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, pluralise};
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, Debug)]
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 !span.is_desugaring(DesugaringKind::Async)
2346 self.diverges.set(Diverges::WarnedAlways);
2348 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2350 let msg = format!("unreachable {}", kind);
2351 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2352 .span_label(span, &msg)
2355 custom_note.unwrap_or("any code following this expression is unreachable"),
2364 code: ObligationCauseCode<'tcx>)
2365 -> ObligationCause<'tcx> {
2366 ObligationCause::new(span, self.body_id, code)
2369 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2370 self.cause(span, ObligationCauseCode::MiscObligation)
2373 /// Resolves type variables in `ty` if possible. Unlike the infcx
2374 /// version (resolve_vars_if_possible), this version will
2375 /// also select obligations if it seems useful, in an effort
2376 /// to get more type information.
2377 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2378 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2380 // No Infer()? Nothing needs doing.
2381 if !ty.has_infer_types() {
2382 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2386 // If `ty` is a type variable, see whether we already know what it is.
2387 ty = self.resolve_vars_if_possible(&ty);
2388 if !ty.has_infer_types() {
2389 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2393 // If not, try resolving pending obligations as much as
2394 // possible. This can help substantially when there are
2395 // indirect dependencies that don't seem worth tracking
2397 self.select_obligations_where_possible(false, |_| {});
2398 ty = self.resolve_vars_if_possible(&ty);
2400 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2404 fn record_deferred_call_resolution(
2406 closure_def_id: DefId,
2407 r: DeferredCallResolution<'tcx>,
2409 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2410 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2413 fn remove_deferred_call_resolutions(
2415 closure_def_id: DefId,
2416 ) -> Vec<DeferredCallResolution<'tcx>> {
2417 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2418 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2421 pub fn tag(&self) -> String {
2422 format!("{:p}", self)
2425 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2426 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2427 span_bug!(span, "no type for local variable {}",
2428 self.tcx.hir().node_to_string(nid))
2433 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2434 debug!("write_ty({:?}, {:?}) in fcx {}",
2435 id, self.resolve_vars_if_possible(&ty), self.tag());
2436 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2438 if ty.references_error() {
2439 self.has_errors.set(true);
2440 self.set_tainted_by_errors();
2444 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2445 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2448 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2449 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2452 pub fn write_method_call(&self,
2454 method: MethodCallee<'tcx>) {
2455 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2456 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2457 self.write_substs(hir_id, method.substs);
2459 // When the method is confirmed, the `method.substs` includes
2460 // parameters from not just the method, but also the impl of
2461 // the method -- in particular, the `Self` type will be fully
2462 // resolved. However, those are not something that the "user
2463 // specified" -- i.e., those types come from the inferred type
2464 // of the receiver, not something the user wrote. So when we
2465 // create the user-substs, we want to replace those earlier
2466 // types with just the types that the user actually wrote --
2467 // that is, those that appear on the *method itself*.
2469 // As an example, if the user wrote something like
2470 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2471 // type of `foo` (possibly adjusted), but we don't want to
2472 // include that. We want just the `[_, u32]` part.
2473 if !method.substs.is_noop() {
2474 let method_generics = self.tcx.generics_of(method.def_id);
2475 if !method_generics.params.is_empty() {
2476 let user_type_annotation = self.infcx.probe(|_| {
2477 let user_substs = UserSubsts {
2478 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2479 let i = param.index as usize;
2480 if i < method_generics.parent_count {
2481 self.infcx.var_for_def(DUMMY_SP, param)
2486 user_self_ty: None, // not relevant here
2489 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2495 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2496 self.write_user_type_annotation(hir_id, user_type_annotation);
2501 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2502 if !substs.is_noop() {
2503 debug!("write_substs({:?}, {:?}) in fcx {}",
2508 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2512 /// Given the substs that we just converted from the HIR, try to
2513 /// canonicalize them and store them as user-given substitutions
2514 /// (i.e., substitutions that must be respected by the NLL check).
2516 /// This should be invoked **before any unifications have
2517 /// occurred**, so that annotations like `Vec<_>` are preserved
2519 pub fn write_user_type_annotation_from_substs(
2523 substs: SubstsRef<'tcx>,
2524 user_self_ty: Option<UserSelfTy<'tcx>>,
2527 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2528 user_self_ty={:?} in fcx {}",
2529 hir_id, def_id, substs, user_self_ty, self.tag(),
2532 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2533 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2534 &UserType::TypeOf(def_id, UserSubsts {
2539 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2540 self.write_user_type_annotation(hir_id, canonicalized);
2544 pub fn write_user_type_annotation(
2547 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2550 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2551 hir_id, canonical_user_type_annotation, self.tag(),
2554 if !canonical_user_type_annotation.is_identity() {
2555 self.tables.borrow_mut().user_provided_types_mut().insert(
2556 hir_id, canonical_user_type_annotation
2559 debug!("write_user_type_annotation: skipping identity substs");
2563 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2564 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2570 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2571 Entry::Vacant(entry) => { entry.insert(adj); },
2572 Entry::Occupied(mut entry) => {
2573 debug!(" - composing on top of {:?}", entry.get());
2574 match (&entry.get()[..], &adj[..]) {
2575 // Applying any adjustment on top of a NeverToAny
2576 // is a valid NeverToAny adjustment, because it can't
2578 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2580 Adjustment { kind: Adjust::Deref(_), .. },
2581 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2583 Adjustment { kind: Adjust::Deref(_), .. },
2584 .. // Any following adjustments are allowed.
2586 // A reborrow has no effect before a dereference.
2588 // FIXME: currently we never try to compose autoderefs
2589 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2591 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2592 expr, entry.get(), adj)
2594 *entry.get_mut() = adj;
2599 /// Basically whenever we are converting from a type scheme into
2600 /// the fn body space, we always want to normalize associated
2601 /// types as well. This function combines the two.
2602 fn instantiate_type_scheme<T>(&self,
2604 substs: SubstsRef<'tcx>,
2607 where T : TypeFoldable<'tcx>
2609 let value = value.subst(self.tcx, substs);
2610 let result = self.normalize_associated_types_in(span, &value);
2611 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2618 /// As `instantiate_type_scheme`, but for the bounds found in a
2619 /// generic type scheme.
2620 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: SubstsRef<'tcx>)
2621 -> ty::InstantiatedPredicates<'tcx> {
2622 let bounds = self.tcx.predicates_of(def_id);
2623 let result = bounds.instantiate(self.tcx, substs);
2624 let result = self.normalize_associated_types_in(span, &result);
2625 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
2632 /// Replaces the opaque types from the given value with type variables,
2633 /// and records the `OpaqueTypeMap` for later use during writeback. See
2634 /// `InferCtxt::instantiate_opaque_types` for more details.
