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
86 mod generator_interior;
90 use crate::astconv::{AstConv, PathSeg};
91 use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
92 use rustc::hir::{self, ExprKind, GenericArg, ItemKind, Node, PatKind, QPath};
93 use rustc::hir::def::{CtorOf, Res, DefKind};
94 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
95 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
96 use rustc::hir::itemlikevisit::ItemLikeVisitor;
97 use rustc::hir::ptr::P;
98 use crate::middle::lang_items;
99 use crate::namespace::Namespace;
100 use rustc::infer::{self, InferCtxt, InferOk, InferResult};
101 use rustc::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
102 use rustc_data_structures::indexed_vec::Idx;
103 use rustc_target::spec::abi::Abi;
104 use rustc::infer::opaque_types::OpaqueTypeDecl;
105 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
106 use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
107 use rustc::middle::region;
108 use rustc::mir::interpret::{ConstValue, GlobalId};
109 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
111 self, AdtKind, CanonicalUserType, Ty, TyCtxt, Const, GenericParamDefKind,
112 ToPolyTraitRef, ToPredicate, RegionKind, UserType
114 use rustc::ty::adjustment::{
115 Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast
117 use rustc::ty::fold::TypeFoldable;
118 use rustc::ty::query::Providers;
119 use rustc::ty::subst::{UnpackedKind, Subst, InternalSubsts, SubstsRef, UserSelfTy, UserSubsts};
120 use rustc::ty::util::{Representability, IntTypeExt, Discr};
121 use rustc::ty::layout::VariantIdx;
122 use syntax_pos::{self, BytePos, Span, MultiSpan};
123 use syntax_pos::hygiene::DesugaringKind;
126 use syntax::feature_gate::{GateIssue, emit_feature_err};
127 use syntax::source_map::{DUMMY_SP, original_sp};
128 use syntax::symbol::{kw, sym};
130 use std::cell::{Cell, RefCell, Ref, RefMut};
131 use std::collections::hash_map::Entry;
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, 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> {
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> {
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>, hir::GeneratorKind)>>,
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/ui/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_without_normalization(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, 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.
454 /// The `Span` points to the expression
455 /// that caused us to diverge
456 /// (e.g. `return`, `break`, etc).
458 /// In some cases (e.g. a `match` expression
459 /// where all arms diverge), we may be
460 /// able to provide a more informative
461 /// message to the user.
462 /// If this is `None`, a default messsage
463 /// will be generated, which is suitable
465 custom_note: Option<&'static str>
468 /// Same as `Always` but with a reachability
469 /// warning already emitted.
473 // Convenience impls for combinig `Diverges`.
475 impl ops::BitAnd for Diverges {
477 fn bitand(self, other: Self) -> Self {
478 cmp::min(self, other)
482 impl ops::BitOr for Diverges {
484 fn bitor(self, other: Self) -> Self {
485 cmp::max(self, other)
489 impl ops::BitAndAssign for Diverges {
490 fn bitand_assign(&mut self, other: Self) {
491 *self = *self & other;
495 impl ops::BitOrAssign for Diverges {
496 fn bitor_assign(&mut self, other: Self) {
497 *self = *self | other;
502 /// Creates a `Diverges::Always` with the provided `span` and the default note message.
503 fn always(span: Span) -> Diverges {
510 fn is_always(self) -> bool {
511 // Enum comparison ignores the
512 // contents of fields, so we just
513 // fill them in with garbage here.
514 self >= Diverges::Always {
521 pub struct BreakableCtxt<'tcx> {
524 // this is `null` for loops where break with a value is illegal,
525 // such as `while`, `for`, and `while let`
526 coerce: Option<DynamicCoerceMany<'tcx>>,
529 pub struct EnclosingBreakables<'tcx> {
530 stack: Vec<BreakableCtxt<'tcx>>,
531 by_id: HirIdMap<usize>,
534 impl<'tcx> EnclosingBreakables<'tcx> {
535 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
536 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
537 bug!("could not find enclosing breakable with id {}", target_id);
543 pub struct FnCtxt<'a, 'tcx> {
546 /// The parameter environment used for proving trait obligations
547 /// in this function. This can change when we descend into
548 /// closures (as they bring new things into scope), hence it is
549 /// not part of `Inherited` (as of the time of this writing,
550 /// closures do not yet change the environment, but they will
552 param_env: ty::ParamEnv<'tcx>,
554 /// Number of errors that had been reported when we started
555 /// checking this function. On exit, if we find that *more* errors
556 /// have been reported, we will skip regionck and other work that
557 /// expects the types within the function to be consistent.
558 // FIXME(matthewjasper) This should not exist, and it's not correct
559 // if type checking is run in parallel.
560 err_count_on_creation: usize,
562 ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
563 ret_coercion_span: RefCell<Option<Span>>,
565 yield_ty: Option<Ty<'tcx>>,
567 ps: RefCell<UnsafetyState>,
569 /// Whether the last checked node generates a divergence (e.g.,
570 /// `return` will set this to `Always`). In general, when entering
571 /// an expression or other node in the tree, the initial value
572 /// indicates whether prior parts of the containing expression may
573 /// have diverged. It is then typically set to `Maybe` (and the
574 /// old value remembered) for processing the subparts of the
575 /// current expression. As each subpart is processed, they may set
576 /// the flag to `Always`, etc. Finally, at the end, we take the
577 /// result and "union" it with the original value, so that when we
578 /// return the flag indicates if any subpart of the parent
579 /// expression (up to and including this part) has diverged. So,
580 /// if you read it after evaluating a subexpression `X`, the value
581 /// you get indicates whether any subexpression that was
582 /// evaluating up to and including `X` diverged.
584 /// We currently use this flag only for diagnostic purposes:
586 /// - To warn about unreachable code: if, after processing a
587 /// sub-expression but before we have applied the effects of the
588 /// current node, we see that the flag is set to `Always`, we
589 /// can issue a warning. This corresponds to something like
590 /// `foo(return)`; we warn on the `foo()` expression. (We then
591 /// update the flag to `WarnedAlways` to suppress duplicate
592 /// reports.) Similarly, if we traverse to a fresh statement (or
593 /// tail expression) from a `Always` setting, we will issue a
594 /// warning. This corresponds to something like `{return;
595 /// foo();}` or `{return; 22}`, where we would warn on the
598 /// An expression represents dead code if, after checking it,
599 /// the diverges flag is set to something other than `Maybe`.
600 diverges: Cell<Diverges>,
602 /// Whether any child nodes have any type errors.
603 has_errors: Cell<bool>,
605 enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
607 inh: &'a Inherited<'a, 'tcx>,
610 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
611 type Target = Inherited<'a, 'tcx>;
612 fn deref(&self) -> &Self::Target {
617 /// Helper type of a temporary returned by `Inherited::build(...)`.
618 /// Necessary because we can't write the following bound:
619 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
620 pub struct InheritedBuilder<'tcx> {
621 infcx: infer::InferCtxtBuilder<'tcx>,
625 impl Inherited<'_, 'tcx> {
626 pub fn build(tcx: TyCtxt<'tcx>, def_id: DefId) -> InheritedBuilder<'tcx> {
627 let hir_id_root = if def_id.is_local() {
628 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
629 DefId::local(hir_id.owner)
635 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
641 impl<'tcx> InheritedBuilder<'tcx> {
642 fn enter<F, R>(&mut self, f: F) -> R
644 F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
646 let def_id = self.def_id;
647 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
651 impl Inherited<'a, 'tcx> {
652 fn new(infcx: InferCtxt<'a, 'tcx>, def_id: DefId) -> Self {
654 let item_id = tcx.hir().as_local_hir_id(def_id);
655 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by(id));
656 let implicit_region_bound = body_id.map(|body_id| {
657 let body = tcx.hir().body(body_id);
658 tcx.mk_region(ty::ReScope(region::Scope {
659 id: body.value.hir_id.local_id,
660 data: region::ScopeData::CallSite
665 tables: MaybeInProgressTables {
666 maybe_tables: infcx.in_progress_tables,
669 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
670 locals: RefCell::new(Default::default()),
671 deferred_sized_obligations: RefCell::new(Vec::new()),
672 deferred_call_resolutions: RefCell::new(Default::default()),
673 deferred_cast_checks: RefCell::new(Vec::new()),
674 deferred_generator_interiors: RefCell::new(Vec::new()),
675 opaque_types: RefCell::new(Default::default()),
676 implicit_region_bound,
681 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
682 debug!("register_predicate({:?})", obligation);
683 if obligation.has_escaping_bound_vars() {
684 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}",
689 .register_predicate_obligation(self, obligation);
692 fn register_predicates<I>(&self, obligations: I)
693 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>>
695 for obligation in obligations {
696 self.register_predicate(obligation);
700 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
701 self.register_predicates(infer_ok.obligations);
705 fn normalize_associated_types_in<T>(&self,
708 param_env: ty::ParamEnv<'tcx>,
710 where T : TypeFoldable<'tcx>
712 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
713 self.register_infer_ok_obligations(ok)
717 struct CheckItemTypesVisitor<'tcx> {
721 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
722 fn visit_item(&mut self, i: &'tcx hir::Item) {
723 check_item_type(self.tcx, i);
725 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
726 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
729 pub fn check_wf_new(tcx: TyCtxt<'_>) {
730 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
731 tcx.hir().krate().par_visit_all_item_likes(&mut visit);
734 fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
735 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
738 fn typeck_item_bodies(tcx: TyCtxt<'_>, crate_num: CrateNum) {
739 debug_assert!(crate_num == LOCAL_CRATE);
740 tcx.par_body_owners(|body_owner_def_id| {
741 tcx.ensure().typeck_tables_of(body_owner_def_id);
745 fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
746 wfcheck::check_item_well_formed(tcx, def_id);
749 fn check_trait_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
750 wfcheck::check_trait_item(tcx, def_id);
753 fn check_impl_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
754 wfcheck::check_impl_item(tcx, def_id);
757 pub fn provide(providers: &mut Providers<'_>) {
758 method::provide(providers);
759 *providers = Providers {
765 check_item_well_formed,
766 check_trait_item_well_formed,
767 check_impl_item_well_formed,
768 check_mod_item_types,
773 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
774 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
777 /// If this `DefId` is a "primary tables entry", returns
778 /// `Some((body_id, header, decl))` with information about
779 /// it's body-id, fn-header and fn-decl (if any). Otherwise,
782 /// If this function returns `Some`, then `typeck_tables(def_id)` will
783 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
784 /// may not succeed. In some cases where this function returns `None`
785 /// (notably closures), `typeck_tables(def_id)` would wind up
786 /// redirecting to the owning function.
790 ) -> Option<(hir::BodyId, Option<&hir::Ty>, Option<&hir::FnHeader>, Option<&hir::FnDecl>)> {
791 match tcx.hir().get(id) {
792 Node::Item(item) => {
794 hir::ItemKind::Const(ref ty, body) |
795 hir::ItemKind::Static(ref ty, _, body) =>
796 Some((body, Some(ty), None, None)),
797 hir::ItemKind::Fn(ref decl, ref header, .., body) =>
798 Some((body, None, Some(header), Some(decl))),
803 Node::TraitItem(item) => {
805 hir::TraitItemKind::Const(ref ty, Some(body)) =>
806 Some((body, Some(ty), None, None)),
807 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
808 Some((body, None, Some(&sig.header), Some(&sig.decl))),
813 Node::ImplItem(item) => {
815 hir::ImplItemKind::Const(ref ty, body) =>
816 Some((body, Some(ty), None, None)),
817 hir::ImplItemKind::Method(ref sig, body) =>
818 Some((body, None, Some(&sig.header), Some(&sig.decl))),
823 Node::AnonConst(constant) => Some((constant.body, None, None, None)),
828 fn has_typeck_tables(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
829 // Closures' tables come from their outermost function,
830 // as they are part of the same "inference environment".
831 let outer_def_id = tcx.closure_base_def_id(def_id);
832 if outer_def_id != def_id {
833 return tcx.has_typeck_tables(outer_def_id);
836 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
837 primary_body_of(tcx, id).is_some()
840 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: DefId) -> &DefIdSet {
841 &*tcx.typeck_tables_of(def_id).used_trait_imports
844 fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
845 // Closures' tables come from their outermost function,
846 // as they are part of the same "inference environment".
847 let outer_def_id = tcx.closure_base_def_id(def_id);
848 if outer_def_id != def_id {
849 return tcx.typeck_tables_of(outer_def_id);
852 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
853 let span = tcx.hir().span(id);
855 // Figure out what primary body this item has.
856 let (body_id, body_ty, fn_header, fn_decl) = primary_body_of(tcx, id)
858 span_bug!(span, "can't type-check body of {:?}", def_id);
860 let body = tcx.hir().body(body_id);
862 let tables = Inherited::build(tcx, def_id).enter(|inh| {
863 let param_env = tcx.param_env(def_id);
864 let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
865 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
866 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
867 AstConv::ty_of_fn(&fcx, header.unsafety, header.abi, decl)
872 check_abi(tcx, span, fn_sig.abi());
874 // Compute the fty from point of view of inside the fn.
876 tcx.liberate_late_bound_regions(def_id, &fn_sig);
878 inh.normalize_associated_types_in(body.value.span,
883 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
886 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
887 let expected_type = body_ty.and_then(|ty| match ty.node {
888 hir::TyKind::Infer => Some(AstConv::ast_ty_to_ty(&fcx, ty)),
890 }).unwrap_or_else(|| tcx.type_of(def_id));
891 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
892 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
894 let revealed_ty = if tcx.features().impl_trait_in_bindings {
895 fcx.instantiate_opaque_types_from_value(
904 // Gather locals in statics (because of block expressions).
