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_index::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::{
120 GenericArgKind, Subst, InternalSubsts, SubstsRef, UserSelfTy, UserSubsts,
122 use rustc::ty::util::{Representability, IntTypeExt, Discr};
123 use rustc::ty::layout::VariantIdx;
124 use syntax_pos::{self, BytePos, Span, MultiSpan};
125 use syntax_pos::hygiene::DesugaringKind;
128 use syntax::feature_gate::{GateIssue, emit_feature_err};
129 use syntax::source_map::{DUMMY_SP, original_sp};
130 use syntax::symbol::{kw, sym};
131 use syntax::util::parser::ExprPrecedence;
133 use std::cell::{Cell, RefCell, Ref, RefMut};
134 use std::collections::hash_map::Entry;
137 use std::mem::replace;
138 use std::ops::{self, Deref};
141 use crate::require_c_abi_if_c_variadic;
142 use crate::session::Session;
143 use crate::session::config::EntryFnType;
144 use crate::TypeAndSubsts;
146 use crate::util::captures::Captures;
147 use crate::util::common::{ErrorReported, indenter};
148 use crate::util::nodemap::{DefIdMap, DefIdSet, FxHashSet, HirIdMap};
150 pub use self::Expectation::*;
151 use self::autoderef::Autoderef;
152 use self::callee::DeferredCallResolution;
153 use self::coercion::{CoerceMany, DynamicCoerceMany};
154 pub use self::compare_method::{compare_impl_method, compare_const_impl};
155 use self::method::{MethodCallee, SelfSource};
156 use self::TupleArgumentsFlag::*;
158 /// The type of a local binding, including the revealed type for anon types.
159 #[derive(Copy, Clone, Debug)]
160 pub struct LocalTy<'tcx> {
162 revealed_ty: Ty<'tcx>
165 /// A wrapper for `InferCtxt`'s `in_progress_tables` field.
166 #[derive(Copy, Clone)]
167 struct MaybeInProgressTables<'a, 'tcx> {
168 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
171 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
172 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
173 match self.maybe_tables {
174 Some(tables) => tables.borrow(),
176 bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables")
181 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
182 match self.maybe_tables {
183 Some(tables) => tables.borrow_mut(),
185 bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables")
191 /// Closures defined within the function. For example:
194 /// bar(move|| { ... })
197 /// Here, the function `foo()` and the closure passed to
198 /// `bar()` will each have their own `FnCtxt`, but they will
199 /// share the inherited fields.
200 pub struct Inherited<'a, 'tcx> {
201 infcx: InferCtxt<'a, 'tcx>,
203 tables: MaybeInProgressTables<'a, 'tcx>,
205 locals: RefCell<HirIdMap<LocalTy<'tcx>>>,
207 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
209 // Some additional `Sized` obligations badly affect type inference.
210 // These obligations are added in a later stage of typeck.
211 deferred_sized_obligations: RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
213 // When we process a call like `c()` where `c` is a closure type,
214 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
215 // `FnOnce` closure. In that case, we defer full resolution of the
216 // call until upvar inference can kick in and make the
217 // decision. We keep these deferred resolutions grouped by the
218 // def-id of the closure, so that once we decide, we can easily go
219 // back and process them.
220 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
222 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
224 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
226 // Opaque types found in explicit return types and their
227 // associated fresh inference variable. Writeback resolves these
228 // variables to get the concrete type, which can be used to
229 // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
230 opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
232 /// Each type parameter has an implicit region bound that
233 /// indicates it must outlive at least the function body (the user
234 /// may specify stronger requirements). This field indicates the
235 /// region of the callee. If it is `None`, then the parameter
236 /// environment is for an item or something where the "callee" is
238 implicit_region_bound: Option<ty::Region<'tcx>>,
240 body_id: Option<hir::BodyId>,
243 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
244 type Target = InferCtxt<'a, 'tcx>;
245 fn deref(&self) -> &Self::Target {
250 /// When type-checking an expression, we propagate downward
251 /// whatever type hint we are able in the form of an `Expectation`.
252 #[derive(Copy, Clone, Debug)]
253 pub enum Expectation<'tcx> {
254 /// We know nothing about what type this expression should have.
257 /// This expression should have the type given (or some subtype).
258 ExpectHasType(Ty<'tcx>),
260 /// This expression will be cast to the `Ty`.
261 ExpectCastableToType(Ty<'tcx>),
263 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
264 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
265 ExpectRvalueLikeUnsized(Ty<'tcx>),
268 impl<'a, 'tcx> Expectation<'tcx> {
269 // Disregard "castable to" expectations because they
270 // can lead us astray. Consider for example `if cond
271 // {22} else {c} as u8` -- if we propagate the
272 // "castable to u8" constraint to 22, it will pick the
273 // type 22u8, which is overly constrained (c might not
274 // be a u8). In effect, the problem is that the
275 // "castable to" expectation is not the tightest thing
276 // we can say, so we want to drop it in this case.
277 // The tightest thing we can say is "must unify with
278 // else branch". Note that in the case of a "has type"
279 // constraint, this limitation does not hold.
281 // If the expected type is just a type variable, then don't use
282 // an expected type. Otherwise, we might write parts of the type
283 // when checking the 'then' block which are incompatible with the
285 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
287 ExpectHasType(ety) => {
288 let ety = fcx.shallow_resolve(ety);
289 if !ety.is_ty_var() {
295 ExpectRvalueLikeUnsized(ety) => {
296 ExpectRvalueLikeUnsized(ety)
302 /// Provides an expectation for an rvalue expression given an *optional*
303 /// hint, which is not required for type safety (the resulting type might
304 /// be checked higher up, as is the case with `&expr` and `box expr`), but
305 /// is useful in determining the concrete type.
307 /// The primary use case is where the expected type is a fat pointer,
308 /// like `&[isize]`. For example, consider the following statement:
310 /// let x: &[isize] = &[1, 2, 3];
312 /// In this case, the expected type for the `&[1, 2, 3]` expression is
313 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
314 /// expectation `ExpectHasType([isize])`, that would be too strong --
315 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
316 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
317 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
318 /// which still is useful, because it informs integer literals and the like.
319 /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
320 /// for examples of where this comes up,.
321 fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
322 match fcx.tcx.struct_tail_without_normalization(ty).kind {
323 ty::Slice(_) | ty::Str | ty::Dynamic(..) => {
324 ExpectRvalueLikeUnsized(ty)
326 _ => ExpectHasType(ty)
330 // Resolves `expected` by a single level if it is a variable. If
331 // there is no expected type or resolution is not possible (e.g.,
332 // no constraints yet present), just returns `None`.
333 fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
335 NoExpectation => NoExpectation,
336 ExpectCastableToType(t) => {
337 ExpectCastableToType(fcx.resolve_vars_if_possible(&t))
339 ExpectHasType(t) => {
340 ExpectHasType(fcx.resolve_vars_if_possible(&t))
342 ExpectRvalueLikeUnsized(t) => {
343 ExpectRvalueLikeUnsized(fcx.resolve_vars_if_possible(&t))
348 fn to_option(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
349 match self.resolve(fcx) {
350 NoExpectation => None,
351 ExpectCastableToType(ty) |
353 ExpectRvalueLikeUnsized(ty) => Some(ty),
357 /// It sometimes happens that we want to turn an expectation into
358 /// a **hard constraint** (i.e., something that must be satisfied
359 /// for the program to type-check). `only_has_type` will return
360 /// such a constraint, if it exists.
361 fn only_has_type(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
362 match self.resolve(fcx) {
363 ExpectHasType(ty) => Some(ty),
364 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
368 /// Like `only_has_type`, but instead of returning `None` if no
369 /// hard constraint exists, creates a fresh type variable.
370 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> Ty<'tcx> {
371 self.only_has_type(fcx)
373 fcx.next_ty_var(TypeVariableOrigin {
374 kind: TypeVariableOriginKind::MiscVariable,
381 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
388 fn maybe_mut_place(m: hir::Mutability) -> Self {
390 hir::MutMutable => Needs::MutPlace,
391 hir::MutImmutable => Needs::None,
396 #[derive(Copy, Clone)]
397 pub struct UnsafetyState {
399 pub unsafety: hir::Unsafety,
400 pub unsafe_push_count: u32,
405 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
406 UnsafetyState { def, unsafety, unsafe_push_count: 0, from_fn: true }
409 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
410 match self.unsafety {
411 // If this unsafe, then if the outer function was already marked as
412 // unsafe we shouldn't attribute the unsafe'ness to the block. This
413 // way the block can be warned about instead of ignoring this
414 // extraneous block (functions are never warned about).
415 hir::Unsafety::Unsafe if self.from_fn => *self,
418 let (unsafety, def, count) = match blk.rules {
419 hir::PushUnsafeBlock(..) =>
420 (unsafety, blk.hir_id, self.unsafe_push_count.checked_add(1).unwrap()),
421 hir::PopUnsafeBlock(..) =>
422 (unsafety, blk.hir_id, self.unsafe_push_count.checked_sub(1).unwrap()),
423 hir::UnsafeBlock(..) =>
424 (hir::Unsafety::Unsafe, blk.hir_id, self.unsafe_push_count),
426 (unsafety, self.def, self.unsafe_push_count),
430 unsafe_push_count: count,
437 #[derive(Debug, Copy, Clone)]
443 /// Tracks whether executing a node may exit normally (versus
444 /// return/break/panic, which "diverge", leaving dead code in their
445 /// wake). Tracked semi-automatically (through type variables marked
446 /// as diverging), with some manual adjustments for control-flow
447 /// primitives (approximating a CFG).
448 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
450 /// Potentially unknown, some cases converge,
451 /// others require a CFG to determine them.
454 /// Definitely known to diverge and therefore
455 /// not reach the next sibling or its parent.
457 /// The `Span` points to the expression
458 /// that caused us to diverge
459 /// (e.g. `return`, `break`, etc).
461 /// In some cases (e.g. a `match` expression
462 /// where all arms diverge), we may be
463 /// able to provide a more informative
464 /// message to the user.
465 /// If this is `None`, a default messsage
466 /// will be generated, which is suitable
468 custom_note: Option<&'static str>
471 /// Same as `Always` but with a reachability
472 /// warning already emitted.
476 // Convenience impls for combining `Diverges`.
478 impl ops::BitAnd for Diverges {
480 fn bitand(self, other: Self) -> Self {
481 cmp::min(self, other)
485 impl ops::BitOr for Diverges {
487 fn bitor(self, other: Self) -> Self {
488 cmp::max(self, other)
492 impl ops::BitAndAssign for Diverges {
493 fn bitand_assign(&mut self, other: Self) {
494 *self = *self & other;
498 impl ops::BitOrAssign for Diverges {
499 fn bitor_assign(&mut self, other: Self) {
500 *self = *self | other;
505 /// Creates a `Diverges::Always` with the provided `span` and the default note message.
506 fn always(span: Span) -> Diverges {
513 fn is_always(self) -> bool {
514 // Enum comparison ignores the
515 // contents of fields, so we just
516 // fill them in with garbage here.
517 self >= Diverges::Always {
524 pub struct BreakableCtxt<'tcx> {
527 // this is `null` for loops where break with a value is illegal,
528 // such as `while`, `for`, and `while let`
529 coerce: Option<DynamicCoerceMany<'tcx>>,
532 pub struct EnclosingBreakables<'tcx> {
533 stack: Vec<BreakableCtxt<'tcx>>,
534 by_id: HirIdMap<usize>,
537 impl<'tcx> EnclosingBreakables<'tcx> {
538 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
539 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
540 bug!("could not find enclosing breakable with id {}", target_id);
546 pub struct FnCtxt<'a, 'tcx> {
549 /// The parameter environment used for proving trait obligations
550 /// in this function. This can change when we descend into
551 /// closures (as they bring new things into scope), hence it is
552 /// not part of `Inherited` (as of the time of this writing,
553 /// closures do not yet change the environment, but they will
555 param_env: ty::ParamEnv<'tcx>,
557 /// Number of errors that had been reported when we started
558 /// checking this function. On exit, if we find that *more* errors
559 /// have been reported, we will skip regionck and other work that
560 /// expects the types within the function to be consistent.
561 // FIXME(matthewjasper) This should not exist, and it's not correct
562 // if type checking is run in parallel.
563 err_count_on_creation: usize,
565 /// If `Some`, this stores coercion information for returned
566 /// expressions. If `None`, this is in a context where return is
567 /// inappropriate, such as a const expression.
569 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
570 /// can track all the return expressions and then use them to
571 /// compute a useful coercion from the set, similar to a match
572 /// expression or other branching context. You can use methods
573 /// like `expected_ty` to access the declared return type (if
575 ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
577 /// First span of a return site that we find. Used in error messages.
578 ret_coercion_span: RefCell<Option<Span>>,
580 yield_ty: Option<Ty<'tcx>>,
582 ps: RefCell<UnsafetyState>,
584 /// Whether the last checked node generates a divergence (e.g.,
585 /// `return` will set this to `Always`). In general, when entering
586 /// an expression or other node in the tree, the initial value
587 /// indicates whether prior parts of the containing expression may
588 /// have diverged. It is then typically set to `Maybe` (and the
589 /// old value remembered) for processing the subparts of the
590 /// current expression. As each subpart is processed, they may set
591 /// the flag to `Always`, etc. Finally, at the end, we take the
592 /// result and "union" it with the original value, so that when we
593 /// return the flag indicates if any subpart of the parent
594 /// expression (up to and including this part) has diverged. So,
595 /// if you read it after evaluating a subexpression `X`, the value
596 /// you get indicates whether any subexpression that was
597 /// evaluating up to and including `X` diverged.
599 /// We currently use this flag only for diagnostic purposes:
601 /// - To warn about unreachable code: if, after processing a
602 /// sub-expression but before we have applied the effects of the
603 /// current node, we see that the flag is set to `Always`, we
604 /// can issue a warning. This corresponds to something like
605 /// `foo(return)`; we warn on the `foo()` expression. (We then
606 /// update the flag to `WarnedAlways` to suppress duplicate
607 /// reports.) Similarly, if we traverse to a fresh statement (or
608 /// tail expression) from a `Always` setting, we will issue a
609 /// warning. This corresponds to something like `{return;
610 /// foo();}` or `{return; 22}`, where we would warn on the
613 /// An expression represents dead code if, after checking it,
614 /// the diverges flag is set to something other than `Maybe`.
615 diverges: Cell<Diverges>,
617 /// Whether any child nodes have any type errors.
618 has_errors: Cell<bool>,
620 enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
622 inh: &'a Inherited<'a, 'tcx>,
625 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
626 type Target = Inherited<'a, 'tcx>;
627 fn deref(&self) -> &Self::Target {
632 /// Helper type of a temporary returned by `Inherited::build(...)`.