2635 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2637 parent_id: hir::HirId,
2641 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2642 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2646 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2647 self.instantiate_opaque_types(
2656 let mut opaque_types = self.opaque_types.borrow_mut();
2657 for (ty, decl) in opaque_type_map {
2658 let old_value = opaque_types.insert(ty, decl);
2659 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2665 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2666 where T : TypeFoldable<'tcx>
2668 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2671 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2673 where T : TypeFoldable<'tcx>
2675 self.inh.partially_normalize_associated_types_in(span,
2681 pub fn require_type_meets(&self,
2684 code: traits::ObligationCauseCode<'tcx>,
2687 self.register_bound(
2690 traits::ObligationCause::new(span, self.body_id, code));
2693 pub fn require_type_is_sized(&self,
2696 code: traits::ObligationCauseCode<'tcx>)
2698 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2699 self.require_type_meets(ty, span, code, lang_item);
2702 pub fn require_type_is_sized_deferred(&self,
2705 code: traits::ObligationCauseCode<'tcx>)
2707 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2710 pub fn register_bound(&self,
2713 cause: traits::ObligationCause<'tcx>)
2715 self.fulfillment_cx.borrow_mut()
2716 .register_bound(self, self.param_env, ty, def_id, cause);
2719 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2720 let t = AstConv::ast_ty_to_ty(self, ast_t);
2721 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2725 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2726 let ty = self.to_ty(ast_ty);
2727 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2729 if Self::can_contain_user_lifetime_bounds(ty) {
2730 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2731 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2732 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2738 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2739 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2740 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2743 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2744 AstConv::ast_const_to_const(self, ast_c, ty)
2747 // If the type given by the user has free regions, save it for later, since
2748 // NLL would like to enforce those. Also pass in types that involve
2749 // projections, since those can resolve to `'static` bounds (modulo #54940,
2750 // which hopefully will be fixed by the time you see this comment, dear
2751 // reader, although I have my doubts). Also pass in types with inference
2752 // types, because they may be repeated. Other sorts of things are already
2753 // sufficiently enforced with erased regions. =)
2754 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2756 T: TypeFoldable<'tcx>
2758 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2761 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2762 match self.tables.borrow().node_types().get(id) {
2764 None if self.is_tainted_by_errors() => self.tcx.types.err,
2766 bug!("no type for node {}: {} in fcx {}",
2767 id, self.tcx.hir().node_to_string(id),
2773 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2774 /// outlive the region `r`.
2775 pub fn register_wf_obligation(&self,
2778 code: traits::ObligationCauseCode<'tcx>)
2780 // WF obligations never themselves fail, so no real need to give a detailed cause:
2781 let cause = traits::ObligationCause::new(span, self.body_id, code);
2782 self.register_predicate(traits::Obligation::new(cause,
2784 ty::Predicate::WellFormed(ty)));
2787 /// Registers obligations that all types appearing in `substs` are well-formed.
2788 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2789 for ty in substs.types() {
2790 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2794 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2795 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2796 /// trait/region obligations.
2798 /// For example, if there is a function:
2801 /// fn foo<'a,T:'a>(...)
2804 /// and a reference:
2810 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2811 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2812 pub fn add_obligations_for_parameters(&self,
2813 cause: traits::ObligationCause<'tcx>,
2814 predicates: &ty::InstantiatedPredicates<'tcx>)
2816 assert!(!predicates.has_escaping_bound_vars());
2818 debug!("add_obligations_for_parameters(predicates={:?})",
2821 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2822 self.register_predicate(obligation);
2826 // FIXME(arielb1): use this instead of field.ty everywhere
2827 // Only for fields! Returns <none> for methods>
2828 // Indifferent to privacy flags
2829 pub fn field_ty(&self,
2831 field: &'tcx ty::FieldDef,
2832 substs: SubstsRef<'tcx>)
2835 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2838 fn check_casts(&self) {
2839 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2840 for cast in deferred_cast_checks.drain(..) {
2845 fn resolve_generator_interiors(&self, def_id: DefId) {
2846 let mut generators = self.deferred_generator_interiors.borrow_mut();
2847 for (body_id, interior, kind) in generators.drain(..) {
2848 self.select_obligations_where_possible(false, |_| {});
2849 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2853 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2854 // Non-numerics get replaced with ! or () (depending on whether
2855 // feature(never_type) is enabled, unconstrained ints with i32,
2856 // unconstrained floats with f64.
2857 // Fallback becomes very dubious if we have encountered type-checking errors.
2858 // In that case, fallback to Error.
2859 // The return value indicates whether fallback has occurred.
2860 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2861 use rustc::ty::error::UnconstrainedNumeric::Neither;
2862 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2864 assert!(ty.is_ty_infer());
2865 let fallback = match self.type_is_unconstrained_numeric(ty) {
2866 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2867 UnconstrainedInt => self.tcx.types.i32,
2868 UnconstrainedFloat => self.tcx.types.f64,
2869 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2870 Neither => return false,
2872 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2873 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2877 fn select_all_obligations_or_error(&self) {
2878 debug!("select_all_obligations_or_error");
2879 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2880 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2884 /// Select as many obligations as we can at present.
2885 fn select_obligations_where_possible(
2887 fallback_has_occurred: bool,
2888 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
2890 if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2891 mutate_fullfillment_errors(&mut errors);
2892 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2896 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2897 /// returns a type of `&T`, but the actual type we assign to the
2898 /// *expression* is `T`. So this function just peels off the return
2899 /// type by one layer to yield `T`.
2900 fn make_overloaded_place_return_type(&self,
2901 method: MethodCallee<'tcx>)
2902 -> ty::TypeAndMut<'tcx>
2904 // extract method return type, which will be &T;
2905 let ret_ty = method.sig.output();
2907 // method returns &T, but the type as visible to user is T, so deref
2908 ret_ty.builtin_deref(true).unwrap()
2914 base_expr: &'tcx hir::Expr,
2918 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2919 // FIXME(#18741) -- this is almost but not quite the same as the
2920 // autoderef that normal method probing does. They could likely be
2923 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2924 let mut result = None;
2925 while result.is_none() && autoderef.next().is_some() {
2926 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2928 autoderef.finalize(self);
2932 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2933 /// (and otherwise adjust) `base_expr`, looking for a type which either
2934 /// supports builtin indexing or overloaded indexing.
2935 /// This loop implements one step in that search; the autoderef loop
2936 /// is implemented by `lookup_indexing`.
2940 base_expr: &hir::Expr,
2941 autoderef: &Autoderef<'a, 'tcx>,
2944 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2945 let adjusted_ty = autoderef.unambiguous_final_ty(self);
2946 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2953 for &unsize in &[false, true] {
2954 let mut self_ty = adjusted_ty;
2956 // We only unsize arrays here.
2957 if let ty::Array(element_ty, _) = adjusted_ty.sty {
2958 self_ty = self.tcx.mk_slice(element_ty);
2964 // If some lookup succeeds, write callee into table and extract index/element
2965 // type from the method signature.
2966 // If some lookup succeeded, install method in table
2967 let input_ty = self.next_ty_var(TypeVariableOrigin {
2968 kind: TypeVariableOriginKind::AutoDeref,
2969 span: base_expr.span,
2971 let method = self.try_overloaded_place_op(
2972 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
2974 let result = method.map(|ok| {
2975 debug!("try_index_step: success, using overloaded indexing");
2976 let method = self.register_infer_ok_obligations(ok);
2978 let mut adjustments = autoderef.adjust_steps(self, needs);
2979 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].sty {
2980 let mutbl = match r_mutbl {
2981 hir::MutImmutable => AutoBorrowMutability::Immutable,
2982 hir::MutMutable => AutoBorrowMutability::Mutable {
2983 // Indexing can be desugared to a method call,
2984 // so maybe we could use two-phase here.
2985 // See the documentation of AllowTwoPhase for why that's
2986 // not the case today.
2987 allow_two_phase_borrow: AllowTwoPhase::No,
2990 adjustments.push(Adjustment {
2991 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
2992 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2999 adjustments.push(Adjustment {
3000 kind: Adjust::Pointer(PointerCast::Unsize),
3001 target: method.sig.inputs()[0]
3004 self.apply_adjustments(base_expr, adjustments);
3006 self.write_method_call(expr.hir_id, method);
3007 (input_ty, self.make_overloaded_place_return_type(method).ty)
3009 if result.is_some() {
3017 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3018 let (tr, name) = match (op, is_mut) {
3019 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3020 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3021 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3022 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3024 (tr, ast::Ident::with_dummy_span(name))
3027 fn try_overloaded_place_op(&self,
3030 arg_tys: &[Ty<'tcx>],
3033 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3035 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3041 // Try Mut first, if needed.
3042 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3043 let method = match (needs, mut_tr) {
3044 (Needs::MutPlace, Some(trait_did)) => {
3045 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3050 // Otherwise, fall back to the immutable version.
