
2590 pub fn field_ty(&self,
2592 field: &'tcx ty::FieldDef,
2593 substs: SubstsRef<'tcx>)
2596 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2599 fn check_casts(&self) {
2600 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2601 for cast in deferred_cast_checks.drain(..) {
2606 fn resolve_generator_interiors(&self, def_id: DefId) {
2607 let mut generators = self.deferred_generator_interiors.borrow_mut();
2608 for (body_id, interior) in generators.drain(..) {
2609 self.select_obligations_where_possible(false);
2610 generator_interior::resolve_interior(self, def_id, body_id, interior);
2614 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2615 // Non-numerics get replaced with ! or () (depending on whether
2616 // feature(never_type) is enabled, unconstrained ints with i32,
2617 // unconstrained floats with f64.
2618 // Fallback becomes very dubious if we have encountered type-checking errors.
2619 // In that case, fallback to Error.
2620 // The return value indicates whether fallback has occurred.
2621 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2622 use rustc::ty::error::UnconstrainedNumeric::Neither;
2623 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2625 assert!(ty.is_ty_infer());
2626 let fallback = match self.type_is_unconstrained_numeric(ty) {
2627 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2628 UnconstrainedInt => self.tcx.types.i32,
2629 UnconstrainedFloat => self.tcx.types.f64,
2630 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2631 Neither => return false,
2633 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2634 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2638 fn select_all_obligations_or_error(&self) {
2639 debug!("select_all_obligations_or_error");
2640 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2641 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2645 /// Select as many obligations as we can at present.
2646 fn select_obligations_where_possible(&self, fallback_has_occurred: bool) {
2647 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2648 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2652 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2653 /// returns a type of `&T`, but the actual type we assign to the
2654 /// *expression* is `T`. So this function just peels off the return
2655 /// type by one layer to yield `T`.
2656 fn make_overloaded_place_return_type(&self,
2657 method: MethodCallee<'tcx>)
2658 -> ty::TypeAndMut<'tcx>
2660 // extract method return type, which will be &T;
2661 let ret_ty = method.sig.output();
2663 // method returns &T, but the type as visible to user is T, so deref
2664 ret_ty.builtin_deref(true).unwrap()
2667 fn lookup_indexing(&self,
2669 base_expr: &'tcx hir::Expr,
2673 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2675 // FIXME(#18741) -- this is almost but not quite the same as the
2676 // autoderef that normal method probing does. They could likely be
2679 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2680 let mut result = None;
2681 while result.is_none() && autoderef.next().is_some() {
2682 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2684 autoderef.finalize(self);
2688 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2689 /// (and otherwise adjust) `base_expr`, looking for a type which either
2690 /// supports builtin indexing or overloaded indexing.
2691 /// This loop implements one step in that search; the autoderef loop
2692 /// is implemented by `lookup_indexing`.
2693 fn try_index_step(&self,
2695 base_expr: &hir::Expr,
2696 autoderef: &Autoderef<'a, 'tcx>,
2699 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2701 let adjusted_ty = autoderef.unambiguous_final_ty(self);
2702 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2709 for &unsize in &[false, true] {
2710 let mut self_ty = adjusted_ty;
2712 // We only unsize arrays here.
2713 if let ty::Array(element_ty, _) = adjusted_ty.sty {
2714 self_ty = self.tcx.mk_slice(element_ty);
2720 // If some lookup succeeds, write callee into table and extract index/element
2721 // type from the method signature.
2722 // If some lookup succeeded, install method in table
2723 let input_ty = self.next_ty_var(TypeVariableOrigin {
2724 kind: TypeVariableOriginKind::AutoDeref,
2725 span: base_expr.span,
2727 let method = self.try_overloaded_place_op(
2728 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
2730 let result = method.map(|ok| {
2731 debug!("try_index_step: success, using overloaded indexing");
2732 let method = self.register_infer_ok_obligations(ok);
2734 let mut adjustments = autoderef.adjust_steps(self, needs);
2735 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].sty {
2736 let mutbl = match r_mutbl {
2737 hir::MutImmutable => AutoBorrowMutability::Immutable,
2738 hir::MutMutable => AutoBorrowMutability::Mutable {
2739 // Indexing can be desugared to a method call,
2740 // so maybe we could use two-phase here.
2741 // See the documentation of AllowTwoPhase for why that's
2742 // not the case today.
2743 allow_two_phase_borrow: AllowTwoPhase::No,
2746 adjustments.push(Adjustment {
2747 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
2748 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2755 adjustments.push(Adjustment {
2756 kind: Adjust::Pointer(PointerCast::Unsize),
2757 target: method.sig.inputs()[0]
2760 self.apply_adjustments(base_expr, adjustments);
2762 self.write_method_call(expr.hir_id, method);
2763 (input_ty, self.make_overloaded_place_return_type(method).ty)
2765 if result.is_some() {
2773 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
2774 let (tr, name) = match (op, is_mut) {
2775 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
2776 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
2777 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
2778 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
2780 (tr, ast::Ident::with_empty_ctxt(name))
2783 fn try_overloaded_place_op(&self,
2786 arg_tys: &[Ty<'tcx>],
2789 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
2791 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
2797 // Try Mut first, if needed.
2798 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
2799 let method = match (needs, mut_tr) {
2800 (Needs::MutPlace, Some(trait_did)) => {
2801 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
2806 // Otherwise, fall back to the immutable version.
2807 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
2808 let method = match (method, imm_tr) {
2809 (None, Some(trait_did)) => {
2810 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
2812 (method, _) => method,
2818 fn check_method_argument_types(&self,
2821 method: Result<MethodCallee<'tcx>, ()>,
2822 args_no_rcvr: &'tcx [hir::Expr],
2823 tuple_arguments: TupleArgumentsFlag,
2824 expected: Expectation<'tcx>)
2826 let has_error = match method {
2828 method.substs.references_error() || method.sig.references_error()
2833 let err_inputs = self.err_args(args_no_rcvr.len());
2835 let err_inputs = match tuple_arguments {
2836 DontTupleArguments => err_inputs,
2837 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
2840 self.check_argument_types(sp, expr_sp, &err_inputs[..], &[], args_no_rcvr,
2841 false, tuple_arguments, None);
2842 return self.tcx.types.err;
2845 let method = method.unwrap();
2846 // HACK(eddyb) ignore self in the definition (see above).
2847 let expected_arg_tys = self.expected_inputs_for_expected_output(
2850 method.sig.output(),
2851 &method.sig.inputs()[1..]
2853 self.check_argument_types(sp, expr_sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2854 args_no_rcvr, method.sig.c_variadic, tuple_arguments,
2855 self.tcx.hir().span_if_local(method.def_id));
2859 fn self_type_matches_expected_vid(
2861 trait_ref: ty::PolyTraitRef<'tcx>,
2862 expected_vid: ty::TyVid,
2864 let self_ty = self.shallow_resolve(trait_ref.self_ty());
2866 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
2867 trait_ref, self_ty, expected_vid
2870 ty::Infer(ty::TyVar(found_vid)) => {
2871 // FIXME: consider using `sub_root_var` here so we
2872 // can see through subtyping.
2873 let found_vid = self.root_var(found_vid);
2874 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
2875 expected_vid == found_vid
2881 fn obligations_for_self_ty<'b>(&'b self, self_ty: ty::TyVid)
2882 -> impl Iterator<Item=(ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
2883 + Captures<'tcx> + 'b
2885 // FIXME: consider using `sub_root_var` here so we
2886 // can see through subtyping.
2887 let ty_var_root = self.root_var(self_ty);
2888 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
2889 self_ty, ty_var_root,
2890 self.fulfillment_cx.borrow().pending_obligations());
2894 .pending_obligations()
2896 .filter_map(move |obligation| match obligation.predicate {
2897 ty::Predicate::Projection(ref data) =>
2898 Some((data.to_poly_trait_ref(self.tcx), obligation)),
2899 ty::Predicate::Trait(ref data) =>
2900 Some((data.to_poly_trait_ref(), obligation)),
2901 ty::Predicate::Subtype(..) => None,
2902 ty::Predicate::RegionOutlives(..) => None,
2903 ty::Predicate::TypeOutlives(..) => None,
2904 ty::Predicate::WellFormed(..) => None,
2905 ty::Predicate::ObjectSafe(..) => None,
2906 ty::Predicate::ConstEvaluatable(..) => None,
2907 // N.B., this predicate is created by breaking down a
2908 // `ClosureType: FnFoo()` predicate, where
2909 // `ClosureType` represents some `Closure`. It can't
2910 // possibly be referring to the current closure,
2911 // because we haven't produced the `Closure` for
2912 // this closure yet; this is exactly why the other
2913 // code is looking for a self type of a unresolved
2914 // inference variable.
2915 ty::Predicate::ClosureKind(..) => None,
2916 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
2919 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
2920 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
2921 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
2925 /// Generic function that factors out common logic from function calls,
2926 /// method calls and overloaded operators.
