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)]
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(
2624 substs: SubstsRef<'tcx>,
2625 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
2626 let bounds = self.tcx.predicates_of(def_id);
2627 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
2628 let result = bounds.instantiate(self.tcx, substs);
2629 let result = self.normalize_associated_types_in(span, &result);
2631 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
2640 /// Replaces the opaque types from the given value with type variables,
2641 /// and records the `OpaqueTypeMap` for later use during writeback. See
2642 /// `InferCtxt::instantiate_opaque_types` for more details.
2643 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2645 parent_id: hir::HirId,
2649 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2650 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2654 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2655 self.instantiate_opaque_types(
2664 let mut opaque_types = self.opaque_types.borrow_mut();
2665 for (ty, decl) in opaque_type_map {
2666 let old_value = opaque_types.insert(ty, decl);
2667 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2673 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2674 where T : TypeFoldable<'tcx>
2676 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2679 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2681 where T : TypeFoldable<'tcx>
2683 self.inh.partially_normalize_associated_types_in(span,
2689 pub fn require_type_meets(&self,
2692 code: traits::ObligationCauseCode<'tcx>,
2695 self.register_bound(
2698 traits::ObligationCause::new(span, self.body_id, code));
2701 pub fn require_type_is_sized(&self,
2704 code: traits::ObligationCauseCode<'tcx>)
2706 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2707 self.require_type_meets(ty, span, code, lang_item);
2710 pub fn require_type_is_sized_deferred(&self,
2713 code: traits::ObligationCauseCode<'tcx>)
2715 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2718 pub fn register_bound(&self,
2721 cause: traits::ObligationCause<'tcx>)
2723 self.fulfillment_cx.borrow_mut()
2724 .register_bound(self, self.param_env, ty, def_id, cause);
2727 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2728 let t = AstConv::ast_ty_to_ty(self, ast_t);
2729 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2733 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2734 let ty = self.to_ty(ast_ty);
2735 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2737 if Self::can_contain_user_lifetime_bounds(ty) {
2738 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2739 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2740 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2746 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2747 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2748 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2751 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2752 AstConv::ast_const_to_const(self, ast_c, ty)
2755 // If the type given by the user has free regions, save it for later, since
2756 // NLL would like to enforce those. Also pass in types that involve
2757 // projections, since those can resolve to `'static` bounds (modulo #54940,
2758 // which hopefully will be fixed by the time you see this comment, dear
2759 // reader, although I have my doubts). Also pass in types with inference
2760 // types, because they may be repeated. Other sorts of things are already
2761 // sufficiently enforced with erased regions. =)
2762 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2764 T: TypeFoldable<'tcx>
2766 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2769 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2770 match self.tables.borrow().node_types().get(id) {
2772 None if self.is_tainted_by_errors() => self.tcx.types.err,
2774 bug!("no type for node {}: {} in fcx {}",
2775 id, self.tcx.hir().node_to_string(id),
2781 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2782 /// outlive the region `r`.
2783 pub fn register_wf_obligation(&self,
2786 code: traits::ObligationCauseCode<'tcx>)
2788 // WF obligations never themselves fail, so no real need to give a detailed cause:
2789 let cause = traits::ObligationCause::new(span, self.body_id, code);
2790 self.register_predicate(traits::Obligation::new(cause,
2792 ty::Predicate::WellFormed(ty)));
2795 /// Registers obligations that all types appearing in `substs` are well-formed.
2796 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2797 for ty in substs.types() {
2798 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2802 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2803 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2804 /// trait/region obligations.
2806 /// For example, if there is a function:
2809 /// fn foo<'a,T:'a>(...)
2812 /// and a reference:
2818 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2819 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2820 pub fn add_obligations_for_parameters(&self,
2821 cause: traits::ObligationCause<'tcx>,
2822 predicates: &ty::InstantiatedPredicates<'tcx>)
2824 assert!(!predicates.has_escaping_bound_vars());
2826 debug!("add_obligations_for_parameters(predicates={:?})",
2829 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2830 self.register_predicate(obligation);
2834 // FIXME(arielb1): use this instead of field.ty everywhere
2835 // Only for fields! Returns <none> for methods>
2836 // Indifferent to privacy flags
2837 pub fn field_ty(&self,
2839 field: &'tcx ty::FieldDef,
2840 substs: SubstsRef<'tcx>)
2843 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2846 fn check_casts(&self) {
2847 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2848 for cast in deferred_cast_checks.drain(..) {
2853 fn resolve_generator_interiors(&self, def_id: DefId) {
2854 let mut generators = self.deferred_generator_interiors.borrow_mut();
2855 for (body_id, interior, kind) in generators.drain(..) {
2856 self.select_obligations_where_possible(false, |_| {});
2857 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2861 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2862 // Non-numerics get replaced with ! or () (depending on whether
2863 // feature(never_type) is enabled, unconstrained ints with i32,
2864 // unconstrained floats with f64.
2865 // Fallback becomes very dubious if we have encountered type-checking errors.
2866 // In that case, fallback to Error.
2867 // The return value indicates whether fallback has occurred.
2868 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2869 use rustc::ty::error::UnconstrainedNumeric::Neither;
2870 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2872 assert!(ty.is_ty_infer());
2873 let fallback = match self.type_is_unconstrained_numeric(ty) {
2874 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2875 UnconstrainedInt => self.tcx.types.i32,
2876 UnconstrainedFloat => self.tcx.types.f64,
2877 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2878 Neither => return false,
2880 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2881 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2885 fn select_all_obligations_or_error(&self) {
2886 debug!("select_all_obligations_or_error");
2887 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2888 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2892 /// Select as many obligations as we can at present.
2893 fn select_obligations_where_possible(
2895 fallback_has_occurred: bool,
2896 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
2898 if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2899 mutate_fullfillment_errors(&mut errors);
2900 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2904 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2905 /// returns a type of `&T`, but the actual type we assign to the
2906 /// *expression* is `T`. So this function just peels off the return
2907 /// type by one layer to yield `T`.
2908 fn make_overloaded_place_return_type(&self,
2909 method: MethodCallee<'tcx>)
2910 -> ty::TypeAndMut<'tcx>
2912 // extract method return type, which will be &T;
2913 let ret_ty = method.sig.output();
2915 // method returns &T, but the type as visible to user is T, so deref
2916 ret_ty.builtin_deref(true).unwrap()
2922 base_expr: &'tcx hir::Expr,
2926 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2927 // FIXME(#18741) -- this is almost but not quite the same as the
2928 // autoderef that normal method probing does. They could likely be
2931 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2932 let mut result = None;
2933 while result.is_none() && autoderef.next().is_some() {
2934 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2936 autoderef.finalize(self);
2940 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2941 /// (and otherwise adjust) `base_expr`, looking for a type which either
2942 /// supports builtin indexing or overloaded indexing.
2943 /// This loop implements one step in that search; the autoderef loop
2944 /// is implemented by `lookup_indexing`.
2948 base_expr: &hir::Expr,
2949 autoderef: &Autoderef<'a, 'tcx>,
2952 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2953 let adjusted_ty = autoderef.unambiguous_final_ty(self);
2954 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2961 for &unsize in &[false, true] {
2962 let mut self_ty = adjusted_ty;
2964 // We only unsize arrays here.