3051 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3052 let method = match (method, imm_tr) {
3053 (None, Some(trait_did)) => {
3054 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3056 (method, _) => method,
3062 fn check_method_argument_types(
3066 method: Result<MethodCallee<'tcx>, ()>,
3067 args_no_rcvr: &'tcx [hir::Expr],
3068 tuple_arguments: TupleArgumentsFlag,
3069 expected: Expectation<'tcx>,
3071 let has_error = match method {
3073 method.substs.references_error() || method.sig.references_error()
3078 let err_inputs = self.err_args(args_no_rcvr.len());
3080 let err_inputs = match tuple_arguments {
3081 DontTupleArguments => err_inputs,
3082 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3085 self.check_argument_types(sp, expr_sp, &err_inputs[..], &[], args_no_rcvr,
3086 false, tuple_arguments, None);
3087 return self.tcx.types.err;
3090 let method = method.unwrap();
3091 // HACK(eddyb) ignore self in the definition (see above).
3092 let expected_arg_tys = self.expected_inputs_for_expected_output(
3095 method.sig.output(),
3096 &method.sig.inputs()[1..]
3098 self.check_argument_types(sp, expr_sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
3099 args_no_rcvr, method.sig.c_variadic, tuple_arguments,
3100 self.tcx.hir().span_if_local(method.def_id));
3104 fn self_type_matches_expected_vid(
3106 trait_ref: ty::PolyTraitRef<'tcx>,
3107 expected_vid: ty::TyVid,
3109 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3111 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3112 trait_ref, self_ty, expected_vid
3115 ty::Infer(ty::TyVar(found_vid)) => {
3116 // FIXME: consider using `sub_root_var` here so we
3117 // can see through subtyping.
3118 let found_vid = self.root_var(found_vid);
3119 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3120 expected_vid == found_vid
3126 fn obligations_for_self_ty<'b>(
3129 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3132 // FIXME: consider using `sub_root_var` here so we
3133 // can see through subtyping.
3134 let ty_var_root = self.root_var(self_ty);
3135 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3136 self_ty, ty_var_root,
3137 self.fulfillment_cx.borrow().pending_obligations());
3141 .pending_obligations()
3143 .filter_map(move |obligation| match obligation.predicate {
3144 ty::Predicate::Projection(ref data) =>
3145 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3146 ty::Predicate::Trait(ref data) =>
3147 Some((data.to_poly_trait_ref(), obligation)),
3148 ty::Predicate::Subtype(..) => None,
3149 ty::Predicate::RegionOutlives(..) => None,
3150 ty::Predicate::TypeOutlives(..) => None,
3151 ty::Predicate::WellFormed(..) => None,
3152 ty::Predicate::ObjectSafe(..) => None,
3153 ty::Predicate::ConstEvaluatable(..) => None,
3154 // N.B., this predicate is created by breaking down a
3155 // `ClosureType: FnFoo()` predicate, where
3156 // `ClosureType` represents some `Closure`. It can't
3157 // possibly be referring to the current closure,
3158 // because we haven't produced the `Closure` for
3159 // this closure yet; this is exactly why the other
3160 // code is looking for a self type of a unresolved
3161 // inference variable.
3162 ty::Predicate::ClosureKind(..) => None,
3163 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3166 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3167 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3168 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3172 /// Generic function that factors out common logic from function calls,
3173 /// method calls and overloaded operators.
3174 fn check_argument_types(
3178 fn_inputs: &[Ty<'tcx>],
3179 expected_arg_tys: &[Ty<'tcx>],
3180 args: &'tcx [hir::Expr],
3182 tuple_arguments: TupleArgumentsFlag,
3183 def_span: Option<Span>,
3187 // Grab the argument types, supplying fresh type variables
3188 // if the wrong number of arguments were supplied
3189 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3195 // All the input types from the fn signature must outlive the call
3196 // so as to validate implied bounds.
3197 for &fn_input_ty in fn_inputs {
3198 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
3201 let expected_arg_count = fn_inputs.len();
3203 let param_count_error = |expected_count: usize,
3208 let mut err = tcx.sess.struct_span_err_with_code(sp,
3209 &format!("this function takes {}{} but {} {} supplied",
3210 if c_variadic { "at least " } else { "" },
3211 potentially_plural_count(expected_count, "parameter"),
3212 potentially_plural_count(arg_count, "parameter"),
3213 if arg_count == 1 {"was"} else {"were"}),
3214 DiagnosticId::Error(error_code.to_owned()));
3216 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3217 err.span_label(def_s, "defined here");
3220 let sugg_span = tcx.sess.source_map().end_point(expr_sp);
3221 // remove closing `)` from the span
3222 let sugg_span = sugg_span.shrink_to_lo();
3223 err.span_suggestion(
3225 "expected the unit value `()`; create it with empty parentheses",
3227 Applicability::MachineApplicable);
3229 err.span_label(sp, format!("expected {}{}",
3230 if c_variadic { "at least " } else { "" },
3231 potentially_plural_count(expected_count, "parameter")));
3236 let mut expected_arg_tys = expected_arg_tys.to_vec();
3238 let formal_tys = if tuple_arguments == TupleArguments {
3239 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3240 match tuple_type.sty {
3241 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3242 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3243 expected_arg_tys = vec![];
3244 self.err_args(args.len())
3246 ty::Tuple(arg_types) => {
3247 expected_arg_tys = match expected_arg_tys.get(0) {
3248 Some(&ty) => match ty.sty {
3249 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3254 arg_types.iter().map(|k| k.expect_ty()).collect()
3257 span_err!(tcx.sess, sp, E0059,
3258 "cannot use call notation; the first type parameter \
3259 for the function trait is neither a tuple nor unit");
3260 expected_arg_tys = vec![];
3261 self.err_args(args.len())
3264 } else if expected_arg_count == supplied_arg_count {
3266 } else if c_variadic {
3267 if supplied_arg_count >= expected_arg_count {
3270 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3271 expected_arg_tys = vec![];
3272 self.err_args(supplied_arg_count)
3275 // is the missing argument of type `()`?
3276 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3277 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3278 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3279 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3283 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3285 expected_arg_tys = vec![];
3286 self.err_args(supplied_arg_count)
3289 debug!("check_argument_types: formal_tys={:?}",
3290 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3292 // If there is no expectation, expect formal_tys.
3293 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3299 let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
3301 // Check the arguments.
3302 // We do this in a pretty awful way: first we type-check any arguments
3303 // that are not closures, then we type-check the closures. This is so
3304 // that we have more information about the types of arguments when we
3305 // type-check the functions. This isn't really the right way to do this.
3306 for &check_closures in &[false, true] {
3307 debug!("check_closures={}", check_closures);
3309 // More awful hacks: before we check argument types, try to do
3310 // an "opportunistic" vtable resolution of any trait bounds on
3311 // the call. This helps coercions.
3313 self.select_obligations_where_possible(false, |errors| {
3314 self.point_at_arg_instead_of_call_if_possible(
3316 &final_arg_types[..],
3323 // For C-variadic functions, we don't have a declared type for all of
3324 // the arguments hence we only do our usual type checking with
3325 // the arguments who's types we do know.
3326 let t = if c_variadic {
3328 } else if tuple_arguments == TupleArguments {
3333 for (i, arg) in args.iter().take(t).enumerate() {
3334 // Warn only for the first loop (the "no closures" one).
3335 // Closure arguments themselves can't be diverging, but
3336 // a previous argument can, e.g., `foo(panic!(), || {})`.
3337 if !check_closures {
3338 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3341 let is_closure = match arg.node {
3342 ExprKind::Closure(..) => true,
3346 if is_closure != check_closures {
3350 debug!("checking the argument");
3351 let formal_ty = formal_tys[i];
3353 // The special-cased logic below has three functions:
3354 // 1. Provide as good of an expected type as possible.