905 GatherLocalsVisitor { fcx: &fcx, parent_id: id, }.visit_body(body);
907 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
909 fcx.write_ty(id, revealed_ty);
914 // All type checking constraints were added, try to fallback unsolved variables.
915 fcx.select_obligations_where_possible(false);
916 let mut fallback_has_occurred = false;
917 for ty in &fcx.unsolved_variables() {
918 fallback_has_occurred |= fcx.fallback_if_possible(ty);
920 fcx.select_obligations_where_possible(fallback_has_occurred);
922 // Even though coercion casts provide type hints, we check casts after fallback for
923 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
926 // Closure and generator analysis may run after fallback
927 // because they don't constrain other type variables.
928 fcx.closure_analyze(body);
929 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
930 fcx.resolve_generator_interiors(def_id);
932 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
933 let ty = fcx.normalize_ty(span, ty);
934 fcx.require_type_is_sized(ty, span, code);
936 fcx.select_all_obligations_or_error();
938 if fn_decl.is_some() {
939 fcx.regionck_fn(id, body);
941 fcx.regionck_expr(body);
944 fcx.resolve_type_vars_in_body(body)
947 // Consistency check our TypeckTables instance can hold all ItemLocalIds
948 // it will need to hold.
949 assert_eq!(tables.local_id_root, Some(DefId::local(id.owner)));
954 fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
955 if !tcx.sess.target.target.is_abi_supported(abi) {
956 struct_span_err!(tcx.sess, span, E0570,
957 "The ABI `{}` is not supported for the current target", abi).emit()
961 struct GatherLocalsVisitor<'a, 'tcx> {
962 fcx: &'a FnCtxt<'a, 'tcx>,
963 parent_id: hir::HirId,
966 impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
967 fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
970 // infer the variable's type
971 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
972 kind: TypeVariableOriginKind::TypeInference,
975 self.fcx.locals.borrow_mut().insert(nid, LocalTy {
982 // take type that the user specified
983 self.fcx.locals.borrow_mut().insert(nid, typ);
990 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
991 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
992 NestedVisitorMap::None
995 // Add explicitly-declared locals.
996 fn visit_local(&mut self, local: &'tcx hir::Local) {
997 let local_ty = match local.ty {
999 let o_ty = self.fcx.to_ty(&ty);
1001 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
1002 self.fcx.instantiate_opaque_types_from_value(
1011 let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(
1012 &UserType::Ty(revealed_ty)
1014 debug!("visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
1015 ty.hir_id, o_ty, revealed_ty, c_ty);
1016 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
1018 Some(LocalTy { decl_ty: o_ty, revealed_ty })
1022 self.assign(local.span, local.hir_id, local_ty);
1024 debug!("local variable {:?} is assigned type {}",
1026 self.fcx.ty_to_string(
1027 self.fcx.locals.borrow().get(&local.hir_id).unwrap().clone().decl_ty));
1028 intravisit::walk_local(self, local);
1031 // Add pattern bindings.
1032 fn visit_pat(&mut self, p: &'tcx hir::Pat) {
1033 if let PatKind::Binding(_, _, ident, _) = p.node {
1034 let var_ty = self.assign(p.span, p.hir_id, None);
1036 if !self.fcx.tcx.features().unsized_locals {
1037 self.fcx.require_type_is_sized(var_ty, p.span,
1038 traits::VariableType(p.hir_id));
1041 debug!("pattern binding {} is assigned to {} with type {:?}",
1043 self.fcx.ty_to_string(
1044 self.fcx.locals.borrow().get(&p.hir_id).unwrap().clone().decl_ty),
1047 intravisit::walk_pat(self, p);
1050 // Don't descend into the bodies of nested closures
1053 _: intravisit::FnKind<'tcx>,
1054 _: &'tcx hir::FnDecl,
1061 /// When `check_fn` is invoked on a generator (i.e., a body that
1062 /// includes yield), it returns back some information about the yield
1064 struct GeneratorTypes<'tcx> {
1065 /// Type of value that is yielded.
1068 /// Types that are captured (see `GeneratorInterior` for more).
1071 /// Indicates if the generator is movable or static (immovable).
1072 movability: hir::GeneratorMovability,
1075 /// Helper used for fns and closures. Does the grungy work of checking a function
1076 /// body and returns the function context used for that purpose, since in the case of a fn item
1077 /// there is still a bit more to do.
1080 /// * inherited: other fields inherited from the enclosing fn (if any)
1081 fn check_fn<'a, 'tcx>(
1082 inherited: &'a Inherited<'a, 'tcx>,
1083 param_env: ty::ParamEnv<'tcx>,
1084 fn_sig: ty::FnSig<'tcx>,
1085 decl: &'tcx hir::FnDecl,
1087 body: &'tcx hir::Body,
1088 can_be_generator: Option<hir::GeneratorMovability>,
1089 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
1090 let mut fn_sig = fn_sig.clone();
1092 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1094 // Create the function context. This is either derived from scratch or,
1095 // in the case of closures, based on the outer context.
1096 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1097 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1099 let declared_ret_ty = fn_sig.output();
1100 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1101 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(
1106 debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
1107 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1108 fn_sig = fcx.tcx.mk_fn_sig(
1109 fn_sig.inputs().iter().cloned(),
1116 let span = body.value.span;
1118 fn_maybe_err(fcx.tcx, span, fn_sig.abi);
1120 if body.generator_kind.is_some() && can_be_generator.is_some() {
1121 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
1122 kind: TypeVariableOriginKind::TypeInference,
1125 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1126 fcx.yield_ty = Some(yield_ty);
1129 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id(fn_id));
1130 let outer_hir_id = fcx.tcx.hir().as_local_hir_id(outer_def_id).unwrap();
1131 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id, }.visit_body(body);
1133 // Add formal parameters.
1134 for (param_ty, param) in fn_sig.inputs().iter().zip(&body.params) {
1135 // Check the pattern.
1136 fcx.check_pat_top(¶m.pat, param_ty, None);
1138 // Check that argument is Sized.
1139 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1140 // for simple cases like `fn foo(x: Trait)`,
1141 // where we would error once on the parameter as a whole, and once on the binding `x`.
1142 if param.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1143 fcx.require_type_is_sized(param_ty, decl.output.span(), traits::SizedArgumentType);
1146 fcx.write_ty(param.hir_id, param_ty);
1149 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1151 fcx.check_return_expr(&body.value);
1153 // We insert the deferred_generator_interiors entry after visiting the body.
1154 // This ensures that all nested generators appear before the entry of this generator.
1155 // resolve_generator_interiors relies on this property.
1156 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
1157 let interior = fcx.next_ty_var(TypeVariableOrigin {
1158 kind: TypeVariableOriginKind::MiscVariable,
1161 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
1162 Some(GeneratorTypes {
1163 yield_ty: fcx.yield_ty.unwrap(),
1165 movability: can_be_generator.unwrap(),
1171 // Finalize the return check by taking the LUB of the return types
1172 // we saw and assigning it to the expected return type. This isn't
1173 // really expected to fail, since the coercions would have failed
1174 // earlier when trying to find a LUB.
1176 // However, the behavior around `!` is sort of complex. In the
1177 // event that the `actual_return_ty` comes back as `!`, that
1178 // indicates that the fn either does not return or "returns" only
1179 // values of type `!`. In this case, if there is an expected
1180 // return type that is *not* `!`, that should be ok. But if the
1181 // return type is being inferred, we want to "fallback" to `!`:
1183 // let x = move || panic!();
1185 // To allow for that, I am creating a type variable with diverging
1186 // fallback. This was deemed ever so slightly better than unifying
1187 // the return value with `!` because it allows for the caller to
1188 // make more assumptions about the return type (e.g., they could do
1190 // let y: Option<u32> = Some(x());
1192 // which would then cause this return type to become `u32`, not
1194 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1195 let mut actual_return_ty = coercion.complete(&fcx);
1196 if actual_return_ty.is_never() {
1197 actual_return_ty = fcx.next_diverging_ty_var(
1198 TypeVariableOrigin {
1199 kind: TypeVariableOriginKind::DivergingFn,
1204 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1206 // Check that the main return type implements the termination trait.
1207 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1208 if let Some((def_id, EntryFnType::Main)) = fcx.tcx.entry_fn(LOCAL_CRATE) {
1209 let main_id = fcx.tcx.hir().as_local_hir_id(def_id).unwrap();
1210 if main_id == fn_id {
1211 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1212 let trait_ref = ty::TraitRef::new(term_id, substs);
1213 let return_ty_span = decl.output.span();
1214 let cause = traits::ObligationCause::new(
1215 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1217 inherited.register_predicate(
1218 traits::Obligation::new(
1219 cause, param_env, trait_ref.to_predicate()));
1224 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1225 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1226 if panic_impl_did == fcx.tcx.hir().local_def_id(fn_id) {
1227 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1228 // at this point we don't care if there are duplicate handlers or if the handler has
1229 // the wrong signature as this value we'll be used when writing metadata and that
1230 // only happens if compilation succeeded
1231 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1233 if declared_ret_ty.sty != ty::Never {
1234 fcx.tcx.sess.span_err(
1236 "return type should be `!`",
1240 let inputs = fn_sig.inputs();
1241 let span = fcx.tcx.hir().span(fn_id);
1242 if inputs.len() == 1 {
1243 let arg_is_panic_info = match inputs[0].sty {
1244 ty::Ref(region, ty, mutbl) => match ty.sty {
1245 ty::Adt(ref adt, _) => {
1246 adt.did == panic_info_did &&
1247 mutbl == hir::Mutability::MutImmutable &&
1248 *region != RegionKind::ReStatic
1255 if !arg_is_panic_info {
1256 fcx.tcx.sess.span_err(
1257 decl.inputs[0].span,
1258 "argument should be `&PanicInfo`",
1262 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1263 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1264 if !generics.params.is_empty() {
1265 fcx.tcx.sess.span_err(
1267 "should have no type parameters",
1273 let span = fcx.tcx.sess.source_map().def_span(span);
1274 fcx.tcx.sess.span_err(span, "function should have one argument");
1277 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1282 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1283 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1284 if alloc_error_handler_did == fcx.tcx.hir().local_def_id(fn_id) {
1285 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1286 if declared_ret_ty.sty != ty::Never {
1287 fcx.tcx.sess.span_err(
1289 "return type should be `!`",
1293 let inputs = fn_sig.inputs();
1294 let span = fcx.tcx.hir().span(fn_id);
1295 if inputs.len() == 1 {
1296 let arg_is_alloc_layout = match inputs[0].sty {
1297 ty::Adt(ref adt, _) => {
1298 adt.did == alloc_layout_did
1303 if !arg_is_alloc_layout {
1304 fcx.tcx.sess.span_err(
1305 decl.inputs[0].span,
1306 "argument should be `Layout`",
1310 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1311 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1312 if !generics.params.is_empty() {
1313 fcx.tcx.sess.span_err(
1315 "`#[alloc_error_handler]` function should have no type \
1322 let span = fcx.tcx.sess.source_map().def_span(span);
1323 fcx.tcx.sess.span_err(span, "function should have one argument");
1326 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1334 fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1335 let def_id = tcx.hir().local_def_id(id);
1336 let def = tcx.adt_def(def_id);
1337 def.destructor(tcx); // force the destructor to be evaluated
1338 check_representable(tcx, span, def_id);
1340 if def.repr.simd() {
1341 check_simd(tcx, span, def_id);
1344 check_transparent(tcx, span, def_id);
1345 check_packed(tcx, span, def_id);
1348 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1349 let def_id = tcx.hir().local_def_id(id);
1350 let def = tcx.adt_def(def_id);
1351 def.destructor(tcx); // force the destructor to be evaluated
1352 check_representable(tcx, span, def_id);
1353 check_transparent(tcx, span, def_id);
1354 check_packed(tcx, span, def_id);
1357 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
1358 /// projections that would result in "inheriting lifetimes".
1359 fn check_opaque<'tcx>(
1362 substs: SubstsRef<'tcx>,
1364 origin: &hir::OpaqueTyOrigin,
1366 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
1367 check_opaque_for_cycles(tcx, def_id, substs, span, origin);
1370 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
1371 /// in "inheriting lifetimes".
1372 fn check_opaque_for_inheriting_lifetimes(
1377 let item = tcx.hir().expect_item(
1378 tcx.hir().as_local_hir_id(def_id).expect("opaque type is not local"));
1379 debug!("check_opaque_for_inheriting_lifetimes: def_id={:?} span={:?} item={:?}",
1380 def_id, span, item);
1383 struct ProhibitOpaqueVisitor<'tcx> {
1384 opaque_identity_ty: Ty<'tcx>,
1385 generics: &'tcx ty::Generics,
1388 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
1389 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
1390 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
1391 if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) }
1394 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1395 debug!("check_opaque_for_inheriting_lifetimes: (visit_region) r={:?}", r);
1396 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
1397 return *index < self.generics.parent_count as u32;
1400 r.super_visit_with(self)
1404 let prohibit_opaque = match item.node {
1405 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn, .. }) |
1406 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn, .. }) => {
1407 let mut visitor = ProhibitOpaqueVisitor {
1408 opaque_identity_ty: tcx.mk_opaque(
1409 def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1410 generics: tcx.generics_of(def_id),
1412 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1414 tcx.predicates_of(def_id).predicates.iter().any(
1415 |(predicate, _)| predicate.visit_with(&mut visitor))
1420 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1421 if prohibit_opaque {
1422 let is_async = match item.node {
1423 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1424 hir::OpaqueTyOrigin::AsyncFn => true,
1427 _ => unreachable!(),
1430 tcx.sess.span_err(span, &format!(
1431 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1433 if is_async { "async fn" } else { "impl Trait" },
1438 /// Checks that an opaque type does not contain cycles.