2965 if let ty::Array(element_ty, _) = adjusted_ty.sty {
2966 self_ty = self.tcx.mk_slice(element_ty);
2972 // If some lookup succeeds, write callee into table and extract index/element
2973 // type from the method signature.
2974 // If some lookup succeeded, install method in table
2975 let input_ty = self.next_ty_var(TypeVariableOrigin {
2976 kind: TypeVariableOriginKind::AutoDeref,
2977 span: base_expr.span,
2979 let method = self.try_overloaded_place_op(
2980 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
2982 let result = method.map(|ok| {
2983 debug!("try_index_step: success, using overloaded indexing");
2984 let method = self.register_infer_ok_obligations(ok);
2986 let mut adjustments = autoderef.adjust_steps(self, needs);
2987 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].sty {
2988 let mutbl = match r_mutbl {
2989 hir::MutImmutable => AutoBorrowMutability::Immutable,
2990 hir::MutMutable => AutoBorrowMutability::Mutable {
2991 // Indexing can be desugared to a method call,
2992 // so maybe we could use two-phase here.
2993 // See the documentation of AllowTwoPhase for why that's
2994 // not the case today.
2995 allow_two_phase_borrow: AllowTwoPhase::No,
2998 adjustments.push(Adjustment {
2999 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3000 target: self.tcx.mk_ref(region, ty::TypeAndMut {
3007 adjustments.push(Adjustment {
3008 kind: Adjust::Pointer(PointerCast::Unsize),
3009 target: method.sig.inputs()[0]
3012 self.apply_adjustments(base_expr, adjustments);
3014 self.write_method_call(expr.hir_id, method);
3015 (input_ty, self.make_overloaded_place_return_type(method).ty)
3017 if result.is_some() {
3025 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3026 let (tr, name) = match (op, is_mut) {
3027 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3028 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3029 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3030 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3032 (tr, ast::Ident::with_dummy_span(name))
3035 fn try_overloaded_place_op(&self,
3038 arg_tys: &[Ty<'tcx>],
3041 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3043 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3049 // Try Mut first, if needed.
3050 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3051 let method = match (needs, mut_tr) {
3052 (Needs::MutPlace, Some(trait_did)) => {
3053 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3058 // Otherwise, fall back to the immutable version.
3059 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3060 let method = match (method, imm_tr) {
3061 (None, Some(trait_did)) => {
3062 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3064 (method, _) => method,
3070 fn check_method_argument_types(
3073 expr: &'tcx hir::Expr,
3074 method: Result<MethodCallee<'tcx>, ()>,
3075 args_no_rcvr: &'tcx [hir::Expr],
3076 tuple_arguments: TupleArgumentsFlag,
3077 expected: Expectation<'tcx>,
3080 let has_error = match method {
3082 method.substs.references_error() || method.sig.references_error()
3087 let err_inputs = self.err_args(args_no_rcvr.len());
3089 let err_inputs = match tuple_arguments {
3090 DontTupleArguments => err_inputs,
3091 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3094 self.check_argument_types(
3104 return self.tcx.types.err;
3107 let method = method.unwrap();
3108 // HACK(eddyb) ignore self in the definition (see above).
3109 let expected_arg_tys = self.expected_inputs_for_expected_output(
3112 method.sig.output(),
3113 &method.sig.inputs()[1..]
3115 self.check_argument_types(
3118 &method.sig.inputs()[1..],
3119 &expected_arg_tys[..],
3121 method.sig.c_variadic,
3123 self.tcx.hir().span_if_local(method.def_id),
3128 fn self_type_matches_expected_vid(
3130 trait_ref: ty::PolyTraitRef<'tcx>,
3131 expected_vid: ty::TyVid,
3133 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3135 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3136 trait_ref, self_ty, expected_vid
3139 ty::Infer(ty::TyVar(found_vid)) => {
3140 // FIXME: consider using `sub_root_var` here so we
3141 // can see through subtyping.
3142 let found_vid = self.root_var(found_vid);
3143 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3144 expected_vid == found_vid
3150 fn obligations_for_self_ty<'b>(
3153 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3156 // FIXME: consider using `sub_root_var` here so we
3157 // can see through subtyping.
3158 let ty_var_root = self.root_var(self_ty);
3159 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3160 self_ty, ty_var_root,
3161 self.fulfillment_cx.borrow().pending_obligations());
3165 .pending_obligations()
3167 .filter_map(move |obligation| match obligation.predicate {
3168 ty::Predicate::Projection(ref data) =>
3169 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3170 ty::Predicate::Trait(ref data) =>
3171 Some((data.to_poly_trait_ref(), obligation)),
3172 ty::Predicate::Subtype(..) => None,
3173 ty::Predicate::RegionOutlives(..) => None,
3174 ty::Predicate::TypeOutlives(..) => None,
3175 ty::Predicate::WellFormed(..) => None,
3176 ty::Predicate::ObjectSafe(..) => None,
3177 ty::Predicate::ConstEvaluatable(..) => None,
3178 // N.B., this predicate is created by breaking down a
3179 // `ClosureType: FnFoo()` predicate, where
3180 // `ClosureType` represents some `Closure`. It can't
3181 // possibly be referring to the current closure,
3182 // because we haven't produced the `Closure` for
3183 // this closure yet; this is exactly why the other
3184 // code is looking for a self type of a unresolved
3185 // inference variable.
3186 ty::Predicate::ClosureKind(..) => None,
3187 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3190 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3191 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3192 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3196 /// Generic function that factors out common logic from function calls,
3197 /// method calls and overloaded operators.
3198 fn check_argument_types(
3201 expr: &'tcx hir::Expr,
3202 fn_inputs: &[Ty<'tcx>],
3203 expected_arg_tys: &[Ty<'tcx>],
3204 args: &'tcx [hir::Expr],
3206 tuple_arguments: TupleArgumentsFlag,
3207 def_span: Option<Span>,
3210 // Grab the argument types, supplying fresh type variables
3211 // if the wrong number of arguments were supplied
3212 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3218 // All the input types from the fn signature must outlive the call
3219 // so as to validate implied bounds.
3220 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3221 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3224 let expected_arg_count = fn_inputs.len();
3226 let param_count_error = |expected_count: usize,
3231 let mut err = tcx.sess.struct_span_err_with_code(sp,
3232 &format!("this function takes {}{} but {} {} supplied",
3233 if c_variadic { "at least " } else { "" },
3234 potentially_plural_count(expected_count, "parameter"),
3235 potentially_plural_count(arg_count, "parameter"),
3236 if arg_count == 1 {"was"} else {"were"}),
3237 DiagnosticId::Error(error_code.to_owned()));
3239 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3240 err.span_label(def_s, "defined here");
3243 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3244 // remove closing `)` from the span
3245 let sugg_span = sugg_span.shrink_to_lo();
3246 err.span_suggestion(
3248 "expected the unit value `()`; create it with empty parentheses",
3250 Applicability::MachineApplicable);
3252 err.span_label(sp, format!("expected {}{}",
3253 if c_variadic { "at least " } else { "" },
3254 potentially_plural_count(expected_count, "parameter")));
3259 let mut expected_arg_tys = expected_arg_tys.to_vec();
3261 let formal_tys = if tuple_arguments == TupleArguments {
3262 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3263 match tuple_type.sty {
3264 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3265 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3266 expected_arg_tys = vec![];
3267 self.err_args(args.len())
3269 ty::Tuple(arg_types) => {
3270 expected_arg_tys = match expected_arg_tys.get(0) {
3271 Some(&ty) => match ty.sty {
3272 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3277 arg_types.iter().map(|k| k.expect_ty()).collect()
3280 span_err!(tcx.sess, sp, E0059,
3281 "cannot use call notation; the first type parameter \
3282 for the function trait is neither a tuple nor unit");
3283 expected_arg_tys = vec![];
3284 self.err_args(args.len())
3287 } else if expected_arg_count == supplied_arg_count {
3289 } else if c_variadic {
3290 if supplied_arg_count >= expected_arg_count {
3293 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3294 expected_arg_tys = vec![];
3295 self.err_args(supplied_arg_count)
3298 // is the missing argument of type `()`?