3355 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3357 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3359 // 2. Coerce to the most detailed type that could be coerced
3360 // to, which is `expected_ty` if `rvalue_hint` returns an
3361 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3362 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3363 // We're processing function arguments so we definitely want to use
3364 // two-phase borrows.
3365 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3366 final_arg_types.push((i, coerce_ty));
3368 // 3. Relate the expected type and the formal one,
3369 // if the expected type was used for the coercion.
3370 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3374 // We also need to make sure we at least write the ty of the other
3375 // arguments which we skipped above.
3377 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3378 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3379 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3382 for arg in args.iter().skip(expected_arg_count) {
3383 let arg_ty = self.check_expr(&arg);
3385 // There are a few types which get autopromoted when passed via varargs
3386 // in C but we just error out instead and require explicit casts.
3387 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3389 ty::Float(ast::FloatTy::F32) => {
3390 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3392 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3393 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3395 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3396 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3399 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3400 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3401 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3409 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3410 vec![self.tcx.types.err; len]
3413 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
3414 /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
3415 /// reference a type argument. If they do, and there's only *one* argument that does, we point
3416 /// at the corresponding argument's expression span instead of the `fn` call path span.
3417 fn point_at_arg_instead_of_call_if_possible(
3419 errors: &mut Vec<traits::FulfillmentError<'_>>,
3420 final_arg_types: &[(usize, Ty<'tcx>)],
3422 args: &'tcx [hir::Expr],
3424 if !call_sp.desugaring_kind().is_some() {
3425 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3426 // the `?` operator.
3427 for error in errors {
3428 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3429 // Collect the argument position for all arguments that could have caused this
3430 // `FullfillmentError`.
3431 let mut referenced_in = final_arg_types.iter()
3432 .flat_map(|(i, ty)| {
3433 let ty = self.resolve_vars_if_possible(ty);
3434 // We walk the argument type because the argument's type could have
3435 // been `Option<T>`, but the `FullfillmentError` references `T`.
3437 .filter(|&ty| ty == predicate.skip_binder().self_ty())
3440 if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
3441 // We make sure that only *one* argument matches the obligation failure
3442 // and thet the obligation's span to its expression's.
3443 error.obligation.cause.span = args[ref_in].span;
3444 error.points_at_arg_span = true;
3451 // AST fragment checking
3454 expected: Expectation<'tcx>)
3460 ast::LitKind::Str(..) => tcx.mk_static_str(),
3461 ast::LitKind::ByteStr(ref v) => {
3462 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3463 tcx.mk_array(tcx.types.u8, v.len() as u64))
3465 ast::LitKind::Byte(_) => tcx.types.u8,
3466 ast::LitKind::Char(_) => tcx.types.char,
3467 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3468 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3469 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3470 let opt_ty = expected.to_option(self).and_then(|ty| {
3472 ty::Int(_) | ty::Uint(_) => Some(ty),
3473 ty::Char => Some(tcx.types.u8),
3474 ty::RawPtr(..) => Some(tcx.types.usize),
3475 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3479 opt_ty.unwrap_or_else(|| self.next_int_var())
3481 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3482 ast::LitKind::FloatUnsuffixed(_) => {
3483 let opt_ty = expected.to_option(self).and_then(|ty| {
3485 ty::Float(_) => Some(ty),
3489 opt_ty.unwrap_or_else(|| self.next_float_var())
3491 ast::LitKind::Bool(_) => tcx.types.bool,
3492 ast::LitKind::Err(_) => tcx.types.err,
3496 // Determine the `Self` type, using fresh variables for all variables
3497 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3498 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3500 pub fn impl_self_ty(&self,
3501 span: Span, // (potential) receiver for this impl
3503 -> TypeAndSubsts<'tcx> {
3504 let ity = self.tcx.type_of(did);
3505 debug!("impl_self_ty: ity={:?}", ity);
3507 let substs = self.fresh_substs_for_item(span, did);
3508 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3510 TypeAndSubsts { substs: substs, ty: substd_ty }
3513 /// Unifies the output type with the expected type early, for more coercions
3514 /// and forward type information on the input expressions.
3515 fn expected_inputs_for_expected_output(&self,
3517 expected_ret: Expectation<'tcx>,
3518 formal_ret: Ty<'tcx>,
3519 formal_args: &[Ty<'tcx>])
3521 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3522 let ret_ty = match expected_ret.only_has_type(self) {
3524 None => return Vec::new()
3526 let expect_args = self.fudge_inference_if_ok(|| {
3527 // Attempt to apply a subtyping relationship between the formal
3528 // return type (likely containing type variables if the function
3529 // is polymorphic) and the expected return type.
3530 // No argument expectations are produced if unification fails.
3531 let origin = self.misc(call_span);
3532 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3534 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3535 // to identity so the resulting type is not constrained.
3538 // Process any obligations locally as much as
3539 // we can. We don't care if some things turn
3540 // out unconstrained or ambiguous, as we're
3541 // just trying to get hints here.
3542 self.save_and_restore_in_snapshot_flag(|_| {
3543 let mut fulfill = TraitEngine::new(self.tcx);
3544 for obligation in ok.obligations {
3545 fulfill.register_predicate_obligation(self, obligation);
3547 fulfill.select_where_possible(self)
3548 }).map_err(|_| ())?;
3550 Err(_) => return Err(()),
3553 // Record all the argument types, with the substitutions
3554 // produced from the above subtyping unification.
3555 Ok(formal_args.iter().map(|ty| {
3556 self.resolve_vars_if_possible(ty)
3558 }).unwrap_or_default();
3559 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3560 formal_args, formal_ret,
3561 expect_args, expected_ret);
3565 pub fn check_struct_path(&self,
3568 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3569 let path_span = match *qpath {
3570 QPath::Resolved(_, ref path) => path.span,
3571 QPath::TypeRelative(ref qself, _) => qself.span
3573 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3574 let variant = match def {
3576 self.set_tainted_by_errors();
3579 Res::Def(DefKind::Variant, _) => {
3581 ty::Adt(adt, substs) => {
3582 Some((adt.variant_of_res(def), adt.did, substs))
3584 _ => bug!("unexpected type: {:?}", ty)
3587 Res::Def(DefKind::Struct, _)
3588 | Res::Def(DefKind::Union, _)
3589 | Res::Def(DefKind::TyAlias, _)
3590 | Res::Def(DefKind::AssocTy, _)
3591 | Res::SelfTy(..) => {
3593 ty::Adt(adt, substs) if !adt.is_enum() => {
3594 Some((adt.non_enum_variant(), adt.did, substs))
3599 _ => bug!("unexpected definition: {:?}", def)
3602 if let Some((variant, did, substs)) = variant {
3603 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3604 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3606 // Check bounds on type arguments used in the path.
3607 let bounds = self.instantiate_bounds(path_span, did, substs);
3608 let cause = traits::ObligationCause::new(
3611 traits::ItemObligation(did),
3613 self.add_obligations_for_parameters(cause, &bounds);
3617 struct_span_err!(self.tcx.sess, path_span, E0071,
3618 "expected struct, variant or union type, found {}",
3619 ty.sort_string(self.tcx))
3620 .span_label(path_span, "not a struct")
3626 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3627 // The newly resolved definition is written into `type_dependent_defs`.
3628 fn finish_resolving_struct_path(&self,
3635 QPath::Resolved(ref maybe_qself, ref path) => {
3636 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3637 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3640 QPath::TypeRelative(ref qself, ref segment) => {
3641 let ty = self.to_ty(qself);
3643 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.node {
3648 let result = AstConv::associated_path_to_ty(
3657 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3658 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3660 // Write back the new resolution.