1439 fn check_opaque_for_cycles<'tcx>(
1442 substs: SubstsRef<'tcx>,
1444 origin: &hir::OpaqueTyOrigin,
1446 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1447 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1449 tcx.sess, span, E0733,
1450 "recursion in an `async fn` requires boxing",
1452 .span_label(span, "recursive `async fn`")
1453 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`.")
1456 let mut err = struct_span_err!(
1457 tcx.sess, span, E0720,
1458 "opaque type expands to a recursive type",
1460 err.span_label(span, "expands to a recursive type");
1461 if let ty::Opaque(..) = partially_expanded_type.sty {
1462 err.note("type resolves to itself");
1464 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1471 // Forbid defining intrinsics in Rust code,
1472 // as they must always be defined by the compiler.
1473 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1474 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1475 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1479 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
1481 "check_item_type(it.hir_id={}, it.name={})",
1483 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1485 let _indenter = indenter();
1487 // Consts can play a role in type-checking, so they are included here.
1488 hir::ItemKind::Static(..) => {
1489 let def_id = tcx.hir().local_def_id(it.hir_id);
1490 tcx.typeck_tables_of(def_id);
1491 maybe_check_static_with_link_section(tcx, def_id, it.span);
1493 hir::ItemKind::Const(..) => {
1494 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1496 hir::ItemKind::Enum(ref enum_definition, _) => {
1497 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1499 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1500 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1501 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1502 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1503 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1504 check_impl_items_against_trait(
1511 let trait_def_id = impl_trait_ref.def_id;
1512 check_on_unimplemented(tcx, trait_def_id, it);
1515 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1516 let def_id = tcx.hir().local_def_id(it.hir_id);
1517 check_on_unimplemented(tcx, def_id, it);
1519 for item in items.iter() {
1520 let item = tcx.hir().trait_item(item.id);
1521 if let hir::TraitItemKind::Method(sig, _) = &item.node {
1522 let abi = sig.header.abi;
1523 fn_maybe_err(tcx, item.ident.span, abi);
1527 hir::ItemKind::Struct(..) => {
1528 check_struct(tcx, it.hir_id, it.span);
1530 hir::ItemKind::Union(..) => {
1531 check_union(tcx, it.hir_id, it.span);
1533 hir::ItemKind::OpaqueTy(hir::OpaqueTy{origin, ..}) => {
1534 let def_id = tcx.hir().local_def_id(it.hir_id);
1536 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1537 check_opaque(tcx, def_id, substs, it.span, &origin);
1539 hir::ItemKind::TyAlias(..) => {
1540 let def_id = tcx.hir().local_def_id(it.hir_id);
1541 let pty_ty = tcx.type_of(def_id);
1542 let generics = tcx.generics_of(def_id);
1543 check_bounds_are_used(tcx, &generics, pty_ty);
1545 hir::ItemKind::ForeignMod(ref m) => {
1546 check_abi(tcx, it.span, m.abi);
1548 if m.abi == Abi::RustIntrinsic {
1549 for item in &m.items {
1550 intrinsic::check_intrinsic_type(tcx, item);
1552 } else if m.abi == Abi::PlatformIntrinsic {
1553 for item in &m.items {
1554 intrinsic::check_platform_intrinsic_type(tcx, item);
1557 for item in &m.items {
1558 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1559 let own_counts = generics.own_counts();
1560 if generics.params.len() - own_counts.lifetimes != 0 {
1561 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1562 (_, 0) => ("type", "types", Some("u32")),
1563 // We don't specify an example value, because we can't generate
1564 // a valid value for any type.
1565 (0, _) => ("const", "consts", None),
1566 _ => ("type or const", "types or consts", None),
1572 "foreign items may not have {} parameters",
1576 &format!("can't have {} parameters", kinds),
1578 // FIXME: once we start storing spans for type arguments, turn this
1579 // into a suggestion.
1581 "replace the {} parameters with concrete {}{}",
1584 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1589 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.node {
1590 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1595 _ => { /* nothing to do */ }
1599 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1600 // Only restricted on wasm32 target for now
1601 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1605 // If `#[link_section]` is missing, then nothing to verify
1606 let attrs = tcx.codegen_fn_attrs(id);
1607 if attrs.link_section.is_none() {
1611 // For the wasm32 target statics with `#[link_section]` are placed into custom
1612 // sections of the final output file, but this isn't link custom sections of
1613 // other executable formats. Namely we can only embed a list of bytes,
1614 // nothing with pointers to anything else or relocations. If any relocation
1615 // show up, reject them here.
1616 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1617 // the consumer's responsibility to ensure all bytes that have been read
1618 // have defined values.
1619 let instance = ty::Instance::mono(tcx, id);
1620 let cid = GlobalId {
1624 let param_env = ty::ParamEnv::reveal_all();
1625 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1626 let alloc = if let ConstValue::ByRef { alloc, .. } = static_.val {
1629 bug!("Matching on non-ByRef static")
1631 if alloc.relocations().len() != 0 {
1632 let msg = "statics with a custom `#[link_section]` must be a \
1633 simple list of bytes on the wasm target with no \
1634 extra levels of indirection such as references";
1635 tcx.sess.span_err(span, msg);
1640 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item) {
1641 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1642 // an error would be reported if this fails.
1643 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1646 fn report_forbidden_specialization(
1648 impl_item: &hir::ImplItem,
1651 let mut err = struct_span_err!(
1652 tcx.sess, impl_item.span, E0520,
1653 "`{}` specializes an item from a parent `impl`, but \
1654 that item is not marked `default`",
1656 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1659 match tcx.span_of_impl(parent_impl) {
1661 err.span_label(span, "parent `impl` is here");
1662 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1666 err.note(&format!("parent implementation is in crate `{}`", cname));
1673 fn check_specialization_validity<'tcx>(
1675 trait_def: &ty::TraitDef,
1676 trait_item: &ty::AssocItem,
1678 impl_item: &hir::ImplItem,
1680 let ancestors = trait_def.ancestors(tcx, impl_id);
1682 let kind = match impl_item.node {
1683 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1684 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1685 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1686 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1689 let parent = ancestors.defs(tcx, trait_item.ident, kind, trait_def.def_id).nth(1)
1690 .map(|node_item| node_item.map(|parent| parent.defaultness));
1692 if let Some(parent) = parent {
1693 if tcx.impl_item_is_final(&parent) {
1694 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1700 fn check_impl_items_against_trait<'tcx>(
1704 impl_trait_ref: ty::TraitRef<'tcx>,
1705 impl_item_refs: &[hir::ImplItemRef],
1707 let impl_span = tcx.sess.source_map().def_span(impl_span);
1709 // If the trait reference itself is erroneous (so the compilation is going
1710 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1711 // isn't populated for such impls.
1712 if impl_trait_ref.references_error() { return; }
1714 // Locate trait definition and items
1715 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1716 let mut overridden_associated_type = None;
1718 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1720 // Check existing impl methods to see if they are both present in trait
1721 // and compatible with trait signature
1722 for impl_item in impl_items() {
1723 let ty_impl_item = tcx.associated_item(
1724 tcx.hir().local_def_id(impl_item.hir_id));
1725 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1726 .find(|ac| Namespace::from(&impl_item.node) == Namespace::from(ac.kind) &&
1727 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1729 // Not compatible, but needed for the error message
1730 tcx.associated_items(impl_trait_ref.def_id)
1731 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1734 // Check that impl definition matches trait definition
1735 if let Some(ty_trait_item) = ty_trait_item {
1736 match impl_item.node {
1737 hir::ImplItemKind::Const(..) => {
1738 // Find associated const definition.
1739 if ty_trait_item.kind == ty::AssocKind::Const {
1740 compare_const_impl(tcx,
1746 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1747 "item `{}` is an associated const, \
1748 which doesn't match its trait `{}`",
1751 err.span_label(impl_item.span, "does not match trait");
1752 // We can only get the spans from local trait definition
1753 // Same for E0324 and E0325
1754 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1755 err.span_label(trait_span, "item in trait");
1760 hir::ImplItemKind::Method(..) => {
1761 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1762 if ty_trait_item.kind == ty::AssocKind::Method {
1763 compare_impl_method(tcx,
1770 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1771 "item `{}` is an associated method, \
1772 which doesn't match its trait `{}`",
1775 err.span_label(impl_item.span, "does not match trait");
1776 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1777 err.span_label(trait_span, "item in trait");
1782 hir::ImplItemKind::OpaqueTy(..) |
1783 hir::ImplItemKind::TyAlias(_) => {
1784 if ty_trait_item.kind == ty::AssocKind::Type {
1785 if ty_trait_item.defaultness.has_value() {
1786 overridden_associated_type = Some(impl_item);
1789 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1790 "item `{}` is an associated type, \
1791 which doesn't match its trait `{}`",
1794 err.span_label(impl_item.span, "does not match trait");
1795 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1796 err.span_label(trait_span, "item in trait");
1803 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1807 // Check for missing items from trait
1808 let mut missing_items = Vec::new();
1809 let mut invalidated_items = Vec::new();
1810 let associated_type_overridden = overridden_associated_type.is_some();
1811 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1812 let is_implemented = trait_def.ancestors(tcx, impl_id)
1813 .defs(tcx, trait_item.ident, trait_item.kind, impl_trait_ref.def_id)
1815 .map(|node_item| !node_item.node.is_from_trait())
1818 if !is_implemented && !tcx.impl_is_default(impl_id) {
1819 if !trait_item.defaultness.has_value() {
1820 missing_items.push(trait_item);
1821 } else if associated_type_overridden {
1822 invalidated_items.push(trait_item.ident);
1827 if !missing_items.is_empty() {
1828 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1829 "not all trait items implemented, missing: `{}`",
1830 missing_items.iter()
1831 .map(|trait_item| trait_item.ident.to_string())
1832 .collect::<Vec<_>>().join("`, `"));
1833 err.span_label(impl_span, format!("missing `{}` in implementation",
1834 missing_items.iter()
1835 .map(|trait_item| trait_item.ident.to_string())
1836 .collect::<Vec<_>>().join("`, `")));
1837 for trait_item in missing_items {
1838 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1839 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1841 err.note_trait_signature(trait_item.ident.to_string(),
1842 trait_item.signature(tcx));
1848 if !invalidated_items.is_empty() {
1849 let invalidator = overridden_associated_type.unwrap();
1850 span_err!(tcx.sess, invalidator.span, E0399,
1851 "the following trait items need to be reimplemented \
1852 as `{}` was overridden: `{}`",
1854 invalidated_items.iter()
1855 .map(|name| name.to_string())
1856 .collect::<Vec<_>>().join("`, `"))
1860 /// Checks whether a type can be represented in memory. In particular, it
1861 /// identifies types that contain themselves without indirection through a
1862 /// pointer, which would mean their size is unbounded.
1863 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
1864 let rty = tcx.type_of(item_def_id);
1866 // Check that it is possible to represent this type. This call identifies
1867 // (1) types that contain themselves and (2) types that contain a different
1868 // recursive type. It is only necessary to throw an error on those that
1869 // contain themselves. For case 2, there must be an inner type that will be
1870 // caught by case 1.
1871 match rty.is_representable(tcx, sp) {
1872 Representability::SelfRecursive(spans) => {
1873 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1875 err.span_label(span, "recursive without indirection");
1880 Representability::Representable | Representability::ContainsRecursive => (),
1885 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1886 let t = tcx.type_of(def_id);
1887 if let ty::Adt(def, substs) = t.sty {
1888 if def.is_struct() {
1889 let fields = &def.non_enum_variant().fields;
1890 if fields.is_empty() {
1891 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1894 let e = fields[0].ty(tcx, substs);
1895 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1896 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1897 .span_label(sp, "SIMD elements must have the same type")
1902 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1903 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1905 span_err!(tcx.sess, sp, E0077,
1906 "SIMD vector element type should be machine type");
1914 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1915 let repr = tcx.adt_def(def_id).repr;
1917 for attr in tcx.get_attrs(def_id).iter() {
1918 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
1919 if let attr::ReprPacked(pack) = r {
1920 if let Some(repr_pack) = repr.pack {
1921 if pack as u64 != repr_pack.bytes() {
1923 tcx.sess, sp, E0634,
1924 "type has conflicting packed representation hints"
1931 if repr.align.is_some() {
1932 struct_span_err!(tcx.sess, sp, E0587,
1933 "type has conflicting packed and align representation hints").emit();
1935 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1936 struct_span_err!(tcx.sess, sp, E0588,
1937 "packed type cannot transitively contain a `[repr(align)]` type").emit();
1942 fn check_packed_inner(tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec<DefId>) -> bool {
1943 let t = tcx.type_of(def_id);
1944 if stack.contains(&def_id) {
1945 debug!("check_packed_inner: {:?} is recursive", t);
1948 if let ty::Adt(def, substs) = t.sty {
1949 if def.is_struct() || def.is_union() {
1950 if tcx.adt_def(def.did).repr.align.is_some() {
1953 // push struct def_id before checking fields
1955 for field in &def.non_enum_variant().fields {
1956 let f = field.ty(tcx, substs);
1957 if let ty::Adt(def, _) = f.sty {
1958 if check_packed_inner(tcx, def.did, stack) {
1963 // only need to pop if not early out
1970 /// Emit an error when encountering more or less than one variant in a transparent enum.