3299 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3300 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3301 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3302 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3306 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3308 expected_arg_tys = vec![];
3309 self.err_args(supplied_arg_count)
3312 debug!("check_argument_types: formal_tys={:?}",
3313 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3315 // If there is no expectation, expect formal_tys.
3316 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3322 let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
3324 // Check the arguments.
3325 // We do this in a pretty awful way: first we type-check any arguments
3326 // that are not closures, then we type-check the closures. This is so
3327 // that we have more information about the types of arguments when we
3328 // type-check the functions. This isn't really the right way to do this.
3329 for &check_closures in &[false, true] {
3330 debug!("check_closures={}", check_closures);
3332 // More awful hacks: before we check argument types, try to do
3333 // an "opportunistic" vtable resolution of any trait bounds on
3334 // the call. This helps coercions.
3336 self.select_obligations_where_possible(false, |errors| {
3337 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
3338 self.point_at_arg_instead_of_call_if_possible(
3340 &final_arg_types[..],
3347 // For C-variadic functions, we don't have a declared type for all of
3348 // the arguments hence we only do our usual type checking with
3349 // the arguments who's types we do know.
3350 let t = if c_variadic {
3352 } else if tuple_arguments == TupleArguments {
3357 for (i, arg) in args.iter().take(t).enumerate() {
3358 // Warn only for the first loop (the "no closures" one).
3359 // Closure arguments themselves can't be diverging, but
3360 // a previous argument can, e.g., `foo(panic!(), || {})`.
3361 if !check_closures {
3362 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3365 let is_closure = match arg.node {
3366 ExprKind::Closure(..) => true,
3370 if is_closure != check_closures {
3374 debug!("checking the argument");
3375 let formal_ty = formal_tys[i];
3377 // The special-cased logic below has three functions:
3378 // 1. Provide as good of an expected type as possible.
3379 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3381 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3383 // 2. Coerce to the most detailed type that could be coerced
3384 // to, which is `expected_ty` if `rvalue_hint` returns an
3385 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3386 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3387 // We're processing function arguments so we definitely want to use
3388 // two-phase borrows.
3389 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3390 final_arg_types.push((i, coerce_ty));
3392 // 3. Relate the expected type and the formal one,
3393 // if the expected type was used for the coercion.
3394 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3398 // We also need to make sure we at least write the ty of the other
3399 // arguments which we skipped above.
3401 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3402 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3403 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3406 for arg in args.iter().skip(expected_arg_count) {
3407 let arg_ty = self.check_expr(&arg);
3409 // There are a few types which get autopromoted when passed via varargs
3410 // in C but we just error out instead and require explicit casts.
3411 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3413 ty::Float(ast::FloatTy::F32) => {
3414 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3416 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3417 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3419 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3420 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3423 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3424 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3425 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3433 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3434 vec![self.tcx.types.err; len]
3437 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
3438 /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
3439 /// reference a type argument. If they do, and there's only *one* argument that does, we point
3440 /// at the corresponding argument's expression span instead of the `fn` call path span.
3441 fn point_at_arg_instead_of_call_if_possible(
3443 errors: &mut Vec<traits::FulfillmentError<'_>>,
3444 final_arg_types: &[(usize, Ty<'tcx>)],
3446 args: &'tcx [hir::Expr],
3448 if !call_sp.desugaring_kind().is_some() {
3449 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3450 // the `?` operator.
3451 for error in errors {
3452 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3453 // Collect the argument position for all arguments that could have caused this
3454 // `FullfillmentError`.
3455 let mut referenced_in = final_arg_types.iter()
3456 .flat_map(|(i, ty)| {
3457 let ty = self.resolve_vars_if_possible(ty);
3458 // We walk the argument type because the argument's type could have
3459 // been `Option<T>`, but the `FullfillmentError` references `T`.
3461 .filter(|&ty| ty == predicate.skip_binder().self_ty())
3464 if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
3465 // We make sure that only *one* argument matches the obligation failure
3466 // and thet the obligation's span to its expression's.
3467 error.obligation.cause.span = args[ref_in].span;
3468 error.points_at_arg_span = true;
3475 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call expression, we walk the
3476 /// `PathSegment`s and resolve their type parameters to see if any of the `FullfillmentError`s
3477 /// were caused by them. If they were, we point at the corresponding type argument's span
3478 /// instead of the `fn` call path span.
3479 fn point_at_type_arg_instead_of_call_if_possible(
3481 errors: &mut Vec<traits::FulfillmentError<'_>>,
3482 call_expr: &'tcx hir::Expr,
3484 if let hir::ExprKind::Call(path, _) = &call_expr.node {
3485 if let hir::ExprKind::Path(qpath) = &path.node {
3486 if let hir::QPath::Resolved(_, path) = &qpath {
3487 for error in errors {
3488 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3489 // If any of the type arguments in this path segment caused the
3490 // `FullfillmentError`, point at its span (#61860).
3491 for arg in path.segments.iter()
3492 .filter_map(|seg| seg.args.as_ref())
3493 .flat_map(|a| a.args.iter())
3495 if let hir::GenericArg::Type(hir_ty) = &arg {
3496 if let hir::TyKind::Path(
3497 hir::QPath::TypeRelative(..),
3499 // Avoid ICE with associated types. As this is best
3500 // effort only, it's ok to ignore the case. It
3501 // would trigger in `is_send::<T::AssocType>();`
3502 // from `typeck-default-trait-impl-assoc-type.rs`.