633 /// Necessary because we can't write the following bound:
634 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
635 pub struct InheritedBuilder<'tcx> {
636 infcx: infer::InferCtxtBuilder<'tcx>,
640 impl Inherited<'_, 'tcx> {
641 pub fn build(tcx: TyCtxt<'tcx>, def_id: DefId) -> InheritedBuilder<'tcx> {
642 let hir_id_root = if def_id.is_local() {
643 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
644 DefId::local(hir_id.owner)
650 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
656 impl<'tcx> InheritedBuilder<'tcx> {
657 fn enter<F, R>(&mut self, f: F) -> R
659 F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
661 let def_id = self.def_id;
662 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
666 impl Inherited<'a, 'tcx> {
667 fn new(infcx: InferCtxt<'a, 'tcx>, def_id: DefId) -> Self {
669 let item_id = tcx.hir().as_local_hir_id(def_id);
670 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by(id));
671 let implicit_region_bound = body_id.map(|body_id| {
672 let body = tcx.hir().body(body_id);
673 tcx.mk_region(ty::ReScope(region::Scope {
674 id: body.value.hir_id.local_id,
675 data: region::ScopeData::CallSite
680 tables: MaybeInProgressTables {
681 maybe_tables: infcx.in_progress_tables,
684 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
685 locals: RefCell::new(Default::default()),
686 deferred_sized_obligations: RefCell::new(Vec::new()),
687 deferred_call_resolutions: RefCell::new(Default::default()),
688 deferred_cast_checks: RefCell::new(Vec::new()),
689 deferred_generator_interiors: RefCell::new(Vec::new()),
690 opaque_types: RefCell::new(Default::default()),
691 implicit_region_bound,
696 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
697 debug!("register_predicate({:?})", obligation);
698 if obligation.has_escaping_bound_vars() {
699 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}",
704 .register_predicate_obligation(self, obligation);
707 fn register_predicates<I>(&self, obligations: I)
708 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>>
710 for obligation in obligations {
711 self.register_predicate(obligation);
715 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
716 self.register_predicates(infer_ok.obligations);
720 fn normalize_associated_types_in<T>(&self,
723 param_env: ty::ParamEnv<'tcx>,
725 where T : TypeFoldable<'tcx>
727 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
728 self.register_infer_ok_obligations(ok)
732 struct CheckItemTypesVisitor<'tcx> {
736 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
737 fn visit_item(&mut self, i: &'tcx hir::Item) {
738 check_item_type(self.tcx, i);
740 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
741 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
744 pub fn check_wf_new(tcx: TyCtxt<'_>) {
745 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
746 tcx.hir().krate().par_visit_all_item_likes(&mut visit);
749 fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
750 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
753 fn typeck_item_bodies(tcx: TyCtxt<'_>, crate_num: CrateNum) {
754 debug_assert!(crate_num == LOCAL_CRATE);
755 tcx.par_body_owners(|body_owner_def_id| {
756 tcx.ensure().typeck_tables_of(body_owner_def_id);
760 fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
761 wfcheck::check_item_well_formed(tcx, def_id);
764 fn check_trait_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
765 wfcheck::check_trait_item(tcx, def_id);
768 fn check_impl_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
769 wfcheck::check_impl_item(tcx, def_id);
772 pub fn provide(providers: &mut Providers<'_>) {
773 method::provide(providers);
774 *providers = Providers {
780 check_item_well_formed,
781 check_trait_item_well_formed,
782 check_impl_item_well_formed,
783 check_mod_item_types,
788 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
789 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
792 /// If this `DefId` is a "primary tables entry", returns
793 /// `Some((body_id, header, decl))` with information about
794 /// it's body-id, fn-header and fn-decl (if any). Otherwise,
797 /// If this function returns `Some`, then `typeck_tables(def_id)` will
798 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
799 /// may not succeed. In some cases where this function returns `None`
800 /// (notably closures), `typeck_tables(def_id)` would wind up
801 /// redirecting to the owning function.
805 ) -> Option<(hir::BodyId, Option<&hir::Ty>, Option<&hir::FnHeader>, Option<&hir::FnDecl>)> {
806 match tcx.hir().get(id) {
807 Node::Item(item) => {
809 hir::ItemKind::Const(ref ty, body) |
810 hir::ItemKind::Static(ref ty, _, body) =>
811 Some((body, Some(ty), None, None)),
812 hir::ItemKind::Fn(ref decl, ref header, .., body) =>
813 Some((body, None, Some(header), Some(decl))),
818 Node::TraitItem(item) => {
820 hir::TraitItemKind::Const(ref ty, Some(body)) =>
821 Some((body, Some(ty), None, None)),
822 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
823 Some((body, None, Some(&sig.header), Some(&sig.decl))),
828 Node::ImplItem(item) => {
830 hir::ImplItemKind::Const(ref ty, body) =>
831 Some((body, Some(ty), None, None)),
832 hir::ImplItemKind::Method(ref sig, body) =>
833 Some((body, None, Some(&sig.header), Some(&sig.decl))),
838 Node::AnonConst(constant) => Some((constant.body, None, None, None)),
843 fn has_typeck_tables(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
844 // Closures' tables come from their outermost function,
845 // as they are part of the same "inference environment".
846 let outer_def_id = tcx.closure_base_def_id(def_id);
847 if outer_def_id != def_id {
848 return tcx.has_typeck_tables(outer_def_id);
851 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
852 primary_body_of(tcx, id).is_some()
855 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: DefId) -> &DefIdSet {
856 &*tcx.typeck_tables_of(def_id).used_trait_imports
859 fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
860 // Closures' tables come from their outermost function,
861 // as they are part of the same "inference environment".
862 let outer_def_id = tcx.closure_base_def_id(def_id);
863 if outer_def_id != def_id {
864 return tcx.typeck_tables_of(outer_def_id);
867 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
868 let span = tcx.hir().span(id);
870 // Figure out what primary body this item has.
871 let (body_id, body_ty, fn_header, fn_decl) = primary_body_of(tcx, id)
873 span_bug!(span, "can't type-check body of {:?}", def_id);
875 let body = tcx.hir().body(body_id);
877 let tables = Inherited::build(tcx, def_id).enter(|inh| {
878 let param_env = tcx.param_env(def_id);
879 let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
880 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
881 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
882 AstConv::ty_of_fn(&fcx, header.unsafety, header.abi, decl)
887 check_abi(tcx, span, fn_sig.abi());
889 // Compute the fty from point of view of inside the fn.
891 tcx.liberate_late_bound_regions(def_id, &fn_sig);
893 inh.normalize_associated_types_in(body.value.span,
898 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
901 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
902 let expected_type = body_ty.and_then(|ty| match ty.kind {
903 hir::TyKind::Infer => Some(AstConv::ast_ty_to_ty(&fcx, ty)),
905 }).unwrap_or_else(|| tcx.type_of(def_id));
906 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
907 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
909 let revealed_ty = if tcx.features().impl_trait_in_bindings {
910 fcx.instantiate_opaque_types_from_value(
919 // Gather locals in statics (because of block expressions).
920 GatherLocalsVisitor { fcx: &fcx, parent_id: id, }.visit_body(body);
922 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
924 fcx.write_ty(id, revealed_ty);
929 // All type checking constraints were added, try to fallback unsolved variables.
930 fcx.select_obligations_where_possible(false, |_| {});
931 let mut fallback_has_occurred = false;
932 for ty in &fcx.unsolved_variables() {
933 fallback_has_occurred |= fcx.fallback_if_possible(ty);
935 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
937 // Even though coercion casts provide type hints, we check casts after fallback for
938 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
941 // Closure and generator analysis may run after fallback
942 // because they don't constrain other type variables.
943 fcx.closure_analyze(body);
944 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
945 fcx.resolve_generator_interiors(def_id);
947 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
948 let ty = fcx.normalize_ty(span, ty);
949 fcx.require_type_is_sized(ty, span, code);
951 fcx.select_all_obligations_or_error();
953 if fn_decl.is_some() {
954 fcx.regionck_fn(id, body);
956 fcx.regionck_expr(body);
959 fcx.resolve_type_vars_in_body(body)
962 // Consistency check our TypeckTables instance can hold all ItemLocalIds
963 // it will need to hold.
964 assert_eq!(tables.local_id_root, Some(DefId::local(id.owner)));
969 fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
970 if !tcx.sess.target.target.is_abi_supported(abi) {
971 struct_span_err!(tcx.sess, span, E0570,
972 "The ABI `{}` is not supported for the current target", abi).emit()
976 struct GatherLocalsVisitor<'a, 'tcx> {
977 fcx: &'a FnCtxt<'a, 'tcx>,
978 parent_id: hir::HirId,
981 impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
982 fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
985 // infer the variable's type
986 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
987 kind: TypeVariableOriginKind::TypeInference,
990 self.fcx.locals.borrow_mut().insert(nid, LocalTy {
997 // take type that the user specified
998 self.fcx.locals.borrow_mut().insert(nid, typ);
1005 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
1006 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1007 NestedVisitorMap::None
1010 // Add explicitly-declared locals.
1011 fn visit_local(&mut self, local: &'tcx hir::Local) {
1012 let local_ty = match local.ty {
1014 let o_ty = self.fcx.to_ty(&ty);
1016 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
1017 self.fcx.instantiate_opaque_types_from_value(
1026 let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(
1027 &UserType::Ty(revealed_ty)
1029 debug!("visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
1030 ty.hir_id, o_ty, revealed_ty, c_ty);
1031 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
1033 Some(LocalTy { decl_ty: o_ty, revealed_ty })
1037 self.assign(local.span, local.hir_id, local_ty);
1039 debug!("local variable {:?} is assigned type {}",
1041 self.fcx.ty_to_string(
1042 self.fcx.locals.borrow().get(&local.hir_id).unwrap().clone().decl_ty));
1043 intravisit::walk_local(self, local);
1046 // Add pattern bindings.
1047 fn visit_pat(&mut self, p: &'tcx hir::Pat) {
1048 if let PatKind::Binding(_, _, ident, _) = p.kind {
1049 let var_ty = self.assign(p.span, p.hir_id, None);
1051 if !self.fcx.tcx.features().unsized_locals {
1052 self.fcx.require_type_is_sized(var_ty, p.span,
1053 traits::VariableType(p.hir_id));
1056 debug!("pattern binding {} is assigned to {} with type {:?}",
1058 self.fcx.ty_to_string(
1059 self.fcx.locals.borrow().get(&p.hir_id).unwrap().clone().decl_ty),
1062 intravisit::walk_pat(self, p);
1065 // Don't descend into the bodies of nested closures
1068 _: intravisit::FnKind<'tcx>,
1069 _: &'tcx hir::FnDecl,
1076 /// When `check_fn` is invoked on a generator (i.e., a body that
1077 /// includes yield), it returns back some information about the yield
1079 struct GeneratorTypes<'tcx> {
1080 /// Type of value that is yielded.
1083 /// Types that are captured (see `GeneratorInterior` for more).
1086 /// Indicates if the generator is movable or static (immovable).
1087 movability: hir::GeneratorMovability,
1090 /// Helper used for fns and closures. Does the grungy work of checking a function
1091 /// body and returns the function context used for that purpose, since in the case of a fn item
1092 /// there is still a bit more to do.
1095 /// * inherited: other fields inherited from the enclosing fn (if any)
1096 fn check_fn<'a, 'tcx>(
1097 inherited: &'a Inherited<'a, 'tcx>,
1098 param_env: ty::ParamEnv<'tcx>,
1099 fn_sig: ty::FnSig<'tcx>,
1100 decl: &'tcx hir::FnDecl,
1102 body: &'tcx hir::Body,
1103 can_be_generator: Option<hir::GeneratorMovability>,
1104 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
1105 let mut fn_sig = fn_sig.clone();
1107 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1109 // Create the function context. This is either derived from scratch or,
1110 // in the case of closures, based on the outer context.
1111 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1112 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1114 let declared_ret_ty = fn_sig.output();
1115 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1116 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(
1121 debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
1122 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1123 fn_sig = fcx.tcx.mk_fn_sig(
1124 fn_sig.inputs().iter().cloned(),
1131 let span = body.value.span;
1133 fn_maybe_err(fcx.tcx, span, fn_sig.abi);
1135 if body.generator_kind.is_some() && can_be_generator.is_some() {
1136 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
1137 kind: TypeVariableOriginKind::TypeInference,
1140 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1141 fcx.yield_ty = Some(yield_ty);
1144 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id(fn_id));
1145 let outer_hir_id = fcx.tcx.hir().as_local_hir_id(outer_def_id).unwrap();
1146 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id, }.visit_body(body);
1148 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
1149 // (as it's created inside the body itself, not passed in from outside).
1150 let maybe_va_list = if fn_sig.c_variadic {
1151 let va_list_did = fcx.tcx.require_lang_item(
1152 lang_items::VaListTypeLangItem,
1153 Some(body.params.last().unwrap().span),
1155 let region = fcx.tcx.mk_region(ty::ReScope(region::Scope {
1156 id: body.value.hir_id.local_id,
1157 data: region::ScopeData::CallSite
1160 Some(fcx.tcx.type_of(va_list_did).subst(fcx.tcx, &[region.into()]))
1165 // Add formal parameters.
1166 for (param_ty, param) in
1167 fn_sig.inputs().iter().copied()
1168 .chain(maybe_va_list)
1171 // Check the pattern.
1172 fcx.check_pat_top(¶m.pat, param_ty, None);
1174 // Check that argument is Sized.
1175 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1176 // for simple cases like `fn foo(x: Trait)`,
1177 // where we would error once on the parameter as a whole, and once on the binding `x`.
1178 if param.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1179 fcx.require_type_is_sized(param_ty, decl.output.span(), traits::SizedArgumentType);
1182 fcx.write_ty(param.hir_id, param_ty);
1185 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1187 fcx.check_return_expr(&body.value);
1189 // We insert the deferred_generator_interiors entry after visiting the body.
1190 // This ensures that all nested generators appear before the entry of this generator.
1191 // resolve_generator_interiors relies on this property.
1192 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
1193 let interior = fcx.next_ty_var(TypeVariableOrigin {
1194 kind: TypeVariableOriginKind::MiscVariable,
1197 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
1198 Some(GeneratorTypes {
1199 yield_ty: fcx.yield_ty.unwrap(),
1201 movability: can_be_generator.unwrap(),
1207 // Finalize the return check by taking the LUB of the return types
1208 // we saw and assigning it to the expected return type. This isn't
1209 // really expected to fail, since the coercions would have failed
1210 // earlier when trying to find a LUB.
1212 // However, the behavior around `!` is sort of complex. In the
1213 // event that the `actual_return_ty` comes back as `!`, that
1214 // indicates that the fn either does not return or "returns" only
1215 // values of type `!`. In this case, if there is an expected
1216 // return type that is *not* `!`, that should be ok. But if the
1217 // return type is being inferred, we want to "fallback" to `!`:
1219 // let x = move || panic!();
1221 // To allow for that, I am creating a type variable with diverging
1222 // fallback. This was deemed ever so slightly better than unifying
1223 // the return value with `!` because it allows for the caller to
1224 // make more assumptions about the return type (e.g., they could do
1226 // let y: Option<u32> = Some(x());
1228 // which would then cause this return type to become `u32`, not
1230 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1231 let mut actual_return_ty = coercion.complete(&fcx);
1232 if actual_return_ty.is_never() {
1233 actual_return_ty = fcx.next_diverging_ty_var(
1234 TypeVariableOrigin {
1235 kind: TypeVariableOriginKind::DivergingFn,
1240 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1242 // Check that the main return type implements the termination trait.