2927 fn check_argument_types(&self,
2930 fn_inputs: &[Ty<'tcx>],
2931 expected_arg_tys: &[Ty<'tcx>],
2932 args: &'tcx [hir::Expr],
2934 tuple_arguments: TupleArgumentsFlag,
2935 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,
3200 expr: &'tcx hir::Expr,
3201 expected: Ty<'tcx>) {
3202 let ty = self.check_expr_with_hint(expr, expected);
3203 self.demand_eqtype(expr.span, expected, ty);
3206 pub fn check_expr_has_type_or_error(&self,
3207 expr: &'tcx hir::Expr,
3208 expected: Ty<'tcx>) -> Ty<'tcx> {
3209 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected))
3212 fn check_expr_meets_expectation_or_error(&self,
3213 expr: &'tcx hir::Expr,
3214 expected: Expectation<'tcx>) -> Ty<'tcx> {
3215 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
3216 let mut ty = self.check_expr_with_expectation(expr, expected);
3218 // While we don't allow *arbitrary* coercions here, we *do* allow
3219 // coercions from ! to `expected`.
3221 assert!(!self.tables.borrow().adjustments().contains_key(expr.hir_id),
3222 "expression with never type wound up being adjusted");
3223 let adj_ty = self.next_diverging_ty_var(
3224 TypeVariableOrigin {
3225 kind: TypeVariableOriginKind::AdjustmentType,
3229 self.apply_adjustments(expr, vec![Adjustment {
3230 kind: Adjust::NeverToAny,
3236 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
3237 let expr = match &expr.node {
3238 ExprKind::DropTemps(expr) => expr,
3241 // Error possibly reported in `check_assign` so avoid emitting error again.
3242 err.emit_unless(self.is_assign_to_bool(expr, expected_ty));
3247 fn check_expr_coercable_to_type(&self,
3248 expr: &'tcx hir::Expr,
3249 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,
3256 expr: &'tcx hir::Expr,
3257 expected: Ty<'tcx>) -> Ty<'tcx> {
3258 self.check_expr_with_expectation(expr, ExpectHasType(expected))
3261 fn check_expr_with_expectation(&self,
3262 expr: &'tcx hir::Expr,
3263 expected: Expectation<'tcx>) -> Ty<'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(&self,
3346 expr: &'tcx hir::Expr,
3347 segment: &hir::PathSegment,
3349 args: &'tcx [hir::Expr],
3350 expected: Expectation<'tcx>,
3351 needs: Needs) -> Ty<'tcx> {
3352 let rcvr = &args[0];
3353 let rcvr_t = self.check_expr_with_needs(&rcvr, needs);
3354 // no need to check for bot/err -- callee does that
3355 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
3357 let method = match self.lookup_method(rcvr_t,
3363 self.write_method_call(expr.hir_id, method);
3367 if segment.ident.name != kw::Invalid {
3368 self.report_method_error(span,
3371 SelfSource::MethodCall(rcvr),
3379 // Call the generic checker.
3380 self.check_method_argument_types(span,
3388 fn check_return_expr(&self, return_expr: &'tcx hir::Expr) {
3392 .unwrap_or_else(|| span_bug!(return_expr.span,
3393 "check_return_expr called outside fn body"));
3395 let ret_ty = ret_coercion.borrow().expected_ty();
3396 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty.clone());
3397 ret_coercion.borrow_mut()
3399 &self.cause(return_expr.span,
3400 ObligationCauseCode::ReturnType(return_expr.hir_id)),
3405 // Check field access expressions
3406 fn check_field(&self,
3407 expr: &'tcx hir::Expr,
3409 base: &'tcx hir::Expr,
3410 field: ast::Ident) -> Ty<'tcx> {
3411 let expr_t = self.check_expr_with_needs(base, needs);
3412 let expr_t = self.structurally_resolved_type(base.span,
3414 let mut private_candidate = None;
3415 let mut autoderef = self.autoderef(expr.span, expr_t);
3416 while let Some((base_t, _)) = autoderef.next() {
3418 ty::Adt(base_def, substs) if !base_def.is_enum() => {
3419 debug!("struct named {:?}", base_t);
3420 let (ident, def_scope) =
3421 self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
3422 let fields = &base_def.non_enum_variant().fields;
3423 if let Some(index) = fields.iter().position(|f| f.ident.modern() == ident) {
3424 let field = &fields[index];
3425 let field_ty = self.field_ty(expr.span, field, substs);
3426 // Save the index of all fields regardless of their visibility in case
3427 // of error recovery.
3428 self.write_field_index(expr.hir_id, index);
3429 if field.vis.is_accessible_from(def_scope, self.tcx) {
3430 let adjustments = autoderef.adjust_steps(self, needs);
3431 self.apply_adjustments(base, adjustments);
3432 autoderef.finalize(self);
3434 self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span);
3437 private_candidate = Some((base_def.did, field_ty));
3440 ty::Tuple(ref tys) => {
3441 let fstr = field.as_str();
3442 if let Ok(index) = fstr.parse::<usize>() {
3443 if fstr == index.to_string() {
3444 if let Some(field_ty) = tys.get(index) {
3445 let adjustments = autoderef.adjust_steps(self, needs);
3446 self.apply_adjustments(base, adjustments);
3447 autoderef.finalize(self);
3449 self.write_field_index(expr.hir_id, index);
3450 return field_ty.expect_ty();
3458 autoderef.unambiguous_final_ty(self);
3460 if let Some((did, field_ty)) = private_candidate {
3461 let struct_path = self.tcx().def_path_str(did);
3462 let mut err = struct_span_err!(self.tcx().sess, expr.span, E0616,
3463 "field `{}` of struct `{}` is private",
3464 field, struct_path);
3465 // Also check if an accessible method exists, which is often what is meant.
3466 if self.method_exists(field, expr_t, expr.hir_id, false)
3467 && !self.expr_in_place(expr.hir_id)
3469 self.suggest_method_call(
3471 &format!("a method `{}` also exists, call it with parentheses", field),
3479 } else if field.name == kw::Invalid {
3480 self.tcx().types.err
3481 } else if self.method_exists(field, expr_t, expr.hir_id, true) {
3482 let mut err = type_error_struct!(self.tcx().sess, field.span, expr_t, E0615,
3483 "attempted to take value of method `{}` on type `{}`",
3486 if !self.expr_in_place(expr.hir_id) {
3487 self.suggest_method_call(
3489 "use parentheses to call the method",
3495 err.help("methods are immutable and cannot be assigned to");
3499 self.tcx().types.err
3501 if !expr_t.is_primitive_ty() {
3502 let mut err = self.no_such_field_err(field.span, field, expr_t);
3505 ty::Adt(def, _) if !def.is_enum() => {
3506 if let Some(suggested_field_name) =
3507 Self::suggest_field_name(def.non_enum_variant(),
3508 &field.as_str(), vec![]) {
3509 err.span_suggestion(
3511 "a field with a similar name exists",
3512 suggested_field_name.to_string(),
3513 Applicability::MaybeIncorrect,
3516 err.span_label(field.span, "unknown field");
3517 let struct_variant_def = def.non_enum_variant();
3518 let field_names = self.available_field_names(struct_variant_def);
3519 if !field_names.is_empty() {
3520 err.note(&format!("available fields are: {}",
3521 self.name_series_display(field_names)));
3525 ty::Array(_, len) => {
3526 if let (Some(len), Ok(user_index)) = (
3527 len.assert_usize(self.tcx),
3528 field.as_str().parse::<u64>()
3530 let base = self.tcx.sess.source_map()
3531 .span_to_snippet(base.span)
3533 self.tcx.hir().hir_to_pretty_string(base.hir_id));
3534 let help = "instead of using tuple indexing, use array indexing";
3535 let suggestion = format!("{}[{}]", base, field);
3536 let applicability = if len < user_index {
3537 Applicability::MachineApplicable
3539 Applicability::MaybeIncorrect
3541 err.span_suggestion(
3542 expr.span, help, suggestion, applicability
3547 let base = self.tcx.sess.source_map()
3548 .span_to_snippet(base.span)
3549 .unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
3550 let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
3551 let suggestion = format!("(*{}).{}", base, field);
3552 err.span_suggestion(
3556 Applicability::MaybeIncorrect,
3563 type_error_struct!(self.tcx().sess, field.span, expr_t, E0610,
3564 "`{}` is a primitive type and therefore doesn't have fields",
3567 self.tcx().types.err
3571 // Return an hint about the closest match in field names
3572 fn suggest_field_name(variant: &'tcx ty::VariantDef,
3574 skip: Vec<LocalInternedString>)
3576 let names = variant.fields.iter().filter_map(|field| {
3577 // ignore already set fields and private fields from non-local crates
3578 if skip.iter().any(|x| *x == field.ident.as_str()) ||
3579 (!variant.def_id.is_local() && field.vis != Visibility::Public)
3583 Some(&field.ident.name)
3587 find_best_match_for_name(names, field, None)
3590 fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<ast::Name> {
3591 variant.fields.iter().filter(|field| {
3593 self.tcx.adjust_ident_and_get_scope(field.ident, variant.def_id, self.body_id).1;
3594 field.vis.is_accessible_from(def_scope, self.tcx)
3596 .map(|field| field.ident.name)
3600 fn name_series_display(&self, names: Vec<ast::Name>) -> String {
3601 // dynamic limit, to never omit just one field
3602 let limit = if names.len() == 6 { 6 } else { 5 };
3603 let mut display = names.iter().take(limit)
3604 .map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
3605 if names.len() > limit {
3606 display = format!("{} ... and {} others", display, names.len() - limit);
3611 fn no_such_field_err<T: Display>(&self, span: Span, field: T, expr_t: &ty::TyS<'_>)
3612 -> DiagnosticBuilder<'_> {
3613 type_error_struct!(self.tcx().sess, span, expr_t, E0609,
3614 "no field `{}` on type `{}`",
3618 fn report_unknown_field(
3621 variant: &'tcx ty::VariantDef,
3623 skip_fields: &[hir::Field],
3626 if variant.recovered {
3629 let mut err = self.type_error_struct_with_diag(
3631 |actual| match ty.sty {
3632 ty::Adt(adt, ..) if adt.is_enum() => {
3633 struct_span_err!(self.tcx.sess, field.ident.span, E0559,
3634 "{} `{}::{}` has no field named `{}`",
3635 kind_name, actual, variant.ident, field.ident)
3638 struct_span_err!(self.tcx.sess, field.ident.span, E0560,
3639 "{} `{}` has no field named `{}`",
3640 kind_name, actual, field.ident)
3644 // prevent all specified fields from being suggested
3645 let skip_fields = skip_fields.iter().map(|ref x| x.ident.as_str());
3646 if let Some(field_name) = Self::suggest_field_name(variant,
3647 &field.ident.as_str(),
3648 skip_fields.collect()) {
3649 err.span_suggestion(
3651 "a field with a similar name exists",
3652 field_name.to_string(),
3653 Applicability::MaybeIncorrect,
3657 ty::Adt(adt, ..) => {
3659 err.span_label(field.ident.span,
3660 format!("`{}::{}` does not have this field",
3661 ty, variant.ident));
3663 err.span_label(field.ident.span,
3664 format!("`{}` does not have this field", ty));
3666 let available_field_names = self.available_field_names(variant);
3667 if !available_field_names.is_empty() {
3668 err.note(&format!("available fields are: {}",
3669 self.name_series_display(available_field_names)));
3672 _ => bug!("non-ADT passed to report_unknown_field")
3678 fn check_expr_struct_fields(&self,
3680 expected: Expectation<'tcx>,
3681 expr_id: hir::HirId,
3683 variant: &'tcx ty::VariantDef,
3684 ast_fields: &'tcx [hir::Field],
3685 check_completeness: bool) -> bool {
3689 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3690 .get(0).cloned().unwrap_or(adt_ty);
3691 // re-link the regions that EIfEO can erase.