3661 self.write_resolution(hir_id, result);
3663 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3668 /// Resolves an associated value path into a base type and associated constant, or method
3669 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3670 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3674 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3676 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3677 let (ty, qself, item_segment) = match *qpath {
3678 QPath::Resolved(ref opt_qself, ref path) => {
3680 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3681 &path.segments[..]);
3683 QPath::TypeRelative(ref qself, ref segment) => {
3684 (self.to_ty(qself), qself, segment)
3687 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3688 // Return directly on cache hit. This is useful to avoid doubly reporting
3689 // errors with default match binding modes. See #44614.
3690 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3691 .unwrap_or(Res::Err);
3692 return (def, Some(ty), slice::from_ref(&**item_segment));
3694 let item_name = item_segment.ident;
3695 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3696 let result = match error {
3697 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3698 _ => Err(ErrorReported),
3700 if item_name.name != kw::Invalid {
3701 self.report_method_error(
3705 SelfSource::QPath(qself),
3708 ).map(|mut e| e.emit());
3713 // Write back the new resolution.
3714 self.write_resolution(hir_id, result);
3716 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3718 slice::from_ref(&**item_segment),
3722 pub fn check_decl_initializer(
3724 local: &'tcx hir::Local,
3725 init: &'tcx hir::Expr,
3727 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3728 // for #42640 (default match binding modes).
3731 let ref_bindings = local.pat.contains_explicit_ref_binding();
3733 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3734 if let Some(m) = ref_bindings {
3735 // Somewhat subtle: if we have a `ref` binding in the pattern,
3736 // we want to avoid introducing coercions for the RHS. This is
3737 // both because it helps preserve sanity and, in the case of
3738 // ref mut, for soundness (issue #23116). In particular, in
3739 // the latter case, we need to be clear that the type of the
3740 // referent for the reference that results is *equal to* the
3741 // type of the place it is referencing, and not some
3742 // supertype thereof.
3743 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3744 self.demand_eqtype(init.span, local_ty, init_ty);
3747 self.check_expr_coercable_to_type(init, local_ty)
3751 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3752 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3753 self.write_ty(local.hir_id, t);
3755 if let Some(ref init) = local.init {
3756 let init_ty = self.check_decl_initializer(local, &init);
3757 self.overwrite_local_ty_if_err(local, t, init_ty);
3760 self.check_pat_top(&local.pat, t, None);
3761 let pat_ty = self.node_ty(local.pat.hir_id);
3762 self.overwrite_local_ty_if_err(local, t, pat_ty);
3765 fn overwrite_local_ty_if_err(&self, local: &'tcx hir::Local, decl_ty: Ty<'tcx>, ty: Ty<'tcx>) {
3766 if ty.references_error() {
3767 // Override the types everywhere with `types.err` to avoid knock down errors.
3768 self.write_ty(local.hir_id, ty);
3769 self.write_ty(local.pat.hir_id, ty);
3770 let local_ty = LocalTy {
3774 self.locals.borrow_mut().insert(local.hir_id, local_ty);
3775 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
3779 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3780 // Don't do all the complex logic below for `DeclItem`.
3782 hir::StmtKind::Item(..) => return,
3783 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3786 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3788 // Hide the outer diverging and `has_errors` flags.
3789 let old_diverges = self.diverges.get();
3790 let old_has_errors = self.has_errors.get();
3791 self.diverges.set(Diverges::Maybe);
3792 self.has_errors.set(false);
3795 hir::StmtKind::Local(ref l) => {
3796 self.check_decl_local(&l);
3799 hir::StmtKind::Item(_) => {}
3800 hir::StmtKind::Expr(ref expr) => {
3801 // Check with expected type of `()`.
3802 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit());
3804 hir::StmtKind::Semi(ref expr) => {
3805 self.check_expr(&expr);
3809 // Combine the diverging and `has_error` flags.
3810 self.diverges.set(self.diverges.get() | old_diverges);
3811 self.has_errors.set(self.has_errors.get() | old_has_errors);
3814 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
3815 let unit = self.tcx.mk_unit();
3816 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
3818 // if the block produces a `!` value, that can always be
3819 // (effectively) coerced to unit.
3821 self.demand_suptype(blk.span, unit, ty);
3825 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
3826 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
3827 /// when given code like the following:
3829 /// if false { return 0i32; } else { 1u32 }
3830 /// // ^^^^ point at this instead of the whole `if` expression
3832 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
3833 if let hir::ExprKind::Match(_, arms, _) = &expr.node {
3834 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
3835 self.in_progress_tables
3836 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
3837 .and_then(|arm_ty| {
3838 if arm_ty.is_never() {
3841 Some(match &arm.body.node {
3842 // Point at the tail expression when possible.
3843 hir::ExprKind::Block(block, _) => block.expr
3846 .unwrap_or(block.span),
3852 if arm_spans.len() == 1 {
3853 return arm_spans[0];
3859 fn check_block_with_expected(
3861 blk: &'tcx hir::Block,
3862 expected: Expectation<'tcx>,
3865 let mut fcx_ps = self.ps.borrow_mut();
3866 let unsafety_state = fcx_ps.recurse(blk);
3867 replace(&mut *fcx_ps, unsafety_state)
3870 // In some cases, blocks have just one exit, but other blocks
3871 // can be targeted by multiple breaks. This can happen both
3872 // with labeled blocks as well as when we desugar
3873 // a `try { ... }` expression.
3877 // 'a: { if true { break 'a Err(()); } Ok(()) }
3879 // Here we would wind up with two coercions, one from
3880 // `Err(())` and the other from the tail expression
3881 // `Ok(())`. If the tail expression is omitted, that's a
3882 // "forced unit" -- unless the block diverges, in which
3883 // case we can ignore the tail expression (e.g., `'a: {
3884 // break 'a 22; }` would not force the type of the block
3886 let tail_expr = blk.expr.as_ref();
3887 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
3888 let coerce = if blk.targeted_by_break {
3889 CoerceMany::new(coerce_to_ty)
3891 let tail_expr: &[P<hir::Expr>] = match tail_expr {
3892 Some(e) => slice::from_ref(e),
3895 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
3898 let prev_diverges = self.diverges.get();
3899 let ctxt = BreakableCtxt {
3900 coerce: Some(coerce),
3904 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
3905 for s in &blk.stmts {
3909 // check the tail expression **without** holding the
3910 // `enclosing_breakables` lock below.
3911 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
3913 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3914 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
3915 let coerce = ctxt.coerce.as_mut().unwrap();
3916 if let Some(tail_expr_ty) = tail_expr_ty {
3917 let tail_expr = tail_expr.unwrap();
3918 let span = self.get_expr_coercion_span(tail_expr);
3919 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
3920 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
3922 // Subtle: if there is no explicit tail expression,
3923 // that is typically equivalent to a tail expression
3924 // of `()` -- except if the block diverges. In that
3925 // case, there is no value supplied from the tail
3926 // expression (assuming there are no other breaks,
3927 // this implies that the type of the block will be
3930 // #41425 -- label the implicit `()` as being the
3931 // "found type" here, rather than the "expected type".
3932 if !self.diverges.get().is_always() {
3933 // #50009 -- Do not point at the entire fn block span, point at the return type
3934 // span, as it is the cause of the requirement, and
3935 // `consider_hint_about_removing_semicolon` will point at the last expression
3936 // if it were a relevant part of the error. This improves usability in editors
3937 // that highlight errors inline.
3938 let mut sp = blk.span;
3939 let mut fn_span = None;
3940 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
3941 let ret_sp = decl.output.span();
3942 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
3943 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
3944 // output would otherwise be incorrect and even misleading. Make sure
3945 // the span we're aiming at correspond to a `fn` body.