1243 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1244 if let Some((def_id, EntryFnType::Main)) = fcx.tcx.entry_fn(LOCAL_CRATE) {
1245 let main_id = fcx.tcx.hir().as_local_hir_id(def_id).unwrap();
1246 if main_id == fn_id {
1247 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1248 let trait_ref = ty::TraitRef::new(term_id, substs);
1249 let return_ty_span = decl.output.span();
1250 let cause = traits::ObligationCause::new(
1251 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1253 inherited.register_predicate(
1254 traits::Obligation::new(
1255 cause, param_env, trait_ref.to_predicate()));
1260 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1261 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1262 if panic_impl_did == fcx.tcx.hir().local_def_id(fn_id) {
1263 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1264 // at this point we don't care if there are duplicate handlers or if the handler has
1265 // the wrong signature as this value we'll be used when writing metadata and that
1266 // only happens if compilation succeeded
1267 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1269 if declared_ret_ty.kind != ty::Never {
1270 fcx.tcx.sess.span_err(
1272 "return type should be `!`",
1276 let inputs = fn_sig.inputs();
1277 let span = fcx.tcx.hir().span(fn_id);
1278 if inputs.len() == 1 {
1279 let arg_is_panic_info = match inputs[0].kind {
1280 ty::Ref(region, ty, mutbl) => match ty.kind {
1281 ty::Adt(ref adt, _) => {
1282 adt.did == panic_info_did &&
1283 mutbl == hir::Mutability::MutImmutable &&
1284 *region != RegionKind::ReStatic
1291 if !arg_is_panic_info {
1292 fcx.tcx.sess.span_err(
1293 decl.inputs[0].span,
1294 "argument should be `&PanicInfo`",
1298 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1299 if let ItemKind::Fn(_, _, ref generics, _) = item.kind {
1300 if !generics.params.is_empty() {
1301 fcx.tcx.sess.span_err(
1303 "should have no type parameters",
1309 let span = fcx.tcx.sess.source_map().def_span(span);
1310 fcx.tcx.sess.span_err(span, "function should have one argument");
1313 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1318 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1319 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1320 if alloc_error_handler_did == fcx.tcx.hir().local_def_id(fn_id) {
1321 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1322 if declared_ret_ty.kind != ty::Never {
1323 fcx.tcx.sess.span_err(
1325 "return type should be `!`",
1329 let inputs = fn_sig.inputs();
1330 let span = fcx.tcx.hir().span(fn_id);
1331 if inputs.len() == 1 {
1332 let arg_is_alloc_layout = match inputs[0].kind {
1333 ty::Adt(ref adt, _) => {
1334 adt.did == alloc_layout_did
1339 if !arg_is_alloc_layout {
1340 fcx.tcx.sess.span_err(
1341 decl.inputs[0].span,
1342 "argument should be `Layout`",
1346 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1347 if let ItemKind::Fn(_, _, ref generics, _) = item.kind {
1348 if !generics.params.is_empty() {
1349 fcx.tcx.sess.span_err(
1351 "`#[alloc_error_handler]` function should have no type \
1358 let span = fcx.tcx.sess.source_map().def_span(span);
1359 fcx.tcx.sess.span_err(span, "function should have one argument");
1362 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1370 fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1371 let def_id = tcx.hir().local_def_id(id);
1372 let def = tcx.adt_def(def_id);
1373 def.destructor(tcx); // force the destructor to be evaluated
1374 check_representable(tcx, span, def_id);
1376 if def.repr.simd() {
1377 check_simd(tcx, span, def_id);
1380 check_transparent(tcx, span, def_id);
1381 check_packed(tcx, span, def_id);
1384 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1385 let def_id = tcx.hir().local_def_id(id);
1386 let def = tcx.adt_def(def_id);
1387 def.destructor(tcx); // force the destructor to be evaluated
1388 check_representable(tcx, span, def_id);
1389 check_transparent(tcx, span, def_id);
1390 check_packed(tcx, span, def_id);
1393 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
1394 /// projections that would result in "inheriting lifetimes".
1395 fn check_opaque<'tcx>(
1398 substs: SubstsRef<'tcx>,
1400 origin: &hir::OpaqueTyOrigin,
1402 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
1403 check_opaque_for_cycles(tcx, def_id, substs, span, origin);
1406 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
1407 /// in "inheriting lifetimes".
1408 fn check_opaque_for_inheriting_lifetimes(
1413 let item = tcx.hir().expect_item(
1414 tcx.hir().as_local_hir_id(def_id).expect("opaque type is not local"));
1415 debug!("check_opaque_for_inheriting_lifetimes: def_id={:?} span={:?} item={:?}",
1416 def_id, span, item);
1419 struct ProhibitOpaqueVisitor<'tcx> {
1420 opaque_identity_ty: Ty<'tcx>,
1421 generics: &'tcx ty::Generics,
1424 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
1425 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
1426 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
1427 if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) }
1430 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1431 debug!("check_opaque_for_inheriting_lifetimes: (visit_region) r={:?}", r);
1432 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
1433 return *index < self.generics.parent_count as u32;
1436 r.super_visit_with(self)
1440 let prohibit_opaque = match item.kind {
1441 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn, .. }) |
1442 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn, .. }) => {
1443 let mut visitor = ProhibitOpaqueVisitor {
1444 opaque_identity_ty: tcx.mk_opaque(
1445 def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1446 generics: tcx.generics_of(def_id),
1448 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1450 tcx.predicates_of(def_id).predicates.iter().any(
1451 |(predicate, _)| predicate.visit_with(&mut visitor))
1456 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1457 if prohibit_opaque {
1458 let is_async = match item.kind {
1459 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1460 hir::OpaqueTyOrigin::AsyncFn => true,
1463 _ => unreachable!(),
1466 tcx.sess.span_err(span, &format!(
1467 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1469 if is_async { "async fn" } else { "impl Trait" },
1474 /// Checks that an opaque type does not contain cycles.
1475 fn check_opaque_for_cycles<'tcx>(
1478 substs: SubstsRef<'tcx>,
1480 origin: &hir::OpaqueTyOrigin,
1482 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1483 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1485 tcx.sess, span, E0733,
1486 "recursion in an `async fn` requires boxing",
1488 .span_label(span, "recursive `async fn`")
1489 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`.")
1492 let mut err = struct_span_err!(
1493 tcx.sess, span, E0720,
1494 "opaque type expands to a recursive type",
1496 err.span_label(span, "expands to a recursive type");
1497 if let ty::Opaque(..) = partially_expanded_type.kind {
1498 err.note("type resolves to itself");
1500 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1507 // Forbid defining intrinsics in Rust code,
1508 // as they must always be defined by the compiler.
1509 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1510 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1511 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1515 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
1517 "check_item_type(it.hir_id={}, it.name={})",
1519 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1521 let _indenter = indenter();
1523 // Consts can play a role in type-checking, so they are included here.
1524 hir::ItemKind::Static(..) => {
1525 let def_id = tcx.hir().local_def_id(it.hir_id);
1526 tcx.typeck_tables_of(def_id);
1527 maybe_check_static_with_link_section(tcx, def_id, it.span);
1529 hir::ItemKind::Const(..) => {
1530 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1532 hir::ItemKind::Enum(ref enum_definition, _) => {
1533 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1535 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1536 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1537 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1538 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1539 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1540 check_impl_items_against_trait(
1547 let trait_def_id = impl_trait_ref.def_id;
1548 check_on_unimplemented(tcx, trait_def_id, it);
1551 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1552 let def_id = tcx.hir().local_def_id(it.hir_id);
1553 check_on_unimplemented(tcx, def_id, it);
1555 for item in items.iter() {
1556 let item = tcx.hir().trait_item(item.id);
1557 if let hir::TraitItemKind::Method(sig, _) = &item.kind {
1558 let abi = sig.header.abi;
1559 fn_maybe_err(tcx, item.ident.span, abi);
1563 hir::ItemKind::Struct(..) => {
1564 check_struct(tcx, it.hir_id, it.span);
1566 hir::ItemKind::Union(..) => {
1567 check_union(tcx, it.hir_id, it.span);
1569 hir::ItemKind::OpaqueTy(hir::OpaqueTy{origin, ..}) => {
1570 let def_id = tcx.hir().local_def_id(it.hir_id);
1572 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1573 check_opaque(tcx, def_id, substs, it.span, &origin);
1575 hir::ItemKind::TyAlias(..) => {
1576 let def_id = tcx.hir().local_def_id(it.hir_id);
1577 let pty_ty = tcx.type_of(def_id);
1578 let generics = tcx.generics_of(def_id);
1579 check_bounds_are_used(tcx, &generics, pty_ty);
1581 hir::ItemKind::ForeignMod(ref m) => {
1582 check_abi(tcx, it.span, m.abi);
1584 if m.abi == Abi::RustIntrinsic {
1585 for item in &m.items {
1586 intrinsic::check_intrinsic_type(tcx, item);
1588 } else if m.abi == Abi::PlatformIntrinsic {
1589 for item in &m.items {
1590 intrinsic::check_platform_intrinsic_type(tcx, item);
1593 for item in &m.items {
1594 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1595 let own_counts = generics.own_counts();
1596 if generics.params.len() - own_counts.lifetimes != 0 {
1597 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1598 (_, 0) => ("type", "types", Some("u32")),
1599 // We don't specify an example value, because we can't generate
1600 // a valid value for any type.
1601 (0, _) => ("const", "consts", None),
1602 _ => ("type or const", "types or consts", None),
1608 "foreign items may not have {} parameters",
1612 &format!("can't have {} parameters", kinds),
1614 // FIXME: once we start storing spans for type arguments, turn this
1615 // into a suggestion.
1617 "replace the {} parameters with concrete {}{}",
1620 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1625 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.kind {
1626 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1631 _ => { /* nothing to do */ }
1635 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1636 // Only restricted on wasm32 target for now
1637 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1641 // If `#[link_section]` is missing, then nothing to verify
1642 let attrs = tcx.codegen_fn_attrs(id);
1643 if attrs.link_section.is_none() {
1647 // For the wasm32 target statics with `#[link_section]` are placed into custom
1648 // sections of the final output file, but this isn't link custom sections of
1649 // other executable formats. Namely we can only embed a list of bytes,
1650 // nothing with pointers to anything else or relocations. If any relocation
1651 // show up, reject them here.
1652 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1653 // the consumer's responsibility to ensure all bytes that have been read
1654 // have defined values.
1655 let instance = ty::Instance::mono(tcx, id);
1656 let cid = GlobalId {
1660 let param_env = ty::ParamEnv::reveal_all();
1661 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1662 let alloc = if let ConstValue::ByRef { alloc, .. } = static_.val {
1665 bug!("Matching on non-ByRef static")
1667 if alloc.relocations().len() != 0 {
1668 let msg = "statics with a custom `#[link_section]` must be a \
1669 simple list of bytes on the wasm target with no \
1670 extra levels of indirection such as references";
1671 tcx.sess.span_err(span, msg);
1676 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item) {
1677 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1678 // an error would be reported if this fails.
1679 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1682 fn report_forbidden_specialization(
1684 impl_item: &hir::ImplItem,
1687 let mut err = struct_span_err!(
1688 tcx.sess, impl_item.span, E0520,
1689 "`{}` specializes an item from a parent `impl`, but \
1690 that item is not marked `default`",
1692 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1695 match tcx.span_of_impl(parent_impl) {
1697 err.span_label(span, "parent `impl` is here");
1698 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1702 err.note(&format!("parent implementation is in crate `{}`", cname));
1709 fn check_specialization_validity<'tcx>(
1711 trait_def: &ty::TraitDef,
1712 trait_item: &ty::AssocItem,
1714 impl_item: &hir::ImplItem,
1716 let ancestors = trait_def.ancestors(tcx, impl_id);
1718 let kind = match impl_item.kind {
1719 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1720 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1721 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1722 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1725 let parent = ancestors.defs(tcx, trait_item.ident, kind, trait_def.def_id).nth(1)
1726 .map(|node_item| node_item.map(|parent| parent.defaultness));
1728 if let Some(parent) = parent {
1729 if tcx.impl_item_is_final(&parent) {
1730 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1736 fn check_impl_items_against_trait<'tcx>(
1740 impl_trait_ref: ty::TraitRef<'tcx>,
1741 impl_item_refs: &[hir::ImplItemRef],
1743 let impl_span = tcx.sess.source_map().def_span(impl_span);
1745 // If the trait reference itself is erroneous (so the compilation is going
1746 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1747 // isn't populated for such impls.
1748 if impl_trait_ref.references_error() { return; }
1750 // Locate trait definition and items
1751 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1752 let mut overridden_associated_type = None;
1754 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1756 // Check existing impl methods to see if they are both present in trait
1757 // and compatible with trait signature
1758 for impl_item in impl_items() {
1759 let ty_impl_item = tcx.associated_item(
1760 tcx.hir().local_def_id(impl_item.hir_id));
1761 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1762 .find(|ac| Namespace::from(&impl_item.kind) == Namespace::from(ac.kind) &&
1763 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1765 // Not compatible, but needed for the error message
1766 tcx.associated_items(impl_trait_ref.def_id)
1767 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1770 // Check that impl definition matches trait definition
1771 if let Some(ty_trait_item) = ty_trait_item {
1772 match impl_item.kind {
1773 hir::ImplItemKind::Const(..) => {
1774 // Find associated const definition.
