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 kind = match impl_item.kind {
1717 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1718 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1719 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1720 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1723 let mut ancestor_impls = trait_def.ancestors(tcx, impl_id)
1725 .filter_map(|parent| {
1726 if parent.is_from_trait() {
1729 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
1734 if ancestor_impls.peek().is_none() {
1735 // No parent, nothing to specialize.
1739 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
1741 // Parent impl exists, and contains the parent item we're trying to specialize, but
1742 // doesn't mark it `default`.
1743 Some(parent_item) if tcx.impl_item_is_final(&parent_item) => {
1744 Some(Err(parent_impl.def_id()))
1747 // Parent impl contains item and makes it specializable.
1752 // Parent impl doesn't mention the item. This means it's inherited from the
1753 // grandparent. In that case, if parent is a `default impl`, inherited items use the
1754 // "defaultness" from the grandparent, else they are final.
1755 None => if tcx.impl_is_default(parent_impl.def_id()) {
1758 Some(Err(parent_impl.def_id()))
1763 // If `opt_result` is `None`, we have only encoutered `default impl`s that don't contain the
1764 // item. This is allowed, the item isn't actually getting specialized here.
1765 let result = opt_result.unwrap_or(Ok(()));
1767 if let Err(parent_impl) = result {
1768 report_forbidden_specialization(tcx, impl_item, parent_impl);
1772 fn check_impl_items_against_trait<'tcx>(
1776 impl_trait_ref: ty::TraitRef<'tcx>,
1777 impl_item_refs: &[hir::ImplItemRef],
1779 let impl_span = tcx.sess.source_map().def_span(impl_span);
1781 // If the trait reference itself is erroneous (so the compilation is going
1782 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1783 // isn't populated for such impls.
1784 if impl_trait_ref.references_error() { return; }
1786 // Locate trait definition and items
1787 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1788 let mut overridden_associated_type = None;
1790 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1792 // Check existing impl methods to see if they are both present in trait
1793 // and compatible with trait signature
1794 for impl_item in impl_items() {
1795 let ty_impl_item = tcx.associated_item(
1796 tcx.hir().local_def_id(impl_item.hir_id));
1797 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1798 .find(|ac| Namespace::from(&impl_item.kind) == Namespace::from(ac.kind) &&
1799 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1801 // Not compatible, but needed for the error message
1802 tcx.associated_items(impl_trait_ref.def_id)
1803 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1806 // Check that impl definition matches trait definition
1807 if let Some(ty_trait_item) = ty_trait_item {
1808 match impl_item.kind {
1809 hir::ImplItemKind::Const(..) => {
1810 // Find associated const definition.
1811 if ty_trait_item.kind == ty::AssocKind::Const {
1812 compare_const_impl(tcx,
1818 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1819 "item `{}` is an associated const, \
1820 which doesn't match its trait `{}`",
1823 err.span_label(impl_item.span, "does not match trait");
1824 // We can only get the spans from local trait definition
1825 // Same for E0324 and E0325
1826 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1827 err.span_label(trait_span, "item in trait");
1832 hir::ImplItemKind::Method(..) => {
1833 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1834 if ty_trait_item.kind == ty::AssocKind::Method {
1835 compare_impl_method(tcx,
1842 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1843 "item `{}` is an associated method, \
1844 which doesn't match its trait `{}`",
1847 err.span_label(impl_item.span, "does not match trait");
1848 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1849 err.span_label(trait_span, "item in trait");
1854 hir::ImplItemKind::OpaqueTy(..) |
1855 hir::ImplItemKind::TyAlias(_) => {
1856 if ty_trait_item.kind == ty::AssocKind::Type {
1857 if ty_trait_item.defaultness.has_value() {
1858 overridden_associated_type = Some(impl_item);
1861 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1862 "item `{}` is an associated type, \
1863 which doesn't match its trait `{}`",
1866 err.span_label(impl_item.span, "does not match trait");
1867 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1868 err.span_label(trait_span, "item in trait");
1875 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1879 // Check for missing items from trait
1880 let mut missing_items = Vec::new();
1881 let mut invalidated_items = Vec::new();
1882 let associated_type_overridden = overridden_associated_type.is_some();
1883 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1884 let is_implemented = trait_def.ancestors(tcx, impl_id)
1885 .leaf_def(tcx, trait_item.ident, trait_item.kind)
1886 .map(|node_item| !node_item.node.is_from_trait())
1889 if !is_implemented && !tcx.impl_is_default(impl_id) {
1890 if !trait_item.defaultness.has_value() {
1891 missing_items.push(trait_item);
1892 } else if associated_type_overridden {
1893 invalidated_items.push(trait_item.ident);
1898 if !missing_items.is_empty() {
1899 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1900 "not all trait items implemented, missing: `{}`",
1901 missing_items.iter()
1902 .map(|trait_item| trait_item.ident.to_string())
1903 .collect::<Vec<_>>().join("`, `"));
1904 err.span_label(impl_span, format!("missing `{}` in implementation",
1905 missing_items.iter()
1906 .map(|trait_item| trait_item.ident.to_string())
1907 .collect::<Vec<_>>().join("`, `")));
1908 for trait_item in missing_items {
1909 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1910 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1912 err.note_trait_signature(trait_item.ident.to_string(),
1913 trait_item.signature(tcx));
1919 if !invalidated_items.is_empty() {
1920 let invalidator = overridden_associated_type.unwrap();
1921 span_err!(tcx.sess, invalidator.span, E0399,
1922 "the following trait items need to be reimplemented \
1923 as `{}` was overridden: `{}`",
1925 invalidated_items.iter()
1926 .map(|name| name.to_string())
1927 .collect::<Vec<_>>().join("`, `"))
1931 /// Checks whether a type can be represented in memory. In particular, it
1932 /// identifies types that contain themselves without indirection through a
1933 /// pointer, which would mean their size is unbounded.