1971 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
1972 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
1973 tcx.hir().span_if_local(variant.def_id).unwrap()
1976 "needs exactly one variant, but has {}",
1979 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
1980 err.span_label(sp, &msg);
1981 if let &[ref start @ .., ref end] = &variant_spans[..] {
1982 for variant_span in start {
1983 err.span_label(*variant_span, "");
1985 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
1990 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
1992 fn bad_non_zero_sized_fields<'tcx>(
1994 adt: &'tcx ty::AdtDef,
1996 field_spans: impl Iterator<Item = Span>,
1999 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2000 let mut err = struct_span_err!(
2004 "{}transparent {} {}",
2005 if adt.is_enum() { "the variant of a " } else { "" },
2009 err.span_label(sp, &msg);
2010 for sp in field_spans {
2011 err.span_label(sp, "this field is non-zero-sized");
2016 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2017 let adt = tcx.adt_def(def_id);
2018 if !adt.repr.transparent() {
2021 let sp = tcx.sess.source_map().def_span(sp);
2024 if !tcx.features().transparent_enums {
2026 &tcx.sess.parse_sess,
2027 sym::transparent_enums,
2029 GateIssue::Language,
2030 "transparent enums are unstable",
2033 if adt.variants.len() != 1 {
2034 bad_variant_count(tcx, adt, sp, def_id);
2035 if adt.variants.is_empty() {
2036 // Don't bother checking the fields. No variants (and thus no fields) exist.
2042 if adt.is_union() && !tcx.features().transparent_unions {
2043 emit_feature_err(&tcx.sess.parse_sess,
2044 sym::transparent_unions,
2046 GateIssue::Language,
2047 "transparent unions are unstable");
2050 // For each field, figure out if it's known to be a ZST and align(1)
2051 let field_infos = adt.all_fields().map(|field| {
2052 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2053 let param_env = tcx.param_env(field.did);
2054 let layout = tcx.layout_of(param_env.and(ty));
2055 // We are currently checking the type this field came from, so it must be local
2056 let span = tcx.hir().span_if_local(field.did).unwrap();
2057 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2058 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2062 let non_zst_fields = field_infos.clone().filter_map(|(span, zst, _align1)| if !zst {
2067 let non_zst_count = non_zst_fields.clone().count();
2068 if non_zst_count != 1 {
2069 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2071 for (span, zst, align1) in field_infos {
2077 "zero-sized field in transparent {} has alignment larger than 1",
2079 ).span_label(span, "has alignment larger than 1").emit();
2084 #[allow(trivial_numeric_casts)]
2085 pub fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, vs: &'tcx [hir::Variant], id: hir::HirId) {
2086 let def_id = tcx.hir().local_def_id(id);
2087 let def = tcx.adt_def(def_id);
2088 def.destructor(tcx); // force the destructor to be evaluated
2091 let attributes = tcx.get_attrs(def_id);
2092 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2094 tcx.sess, attr.span, E0084,
2095 "unsupported representation for zero-variant enum")
2096 .span_label(sp, "zero-variant enum")
2101 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2102 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2103 if !tcx.features().repr128 {
2104 emit_feature_err(&tcx.sess.parse_sess,
2107 GateIssue::Language,
2108 "repr with 128-bit type is unstable");
2113 if let Some(ref e) = v.disr_expr {
2114 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2118 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2120 |var: &hir::Variant| match var.data {
2121 hir::VariantData::Unit(..) => true,
2125 let has_disr = |var: &hir::Variant| var.disr_expr.is_some();
2126 let has_non_units = vs.iter().any(|var| !is_unit(var));
2127 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2128 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2130 if disr_non_unit || (disr_units && has_non_units) {
2131 let mut err = struct_span_err!(tcx.sess, sp, E0732,
2132 "`#[repr(inttype)]` must be specified");
2137 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2138 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2139 // Check for duplicate discriminant values
2140 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2141 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2142 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2143 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2144 let i_span = match variant_i.disr_expr {
2145 Some(ref expr) => tcx.hir().span(expr.hir_id),
2146 None => tcx.hir().span(variant_i_hir_id)
2148 let span = match v.disr_expr {
2149 Some(ref expr) => tcx.hir().span(expr.hir_id),
2152 struct_span_err!(tcx.sess, span, E0081,
2153 "discriminant value `{}` already exists", disr_vals[i])
2154 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2155 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
2158 disr_vals.push(discr);
2161 check_representable(tcx, sp, def_id);
2162 check_transparent(tcx, sp, def_id);
2165 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span, qpath: &QPath) {
2166 span_err!(tcx.sess, span, E0533,
2167 "expected unit struct/variant or constant, found {} `{}`",
2169 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
2172 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2173 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2177 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
2178 -> &'tcx ty::GenericPredicates<'tcx>
2181 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2182 let item_id = tcx.hir().ty_param_owner(hir_id);
2183 let item_def_id = tcx.hir().local_def_id(item_id);
2184 let generics = tcx.generics_of(item_def_id);
2185 let index = generics.param_def_id_to_index[&def_id];
2186 tcx.arena.alloc(ty::GenericPredicates {
2188 predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
2190 ty::Predicate::Trait(ref data)
2191 if data.skip_binder().self_ty().is_param(index) => {
2192 // HACK(eddyb) should get the original `Span`.
2193 let span = tcx.def_span(def_id);
2194 Some((predicate, span))
2204 def: Option<&ty::GenericParamDef>,
2206 ) -> Option<ty::Region<'tcx>> {
2208 Some(def) => infer::EarlyBoundRegion(span, def.name),
2209 None => infer::MiscVariable(span)
2211 Some(self.next_region_var(v))
2214 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2215 if let Some(param) = param {
2216 if let UnpackedKind::Type(ty) = self.var_for_def(span, param).unpack() {
2221 self.next_ty_var(TypeVariableOrigin {
2222 kind: TypeVariableOriginKind::TypeInference,
2231 param: Option<&ty::GenericParamDef>,
2233 ) -> &'tcx Const<'tcx> {
2234 if let Some(param) = param {
2235 if let UnpackedKind::Const(ct) = self.var_for_def(span, param).unpack() {
2240 self.next_const_var(ty, ConstVariableOrigin {
2241 kind: ConstVariableOriginKind::ConstInference,
2247 fn projected_ty_from_poly_trait_ref(&self,
2250 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2253 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2255 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2259 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2262 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2263 if ty.has_escaping_bound_vars() {
2264 ty // FIXME: normalization and escaping regions
2266 self.normalize_associated_types_in(span, &ty)
2270 fn set_tainted_by_errors(&self) {
2271 self.infcx.set_tainted_by_errors()
2274 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2275 self.write_ty(hir_id, ty)
2279 /// Controls whether the arguments are tupled. This is used for the call
2282 /// Tupling means that all call-side arguments are packed into a tuple and
2283 /// passed as a single parameter. For example, if tupling is enabled, this
2286 /// fn f(x: (isize, isize))
2288 /// Can be called as:
2295 #[derive(Clone, Eq, PartialEq)]
2296 enum TupleArgumentsFlag {
2301 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2303 inh: &'a Inherited<'a, 'tcx>,
2304 param_env: ty::ParamEnv<'tcx>,
2305 body_id: hir::HirId,
2306 ) -> FnCtxt<'a, 'tcx> {
2310 err_count_on_creation: inh.tcx.sess.err_count(),
2312 ret_coercion_span: RefCell::new(None),
2314 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2315 hir::CRATE_HIR_ID)),
2316 diverges: Cell::new(Diverges::Maybe),
2317 has_errors: Cell::new(false),
2318 enclosing_breakables: RefCell::new(EnclosingBreakables {
2320 by_id: Default::default(),
2326 pub fn sess(&self) -> &Session {
2330 pub fn errors_reported_since_creation(&self) -> bool {
2331 self.tcx.sess.err_count() > self.err_count_on_creation
2334 /// Produces warning on the given node, if the current point in the
2335 /// function is unreachable, and there hasn't been another warning.
2336 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2337 // FIXME: Combine these two 'if' expressions into one once
2338 // let chains are implemented
2339 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2340 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2341 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2342 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2343 if !span.is_desugaring(DesugaringKind::CondTemporary) {
2344 self.diverges.set(Diverges::WarnedAlways);
2346 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2348 let msg = format!("unreachable {}", kind);
2349 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2352 custom_note.unwrap_or("any code following this expression is unreachable")
2361 code: ObligationCauseCode<'tcx>)
2362 -> ObligationCause<'tcx> {
2363 ObligationCause::new(span, self.body_id, code)
2366 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2367 self.cause(span, ObligationCauseCode::MiscObligation)
2370 /// Resolves type variables in `ty` if possible. Unlike the infcx
2371 /// version (resolve_vars_if_possible), this version will
2372 /// also select obligations if it seems useful, in an effort
2373 /// to get more type information.
2374 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2375 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2377 // No Infer()? Nothing needs doing.
2378 if !ty.has_infer_types() {
2379 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2383 // If `ty` is a type variable, see whether we already know what it is.
2384 ty = self.resolve_vars_if_possible(&ty);
2385 if !ty.has_infer_types() {
2386 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2390 // If not, try resolving pending obligations as much as
2391 // possible. This can help substantially when there are
2392 // indirect dependencies that don't seem worth tracking
2394 self.select_obligations_where_possible(false);
2395 ty = self.resolve_vars_if_possible(&ty);
2397 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2401 fn record_deferred_call_resolution(
2403 closure_def_id: DefId,
2404 r: DeferredCallResolution<'tcx>,
2406 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2407 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2410 fn remove_deferred_call_resolutions(
2412 closure_def_id: DefId,
2413 ) -> Vec<DeferredCallResolution<'tcx>> {
2414 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2415 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2418 pub fn tag(&self) -> String {
2419 format!("{:p}", self)
2422 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2423 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2424 span_bug!(span, "no type for local variable {}",
2425 self.tcx.hir().node_to_string(nid))
2430 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2431 debug!("write_ty({:?}, {:?}) in fcx {}",
2432 id, self.resolve_vars_if_possible(&ty), self.tag());
2433 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2435 if ty.references_error() {
2436 self.has_errors.set(true);
2437 self.set_tainted_by_errors();
2441 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2442 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2445 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2446 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2449 pub fn write_method_call(&self,
2451 method: MethodCallee<'tcx>) {
2452 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2453 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2454 self.write_substs(hir_id, method.substs);
2456 // When the method is confirmed, the `method.substs` includes
2457 // parameters from not just the method, but also the impl of
2458 // the method -- in particular, the `Self` type will be fully
2459 // resolved. However, those are not something that the "user
2460 // specified" -- i.e., those types come from the inferred type
2461 // of the receiver, not something the user wrote. So when we
2462 // create the user-substs, we want to replace those earlier
2463 // types with just the types that the user actually wrote --
2464 // that is, those that appear on the *method itself*.
2466 // As an example, if the user wrote something like
2467 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2468 // type of `foo` (possibly adjusted), but we don't want to
2469 // include that. We want just the `[_, u32]` part.
2470 if !method.substs.is_noop() {
2471 let method_generics = self.tcx.generics_of(method.def_id);
2472 if !method_generics.params.is_empty() {
2473 let user_type_annotation = self.infcx.probe(|_| {
2474 let user_substs = UserSubsts {
2475 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2476 let i = param.index as usize;
2477 if i < method_generics.parent_count {
2478 self.infcx.var_for_def(DUMMY_SP, param)
2483 user_self_ty: None, // not relevant here
2486 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2492 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2493 self.write_user_type_annotation(hir_id, user_type_annotation);
2498 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2499 if !substs.is_noop() {
2500 debug!("write_substs({:?}, {:?}) in fcx {}",
2505 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2509 /// Given the substs that we just converted from the HIR, try to
2510 /// canonicalize them and store them as user-given substitutions
2511 /// (i.e., substitutions that must be respected by the NLL check).
2513 /// This should be invoked **before any unifications have
2514 /// occurred**, so that annotations like `Vec<_>` are preserved
2516 pub fn write_user_type_annotation_from_substs(
2520 substs: SubstsRef<'tcx>,
2521 user_self_ty: Option<UserSelfTy<'tcx>>,
2524 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2525 user_self_ty={:?} in fcx {}",
2526 hir_id, def_id, substs, user_self_ty, self.tag(),
2529 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2530 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2531 &UserType::TypeOf(def_id, UserSubsts {
2536 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2537 self.write_user_type_annotation(hir_id, canonicalized);
2541 pub fn write_user_type_annotation(
2544 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2547 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2548 hir_id, canonical_user_type_annotation, self.tag(),
2551 if !canonical_user_type_annotation.is_identity() {
2552 self.tables.borrow_mut().user_provided_types_mut().insert(
2553 hir_id, canonical_user_type_annotation
2556 debug!("write_user_type_annotation: skipping identity substs");
2560 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2561 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2567 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2568 Entry::Vacant(entry) => { entry.insert(adj); },
2569 Entry::Occupied(mut entry) => {
2570 debug!(" - composing on top of {:?}", entry.get());
2571 match (&entry.get()[..], &adj[..]) {
2572 // Applying any adjustment on top of a NeverToAny
2573 // is a valid NeverToAny adjustment, because it can't
2575 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2577 Adjustment { kind: Adjust::Deref(_), .. },
2578 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2580 Adjustment { kind: Adjust::Deref(_), .. },
2581 .. // Any following adjustments are allowed.
2583 // A reborrow has no effect before a dereference.