1775 if ty_trait_item.kind == ty::AssocKind::Const {
1776 compare_const_impl(tcx,
1782 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1783 "item `{}` is an associated const, \
1784 which doesn't match its trait `{}`",
1787 err.span_label(impl_item.span, "does not match trait");
1788 // We can only get the spans from local trait definition
1789 // Same for E0324 and E0325
1790 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1791 err.span_label(trait_span, "item in trait");
1796 hir::ImplItemKind::Method(..) => {
1797 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1798 if ty_trait_item.kind == ty::AssocKind::Method {
1799 compare_impl_method(tcx,
1806 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1807 "item `{}` is an associated method, \
1808 which doesn't match its trait `{}`",
1811 err.span_label(impl_item.span, "does not match trait");
1812 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1813 err.span_label(trait_span, "item in trait");
1818 hir::ImplItemKind::OpaqueTy(..) |
1819 hir::ImplItemKind::TyAlias(_) => {
1820 if ty_trait_item.kind == ty::AssocKind::Type {
1821 if ty_trait_item.defaultness.has_value() {
1822 overridden_associated_type = Some(impl_item);
1825 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1826 "item `{}` is an associated type, \
1827 which doesn't match its trait `{}`",
1830 err.span_label(impl_item.span, "does not match trait");
1831 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1832 err.span_label(trait_span, "item in trait");
1839 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1843 // Check for missing items from trait
1844 let mut missing_items = Vec::new();
1845 let mut invalidated_items = Vec::new();
1846 let associated_type_overridden = overridden_associated_type.is_some();
1847 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1848 let is_implemented = trait_def.ancestors(tcx, impl_id)
1849 .defs(tcx, trait_item.ident, trait_item.kind, impl_trait_ref.def_id)
1851 .map(|node_item| !node_item.node.is_from_trait())
1854 if !is_implemented && !tcx.impl_is_default(impl_id) {
1855 if !trait_item.defaultness.has_value() {
1856 missing_items.push(trait_item);
1857 } else if associated_type_overridden {
1858 invalidated_items.push(trait_item.ident);
1863 if !missing_items.is_empty() {
1864 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1865 "not all trait items implemented, missing: `{}`",
1866 missing_items.iter()
1867 .map(|trait_item| trait_item.ident.to_string())
1868 .collect::<Vec<_>>().join("`, `"));
1869 err.span_label(impl_span, format!("missing `{}` in implementation",
1870 missing_items.iter()
1871 .map(|trait_item| trait_item.ident.to_string())
1872 .collect::<Vec<_>>().join("`, `")));
1873 for trait_item in missing_items {
1874 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1875 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1877 err.note_trait_signature(trait_item.ident.to_string(),
1878 trait_item.signature(tcx));
1884 if !invalidated_items.is_empty() {
1885 let invalidator = overridden_associated_type.unwrap();
1886 span_err!(tcx.sess, invalidator.span, E0399,
1887 "the following trait items need to be reimplemented \
1888 as `{}` was overridden: `{}`",
1890 invalidated_items.iter()
1891 .map(|name| name.to_string())
1892 .collect::<Vec<_>>().join("`, `"))
1896 /// Checks whether a type can be represented in memory. In particular, it
1897 /// identifies types that contain themselves without indirection through a
1898 /// pointer, which would mean their size is unbounded.
1899 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
1900 let rty = tcx.type_of(item_def_id);
1902 // Check that it is possible to represent this type. This call identifies
1903 // (1) types that contain themselves and (2) types that contain a different
1904 // recursive type. It is only necessary to throw an error on those that
1905 // contain themselves. For case 2, there must be an inner type that will be
1906 // caught by case 1.
1907 match rty.is_representable(tcx, sp) {
1908 Representability::SelfRecursive(spans) => {
1909 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1911 err.span_label(span, "recursive without indirection");
1916 Representability::Representable | Representability::ContainsRecursive => (),
1921 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1922 let t = tcx.type_of(def_id);
1923 if let ty::Adt(def, substs) = t.kind {
1924 if def.is_struct() {
1925 let fields = &def.non_enum_variant().fields;
1926 if fields.is_empty() {
1927 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1930 let e = fields[0].ty(tcx, substs);
1931 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1932 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1933 .span_label(sp, "SIMD elements must have the same type")
1938 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1939 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1941 span_err!(tcx.sess, sp, E0077,
1942 "SIMD vector element type should be machine type");
1950 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1951 let repr = tcx.adt_def(def_id).repr;
1953 for attr in tcx.get_attrs(def_id).iter() {
1954 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
1955 if let attr::ReprPacked(pack) = r {
1956 if let Some(repr_pack) = repr.pack {
1957 if pack as u64 != repr_pack.bytes() {
1959 tcx.sess, sp, E0634,
1960 "type has conflicting packed representation hints"
1967 if repr.align.is_some() {
1968 struct_span_err!(tcx.sess, sp, E0587,
1969 "type has conflicting packed and align representation hints").emit();
1971 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1972 struct_span_err!(tcx.sess, sp, E0588,
1973 "packed type cannot transitively contain a `[repr(align)]` type").emit();
1978 fn check_packed_inner(tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec<DefId>) -> bool {
1979 let t = tcx.type_of(def_id);
1980 if stack.contains(&def_id) {
1981 debug!("check_packed_inner: {:?} is recursive", t);
1984 if let ty::Adt(def, substs) = t.kind {
1985 if def.is_struct() || def.is_union() {
1986 if tcx.adt_def(def.did).repr.align.is_some() {
1989 // push struct def_id before checking fields
1991 for field in &def.non_enum_variant().fields {
1992 let f = field.ty(tcx, substs);
1993 if let ty::Adt(def, _) = f.kind {
1994 if check_packed_inner(tcx, def.did, stack) {
1999 // only need to pop if not early out
2006 /// Emit an error when encountering more or less than one variant in a transparent enum.
2007 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2008 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
2009 tcx.hir().span_if_local(variant.def_id).unwrap()
2012 "needs exactly one variant, but has {}",
2015 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2016 err.span_label(sp, &msg);
2017 if let &[ref start @ .., ref end] = &variant_spans[..] {
2018 for variant_span in start {
2019 err.span_label(*variant_span, "");
2021 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2026 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2028 fn bad_non_zero_sized_fields<'tcx>(
2030 adt: &'tcx ty::AdtDef,
2032 field_spans: impl Iterator<Item = Span>,
2035 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2036 let mut err = struct_span_err!(
2040 "{}transparent {} {}",
2041 if adt.is_enum() { "the variant of a " } else { "" },
2045 err.span_label(sp, &msg);
2046 for sp in field_spans {
2047 err.span_label(sp, "this field is non-zero-sized");
2052 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2053 let adt = tcx.adt_def(def_id);
2054 if !adt.repr.transparent() {
2057 let sp = tcx.sess.source_map().def_span(sp);
2060 if !tcx.features().transparent_enums {
2062 &tcx.sess.parse_sess,
2063 sym::transparent_enums,
2065 GateIssue::Language,
2066 "transparent enums are unstable",
2069 if adt.variants.len() != 1 {
2070 bad_variant_count(tcx, adt, sp, def_id);
2071 if adt.variants.is_empty() {
2072 // Don't bother checking the fields. No variants (and thus no fields) exist.
2078 if adt.is_union() && !tcx.features().transparent_unions {
2079 emit_feature_err(&tcx.sess.parse_sess,
2080 sym::transparent_unions,
2082 GateIssue::Language,
2083 "transparent unions are unstable");
2086 // For each field, figure out if it's known to be a ZST and align(1)
2087 let field_infos = adt.all_fields().map(|field| {
2088 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2089 let param_env = tcx.param_env(field.did);
2090 let layout = tcx.layout_of(param_env.and(ty));
2091 // We are currently checking the type this field came from, so it must be local
2092 let span = tcx.hir().span_if_local(field.did).unwrap();
2093 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2094 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2098 let non_zst_fields = field_infos.clone().filter_map(|(span, zst, _align1)| if !zst {
2103 let non_zst_count = non_zst_fields.clone().count();
2104 if non_zst_count != 1 {
2105 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2107 for (span, zst, align1) in field_infos {
2113 "zero-sized field in transparent {} has alignment larger than 1",
2115 ).span_label(span, "has alignment larger than 1").emit();
2120 #[allow(trivial_numeric_casts)]
2121 pub fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, vs: &'tcx [hir::Variant], id: hir::HirId) {
2122 let def_id = tcx.hir().local_def_id(id);
2123 let def = tcx.adt_def(def_id);
2124 def.destructor(tcx); // force the destructor to be evaluated
2127 let attributes = tcx.get_attrs(def_id);
2128 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2130 tcx.sess, attr.span, E0084,
2131 "unsupported representation for zero-variant enum")
2132 .span_label(sp, "zero-variant enum")
2137 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2138 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2139 if !tcx.features().repr128 {
2140 emit_feature_err(&tcx.sess.parse_sess,
2143 GateIssue::Language,
2144 "repr with 128-bit type is unstable");
2149 if let Some(ref e) = v.disr_expr {
2150 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2154 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2156 |var: &hir::Variant| match var.data {
2157 hir::VariantData::Unit(..) => true,
2161 let has_disr = |var: &hir::Variant| var.disr_expr.is_some();
2162 let has_non_units = vs.iter().any(|var| !is_unit(var));
2163 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2164 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2166 if disr_non_unit || (disr_units && has_non_units) {
2167 let mut err = struct_span_err!(tcx.sess, sp, E0732,
2168 "`#[repr(inttype)]` must be specified");
2173 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2174 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2175 // Check for duplicate discriminant values
2176 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2177 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2178 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2179 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2180 let i_span = match variant_i.disr_expr {
2181 Some(ref expr) => tcx.hir().span(expr.hir_id),
2182 None => tcx.hir().span(variant_i_hir_id)
2184 let span = match v.disr_expr {
2185 Some(ref expr) => tcx.hir().span(expr.hir_id),
2188 struct_span_err!(tcx.sess, span, E0081,
2189 "discriminant value `{}` already exists", disr_vals[i])
2190 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2191 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
2194 disr_vals.push(discr);
2197 check_representable(tcx, sp, def_id);
2198 check_transparent(tcx, sp, def_id);
2201 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span, qpath: &QPath) {
2202 span_err!(tcx.sess, span, E0533,
2203 "expected unit struct/variant or constant, found {} `{}`",
2205 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
2208 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2209 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2213 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
2214 -> &'tcx ty::GenericPredicates<'tcx>
2217 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2218 let item_id = tcx.hir().ty_param_owner(hir_id);
2219 let item_def_id = tcx.hir().local_def_id(item_id);
2220 let generics = tcx.generics_of(item_def_id);
2221 let index = generics.param_def_id_to_index[&def_id];
2222 tcx.arena.alloc(ty::GenericPredicates {
2224 predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
2226 ty::Predicate::Trait(ref data)
2227 if data.skip_binder().self_ty().is_param(index) => {
2228 // HACK(eddyb) should get the original `Span`.
2229 let span = tcx.def_span(def_id);
2230 Some((predicate, span))
2240 def: Option<&ty::GenericParamDef>,
2242 ) -> Option<ty::Region<'tcx>> {
2244 Some(def) => infer::EarlyBoundRegion(span, def.name),
2245 None => infer::MiscVariable(span)
2247 Some(self.next_region_var(v))
2250 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2251 if let Some(param) = param {
2252 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2257 self.next_ty_var(TypeVariableOrigin {
2258 kind: TypeVariableOriginKind::TypeInference,
2267 param: Option<&ty::GenericParamDef>,
2269 ) -> &'tcx Const<'tcx> {
2270 if let Some(param) = param {
2271 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2276 self.next_const_var(ty, ConstVariableOrigin {
2277 kind: ConstVariableOriginKind::ConstInference,
2283 fn projected_ty_from_poly_trait_ref(&self,
2286 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2289 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2291 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2295 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2298 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2299 if ty.has_escaping_bound_vars() {
2300 ty // FIXME: normalization and escaping regions
2302 self.normalize_associated_types_in(span, &ty)
2306 fn set_tainted_by_errors(&self) {
2307 self.infcx.set_tainted_by_errors()
2310 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2311 self.write_ty(hir_id, ty)
2315 /// Controls whether the arguments are tupled. This is used for the call
2318 /// Tupling means that all call-side arguments are packed into a tuple and
2319 /// passed as a single parameter. For example, if tupling is enabled, this
2322 /// fn f(x: (isize, isize))
2324 /// Can be called as:
2331 #[derive(Clone, Eq, PartialEq)]
2332 enum TupleArgumentsFlag {
2337 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2339 inh: &'a Inherited<'a, 'tcx>,
2340 param_env: ty::ParamEnv<'tcx>,
2341 body_id: hir::HirId,
2342 ) -> FnCtxt<'a, 'tcx> {
2346 err_count_on_creation: inh.tcx.sess.err_count(),
2348 ret_coercion_span: RefCell::new(None),
2350 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2351 hir::CRATE_HIR_ID)),
2352 diverges: Cell::new(Diverges::Maybe),
2353 has_errors: Cell::new(false),
2354 enclosing_breakables: RefCell::new(EnclosingBreakables {
2356 by_id: Default::default(),
2362 pub fn sess(&self) -> &Session {
2366 pub fn errors_reported_since_creation(&self) -> bool {
2367 self.tcx.sess.err_count() > self.err_count_on_creation
2370 /// Produces warning on the given node, if the current point in the
2371 /// function is unreachable, and there hasn't been another warning.
2372 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2373 // FIXME: Combine these two 'if' expressions into one once
2374 // let chains are implemented
2375 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2376 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2377 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2378 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2379 if !span.is_desugaring(DesugaringKind::CondTemporary) &&
2380 !span.is_desugaring(DesugaringKind::Async) &&
2381 !orig_span.is_desugaring(DesugaringKind::Await)
2383 self.diverges.set(Diverges::WarnedAlways);
2385 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2387 let msg = format!("unreachable {}", kind);
2388 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2389 .span_label(span, &msg)
2392 custom_note.unwrap_or("any code following this expression is unreachable"),
2401 code: ObligationCauseCode<'tcx>)
2402 -> ObligationCause<'tcx> {
2403 ObligationCause::new(span, self.body_id, code)
2406 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2407 self.cause(span, ObligationCauseCode::MiscObligation)
2410 /// Resolves type variables in `ty` if possible. Unlike the infcx
2411 /// version (resolve_vars_if_possible), this version will
2412 /// also select obligations if it seems useful, in an effort
2413 /// to get more type information.
2414 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2415 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2417 // No Infer()? Nothing needs doing.
2418 if !ty.has_infer_types() {
2419 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2423 // If `ty` is a type variable, see whether we already know what it is.
2424 ty = self.resolve_vars_if_possible(&ty);
2425 if !ty.has_infer_types() {
2426 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2430 // If not, try resolving pending obligations as much as
2431 // possible. This can help substantially when there are
2432 // indirect dependencies that don't seem worth tracking
2434 self.select_obligations_where_possible(false, |_| {});
2435 ty = self.resolve_vars_if_possible(&ty);
2437 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2441 fn record_deferred_call_resolution(
2443 closure_def_id: DefId,
2444 r: DeferredCallResolution<'tcx>,
2446 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2447 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2450 fn remove_deferred_call_resolutions(
2452 closure_def_id: DefId,
2453 ) -> Vec<DeferredCallResolution<'tcx>> {
2454 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2455 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2458 pub fn tag(&self) -> String {
2459 format!("{:p}", self)
2462 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2463 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2464 span_bug!(span, "no type for local variable {}",
2465 self.tcx.hir().node_to_string(nid))
2470 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2471 debug!("write_ty({:?}, {:?}) in fcx {}",
2472 id, self.resolve_vars_if_possible(&ty), self.tag());
2473 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2475 if ty.references_error() {
2476 self.has_errors.set(true);
2477 self.set_tainted_by_errors();
2481 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2482 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2485 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2486 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2489 pub fn write_method_call(&self,
2491 method: MethodCallee<'tcx>) {
2492 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2493 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2494 self.write_substs(hir_id, method.substs);
2496 // When the method is confirmed, the `method.substs` includes
2497 // parameters from not just the method, but also the impl of
2498 // the method -- in particular, the `Self` type will be fully
2499 // resolved. However, those are not something that the "user
2500 // specified" -- i.e., those types come from the inferred type
2501 // of the receiver, not something the user wrote. So when we
2502 // create the user-substs, we want to replace those earlier
2503 // types with just the types that the user actually wrote --
2504 // that is, those that appear on the *method itself*.