1934 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
1935 let rty = tcx.type_of(item_def_id);
1937 // Check that it is possible to represent this type. This call identifies
1938 // (1) types that contain themselves and (2) types that contain a different
1939 // recursive type. It is only necessary to throw an error on those that
1940 // contain themselves. For case 2, there must be an inner type that will be
1941 // caught by case 1.
1942 match rty.is_representable(tcx, sp) {
1943 Representability::SelfRecursive(spans) => {
1944 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1946 err.span_label(span, "recursive without indirection");
1951 Representability::Representable | Representability::ContainsRecursive => (),
1956 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1957 let t = tcx.type_of(def_id);
1958 if let ty::Adt(def, substs) = t.kind {
1959 if def.is_struct() {
1960 let fields = &def.non_enum_variant().fields;
1961 if fields.is_empty() {
1962 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1965 let e = fields[0].ty(tcx, substs);
1966 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1967 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1968 .span_label(sp, "SIMD elements must have the same type")
1973 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1974 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1976 span_err!(tcx.sess, sp, E0077,
1977 "SIMD vector element type should be machine type");
1985 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1986 let repr = tcx.adt_def(def_id).repr;
1988 for attr in tcx.get_attrs(def_id).iter() {
1989 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
1990 if let attr::ReprPacked(pack) = r {
1991 if let Some(repr_pack) = repr.pack {
1992 if pack as u64 != repr_pack.bytes() {
1994 tcx.sess, sp, E0634,
1995 "type has conflicting packed representation hints"
2002 if repr.align.is_some() {
2003 struct_span_err!(tcx.sess, sp, E0587,
2004 "type has conflicting packed and align representation hints").emit();
2006 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
2007 struct_span_err!(tcx.sess, sp, E0588,
2008 "packed type cannot transitively contain a `[repr(align)]` type").emit();
2013 fn check_packed_inner(tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec<DefId>) -> bool {
2014 let t = tcx.type_of(def_id);
2015 if stack.contains(&def_id) {
2016 debug!("check_packed_inner: {:?} is recursive", t);
2019 if let ty::Adt(def, substs) = t.kind {
2020 if def.is_struct() || def.is_union() {
2021 if tcx.adt_def(def.did).repr.align.is_some() {
2024 // push struct def_id before checking fields
2026 for field in &def.non_enum_variant().fields {
2027 let f = field.ty(tcx, substs);
2028 if let ty::Adt(def, _) = f.kind {
2029 if check_packed_inner(tcx, def.did, stack) {
2034 // only need to pop if not early out
2041 /// Emit an error when encountering more or less than one variant in a transparent enum.
2042 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2043 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
2044 tcx.hir().span_if_local(variant.def_id).unwrap()
2047 "needs exactly one variant, but has {}",
2050 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2051 err.span_label(sp, &msg);
2052 if let &[ref start @ .., ref end] = &variant_spans[..] {
2053 for variant_span in start {
2054 err.span_label(*variant_span, "");
2056 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2061 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2063 fn bad_non_zero_sized_fields<'tcx>(
2065 adt: &'tcx ty::AdtDef,
2067 field_spans: impl Iterator<Item = Span>,
2070 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2071 let mut err = struct_span_err!(
2075 "{}transparent {} {}",
2076 if adt.is_enum() { "the variant of a " } else { "" },
2080 err.span_label(sp, &msg);
2081 for sp in field_spans {
2082 err.span_label(sp, "this field is non-zero-sized");
2087 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2088 let adt = tcx.adt_def(def_id);
2089 if !adt.repr.transparent() {
2092 let sp = tcx.sess.source_map().def_span(sp);
2095 if !tcx.features().transparent_enums {
2097 &tcx.sess.parse_sess,
2098 sym::transparent_enums,
2100 GateIssue::Language,
2101 "transparent enums are unstable",
2104 if adt.variants.len() != 1 {
2105 bad_variant_count(tcx, adt, sp, def_id);
2106 if adt.variants.is_empty() {
2107 // Don't bother checking the fields. No variants (and thus no fields) exist.