3692 self.demand_eqtype(span, adt_ty_hint, adt_ty);
3694 let (substs, adt_kind, kind_name) = match &adt_ty.sty {
3695 &ty::Adt(adt, substs) => {
3696 (substs, adt.adt_kind(), adt.variant_descr())
3698 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3701 let mut remaining_fields = variant.fields.iter().enumerate().map(|(i, field)|
3702 (field.ident.modern(), (i, field))
3703 ).collect::<FxHashMap<_, _>>();
3705 let mut seen_fields = FxHashMap::default();
3707 let mut error_happened = false;
3709 // Type-check each field.
3710 for field in ast_fields {
3711 let ident = tcx.adjust_ident(field.ident, variant.def_id);
3712 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
3713 seen_fields.insert(ident, field.span);
3714 self.write_field_index(field.hir_id, i);
3716 // We don't look at stability attributes on
3717 // struct-like enums (yet...), but it's definitely not
3718 // a bug to have constructed one.
3719 if adt_kind != AdtKind::Enum {
3720 tcx.check_stability(v_field.did, Some(expr_id), field.span);
3723 self.field_ty(field.span, v_field, substs)
3725 error_happened = true;
3726 if let Some(prev_span) = seen_fields.get(&ident) {
3727 let mut err = struct_span_err!(self.tcx.sess,
3730 "field `{}` specified more than once",
3733 err.span_label(field.ident.span, "used more than once");
3734 err.span_label(*prev_span, format!("first use of `{}`", ident));
3738 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3744 // Make sure to give a type to the field even if there's
3745 // an error, so we can continue type-checking.
3746 self.check_expr_coercable_to_type(&field.expr, field_type);
3749 // Make sure the programmer specified correct number of fields.
3750 if kind_name == "union" {
3751 if ast_fields.len() != 1 {
3752 tcx.sess.span_err(span, "union expressions should have exactly one field");
3754 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3755 let len = remaining_fields.len();
3757 let mut displayable_field_names = remaining_fields
3759 .map(|ident| ident.as_str())
3760 .collect::<Vec<_>>();
3762 displayable_field_names.sort();
3764 let truncated_fields_error = if len <= 3 {
3767 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3770 let remaining_fields_names = displayable_field_names.iter().take(3)
3771 .map(|n| format!("`{}`", n))
3772 .collect::<Vec<_>>()
3775 struct_span_err!(tcx.sess, span, E0063,
3776 "missing field{} {}{} in initializer of `{}`",
3777 if remaining_fields.len() == 1 { "" } else { "s" },
3778 remaining_fields_names,
3779 truncated_fields_error,
3781 .span_label(span, format!("missing {}{}",
3782 remaining_fields_names,
3783 truncated_fields_error))
3789 fn check_struct_fields_on_error(&self,
3790 fields: &'tcx [hir::Field],
3791 base_expr: &'tcx Option<P<hir::Expr>>) {
3792 for field in fields {
3793 self.check_expr(&field.expr);
3795 if let Some(ref base) = *base_expr {
3796 self.check_expr(&base);
3800 pub fn check_struct_path(&self,
3803 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3804 let path_span = match *qpath {
3805 QPath::Resolved(_, ref path) => path.span,
3806 QPath::TypeRelative(ref qself, _) => qself.span
3808 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3809 let variant = match def {
3811 self.set_tainted_by_errors();
3814 Res::Def(DefKind::Variant, _) => {
3816 ty::Adt(adt, substs) => {
3817 Some((adt.variant_of_res(def), adt.did, substs))
3819 _ => bug!("unexpected type: {:?}", ty)
3822 Res::Def(DefKind::Struct, _)
3823 | Res::Def(DefKind::Union, _)
3824 | Res::Def(DefKind::TyAlias, _)
3825 | Res::Def(DefKind::AssocTy, _)
3826 | Res::SelfTy(..) => {
3828 ty::Adt(adt, substs) if !adt.is_enum() => {
3829 Some((adt.non_enum_variant(), adt.did, substs))
3834 _ => bug!("unexpected definition: {:?}", def)
3837 if let Some((variant, did, substs)) = variant {
3838 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3839 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3841 // Check bounds on type arguments used in the path.
3842 let bounds = self.instantiate_bounds(path_span, did, substs);
3843 let cause = traits::ObligationCause::new(path_span, self.body_id,
3844 traits::ItemObligation(did));
3845 self.add_obligations_for_parameters(cause, &bounds);
3849 struct_span_err!(self.tcx.sess, path_span, E0071,
3850 "expected struct, variant or union type, found {}",
3851 ty.sort_string(self.tcx))
3852 .span_label(path_span, "not a struct")
3858 fn check_expr_struct(&self,
3860 expected: Expectation<'tcx>,
3862 fields: &'tcx [hir::Field],
3863 base_expr: &'tcx Option<P<hir::Expr>>) -> Ty<'tcx>
3865 // Find the relevant variant
3866 let (variant, adt_ty) =
3867 if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id) {
3870 self.check_struct_fields_on_error(fields, base_expr);
3871 return self.tcx.types.err;
3874 let path_span = match *qpath {
3875 QPath::Resolved(_, ref path) => path.span,
3876 QPath::TypeRelative(ref qself, _) => qself.span
3879 // Prohibit struct expressions when non-exhaustive flag is set.
3880 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
3881 if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
3882 span_err!(self.tcx.sess, expr.span, E0639,
3883 "cannot create non-exhaustive {} using struct expression",
3884 adt.variant_descr());
3887 let error_happened = self.check_expr_struct_fields(adt_ty, expected, expr.hir_id, path_span,
3888 variant, fields, base_expr.is_none());
3889 if let &Some(ref base_expr) = base_expr {
3890 // If check_expr_struct_fields hit an error, do not attempt to populate
3891 // the fields with the base_expr. This could cause us to hit errors later
3892 // when certain fields are assumed to exist that in fact do not.
3893 if !error_happened {
3894 self.check_expr_has_type_or_error(base_expr, adt_ty);
3896 ty::Adt(adt, substs) if adt.is_struct() => {
3897 let fru_field_types = adt.non_enum_variant().fields.iter().map(|f| {
3898 self.normalize_associated_types_in(expr.span, &f.ty(self.tcx, substs))
3903 .fru_field_types_mut()
3904 .insert(expr.hir_id, fru_field_types);
3907 span_err!(self.tcx.sess, base_expr.span, E0436,
3908 "functional record update syntax requires a struct");
3913 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
3919 /// If an expression has any sub-expressions that result in a type error,
3920 /// inspecting that expression's type with `ty.references_error()` will return
3921 /// true. Likewise, if an expression is known to diverge, inspecting its
3922 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3923 /// strict, _|_ can appear in the type of an expression that does not,
3924 /// itself, diverge: for example, fn() -> _|_.)
3925 /// Note that inspecting a type's structure *directly* may expose the fact
3926 /// that there are actually multiple representations for `Error`, so avoid
3927 /// that when err needs to be handled differently.
3928 fn check_expr_with_expectation_and_needs(&self,
3929 expr: &'tcx hir::Expr,
3930 expected: Expectation<'tcx>,
3931 needs: Needs) -> Ty<'tcx> {
3932 debug!(">> type-checking: expr={:?} expected={:?}",
3935 // Warn for expressions after diverging siblings.
3936 self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
3938 // Hide the outer diverging and has_errors flags.
3939 let old_diverges = self.diverges.get();
3940 let old_has_errors = self.has_errors.get();
3941 self.diverges.set(Diverges::Maybe);
3942 self.has_errors.set(false);
3944 let ty = self.check_expr_kind(expr, expected, needs);
3946 // Warn for non-block expressions with diverging children.