2585 // FIXME: currently we never try to compose autoderefs
2586 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2588 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2589 expr, entry.get(), adj)
2591 *entry.get_mut() = adj;
2596 /// Basically whenever we are converting from a type scheme into
2597 /// the fn body space, we always want to normalize associated
2598 /// types as well. This function combines the two.
2599 fn instantiate_type_scheme<T>(&self,
2601 substs: SubstsRef<'tcx>,
2604 where T : TypeFoldable<'tcx>
2606 let value = value.subst(self.tcx, substs);
2607 let result = self.normalize_associated_types_in(span, &value);
2608 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2615 /// As `instantiate_type_scheme`, but for the bounds found in a
2616 /// generic type scheme.
2617 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: SubstsRef<'tcx>)
2618 -> ty::InstantiatedPredicates<'tcx> {
2619 let bounds = self.tcx.predicates_of(def_id);
2620 let result = bounds.instantiate(self.tcx, substs);
2621 let result = self.normalize_associated_types_in(span, &result);
2622 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
2629 /// Replaces the opaque types from the given value with type variables,
2630 /// and records the `OpaqueTypeMap` for later use during writeback. See
2631 /// `InferCtxt::instantiate_opaque_types` for more details.
2632 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2634 parent_id: hir::HirId,
2638 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2639 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2643 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2644 self.instantiate_opaque_types(
2653 let mut opaque_types = self.opaque_types.borrow_mut();
2654 for (ty, decl) in opaque_type_map {
2655 let old_value = opaque_types.insert(ty, decl);
2656 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2662 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2663 where T : TypeFoldable<'tcx>
2665 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2668 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2670 where T : TypeFoldable<'tcx>
2672 self.inh.partially_normalize_associated_types_in(span,
2678 pub fn require_type_meets(&self,
2681 code: traits::ObligationCauseCode<'tcx>,
2684 self.register_bound(
2687 traits::ObligationCause::new(span, self.body_id, code));
2690 pub fn require_type_is_sized(&self,
2693 code: traits::ObligationCauseCode<'tcx>)
2695 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2696 self.require_type_meets(ty, span, code, lang_item);
2699 pub fn require_type_is_sized_deferred(&self,
2702 code: traits::ObligationCauseCode<'tcx>)
2704 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2707 pub fn register_bound(&self,
2710 cause: traits::ObligationCause<'tcx>)
2712 self.fulfillment_cx.borrow_mut()
2713 .register_bound(self, self.param_env, ty, def_id, cause);
2716 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2717 let t = AstConv::ast_ty_to_ty(self, ast_t);
2718 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2722 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2723 let ty = self.to_ty(ast_ty);
2724 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2726 if Self::can_contain_user_lifetime_bounds(ty) {
2727 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2728 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2729 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2735 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2736 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2737 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2740 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2741 AstConv::ast_const_to_const(self, ast_c, ty)
2744 // If the type given by the user has free regions, save it for later, since
2745 // NLL would like to enforce those. Also pass in types that involve
2746 // projections, since those can resolve to `'static` bounds (modulo #54940,
2747 // which hopefully will be fixed by the time you see this comment, dear
2748 // reader, although I have my doubts). Also pass in types with inference
2749 // types, because they may be repeated. Other sorts of things are already
2750 // sufficiently enforced with erased regions. =)
2751 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2753 T: TypeFoldable<'tcx>
2755 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2758 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2759 match self.tables.borrow().node_types().get(id) {
2761 None if self.is_tainted_by_errors() => self.tcx.types.err,
2763 bug!("no type for node {}: {} in fcx {}",
2764 id, self.tcx.hir().node_to_string(id),
2770 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2771 /// outlive the region `r`.
2772 pub fn register_wf_obligation(&self,
2775 code: traits::ObligationCauseCode<'tcx>)
2777 // WF obligations never themselves fail, so no real need to give a detailed cause:
2778 let cause = traits::ObligationCause::new(span, self.body_id, code);
2779 self.register_predicate(traits::Obligation::new(cause,
2781 ty::Predicate::WellFormed(ty)));
2784 /// Registers obligations that all types appearing in `substs` are well-formed.
2785 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2786 for ty in substs.types() {
2787 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2791 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2792 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2793 /// trait/region obligations.
2795 /// For example, if there is a function:
2798 /// fn foo<'a,T:'a>(...)
2801 /// and a reference:
2807 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2808 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2809 pub fn add_obligations_for_parameters(&self,
2810 cause: traits::ObligationCause<'tcx>,
2811 predicates: &ty::InstantiatedPredicates<'tcx>)
2813 assert!(!predicates.has_escaping_bound_vars());
2815 debug!("add_obligations_for_parameters(predicates={:?})",
2818 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2819 self.register_predicate(obligation);
2823 // FIXME(arielb1): use this instead of field.ty everywhere
2824 // Only for fields! Returns <none> for methods>
2825 // Indifferent to privacy flags
2826 pub fn field_ty(&self,
2828 field: &'tcx ty::FieldDef,
2829 substs: SubstsRef<'tcx>)
2832 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2835 fn check_casts(&self) {
2836 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2837 for cast in deferred_cast_checks.drain(..) {
2842 fn resolve_generator_interiors(&self, def_id: DefId) {
2843 let mut generators = self.deferred_generator_interiors.borrow_mut();
2844 for (body_id, interior, kind) in generators.drain(..) {
2845 self.select_obligations_where_possible(false);
2846 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2850 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2851 // Non-numerics get replaced with ! or () (depending on whether
2852 // feature(never_type) is enabled, unconstrained ints with i32,
2853 // unconstrained floats with f64.
2854 // Fallback becomes very dubious if we have encountered type-checking errors.
2855 // In that case, fallback to Error.
2856 // The return value indicates whether fallback has occurred.
2857 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2858 use rustc::ty::error::UnconstrainedNumeric::Neither;
2859 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2861 assert!(ty.is_ty_infer());
2862 let fallback = match self.type_is_unconstrained_numeric(ty) {
2863 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2864 UnconstrainedInt => self.tcx.types.i32,
2865 UnconstrainedFloat => self.tcx.types.f64,
2866 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2867 Neither => return false,
2869 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2870 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2874 fn select_all_obligations_or_error(&self) {
2875 debug!("select_all_obligations_or_error");
2876 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2877 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2881 /// Select as many obligations as we can at present.
2882 fn select_obligations_where_possible(&self, fallback_has_occurred: bool) {
2883 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2884 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2888 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2889 /// returns a type of `&T`, but the actual type we assign to the
2890 /// *expression* is `T`. So this function just peels off the return
2891 /// type by one layer to yield `T`.
2892 fn make_overloaded_place_return_type(&self,
2893 method: MethodCallee<'tcx>)
2894 -> ty::TypeAndMut<'tcx>
2896 // extract method return type, which will be &T;
2897 let ret_ty = method.sig.output();
2899 // method returns &T, but the type as visible to user is T, so deref
2900 ret_ty.builtin_deref(true).unwrap()
2906 base_expr: &'tcx hir::Expr,
2910 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2911 // FIXME(#18741) -- this is almost but not quite the same as the
2912 // autoderef that normal method probing does. They could likely be
2915 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2916 let mut result = None;
2917 while result.is_none() && autoderef.next().is_some() {
2918 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2920 autoderef.finalize(self);
2924 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2925 /// (and otherwise adjust) `base_expr`, looking for a type which either
2926 /// supports builtin indexing or overloaded indexing.
2927 /// This loop implements one step in that search; the autoderef loop
2928 /// is implemented by `lookup_indexing`.
2932 base_expr: &hir::Expr,
2933 autoderef: &Autoderef<'a, 'tcx>,
2936 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2937 let adjusted_ty = autoderef.unambiguous_final_ty(self);
2938 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2945 for &unsize in &[false, true] {
2946 let mut self_ty = adjusted_ty;
2948 // We only unsize arrays here.
2949 if let ty::Array(element_ty, _) = adjusted_ty.sty {
2950 self_ty = self.tcx.mk_slice(element_ty);
2956 // If some lookup succeeds, write callee into table and extract index/element
2957 // type from the method signature.
2958 // If some lookup succeeded, install method in table
2959 let input_ty = self.next_ty_var(TypeVariableOrigin {
2960 kind: TypeVariableOriginKind::AutoDeref,
2961 span: base_expr.span,
2963 let method = self.try_overloaded_place_op(
2964 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
2966 let result = method.map(|ok| {
2967 debug!("try_index_step: success, using overloaded indexing");
2968 let method = self.register_infer_ok_obligations(ok);
2970 let mut adjustments = autoderef.adjust_steps(self, needs);
2971 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].sty {
2972 let mutbl = match r_mutbl {
2973 hir::MutImmutable => AutoBorrowMutability::Immutable,
2974 hir::MutMutable => AutoBorrowMutability::Mutable {
2975 // Indexing can be desugared to a method call,
2976 // so maybe we could use two-phase here.
2977 // See the documentation of AllowTwoPhase for why that's
2978 // not the case today.
2979 allow_two_phase_borrow: AllowTwoPhase::No,
2982 adjustments.push(Adjustment {
2983 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
2984 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2991 adjustments.push(Adjustment {
2992 kind: Adjust::Pointer(PointerCast::Unsize),
2993 target: method.sig.inputs()[0]
2996 self.apply_adjustments(base_expr, adjustments);
2998 self.write_method_call(expr.hir_id, method);
2999 (input_ty, self.make_overloaded_place_return_type(method).ty)
3001 if result.is_some() {
3009 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3010 let (tr, name) = match (op, is_mut) {
3011 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3012 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3013 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3014 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3016 (tr, ast::Ident::with_dummy_span(name))
3019 fn try_overloaded_place_op(&self,
3022 arg_tys: &[Ty<'tcx>],
3025 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3027 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3033 // Try Mut first, if needed.
3034 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3035 let method = match (needs, mut_tr) {
3036 (Needs::MutPlace, Some(trait_did)) => {
3037 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3042 // Otherwise, fall back to the immutable version.
3043 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3044 let method = match (method, imm_tr) {
3045 (None, Some(trait_did)) => {
3046 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3048 (method, _) => method,
3054 fn check_method_argument_types(
3058 method: Result<MethodCallee<'tcx>, ()>,
3059 args_no_rcvr: &'tcx [hir::Expr],
3060 tuple_arguments: TupleArgumentsFlag,
3061 expected: Expectation<'tcx>,
3063 let has_error = match method {
3065 method.substs.references_error() || method.sig.references_error()
3070 let err_inputs = self.err_args(args_no_rcvr.len());
3072 let err_inputs = match tuple_arguments {
3073 DontTupleArguments => err_inputs,
3074 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3077 self.check_argument_types(sp, expr_sp, &err_inputs[..], &[], args_no_rcvr,
3078 false, tuple_arguments, None);
3079 return self.tcx.types.err;
3082 let method = method.unwrap();
3083 // HACK(eddyb) ignore self in the definition (see above).
3084 let expected_arg_tys = self.expected_inputs_for_expected_output(
3087 method.sig.output(),
3088 &method.sig.inputs()[1..]
3090 self.check_argument_types(sp, expr_sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
3091 args_no_rcvr, method.sig.c_variadic, tuple_arguments,
3092 self.tcx.hir().span_if_local(method.def_id));
3096 fn self_type_matches_expected_vid(
3098 trait_ref: ty::PolyTraitRef<'tcx>,
3099 expected_vid: ty::TyVid,
3101 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3103 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3104 trait_ref, self_ty, expected_vid
3107 ty::Infer(ty::TyVar(found_vid)) => {
3108 // FIXME: consider using `sub_root_var` here so we
3109 // can see through subtyping.
3110 let found_vid = self.root_var(found_vid);
3111 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3112 expected_vid == found_vid
3118 fn obligations_for_self_ty<'b>(
3121 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3124 // FIXME: consider using `sub_root_var` here so we
3125 // can see through subtyping.
3126 let ty_var_root = self.root_var(self_ty);
3127 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3128 self_ty, ty_var_root,
3129 self.fulfillment_cx.borrow().pending_obligations());
3133 .pending_obligations()
3135 .filter_map(move |obligation| match obligation.predicate {
3136 ty::Predicate::Projection(ref data) =>
3137 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3138 ty::Predicate::Trait(ref data) =>
3139 Some((data.to_poly_trait_ref(), obligation)),
3140 ty::Predicate::Subtype(..) => None,
3141 ty::Predicate::RegionOutlives(..) => None,
3142 ty::Predicate::TypeOutlives(..) => None,
3143 ty::Predicate::WellFormed(..) => None,
3144 ty::Predicate::ObjectSafe(..) => None,
3145 ty::Predicate::ConstEvaluatable(..) => None,
3146 // N.B., this predicate is created by breaking down a
3147 // `ClosureType: FnFoo()` predicate, where
3148 // `ClosureType` represents some `Closure`. It can't
3149 // possibly be referring to the current closure,
3150 // because we haven't produced the `Closure` for
3151 // this closure yet; this is exactly why the other
3152 // code is looking for a self type of a unresolved
3153 // inference variable.
3154 ty::Predicate::ClosureKind(..) => None,
3155 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3158 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3159 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3160 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3164 /// Generic function that factors out common logic from function calls,
3165 /// method calls and overloaded operators.
3166 fn check_argument_types(
3170 fn_inputs: &[Ty<'tcx>],
3171 expected_arg_tys: &[Ty<'tcx>],
3172 args: &'tcx [hir::Expr],
3174 tuple_arguments: TupleArgumentsFlag,
3175 def_span: Option<Span>,
3179 // Grab the argument types, supplying fresh type variables
3180 // if the wrong number of arguments were supplied
3181 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3187 // All the input types from the fn signature must outlive the call
3188 // so as to validate implied bounds.