2113 if adt.is_union() && !tcx.features().transparent_unions {
2114 emit_feature_err(&tcx.sess.parse_sess,
2115 sym::transparent_unions,
2117 GateIssue::Language,
2118 "transparent unions are unstable");
2121 // For each field, figure out if it's known to be a ZST and align(1)
2122 let field_infos = adt.all_fields().map(|field| {
2123 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2124 let param_env = tcx.param_env(field.did);
2125 let layout = tcx.layout_of(param_env.and(ty));
2126 // We are currently checking the type this field came from, so it must be local
2127 let span = tcx.hir().span_if_local(field.did).unwrap();
2128 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2129 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2133 let non_zst_fields = field_infos.clone().filter_map(|(span, zst, _align1)| if !zst {
2138 let non_zst_count = non_zst_fields.clone().count();
2139 if non_zst_count != 1 {
2140 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2142 for (span, zst, align1) in field_infos {
2148 "zero-sized field in transparent {} has alignment larger than 1",
2150 ).span_label(span, "has alignment larger than 1").emit();
2155 #[allow(trivial_numeric_casts)]
2156 pub fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, vs: &'tcx [hir::Variant], id: hir::HirId) {
2157 let def_id = tcx.hir().local_def_id(id);
2158 let def = tcx.adt_def(def_id);
2159 def.destructor(tcx); // force the destructor to be evaluated
2162 let attributes = tcx.get_attrs(def_id);
2163 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2165 tcx.sess, attr.span, E0084,
2166 "unsupported representation for zero-variant enum")
2167 .span_label(sp, "zero-variant enum")
2172 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2173 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2174 if !tcx.features().repr128 {
2175 emit_feature_err(&tcx.sess.parse_sess,
2178 GateIssue::Language,
2179 "repr with 128-bit type is unstable");
2184 if let Some(ref e) = v.disr_expr {
2185 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2189 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2191 |var: &hir::Variant| match var.data {
2192 hir::VariantData::Unit(..) => true,
2196 let has_disr = |var: &hir::Variant| var.disr_expr.is_some();
2197 let has_non_units = vs.iter().any(|var| !is_unit(var));
2198 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2199 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2201 if disr_non_unit || (disr_units && has_non_units) {
2202 let mut err = struct_span_err!(tcx.sess, sp, E0732,
2203 "`#[repr(inttype)]` must be specified");
2208 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2209 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2210 // Check for duplicate discriminant values
2211 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2212 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2213 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2214 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2215 let i_span = match variant_i.disr_expr {
2216 Some(ref expr) => tcx.hir().span(expr.hir_id),
2217 None => tcx.hir().span(variant_i_hir_id)
2219 let span = match v.disr_expr {
2220 Some(ref expr) => tcx.hir().span(expr.hir_id),
2223 struct_span_err!(tcx.sess, span, E0081,
2224 "discriminant value `{}` already exists", disr_vals[i])
2225 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2226 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
2229 disr_vals.push(discr);
2232 check_representable(tcx, sp, def_id);
2233 check_transparent(tcx, sp, def_id);
2236 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span, qpath: &QPath) {
2237 span_err!(tcx.sess, span, E0533,
2238 "expected unit struct/variant or constant, found {} `{}`",
2240 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
2243 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2244 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2248 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
2249 -> &'tcx ty::GenericPredicates<'tcx>
2252 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2253 let item_id = tcx.hir().ty_param_owner(hir_id);
2254 let item_def_id = tcx.hir().local_def_id(item_id);
2255 let generics = tcx.generics_of(item_def_id);
2256 let index = generics.param_def_id_to_index[&def_id];
2257 tcx.arena.alloc(ty::GenericPredicates {
2259 predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
2261 ty::Predicate::Trait(ref data)
2262 if data.skip_binder().self_ty().is_param(index) => {
2263 // HACK(eddyb) should get the original `Span`.
2264 let span = tcx.def_span(def_id);
2265 Some((predicate, span))
2275 def: Option<&ty::GenericParamDef>,
2277 ) -> Option<ty::Region<'tcx>> {
2279 Some(def) => infer::EarlyBoundRegion(span, def.name),
2280 None => infer::MiscVariable(span)
2282 Some(self.next_region_var(v))
2285 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2286 if let Some(param) = param {
2287 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2292 self.next_ty_var(TypeVariableOrigin {
2293 kind: TypeVariableOriginKind::TypeInference,
2302 param: Option<&ty::GenericParamDef>,
2304 ) -> &'tcx Const<'tcx> {
2305 if let Some(param) = param {
2306 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2311 self.next_const_var(ty, ConstVariableOrigin {
2312 kind: ConstVariableOriginKind::ConstInference,
2318 fn projected_ty_from_poly_trait_ref(&self,
2321 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2324 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2326 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2330 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2333 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2334 if ty.has_escaping_bound_vars() {
2335 ty // FIXME: normalization and escaping regions
2337 self.normalize_associated_types_in(span, &ty)
2341 fn set_tainted_by_errors(&self) {
2342 self.infcx.set_tainted_by_errors()
2345 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2346 self.write_ty(hir_id, ty)
2350 /// Controls whether the arguments are tupled. This is used for the call
2353 /// Tupling means that all call-side arguments are packed into a tuple and
2354 /// passed as a single parameter. For example, if tupling is enabled, this
2357 /// fn f(x: (isize, isize))
2359 /// Can be called as:
2366 #[derive(Clone, Eq, PartialEq)]
2367 enum TupleArgumentsFlag {
2372 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2374 inh: &'a Inherited<'a, 'tcx>,
2375 param_env: ty::ParamEnv<'tcx>,
2376 body_id: hir::HirId,
2377 ) -> FnCtxt<'a, 'tcx> {
2381 err_count_on_creation: inh.tcx.sess.err_count(),
2383 ret_coercion_span: RefCell::new(None),
2385 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2386 hir::CRATE_HIR_ID)),
2387 diverges: Cell::new(Diverges::Maybe),
2388 has_errors: Cell::new(false),
2389 enclosing_breakables: RefCell::new(EnclosingBreakables {
2391 by_id: Default::default(),
2397 pub fn sess(&self) -> &Session {
2401 pub fn errors_reported_since_creation(&self) -> bool {
2402 self.tcx.sess.err_count() > self.err_count_on_creation
2405 /// Produces warning on the given node, if the current point in the
2406 /// function is unreachable, and there hasn't been another warning.