2506 // As an example, if the user wrote something like
2507 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2508 // type of `foo` (possibly adjusted), but we don't want to
2509 // include that. We want just the `[_, u32]` part.
2510 if !method.substs.is_noop() {
2511 let method_generics = self.tcx.generics_of(method.def_id);
2512 if !method_generics.params.is_empty() {
2513 let user_type_annotation = self.infcx.probe(|_| {
2514 let user_substs = UserSubsts {
2515 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2516 let i = param.index as usize;
2517 if i < method_generics.parent_count {
2518 self.infcx.var_for_def(DUMMY_SP, param)
2523 user_self_ty: None, // not relevant here
2526 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2532 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2533 self.write_user_type_annotation(hir_id, user_type_annotation);
2538 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2539 if !substs.is_noop() {
2540 debug!("write_substs({:?}, {:?}) in fcx {}",
2545 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2549 /// Given the substs that we just converted from the HIR, try to
2550 /// canonicalize them and store them as user-given substitutions
2551 /// (i.e., substitutions that must be respected by the NLL check).
2553 /// This should be invoked **before any unifications have
2554 /// occurred**, so that annotations like `Vec<_>` are preserved
2556 pub fn write_user_type_annotation_from_substs(
2560 substs: SubstsRef<'tcx>,
2561 user_self_ty: Option<UserSelfTy<'tcx>>,
2564 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2565 user_self_ty={:?} in fcx {}",
2566 hir_id, def_id, substs, user_self_ty, self.tag(),
2569 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2570 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2571 &UserType::TypeOf(def_id, UserSubsts {
2576 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2577 self.write_user_type_annotation(hir_id, canonicalized);
2581 pub fn write_user_type_annotation(
2584 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2587 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2588 hir_id, canonical_user_type_annotation, self.tag(),
2591 if !canonical_user_type_annotation.is_identity() {
2592 self.tables.borrow_mut().user_provided_types_mut().insert(
2593 hir_id, canonical_user_type_annotation
2596 debug!("write_user_type_annotation: skipping identity substs");
2600 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2601 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2607 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2608 Entry::Vacant(entry) => { entry.insert(adj); },
2609 Entry::Occupied(mut entry) => {
2610 debug!(" - composing on top of {:?}", entry.get());
2611 match (&entry.get()[..], &adj[..]) {
2612 // Applying any adjustment on top of a NeverToAny
2613 // is a valid NeverToAny adjustment, because it can't
2615 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2617 Adjustment { kind: Adjust::Deref(_), .. },
2618 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2620 Adjustment { kind: Adjust::Deref(_), .. },
2621 .. // Any following adjustments are allowed.
2623 // A reborrow has no effect before a dereference.
2625 // FIXME: currently we never try to compose autoderefs
2626 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2628 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2629 expr, entry.get(), adj)
2631 *entry.get_mut() = adj;
2636 /// Basically whenever we are converting from a type scheme into
2637 /// the fn body space, we always want to normalize associated
2638 /// types as well. This function combines the two.
2639 fn instantiate_type_scheme<T>(&self,
2641 substs: SubstsRef<'tcx>,
2644 where T : TypeFoldable<'tcx>
2646 let value = value.subst(self.tcx, substs);
2647 let result = self.normalize_associated_types_in(span, &value);
2648 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2655 /// As `instantiate_type_scheme`, but for the bounds found in a
2656 /// generic type scheme.
2657 fn instantiate_bounds(
2661 substs: SubstsRef<'tcx>,
2662 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
2663 let bounds = self.tcx.predicates_of(def_id);
2664 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
2665 let result = bounds.instantiate(self.tcx, substs);
2666 let result = self.normalize_associated_types_in(span, &result);
2668 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
2677 /// Replaces the opaque types from the given value with type variables,
2678 /// and records the `OpaqueTypeMap` for later use during writeback. See
2679 /// `InferCtxt::instantiate_opaque_types` for more details.
2680 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2682 parent_id: hir::HirId,
2686 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2687 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2691 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2692 self.instantiate_opaque_types(
2701 let mut opaque_types = self.opaque_types.borrow_mut();
2702 for (ty, decl) in opaque_type_map {
2703 let old_value = opaque_types.insert(ty, decl);
2704 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2710 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2711 where T : TypeFoldable<'tcx>
2713 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2716 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2718 where T : TypeFoldable<'tcx>
2720 self.inh.partially_normalize_associated_types_in(span,
2726 pub fn require_type_meets(&self,
2729 code: traits::ObligationCauseCode<'tcx>,
2732 self.register_bound(
2735 traits::ObligationCause::new(span, self.body_id, code));
2738 pub fn require_type_is_sized(
2742 code: traits::ObligationCauseCode<'tcx>,
2744 if !ty.references_error() {
2745 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2746 self.require_type_meets(ty, span, code, lang_item);
2750 pub fn require_type_is_sized_deferred(
2754 code: traits::ObligationCauseCode<'tcx>,
2756 if !ty.references_error() {
2757 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2761 pub fn register_bound(
2765 cause: traits::ObligationCause<'tcx>,
2767 if !ty.references_error() {
2768 self.fulfillment_cx.borrow_mut()
2769 .register_bound(self, self.param_env, ty, def_id, cause);
2773 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2774 let t = AstConv::ast_ty_to_ty(self, ast_t);
2775 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2779 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2780 let ty = self.to_ty(ast_ty);
2781 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2783 if Self::can_contain_user_lifetime_bounds(ty) {
2784 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2785 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2786 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2792 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2793 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2794 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2797 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2798 AstConv::ast_const_to_const(self, ast_c, ty)
2801 // If the type given by the user has free regions, save it for later, since
2802 // NLL would like to enforce those. Also pass in types that involve
2803 // projections, since those can resolve to `'static` bounds (modulo #54940,
2804 // which hopefully will be fixed by the time you see this comment, dear
2805 // reader, although I have my doubts). Also pass in types with inference
2806 // types, because they may be repeated. Other sorts of things are already
2807 // sufficiently enforced with erased regions. =)
2808 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2810 T: TypeFoldable<'tcx>
2812 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2815 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2816 match self.tables.borrow().node_types().get(id) {
2818 None if self.is_tainted_by_errors() => self.tcx.types.err,
2820 bug!("no type for node {}: {} in fcx {}",
2821 id, self.tcx.hir().node_to_string(id),
2827 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2828 /// outlive the region `r`.
2829 pub fn register_wf_obligation(
2833 code: traits::ObligationCauseCode<'tcx>,
2835 // WF obligations never themselves fail, so no real need to give a detailed cause:
2836 let cause = traits::ObligationCause::new(span, self.body_id, code);
2837 self.register_predicate(
2838 traits::Obligation::new(cause, self.param_env, ty::Predicate::WellFormed(ty)),
2842 /// Registers obligations that all types appearing in `substs` are well-formed.
2843 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2844 for ty in substs.types() {
2845 if !ty.references_error() {
2846 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2851 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2852 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2853 /// trait/region obligations.
2855 /// For example, if there is a function:
2858 /// fn foo<'a,T:'a>(...)
2861 /// and a reference:
2867 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2868 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2869 pub fn add_obligations_for_parameters(&self,
2870 cause: traits::ObligationCause<'tcx>,
2871 predicates: &ty::InstantiatedPredicates<'tcx>)
2873 assert!(!predicates.has_escaping_bound_vars());
2875 debug!("add_obligations_for_parameters(predicates={:?})",
2878 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2879 self.register_predicate(obligation);
2883 // FIXME(arielb1): use this instead of field.ty everywhere
2884 // Only for fields! Returns <none> for methods>
2885 // Indifferent to privacy flags
2889 field: &'tcx ty::FieldDef,
2890 substs: SubstsRef<'tcx>,
2892 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2895 fn check_casts(&self) {
2896 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2897 for cast in deferred_cast_checks.drain(..) {
2902 fn resolve_generator_interiors(&self, def_id: DefId) {
2903 let mut generators = self.deferred_generator_interiors.borrow_mut();
2904 for (body_id, interior, kind) in generators.drain(..) {
2905 self.select_obligations_where_possible(false, |_| {});
2906 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2910 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2911 // Non-numerics get replaced with ! or () (depending on whether
2912 // feature(never_type) is enabled, unconstrained ints with i32,
2913 // unconstrained floats with f64.
2914 // Fallback becomes very dubious if we have encountered type-checking errors.
2915 // In that case, fallback to Error.
2916 // The return value indicates whether fallback has occurred.
2917 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2918 use rustc::ty::error::UnconstrainedNumeric::Neither;
2919 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2921 assert!(ty.is_ty_infer());
2922 let fallback = match self.type_is_unconstrained_numeric(ty) {
2923 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2924 UnconstrainedInt => self.tcx.types.i32,
2925 UnconstrainedFloat => self.tcx.types.f64,
2926 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2927 Neither => return false,
2929 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2930 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2934 fn select_all_obligations_or_error(&self) {
2935 debug!("select_all_obligations_or_error");
2936 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2937 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2941 /// Select as many obligations as we can at present.
2942 fn select_obligations_where_possible(
2944 fallback_has_occurred: bool,
2945 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
2947 if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2948 mutate_fullfillment_errors(&mut errors);
2949 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2953 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2954 /// returns a type of `&T`, but the actual type we assign to the
2955 /// *expression* is `T`. So this function just peels off the return
2956 /// type by one layer to yield `T`.
2957 fn make_overloaded_place_return_type(&self,
2958 method: MethodCallee<'tcx>)
2959 -> ty::TypeAndMut<'tcx>
2961 // extract method return type, which will be &T;
2962 let ret_ty = method.sig.output();
2964 // method returns &T, but the type as visible to user is T, so deref
2965 ret_ty.builtin_deref(true).unwrap()
2971 base_expr: &'tcx hir::Expr,
2975 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
2976 // FIXME(#18741) -- this is almost but not quite the same as the
2977 // autoderef that normal method probing does. They could likely be
2980 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2981 let mut result = None;
2982 while result.is_none() && autoderef.next().is_some() {
2983 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2985 autoderef.finalize(self);
2989 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2990 /// (and otherwise adjust) `base_expr`, looking for a type which either
2991 /// supports builtin indexing or overloaded indexing.
2992 /// This loop implements one step in that search; the autoderef loop
2993 /// is implemented by `lookup_indexing`.
2997 base_expr: &hir::Expr,
2998 autoderef: &Autoderef<'a, 'tcx>,
3001 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3002 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3003 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3010 for &unsize in &[false, true] {
3011 let mut self_ty = adjusted_ty;
3013 // We only unsize arrays here.
3014 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3015 self_ty = self.tcx.mk_slice(element_ty);
3021 // If some lookup succeeds, write callee into table and extract index/element
3022 // type from the method signature.
3023 // If some lookup succeeded, install method in table
3024 let input_ty = self.next_ty_var(TypeVariableOrigin {
3025 kind: TypeVariableOriginKind::AutoDeref,
3026 span: base_expr.span,
3028 let method = self.try_overloaded_place_op(
3029 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
3031 let result = method.map(|ok| {
3032 debug!("try_index_step: success, using overloaded indexing");
3033 let method = self.register_infer_ok_obligations(ok);
3035 let mut adjustments = autoderef.adjust_steps(self, needs);
3036 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3037 let mutbl = match r_mutbl {
3038 hir::MutImmutable => AutoBorrowMutability::Immutable,
3039 hir::MutMutable => AutoBorrowMutability::Mutable {
3040 // Indexing can be desugared to a method call,
3041 // so maybe we could use two-phase here.
3042 // See the documentation of AllowTwoPhase for why that's
3043 // not the case today.
3044 allow_two_phase_borrow: AllowTwoPhase::No,
3047 adjustments.push(Adjustment {
3048 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3049 target: self.tcx.mk_ref(region, ty::TypeAndMut {
3056 adjustments.push(Adjustment {
3057 kind: Adjust::Pointer(PointerCast::Unsize),
3058 target: method.sig.inputs()[0]
3061 self.apply_adjustments(base_expr, adjustments);
3063 self.write_method_call(expr.hir_id, method);
3064 (input_ty, self.make_overloaded_place_return_type(method).ty)
3066 if result.is_some() {
3074 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3075 let (tr, name) = match (op, is_mut) {
3076 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3077 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3078 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3079 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3081 (tr, ast::Ident::with_dummy_span(name))
3084 fn try_overloaded_place_op(&self,
3087 arg_tys: &[Ty<'tcx>],
3090 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3092 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3098 // Try Mut first, if needed.
3099 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3100 let method = match (needs, mut_tr) {
3101 (Needs::MutPlace, Some(trait_did)) => {
3102 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3107 // Otherwise, fall back to the immutable version.
3108 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3109 let method = match (method, imm_tr) {
3110 (None, Some(trait_did)) => {
3111 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3113 (method, _) => method,
3119 fn check_method_argument_types(
3122 expr: &'tcx hir::Expr,
3123 method: Result<MethodCallee<'tcx>, ()>,
3124 args_no_rcvr: &'tcx [hir::Expr],
3125 tuple_arguments: TupleArgumentsFlag,
3126 expected: Expectation<'tcx>,
3129 let has_error = match method {
3131 method.substs.references_error() || method.sig.references_error()
3136 let err_inputs = self.err_args(args_no_rcvr.len());
3138 let err_inputs = match tuple_arguments {
3139 DontTupleArguments => err_inputs,
3140 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3143 self.check_argument_types(
3153 return self.tcx.types.err;
3156 let method = method.unwrap();
3157 // HACK(eddyb) ignore self in the definition (see above).
3158 let expected_arg_tys = self.expected_inputs_for_expected_output(
3161 method.sig.output(),
3162 &method.sig.inputs()[1..]
3164 self.check_argument_types(
3167 &method.sig.inputs()[1..],
3168 &expected_arg_tys[..],
3170 method.sig.c_variadic,
3172 self.tcx.hir().span_if_local(method.def_id),
3177 fn self_type_matches_expected_vid(
3179 trait_ref: ty::PolyTraitRef<'tcx>,
3180 expected_vid: ty::TyVid,
3182 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3184 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3185 trait_ref, self_ty, expected_vid
3187 match self_ty.kind {
3188 ty::Infer(ty::TyVar(found_vid)) => {
3189 // FIXME: consider using `sub_root_var` here so we
3190 // can see through subtyping.
3191 let found_vid = self.root_var(found_vid);
3192 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3193 expected_vid == found_vid
3199 fn obligations_for_self_ty<'b>(
3202 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3205 // FIXME: consider using `sub_root_var` here so we
3206 // can see through subtyping.
3207 let ty_var_root = self.root_var(self_ty);
3208 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3209 self_ty, ty_var_root,
3210 self.fulfillment_cx.borrow().pending_obligations());
3214 .pending_obligations()
3216 .filter_map(move |obligation| match obligation.predicate {
3217 ty::Predicate::Projection(ref data) =>
3218 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3219 ty::Predicate::Trait(ref data) =>
3220 Some((data.to_poly_trait_ref(), obligation)),
3221 ty::Predicate::Subtype(..) => None,
3222 ty::Predicate::RegionOutlives(..) => None,
3223 ty::Predicate::TypeOutlives(..) => None,
3224 ty::Predicate::WellFormed(..) => None,
3225 ty::Predicate::ObjectSafe(..) => None,
3226 ty::Predicate::ConstEvaluatable(..) => None,
3227 // N.B., this predicate is created by breaking down a
3228 // `ClosureType: FnFoo()` predicate, where
3229 // `ClosureType` represents some `Closure`. It can't
3230 // possibly be referring to the current closure,
3231 // because we haven't produced the `Closure` for
3232 // this closure yet; this is exactly why the other
3233 // code is looking for a self type of a unresolved
3234 // inference variable.