3946 if block_sp == blk.span {
3948 fn_span = Some(ident.span);
3952 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
3953 if let Some(expected_ty) = expected.only_has_type(self) {
3954 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
3956 if let Some(fn_span) = fn_span {
3959 "implicitly returns `()` as its body has no tail or `return` \
3969 // If we can break from the block, then the block's exit is always reachable
3970 // (... as long as the entry is reachable) - regardless of the tail of the block.
3971 self.diverges.set(prev_diverges);
3974 let mut ty = ctxt.coerce.unwrap().complete(self);
3976 if self.has_errors.get() || ty.references_error() {
3977 ty = self.tcx.types.err
3980 self.write_ty(blk.hir_id, ty);
3982 *self.ps.borrow_mut() = prev;
3986 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
3987 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
3989 Node::Item(&hir::Item {
3990 node: hir::ItemKind::Fn(_, _, _, body_id), ..
3992 Node::ImplItem(&hir::ImplItem {
3993 node: hir::ImplItemKind::Method(_, body_id), ..
3995 let body = self.tcx.hir().body(body_id);
3996 if let ExprKind::Block(block, _) = &body.value.node {
3997 return Some(block.span);
4005 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4006 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
4007 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4008 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4011 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4012 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
4014 Node::Item(&hir::Item {
4015 ident, node: hir::ItemKind::Fn(ref decl, ..), ..
4017 // This is less than ideal, it will not suggest a return type span on any
4018 // method called `main`, regardless of whether it is actually the entry point,
4019 // but it will still present it as the reason for the expected type.
4020 Some((decl, ident, ident.name != sym::main))
4022 Node::TraitItem(&hir::TraitItem {
4023 ident, node: hir::TraitItemKind::Method(hir::MethodSig {
4026 }) => Some((decl, ident, true)),
4027 Node::ImplItem(&hir::ImplItem {
4028 ident, node: hir::ImplItemKind::Method(hir::MethodSig {
4031 }) => Some((decl, ident, false)),
4036 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4037 /// suggestion can be made, `None` otherwise.
4038 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
4039 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4040 // `while` before reaching it, as block tail returns are not available in them.
4041 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4042 let parent = self.tcx.hir().get(blk_id);
4043 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4047 /// On implicit return expressions with mismatched types, provides the following suggestions:
4049 /// - Points out the method's return type as the reason for the expected type.
4050 /// - Possible missing semicolon.
4051 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4052 pub fn suggest_mismatched_types_on_tail(
4054 err: &mut DiagnosticBuilder<'tcx>,
4055 expression: &'tcx hir::Expr,
4061 self.suggest_missing_semicolon(err, expression, expected, cause_span);
4062 let mut pointing_at_return_type = false;
4063 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4064 pointing_at_return_type = self.suggest_missing_return_type(
4065 err, &fn_decl, expected, found, can_suggest);
4067 self.suggest_ref_or_into(err, expression, expected, found);
4068 self.suggest_boxing_when_appropriate(err, expression, expected, found);
4069 pointing_at_return_type
4072 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4073 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4075 /// fn foo(x: usize) -> usize { x }
4076 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4080 err: &mut DiagnosticBuilder<'tcx>,
4085 let hir = self.tcx.hir();
4086 let (def_id, sig) = match found.sty {
4087 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4088 ty::Closure(def_id, substs) => {
4089 // We don't use `closure_sig` to account for malformed closures like
4090 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4091 let closure_sig_ty = substs.closure_sig_ty(def_id, self.tcx);
4092 (def_id, match closure_sig_ty.sty {
4093 ty::FnPtr(sig) => sig,
4101 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4103 let sig = self.normalize_associated_types_in(expr.span, &sig);
4104 if self.can_coerce(sig.output(), expected) {
4105 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4106 (String::new(), Applicability::MachineApplicable)
4108 ("...".to_string(), Applicability::HasPlaceholders)
4110 let mut msg = "call this function";
4111 match hir.get_if_local(def_id) {
4112 Some(Node::Item(hir::Item {
4113 node: ItemKind::Fn(.., body_id),
4116 Some(Node::ImplItem(hir::ImplItem {
4117 node: hir::ImplItemKind::Method(_, body_id),
4120 Some(Node::TraitItem(hir::TraitItem {
4121 node: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4124 let body = hir.body(*body_id);
4125 sugg_call = body.params.iter()
4126 .map(|param| match ¶m.pat.node {
4127 hir::PatKind::Binding(_, _, ident, None)
4128 if ident.name != kw::SelfLower => ident.to_string(),
4129 _ => "_".to_string(),
4130 }).collect::<Vec<_>>().join(", ");
4132 Some(Node::Expr(hir::Expr {
4133 node: ExprKind::Closure(_, _, body_id, closure_span, _),
4134 span: full_closure_span,
4137 if *full_closure_span == expr.span {
4140 err.span_label(*closure_span, "closure defined here");
4141 msg = "call this closure";
4142 let body = hir.body(*body_id);
4143 sugg_call = body.params.iter()
4144 .map(|param| match ¶m.pat.node {
4145 hir::PatKind::Binding(_, _, ident, None)
4146 if ident.name != kw::SelfLower => ident.to_string(),
4147 _ => "_".to_string(),
4148 }).collect::<Vec<_>>().join(", ");
4150 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4151 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4152 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4153 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4154 msg = "instantiate this tuple variant";
4156 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4157 msg = "instantiate this tuple struct";
4162 Some(Node::ForeignItem(hir::ForeignItem {
4163 node: hir::ForeignItemKind::Fn(_, idents, _),
4166 Some(Node::TraitItem(hir::TraitItem {
4167 node: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4169 })) => sugg_call = idents.iter()
4170 .map(|ident| if ident.name != kw::SelfLower {
4174 }).collect::<Vec<_>>()
4178 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4179 err.span_suggestion(
4181 &format!("use parentheses to {}", msg),
4182 format!("{}({})", code, sugg_call),
4191 pub fn suggest_ref_or_into(
4193 err: &mut DiagnosticBuilder<'tcx>,
4198 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4199 err.span_suggestion(
4203 Applicability::MachineApplicable,
4205 } else if let (ty::FnDef(def_id, ..), true) = (
4207 self.suggest_fn_call(err, expr, expected, found),
4209 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4210 let sp = self.sess().source_map().def_span(sp);
4211 err.span_label(sp, &format!("{} defined here", found));
4213 } else if !self.check_for_cast(err, expr, found, expected) {
4214 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4218 let methods = self.get_conversion_methods(expr.span, expected, found);
4219 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4220 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4221 .filter_map(|(receiver, method)| {
4222 let method_call = format!(".{}()", method.ident);
4223 if receiver.ends_with(&method_call) {
4224 None // do not suggest code that is already there (#53348)
4226 let method_call_list = [".to_vec()", ".to_string()"];
4227 let sugg = if receiver.ends_with(".clone()")
4228 && method_call_list.contains(&method_call.as_str()) {
4229 let max_len = receiver.rfind(".").unwrap();
4230 format!("{}{}", &receiver[..max_len], method_call)
4232 format!("{}{}", receiver, method_call)
4234 Some(if is_struct_pat_shorthand_field {
4235 format!("{}: {}", receiver, sugg)
4241 if suggestions.peek().is_some() {
4242 err.span_suggestions(
4244 "try using a conversion method",
4246 Applicability::MaybeIncorrect,
4253 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4254 /// in the heap by calling `Box::new()`.
4255 fn suggest_boxing_when_appropriate(
4257 err: &mut DiagnosticBuilder<'tcx>,
4262 if self.tcx.hir().is_const_context(expr.hir_id) {
4263 // Do not suggest `Box::new` in const context.