2407 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2408 // FIXME: Combine these two 'if' expressions into one once
2409 // let chains are implemented
2410 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2411 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2412 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2413 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2414 if !span.is_desugaring(DesugaringKind::CondTemporary) &&
2415 !span.is_desugaring(DesugaringKind::Async) &&
2416 !orig_span.is_desugaring(DesugaringKind::Await)
2418 self.diverges.set(Diverges::WarnedAlways);
2420 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2422 let msg = format!("unreachable {}", kind);
2423 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2424 .span_label(span, &msg)
2427 custom_note.unwrap_or("any code following this expression is unreachable"),
2436 code: ObligationCauseCode<'tcx>)
2437 -> ObligationCause<'tcx> {
2438 ObligationCause::new(span, self.body_id, code)
2441 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2442 self.cause(span, ObligationCauseCode::MiscObligation)
2445 /// Resolves type variables in `ty` if possible. Unlike the infcx
2446 /// version (resolve_vars_if_possible), this version will
2447 /// also select obligations if it seems useful, in an effort
2448 /// to get more type information.
2449 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2450 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2452 // No Infer()? Nothing needs doing.
2453 if !ty.has_infer_types() {
2454 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2458 // If `ty` is a type variable, see whether we already know what it is.
2459 ty = self.resolve_vars_if_possible(&ty);
2460 if !ty.has_infer_types() {
2461 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2465 // If not, try resolving pending obligations as much as
2466 // possible. This can help substantially when there are
2467 // indirect dependencies that don't seem worth tracking
2469 self.select_obligations_where_possible(false, |_| {});
2470 ty = self.resolve_vars_if_possible(&ty);
2472 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2476 fn record_deferred_call_resolution(
2478 closure_def_id: DefId,
2479 r: DeferredCallResolution<'tcx>,
2481 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2482 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2485 fn remove_deferred_call_resolutions(
2487 closure_def_id: DefId,
2488 ) -> Vec<DeferredCallResolution<'tcx>> {
2489 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2490 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2493 pub fn tag(&self) -> String {
2494 format!("{:p}", self)
2497 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2498 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2499 span_bug!(span, "no type for local variable {}",
2500 self.tcx.hir().node_to_string(nid))
2505 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2506 debug!("write_ty({:?}, {:?}) in fcx {}",
2507 id, self.resolve_vars_if_possible(&ty), self.tag());
2508 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2510 if ty.references_error() {
2511 self.has_errors.set(true);
2512 self.set_tainted_by_errors();
2516 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2517 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2520 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2521 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2524 pub fn write_method_call(&self,
2526 method: MethodCallee<'tcx>) {
2527 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2528 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2529 self.write_substs(hir_id, method.substs);
2531 // When the method is confirmed, the `method.substs` includes
2532 // parameters from not just the method, but also the impl of
2533 // the method -- in particular, the `Self` type will be fully
2534 // resolved. However, those are not something that the "user
2535 // specified" -- i.e., those types come from the inferred type
2536 // of the receiver, not something the user wrote. So when we
2537 // create the user-substs, we want to replace those earlier
2538 // types with just the types that the user actually wrote --
2539 // that is, those that appear on the *method itself*.
2541 // As an example, if the user wrote something like
2542 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2543 // type of `foo` (possibly adjusted), but we don't want to
2544 // include that. We want just the `[_, u32]` part.
2545 if !method.substs.is_noop() {
2546 let method_generics = self.tcx.generics_of(method.def_id);
2547 if !method_generics.params.is_empty() {
2548 let user_type_annotation = self.infcx.probe(|_| {
2549 let user_substs = UserSubsts {
2550 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2551 let i = param.index as usize;
2552 if i < method_generics.parent_count {
2553 self.infcx.var_for_def(DUMMY_SP, param)
2558 user_self_ty: None, // not relevant here
2561 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2567 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2568 self.write_user_type_annotation(hir_id, user_type_annotation);
2573 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2574 if !substs.is_noop() {
2575 debug!("write_substs({:?}, {:?}) in fcx {}",
2580 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2584 /// Given the substs that we just converted from the HIR, try to
2585 /// canonicalize them and store them as user-given substitutions
2586 /// (i.e., substitutions that must be respected by the NLL check).
2588 /// This should be invoked **before any unifications have
2589 /// occurred**, so that annotations like `Vec<_>` are preserved
2591 pub fn write_user_type_annotation_from_substs(
2595 substs: SubstsRef<'tcx>,
2596 user_self_ty: Option<UserSelfTy<'tcx>>,
2599 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2600 user_self_ty={:?} in fcx {}",
2601 hir_id, def_id, substs, user_self_ty, self.tag(),
2604 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2605 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2606 &UserType::TypeOf(def_id, UserSubsts {
2611 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2612 self.write_user_type_annotation(hir_id, canonicalized);
2616 pub fn write_user_type_annotation(
2619 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2622 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2623 hir_id, canonical_user_type_annotation, self.tag(),
2626 if !canonical_user_type_annotation.is_identity() {
2627 self.tables.borrow_mut().user_provided_types_mut().insert(
2628 hir_id, canonical_user_type_annotation
2631 debug!("write_user_type_annotation: skipping identity substs");
2635 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2636 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2642 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2643 Entry::Vacant(entry) => { entry.insert(adj); },
2644 Entry::Occupied(mut entry) => {
2645 debug!(" - composing on top of {:?}", entry.get());
2646 match (&entry.get()[..], &adj[..]) {
2647 // Applying any adjustment on top of a NeverToAny
2648 // is a valid NeverToAny adjustment, because it can't
2650 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2652 Adjustment { kind: Adjust::Deref(_), .. },
2653 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2655 Adjustment { kind: Adjust::Deref(_), .. },
2656 .. // Any following adjustments are allowed.