3235 ty::Predicate::ClosureKind(..) => None,
3236 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3239 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3240 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3241 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3245 /// Generic function that factors out common logic from function calls,
3246 /// method calls and overloaded operators.
3247 fn check_argument_types(
3250 expr: &'tcx hir::Expr,
3251 fn_inputs: &[Ty<'tcx>],
3252 expected_arg_tys: &[Ty<'tcx>],
3253 args: &'tcx [hir::Expr],
3255 tuple_arguments: TupleArgumentsFlag,
3256 def_span: Option<Span>,
3259 // Grab the argument types, supplying fresh type variables
3260 // if the wrong number of arguments were supplied
3261 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3267 // All the input types from the fn signature must outlive the call
3268 // so as to validate implied bounds.
3269 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3270 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3273 let expected_arg_count = fn_inputs.len();
3275 let param_count_error = |expected_count: usize,
3280 let mut err = tcx.sess.struct_span_err_with_code(sp,
3281 &format!("this function takes {}{} but {} {} supplied",
3282 if c_variadic { "at least " } else { "" },
3283 potentially_plural_count(expected_count, "parameter"),
3284 potentially_plural_count(arg_count, "parameter"),
3285 if arg_count == 1 {"was"} else {"were"}),
3286 DiagnosticId::Error(error_code.to_owned()));
3288 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3289 err.span_label(def_s, "defined here");
3292 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3293 // remove closing `)` from the span
3294 let sugg_span = sugg_span.shrink_to_lo();
3295 err.span_suggestion(
3297 "expected the unit value `()`; create it with empty parentheses",
3299 Applicability::MachineApplicable);
3301 err.span_label(sp, format!("expected {}{}",
3302 if c_variadic { "at least " } else { "" },
3303 potentially_plural_count(expected_count, "parameter")));
3308 let mut expected_arg_tys = expected_arg_tys.to_vec();
3310 let formal_tys = if tuple_arguments == TupleArguments {
3311 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3312 match tuple_type.kind {
3313 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3314 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3315 expected_arg_tys = vec![];
3316 self.err_args(args.len())
3318 ty::Tuple(arg_types) => {
3319 expected_arg_tys = match expected_arg_tys.get(0) {
3320 Some(&ty) => match ty.kind {
3321 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3326 arg_types.iter().map(|k| k.expect_ty()).collect()
3329 span_err!(tcx.sess, sp, E0059,
3330 "cannot use call notation; the first type parameter \
3331 for the function trait is neither a tuple nor unit");
3332 expected_arg_tys = vec![];
3333 self.err_args(args.len())
3336 } else if expected_arg_count == supplied_arg_count {
3338 } else if c_variadic {
3339 if supplied_arg_count >= expected_arg_count {
3342 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3343 expected_arg_tys = vec![];
3344 self.err_args(supplied_arg_count)
3347 // is the missing argument of type `()`?
3348 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3349 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3350 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3351 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3355 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3357 expected_arg_tys = vec![];
3358 self.err_args(supplied_arg_count)
3361 debug!("check_argument_types: formal_tys={:?}",
3362 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3364 // If there is no expectation, expect formal_tys.
3365 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3371 let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
3373 // Check the arguments.
3374 // We do this in a pretty awful way: first we type-check any arguments
3375 // that are not closures, then we type-check the closures. This is so
3376 // that we have more information about the types of arguments when we
3377 // type-check the functions. This isn't really the right way to do this.
3378 for &check_closures in &[false, true] {
3379 debug!("check_closures={}", check_closures);
3381 // More awful hacks: before we check argument types, try to do
3382 // an "opportunistic" vtable resolution of any trait bounds on
3383 // the call. This helps coercions.
3385 self.select_obligations_where_possible(false, |errors| {
3386 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
3387 self.point_at_arg_instead_of_call_if_possible(
3389 &final_arg_types[..],
3396 // For C-variadic functions, we don't have a declared type for all of
3397 // the arguments hence we only do our usual type checking with
3398 // the arguments who's types we do know.
3399 let t = if c_variadic {
3401 } else if tuple_arguments == TupleArguments {
3406 for (i, arg) in args.iter().take(t).enumerate() {
3407 // Warn only for the first loop (the "no closures" one).
3408 // Closure arguments themselves can't be diverging, but
3409 // a previous argument can, e.g., `foo(panic!(), || {})`.
3410 if !check_closures {
3411 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3414 let is_closure = match arg.kind {
3415 ExprKind::Closure(..) => true,
3419 if is_closure != check_closures {
3423 debug!("checking the argument");
3424 let formal_ty = formal_tys[i];
3426 // The special-cased logic below has three functions:
3427 // 1. Provide as good of an expected type as possible.
3428 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3430 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3432 // 2. Coerce to the most detailed type that could be coerced
3433 // to, which is `expected_ty` if `rvalue_hint` returns an
3434 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3435 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3436 // We're processing function arguments so we definitely want to use
3437 // two-phase borrows.
3438 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3439 final_arg_types.push((i, coerce_ty));
3441 // 3. Relate the expected type and the formal one,
3442 // if the expected type was used for the coercion.
3443 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3447 // We also need to make sure we at least write the ty of the other
3448 // arguments which we skipped above.
3450 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3451 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3452 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3455 for arg in args.iter().skip(expected_arg_count) {
3456 let arg_ty = self.check_expr(&arg);
3458 // There are a few types which get autopromoted when passed via varargs
3459 // in C but we just error out instead and require explicit casts.
3460 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3462 ty::Float(ast::FloatTy::F32) => {
3463 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3465 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3466 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3468 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3469 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3472 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3473 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3474 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3482 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3483 vec![self.tcx.types.err; len]
3486 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
3487 /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
3488 /// reference a type argument. If they do, and there's only *one* argument that does, we point
3489 /// at the corresponding argument's expression span instead of the `fn` call path span.
3490 fn point_at_arg_instead_of_call_if_possible(
3492 errors: &mut Vec<traits::FulfillmentError<'_>>,
3493 final_arg_types: &[(usize, Ty<'tcx>)],
3495 args: &'tcx [hir::Expr],
3497 if !call_sp.desugaring_kind().is_some() {
3498 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3499 // the `?` operator.
3500 for error in errors {
3501 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3502 // Collect the argument position for all arguments that could have caused this
3503 // `FullfillmentError`.
3504 let mut referenced_in = final_arg_types.iter()
3505 .flat_map(|(i, ty)| {
3506 let ty = self.resolve_vars_if_possible(ty);
3507 // We walk the argument type because the argument's type could have
3508 // been `Option<T>`, but the `FullfillmentError` references `T`.
3510 .filter(|&ty| ty == predicate.skip_binder().self_ty())
3513 if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
3514 // We make sure that only *one* argument matches the obligation failure
3515 // and thet the obligation's span to its expression's.
3516 error.obligation.cause.span = args[ref_in].span;
3517 error.points_at_arg_span = true;
3524 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call expression, we walk the
3525 /// `PathSegment`s and resolve their type parameters to see if any of the `FullfillmentError`s
3526 /// were caused by them. If they were, we point at the corresponding type argument's span
3527 /// instead of the `fn` call path span.
3528 fn point_at_type_arg_instead_of_call_if_possible(
3530 errors: &mut Vec<traits::FulfillmentError<'_>>,
3531 call_expr: &'tcx hir::Expr,
3533 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
3534 if let hir::ExprKind::Path(qpath) = &path.kind {
3535 if let hir::QPath::Resolved(_, path) = &qpath {
3536 for error in errors {
3537 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3538 // If any of the type arguments in this path segment caused the
3539 // `FullfillmentError`, point at its span (#61860).
3540 for arg in path.segments.iter()
3541 .filter_map(|seg| seg.args.as_ref())
3542 .flat_map(|a| a.args.iter())
3544 if let hir::GenericArg::Type(hir_ty) = &arg {
3545 if let hir::TyKind::Path(
3546 hir::QPath::TypeRelative(..),
3548 // Avoid ICE with associated types. As this is best
3549 // effort only, it's ok to ignore the case. It
3550 // would trigger in `is_send::<T::AssocType>();`
3551 // from `typeck-default-trait-impl-assoc-type.rs`.
3553 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
3554 let ty = self.resolve_vars_if_possible(&ty);
3555 if ty == predicate.skip_binder().self_ty() {
3556 error.obligation.cause.span = hir_ty.span;
3568 // AST fragment checking
3571 expected: Expectation<'tcx>)
3577 ast::LitKind::Str(..) => tcx.mk_static_str(),
3578 ast::LitKind::ByteStr(ref v) => {
3579 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3580 tcx.mk_array(tcx.types.u8, v.len() as u64))
3582 ast::LitKind::Byte(_) => tcx.types.u8,
3583 ast::LitKind::Char(_) => tcx.types.char,
3584 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3585 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3586 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3587 let opt_ty = expected.to_option(self).and_then(|ty| {
3589 ty::Int(_) | ty::Uint(_) => Some(ty),
3590 ty::Char => Some(tcx.types.u8),
3591 ty::RawPtr(..) => Some(tcx.types.usize),
3592 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3596 opt_ty.unwrap_or_else(|| self.next_int_var())
3598 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3599 ast::LitKind::FloatUnsuffixed(_) => {
3600 let opt_ty = expected.to_option(self).and_then(|ty| {
3602 ty::Float(_) => Some(ty),
3606 opt_ty.unwrap_or_else(|| self.next_float_var())
3608 ast::LitKind::Bool(_) => tcx.types.bool,
3609 ast::LitKind::Err(_) => tcx.types.err,
3613 // Determine the `Self` type, using fresh variables for all variables
3614 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3615 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3617 pub fn impl_self_ty(&self,
3618 span: Span, // (potential) receiver for this impl
3620 -> TypeAndSubsts<'tcx> {
3621 let ity = self.tcx.type_of(did);
3622 debug!("impl_self_ty: ity={:?}", ity);
3624 let substs = self.fresh_substs_for_item(span, did);
3625 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3627 TypeAndSubsts { substs: substs, ty: substd_ty }
3630 /// Unifies the output type with the expected type early, for more coercions
3631 /// and forward type information on the input expressions.
3632 fn expected_inputs_for_expected_output(&self,
3634 expected_ret: Expectation<'tcx>,
3635 formal_ret: Ty<'tcx>,
3636 formal_args: &[Ty<'tcx>])
3638 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3639 let ret_ty = match expected_ret.only_has_type(self) {
3641 None => return Vec::new()
3643 let expect_args = self.fudge_inference_if_ok(|| {
3644 // Attempt to apply a subtyping relationship between the formal
3645 // return type (likely containing type variables if the function
3646 // is polymorphic) and the expected return type.
3647 // No argument expectations are produced if unification fails.
3648 let origin = self.misc(call_span);
3649 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3651 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3652 // to identity so the resulting type is not constrained.
3655 // Process any obligations locally as much as
3656 // we can. We don't care if some things turn
3657 // out unconstrained or ambiguous, as we're
3658 // just trying to get hints here.
3659 self.save_and_restore_in_snapshot_flag(|_| {
3660 let mut fulfill = TraitEngine::new(self.tcx);
3661 for obligation in ok.obligations {
3662 fulfill.register_predicate_obligation(self, obligation);
3664 fulfill.select_where_possible(self)
3665 }).map_err(|_| ())?;
3667 Err(_) => return Err(()),
3670 // Record all the argument types, with the substitutions
3671 // produced from the above subtyping unification.
3672 Ok(formal_args.iter().map(|ty| {
3673 self.resolve_vars_if_possible(ty)
3675 }).unwrap_or_default();
3676 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3677 formal_args, formal_ret,
3678 expect_args, expected_ret);
3682 pub fn check_struct_path(&self,
3685 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3686 let path_span = match *qpath {
3687 QPath::Resolved(_, ref path) => path.span,
3688 QPath::TypeRelative(ref qself, _) => qself.span
3690 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3691 let variant = match def {
3693 self.set_tainted_by_errors();
3696 Res::Def(DefKind::Variant, _) => {
3698 ty::Adt(adt, substs) => {
3699 Some((adt.variant_of_res(def), adt.did, substs))
3701 _ => bug!("unexpected type: {:?}", ty)
3704 Res::Def(DefKind::Struct, _)
3705 | Res::Def(DefKind::Union, _)
3706 | Res::Def(DefKind::TyAlias, _)
3707 | Res::Def(DefKind::AssocTy, _)
3708 | Res::SelfTy(..) => {
3710 ty::Adt(adt, substs) if !adt.is_enum() => {
3711 Some((adt.non_enum_variant(), adt.did, substs))
3716 _ => bug!("unexpected definition: {:?}", def)
3719 if let Some((variant, did, substs)) = variant {
3720 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3721 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3723 // Check bounds on type arguments used in the path.
3724 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
3725 let cause = traits::ObligationCause::new(
3728 traits::ItemObligation(did),
3730 self.add_obligations_for_parameters(cause, &bounds);
3734 struct_span_err!(self.tcx.sess, path_span, E0071,
3735 "expected struct, variant or union type, found {}",
3736 ty.sort_string(self.tcx))
3737 .span_label(path_span, "not a struct")
3743 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3744 // The newly resolved definition is written into `type_dependent_defs`.
3745 fn finish_resolving_struct_path(&self,
3752 QPath::Resolved(ref maybe_qself, ref path) => {
3753 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3754 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3757 QPath::TypeRelative(ref qself, ref segment) => {
3758 let ty = self.to_ty(qself);
3760 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
3765 let result = AstConv::associated_path_to_ty(
3774 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3775 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3777 // Write back the new resolution.
3778 self.write_resolution(hir_id, result);
3780 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3785 /// Resolves an associated value path into a base type and associated constant, or method
3786 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3787 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3791 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3793 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3794 let (ty, qself, item_segment) = match *qpath {
3795 QPath::Resolved(ref opt_qself, ref path) => {
3797 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3798 &path.segments[..]);
3800 QPath::TypeRelative(ref qself, ref segment) => {
3801 (self.to_ty(qself), qself, segment)
3804 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3805 // Return directly on cache hit. This is useful to avoid doubly reporting
3806 // errors with default match binding modes. See #44614.
3807 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3808 .unwrap_or(Res::Err);
3809 return (def, Some(ty), slice::from_ref(&**item_segment));
3811 let item_name = item_segment.ident;
3812 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3813 let result = match error {
3814 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3815 _ => Err(ErrorReported),
3817 if item_name.name != kw::Invalid {
3818 self.report_method_error(
3822 SelfSource::QPath(qself),
3825 ).map(|mut e| e.emit());
3830 // Write back the new resolution.