3948 ExprKind::Block(..) |
3949 ExprKind::Loop(..) | ExprKind::While(..) |
3950 ExprKind::Match(..) => {}
3952 _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression")
3955 // Any expression that produces a value of type `!` must have diverged
3957 self.diverges.set(self.diverges.get() | Diverges::Always);
3960 // Record the type, which applies it effects.
3961 // We need to do this after the warning above, so that
3962 // we don't warn for the diverging expression itself.
3963 self.write_ty(expr.hir_id, ty);
3965 // Combine the diverging and has_error flags.
3966 self.diverges.set(self.diverges.get() | old_diverges);
3967 self.has_errors.set(self.has_errors.get() | old_has_errors);
3969 debug!("type of {} is...", self.tcx.hir().hir_to_string(expr.hir_id));
3970 debug!("... {:?}, expected is {:?}", ty, expected);
3977 expr: &'tcx hir::Expr,
3978 expected: Expectation<'tcx>,
3982 "check_expr_kind(expr={:?}, expected={:?}, needs={:?})",
3989 let id = expr.hir_id;
3991 ExprKind::Box(ref subexpr) => {
3992 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
3994 ty::Adt(def, _) if def.is_box()
3995 => Expectation::rvalue_hint(self, ty.boxed_ty()),
3999 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
4000 tcx.mk_box(referent_ty)
4003 ExprKind::Lit(ref lit) => {
4004 self.check_lit(&lit, expected)
4006 ExprKind::Binary(op, ref lhs, ref rhs) => {
4007 self.check_binop(expr, op, lhs, rhs)
4009 ExprKind::AssignOp(op, ref lhs, ref rhs) => {
4010 self.check_binop_assign(expr, op, lhs, rhs)
4012 ExprKind::Unary(unop, ref oprnd) => {
4013 let expected_inner = match unop {
4014 hir::UnNot | hir::UnNeg => {
4021 let needs = match unop {
4022 hir::UnDeref => needs,
4025 let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd,
4029 if !oprnd_t.references_error() {
4030 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
4033 if let Some(mt) = oprnd_t.builtin_deref(true) {
4035 } else if let Some(ok) = self.try_overloaded_deref(
4036 expr.span, oprnd_t, needs) {
4037 let method = self.register_infer_ok_obligations(ok);
4038 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].sty {
4039 let mutbl = match mutbl {
4040 hir::MutImmutable => AutoBorrowMutability::Immutable,
4041 hir::MutMutable => AutoBorrowMutability::Mutable {
4042 // (It shouldn't actually matter for unary ops whether
4043 // we enable two-phase borrows or not, since a unary
4044 // op has no additional operands.)
4045 allow_two_phase_borrow: AllowTwoPhase::No,
4048 self.apply_adjustments(oprnd, vec![Adjustment {
4049 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
4050 target: method.sig.inputs()[0]
4053 oprnd_t = self.make_overloaded_place_return_type(method).ty;
4054 self.write_method_call(expr.hir_id, method);
4056 let mut err = type_error_struct!(
4061 "type `{}` cannot be dereferenced",
4064 let sp = tcx.sess.source_map().start_point(expr.span);
4065 if let Some(sp) = tcx.sess.parse_sess.ambiguous_block_expr_parse
4068 tcx.sess.parse_sess.expr_parentheses_needed(
4075 oprnd_t = tcx.types.err;
4079 let result = self.check_user_unop(expr, oprnd_t, unop);
4080 // If it's builtin, we can reuse the type, this helps inference.
4081 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::Bool) {
4086 let result = self.check_user_unop(expr, oprnd_t, unop);
4087 // If it's builtin, we can reuse the type, this helps inference.
4088 if !oprnd_t.is_numeric() {
4096 ExprKind::AddrOf(mutbl, ref oprnd) => {
4097 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
4099 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
4100 if oprnd.is_place_expr() {
4101 // Places may legitimately have unsized types.
4102 // For example, dereferences of a fat pointer and
4103 // the last field of a struct can be unsized.
4106 Expectation::rvalue_hint(self, ty)
4112 let needs = Needs::maybe_mut_place(mutbl);
4113 let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs);
4115 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
4116 if tm.ty.references_error() {
4119 // Note: at this point, we cannot say what the best lifetime
4120 // is to use for resulting pointer. We want to use the
4121 // shortest lifetime possible so as to avoid spurious borrowck
4122 // errors. Moreover, the longest lifetime will depend on the
4123 // precise details of the value whose address is being taken
4124 // (and how long it is valid), which we don't know yet until type
4125 // inference is complete.
4127 // Therefore, here we simply generate a region variable. The
4128 // region inferencer will then select the ultimate value.
4129 // Finally, borrowck is charged with guaranteeing that the
4130 // value whose address was taken can actually be made to live
4131 // as long as it needs to live.
4132 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
4133 tcx.mk_ref(region, tm)
4136 ExprKind::Path(ref qpath) => {
4137 let (res, opt_ty, segs) = self.resolve_ty_and_res_ufcs(qpath, expr.hir_id,
4139 let ty = match res {
4141 self.set_tainted_by_errors();
4144 Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
4145 report_unexpected_variant_res(tcx, res, expr.span, qpath);
4148 _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, id).0,
4151 if let ty::FnDef(..) = ty.sty {
4152 let fn_sig = ty.fn_sig(tcx);
4153 if !tcx.features().unsized_locals {
4154 // We want to remove some Sized bounds from std functions,
4155 // but don't want to expose the removal to stable Rust.
4156 // i.e., we don't want to allow
4162 // to work in stable even if the Sized bound on `drop` is relaxed.
4163 for i in 0..fn_sig.inputs().skip_binder().len() {
4164 // We just want to check sizedness, so instead of introducing
4165 // placeholder lifetimes with probing, we just replace higher lifetimes
4167 let input = self.replace_bound_vars_with_fresh_vars(
4169 infer::LateBoundRegionConversionTime::FnCall,
4170 &fn_sig.input(i)).0;
4171 self.require_type_is_sized_deferred(input, expr.span,
4172 traits::SizedArgumentType);
4175 // Here we want to prevent struct constructors from returning unsized types.
4176 // There were two cases this happened: fn pointer coercion in stable
4177 // and usual function call in presense of unsized_locals.
4178 // Also, as we just want to check sizedness, instead of introducing
4179 // placeholder lifetimes with probing, we just replace higher lifetimes
4181 let output = self.replace_bound_vars_with_fresh_vars(
4183 infer::LateBoundRegionConversionTime::FnCall,
4184 &fn_sig.output()).0;
4185 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
4188 // We always require that the type provided as the value for
4189 // a type parameter outlives the moment of instantiation.
4190 let substs = self.tables.borrow().node_substs(expr.hir_id);
4191 self.add_wf_bounds(substs, expr);
4195 ExprKind::InlineAsm(_, ref outputs, ref inputs) => {
4196 for expr in outputs.iter().chain(inputs.iter()) {
4197 self.check_expr(expr);
4201 ExprKind::Break(destination, ref expr_opt) => {
4202 if let Ok(target_id) = destination.target_id {
4204 if let Some(ref e) = *expr_opt {
4205 // If this is a break with a value, we need to type-check
4206 // the expression. Get an expected type from the loop context.
4207 let opt_coerce_to = {
4208 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4209 enclosing_breakables.find_breakable(target_id)
4212 .map(|coerce| coerce.expected_ty())
4215 // If the loop context is not a `loop { }`, then break with
4216 // a value is illegal, and `opt_coerce_to` will be `None`.
4217 // Just set expectation to error in that case.
4218 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
4220 // Recurse without `enclosing_breakables` borrowed.
4221 e_ty = self.check_expr_with_hint(e, coerce_to);
4222 cause = self.misc(e.span);
4224 // Otherwise, this is a break *without* a value. That's
4225 // always legal, and is equivalent to `break ()`.
4226 e_ty = tcx.mk_unit();
4227 cause = self.misc(expr.span);
4230 // Now that we have type-checked `expr_opt`, borrow
4231 // the `enclosing_loops` field and let's coerce the
4232 // type of `expr_opt` into what is expected.
4233 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4234 let ctxt = enclosing_breakables.find_breakable(target_id);
4235 if let Some(ref mut coerce) = ctxt.coerce {
4236 if let Some(ref e) = *expr_opt {
4237 coerce.coerce(self, &cause, e, e_ty);
4239 assert!(e_ty.is_unit());
4240 coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
4243 // If `ctxt.coerce` is `None`, we can just ignore
4244 // the type of the expresison. This is because
4245 // either this was a break *without* a value, in
4246 // which case it is always a legal type (`()`), or
4247 // else an error would have been flagged by the
4248 // `loops` pass for using break with an expression
4249 // where you are not supposed to.
4250 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
4253 ctxt.may_break = true;
4255 // the type of a `break` is always `!`, since it diverges
4258 // Otherwise, we failed to find the enclosing loop;
4259 // this can only happen if the `break` was not
4260 // inside a loop at all, which is caught by the
4261 // loop-checking pass.
4262 if self.tcx.sess.err_count() == 0 {
4263 self.tcx.sess.delay_span_bug(expr.span,
4264 "break was outside loop, but no error was emitted");
4267 // We still need to assign a type to the inner expression to
4268 // prevent the ICE in #43162.