2658 // A reborrow has no effect before a dereference.
2660 // FIXME: currently we never try to compose autoderefs
2661 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2663 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2664 expr, entry.get(), adj)
2666 *entry.get_mut() = adj;
2671 /// Basically whenever we are converting from a type scheme into
2672 /// the fn body space, we always want to normalize associated
2673 /// types as well. This function combines the two.
2674 fn instantiate_type_scheme<T>(&self,
2676 substs: SubstsRef<'tcx>,
2679 where T : TypeFoldable<'tcx>
2681 let value = value.subst(self.tcx, substs);
2682 let result = self.normalize_associated_types_in(span, &value);
2683 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2690 /// As `instantiate_type_scheme`, but for the bounds found in a
2691 /// generic type scheme.
2692 fn instantiate_bounds(
2696 substs: SubstsRef<'tcx>,
2697 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
2698 let bounds = self.tcx.predicates_of(def_id);
2699 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
2700 let result = bounds.instantiate(self.tcx, substs);
2701 let result = self.normalize_associated_types_in(span, &result);
2703 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
2712 /// Replaces the opaque types from the given value with type variables,
2713 /// and records the `OpaqueTypeMap` for later use during writeback. See
2714 /// `InferCtxt::instantiate_opaque_types` for more details.
2715 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2717 parent_id: hir::HirId,
2721 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2722 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2726 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2727 self.instantiate_opaque_types(
2736 let mut opaque_types = self.opaque_types.borrow_mut();
2737 for (ty, decl) in opaque_type_map {
2738 let old_value = opaque_types.insert(ty, decl);
2739 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2745 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2746 where T : TypeFoldable<'tcx>
2748 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2751 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2753 where T : TypeFoldable<'tcx>
2755 self.inh.partially_normalize_associated_types_in(span,
2761 pub fn require_type_meets(&self,
2764 code: traits::ObligationCauseCode<'tcx>,
2767 self.register_bound(
2770 traits::ObligationCause::new(span, self.body_id, code));
2773 pub fn require_type_is_sized(
2777 code: traits::ObligationCauseCode<'tcx>,
2779 if !ty.references_error() {
2780 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2781 self.require_type_meets(ty, span, code, lang_item);
2785 pub fn require_type_is_sized_deferred(
2789 code: traits::ObligationCauseCode<'tcx>,
2791 if !ty.references_error() {
2792 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2796 pub fn register_bound(
2800 cause: traits::ObligationCause<'tcx>,
2802 if !ty.references_error() {
2803 self.fulfillment_cx.borrow_mut()
2804 .register_bound(self, self.param_env, ty, def_id, cause);
2808 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2809 let t = AstConv::ast_ty_to_ty(self, ast_t);
2810 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2814 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2815 let ty = self.to_ty(ast_ty);
2816 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2818 if Self::can_contain_user_lifetime_bounds(ty) {
2819 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2820 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2821 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2827 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2828 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2829 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2832 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2833 AstConv::ast_const_to_const(self, ast_c, ty)
2836 // If the type given by the user has free regions, save it for later, since
2837 // NLL would like to enforce those. Also pass in types that involve
2838 // projections, since those can resolve to `'static` bounds (modulo #54940,
2839 // which hopefully will be fixed by the time you see this comment, dear
2840 // reader, although I have my doubts). Also pass in types with inference
2841 // types, because they may be repeated. Other sorts of things are already
2842 // sufficiently enforced with erased regions. =)
2843 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2845 T: TypeFoldable<'tcx>
2847 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2850 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2851 match self.tables.borrow().node_types().get(id) {
2853 None if self.is_tainted_by_errors() => self.tcx.types.err,
2855 bug!("no type for node {}: {} in fcx {}",
2856 id, self.tcx.hir().node_to_string(id),
2862 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2863 /// outlive the region `r`.
2864 pub fn register_wf_obligation(
2868 code: traits::ObligationCauseCode<'tcx>,
2870 // WF obligations never themselves fail, so no real need to give a detailed cause:
2871 let cause = traits::ObligationCause::new(span, self.body_id, code);
2872 self.register_predicate(
2873 traits::Obligation::new(cause, self.param_env, ty::Predicate::WellFormed(ty)),
2877 /// Registers obligations that all types appearing in `substs` are well-formed.
2878 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2879 for ty in substs.types() {
2880 if !ty.references_error() {
2881 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2886 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2887 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2888 /// trait/region obligations.
2890 /// For example, if there is a function:
2893 /// fn foo<'a,T:'a>(...)
2896 /// and a reference:
2902 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2903 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2904 pub fn add_obligations_for_parameters(&self,
2905 cause: traits::ObligationCause<'tcx>,
2906 predicates: &ty::InstantiatedPredicates<'tcx>)
2908 assert!(!predicates.has_escaping_bound_vars());
2910 debug!("add_obligations_for_parameters(predicates={:?})",
2913 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2914 self.register_predicate(obligation);
2918 // FIXME(arielb1): use this instead of field.ty everywhere
2919 // Only for fields! Returns <none> for methods>
2920 // Indifferent to privacy flags
2924 field: &'tcx ty::FieldDef,
2925 substs: SubstsRef<'tcx>,
2927 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2930 fn check_casts(&self) {
2931 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2932 for cast in deferred_cast_checks.drain(..) {
2937 fn resolve_generator_interiors(&self, def_id: DefId) {
2938 let mut generators = self.deferred_generator_interiors.borrow_mut();
2939 for (body_id, interior, kind) in generators.drain(..) {
2940 self.select_obligations_where_possible(false, |_| {});
2941 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2945 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2946 // Non-numerics get replaced with ! or () (depending on whether
2947 // feature(never_type) is enabled, unconstrained ints with i32,
2948 // unconstrained floats with f64.