3504 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
3505 let ty = self.resolve_vars_if_possible(&ty);
3506 if ty == predicate.skip_binder().self_ty() {
3507 error.obligation.cause.span = hir_ty.span;
3519 // AST fragment checking
3522 expected: Expectation<'tcx>)
3528 ast::LitKind::Str(..) => tcx.mk_static_str(),
3529 ast::LitKind::ByteStr(ref v) => {
3530 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3531 tcx.mk_array(tcx.types.u8, v.len() as u64))
3533 ast::LitKind::Byte(_) => tcx.types.u8,
3534 ast::LitKind::Char(_) => tcx.types.char,
3535 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3536 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3537 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3538 let opt_ty = expected.to_option(self).and_then(|ty| {
3540 ty::Int(_) | ty::Uint(_) => Some(ty),
3541 ty::Char => Some(tcx.types.u8),
3542 ty::RawPtr(..) => Some(tcx.types.usize),
3543 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3547 opt_ty.unwrap_or_else(|| self.next_int_var())
3549 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3550 ast::LitKind::FloatUnsuffixed(_) => {
3551 let opt_ty = expected.to_option(self).and_then(|ty| {
3553 ty::Float(_) => Some(ty),
3557 opt_ty.unwrap_or_else(|| self.next_float_var())
3559 ast::LitKind::Bool(_) => tcx.types.bool,
3560 ast::LitKind::Err(_) => tcx.types.err,
3564 // Determine the `Self` type, using fresh variables for all variables
3565 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3566 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3568 pub fn impl_self_ty(&self,
3569 span: Span, // (potential) receiver for this impl
3571 -> TypeAndSubsts<'tcx> {
3572 let ity = self.tcx.type_of(did);
3573 debug!("impl_self_ty: ity={:?}", ity);
3575 let substs = self.fresh_substs_for_item(span, did);
3576 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3578 TypeAndSubsts { substs: substs, ty: substd_ty }
3581 /// Unifies the output type with the expected type early, for more coercions
3582 /// and forward type information on the input expressions.
3583 fn expected_inputs_for_expected_output(&self,
3585 expected_ret: Expectation<'tcx>,
3586 formal_ret: Ty<'tcx>,
3587 formal_args: &[Ty<'tcx>])
3589 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3590 let ret_ty = match expected_ret.only_has_type(self) {
3592 None => return Vec::new()
3594 let expect_args = self.fudge_inference_if_ok(|| {
3595 // Attempt to apply a subtyping relationship between the formal
3596 // return type (likely containing type variables if the function
3597 // is polymorphic) and the expected return type.
3598 // No argument expectations are produced if unification fails.
3599 let origin = self.misc(call_span);
3600 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3602 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3603 // to identity so the resulting type is not constrained.
3606 // Process any obligations locally as much as
3607 // we can. We don't care if some things turn
3608 // out unconstrained or ambiguous, as we're
3609 // just trying to get hints here.
3610 self.save_and_restore_in_snapshot_flag(|_| {
3611 let mut fulfill = TraitEngine::new(self.tcx);
3612 for obligation in ok.obligations {
3613 fulfill.register_predicate_obligation(self, obligation);
3615 fulfill.select_where_possible(self)
3616 }).map_err(|_| ())?;
3618 Err(_) => return Err(()),
3621 // Record all the argument types, with the substitutions
3622 // produced from the above subtyping unification.
3623 Ok(formal_args.iter().map(|ty| {
3624 self.resolve_vars_if_possible(ty)
3626 }).unwrap_or_default();
3627 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3628 formal_args, formal_ret,
3629 expect_args, expected_ret);
3633 pub fn check_struct_path(&self,
3636 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3637 let path_span = match *qpath {
3638 QPath::Resolved(_, ref path) => path.span,
3639 QPath::TypeRelative(ref qself, _) => qself.span
3641 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3642 let variant = match def {
3644 self.set_tainted_by_errors();
3647 Res::Def(DefKind::Variant, _) => {
3649 ty::Adt(adt, substs) => {
3650 Some((adt.variant_of_res(def), adt.did, substs))
3652 _ => bug!("unexpected type: {:?}", ty)
3655 Res::Def(DefKind::Struct, _)
3656 | Res::Def(DefKind::Union, _)
3657 | Res::Def(DefKind::TyAlias, _)
3658 | Res::Def(DefKind::AssocTy, _)
3659 | Res::SelfTy(..) => {
3661 ty::Adt(adt, substs) if !adt.is_enum() => {
3662 Some((adt.non_enum_variant(), adt.did, substs))
3667 _ => bug!("unexpected definition: {:?}", def)
3670 if let Some((variant, did, substs)) = variant {
3671 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3672 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3674 // Check bounds on type arguments used in the path.
3675 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
3676 let cause = traits::ObligationCause::new(
3679 traits::ItemObligation(did),
3681 self.add_obligations_for_parameters(cause, &bounds);
3685 struct_span_err!(self.tcx.sess, path_span, E0071,
3686 "expected struct, variant or union type, found {}",
3687 ty.sort_string(self.tcx))
3688 .span_label(path_span, "not a struct")
3694 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3695 // The newly resolved definition is written into `type_dependent_defs`.
3696 fn finish_resolving_struct_path(&self,
3703 QPath::Resolved(ref maybe_qself, ref path) => {
3704 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3705 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3708 QPath::TypeRelative(ref qself, ref segment) => {
3709 let ty = self.to_ty(qself);
3711 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.node {
3716 let result = AstConv::associated_path_to_ty(
3725 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3726 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3728 // Write back the new resolution.
3729 self.write_resolution(hir_id, result);
3731 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3736 /// Resolves an associated value path into a base type and associated constant, or method
3737 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3738 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3742 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3744 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3745 let (ty, qself, item_segment) = match *qpath {
3746 QPath::Resolved(ref opt_qself, ref path) => {
3748 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3749 &path.segments[..]);
3751 QPath::TypeRelative(ref qself, ref segment) => {
3752 (self.to_ty(qself), qself, segment)
3755 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3756 // Return directly on cache hit. This is useful to avoid doubly reporting
3757 // errors with default match binding modes. See #44614.
3758 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3759 .unwrap_or(Res::Err);
3760 return (def, Some(ty), slice::from_ref(&**item_segment));
3762 let item_name = item_segment.ident;
3763 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3764 let result = match error {
3765 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3766 _ => Err(ErrorReported),
3768 if item_name.name != kw::Invalid {
3769 self.report_method_error(
3773 SelfSource::QPath(qself),
3776 ).map(|mut e| e.emit());
3781 // Write back the new resolution.
3782 self.write_resolution(hir_id, result);
3784 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3786 slice::from_ref(&**item_segment),
3790 pub fn check_decl_initializer(
3792 local: &'tcx hir::Local,
3793 init: &'tcx hir::Expr,
3795 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3796 // for #42640 (default match binding modes).
3799 let ref_bindings = local.pat.contains_explicit_ref_binding();
3801 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3802 if let Some(m) = ref_bindings {
3803 // Somewhat subtle: if we have a `ref` binding in the pattern,
3804 // we want to avoid introducing coercions for the RHS. This is
3805 // both because it helps preserve sanity and, in the case of
3806 // ref mut, for soundness (issue #23116). In particular, in
3807 // the latter case, we need to be clear that the type of the
3808 // referent for the reference that results is *equal to* the
3809 // type of the place it is referencing, and not some
3810 // supertype thereof.
3811 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3812 self.demand_eqtype(init.span, local_ty, init_ty);
3815 self.check_expr_coercable_to_type(init, local_ty)
3819 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3820 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3821 self.write_ty(local.hir_id, t);
3823 if let Some(ref init) = local.init {
3824 let init_ty = self.check_decl_initializer(local, &init);
3825 if init_ty.references_error() {
3826 self.write_ty(local.hir_id, init_ty);
3830 self.check_pat_top(&local.pat, t, None);
3831 let pat_ty = self.node_ty(local.pat.hir_id);
3832 if pat_ty.references_error() {
3833 self.write_ty(local.hir_id, pat_ty);
3837 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3838 // Don't do all the complex logic below for `DeclItem`.