4269 if let Some(ref e) = *expr_opt {
4270 self.check_expr_with_hint(e, tcx.types.err);
4272 // ... except when we try to 'break rust;'.
4273 // ICE this expression in particular (see #43162).
4274 if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.node {
4275 if path.segments.len() == 1 &&
4276 path.segments[0].ident.name == sym::rust {
4277 fatally_break_rust(self.tcx.sess);
4281 // There was an error; make type-check fail.
4286 ExprKind::Continue(destination) => {
4287 if destination.target_id.is_ok() {
4290 // There was an error; make type-check fail.
4294 ExprKind::Ret(ref expr_opt) => {
4295 if self.ret_coercion.is_none() {
4296 struct_span_err!(self.tcx.sess, expr.span, E0572,
4297 "return statement outside of function body").emit();
4298 } else if let Some(ref e) = *expr_opt {
4299 if self.ret_coercion_span.borrow().is_none() {
4300 *self.ret_coercion_span.borrow_mut() = Some(e.span);
4302 self.check_return_expr(e);
4304 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
4305 if self.ret_coercion_span.borrow().is_none() {
4306 *self.ret_coercion_span.borrow_mut() = Some(expr.span);
4308 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
4309 if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
4310 coercion.coerce_forced_unit(
4315 fn_decl.output.span(),
4317 "expected `{}` because of this return type",
4325 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
4330 ExprKind::Assign(ref lhs, ref rhs) => {
4331 self.check_assign(expr, expected, lhs, rhs)
4333 ExprKind::While(ref cond, ref body, _) => {
4334 let ctxt = BreakableCtxt {
4335 // cannot use break with a value from a while loop
4337 may_break: false, // Will get updated if/when we find a `break`.
4340 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
4341 self.check_expr_has_type_or_error(&cond, tcx.types.bool);
4342 let cond_diverging = self.diverges.get();
4343 self.check_block_no_value(&body);
4345 // We may never reach the body so it diverging means nothing.
4346 self.diverges.set(cond_diverging);
4350 // No way to know whether it's diverging because
4351 // of a `break` or an outer `break` or `return`.
4352 self.diverges.set(Diverges::Maybe);
4357 ExprKind::Loop(ref body, _, source) => {
4358 let coerce = match source {
4359 // you can only use break with a value from a normal `loop { }`
4360 hir::LoopSource::Loop => {
4361 let coerce_to = expected.coercion_target_type(self, body.span);
4362 Some(CoerceMany::new(coerce_to))
4365 hir::LoopSource::WhileLet |
4366 hir::LoopSource::ForLoop => {
4371 let ctxt = BreakableCtxt {
4373 may_break: false, // Will get updated if/when we find a `break`.
4376 let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
4377 self.check_block_no_value(&body);
4381 // No way to know whether it's diverging because
4382 // of a `break` or an outer `break` or `return`.
4383 self.diverges.set(Diverges::Maybe);
4386 // If we permit break with a value, then result type is
4387 // the LUB of the breaks (possibly ! if none); else, it
4388 // is nil. This makes sense because infinite loops
4389 // (which would have type !) are only possible iff we
4390 // permit break with a value [1].
4391 if ctxt.coerce.is_none() && !ctxt.may_break {
4393 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
4395 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
4397 ExprKind::Match(ref discrim, ref arms, match_src) => {
4398 self.check_match(expr, &discrim, arms, expected, match_src)
4400 ExprKind::Closure(capture, ref decl, body_id, _, gen) => {
4401 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
4403 ExprKind::Block(ref body, _) => {
4404 self.check_block_with_expected(&body, expected)
4406 ExprKind::Call(ref callee, ref args) => {
4407 self.check_call(expr, &callee, args, expected)
4409 ExprKind::MethodCall(ref segment, span, ref args) => {
4410 self.check_method_call(expr, segment, span, args, expected, needs)
4412 ExprKind::Cast(ref e, ref t) => {
4413 // Find the type of `e`. Supply hints based on the type we are casting to,
4415 let t_cast = self.to_ty_saving_user_provided_ty(t);
4416 let t_cast = self.resolve_vars_if_possible(&t_cast);
4417 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
4418 let t_cast = self.resolve_vars_if_possible(&t_cast);
4420 // Eagerly check for some obvious errors.
4421 if t_expr.references_error() || t_cast.references_error() {
4424 // Defer other checks until we're done type checking.
4425 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
4426 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
4428 deferred_cast_checks.push(cast_check);
4431 Err(ErrorReported) => {
4437 ExprKind::Type(ref e, ref t) => {
4438 let ty = self.to_ty_saving_user_provided_ty(&t);
4439 self.check_expr_eq_type(&e, ty);
4442 ExprKind::DropTemps(ref e) => {
4443 self.check_expr_with_expectation(e, expected)
4445 ExprKind::Array(ref args) => {
4446 let uty = expected.to_option(self).and_then(|uty| {
4448 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
4453 let element_ty = if !args.is_empty() {
4454 let coerce_to = uty.unwrap_or_else(|| {
4455 self.next_ty_var(TypeVariableOrigin {
4456 kind: TypeVariableOriginKind::TypeInference,
4460 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
4461 assert_eq!(self.diverges.get(), Diverges::Maybe);
4463 let e_ty = self.check_expr_with_hint(e, coerce_to);
4464 let cause = self.misc(e.span);
4465 coerce.coerce(self, &cause, e, e_ty);
4467 coerce.complete(self)
4469 self.next_ty_var(TypeVariableOrigin {
4470 kind: TypeVariableOriginKind::TypeInference,
4474 tcx.mk_array(element_ty, args.len() as u64)
4476 ExprKind::Repeat(ref element, ref count) => {
4477 let count_def_id = tcx.hir().local_def_id_from_hir_id(count.hir_id);
4478 let count = if self.const_param_def_id(count).is_some() {
4479 Ok(self.to_const(count, self.tcx.type_of(count_def_id)))
4481 let param_env = ty::ParamEnv::empty();
4482 let substs = InternalSubsts::identity_for_item(tcx.global_tcx(), count_def_id);
4483 let instance = ty::Instance::resolve(
4489 let global_id = GlobalId {
4494 tcx.const_eval(param_env.and(global_id))
4497 let uty = match expected {
4498 ExpectHasType(uty) => {
4500 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
4507 let (element_ty, t) = match uty {
4509 self.check_expr_coercable_to_type(&element, uty);
4513 let ty = self.next_ty_var(TypeVariableOrigin {
4514 kind: TypeVariableOriginKind::MiscVariable,
4517 let element_ty = self.check_expr_has_type_or_error(&element, ty);
4522 if let Ok(count) = count {
4523 let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1);
4525 // For [foo, ..n] where n > 1, `foo` must have
4527 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
4528 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
4532 if element_ty.references_error() {
4534 } else if let Ok(count) = count {
4535 tcx.mk_ty(ty::Array(t, count))
4540 ExprKind::Tup(ref elts) => {
4541 let flds = expected.only_has_type(self).and_then(|ty| {
4542 let ty = self.resolve_type_vars_with_obligations(ty);
4544 ty::Tuple(ref flds) => Some(&flds[..]),
4549 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
4550 let t = match flds {
4551 Some(ref fs) if i < fs.len() => {
4552 let ety = fs[i].expect_ty();
4553 self.check_expr_coercable_to_type(&e, ety);
4557 self.check_expr_with_expectation(&e, NoExpectation)
4562 let tuple = tcx.mk_tup(elt_ts_iter);
4563 if tuple.references_error() {
4566 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
4570 ExprKind::Struct(ref qpath, ref fields, ref base_expr) => {
4571 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
4573 ExprKind::Field(ref base, field) => {
4574 self.check_field(expr, needs, &base, field)
4576 ExprKind::Index(ref base, ref idx) => {
4577 let base_t = self.check_expr_with_needs(&base, needs);
4578 let idx_t = self.check_expr(&idx);
4580 if base_t.references_error() {
4582 } else if idx_t.references_error() {
4585 let base_t = self.structurally_resolved_type(base.span, base_t);
4586 match self.lookup_indexing(expr, base, base_t, idx_t, needs) {
4587 Some((index_ty, element_ty)) => {
4588 // two-phase not needed because index_ty is never mutable
4589 self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No);
4594 type_error_struct!(tcx.sess, expr.span, base_t, E0608,
4595 "cannot index into a value of type `{}`",
4597 // Try to give some advice about indexing tuples.
4598 if let ty::Tuple(..) = base_t.sty {
4599 let mut needs_note = true;
4600 // If the index is an integer, we can show the actual
4601 // fixed expression:
4602 if let ExprKind::Lit(ref lit) = idx.node {
4603 if let ast::LitKind::Int(i,
4604 ast::LitIntType::Unsuffixed) = lit.node {
4605 let snip = tcx.sess.source_map().span_to_snippet(base.span);
4606 if let Ok(snip) = snip {
4607 err.span_suggestion(
4609 "to access tuple elements, use",
4610 format!("{}.{}", snip, i),
4611 Applicability::MachineApplicable,
4618 err.help("to access tuple elements, use tuple indexing \
4619 syntax (e.g., `tuple.0`)");
4628 ExprKind::Yield(ref value) => {
4629 match self.yield_ty {
4631 self.check_expr_coercable_to_type(&value, ty);
4634 struct_span_err!(self.tcx.sess, expr.span, E0627,
4635 "yield statement outside of generator literal").emit();
4640 hir::ExprKind::Err => {
4646 /// Type check assignment expression `expr` of form `lhs = rhs`.