4266 if !expected.is_box() || found.is_box() {
4269 let boxed_found = self.tcx.mk_box(found);
4270 if let (true, Ok(snippet)) = (
4271 self.can_coerce(boxed_found, expected),
4272 self.sess().source_map().span_to_snippet(expr.span),
4274 err.span_suggestion(
4276 "store this in the heap by calling `Box::new`",
4277 format!("Box::new({})", snippet),
4278 Applicability::MachineApplicable,
4280 err.note("for more on the distinction between the stack and the \
4281 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4282 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4283 https://doc.rust-lang.org/std/boxed/index.html");
4288 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4292 /// bar_that_returns_u32()
4296 /// This routine checks if the return expression in a block would make sense on its own as a
4297 /// statement and the return type has been left as default or has been specified as `()`. If so,
4298 /// it suggests adding a semicolon.
4299 fn suggest_missing_semicolon(
4301 err: &mut DiagnosticBuilder<'tcx>,
4302 expression: &'tcx hir::Expr,
4306 if expected.is_unit() {
4307 // `BlockTailExpression` only relevant if the tail expr would be
4308 // useful on its own.
4309 match expression.node {
4310 ExprKind::Call(..) |
4311 ExprKind::MethodCall(..) |
4312 ExprKind::Loop(..) |
4313 ExprKind::Match(..) |
4314 ExprKind::Block(..) => {
4315 let sp = self.tcx.sess.source_map().next_point(cause_span);
4316 err.span_suggestion(
4318 "try adding a semicolon",
4320 Applicability::MachineApplicable);
4327 /// A possible error is to forget to add a return type that is needed:
4331 /// bar_that_returns_u32()
4335 /// This routine checks if the return type is left as default, the method is not part of an
4336 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4338 fn suggest_missing_return_type(
4340 err: &mut DiagnosticBuilder<'tcx>,
4341 fn_decl: &hir::FnDecl,
4346 // Only suggest changing the return type for methods that
4347 // haven't set a return type at all (and aren't `fn main()` or an impl).
4348 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4349 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4350 err.span_suggestion(
4352 "try adding a return type",
4353 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
4354 Applicability::MachineApplicable);
4357 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4358 err.span_label(span, "possibly return type missing here?");
4361 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4362 // `fn main()` must return `()`, do not suggest changing return type
4363 err.span_label(span, "expected `()` because of default return type");
4366 // expectation was caused by something else, not the default return
4367 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4368 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4369 // Only point to return type if the expected type is the return type, as if they
4370 // are not, the expectation must have been caused by something else.
4371 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.node);
4373 let ty = AstConv::ast_ty_to_ty(self, ty);
4374 debug!("suggest_missing_return_type: return type {:?}", ty);
4375 debug!("suggest_missing_return_type: expected type {:?}", ty);
4376 if ty.sty == expected.sty {
4377 err.span_label(sp, format!("expected `{}` because of return type",
4386 /// A possible error is to forget to add `.await` when using futures:
4389 /// async fn make_u32() -> u32 {
4393 /// fn take_u32(x: u32) {}
4395 /// async fn foo() {
4396 /// let x = make_u32();
4401 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4402 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4403 /// `.await` to the tail of the expression.
4404 fn suggest_missing_await(
4406 err: &mut DiagnosticBuilder<'tcx>,
4411 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4412 // body isn't `async`.
4413 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4414 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4415 let body = self.tcx().hir().body(body_id);
4416 if let Some(hir::GeneratorKind::Async) = body.generator_kind {
4418 // Check for `Future` implementations by constructing a predicate to
4419 // prove: `<T as Future>::Output == U`
4420 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4421 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4422 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4423 // `<T as Future>::Output`
4424 projection_ty: ty::ProjectionTy {
4426 substs: self.tcx.mk_substs_trait(
4428 self.fresh_substs_for_item(sp, item_def_id)
4435 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4436 if self.infcx.predicate_may_hold(&obligation) {
4437 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4438 err.span_suggestion(
4440 "consider using `.await` here",
4441 format!("{}.await", code),
4442 Applicability::MaybeIncorrect,
4450 /// A common error is to add an extra semicolon:
4453 /// fn foo() -> usize {
4458 /// This routine checks if the final statement in a block is an
4459 /// expression with an explicit semicolon whose type is compatible
4460 /// with `expected_ty`. If so, it suggests removing the semicolon.
4461 fn consider_hint_about_removing_semicolon(
4463 blk: &'tcx hir::Block,
4464 expected_ty: Ty<'tcx>,
4465 err: &mut DiagnosticBuilder<'_>,
4467 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4468 err.span_suggestion(
4470 "consider removing this semicolon",
4472 Applicability::MachineApplicable,
4477 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4478 // Be helpful when the user wrote `{... expr;}` and
4479 // taking the `;` off is enough to fix the error.
4480 let last_stmt = blk.stmts.last()?;
4481 let last_expr = match last_stmt.node {
4482 hir::StmtKind::Semi(ref e) => e,
4485 let last_expr_ty = self.node_ty(last_expr.hir_id);
4486 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4489 let original_span = original_sp(last_stmt.span, blk.span);
4490 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4493 // Instantiates the given path, which must refer to an item with the given
4494 // number of type parameters and type.
4495 pub fn instantiate_value_path(&self,
4496 segments: &[hir::PathSegment],
4497 self_ty: Option<Ty<'tcx>>,
4501 -> (Ty<'tcx>, Res) {
4503 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4512 let path_segs = match res {
4513 Res::Local(_) | Res::SelfCtor(_) => vec![],
4514 Res::Def(kind, def_id) =>
4515 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4516 _ => bug!("instantiate_value_path on {:?}", res),
4519 let mut user_self_ty = None;
4520 let mut is_alias_variant_ctor = false;
4522 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4523 if let Some(self_ty) = self_ty {
4524 let adt_def = self_ty.ty_adt_def().unwrap();
4525 user_self_ty = Some(UserSelfTy {
4526 impl_def_id: adt_def.did,
4529 is_alias_variant_ctor = true;
4532 Res::Def(DefKind::Method, def_id)
4533 | Res::Def(DefKind::AssocConst, def_id) => {
4534 let container = tcx.associated_item(def_id).container;
4535 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4537 ty::TraitContainer(trait_did) => {
4538 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4540 ty::ImplContainer(impl_def_id) => {
4541 if segments.len() == 1 {
4542 // `<T>::assoc` will end up here, and so
4543 // can `T::assoc`. It this came from an
4544 // inherent impl, we need to record the
4545 // `T` for posterity (see `UserSelfTy` for
4547 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4548 user_self_ty = Some(UserSelfTy {
4559 // Now that we have categorized what space the parameters for each
4560 // segment belong to, let's sort out the parameters that the user
4561 // provided (if any) into their appropriate spaces. We'll also report
4562 // errors if type parameters are provided in an inappropriate place.
4564 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4565 let generics_has_err = AstConv::prohibit_generics(
4566 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4567 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4574 if let Res::Local(hid) = res {
4575 let ty = self.local_ty(span, hid).decl_ty;
4576 let ty = self.normalize_associated_types_in(span, &ty);
4577 self.write_ty(hir_id, ty);
4581 if generics_has_err {
4582 // Don't try to infer type parameters when prohibited generic arguments were given.
4583 user_self_ty = None;
4586 // Now we have to compare the types that the user *actually*
4587 // provided against the types that were *expected*. If the user
4588 // did not provide any types, then we want to substitute inference
4589 // variables. If the user provided some types, we may still need
4590 // to add defaults. If the user provided *too many* types, that's
4593 let mut infer_args_for_err = FxHashSet::default();
4594 for &PathSeg(def_id, index) in &path_segs {
4595 let seg = &segments[index];
4596 let generics = tcx.generics_of(def_id);
4597 // Argument-position `impl Trait` is treated as a normal generic
4598 // parameter internally, but we don't allow users to specify the
4599 // parameter's value explicitly, so we have to do some error-
4601 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4606 false, // `is_method_call`
4608 if suppress_errors {
4609 infer_args_for_err.insert(index);
4610 self.set_tainted_by_errors(); // See issue #53251.