3840 hir::StmtKind::Item(..) => return,
3841 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3844 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3846 // Hide the outer diverging and `has_errors` flags.
3847 let old_diverges = self.diverges.get();
3848 let old_has_errors = self.has_errors.get();
3849 self.diverges.set(Diverges::Maybe);
3850 self.has_errors.set(false);
3853 hir::StmtKind::Local(ref l) => {
3854 self.check_decl_local(&l);
3857 hir::StmtKind::Item(_) => {}
3858 hir::StmtKind::Expr(ref expr) => {
3859 // Check with expected type of `()`.
3860 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit());
3862 hir::StmtKind::Semi(ref expr) => {
3863 self.check_expr(&expr);
3867 // Combine the diverging and `has_error` flags.
3868 self.diverges.set(self.diverges.get() | old_diverges);
3869 self.has_errors.set(self.has_errors.get() | old_has_errors);
3872 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
3873 let unit = self.tcx.mk_unit();
3874 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
3876 // if the block produces a `!` value, that can always be
3877 // (effectively) coerced to unit.
3879 self.demand_suptype(blk.span, unit, ty);
3883 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
3884 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
3885 /// when given code like the following:
3887 /// if false { return 0i32; } else { 1u32 }
3888 /// // ^^^^ point at this instead of the whole `if` expression
3890 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
3891 if let hir::ExprKind::Match(_, arms, _) = &expr.node {
3892 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
3893 self.in_progress_tables
3894 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
3895 .and_then(|arm_ty| {
3896 if arm_ty.is_never() {
3899 Some(match &arm.body.node {
3900 // Point at the tail expression when possible.
3901 hir::ExprKind::Block(block, _) => block.expr
3904 .unwrap_or(block.span),
3910 if arm_spans.len() == 1 {
3911 return arm_spans[0];
3917 fn check_block_with_expected(
3919 blk: &'tcx hir::Block,
3920 expected: Expectation<'tcx>,
3923 let mut fcx_ps = self.ps.borrow_mut();
3924 let unsafety_state = fcx_ps.recurse(blk);
3925 replace(&mut *fcx_ps, unsafety_state)
3928 // In some cases, blocks have just one exit, but other blocks
3929 // can be targeted by multiple breaks. This can happen both
3930 // with labeled blocks as well as when we desugar
3931 // a `try { ... }` expression.
3935 // 'a: { if true { break 'a Err(()); } Ok(()) }
3937 // Here we would wind up with two coercions, one from
3938 // `Err(())` and the other from the tail expression
3939 // `Ok(())`. If the tail expression is omitted, that's a
3940 // "forced unit" -- unless the block diverges, in which
3941 // case we can ignore the tail expression (e.g., `'a: {
3942 // break 'a 22; }` would not force the type of the block
3944 let tail_expr = blk.expr.as_ref();
3945 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
3946 let coerce = if blk.targeted_by_break {
3947 CoerceMany::new(coerce_to_ty)
3949 let tail_expr: &[P<hir::Expr>] = match tail_expr {
3950 Some(e) => slice::from_ref(e),
3953 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
3956 let prev_diverges = self.diverges.get();
3957 let ctxt = BreakableCtxt {
3958 coerce: Some(coerce),
3962 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
3963 for s in &blk.stmts {
3967 // check the tail expression **without** holding the
3968 // `enclosing_breakables` lock below.
3969 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
3971 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
3972 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
3973 let coerce = ctxt.coerce.as_mut().unwrap();
3974 if let Some(tail_expr_ty) = tail_expr_ty {
3975 let tail_expr = tail_expr.unwrap();
3976 let span = self.get_expr_coercion_span(tail_expr);
3977 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
3978 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
3980 // Subtle: if there is no explicit tail expression,
3981 // that is typically equivalent to a tail expression
3982 // of `()` -- except if the block diverges. In that
3983 // case, there is no value supplied from the tail
3984 // expression (assuming there are no other breaks,
3985 // this implies that the type of the block will be
3988 // #41425 -- label the implicit `()` as being the
3989 // "found type" here, rather than the "expected type".
3990 if !self.diverges.get().is_always() {
3991 // #50009 -- Do not point at the entire fn block span, point at the return type
3992 // span, as it is the cause of the requirement, and
3993 // `consider_hint_about_removing_semicolon` will point at the last expression
3994 // if it were a relevant part of the error. This improves usability in editors
3995 // that highlight errors inline.
3996 let mut sp = blk.span;
3997 let mut fn_span = None;
3998 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
3999 let ret_sp = decl.output.span();
4000 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4001 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4002 // output would otherwise be incorrect and even misleading. Make sure
4003 // the span we're aiming at correspond to a `fn` body.
4004 if block_sp == blk.span {
4006 fn_span = Some(ident.span);
4010 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4011 if let Some(expected_ty) = expected.only_has_type(self) {
4012 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4014 if let Some(fn_span) = fn_span {
4017 "implicitly returns `()` as its body has no tail or `return` \
4027 // If we can break from the block, then the block's exit is always reachable
4028 // (... as long as the entry is reachable) - regardless of the tail of the block.
4029 self.diverges.set(prev_diverges);
4032 let mut ty = ctxt.coerce.unwrap().complete(self);
4034 if self.has_errors.get() || ty.references_error() {
4035 ty = self.tcx.types.err
4038 self.write_ty(blk.hir_id, ty);
4040 *self.ps.borrow_mut() = prev;
4044 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4045 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4047 Node::Item(&hir::Item {
4048 node: hir::ItemKind::Fn(_, _, _, body_id), ..
4050 Node::ImplItem(&hir::ImplItem {
4051 node: hir::ImplItemKind::Method(_, body_id), ..
4053 let body = self.tcx.hir().body(body_id);
4054 if let ExprKind::Block(block, _) = &body.value.node {
4055 return Some(block.span);
4063 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4064 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
4065 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4066 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4069 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4070 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
4072 Node::Item(&hir::Item {
4073 ident, node: hir::ItemKind::Fn(ref decl, ..), ..
4075 // This is less than ideal, it will not suggest a return type span on any
4076 // method called `main`, regardless of whether it is actually the entry point,
4077 // but it will still present it as the reason for the expected type.
4078 Some((decl, ident, ident.name != sym::main))
4080 Node::TraitItem(&hir::TraitItem {
4081 ident, node: hir::TraitItemKind::Method(hir::MethodSig {
4084 }) => Some((decl, ident, true)),
4085 Node::ImplItem(&hir::ImplItem {
4086 ident, node: hir::ImplItemKind::Method(hir::MethodSig {
4089 }) => Some((decl, ident, false)),
4094 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4095 /// suggestion can be made, `None` otherwise.
4096 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
4097 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4098 // `while` before reaching it, as block tail returns are not available in them.
4099 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4100 let parent = self.tcx.hir().get(blk_id);
4101 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4105 /// On implicit return expressions with mismatched types, provides the following suggestions:
4107 /// - Points out the method's return type as the reason for the expected type.