3189 for &fn_input_ty in fn_inputs {
3190 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
3193 let expected_arg_count = fn_inputs.len();
3195 let param_count_error = |expected_count: usize,
3200 let mut err = tcx.sess.struct_span_err_with_code(sp,
3201 &format!("this function takes {}{} but {} {} supplied",
3202 if c_variadic { "at least " } else { "" },
3203 potentially_plural_count(expected_count, "parameter"),
3204 potentially_plural_count(arg_count, "parameter"),
3205 if arg_count == 1 {"was"} else {"were"}),
3206 DiagnosticId::Error(error_code.to_owned()));
3208 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3209 err.span_label(def_s, "defined here");
3212 let sugg_span = tcx.sess.source_map().end_point(expr_sp);
3213 // remove closing `)` from the span
3214 let sugg_span = sugg_span.shrink_to_lo();
3215 err.span_suggestion(
3217 "expected the unit value `()`; create it with empty parentheses",
3219 Applicability::MachineApplicable);
3221 err.span_label(sp, format!("expected {}{}",
3222 if c_variadic { "at least " } else { "" },
3223 potentially_plural_count(expected_count, "parameter")));
3228 let mut expected_arg_tys = expected_arg_tys.to_vec();
3230 let formal_tys = if tuple_arguments == TupleArguments {
3231 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3232 match tuple_type.sty {
3233 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3234 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3235 expected_arg_tys = vec![];
3236 self.err_args(args.len())
3238 ty::Tuple(arg_types) => {
3239 expected_arg_tys = match expected_arg_tys.get(0) {
3240 Some(&ty) => match ty.sty {
3241 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3246 arg_types.iter().map(|k| k.expect_ty()).collect()
3249 span_err!(tcx.sess, sp, E0059,
3250 "cannot use call notation; the first type parameter \
3251 for the function trait is neither a tuple nor unit");
3252 expected_arg_tys = vec![];
3253 self.err_args(args.len())
3256 } else if expected_arg_count == supplied_arg_count {
3258 } else if c_variadic {
3259 if supplied_arg_count >= expected_arg_count {
3262 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3263 expected_arg_tys = vec![];
3264 self.err_args(supplied_arg_count)
3267 // is the missing argument of type `()`?
3268 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3269 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3270 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3271 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3275 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3277 expected_arg_tys = vec![];
3278 self.err_args(supplied_arg_count)
3281 debug!("check_argument_types: formal_tys={:?}",
3282 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3284 // If there is no expectation, expect formal_tys.
3285 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3291 // Check the arguments.
3292 // We do this in a pretty awful way: first we type-check any arguments
3293 // that are not closures, then we type-check the closures. This is so
3294 // that we have more information about the types of arguments when we
3295 // type-check the functions. This isn't really the right way to do this.
3296 for &check_closures in &[false, true] {
3297 debug!("check_closures={}", check_closures);
3299 // More awful hacks: before we check argument types, try to do
3300 // an "opportunistic" vtable resolution of any trait bounds on
3301 // the call. This helps coercions.
3303 self.select_obligations_where_possible(false);
3306 // For C-variadic functions, we don't have a declared type for all of
3307 // the arguments hence we only do our usual type checking with
3308 // the arguments who's types we do know.
3309 let t = if c_variadic {
3311 } else if tuple_arguments == TupleArguments {
3316 for (i, arg) in args.iter().take(t).enumerate() {
3317 // Warn only for the first loop (the "no closures" one).
3318 // Closure arguments themselves can't be diverging, but
3319 // a previous argument can, e.g., `foo(panic!(), || {})`.
3320 if !check_closures {
3321 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3324 let is_closure = match arg.node {
3325 ExprKind::Closure(..) => true,
3329 if is_closure != check_closures {
3333 debug!("checking the argument");
3334 let formal_ty = formal_tys[i];
3336 // The special-cased logic below has three functions:
3337 // 1. Provide as good of an expected type as possible.
3338 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3340 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3342 // 2. Coerce to the most detailed type that could be coerced
3343 // to, which is `expected_ty` if `rvalue_hint` returns an
3344 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3345 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3346 // We're processing function arguments so we definitely want to use
3347 // two-phase borrows.
3348 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3350 // 3. Relate the expected type and the formal one,
3351 // if the expected type was used for the coercion.
3352 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3356 // We also need to make sure we at least write the ty of the other
3357 // arguments which we skipped above.
3359 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3360 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3361 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3364 for arg in args.iter().skip(expected_arg_count) {
3365 let arg_ty = self.check_expr(&arg);
3367 // There are a few types which get autopromoted when passed via varargs
3368 // in C but we just error out instead and require explicit casts.
3369 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3371 ty::Float(ast::FloatTy::F32) => {
3372 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3374 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3375 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3377 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3378 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3381 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3382 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3383 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3391 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3392 vec![self.tcx.types.err; len]
3395 // AST fragment checking
3398 expected: Expectation<'tcx>)
3404 ast::LitKind::Str(..) => tcx.mk_static_str(),
3405 ast::LitKind::ByteStr(ref v) => {
3406 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3407 tcx.mk_array(tcx.types.u8, v.len() as u64))
3409 ast::LitKind::Byte(_) => tcx.types.u8,
3410 ast::LitKind::Char(_) => tcx.types.char,
3411 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3412 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3413 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3414 let opt_ty = expected.to_option(self).and_then(|ty| {
3416 ty::Int(_) | ty::Uint(_) => Some(ty),
3417 ty::Char => Some(tcx.types.u8),
3418 ty::RawPtr(..) => Some(tcx.types.usize),
3419 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3423 opt_ty.unwrap_or_else(|| self.next_int_var())
3425 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3426 ast::LitKind::FloatUnsuffixed(_) => {
3427 let opt_ty = expected.to_option(self).and_then(|ty| {
3429 ty::Float(_) => Some(ty),
3433 opt_ty.unwrap_or_else(|| self.next_float_var())
3435 ast::LitKind::Bool(_) => tcx.types.bool,
3436 ast::LitKind::Err(_) => tcx.types.err,
3440 // Determine the `Self` type, using fresh variables for all variables
3441 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3442 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3444 pub fn impl_self_ty(&self,
3445 span: Span, // (potential) receiver for this impl
3447 -> TypeAndSubsts<'tcx> {
3448 let ity = self.tcx.type_of(did);
3449 debug!("impl_self_ty: ity={:?}", ity);
3451 let substs = self.fresh_substs_for_item(span, did);
3452 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3454 TypeAndSubsts { substs: substs, ty: substd_ty }
3457 /// Unifies the output type with the expected type early, for more coercions
3458 /// and forward type information on the input expressions.
3459 fn expected_inputs_for_expected_output(&self,
3461 expected_ret: Expectation<'tcx>,
3462 formal_ret: Ty<'tcx>,
3463 formal_args: &[Ty<'tcx>])
3465 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3466 let ret_ty = match expected_ret.only_has_type(self) {
3468 None => return Vec::new()
3470 let expect_args = self.fudge_inference_if_ok(|| {
3471 // Attempt to apply a subtyping relationship between the formal
3472 // return type (likely containing type variables if the function
3473 // is polymorphic) and the expected return type.
3474 // No argument expectations are produced if unification fails.
3475 let origin = self.misc(call_span);
3476 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3478 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3479 // to identity so the resulting type is not constrained.
3482 // Process any obligations locally as much as
3483 // we can. We don't care if some things turn
3484 // out unconstrained or ambiguous, as we're
3485 // just trying to get hints here.
3486 self.save_and_restore_in_snapshot_flag(|_| {
3487 let mut fulfill = TraitEngine::new(self.tcx);
3488 for obligation in ok.obligations {
3489 fulfill.register_predicate_obligation(self, obligation);
3491 fulfill.select_where_possible(self)
3492 }).map_err(|_| ())?;
3494 Err(_) => return Err(()),
3497 // Record all the argument types, with the substitutions
3498 // produced from the above subtyping unification.
3499 Ok(formal_args.iter().map(|ty| {
3500 self.resolve_vars_if_possible(ty)
3502 }).unwrap_or_default();
3503 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3504 formal_args, formal_ret,
3505 expect_args, expected_ret);
3509 pub fn check_struct_path(&self,
3512 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3513 let path_span = match *qpath {
3514 QPath::Resolved(_, ref path) => path.span,
3515 QPath::TypeRelative(ref qself, _) => qself.span
3517 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3518 let variant = match def {
3520 self.set_tainted_by_errors();
3523 Res::Def(DefKind::Variant, _) => {
3525 ty::Adt(adt, substs) => {
3526 Some((adt.variant_of_res(def), adt.did, substs))
3528 _ => bug!("unexpected type: {:?}", ty)
3531 Res::Def(DefKind::Struct, _)
3532 | Res::Def(DefKind::Union, _)
3533 | Res::Def(DefKind::TyAlias, _)
3534 | Res::Def(DefKind::AssocTy, _)
3535 | Res::SelfTy(..) => {
3537 ty::Adt(adt, substs) if !adt.is_enum() => {
3538 Some((adt.non_enum_variant(), adt.did, substs))
3543 _ => bug!("unexpected definition: {:?}", def)
3546 if let Some((variant, did, substs)) = variant {
3547 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3548 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3550 // Check bounds on type arguments used in the path.
3551 let bounds = self.instantiate_bounds(path_span, did, substs);
3552 let cause = traits::ObligationCause::new(path_span, self.body_id,
3553 traits::ItemObligation(did));
3554 self.add_obligations_for_parameters(cause, &bounds);
3558 struct_span_err!(self.tcx.sess, path_span, E0071,
3559 "expected struct, variant or union type, found {}",
3560 ty.sort_string(self.tcx))
3561 .span_label(path_span, "not a struct")
3567 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3568 // The newly resolved definition is written into `type_dependent_defs`.
3569 fn finish_resolving_struct_path(&self,
3576 QPath::Resolved(ref maybe_qself, ref path) => {
3577 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3578 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3581 QPath::TypeRelative(ref qself, ref segment) => {
3582 let ty = self.to_ty(qself);
3584 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.node {
3589 let result = AstConv::associated_path_to_ty(
3598 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3599 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3601 // Write back the new resolution.
3602 self.write_resolution(hir_id, result);
3604 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3609 /// Resolves an associated value path into a base type and associated constant, or method
3610 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3611 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3615 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3617 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3618 let (ty, qself, item_segment) = match *qpath {
3619 QPath::Resolved(ref opt_qself, ref path) => {
3621 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3622 &path.segments[..]);
3624 QPath::TypeRelative(ref qself, ref segment) => {
3625 (self.to_ty(qself), qself, segment)
3628 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3629 // Return directly on cache hit. This is useful to avoid doubly reporting
3630 // errors with default match binding modes. See #44614.
3631 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3632 .unwrap_or(Res::Err);
3633 return (def, Some(ty), slice::from_ref(&**item_segment));
3635 let item_name = item_segment.ident;
3636 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3637 let result = match error {
3638 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3639 _ => Err(ErrorReported),
3641 if item_name.name != kw::Invalid {
3642 self.report_method_error(
3646 SelfSource::QPath(qself),
3649 ).map(|mut e| e.emit());
3654 // Write back the new resolution.
3655 self.write_resolution(hir_id, result);
3657 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3659 slice::from_ref(&**item_segment),
3663 pub fn check_decl_initializer(
3665 local: &'tcx hir::Local,
3666 init: &'tcx hir::Expr,
3668 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3669 // for #42640 (default match binding modes).
3672 let ref_bindings = local.pat.contains_explicit_ref_binding();
3674 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3675 if let Some(m) = ref_bindings {
3676 // Somewhat subtle: if we have a `ref` binding in the pattern,
3677 // we want to avoid introducing coercions for the RHS. This is
3678 // both because it helps preserve sanity and, in the case of
3679 // ref mut, for soundness (issue #23116). In particular, in
3680 // the latter case, we need to be clear that the type of the
3681 // referent for the reference that results is *equal to* the
3682 // type of the place it is referencing, and not some
3683 // supertype thereof.
3684 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3685 self.demand_eqtype(init.span, local_ty, init_ty);
3688 self.check_expr_coercable_to_type(init, local_ty)
3692 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3693 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3694 self.write_ty(local.hir_id, t);
3696 if let Some(ref init) = local.init {
3697 let init_ty = self.check_decl_initializer(local, &init);
3698 if init_ty.references_error() {
3699 self.write_ty(local.hir_id, init_ty);
3703 self.check_pat_top(&local.pat, t, None);
3704 let pat_ty = self.node_ty(local.pat.hir_id);
3705 if pat_ty.references_error() {
3706 self.write_ty(local.hir_id, pat_ty);
3710 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3711 // Don't do all the complex logic below for `DeclItem`.
3713 hir::StmtKind::Item(..) => return,
3714 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3717 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3719 // Hide the outer diverging and `has_errors` flags.
3720 let old_diverges = self.diverges.get();
3721 let old_has_errors = self.has_errors.get();
3722 self.diverges.set(Diverges::Maybe);
3723 self.has_errors.set(false);
3726 hir::StmtKind::Local(ref l) => {
3727 self.check_decl_local(&l);
3730 hir::StmtKind::Item(_) => {}
3731 hir::StmtKind::Expr(ref expr) => {
3732 // Check with expected type of `()`.
3733 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit());
3735 hir::StmtKind::Semi(ref expr) => {
3736 self.check_expr(&expr);
3740 // Combine the diverging and `has_error` flags.