2949 // Fallback becomes very dubious if we have encountered type-checking errors.
2950 // In that case, fallback to Error.
2951 // The return value indicates whether fallback has occurred.
2952 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2953 use rustc::ty::error::UnconstrainedNumeric::Neither;
2954 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2956 assert!(ty.is_ty_infer());
2957 let fallback = match self.type_is_unconstrained_numeric(ty) {
2958 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2959 UnconstrainedInt => self.tcx.types.i32,
2960 UnconstrainedFloat => self.tcx.types.f64,
2961 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2962 Neither => return false,
2964 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2965 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2969 fn select_all_obligations_or_error(&self) {
2970 debug!("select_all_obligations_or_error");
2971 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2972 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2976 /// Select as many obligations as we can at present.
2977 fn select_obligations_where_possible(
2979 fallback_has_occurred: bool,
2980 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
2982 if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2983 mutate_fullfillment_errors(&mut errors);
2984 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2988 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2989 /// returns a type of `&T`, but the actual type we assign to the
2990 /// *expression* is `T`. So this function just peels off the return
2991 /// type by one layer to yield `T`.
2992 fn make_overloaded_place_return_type(&self,
2993 method: MethodCallee<'tcx>)
2994 -> ty::TypeAndMut<'tcx>
2996 // extract method return type, which will be &T;
2997 let ret_ty = method.sig.output();
2999 // method returns &T, but the type as visible to user is T, so deref
3000 ret_ty.builtin_deref(true).unwrap()
3006 base_expr: &'tcx hir::Expr,
3010 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3011 // FIXME(#18741) -- this is almost but not quite the same as the
3012 // autoderef that normal method probing does. They could likely be
3015 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3016 let mut result = None;
3017 while result.is_none() && autoderef.next().is_some() {
3018 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3020 autoderef.finalize(self);
3024 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3025 /// (and otherwise adjust) `base_expr`, looking for a type which either
3026 /// supports builtin indexing or overloaded indexing.
3027 /// This loop implements one step in that search; the autoderef loop
3028 /// is implemented by `lookup_indexing`.
3032 base_expr: &hir::Expr,
3033 autoderef: &Autoderef<'a, 'tcx>,
3036 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3037 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3038 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3045 for &unsize in &[false, true] {
3046 let mut self_ty = adjusted_ty;
3048 // We only unsize arrays here.
3049 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3050 self_ty = self.tcx.mk_slice(element_ty);
3056 // If some lookup succeeds, write callee into table and extract index/element
3057 // type from the method signature.
3058 // If some lookup succeeded, install method in table
3059 let input_ty = self.next_ty_var(TypeVariableOrigin {
3060 kind: TypeVariableOriginKind::AutoDeref,
3061 span: base_expr.span,
3063 let method = self.try_overloaded_place_op(
3064 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
3066 let result = method.map(|ok| {
3067 debug!("try_index_step: success, using overloaded indexing");
3068 let method = self.register_infer_ok_obligations(ok);
3070 let mut adjustments = autoderef.adjust_steps(self, needs);
3071 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3072 let mutbl = match r_mutbl {
3073 hir::MutImmutable => AutoBorrowMutability::Immutable,
3074 hir::MutMutable => AutoBorrowMutability::Mutable {
3075 // Indexing can be desugared to a method call,
3076 // so maybe we could use two-phase here.
3077 // See the documentation of AllowTwoPhase for why that's
3078 // not the case today.
3079 allow_two_phase_borrow: AllowTwoPhase::No,
3082 adjustments.push(Adjustment {
3083 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3084 target: self.tcx.mk_ref(region, ty::TypeAndMut {
3091 adjustments.push(Adjustment {
3092 kind: Adjust::Pointer(PointerCast::Unsize),
3093 target: method.sig.inputs()[0]
3096 self.apply_adjustments(base_expr, adjustments);
3098 self.write_method_call(expr.hir_id, method);
3099 (input_ty, self.make_overloaded_place_return_type(method).ty)
3101 if result.is_some() {
3109 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3110 let (tr, name) = match (op, is_mut) {
3111 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3112 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3113 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3114 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3116 (tr, ast::Ident::with_dummy_span(name))
3119 fn try_overloaded_place_op(&self,
3122 arg_tys: &[Ty<'tcx>],
3125 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3127 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3133 // Try Mut first, if needed.
3134 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3135 let method = match (needs, mut_tr) {
3136 (Needs::MutPlace, Some(trait_did)) => {
3137 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3142 // Otherwise, fall back to the immutable version.
3143 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3144 let method = match (method, imm_tr) {
3145 (None, Some(trait_did)) => {
3146 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3148 (method, _) => method,
3154 fn check_method_argument_types(
3157 expr: &'tcx hir::Expr,
3158 method: Result<MethodCallee<'tcx>, ()>,
3159 args_no_rcvr: &'tcx [hir::Expr],
3160 tuple_arguments: TupleArgumentsFlag,
3161 expected: Expectation<'tcx>,
3164 let has_error = match method {
3166 method.substs.references_error() || method.sig.references_error()
3171 let err_inputs = self.err_args(args_no_rcvr.len());
3173 let err_inputs = match tuple_arguments {
3174 DontTupleArguments => err_inputs,
3175 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3178 self.check_argument_types(
3188 return self.tcx.types.err;
3191 let method = method.unwrap();
3192 // HACK(eddyb) ignore self in the definition (see above).