4108 /// - Possible missing semicolon.
4109 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4110 pub fn suggest_mismatched_types_on_tail(
4112 err: &mut DiagnosticBuilder<'tcx>,
4113 expression: &'tcx hir::Expr,
4119 self.suggest_missing_semicolon(err, expression, expected, cause_span);
4120 let mut pointing_at_return_type = false;
4121 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4122 pointing_at_return_type = self.suggest_missing_return_type(
4123 err, &fn_decl, expected, found, can_suggest);
4125 self.suggest_ref_or_into(err, expression, expected, found);
4126 self.suggest_boxing_when_appropriate(err, expression, expected, found);
4127 pointing_at_return_type
4130 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4131 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4133 /// fn foo(x: usize) -> usize { x }
4134 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4138 err: &mut DiagnosticBuilder<'tcx>,
4143 let hir = self.tcx.hir();
4144 let (def_id, sig) = match found.sty {
4145 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4146 ty::Closure(def_id, substs) => {
4147 // We don't use `closure_sig` to account for malformed closures like
4148 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4149 let closure_sig_ty = substs.closure_sig_ty(def_id, self.tcx);
4150 (def_id, match closure_sig_ty.sty {
4151 ty::FnPtr(sig) => sig,
4159 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4161 let sig = self.normalize_associated_types_in(expr.span, &sig);
4162 if self.can_coerce(sig.output(), expected) {
4163 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4164 (String::new(), Applicability::MachineApplicable)
4166 ("...".to_string(), Applicability::HasPlaceholders)
4168 let mut msg = "call this function";
4169 match hir.get_if_local(def_id) {
4170 Some(Node::Item(hir::Item {
4171 node: ItemKind::Fn(.., body_id),
4174 Some(Node::ImplItem(hir::ImplItem {
4175 node: hir::ImplItemKind::Method(_, body_id),
4178 Some(Node::TraitItem(hir::TraitItem {
4179 node: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4182 let body = hir.body(*body_id);
4183 sugg_call = body.params.iter()
4184 .map(|param| match ¶m.pat.node {
4185 hir::PatKind::Binding(_, _, ident, None)
4186 if ident.name != kw::SelfLower => ident.to_string(),
4187 _ => "_".to_string(),
4188 }).collect::<Vec<_>>().join(", ");
4190 Some(Node::Expr(hir::Expr {
4191 node: ExprKind::Closure(_, _, body_id, closure_span, _),
4192 span: full_closure_span,
4195 if *full_closure_span == expr.span {
4198 err.span_label(*closure_span, "closure defined here");
4199 msg = "call this closure";
4200 let body = hir.body(*body_id);
4201 sugg_call = body.params.iter()
4202 .map(|param| match ¶m.pat.node {
4203 hir::PatKind::Binding(_, _, ident, None)
4204 if ident.name != kw::SelfLower => ident.to_string(),
4205 _ => "_".to_string(),
4206 }).collect::<Vec<_>>().join(", ");
4208 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4209 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4210 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4211 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4212 msg = "instantiate this tuple variant";
4214 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4215 msg = "instantiate this tuple struct";
4220 Some(Node::ForeignItem(hir::ForeignItem {
4221 node: hir::ForeignItemKind::Fn(_, idents, _),
4224 Some(Node::TraitItem(hir::TraitItem {
4225 node: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4227 })) => sugg_call = idents.iter()
4228 .map(|ident| if ident.name != kw::SelfLower {
4232 }).collect::<Vec<_>>()
4236 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4237 err.span_suggestion(
4239 &format!("use parentheses to {}", msg),
4240 format!("{}({})", code, sugg_call),
4249 pub fn suggest_ref_or_into(
4251 err: &mut DiagnosticBuilder<'tcx>,
4256 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4257 err.span_suggestion(
4261 Applicability::MachineApplicable,
4263 } else if let (ty::FnDef(def_id, ..), true) = (
4265 self.suggest_fn_call(err, expr, expected, found),
4267 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4268 let sp = self.sess().source_map().def_span(sp);
4269 err.span_label(sp, &format!("{} defined here", found));
4271 } else if !self.check_for_cast(err, expr, found, expected) {
4272 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4276 let methods = self.get_conversion_methods(expr.span, expected, found);
4277 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4278 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4279 .filter_map(|(receiver, method)| {
4280 let method_call = format!(".{}()", method.ident);
4281 if receiver.ends_with(&method_call) {
4282 None // do not suggest code that is already there (#53348)
4284 let method_call_list = [".to_vec()", ".to_string()"];
4285 let sugg = if receiver.ends_with(".clone()")
4286 && method_call_list.contains(&method_call.as_str()) {
4287 let max_len = receiver.rfind(".").unwrap();
4288 format!("{}{}", &receiver[..max_len], method_call)
4290 format!("{}{}", receiver, method_call)
4292 Some(if is_struct_pat_shorthand_field {
4293 format!("{}: {}", receiver, sugg)
4299 if suggestions.peek().is_some() {
4300 err.span_suggestions(
4302 "try using a conversion method",
4304 Applicability::MaybeIncorrect,
4311 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4312 /// in the heap by calling `Box::new()`.
4313 fn suggest_boxing_when_appropriate(
4315 err: &mut DiagnosticBuilder<'tcx>,
4320 if self.tcx.hir().is_const_context(expr.hir_id) {
4321 // Do not suggest `Box::new` in const context.
4324 if !expected.is_box() || found.is_box() {
4327 let boxed_found = self.tcx.mk_box(found);
4328 if let (true, Ok(snippet)) = (
4329 self.can_coerce(boxed_found, expected),
4330 self.sess().source_map().span_to_snippet(expr.span),
4332 err.span_suggestion(
4334 "store this in the heap by calling `Box::new`",
4335 format!("Box::new({})", snippet),
4336 Applicability::MachineApplicable,
4338 err.note("for more on the distinction between the stack and the \
4339 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4340 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4341 https://doc.rust-lang.org/std/boxed/index.html");
4346 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4350 /// bar_that_returns_u32()
4354 /// This routine checks if the return expression in a block would make sense on its own as a
4355 /// statement and the return type has been left as default or has been specified as `()`. If so,
4356 /// it suggests adding a semicolon.
4357 fn suggest_missing_semicolon(
4359 err: &mut DiagnosticBuilder<'tcx>,
4360 expression: &'tcx hir::Expr,
4364 if expected.is_unit() {
4365 // `BlockTailExpression` only relevant if the tail expr would be
4366 // useful on its own.
4367 match expression.node {
4368 ExprKind::Call(..) |
4369 ExprKind::MethodCall(..) |
4370 ExprKind::Loop(..) |
4371 ExprKind::Match(..) |
4372 ExprKind::Block(..) => {
4373 let sp = self.tcx.sess.source_map().next_point(cause_span);
4374 err.span_suggestion(
4376 "try adding a semicolon",
4378 Applicability::MachineApplicable);
4385 /// A possible error is to forget to add a return type that is needed:
4389 /// bar_that_returns_u32()
4393 /// This routine checks if the return type is left as default, the method is not part of an
4394 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4396 fn suggest_missing_return_type(
4398 err: &mut DiagnosticBuilder<'tcx>,
4399 fn_decl: &hir::FnDecl,
4404 // Only suggest changing the return type for methods that
4405 // haven't set a return type at all (and aren't `fn main()` or an impl).