3741 self.diverges.set(self.diverges.get() | old_diverges);
3742 self.has_errors.set(self.has_errors.get() | old_has_errors);
3745 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
3746 let unit = self.tcx.mk_unit();
3747 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
3749 // if the block produces a `!` value, that can always be
3750 // (effectively) coerced to unit.
3752 self.demand_suptype(blk.span, unit, ty);
3756 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
3757 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
3758 /// when given code like the following:
3760 /// if false { return 0i32; } else { 1u32 }
3761 /// // ^^^^ point at this instead of the whole `if` expression
3763 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
3764 if let hir::ExprKind::Match(_, arms, _) = &expr.node {
3765 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
3766 self.in_progress_tables
3767 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
3768 .and_then(|arm_ty| {
3769 if arm_ty.is_never() {
3772 Some(match &arm.body.node {
3773 // Point at the tail expression when possible.
3774 hir::ExprKind::Block(block, _) => block.expr
3777 .unwrap_or(block.span),
3783 if arm_spans.len() == 1 {
3784 return arm_spans[0];
3790 fn check_block_with_expected(
3792 blk: &'tcx hir::Block,
3793 expected: Expectation<'tcx>,
3796 let mut fcx_ps = self.ps.borrow_mut();
3797 let unsafety_state = fcx_ps.recurse(blk);
3798 replace(&mut *fcx_ps, unsafety_state)
3801 // In some cases, blocks have just one exit, but other blocks
3802 // can be targeted by multiple breaks. This can happen both
3803 // with labeled blocks as well as when we desugar
3804 // a `try { ... }` expression.
3808 // 'a: { if true { break 'a Err(()); } Ok(()) }
3810 // Here we would wind up with two coercions, one from
3811 // `Err(())` and the other from the tail expression
3812 // `Ok(())`. If the tail expression is omitted, that's a
3813 // "forced unit" -- unless the block diverges, in which
3814 // case we can ignore the tail expression (e.g., `'a: {
3815 // break 'a 22; }` would not force the type of the block
3817 let tail_expr = blk.expr.as_ref();
3818 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
3819 let coerce = if blk.targeted_by_break {
3820 CoerceMany::new(coerce_to_ty)
3822 let tail_expr: &[P<hir::Expr>] = match tail_expr {
3823 Some(e) => slice::from_ref(e),
3826 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
3829 let prev_diverges = self.diverges.get();
3830 let ctxt = BreakableCtxt {
3831 coerce: Some(coerce),
3835 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
3836 for s in &blk.stmts {
3840 // check the tail expression **without** holding the
3841 // `enclosing_breakables` lock below.
3842 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
3844 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3845 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
3846 let coerce = ctxt.coerce.as_mut().unwrap();
3847 if let Some(tail_expr_ty) = tail_expr_ty {
3848 let tail_expr = tail_expr.unwrap();
3849 let span = self.get_expr_coercion_span(tail_expr);
3850 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
3851 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
3853 // Subtle: if there is no explicit tail expression,
3854 // that is typically equivalent to a tail expression
3855 // of `()` -- except if the block diverges. In that
3856 // case, there is no value supplied from the tail
3857 // expression (assuming there are no other breaks,
3858 // this implies that the type of the block will be
3861 // #41425 -- label the implicit `()` as being the
3862 // "found type" here, rather than the "expected type".
3863 if !self.diverges.get().is_always() {
3864 // #50009 -- Do not point at the entire fn block span, point at the return type
3865 // span, as it is the cause of the requirement, and
3866 // `consider_hint_about_removing_semicolon` will point at the last expression
3867 // if it were a relevant part of the error. This improves usability in editors
3868 // that highlight errors inline.
3869 let mut sp = blk.span;
3870 let mut fn_span = None;
3871 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
3872 let ret_sp = decl.output.span();
3873 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
3874 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
3875 // output would otherwise be incorrect and even misleading. Make sure
3876 // the span we're aiming at correspond to a `fn` body.
3877 if block_sp == blk.span {
3879 fn_span = Some(ident.span);
3883 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
3884 if let Some(expected_ty) = expected.only_has_type(self) {
3885 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
3887 if let Some(fn_span) = fn_span {
3890 "implicitly returns `()` as its body has no tail or `return` \
3900 // If we can break from the block, then the block's exit is always reachable
3901 // (... as long as the entry is reachable) - regardless of the tail of the block.
3902 self.diverges.set(prev_diverges);
3905 let mut ty = ctxt.coerce.unwrap().complete(self);
3907 if self.has_errors.get() || ty.references_error() {
3908 ty = self.tcx.types.err
3911 self.write_ty(blk.hir_id, ty);
3913 *self.ps.borrow_mut() = prev;
3917 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
3918 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
3920 Node::Item(&hir::Item {
3921 node: hir::ItemKind::Fn(_, _, _, body_id), ..
3923 Node::ImplItem(&hir::ImplItem {
3924 node: hir::ImplItemKind::Method(_, body_id), ..
3926 let body = self.tcx.hir().body(body_id);
3927 if let ExprKind::Block(block, _) = &body.value.node {
3928 return Some(block.span);
3936 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
3937 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
3938 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
3939 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
3942 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
3943 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
3945 Node::Item(&hir::Item {
3946 ident, node: hir::ItemKind::Fn(ref decl, ..), ..
3948 // This is less than ideal, it will not suggest a return type span on any
3949 // method called `main`, regardless of whether it is actually the entry point,
3950 // but it will still present it as the reason for the expected type.
3951 Some((decl, ident, ident.name != sym::main))
3953 Node::TraitItem(&hir::TraitItem {
3954 ident, node: hir::TraitItemKind::Method(hir::MethodSig {
3957 }) => Some((decl, ident, true)),
3958 Node::ImplItem(&hir::ImplItem {
3959 ident, node: hir::ImplItemKind::Method(hir::MethodSig {
3962 }) => Some((decl, ident, false)),
3967 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
3968 /// suggestion can be made, `None` otherwise.
3969 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
3970 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
3971 // `while` before reaching it, as block tail returns are not available in them.
3972 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
3973 let parent = self.tcx.hir().get(blk_id);
3974 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
3978 /// On implicit return expressions with mismatched types, provides the following suggestions:
3980 /// - Points out the method's return type as the reason for the expected type.
3981 /// - Possible missing semicolon.
3982 /// - Possible missing return type if the return type is the default, and not `fn main()`.
3983 pub fn suggest_mismatched_types_on_tail(
3985 err: &mut DiagnosticBuilder<'tcx>,
3986 expression: &'tcx hir::Expr,
3992 self.suggest_missing_semicolon(err, expression, expected, cause_span);
3993 let mut pointing_at_return_type = false;
3994 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
3995 pointing_at_return_type = self.suggest_missing_return_type(
3996 err, &fn_decl, expected, found, can_suggest);
3998 self.suggest_ref_or_into(err, expression, expected, found);
3999 self.suggest_boxing_when_appropriate(err, expression, expected, found);
4000 pointing_at_return_type
4003 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4004 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4006 /// fn foo(x: usize) -> usize { x }
4007 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4011 err: &mut DiagnosticBuilder<'tcx>,
4016 let hir = self.tcx.hir();
4017 let (def_id, sig) = match found.sty {
4018 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4019 ty::Closure(def_id, substs) => {
4020 // We don't use `closure_sig` to account for malformed closures like
4021 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4022 let closure_sig_ty = substs.closure_sig_ty(def_id, self.tcx);
4023 (def_id, match closure_sig_ty.sty {
4024 ty::FnPtr(sig) => sig,
4032 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4034 let sig = self.normalize_associated_types_in(expr.span, &sig);
4035 if self.can_coerce(sig.output(), expected) {
4036 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4037 (String::new(), Applicability::MachineApplicable)
4039 ("...".to_string(), Applicability::HasPlaceholders)
4041 let mut msg = "call this function";
4042 match hir.get_if_local(def_id) {
4043 Some(Node::Item(hir::Item {
4044 node: ItemKind::Fn(.., body_id),
4047 Some(Node::ImplItem(hir::ImplItem {
4048 node: hir::ImplItemKind::Method(_, body_id),
4051 Some(Node::TraitItem(hir::TraitItem {
4052 node: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4055 let body = hir.body(*body_id);
4056 sugg_call = body.params.iter()
4057 .map(|param| match ¶m.pat.node {
4058 hir::PatKind::Binding(_, _, ident, None)
4059 if ident.name != kw::SelfLower => ident.to_string(),
4060 _ => "_".to_string(),
4061 }).collect::<Vec<_>>().join(", ");
4063 Some(Node::Expr(hir::Expr {
4064 node: ExprKind::Closure(_, _, body_id, closure_span, _),
4065 span: full_closure_span,
4068 if *full_closure_span == expr.span {
4071 err.span_label(*closure_span, "closure defined here");
4072 msg = "call this closure";
4073 let body = hir.body(*body_id);
4074 sugg_call = body.params.iter()
4075 .map(|param| match ¶m.pat.node {
4076 hir::PatKind::Binding(_, _, ident, None)
4077 if ident.name != kw::SelfLower => ident.to_string(),
4078 _ => "_".to_string(),
4079 }).collect::<Vec<_>>().join(", ");
4081 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4082 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4083 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4084 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4085 msg = "instantiate this tuple variant";
4087 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4088 msg = "instantiate this tuple struct";
4093 Some(Node::ForeignItem(hir::ForeignItem {
4094 node: hir::ForeignItemKind::Fn(_, idents, _),
4097 Some(Node::TraitItem(hir::TraitItem {
4098 node: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4100 })) => sugg_call = idents.iter()
4101 .map(|ident| if ident.name != kw::SelfLower {
4105 }).collect::<Vec<_>>()
4109 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4110 err.span_suggestion(
4112 &format!("use parentheses to {}", msg),
4113 format!("{}({})", code, sugg_call),
4122 pub fn suggest_ref_or_into(
4124 err: &mut DiagnosticBuilder<'tcx>,
4129 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4130 err.span_suggestion(
4134 Applicability::MachineApplicable,
4136 } else if let (ty::FnDef(def_id, ..), true) = (
4138 self.suggest_fn_call(err, expr, expected, found),
4140 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4141 let sp = self.sess().source_map().def_span(sp);
4142 err.span_label(sp, &format!("{} defined here", found));
4144 } else if !self.check_for_cast(err, expr, found, expected) {
4145 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4149 let methods = self.get_conversion_methods(expr.span, expected, found);
4150 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4151 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4152 .filter_map(|(receiver, method)| {
4153 let method_call = format!(".{}()", method.ident);
4154 if receiver.ends_with(&method_call) {
4155 None // do not suggest code that is already there (#53348)
4157 let method_call_list = [".to_vec()", ".to_string()"];
4158 let sugg = if receiver.ends_with(".clone()")
4159 && method_call_list.contains(&method_call.as_str()) {
4160 let max_len = receiver.rfind(".").unwrap();
4161 format!("{}{}", &receiver[..max_len], method_call)
4163 format!("{}{}", receiver, method_call)
4165 Some(if is_struct_pat_shorthand_field {
4166 format!("{}: {}", receiver, sugg)
4172 if suggestions.peek().is_some() {
4173 err.span_suggestions(
4175 "try using a conversion method",
4177 Applicability::MaybeIncorrect,
4184 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4185 /// in the heap by calling `Box::new()`.
4186 fn suggest_boxing_when_appropriate(
4188 err: &mut DiagnosticBuilder<'tcx>,
4193 if self.tcx.hir().is_const_context(expr.hir_id) {
4194 // Do not suggest `Box::new` in const context.
4197 if !expected.is_box() || found.is_box() {
4200 let boxed_found = self.tcx.mk_box(found);
4201 if let (true, Ok(snippet)) = (
4202 self.can_coerce(boxed_found, expected),
4203 self.sess().source_map().span_to_snippet(expr.span),
4205 err.span_suggestion(
4207 "store this in the heap by calling `Box::new`",
4208 format!("Box::new({})", snippet),
4209 Applicability::MachineApplicable,
4211 err.note("for more on the distinction between the stack and the \
4212 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4213 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4214 https://doc.rust-lang.org/std/boxed/index.html");
4219 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4223 /// bar_that_returns_u32()
4227 /// This routine checks if the return expression in a block would make sense on its own as a
4228 /// statement and the return type has been left as default or has been specified as `()`. If so,
4229 /// it suggests adding a semicolon.
4230 fn suggest_missing_semicolon(
4232 err: &mut DiagnosticBuilder<'tcx>,
4233 expression: &'tcx hir::Expr,
4237 if expected.is_unit() {
4238 // `BlockTailExpression` only relevant if the tail expr would be
4239 // useful on its own.
4240 match expression.node {
4241 ExprKind::Call(..) |
4242 ExprKind::MethodCall(..) |
4243 ExprKind::Loop(..) |
4244 ExprKind::Match(..) |
4245 ExprKind::Block(..) => {
4246 let sp = self.tcx.sess.source_map().next_point(cause_span);
4247 err.span_suggestion(
4249 "try adding a semicolon",
4251 Applicability::MachineApplicable);
4258 /// A possible error is to forget to add a return type that is needed:
4262 /// bar_that_returns_u32()
4266 /// This routine checks if the return type is left as default, the method is not part of an
4267 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4269 fn suggest_missing_return_type(
4271 err: &mut DiagnosticBuilder<'tcx>,
4272 fn_decl: &hir::FnDecl,
4277 // Only suggest changing the return type for methods that
4278 // haven't set a return type at all (and aren't `fn main()` or an impl).