3193 let expected_arg_tys = self.expected_inputs_for_expected_output(
3196 method.sig.output(),
3197 &method.sig.inputs()[1..]
3199 self.check_argument_types(
3202 &method.sig.inputs()[1..],
3203 &expected_arg_tys[..],
3205 method.sig.c_variadic,
3207 self.tcx.hir().span_if_local(method.def_id),
3212 fn self_type_matches_expected_vid(
3214 trait_ref: ty::PolyTraitRef<'tcx>,
3215 expected_vid: ty::TyVid,
3217 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3219 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3220 trait_ref, self_ty, expected_vid
3222 match self_ty.kind {
3223 ty::Infer(ty::TyVar(found_vid)) => {
3224 // FIXME: consider using `sub_root_var` here so we
3225 // can see through subtyping.
3226 let found_vid = self.root_var(found_vid);
3227 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3228 expected_vid == found_vid
3234 fn obligations_for_self_ty<'b>(
3237 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3240 // FIXME: consider using `sub_root_var` here so we
3241 // can see through subtyping.
3242 let ty_var_root = self.root_var(self_ty);
3243 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3244 self_ty, ty_var_root,
3245 self.fulfillment_cx.borrow().pending_obligations());
3249 .pending_obligations()
3251 .filter_map(move |obligation| match obligation.predicate {
3252 ty::Predicate::Projection(ref data) =>
3253 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3254 ty::Predicate::Trait(ref data) =>
3255 Some((data.to_poly_trait_ref(), obligation)),
3256 ty::Predicate::Subtype(..) => None,
3257 ty::Predicate::RegionOutlives(..) => None,
3258 ty::Predicate::TypeOutlives(..) => None,
3259 ty::Predicate::WellFormed(..) => None,
3260 ty::Predicate::ObjectSafe(..) => None,
3261 ty::Predicate::ConstEvaluatable(..) => None,
3262 // N.B., this predicate is created by breaking down a
3263 // `ClosureType: FnFoo()` predicate, where
3264 // `ClosureType` represents some `Closure`. It can't
3265 // possibly be referring to the current closure,
3266 // because we haven't produced the `Closure` for
3267 // this closure yet; this is exactly why the other
3268 // code is looking for a self type of a unresolved
3269 // inference variable.
3270 ty::Predicate::ClosureKind(..) => None,
3271 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3274 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3275 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3276 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3280 /// Generic function that factors out common logic from function calls,
3281 /// method calls and overloaded operators.
3282 fn check_argument_types(
3285 expr: &'tcx hir::Expr,
3286 fn_inputs: &[Ty<'tcx>],
3287 expected_arg_tys: &[Ty<'tcx>],
3288 args: &'tcx [hir::Expr],
3290 tuple_arguments: TupleArgumentsFlag,
3291 def_span: Option<Span>,
3294 // Grab the argument types, supplying fresh type variables
3295 // if the wrong number of arguments were supplied
3296 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3302 // All the input types from the fn signature must outlive the call
3303 // so as to validate implied bounds.
3304 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3305 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3308 let expected_arg_count = fn_inputs.len();
3310 let param_count_error = |expected_count: usize,
3315 let mut err = tcx.sess.struct_span_err_with_code(sp,
3316 &format!("this function takes {}{} but {} {} supplied",
3317 if c_variadic { "at least " } else { "" },
3318 potentially_plural_count(expected_count, "parameter"),
3319 potentially_plural_count(arg_count, "parameter"),
3320 if arg_count == 1 {"was"} else {"were"}),
3321 DiagnosticId::Error(error_code.to_owned()));
3323 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3324 err.span_label(def_s, "defined here");
3327 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3328 // remove closing `)` from the span
3329 let sugg_span = sugg_span.shrink_to_lo();
3330 err.span_suggestion(
3332 "expected the unit value `()`; create it with empty parentheses",
3334 Applicability::MachineApplicable);
3336 err.span_label(sp, format!("expected {}{}",
3337 if c_variadic { "at least " } else { "" },
3338 potentially_plural_count(expected_count, "parameter")));
3343 let mut expected_arg_tys = expected_arg_tys.to_vec();
3345 let formal_tys = if tuple_arguments == TupleArguments {
3346 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3347 match tuple_type.kind {
3348 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3349 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3350 expected_arg_tys = vec![];
3351 self.err_args(args.len())
3353 ty::Tuple(arg_types) => {
3354 expected_arg_tys = match expected_arg_tys.get(0) {
3355 Some(&ty) => match ty.kind {
3356 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3361 arg_types.iter().map(|k| k.expect_ty()).collect()
3364 span_err!(tcx.sess, sp, E0059,
3365 "cannot use call notation; the first type parameter \
3366 for the function trait is neither a tuple nor unit");
3367 expected_arg_tys = vec![];
3368 self.err_args(args.len())
3371 } else if expected_arg_count == supplied_arg_count {
3373 } else if c_variadic {
3374 if supplied_arg_count >= expected_arg_count {
3377 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3378 expected_arg_tys = vec![];
3379 self.err_args(supplied_arg_count)
3382 // is the missing argument of type `()`?