4406 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4407 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4408 err.span_suggestion(
4410 "try adding a return type",
4411 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
4412 Applicability::MachineApplicable);
4415 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4416 err.span_label(span, "possibly return type missing here?");
4419 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4420 // `fn main()` must return `()`, do not suggest changing return type
4421 err.span_label(span, "expected `()` because of default return type");
4424 // expectation was caused by something else, not the default return
4425 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4426 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4427 // Only point to return type if the expected type is the return type, as if they
4428 // are not, the expectation must have been caused by something else.
4429 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.node);
4431 let ty = AstConv::ast_ty_to_ty(self, ty);
4432 debug!("suggest_missing_return_type: return type {:?}", ty);
4433 debug!("suggest_missing_return_type: expected type {:?}", ty);
4434 if ty.sty == expected.sty {
4435 err.span_label(sp, format!("expected `{}` because of return type",
4444 /// A possible error is to forget to add `.await` when using futures:
4447 /// async fn make_u32() -> u32 {
4451 /// fn take_u32(x: u32) {}
4453 /// async fn foo() {
4454 /// let x = make_u32();
4459 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4460 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4461 /// `.await` to the tail of the expression.
4462 fn suggest_missing_await(
4464 err: &mut DiagnosticBuilder<'tcx>,
4469 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4470 // body isn't `async`.
4471 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4472 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4473 let body = self.tcx().hir().body(body_id);
4474 if let Some(hir::GeneratorKind::Async) = body.generator_kind {
4476 // Check for `Future` implementations by constructing a predicate to
4477 // prove: `<T as Future>::Output == U`
4478 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4479 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4480 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4481 // `<T as Future>::Output`
4482 projection_ty: ty::ProjectionTy {
4484 substs: self.tcx.mk_substs_trait(
4486 self.fresh_substs_for_item(sp, item_def_id)
4493 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4494 if self.infcx.predicate_may_hold(&obligation) {
4495 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4496 err.span_suggestion(
4498 "consider using `.await` here",
4499 format!("{}.await", code),
4500 Applicability::MaybeIncorrect,
4508 /// A common error is to add an extra semicolon:
4511 /// fn foo() -> usize {
4516 /// This routine checks if the final statement in a block is an
4517 /// expression with an explicit semicolon whose type is compatible
4518 /// with `expected_ty`. If so, it suggests removing the semicolon.
4519 fn consider_hint_about_removing_semicolon(
4521 blk: &'tcx hir::Block,
4522 expected_ty: Ty<'tcx>,
4523 err: &mut DiagnosticBuilder<'_>,
4525 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4526 err.span_suggestion(
4528 "consider removing this semicolon",
4530 Applicability::MachineApplicable,
4535 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4536 // Be helpful when the user wrote `{... expr;}` and
4537 // taking the `;` off is enough to fix the error.
4538 let last_stmt = blk.stmts.last()?;
4539 let last_expr = match last_stmt.node {
4540 hir::StmtKind::Semi(ref e) => e,
4543 let last_expr_ty = self.node_ty(last_expr.hir_id);
4544 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4547 let original_span = original_sp(last_stmt.span, blk.span);
4548 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4551 // Instantiates the given path, which must refer to an item with the given
4552 // number of type parameters and type.
4553 pub fn instantiate_value_path(&self,
4554 segments: &[hir::PathSegment],
4555 self_ty: Option<Ty<'tcx>>,
4559 -> (Ty<'tcx>, Res) {
4561 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4570 let path_segs = match res {
4571 Res::Local(_) | Res::SelfCtor(_) => vec![],
4572 Res::Def(kind, def_id) =>
4573 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4574 _ => bug!("instantiate_value_path on {:?}", res),
4577 let mut user_self_ty = None;
4578 let mut is_alias_variant_ctor = false;
4580 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4581 if let Some(self_ty) = self_ty {
4582 let adt_def = self_ty.ty_adt_def().unwrap();
4583 user_self_ty = Some(UserSelfTy {
4584 impl_def_id: adt_def.did,
4587 is_alias_variant_ctor = true;
4590 Res::Def(DefKind::Method, def_id)
4591 | Res::Def(DefKind::AssocConst, def_id) => {
4592 let container = tcx.associated_item(def_id).container;
4593 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4595 ty::TraitContainer(trait_did) => {
4596 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4598 ty::ImplContainer(impl_def_id) => {
4599 if segments.len() == 1 {
4600 // `<T>::assoc` will end up here, and so
4601 // can `T::assoc`. It this came from an
4602 // inherent impl, we need to record the
4603 // `T` for posterity (see `UserSelfTy` for
4605 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4606 user_self_ty = Some(UserSelfTy {
4617 // Now that we have categorized what space the parameters for each
4618 // segment belong to, let's sort out the parameters that the user
4619 // provided (if any) into their appropriate spaces. We'll also report
4620 // errors if type parameters are provided in an inappropriate place.
4622 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4623 let generics_has_err = AstConv::prohibit_generics(
4624 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4625 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4632 if let Res::Local(hid) = res {
4633 let ty = self.local_ty(span, hid).decl_ty;
4634 let ty = self.normalize_associated_types_in(span, &ty);
4635 self.write_ty(hir_id, ty);
4639 if generics_has_err {
4640 // Don't try to infer type parameters when prohibited generic arguments were given.
4641 user_self_ty = None;
4644 // Now we have to compare the types that the user *actually*
4645 // provided against the types that were *expected*. If the user
4646 // did not provide any types, then we want to substitute inference
4647 // variables. If the user provided some types, we may still need
4648 // to add defaults. If the user provided *too many* types, that's
4651 let mut infer_args_for_err = FxHashSet::default();
4652 for &PathSeg(def_id, index) in &path_segs {
4653 let seg = &segments[index];
4654 let generics = tcx.generics_of(def_id);
4655 // Argument-position `impl Trait` is treated as a normal generic
4656 // parameter internally, but we don't allow users to specify the
4657 // parameter's value explicitly, so we have to do some error-
4659 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4664 false, // `is_method_call`
4666 if suppress_errors {
4667 infer_args_for_err.insert(index);
4668 self.set_tainted_by_errors(); // See issue #53251.
4672 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4673 tcx.generics_of(*def_id).has_self
4674 }).unwrap_or(false);
4676 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4677 let ty = self.impl_self_ty(span, impl_def_id).ty;
4678 let adt_def = ty.ty_adt_def();
4681 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4682 let variant = adt_def.non_enum_variant();
4683 let ctor_def_id = variant.ctor_def_id.unwrap();
4685 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4690 let mut err = tcx.sess.struct_span_err(span,
4691 "the `Self` constructor can only be used with tuple or unit structs");
4692 if let Some(adt_def) = adt_def {
4693 match adt_def.adt_kind() {
4695 err.help("did you mean to use one of the enum's variants?");
4699 err.span_suggestion(
4701 "use curly brackets",
4702 String::from("Self { /* fields */ }"),
4703 Applicability::HasPlaceholders,
4710 return (tcx.types.err, res)
4716 let def_id = res.def_id();
4718 // The things we are substituting into the type should not contain
4719 // escaping late-bound regions, and nor should the base type scheme.