4647 /// The expected type is `()` and is passsed to the function for the purposes of diagnostics.
4650 expr: &'tcx hir::Expr,
4651 expected: Expectation<'tcx>,
4652 lhs: &'tcx hir::Expr,
4653 rhs: &'tcx hir::Expr,
4655 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
4656 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
4658 let expected_ty = expected.coercion_target_type(self, expr.span);
4659 if expected_ty == self.tcx.types.bool {
4660 // The expected type is `bool` but this will result in `()` so we can reasonably
4661 // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
4662 // The likely cause of this is `if foo = bar { .. }`.
4663 let actual_ty = self.tcx.mk_unit();
4664 let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
4665 let msg = "try comparing for equality";
4666 let left = self.tcx.sess.source_map().span_to_snippet(lhs.span);
4667 let right = self.tcx.sess.source_map().span_to_snippet(rhs.span);
4668 if let (Ok(left), Ok(right)) = (left, right) {
4669 let help = format!("{} == {}", left, right);
4670 err.span_suggestion(expr.span, msg, help, Applicability::MaybeIncorrect);
4675 } else if !lhs.is_place_expr() {
4676 struct_span_err!(self.tcx.sess, expr.span, E0070,
4677 "invalid left-hand side expression")
4678 .span_label(expr.span, "left-hand of expression not valid")
4682 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
4684 if lhs_ty.references_error() || rhs_ty.references_error() {
4691 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4692 // The newly resolved definition is written into `type_dependent_defs`.
4693 fn finish_resolving_struct_path(&self,
4700 QPath::Resolved(ref maybe_qself, ref path) => {
4701 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4702 let ty = AstConv::res_to_ty(self, self_ty, path, true);
4705 QPath::TypeRelative(ref qself, ref segment) => {
4706 let ty = self.to_ty(qself);
4708 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.node {
4713 let result = AstConv::associated_path_to_ty(
4722 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
4723 let result = result.map(|(_, kind, def_id)| (kind, def_id));
4725 // Write back the new resolution.
4726 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, result);
4728 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
4733 /// Resolves associated value path into a base type and associated constant or method
4734 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
4735 pub fn resolve_ty_and_res_ufcs<'b>(&self,
4739 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
4741 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
4742 let (ty, qself, item_segment) = match *qpath {
4743 QPath::Resolved(ref opt_qself, ref path) => {
4745 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4746 &path.segments[..]);
4748 QPath::TypeRelative(ref qself, ref segment) => {
4749 (self.to_ty(qself), qself, segment)
4752 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
4753 // Return directly on cache hit. This is useful to avoid doubly reporting
4754 // errors with default match binding modes. See #44614.
4755 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
4756 .unwrap_or(Res::Err);
4757 return (def, Some(ty), slice::from_ref(&**item_segment));
4759 let item_name = item_segment.ident;
4760 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
4761 let result = match error {
4762 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
4763 _ => Err(ErrorReported),
4765 if item_name.name != kw::Invalid {
4766 self.report_method_error(
4770 SelfSource::QPath(qself),
4778 // Write back the new resolution.
4779 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, result);
4781 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
4783 slice::from_ref(&**item_segment),
4787 pub fn check_decl_initializer(&self,
4788 local: &'tcx hir::Local,
4789 init: &'tcx hir::Expr) -> Ty<'tcx>
4791 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
4792 // for #42640 (default match binding modes).
4795 let ref_bindings = local.pat.contains_explicit_ref_binding();
4797 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
4798 if let Some(m) = ref_bindings {
4799 // Somewhat subtle: if we have a `ref` binding in the pattern,
4800 // we want to avoid introducing coercions for the RHS. This is
4801 // both because it helps preserve sanity and, in the case of
4802 // ref mut, for soundness (issue #23116). In particular, in
4803 // the latter case, we need to be clear that the type of the
4804 // referent for the reference that results is *equal to* the
4805 // type of the place it is referencing, and not some
4806 // supertype thereof.
4807 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4808 self.demand_eqtype(init.span, local_ty, init_ty);
4811 self.check_expr_coercable_to_type(init, local_ty)
4815 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
4816 let t = self.local_ty(local.span, local.hir_id).decl_ty;
4817 self.write_ty(local.hir_id, t);
4819 if let Some(ref init) = local.init {
4820 let init_ty = self.check_decl_initializer(local, &init);
4821 if init_ty.references_error() {
4822 self.write_ty(local.hir_id, init_ty);
4826 self.check_pat_walk(
4829 ty::BindingMode::BindByValue(hir::Mutability::MutImmutable),
4832 let pat_ty = self.node_ty(local.pat.hir_id);
4833 if pat_ty.references_error() {
4834 self.write_ty(local.hir_id, pat_ty);
4838 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
4839 // Don't do all the complex logic below for `DeclItem`.
4841 hir::StmtKind::Item(..) => return,
4842 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
4845 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
4847 // Hide the outer diverging and `has_errors` flags.
4848 let old_diverges = self.diverges.get();
4849 let old_has_errors = self.has_errors.get();
4850 self.diverges.set(Diverges::Maybe);
4851 self.has_errors.set(false);
4854 hir::StmtKind::Local(ref l) => {
4855 self.check_decl_local(&l);
4858 hir::StmtKind::Item(_) => {}
4859 hir::StmtKind::Expr(ref expr) => {
4860 // Check with expected type of `()`.
4861 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit());
4863 hir::StmtKind::Semi(ref expr) => {
4864 self.check_expr(&expr);
4868 // Combine the diverging and `has_error` flags.
4869 self.diverges.set(self.diverges.get() | old_diverges);
4870 self.has_errors.set(self.has_errors.get() | old_has_errors);
4873 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
4874 let unit = self.tcx.mk_unit();
4875 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4877 // if the block produces a `!` value, that can always be
4878 // (effectively) coerced to unit.
4880 self.demand_suptype(blk.span, unit, ty);
4884 fn check_block_with_expected(&self,
4885 blk: &'tcx hir::Block,
4886 expected: Expectation<'tcx>) -> Ty<'tcx> {
4888 let mut fcx_ps = self.ps.borrow_mut();
4889 let unsafety_state = fcx_ps.recurse(blk);
4890 replace(&mut *fcx_ps, unsafety_state)
4893 // In some cases, blocks have just one exit, but other blocks
4894 // can be targeted by multiple breaks. This can happen both
4895 // with labeled blocks as well as when we desugar
4896 // a `try { ... }` expression.
4900 // 'a: { if true { break 'a Err(()); } Ok(()) }
4902 // Here we would wind up with two coercions, one from
4903 // `Err(())` and the other from the tail expression
4904 // `Ok(())`. If the tail expression is omitted, that's a
4905 // "forced unit" -- unless the block diverges, in which
4906 // case we can ignore the tail expression (e.g., `'a: {
4907 // break 'a 22; }` would not force the type of the block
4909 let tail_expr = blk.expr.as_ref();
4910 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4911 let coerce = if blk.targeted_by_break {
4912 CoerceMany::new(coerce_to_ty)
4914 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4915 Some(e) => slice::from_ref(e),
4918 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4921 let prev_diverges = self.diverges.get();
4922 let ctxt = BreakableCtxt {
4923 coerce: Some(coerce),
4927 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4928 for s in &blk.stmts {
4932 // check the tail expression **without** holding the
4933 // `enclosing_breakables` lock below.
4934 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4936 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4937 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4938 let coerce = ctxt.coerce.as_mut().unwrap();
4939 if let Some(tail_expr_ty) = tail_expr_ty {
4940 let tail_expr = tail_expr.unwrap();
4941 let cause = self.cause(tail_expr.span,
4942 ObligationCauseCode::BlockTailExpression(blk.hir_id));
4948 // Subtle: if there is no explicit tail expression,
4949 // that is typically equivalent to a tail expression
4950 // of `()` -- except if the block diverges. In that
4951 // case, there is no value supplied from the tail
4952 // expression (assuming there are no other breaks,
4953 // this implies that the type of the block will be
4956 // #41425 -- label the implicit `()` as being the
4957 // "found type" here, rather than the "expected type".
4958 if !self.diverges.get().always() {
4959 // #50009 -- Do not point at the entire fn block span, point at the return type
4960 // span, as it is the cause of the requirement, and
4961 // `consider_hint_about_removing_semicolon` will point at the last expression
4962 // if it were a relevant part of the error. This improves usability in editors
4963 // that highlight errors inline.
4964 let mut sp = blk.span;
4965 let mut fn_span = None;
4966 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4967 let ret_sp = decl.output.span();
4968 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4969 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4970 // output would otherwise be incorrect and even misleading. Make sure
4971 // the span we're aiming at correspond to a `fn` body.
4972 if block_sp == blk.span {
4974 fn_span = Some(ident.span);
4978 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4979 if let Some(expected_ty) = expected.only_has_type(self) {
4980 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4982 if let Some(fn_span) = fn_span {
4983 err.span_label(fn_span, "this function's body doesn't return");
4991 // If we can break from the block, then the block's exit is always reachable
4992 // (... as long as the entry is reachable) - regardless of the tail of the block.
4993 self.diverges.set(prev_diverges);
4996 let mut ty = ctxt.coerce.unwrap().complete(self);
4998 if self.has_errors.get() || ty.references_error() {
4999 ty = self.tcx.types.err
5002 self.write_ty(blk.hir_id, ty);
5004 *self.ps.borrow_mut() = prev;
5008 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
5009 let node = self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_item(id));
5011 Node::Item(&hir::Item {
5012 node: hir::ItemKind::Fn(_, _, _, body_id), ..