4279 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4280 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4281 err.span_suggestion(
4283 "try adding a return type",
4284 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
4285 Applicability::MachineApplicable);
4288 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4289 err.span_label(span, "possibly return type missing here?");
4292 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4293 // `fn main()` must return `()`, do not suggest changing return type
4294 err.span_label(span, "expected `()` because of default return type");
4297 // expectation was caused by something else, not the default return
4298 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4299 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4300 // Only point to return type if the expected type is the return type, as if they
4301 // are not, the expectation must have been caused by something else.
4302 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.node);
4304 let ty = AstConv::ast_ty_to_ty(self, ty);
4305 debug!("suggest_missing_return_type: return type {:?}", ty);
4306 debug!("suggest_missing_return_type: expected type {:?}", ty);
4307 if ty.sty == expected.sty {
4308 err.span_label(sp, format!("expected `{}` because of return type",
4317 /// A possible error is to forget to add `.await` when using futures:
4320 /// async fn make_u32() -> u32 {
4324 /// fn take_u32(x: u32) {}
4326 /// async fn foo() {
4327 /// let x = make_u32();
4332 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4333 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4334 /// `.await` to the tail of the expression.
4335 fn suggest_missing_await(
4337 err: &mut DiagnosticBuilder<'tcx>,
4342 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4343 // body isn't `async`.
4344 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4345 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4346 let body = self.tcx().hir().body(body_id);
4347 if let Some(hir::GeneratorKind::Async) = body.generator_kind {
4349 // Check for `Future` implementations by constructing a predicate to
4350 // prove: `<T as Future>::Output == U`
4351 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4352 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4353 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4354 // `<T as Future>::Output`
4355 projection_ty: ty::ProjectionTy {
4357 substs: self.tcx.mk_substs_trait(
4359 self.fresh_substs_for_item(sp, item_def_id)
4366 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4367 if self.infcx.predicate_may_hold(&obligation) {
4368 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4369 err.span_suggestion(
4371 "consider using `.await` here",
4372 format!("{}.await", code),
4373 Applicability::MaybeIncorrect,
4381 /// A common error is to add an extra semicolon:
4384 /// fn foo() -> usize {
4389 /// This routine checks if the final statement in a block is an
4390 /// expression with an explicit semicolon whose type is compatible
4391 /// with `expected_ty`. If so, it suggests removing the semicolon.
4392 fn consider_hint_about_removing_semicolon(
4394 blk: &'tcx hir::Block,
4395 expected_ty: Ty<'tcx>,
4396 err: &mut DiagnosticBuilder<'_>,
4398 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4399 err.span_suggestion(
4401 "consider removing this semicolon",
4403 Applicability::MachineApplicable,
4408 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4409 // Be helpful when the user wrote `{... expr;}` and
4410 // taking the `;` off is enough to fix the error.
4411 let last_stmt = blk.stmts.last()?;
4412 let last_expr = match last_stmt.node {
4413 hir::StmtKind::Semi(ref e) => e,
4416 let last_expr_ty = self.node_ty(last_expr.hir_id);
4417 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4420 let original_span = original_sp(last_stmt.span, blk.span);
4421 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4424 // Instantiates the given path, which must refer to an item with the given
4425 // number of type parameters and type.
4426 pub fn instantiate_value_path(&self,
4427 segments: &[hir::PathSegment],
4428 self_ty: Option<Ty<'tcx>>,
4432 -> (Ty<'tcx>, Res) {
4434 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4443 let path_segs = match res {
4444 Res::Local(_) | Res::SelfCtor(_) => vec![],
4445 Res::Def(kind, def_id) =>
4446 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4447 _ => bug!("instantiate_value_path on {:?}", res),
4450 let mut user_self_ty = None;
4451 let mut is_alias_variant_ctor = false;
4453 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4454 if let Some(self_ty) = self_ty {
4455 let adt_def = self_ty.ty_adt_def().unwrap();
4456 user_self_ty = Some(UserSelfTy {
4457 impl_def_id: adt_def.did,
4460 is_alias_variant_ctor = true;
4463 Res::Def(DefKind::Method, def_id)
4464 | Res::Def(DefKind::AssocConst, def_id) => {
4465 let container = tcx.associated_item(def_id).container;
4466 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4468 ty::TraitContainer(trait_did) => {
4469 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4471 ty::ImplContainer(impl_def_id) => {
4472 if segments.len() == 1 {
4473 // `<T>::assoc` will end up here, and so
4474 // can `T::assoc`. It this came from an
4475 // inherent impl, we need to record the
4476 // `T` for posterity (see `UserSelfTy` for
4478 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4479 user_self_ty = Some(UserSelfTy {
4490 // Now that we have categorized what space the parameters for each
4491 // segment belong to, let's sort out the parameters that the user
4492 // provided (if any) into their appropriate spaces. We'll also report
4493 // errors if type parameters are provided in an inappropriate place.
4495 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4496 let generics_has_err = AstConv::prohibit_generics(
4497 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4498 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4505 if let Res::Local(hid) = res {
4506 let ty = self.local_ty(span, hid).decl_ty;
4507 let ty = self.normalize_associated_types_in(span, &ty);
4508 self.write_ty(hir_id, ty);
4512 if generics_has_err {
4513 // Don't try to infer type parameters when prohibited generic arguments were given.
4514 user_self_ty = None;
4517 // Now we have to compare the types that the user *actually*
4518 // provided against the types that were *expected*. If the user
4519 // did not provide any types, then we want to substitute inference
4520 // variables. If the user provided some types, we may still need
4521 // to add defaults. If the user provided *too many* types, that's
4524 let mut infer_args_for_err = FxHashSet::default();
4525 for &PathSeg(def_id, index) in &path_segs {
4526 let seg = &segments[index];
4527 let generics = tcx.generics_of(def_id);
4528 // Argument-position `impl Trait` is treated as a normal generic
4529 // parameter internally, but we don't allow users to specify the
4530 // parameter's value explicitly, so we have to do some error-
4532 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4537 false, // `is_method_call`
4539 if suppress_errors {
4540 infer_args_for_err.insert(index);
4541 self.set_tainted_by_errors(); // See issue #53251.
4545 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4546 tcx.generics_of(*def_id).has_self
4547 }).unwrap_or(false);
4549 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4550 let ty = self.impl_self_ty(span, impl_def_id).ty;
4551 let adt_def = ty.ty_adt_def();
4554 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4555 let variant = adt_def.non_enum_variant();
4556 let ctor_def_id = variant.ctor_def_id.unwrap();
4558 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4563 let mut err = tcx.sess.struct_span_err(span,
4564 "the `Self` constructor can only be used with tuple or unit structs");
4565 if let Some(adt_def) = adt_def {
4566 match adt_def.adt_kind() {
4568 err.help("did you mean to use one of the enum's variants?");
4572 err.span_suggestion(
4574 "use curly brackets",
4575 String::from("Self { /* fields */ }"),
4576 Applicability::HasPlaceholders,
4583 return (tcx.types.err, res)
4589 let def_id = res.def_id();
4591 // The things we are substituting into the type should not contain
4592 // escaping late-bound regions, and nor should the base type scheme.
4593 let ty = tcx.type_of(def_id);
4595 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4601 // Provide the generic args, and whether types should be inferred.
4603 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4606 // If we've encountered an `impl Trait`-related error, we're just
4607 // going to infer the arguments for better error messages.
4608 if !infer_args_for_err.contains(&index) {
4609 // Check whether the user has provided generic arguments.
4610 if let Some(ref data) = segments[index].args {
4611 return (Some(data), segments[index].infer_args);
4614 return (None, segments[index].infer_args);
4619 // Provide substitutions for parameters for which (valid) arguments have been provided.
4621 match (¶m.kind, arg) {
4622 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4623 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4625 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4626 self.to_ty(ty).into()
4628 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4629 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4631 _ => unreachable!(),
4634 // Provide substitutions for parameters for which arguments are inferred.
4635 |substs, param, infer_args| {
4637 GenericParamDefKind::Lifetime => {
4638 self.re_infer(Some(param), span).unwrap().into()
4640 GenericParamDefKind::Type { has_default, .. } => {
4641 if !infer_args && has_default {
4642 // If we have a default, then we it doesn't matter that we're not
4643 // inferring the type arguments: we provide the default where any
4645 let default = tcx.type_of(param.def_id);
4648 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4651 // If no type arguments were provided, we have to infer them.
4652 // This case also occurs as a result of some malformed input, e.g.
4653 // a lifetime argument being given instead of a type parameter.
4654 // Using inference instead of `Error` gives better error messages.
4655 self.var_for_def(span, param)
4658 GenericParamDefKind::Const => {
4659 // FIXME(const_generics:defaults)
4660 // No const parameters were provided, we have to infer them.
4661 self.var_for_def(span, param)
4666 assert!(!substs.has_escaping_bound_vars());
4667 assert!(!ty.has_escaping_bound_vars());
4669 // First, store the "user substs" for later.
4670 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4672 // Add all the obligations that are required, substituting and
4673 // normalized appropriately.
4674 let bounds = self.instantiate_bounds(span, def_id, &substs);
4675 self.add_obligations_for_parameters(
4676 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
4679 // Substitute the values for the type parameters into the type of
4680 // the referenced item.
4681 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4683 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4684 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4685 // is inherent, there is no `Self` parameter; instead, the impl needs
4686 // type parameters, which we can infer by unifying the provided `Self`
4687 // with the substituted impl type.
4688 // This also occurs for an enum variant on a type alias.
4689 let ty = tcx.type_of(impl_def_id);
4691 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4692 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4693 Ok(ok) => self.register_infer_ok_obligations(ok),
4695 self.tcx.sess.delay_span_bug(span, &format!(
4696 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4704 self.check_rustc_args_require_const(def_id, hir_id, span);
4706 debug!("instantiate_value_path: type of {:?} is {:?}",
4709 self.write_substs(hir_id, substs);
4711 (ty_substituted, res)
4714 fn check_rustc_args_require_const(&self,
4718 // We're only interested in functions tagged with
4719 // #[rustc_args_required_const], so ignore anything that's not.
4720 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
4724 // If our calling expression is indeed the function itself, we're good!
4725 // If not, generate an error that this can only be called directly.
4726 if let Node::Expr(expr) = self.tcx.hir().get(
4727 self.tcx.hir().get_parent_node(hir_id))
4729 if let ExprKind::Call(ref callee, ..) = expr.node {
4730 if callee.hir_id == hir_id {
4736 self.tcx.sess.span_err(span, "this function can only be invoked \
4737 directly, not through a function pointer");
4740 // Resolves `typ` by a single level if `typ` is a type variable.
4741 // If no resolution is possible, then an error is reported.
4742 // Numeric inference variables may be left unresolved.
4743 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4744 let ty = self.resolve_type_vars_with_obligations(ty);
4745 if !ty.is_ty_var() {
4748 if !self.is_tainted_by_errors() {
4749 self.need_type_info_err((**self).body_id, sp, ty)
4750 .note("type must be known at this point")
4753 self.demand_suptype(sp, self.tcx.types.err, ty);
4758 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
4761 ctxt: BreakableCtxt<'tcx>,
4763 ) -> (BreakableCtxt<'tcx>, R) {
4766 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4767 index = enclosing_breakables.stack.len();
4768 enclosing_breakables.by_id.insert(id, index);
4769 enclosing_breakables.stack.push(ctxt);
4773 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4774 debug_assert!(enclosing_breakables.stack.len() == index + 1);
4775 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
4776 enclosing_breakables.stack.pop().expect("missing breakable context")
4781 /// Instantiate a QueryResponse in a probe context, without a
4782 /// good ObligationCause.
4783 fn probe_instantiate_query_response(
4786 original_values: &OriginalQueryValues<'tcx>,
4787 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
4788 ) -> InferResult<'tcx, Ty<'tcx>>
4790 self.instantiate_query_response_and_region_obligations(
4791 &traits::ObligationCause::misc(span, self.body_id),
4797 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
4798 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
4799 let mut contained_in_place = false;
4801 while let hir::Node::Expr(parent_expr) =
4802 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
4804 match &parent_expr.node {
4805 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
4806 if lhs.hir_id == expr_id {
4807 contained_in_place = true;
4813 expr_id = parent_expr.hir_id;
4820 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
4821 let own_counts = generics.own_counts();
4823 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
4829 if own_counts.types == 0 {
4833 // Make a vector of booleans initially `false`; set to `true` when used.
4834 let mut types_used = vec![false; own_counts.types];
4836 for leaf_ty in ty.walk() {
4837 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.sty {
4838 debug!("found use of ty param num {}", index);
4839 types_used[index as usize - own_counts.lifetimes] = true;
4840 } else if let ty::Error = leaf_ty.sty {
4841 // If there is already another error, do not emit
4842 // an error for not using a type parameter.
4843 assert!(tcx.sess.has_errors());
4848 let types = generics.params.iter().filter(|param| match param.kind {
4849 ty::GenericParamDefKind::Type { .. } => true,
4852 for (&used, param) in types_used.iter().zip(types) {
4854 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
4855 let span = tcx.hir().span(id);
4856 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
4857 .span_label(span, "unused type parameter")
4863 fn fatally_break_rust(sess: &Session) {
4864 let handler = sess.diagnostic();
4865 handler.span_bug_no_panic(
4867 "It looks like you're trying to break rust; would you like some ICE?",
4869 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
4870 handler.note_without_error(
4871 "we would appreciate a joke overview: \
4872 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
4874 handler.note_without_error(&format!("rustc {} running on {}",
4875 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
4876 crate::session::config::host_triple(),
4880 fn potentially_plural_count(count: usize, word: &str) -> String {
4881 format!("{} {}{}", count, word, if count == 1 { "" } else { "s" })