4720 let ty = tcx.type_of(def_id);
4722 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4728 // Provide the generic args, and whether types should be inferred.
4730 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4733 // If we've encountered an `impl Trait`-related error, we're just
4734 // going to infer the arguments for better error messages.
4735 if !infer_args_for_err.contains(&index) {
4736 // Check whether the user has provided generic arguments.
4737 if let Some(ref data) = segments[index].args {
4738 return (Some(data), segments[index].infer_args);
4741 return (None, segments[index].infer_args);
4746 // Provide substitutions for parameters for which (valid) arguments have been provided.
4748 match (¶m.kind, arg) {
4749 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4750 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4752 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4753 self.to_ty(ty).into()
4755 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4756 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4758 _ => unreachable!(),
4761 // Provide substitutions for parameters for which arguments are inferred.
4762 |substs, param, infer_args| {
4764 GenericParamDefKind::Lifetime => {
4765 self.re_infer(Some(param), span).unwrap().into()
4767 GenericParamDefKind::Type { has_default, .. } => {
4768 if !infer_args && has_default {
4769 // If we have a default, then we it doesn't matter that we're not
4770 // inferring the type arguments: we provide the default where any
4772 let default = tcx.type_of(param.def_id);
4775 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4778 // If no type arguments were provided, we have to infer them.
4779 // This case also occurs as a result of some malformed input, e.g.
4780 // a lifetime argument being given instead of a type parameter.
4781 // Using inference instead of `Error` gives better error messages.
4782 self.var_for_def(span, param)
4785 GenericParamDefKind::Const => {
4786 // FIXME(const_generics:defaults)
4787 // No const parameters were provided, we have to infer them.
4788 self.var_for_def(span, param)
4793 assert!(!substs.has_escaping_bound_vars());
4794 assert!(!ty.has_escaping_bound_vars());
4796 // First, store the "user substs" for later.
4797 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4799 self.add_required_obligations(span, def_id, &substs);
4801 // Substitute the values for the type parameters into the type of
4802 // the referenced item.
4803 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4805 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4806 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4807 // is inherent, there is no `Self` parameter; instead, the impl needs
4808 // type parameters, which we can infer by unifying the provided `Self`
4809 // with the substituted impl type.
4810 // This also occurs for an enum variant on a type alias.
4811 let ty = tcx.type_of(impl_def_id);
4813 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4814 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4815 Ok(ok) => self.register_infer_ok_obligations(ok),
4817 self.tcx.sess.delay_span_bug(span, &format!(
4818 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4826 self.check_rustc_args_require_const(def_id, hir_id, span);
4828 debug!("instantiate_value_path: type of {:?} is {:?}",
4831 self.write_substs(hir_id, substs);
4833 (ty_substituted, res)
4836 /// Add all the obligations that are required, substituting and normalized appropriately.
4837 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
4838 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
4840 for (i, mut obligation) in traits::predicates_for_generics(
4841 traits::ObligationCause::new(
4844 traits::ItemObligation(def_id),
4848 ).into_iter().enumerate() {
4849 // This makes the error point at the bound, but we want to point at the argument
4850 if let Some(span) = spans.get(i) {
4851 obligation.cause.code = traits::BindingObligation(def_id, *span);
4853 self.register_predicate(obligation);
4857 fn check_rustc_args_require_const(&self,
4861 // We're only interested in functions tagged with
4862 // #[rustc_args_required_const], so ignore anything that's not.
4863 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
4867 // If our calling expression is indeed the function itself, we're good!
4868 // If not, generate an error that this can only be called directly.
4869 if let Node::Expr(expr) = self.tcx.hir().get(
4870 self.tcx.hir().get_parent_node(hir_id))
4872 if let ExprKind::Call(ref callee, ..) = expr.node {
4873 if callee.hir_id == hir_id {
4879 self.tcx.sess.span_err(span, "this function can only be invoked \
4880 directly, not through a function pointer");
4883 // Resolves `typ` by a single level if `typ` is a type variable.
4884 // If no resolution is possible, then an error is reported.
4885 // Numeric inference variables may be left unresolved.
4886 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4887 let ty = self.resolve_type_vars_with_obligations(ty);
4888 if !ty.is_ty_var() {
4891 if !self.is_tainted_by_errors() {
4892 self.need_type_info_err((**self).body_id, sp, ty)
4893 .note("type must be known at this point")
4896 self.demand_suptype(sp, self.tcx.types.err, ty);
4901 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
4904 ctxt: BreakableCtxt<'tcx>,
4906 ) -> (BreakableCtxt<'tcx>, R) {
4909 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4910 index = enclosing_breakables.stack.len();
4911 enclosing_breakables.by_id.insert(id, index);
4912 enclosing_breakables.stack.push(ctxt);
4916 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4917 debug_assert!(enclosing_breakables.stack.len() == index + 1);
4918 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
4919 enclosing_breakables.stack.pop().expect("missing breakable context")
4924 /// Instantiate a QueryResponse in a probe context, without a
4925 /// good ObligationCause.
4926 fn probe_instantiate_query_response(
4929 original_values: &OriginalQueryValues<'tcx>,
4930 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
4931 ) -> InferResult<'tcx, Ty<'tcx>>
4933 self.instantiate_query_response_and_region_obligations(
4934 &traits::ObligationCause::misc(span, self.body_id),
4940 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
4941 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
4942 let mut contained_in_place = false;
4944 while let hir::Node::Expr(parent_expr) =
4945 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
4947 match &parent_expr.node {
4948 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
4949 if lhs.hir_id == expr_id {
4950 contained_in_place = true;
4956 expr_id = parent_expr.hir_id;
4963 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
4964 let own_counts = generics.own_counts();
4966 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
4972 if own_counts.types == 0 {
4976 // Make a vector of booleans initially `false`; set to `true` when used.
4977 let mut types_used = vec![false; own_counts.types];
4979 for leaf_ty in ty.walk() {
4980 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.sty {
4981 debug!("found use of ty param num {}", index);
4982 types_used[index as usize - own_counts.lifetimes] = true;
4983 } else if let ty::Error = leaf_ty.sty {
4984 // If there is already another error, do not emit
4985 // an error for not using a type parameter.
4986 assert!(tcx.sess.has_errors());
4991 let types = generics.params.iter().filter(|param| match param.kind {
4992 ty::GenericParamDefKind::Type { .. } => true,
4995 for (&used, param) in types_used.iter().zip(types) {
4997 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
4998 let span = tcx.hir().span(id);
4999 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5000 .span_label(span, "unused type parameter")
5006 fn fatally_break_rust(sess: &Session) {
5007 let handler = sess.diagnostic();
5008 handler.span_bug_no_panic(
5010 "It looks like you're trying to break rust; would you like some ICE?",
5012 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5013 handler.note_without_error(
5014 "we would appreciate a joke overview: \
5015 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5017 handler.note_without_error(&format!("rustc {} running on {}",
5018 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5019 crate::session::config::host_triple(),
5023 fn potentially_plural_count(count: usize, word: &str) -> String {
5024 format!("{} {}{}", count, word, pluralise!(count))