3831 self.write_resolution(hir_id, result);
3833 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3835 slice::from_ref(&**item_segment),
3839 pub fn check_decl_initializer(
3841 local: &'tcx hir::Local,
3842 init: &'tcx hir::Expr,
3844 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3845 // for #42640 (default match binding modes).
3848 let ref_bindings = local.pat.contains_explicit_ref_binding();
3850 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3851 if let Some(m) = ref_bindings {
3852 // Somewhat subtle: if we have a `ref` binding in the pattern,
3853 // we want to avoid introducing coercions for the RHS. This is
3854 // both because it helps preserve sanity and, in the case of
3855 // ref mut, for soundness (issue #23116). In particular, in
3856 // the latter case, we need to be clear that the type of the
3857 // referent for the reference that results is *equal to* the
3858 // type of the place it is referencing, and not some
3859 // supertype thereof.
3860 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3861 self.demand_eqtype(init.span, local_ty, init_ty);
3864 self.check_expr_coercable_to_type(init, local_ty)
3868 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3869 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3870 self.write_ty(local.hir_id, t);
3872 if let Some(ref init) = local.init {
3873 let init_ty = self.check_decl_initializer(local, &init);
3874 self.overwrite_local_ty_if_err(local, t, init_ty);
3877 self.check_pat_top(&local.pat, t, None);
3878 let pat_ty = self.node_ty(local.pat.hir_id);
3879 self.overwrite_local_ty_if_err(local, t, pat_ty);
3882 fn overwrite_local_ty_if_err(&self, local: &'tcx hir::Local, decl_ty: Ty<'tcx>, ty: Ty<'tcx>) {
3883 if ty.references_error() {
3884 // Override the types everywhere with `types.err` to avoid knock down errors.
3885 self.write_ty(local.hir_id, ty);
3886 self.write_ty(local.pat.hir_id, ty);
3887 let local_ty = LocalTy {
3891 self.locals.borrow_mut().insert(local.hir_id, local_ty);
3892 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
3896 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
3897 err.span_suggestion_short(
3898 span.shrink_to_hi(),
3899 "consider using a semicolon here",
3901 Applicability::MachineApplicable,
3905 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3906 // Don't do all the complex logic below for `DeclItem`.
3908 hir::StmtKind::Item(..) => return,
3909 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3912 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3914 // Hide the outer diverging and `has_errors` flags.
3915 let old_diverges = self.diverges.get();
3916 let old_has_errors = self.has_errors.get();
3917 self.diverges.set(Diverges::Maybe);
3918 self.has_errors.set(false);
3921 hir::StmtKind::Local(ref l) => {
3922 self.check_decl_local(&l);
3925 hir::StmtKind::Item(_) => {}
3926 hir::StmtKind::Expr(ref expr) => {
3927 // Check with expected type of `()`.
3929 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
3930 self.suggest_semicolon_at_end(expr.span, err);
3933 hir::StmtKind::Semi(ref expr) => {
3934 self.check_expr(&expr);
3938 // Combine the diverging and `has_error` flags.
3939 self.diverges.set(self.diverges.get() | old_diverges);
3940 self.has_errors.set(self.has_errors.get() | old_has_errors);
3943 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
3944 let unit = self.tcx.mk_unit();
3945 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
3947 // if the block produces a `!` value, that can always be
3948 // (effectively) coerced to unit.
3950 self.demand_suptype(blk.span, unit, ty);
3954 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
3955 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
3956 /// when given code like the following:
3958 /// if false { return 0i32; } else { 1u32 }
3959 /// // ^^^^ point at this instead of the whole `if` expression
3961 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
3962 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
3963 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
3964 self.in_progress_tables
3965 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
3966 .and_then(|arm_ty| {
3967 if arm_ty.is_never() {
3970 Some(match &arm.body.kind {
3971 // Point at the tail expression when possible.
3972 hir::ExprKind::Block(block, _) => block.expr
3975 .unwrap_or(block.span),
3981 if arm_spans.len() == 1 {
3982 return arm_spans[0];
3988 fn check_block_with_expected(
3990 blk: &'tcx hir::Block,
3991 expected: Expectation<'tcx>,
3994 let mut fcx_ps = self.ps.borrow_mut();
3995 let unsafety_state = fcx_ps.recurse(blk);
3996 replace(&mut *fcx_ps, unsafety_state)
3999 // In some cases, blocks have just one exit, but other blocks
4000 // can be targeted by multiple breaks. This can happen both
4001 // with labeled blocks as well as when we desugar
4002 // a `try { ... }` expression.
4006 // 'a: { if true { break 'a Err(()); } Ok(()) }
4008 // Here we would wind up with two coercions, one from
4009 // `Err(())` and the other from the tail expression
4010 // `Ok(())`. If the tail expression is omitted, that's a
4011 // "forced unit" -- unless the block diverges, in which
4012 // case we can ignore the tail expression (e.g., `'a: {
4013 // break 'a 22; }` would not force the type of the block
4015 let tail_expr = blk.expr.as_ref();
4016 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4017 let coerce = if blk.targeted_by_break {
4018 CoerceMany::new(coerce_to_ty)
4020 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4021 Some(e) => slice::from_ref(e),
4024 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4027 let prev_diverges = self.diverges.get();
4028 let ctxt = BreakableCtxt {
4029 coerce: Some(coerce),
4033 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4034 for s in &blk.stmts {
4038 // check the tail expression **without** holding the
4039 // `enclosing_breakables` lock below.
4040 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4042 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4043 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4044 let coerce = ctxt.coerce.as_mut().unwrap();
4045 if let Some(tail_expr_ty) = tail_expr_ty {
4046 let tail_expr = tail_expr.unwrap();
4047 let span = self.get_expr_coercion_span(tail_expr);
4048 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4049 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4051 // Subtle: if there is no explicit tail expression,
4052 // that is typically equivalent to a tail expression
4053 // of `()` -- except if the block diverges. In that
4054 // case, there is no value supplied from the tail
4055 // expression (assuming there are no other breaks,
4056 // this implies that the type of the block will be
4059 // #41425 -- label the implicit `()` as being the
4060 // "found type" here, rather than the "expected type".
4061 if !self.diverges.get().is_always() {
4062 // #50009 -- Do not point at the entire fn block span, point at the return type
4063 // span, as it is the cause of the requirement, and
4064 // `consider_hint_about_removing_semicolon` will point at the last expression
4065 // if it were a relevant part of the error. This improves usability in editors
4066 // that highlight errors inline.
4067 let mut sp = blk.span;
4068 let mut fn_span = None;
4069 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4070 let ret_sp = decl.output.span();
4071 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4072 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4073 // output would otherwise be incorrect and even misleading. Make sure
4074 // the span we're aiming at correspond to a `fn` body.
4075 if block_sp == blk.span {
4077 fn_span = Some(ident.span);
4081 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4082 if let Some(expected_ty) = expected.only_has_type(self) {
4083 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4085 if let Some(fn_span) = fn_span {
4088 "implicitly returns `()` as its body has no tail or `return` \
4098 // If we can break from the block, then the block's exit is always reachable
4099 // (... as long as the entry is reachable) - regardless of the tail of the block.
4100 self.diverges.set(prev_diverges);
4103 let mut ty = ctxt.coerce.unwrap().complete(self);
4105 if self.has_errors.get() || ty.references_error() {
4106 ty = self.tcx.types.err
4109 self.write_ty(blk.hir_id, ty);
4111 *self.ps.borrow_mut() = prev;
4115 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4116 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4118 Node::Item(&hir::Item {
4119 kind: hir::ItemKind::Fn(_, _, _, body_id), ..
4121 Node::ImplItem(&hir::ImplItem {
4122 kind: hir::ImplItemKind::Method(_, body_id), ..
4124 let body = self.tcx.hir().body(body_id);
4125 if let ExprKind::Block(block, _) = &body.value.kind {
4126 return Some(block.span);
4134 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4135 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
4136 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4137 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4140 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4141 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
4143 Node::Item(&hir::Item {
4144 ident, kind: hir::ItemKind::Fn(ref decl, ..), ..
4146 // This is less than ideal, it will not suggest a return type span on any
4147 // method called `main`, regardless of whether it is actually the entry point,
4148 // but it will still present it as the reason for the expected type.
4149 Some((decl, ident, ident.name != sym::main))
4151 Node::TraitItem(&hir::TraitItem {
4152 ident, kind: hir::TraitItemKind::Method(hir::MethodSig {
4155 }) => Some((decl, ident, true)),
4156 Node::ImplItem(&hir::ImplItem {
4157 ident, kind: hir::ImplItemKind::Method(hir::MethodSig {
4160 }) => Some((decl, ident, false)),
4165 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4166 /// suggestion can be made, `None` otherwise.
4167 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
4168 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4169 // `while` before reaching it, as block tail returns are not available in them.
4170 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4171 let parent = self.tcx.hir().get(blk_id);
4172 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4176 /// On implicit return expressions with mismatched types, provides the following suggestions:
4178 /// - Points out the method's return type as the reason for the expected type.
4179 /// - Possible missing semicolon.
4180 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4181 pub fn suggest_mismatched_types_on_tail(
4183 err: &mut DiagnosticBuilder<'tcx>,
4184 expression: &'tcx hir::Expr,
4190 self.suggest_missing_semicolon(err, expression, expected, cause_span);
4191 let mut pointing_at_return_type = false;
4192 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4193 pointing_at_return_type = self.suggest_missing_return_type(
4194 err, &fn_decl, expected, found, can_suggest);
4196 self.suggest_ref_or_into(err, expression, expected, found);
4197 self.suggest_boxing_when_appropriate(err, expression, expected, found);
4198 pointing_at_return_type
4201 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4202 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4204 /// fn foo(x: usize) -> usize { x }
4205 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4209 err: &mut DiagnosticBuilder<'tcx>,
4214 let hir = self.tcx.hir();
4215 let (def_id, sig) = match found.kind {
4216 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4217 ty::Closure(def_id, substs) => {
4218 // We don't use `closure_sig` to account for malformed closures like
4219 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4220 let closure_sig_ty = substs.as_closure().sig_ty(def_id, self.tcx);
4221 (def_id, match closure_sig_ty.kind {
4222 ty::FnPtr(sig) => sig,
4230 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4232 let sig = self.normalize_associated_types_in(expr.span, &sig);
4233 if self.can_coerce(sig.output(), expected) {
4234 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4235 (String::new(), Applicability::MachineApplicable)
4237 ("...".to_string(), Applicability::HasPlaceholders)
4239 let mut msg = "call this function";
4240 match hir.get_if_local(def_id) {
4241 Some(Node::Item(hir::Item {
4242 kind: ItemKind::Fn(.., body_id),
4245 Some(Node::ImplItem(hir::ImplItem {
4246 kind: hir::ImplItemKind::Method(_, body_id),
4249 Some(Node::TraitItem(hir::TraitItem {
4250 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4253 let body = hir.body(*body_id);
4254 sugg_call = body.params.iter()
4255 .map(|param| match ¶m.pat.kind {
4256 hir::PatKind::Binding(_, _, ident, None)
4257 if ident.name != kw::SelfLower => ident.to_string(),
4258 _ => "_".to_string(),
4259 }).collect::<Vec<_>>().join(", ");
4261 Some(Node::Expr(hir::Expr {
4262 kind: ExprKind::Closure(_, _, body_id, closure_span, _),
4263 span: full_closure_span,
4266 if *full_closure_span == expr.span {
4269 err.span_label(*closure_span, "closure defined here");
4270 msg = "call this closure";
4271 let body = hir.body(*body_id);
4272 sugg_call = body.params.iter()
4273 .map(|param| match ¶m.pat.kind {
4274 hir::PatKind::Binding(_, _, ident, None)
4275 if ident.name != kw::SelfLower => ident.to_string(),
4276 _ => "_".to_string(),
4277 }).collect::<Vec<_>>().join(", ");
4279 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4280 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4281 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4282 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4283 msg = "instantiate this tuple variant";
4285 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4286 msg = "instantiate this tuple struct";
4291 Some(Node::ForeignItem(hir::ForeignItem {
4292 kind: hir::ForeignItemKind::Fn(_, idents, _),
4295 Some(Node::TraitItem(hir::TraitItem {
4296 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4298 })) => sugg_call = idents.iter()
4299 .map(|ident| if ident.name != kw::SelfLower {
4303 }).collect::<Vec<_>>()
4307 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4308 err.span_suggestion(
4310 &format!("use parentheses to {}", msg),
4311 format!("{}({})", code, sugg_call),
4320 pub fn suggest_ref_or_into(
4322 err: &mut DiagnosticBuilder<'tcx>,
4327 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4328 err.span_suggestion(
4332 Applicability::MachineApplicable,
4334 } else if let (ty::FnDef(def_id, ..), true) = (
4336 self.suggest_fn_call(err, expr, expected, found),
4338 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4339 let sp = self.sess().source_map().def_span(sp);
4340 err.span_label(sp, &format!("{} defined here", found));
4342 } else if !self.check_for_cast(err, expr, found, expected) {
4343 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4347 let methods = self.get_conversion_methods(expr.span, expected, found);
4348 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4349 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4350 .filter_map(|(receiver, method)| {
4351 let method_call = format!(".{}()", method.ident);
4352 if receiver.ends_with(&method_call) {
4353 None // do not suggest code that is already there (#53348)
4355 let method_call_list = [".to_vec()", ".to_string()"];
4356 let sugg = if receiver.ends_with(".clone()")
4357 && method_call_list.contains(&method_call.as_str()) {
4358 let max_len = receiver.rfind(".").unwrap();
4359 format!("{}{}", &receiver[..max_len], method_call)
4361 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
4362 format!("({}){}", receiver, method_call)
4364 format!("{}{}", receiver, method_call)
4367 Some(if is_struct_pat_shorthand_field {
4368 format!("{}: {}", receiver, sugg)
4374 if suggestions.peek().is_some() {
4375 err.span_suggestions(
4377 "try using a conversion method",
4379 Applicability::MaybeIncorrect,
4386 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4387 /// in the heap by calling `Box::new()`.
4388 fn suggest_boxing_when_appropriate(
4390 err: &mut DiagnosticBuilder<'tcx>,
4395 if self.tcx.hir().is_const_context(expr.hir_id) {
4396 // Do not suggest `Box::new` in const context.
4399 if !expected.is_box() || found.is_box() {
4402 let boxed_found = self.tcx.mk_box(found);
4403 if let (true, Ok(snippet)) = (
4404 self.can_coerce(boxed_found, expected),
4405 self.sess().source_map().span_to_snippet(expr.span),
4407 err.span_suggestion(
4409 "store this in the heap by calling `Box::new`",
4410 format!("Box::new({})", snippet),
4411 Applicability::MachineApplicable,
4413 err.note("for more on the distinction between the stack and the \
4414 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4415 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4416 https://doc.rust-lang.org/std/boxed/index.html");
4421 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4425 /// bar_that_returns_u32()
4429 /// This routine checks if the return expression in a block would make sense on its own as a
4430 /// statement and the return type has been left as default or has been specified as `()`. If so,
4431 /// it suggests adding a semicolon.