4614 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4615 tcx.generics_of(*def_id).has_self
4616 }).unwrap_or(false);
4618 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4619 let ty = self.impl_self_ty(span, impl_def_id).ty;
4620 let adt_def = ty.ty_adt_def();
4623 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4624 let variant = adt_def.non_enum_variant();
4625 let ctor_def_id = variant.ctor_def_id.unwrap();
4627 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4632 let mut err = tcx.sess.struct_span_err(span,
4633 "the `Self` constructor can only be used with tuple or unit structs");
4634 if let Some(adt_def) = adt_def {
4635 match adt_def.adt_kind() {
4637 err.help("did you mean to use one of the enum's variants?");
4641 err.span_suggestion(
4643 "use curly brackets",
4644 String::from("Self { /* fields */ }"),
4645 Applicability::HasPlaceholders,
4652 return (tcx.types.err, res)
4658 let def_id = res.def_id();
4660 // The things we are substituting into the type should not contain
4661 // escaping late-bound regions, and nor should the base type scheme.
4662 let ty = tcx.type_of(def_id);
4664 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4670 // Provide the generic args, and whether types should be inferred.
4672 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4675 // If we've encountered an `impl Trait`-related error, we're just
4676 // going to infer the arguments for better error messages.
4677 if !infer_args_for_err.contains(&index) {
4678 // Check whether the user has provided generic arguments.
4679 if let Some(ref data) = segments[index].args {
4680 return (Some(data), segments[index].infer_args);
4683 return (None, segments[index].infer_args);
4688 // Provide substitutions for parameters for which (valid) arguments have been provided.
4690 match (¶m.kind, arg) {
4691 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4692 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4694 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4695 self.to_ty(ty).into()
4697 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4698 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4700 _ => unreachable!(),
4703 // Provide substitutions for parameters for which arguments are inferred.
4704 |substs, param, infer_args| {
4706 GenericParamDefKind::Lifetime => {
4707 self.re_infer(Some(param), span).unwrap().into()
4709 GenericParamDefKind::Type { has_default, .. } => {
4710 if !infer_args && has_default {
4711 // If we have a default, then we it doesn't matter that we're not
4712 // inferring the type arguments: we provide the default where any
4714 let default = tcx.type_of(param.def_id);
4717 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4720 // If no type arguments were provided, we have to infer them.
4721 // This case also occurs as a result of some malformed input, e.g.
4722 // a lifetime argument being given instead of a type parameter.
4723 // Using inference instead of `Error` gives better error messages.
4724 self.var_for_def(span, param)
4727 GenericParamDefKind::Const => {
4728 // FIXME(const_generics:defaults)
4729 // No const parameters were provided, we have to infer them.
4730 self.var_for_def(span, param)
4735 assert!(!substs.has_escaping_bound_vars());
4736 assert!(!ty.has_escaping_bound_vars());
4738 // First, store the "user substs" for later.
4739 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4741 // Add all the obligations that are required, substituting and
4742 // normalized appropriately.
4743 let bounds = self.instantiate_bounds(span, def_id, &substs);
4744 self.add_obligations_for_parameters(
4745 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
4749 // Substitute the values for the type parameters into the type of
4750 // the referenced item.
4751 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4753 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4754 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4755 // is inherent, there is no `Self` parameter; instead, the impl needs
4756 // type parameters, which we can infer by unifying the provided `Self`
4757 // with the substituted impl type.
4758 // This also occurs for an enum variant on a type alias.
4759 let ty = tcx.type_of(impl_def_id);
4761 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4762 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4763 Ok(ok) => self.register_infer_ok_obligations(ok),
4765 self.tcx.sess.delay_span_bug(span, &format!(
4766 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4774 self.check_rustc_args_require_const(def_id, hir_id, span);
4776 debug!("instantiate_value_path: type of {:?} is {:?}",
4779 self.write_substs(hir_id, substs);
4781 (ty_substituted, res)
4784 fn check_rustc_args_require_const(&self,
4788 // We're only interested in functions tagged with
4789 // #[rustc_args_required_const], so ignore anything that's not.
4790 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
4794 // If our calling expression is indeed the function itself, we're good!
4795 // If not, generate an error that this can only be called directly.
4796 if let Node::Expr(expr) = self.tcx.hir().get(
4797 self.tcx.hir().get_parent_node(hir_id))
4799 if let ExprKind::Call(ref callee, ..) = expr.node {
4800 if callee.hir_id == hir_id {
4806 self.tcx.sess.span_err(span, "this function can only be invoked \
4807 directly, not through a function pointer");
4810 // Resolves `typ` by a single level if `typ` is a type variable.
4811 // If no resolution is possible, then an error is reported.
4812 // Numeric inference variables may be left unresolved.
4813 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4814 let ty = self.resolve_type_vars_with_obligations(ty);
4815 if !ty.is_ty_var() {
4818 if !self.is_tainted_by_errors() {
4819 self.need_type_info_err((**self).body_id, sp, ty)
4820 .note("type must be known at this point")
4823 self.demand_suptype(sp, self.tcx.types.err, ty);
4828 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
4831 ctxt: BreakableCtxt<'tcx>,
4833 ) -> (BreakableCtxt<'tcx>, R) {
4836 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4837 index = enclosing_breakables.stack.len();
4838 enclosing_breakables.by_id.insert(id, index);
4839 enclosing_breakables.stack.push(ctxt);
4843 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4844 debug_assert!(enclosing_breakables.stack.len() == index + 1);
4845 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
4846 enclosing_breakables.stack.pop().expect("missing breakable context")
4851 /// Instantiate a QueryResponse in a probe context, without a
4852 /// good ObligationCause.
4853 fn probe_instantiate_query_response(
4856 original_values: &OriginalQueryValues<'tcx>,
4857 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
4858 ) -> InferResult<'tcx, Ty<'tcx>>
4860 self.instantiate_query_response_and_region_obligations(
4861 &traits::ObligationCause::misc(span, self.body_id),
4867 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
4868 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
4869 let mut contained_in_place = false;
4871 while let hir::Node::Expr(parent_expr) =
4872 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
4874 match &parent_expr.node {
4875 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
4876 if lhs.hir_id == expr_id {
4877 contained_in_place = true;
4883 expr_id = parent_expr.hir_id;
4890 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
4891 let own_counts = generics.own_counts();
4893 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
4899 if own_counts.types == 0 {
4903 // Make a vector of booleans initially `false`; set to `true` when used.
4904 let mut types_used = vec![false; own_counts.types];
4906 for leaf_ty in ty.walk() {
4907 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.sty {
4908 debug!("found use of ty param num {}", index);
4909 types_used[index as usize - own_counts.lifetimes] = true;
4910 } else if let ty::Error = leaf_ty.sty {
4911 // If there is already another error, do not emit
4912 // an error for not using a type parameter.
4913 assert!(tcx.sess.has_errors());
4918 let types = generics.params.iter().filter(|param| match param.kind {
4919 ty::GenericParamDefKind::Type { .. } => true,
4922 for (&used, param) in types_used.iter().zip(types) {
4924 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
4925 let span = tcx.hir().span(id);
4926 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
4927 .span_label(span, "unused type parameter")
4933 fn fatally_break_rust(sess: &Session) {
4934 let handler = sess.diagnostic();
4935 handler.span_bug_no_panic(
4937 "It looks like you're trying to break rust; would you like some ICE?",
4939 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
4940 handler.note_without_error(
4941 "we would appreciate a joke overview: \
4942 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
4944 handler.note_without_error(&format!("rustc {} running on {}",
4945 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
4946 crate::session::config::host_triple(),
4950 fn potentially_plural_count(count: usize, word: &str) -> String {
4951 format!("{} {}{}", count, word, pluralise!(count))