5014 Node::ImplItem(&hir::ImplItem {
5015 node: hir::ImplItemKind::Method(_, body_id), ..
5017 let body = self.tcx.hir().body(body_id);
5018 if let ExprKind::Block(block, _) = &body.value.node {
5019 return Some(block.span);
5027 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
5028 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(hir::FnDecl, ast::Ident)> {
5029 let parent = self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_item(blk_id));
5030 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
5033 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
5034 fn get_node_fn_decl(&self, node: Node<'_>) -> Option<(hir::FnDecl, ast::Ident, bool)> {
5036 Node::Item(&hir::Item {
5037 ident, node: hir::ItemKind::Fn(ref decl, ..), ..
5038 }) => decl.clone().and_then(|decl| {
5039 // This is less than ideal, it will not suggest a return type span on any
5040 // method called `main`, regardless of whether it is actually the entry point,
5041 // but it will still present it as the reason for the expected type.
5042 Some((decl, ident, ident.name != sym::main))
5044 Node::TraitItem(&hir::TraitItem {
5045 ident, node: hir::TraitItemKind::Method(hir::MethodSig {
5048 }) => decl.clone().and_then(|decl| Some((decl, ident, true))),
5049 Node::ImplItem(&hir::ImplItem {
5050 ident, node: hir::ImplItemKind::Method(hir::MethodSig {
5053 }) => decl.clone().and_then(|decl| Some((decl, ident, false))),
5058 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
5059 /// suggestion can be made, `None` otherwise.
5060 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(hir::FnDecl, bool)> {
5061 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
5062 // `while` before reaching it, as block tail returns are not available in them.
5063 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
5064 let parent = self.tcx.hir().get_by_hir_id(blk_id);
5065 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
5069 /// On implicit return expressions with mismatched types, provides the following suggestions:
5071 /// - Points out the method's return type as the reason for the expected type.
5072 /// - Possible missing semicolon.
5073 /// - Possible missing return type if the return type is the default, and not `fn main()`.
5074 pub fn suggest_mismatched_types_on_tail(
5076 err: &mut DiagnosticBuilder<'tcx>,
5077 expression: &'tcx hir::Expr,
5083 self.suggest_missing_semicolon(err, expression, expected, cause_span);
5084 let mut pointing_at_return_type = false;
5085 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
5086 pointing_at_return_type = self.suggest_missing_return_type(
5087 err, &fn_decl, expected, found, can_suggest);
5089 self.suggest_ref_or_into(err, expression, expected, found);
5090 pointing_at_return_type
5093 pub fn suggest_ref_or_into(
5095 err: &mut DiagnosticBuilder<'tcx>,
5100 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
5101 err.span_suggestion(
5105 Applicability::MachineApplicable,
5107 } else if !self.check_for_cast(err, expr, found, expected) {
5108 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
5112 let methods = self.get_conversion_methods(expr.span, expected, found);
5113 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
5114 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
5115 .filter_map(|(receiver, method)| {
5116 let method_call = format!(".{}()", method.ident);
5117 if receiver.ends_with(&method_call) {
5118 None // do not suggest code that is already there (#53348)
5120 let method_call_list = [".to_vec()", ".to_string()"];
5121 let sugg = if receiver.ends_with(".clone()")
5122 && method_call_list.contains(&method_call.as_str()) {
5123 let max_len = receiver.rfind(".").unwrap();
5124 format!("{}{}", &receiver[..max_len], method_call)
5126 format!("{}{}", receiver, method_call)
5128 Some(if is_struct_pat_shorthand_field {
5129 format!("{}: {}", receiver, sugg)
5135 if suggestions.peek().is_some() {
5136 err.span_suggestions(
5138 "try using a conversion method",
5140 Applicability::MaybeIncorrect,
5147 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
5151 /// bar_that_returns_u32()
5155 /// This routine checks if the return expression in a block would make sense on its own as a
5156 /// statement and the return type has been left as default or has been specified as `()`. If so,
5157 /// it suggests adding a semicolon.
5158 fn suggest_missing_semicolon(&self,
5159 err: &mut DiagnosticBuilder<'tcx>,
5160 expression: &'tcx hir::Expr,
5163 if expected.is_unit() {
5164 // `BlockTailExpression` only relevant if the tail expr would be
5165 // useful on its own.
5166 match expression.node {
5167 ExprKind::Call(..) |
5168 ExprKind::MethodCall(..) |
5169 ExprKind::While(..) |
5170 ExprKind::Loop(..) |
5171 ExprKind::Match(..) |
5172 ExprKind::Block(..) => {
5173 let sp = self.tcx.sess.source_map().next_point(cause_span);
5174 err.span_suggestion(
5176 "try adding a semicolon",
5178 Applicability::MachineApplicable);
5185 /// A possible error is to forget to add a return type that is needed:
5189 /// bar_that_returns_u32()
5193 /// This routine checks if the return type is left as default, the method is not part of an
5194 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
5196 fn suggest_missing_return_type(
5198 err: &mut DiagnosticBuilder<'tcx>,
5199 fn_decl: &hir::FnDecl,
5204 // Only suggest changing the return type for methods that
5205 // haven't set a return type at all (and aren't `fn main()` or an impl).
5206 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
5207 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
5208 err.span_suggestion(
5210 "try adding a return type",
5211 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
5212 Applicability::MachineApplicable);
5215 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
5216 err.span_label(span, "possibly return type missing here?");
5219 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
5220 // `fn main()` must return `()`, do not suggest changing return type
5221 err.span_label(span, "expected `()` because of default return type");
5224 // expectation was caused by something else, not the default return
5225 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
5226 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
5227 // Only point to return type if the expected type is the return type, as if they
5228 // are not, the expectation must have been caused by something else.
5229 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.node);
5231 let ty = AstConv::ast_ty_to_ty(self, ty);
5232 debug!("suggest_missing_return_type: return type {:?}", ty);
5233 debug!("suggest_missing_return_type: expected type {:?}", ty);
5234 if ty.sty == expected.sty {
5235 err.span_label(sp, format!("expected `{}` because of return type",
5244 /// A common error is to add an extra semicolon:
5247 /// fn foo() -> usize {
5252 /// This routine checks if the final statement in a block is an
5253 /// expression with an explicit semicolon whose type is compatible
5254 /// with `expected_ty`. If so, it suggests removing the semicolon.
5255 fn consider_hint_about_removing_semicolon(
5257 blk: &'tcx hir::Block,
5258 expected_ty: Ty<'tcx>,
5259 err: &mut DiagnosticBuilder<'_>,
5261 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
5262 err.span_suggestion(
5264 "consider removing this semicolon",
5266 Applicability::MachineApplicable,
5271 fn could_remove_semicolon(
5273 blk: &'tcx hir::Block,
5274 expected_ty: Ty<'tcx>,
5276 // Be helpful when the user wrote `{... expr;}` and
5277 // taking the `;` off is enough to fix the error.
5278 let last_stmt = blk.stmts.last()?;
5279 let last_expr = match last_stmt.node {
5280 hir::StmtKind::Semi(ref e) => e,
5283 let last_expr_ty = self.node_ty(last_expr.hir_id);
5284 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
5287 let original_span = original_sp(last_stmt.span, blk.span);
5288 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
5291 // Rewrite `SelfCtor` to `Ctor`
5292 pub fn rewrite_self_ctor(
5296 ) -> Result<Res, ErrorReported> {
5298 if let Res::SelfCtor(impl_def_id) = res {
5299 let ty = self.impl_self_ty(span, impl_def_id).ty;
5300 let adt_def = ty.ty_adt_def();
5303 Some(adt_def) if adt_def.has_ctor() => {
5304 let variant = adt_def.non_enum_variant();
5305 let ctor_def_id = variant.ctor_def_id.unwrap();
5306 Ok(Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id))
5309 let mut err = tcx.sess.struct_span_err(span,
5310 "the `Self` constructor can only be used with tuple or unit structs");
5311 if let Some(adt_def) = adt_def {
5312 match adt_def.adt_kind() {
5314 err.help("did you mean to use one of the enum's variants?");
5318 err.span_suggestion(
5320 "use curly brackets",
5321 String::from("Self { /* fields */ }"),
5322 Applicability::HasPlaceholders,
5337 // Instantiates the given path, which must refer to an item with the given
5338 // number of type parameters and type.
5339 pub fn instantiate_value_path(&self,
5340 segments: &[hir::PathSegment],
5341 self_ty: Option<Ty<'tcx>>,
5345 -> (Ty<'tcx>, Res) {
5347 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
5356 let res = match self.rewrite_self_ctor(res, span) {
5358 Err(ErrorReported) => return (tcx.types.err, res),
5360 let path_segs = match res {
5361 Res::Local(_) => vec![],
5362 Res::Def(kind, def_id) =>
5363 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
5364 _ => bug!("instantiate_value_path on {:?}", res),
5367 let mut user_self_ty = None;
5368 let mut is_alias_variant_ctor = false;
5370 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
5371 if let Some(self_ty) = self_ty {
5372 let adt_def = self_ty.ty_adt_def().unwrap();
5373 user_self_ty = Some(UserSelfTy {
5374 impl_def_id: adt_def.did,
5377 is_alias_variant_ctor = true;
5380 Res::Def(DefKind::Method, def_id)
5381 | Res::Def(DefKind::AssocConst, def_id) => {
5382 let container = tcx.associated_item(def_id).container;
5383 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
5385 ty::TraitContainer(trait_did) => {
5386 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
5388 ty::ImplContainer(impl_def_id) => {
5389 if segments.len() == 1 {
5390 // `<T>::assoc` will end up here, and so
5391 // can `T::assoc`. It this came from an
5392 // inherent impl, we need to record the
5393 // `T` for posterity (see `UserSelfTy` for
5395 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
5396 user_self_ty = Some(UserSelfTy {
5407 // Now that we have categorized what space the parameters for each
5408 // segment belong to, let's sort out the parameters that the user
5409 // provided (if any) into their appropriate spaces. We'll also report
5410 // errors if type parameters are provided in an inappropriate place.