4432 fn suggest_missing_semicolon(
4434 err: &mut DiagnosticBuilder<'tcx>,
4435 expression: &'tcx hir::Expr,
4439 if expected.is_unit() {
4440 // `BlockTailExpression` only relevant if the tail expr would be
4441 // useful on its own.
4442 match expression.kind {
4443 ExprKind::Call(..) |
4444 ExprKind::MethodCall(..) |
4445 ExprKind::Loop(..) |
4446 ExprKind::Match(..) |
4447 ExprKind::Block(..) => {
4448 let sp = self.tcx.sess.source_map().next_point(cause_span);
4449 err.span_suggestion(
4451 "try adding a semicolon",
4453 Applicability::MachineApplicable);
4460 /// A possible error is to forget to add a return type that is needed:
4464 /// bar_that_returns_u32()
4468 /// This routine checks if the return type is left as default, the method is not part of an
4469 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4471 fn suggest_missing_return_type(
4473 err: &mut DiagnosticBuilder<'tcx>,
4474 fn_decl: &hir::FnDecl,
4479 // Only suggest changing the return type for methods that
4480 // haven't set a return type at all (and aren't `fn main()` or an impl).
4481 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4482 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4483 err.span_suggestion(
4485 "try adding a return type",
4486 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
4487 Applicability::MachineApplicable);
4490 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4491 err.span_label(span, "possibly return type missing here?");
4494 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4495 // `fn main()` must return `()`, do not suggest changing return type
4496 err.span_label(span, "expected `()` because of default return type");
4499 // expectation was caused by something else, not the default return
4500 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4501 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4502 // Only point to return type if the expected type is the return type, as if they
4503 // are not, the expectation must have been caused by something else.
4504 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
4506 let ty = AstConv::ast_ty_to_ty(self, ty);
4507 debug!("suggest_missing_return_type: return type {:?}", ty);
4508 debug!("suggest_missing_return_type: expected type {:?}", ty);
4509 if ty.kind == expected.kind {
4510 err.span_label(sp, format!("expected `{}` because of return type",
4519 /// A possible error is to forget to add `.await` when using futures:
4522 /// async fn make_u32() -> u32 {
4526 /// fn take_u32(x: u32) {}
4528 /// async fn foo() {
4529 /// let x = make_u32();
4534 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4535 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4536 /// `.await` to the tail of the expression.
4537 fn suggest_missing_await(
4539 err: &mut DiagnosticBuilder<'tcx>,
4544 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4545 // body isn't `async`.
4546 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4547 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4548 let body = self.tcx().hir().body(body_id);
4549 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
4551 // Check for `Future` implementations by constructing a predicate to
4552 // prove: `<T as Future>::Output == U`
4553 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4554 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4555 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4556 // `<T as Future>::Output`
4557 projection_ty: ty::ProjectionTy {
4559 substs: self.tcx.mk_substs_trait(
4561 self.fresh_substs_for_item(sp, item_def_id)
4568 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4569 if self.infcx.predicate_may_hold(&obligation) {
4570 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4571 err.span_suggestion(
4573 "consider using `.await` here",
4574 format!("{}.await", code),
4575 Applicability::MaybeIncorrect,
4583 /// A common error is to add an extra semicolon:
4586 /// fn foo() -> usize {
4591 /// This routine checks if the final statement in a block is an
4592 /// expression with an explicit semicolon whose type is compatible
4593 /// with `expected_ty`. If so, it suggests removing the semicolon.
4594 fn consider_hint_about_removing_semicolon(
4596 blk: &'tcx hir::Block,
4597 expected_ty: Ty<'tcx>,
4598 err: &mut DiagnosticBuilder<'_>,
4600 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4601 err.span_suggestion(
4603 "consider removing this semicolon",
4605 Applicability::MachineApplicable,
4610 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4611 // Be helpful when the user wrote `{... expr;}` and
4612 // taking the `;` off is enough to fix the error.
4613 let last_stmt = blk.stmts.last()?;
4614 let last_expr = match last_stmt.kind {
4615 hir::StmtKind::Semi(ref e) => e,
4618 let last_expr_ty = self.node_ty(last_expr.hir_id);
4619 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4622 let original_span = original_sp(last_stmt.span, blk.span);
4623 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4626 // Instantiates the given path, which must refer to an item with the given
4627 // number of type parameters and type.
4628 pub fn instantiate_value_path(&self,
4629 segments: &[hir::PathSegment],
4630 self_ty: Option<Ty<'tcx>>,
4634 -> (Ty<'tcx>, Res) {
4636 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4645 let path_segs = match res {
4646 Res::Local(_) | Res::SelfCtor(_) => vec![],
4647 Res::Def(kind, def_id) =>
4648 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4649 _ => bug!("instantiate_value_path on {:?}", res),
4652 let mut user_self_ty = None;
4653 let mut is_alias_variant_ctor = false;
4655 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4656 if let Some(self_ty) = self_ty {
4657 let adt_def = self_ty.ty_adt_def().unwrap();
4658 user_self_ty = Some(UserSelfTy {
4659 impl_def_id: adt_def.did,
4662 is_alias_variant_ctor = true;
4665 Res::Def(DefKind::Method, def_id)
4666 | Res::Def(DefKind::AssocConst, def_id) => {
4667 let container = tcx.associated_item(def_id).container;
4668 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4670 ty::TraitContainer(trait_did) => {
4671 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4673 ty::ImplContainer(impl_def_id) => {
4674 if segments.len() == 1 {
4675 // `<T>::assoc` will end up here, and so
4676 // can `T::assoc`. It this came from an
4677 // inherent impl, we need to record the
4678 // `T` for posterity (see `UserSelfTy` for
4680 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4681 user_self_ty = Some(UserSelfTy {
4692 // Now that we have categorized what space the parameters for each
4693 // segment belong to, let's sort out the parameters that the user
4694 // provided (if any) into their appropriate spaces. We'll also report
4695 // errors if type parameters are provided in an inappropriate place.
4697 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4698 let generics_has_err = AstConv::prohibit_generics(
4699 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4700 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4707 if let Res::Local(hid) = res {
4708 let ty = self.local_ty(span, hid).decl_ty;
4709 let ty = self.normalize_associated_types_in(span, &ty);
4710 self.write_ty(hir_id, ty);
4714 if generics_has_err {
4715 // Don't try to infer type parameters when prohibited generic arguments were given.
4716 user_self_ty = None;
4719 // Now we have to compare the types that the user *actually*
4720 // provided against the types that were *expected*. If the user
4721 // did not provide any types, then we want to substitute inference
4722 // variables. If the user provided some types, we may still need
4723 // to add defaults. If the user provided *too many* types, that's
4726 let mut infer_args_for_err = FxHashSet::default();
4727 for &PathSeg(def_id, index) in &path_segs {
4728 let seg = &segments[index];
4729 let generics = tcx.generics_of(def_id);
4730 // Argument-position `impl Trait` is treated as a normal generic
4731 // parameter internally, but we don't allow users to specify the
4732 // parameter's value explicitly, so we have to do some error-
4734 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4739 false, // `is_method_call`
4741 if suppress_errors {
4742 infer_args_for_err.insert(index);
4743 self.set_tainted_by_errors(); // See issue #53251.
4747 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4748 tcx.generics_of(*def_id).has_self
4749 }).unwrap_or(false);
4751 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4752 let ty = self.impl_self_ty(span, impl_def_id).ty;
4753 let adt_def = ty.ty_adt_def();
4756 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4757 let variant = adt_def.non_enum_variant();
4758 let ctor_def_id = variant.ctor_def_id.unwrap();
4760 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4765 let mut err = tcx.sess.struct_span_err(span,
4766 "the `Self` constructor can only be used with tuple or unit structs");
4767 if let Some(adt_def) = adt_def {
4768 match adt_def.adt_kind() {
4770 err.help("did you mean to use one of the enum's variants?");
4774 err.span_suggestion(
4776 "use curly brackets",
4777 String::from("Self { /* fields */ }"),
4778 Applicability::HasPlaceholders,
4785 return (tcx.types.err, res)
4791 let def_id = res.def_id();
4793 // The things we are substituting into the type should not contain
4794 // escaping late-bound regions, and nor should the base type scheme.
4795 let ty = tcx.type_of(def_id);
4797 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4803 // Provide the generic args, and whether types should be inferred.
4805 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4808 // If we've encountered an `impl Trait`-related error, we're just
4809 // going to infer the arguments for better error messages.
4810 if !infer_args_for_err.contains(&index) {
4811 // Check whether the user has provided generic arguments.
4812 if let Some(ref data) = segments[index].args {
4813 return (Some(data), segments[index].infer_args);
4816 return (None, segments[index].infer_args);
4821 // Provide substitutions for parameters for which (valid) arguments have been provided.
4823 match (¶m.kind, arg) {
4824 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4825 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4827 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4828 self.to_ty(ty).into()
4830 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4831 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4833 _ => unreachable!(),
4836 // Provide substitutions for parameters for which arguments are inferred.
4837 |substs, param, infer_args| {
4839 GenericParamDefKind::Lifetime => {
4840 self.re_infer(Some(param), span).unwrap().into()
4842 GenericParamDefKind::Type { has_default, .. } => {
4843 if !infer_args && has_default {
4844 // If we have a default, then we it doesn't matter that we're not
4845 // inferring the type arguments: we provide the default where any
4847 let default = tcx.type_of(param.def_id);
4850 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4853 // If no type arguments were provided, we have to infer them.
4854 // This case also occurs as a result of some malformed input, e.g.
4855 // a lifetime argument being given instead of a type parameter.
4856 // Using inference instead of `Error` gives better error messages.
4857 self.var_for_def(span, param)
4860 GenericParamDefKind::Const => {
4861 // FIXME(const_generics:defaults)
4862 // No const parameters were provided, we have to infer them.
4863 self.var_for_def(span, param)
4868 assert!(!substs.has_escaping_bound_vars());
4869 assert!(!ty.has_escaping_bound_vars());
4871 // First, store the "user substs" for later.
4872 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4874 self.add_required_obligations(span, def_id, &substs);
4876 // Substitute the values for the type parameters into the type of
4877 // the referenced item.
4878 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4880 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4881 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4882 // is inherent, there is no `Self` parameter; instead, the impl needs
4883 // type parameters, which we can infer by unifying the provided `Self`
4884 // with the substituted impl type.
4885 // This also occurs for an enum variant on a type alias.
4886 let ty = tcx.type_of(impl_def_id);
4888 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4889 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4890 Ok(ok) => self.register_infer_ok_obligations(ok),
4892 self.tcx.sess.delay_span_bug(span, &format!(
4893 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4901 self.check_rustc_args_require_const(def_id, hir_id, span);
4903 debug!("instantiate_value_path: type of {:?} is {:?}",
4906 self.write_substs(hir_id, substs);
4908 (ty_substituted, res)
4911 /// Add all the obligations that are required, substituting and normalized appropriately.
4912 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
4913 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
4915 for (i, mut obligation) in traits::predicates_for_generics(
4916 traits::ObligationCause::new(
4919 traits::ItemObligation(def_id),
4923 ).into_iter().enumerate() {
4924 // This makes the error point at the bound, but we want to point at the argument
4925 if let Some(span) = spans.get(i) {
4926 obligation.cause.code = traits::BindingObligation(def_id, *span);
4928 self.register_predicate(obligation);
4932 fn check_rustc_args_require_const(&self,
4936 // We're only interested in functions tagged with
4937 // #[rustc_args_required_const], so ignore anything that's not.
4938 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
4942 // If our calling expression is indeed the function itself, we're good!
4943 // If not, generate an error that this can only be called directly.
4944 if let Node::Expr(expr) = self.tcx.hir().get(
4945 self.tcx.hir().get_parent_node(hir_id))
4947 if let ExprKind::Call(ref callee, ..) = expr.kind {
4948 if callee.hir_id == hir_id {
4954 self.tcx.sess.span_err(span, "this function can only be invoked \
4955 directly, not through a function pointer");
4958 // Resolves `typ` by a single level if `typ` is a type variable.
4959 // If no resolution is possible, then an error is reported.
4960 // Numeric inference variables may be left unresolved.
4961 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4962 let ty = self.resolve_type_vars_with_obligations(ty);
4963 if !ty.is_ty_var() {
4966 if !self.is_tainted_by_errors() {
4967 self.need_type_info_err((**self).body_id, sp, ty)
4968 .note("type must be known at this point")
4971 self.demand_suptype(sp, self.tcx.types.err, ty);
4976 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
4979 ctxt: BreakableCtxt<'tcx>,
4981 ) -> (BreakableCtxt<'tcx>, R) {
4984 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4985 index = enclosing_breakables.stack.len();
4986 enclosing_breakables.by_id.insert(id, index);
4987 enclosing_breakables.stack.push(ctxt);
4991 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4992 debug_assert!(enclosing_breakables.stack.len() == index + 1);
4993 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
4994 enclosing_breakables.stack.pop().expect("missing breakable context")
4999 /// Instantiate a QueryResponse in a probe context, without a
5000 /// good ObligationCause.
5001 fn probe_instantiate_query_response(
5004 original_values: &OriginalQueryValues<'tcx>,
5005 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5006 ) -> InferResult<'tcx, Ty<'tcx>>
5008 self.instantiate_query_response_and_region_obligations(
5009 &traits::ObligationCause::misc(span, self.body_id),
5015 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5016 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5017 let mut contained_in_place = false;
5019 while let hir::Node::Expr(parent_expr) =
5020 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5022 match &parent_expr.kind {
5023 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5024 if lhs.hir_id == expr_id {
5025 contained_in_place = true;
5031 expr_id = parent_expr.hir_id;
5038 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5039 let own_counts = generics.own_counts();
5041 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5047 if own_counts.types == 0 {
5051 // Make a vector of booleans initially `false`; set to `true` when used.
5052 let mut types_used = vec![false; own_counts.types];
5054 for leaf_ty in ty.walk() {
5055 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.kind {
5056 debug!("found use of ty param num {}", index);
5057 types_used[index as usize - own_counts.lifetimes] = true;
5058 } else if let ty::Error = leaf_ty.kind {
5059 // If there is already another error, do not emit
5060 // an error for not using a type parameter.
5061 assert!(tcx.sess.has_errors());
5066 let types = generics.params.iter().filter(|param| match param.kind {
5067 ty::GenericParamDefKind::Type { .. } => true,
5070 for (&used, param) in types_used.iter().zip(types) {
5072 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5073 let span = tcx.hir().span(id);
5074 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5075 .span_label(span, "unused type parameter")
5081 fn fatally_break_rust(sess: &Session) {
5082 let handler = sess.diagnostic();
5083 handler.span_bug_no_panic(
5085 "It looks like you're trying to break rust; would you like some ICE?",
5087 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5088 handler.note_without_error(
5089 "we would appreciate a joke overview: \
5090 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5092 handler.note_without_error(&format!("rustc {} running on {}",
5093 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5094 crate::session::config::host_triple(),
5098 fn potentially_plural_count(count: usize, word: &str) -> String {
5099 format!("{} {}{}", count, word, pluralise!(count))