5412 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
5413 let generics_has_err = AstConv::prohibit_generics(
5414 self, segments.iter().enumerate().filter_map(|(index, seg)| {
5415 if !generic_segs.contains(&index) || is_alias_variant_ctor {
5422 if let Res::Local(hid) = res {
5423 let ty = self.local_ty(span, hid).decl_ty;
5424 let ty = self.normalize_associated_types_in(span, &ty);
5425 self.write_ty(hir_id, ty);
5429 if generics_has_err {
5430 // Don't try to infer type parameters when prohibited generic arguments were given.
5431 user_self_ty = None;
5434 // Now we have to compare the types that the user *actually*
5435 // provided against the types that were *expected*. If the user
5436 // did not provide any types, then we want to substitute inference
5437 // variables. If the user provided some types, we may still need
5438 // to add defaults. If the user provided *too many* types, that's
5441 let mut infer_args_for_err = FxHashSet::default();
5442 for &PathSeg(def_id, index) in &path_segs {
5443 let seg = &segments[index];
5444 let generics = tcx.generics_of(def_id);
5445 // Argument-position `impl Trait` is treated as a normal generic
5446 // parameter internally, but we don't allow users to specify the
5447 // parameter's value explicitly, so we have to do some error-
5449 let suppress_errors = AstConv::check_generic_arg_count_for_call(
5454 false, // `is_method_call`
5456 if suppress_errors {
5457 infer_args_for_err.insert(index);
5458 self.set_tainted_by_errors(); // See issue #53251.
5462 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
5463 tcx.generics_of(*def_id).has_self
5464 }).unwrap_or(false);
5466 let def_id = res.def_id();
5468 // The things we are substituting into the type should not contain
5469 // escaping late-bound regions, and nor should the base type scheme.
5470 let ty = tcx.type_of(def_id);
5472 let substs = AstConv::create_substs_for_generic_args(
5478 // Provide the generic args, and whether types should be inferred.
5480 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
5483 // If we've encountered an `impl Trait`-related error, we're just
5484 // going to infer the arguments for better error messages.
5485 if !infer_args_for_err.contains(&index) {
5486 // Check whether the user has provided generic arguments.
5487 if let Some(ref data) = segments[index].args {
5488 return (Some(data), segments[index].infer_args);
5491 return (None, segments[index].infer_args);
5496 // Provide substitutions for parameters for which (valid) arguments have been provided.
5498 match (¶m.kind, arg) {
5499 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
5500 AstConv::ast_region_to_region(self, lt, Some(param)).into()
5502 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
5503 self.to_ty(ty).into()
5505 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
5506 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
5508 _ => unreachable!(),
5511 // Provide substitutions for parameters for which arguments are inferred.
5512 |substs, param, infer_args| {
5514 GenericParamDefKind::Lifetime => {
5515 self.re_infer(Some(param), span).unwrap().into()
5517 GenericParamDefKind::Type { has_default, .. } => {
5518 if !infer_args && has_default {
5519 // If we have a default, then we it doesn't matter that we're not
5520 // inferring the type arguments: we provide the default where any
5522 let default = tcx.type_of(param.def_id);
5525 default.subst_spanned(tcx, substs.unwrap(), Some(span))
5528 // If no type arguments were provided, we have to infer them.
5529 // This case also occurs as a result of some malformed input, e.g.
5530 // a lifetime argument being given instead of a type parameter.
5531 // Using inference instead of `Error` gives better error messages.
5532 self.var_for_def(span, param)
5535 GenericParamDefKind::Const => {
5536 // FIXME(const_generics:defaults)
5537 // No const parameters were provided, we have to infer them.
5538 self.var_for_def(span, param)
5543 assert!(!substs.has_escaping_bound_vars());
5544 assert!(!ty.has_escaping_bound_vars());
5546 // First, store the "user substs" for later.
5547 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
5549 // Add all the obligations that are required, substituting and
5550 // normalized appropriately.
5551 let bounds = self.instantiate_bounds(span, def_id, &substs);
5552 self.add_obligations_for_parameters(
5553 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
5556 // Substitute the values for the type parameters into the type of
5557 // the referenced item.
5558 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
5560 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
5561 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
5562 // is inherent, there is no `Self` parameter; instead, the impl needs
5563 // type parameters, which we can infer by unifying the provided `Self`
5564 // with the substituted impl type.
5565 // This also occurs for an enum variant on a type alias.
5566 let ty = tcx.type_of(impl_def_id);
5568 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
5569 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
5570 Ok(ok) => self.register_infer_ok_obligations(ok),
5572 self.tcx.sess.delay_span_bug(span, &format!(
5573 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
5581 self.check_rustc_args_require_const(def_id, hir_id, span);
5583 debug!("instantiate_value_path: type of {:?} is {:?}",
5586 self.write_substs(hir_id, substs);
5588 (ty_substituted, res)
5591 fn check_rustc_args_require_const(&self,
5595 // We're only interested in functions tagged with
5596 // #[rustc_args_required_const], so ignore anything that's not.
5597 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5601 // If our calling expression is indeed the function itself, we're good!
5602 // If not, generate an error that this can only be called directly.
5603 if let Node::Expr(expr) = self.tcx.hir().get_by_hir_id(
5604 self.tcx.hir().get_parent_node_by_hir_id(hir_id))
5606 if let ExprKind::Call(ref callee, ..) = expr.node {
5607 if callee.hir_id == hir_id {
5613 self.tcx.sess.span_err(span, "this function can only be invoked \
5614 directly, not through a function pointer");
5617 // Resolves `typ` by a single level if `typ` is a type variable.
5618 // If no resolution is possible, then an error is reported.
5619 // Numeric inference variables may be left unresolved.
5620 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5621 let ty = self.resolve_type_vars_with_obligations(ty);
5622 if !ty.is_ty_var() {
5625 if !self.is_tainted_by_errors() {
5626 self.need_type_info_err((**self).body_id, sp, ty)
5627 .note("type must be known at this point")
5630 self.demand_suptype(sp, self.tcx.types.err, ty);
5635 fn with_breakable_ctxt<F: FnOnce() -> R, R>(&self, id: hir::HirId,
5636 ctxt: BreakableCtxt<'tcx>, f: F)
5637 -> (BreakableCtxt<'tcx>, R) {
5640 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5641 index = enclosing_breakables.stack.len();
5642 enclosing_breakables.by_id.insert(id, index);
5643 enclosing_breakables.stack.push(ctxt);
5647 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5648 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5649 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5650 enclosing_breakables.stack.pop().expect("missing breakable context")
5655 /// Instantiate a QueryResponse in a probe context, without a
5656 /// good ObligationCause.
5657 fn probe_instantiate_query_response(
5660 original_values: &OriginalQueryValues<'tcx>,
5661 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5662 ) -> InferResult<'tcx, Ty<'tcx>>
5664 self.instantiate_query_response_and_region_obligations(
5665 &traits::ObligationCause::misc(span, self.body_id),
5671 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5672 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5673 let mut contained_in_place = false;
5675 while let hir::Node::Expr(parent_expr) =
5676 self.tcx.hir().get_by_hir_id(self.tcx.hir().get_parent_node_by_hir_id(expr_id))
5678 match &parent_expr.node {
5679 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5680 if lhs.hir_id == expr_id {
5681 contained_in_place = true;
5687 expr_id = parent_expr.hir_id;
5694 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5695 let own_counts = generics.own_counts();
5697 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5703 if own_counts.types == 0 {
5707 // Make a vector of booleans initially false, set to true when used.
5708 let mut types_used = vec![false; own_counts.types];
5710 for leaf_ty in ty.walk() {
5711 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.sty {
5712 debug!("Found use of ty param num {}", index);
5713 types_used[index as usize - own_counts.lifetimes] = true;
5714 } else if let ty::Error = leaf_ty.sty {
5715 // If there is already another error, do not emit
5716 // an error for not using a type Parameter.
5717 assert!(tcx.sess.err_count() > 0);
5722 let types = generics.params.iter().filter(|param| match param.kind {
5723 ty::GenericParamDefKind::Type { .. } => true,
5726 for (&used, param) in types_used.iter().zip(types) {
5728 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5729 let span = tcx.hir().span_by_hir_id(id);
5730 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5731 .span_label(span, "unused type parameter")
5737 fn fatally_break_rust(sess: &Session) {
5738 let handler = sess.diagnostic();
5739 handler.span_bug_no_panic(
5741 "It looks like you're trying to break rust; would you like some ICE?",
5743 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5744 handler.note_without_error(
5745 "we would appreciate a joke overview: \
5746 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5748 handler.note_without_error(&format!("rustc {} running on {}",
5749 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5750 crate::session::config::host_triple(),
5754 fn potentially_plural_count(count: usize, word: &str) -> String {
5755 format!("{} {}{}", count, word, if count == 1 { "" } else { "s" })