3383 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3384 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3385 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3386 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3390 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3392 expected_arg_tys = vec![];
3393 self.err_args(supplied_arg_count)
3396 debug!("check_argument_types: formal_tys={:?}",
3397 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3399 // If there is no expectation, expect formal_tys.
3400 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3406 let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
3408 // Check the arguments.
3409 // We do this in a pretty awful way: first we type-check any arguments
3410 // that are not closures, then we type-check the closures. This is so
3411 // that we have more information about the types of arguments when we
3412 // type-check the functions. This isn't really the right way to do this.
3413 for &check_closures in &[false, true] {
3414 debug!("check_closures={}", check_closures);
3416 // More awful hacks: before we check argument types, try to do
3417 // an "opportunistic" vtable resolution of any trait bounds on
3418 // the call. This helps coercions.
3420 self.select_obligations_where_possible(false, |errors| {
3421 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
3422 self.point_at_arg_instead_of_call_if_possible(
3424 &final_arg_types[..],
3431 // For C-variadic functions, we don't have a declared type for all of
3432 // the arguments hence we only do our usual type checking with
3433 // the arguments who's types we do know.
3434 let t = if c_variadic {
3436 } else if tuple_arguments == TupleArguments {
3441 for (i, arg) in args.iter().take(t).enumerate() {
3442 // Warn only for the first loop (the "no closures" one).
3443 // Closure arguments themselves can't be diverging, but
3444 // a previous argument can, e.g., `foo(panic!(), || {})`.
3445 if !check_closures {
3446 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3449 let is_closure = match arg.kind {
3450 ExprKind::Closure(..) => true,
3454 if is_closure != check_closures {
3458 debug!("checking the argument");
3459 let formal_ty = formal_tys[i];
3461 // The special-cased logic below has three functions:
3462 // 1. Provide as good of an expected type as possible.
3463 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3465 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3467 // 2. Coerce to the most detailed type that could be coerced
3468 // to, which is `expected_ty` if `rvalue_hint` returns an
3469 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3470 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3471 // We're processing function arguments so we definitely want to use
3472 // two-phase borrows.
3473 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3474 final_arg_types.push((i, coerce_ty));
3476 // 3. Relate the expected type and the formal one,
3477 // if the expected type was used for the coercion.
3478 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3482 // We also need to make sure we at least write the ty of the other
3483 // arguments which we skipped above.
3485 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3486 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3487 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3490 for arg in args.iter().skip(expected_arg_count) {
3491 let arg_ty = self.check_expr(&arg);
3493 // There are a few types which get autopromoted when passed via varargs
3494 // in C but we just error out instead and require explicit casts.
3495 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3497 ty::Float(ast::FloatTy::F32) => {
3498 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3500 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3501 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3503 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3504 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3507 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3508 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3509 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3517 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3518 vec![self.tcx.types.err; len]
3521 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
3522 /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
3523 /// reference a type argument. If they do, and there's only *one* argument that does, we point
3524 /// at the corresponding argument's expression span instead of the `fn` call path span.
3525 fn point_at_arg_instead_of_call_if_possible(
3527 errors: &mut Vec<traits::FulfillmentError<'_>>,
3528 final_arg_types: &[(usize, Ty<'tcx>)],
3530 args: &'tcx [hir::Expr],
3532 if !call_sp.desugaring_kind().is_some() {
3533 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3534 // the `?` operator.
3535 for error in errors {
3536 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3537 // Collect the argument position for all arguments that could have caused this
3538 // `FullfillmentError`.
3539 let mut referenced_in = final_arg_types.iter()
3540 .flat_map(|(i, ty)| {
3541 let ty = self.resolve_vars_if_possible(ty);
3542 // We walk the argument type because the argument's type could have
3543 // been `Option<T>`, but the `FullfillmentError` references `T`.
3545 .filter(|&ty| ty == predicate.skip_binder().self_ty())
3548 if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
3549 // We make sure that only *one* argument matches the obligation failure
3550 // and thet the obligation's span to its expression's.
3551 error.obligation.cause.span = args[ref_in].span;
3552 error.points_at_arg_span = true;
3559 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call expression, we walk the
3560 /// `PathSegment`s and resolve their type parameters to see if any of the `FullfillmentError`s
3561 /// were caused by them. If they were, we point at the corresponding type argument's span
3562 /// instead of the `fn` call path span.
3563 fn point_at_type_arg_instead_of_call_if_possible(
3565 errors: &mut Vec<traits::FulfillmentError<'_>>,
3566 call_expr: &'tcx hir::Expr,
3568 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
3569 if let hir::ExprKind::Path(qpath) = &path.kind {
3570 if let hir::QPath::Resolved(_, path) = &qpath {
3571 for error in errors {
3572 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3573 // If any of the type arguments in this path segment caused the
3574 // `FullfillmentError`, point at its span (#61860).
3575 for arg in path.segments.iter()
3576 .filter_map(|seg| seg.args.as_ref())
3577 .flat_map(|a| a.args.iter())
3579 if let hir::GenericArg::Type(hir_ty) = &arg {
3580 if let hir::TyKind::Path(
3581 hir::QPath::TypeRelative(..),
3583 // Avoid ICE with associated types. As this is best
3584 // effort only, it's ok to ignore the case. It
3585 // would trigger in `is_send::<T::AssocType>();`
3586 // from `typeck-default-trait-impl-assoc-type.rs`.
3588 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
3589 let ty = self.resolve_vars_if_possible(&ty);
3590 if ty == predicate.skip_binder().self_ty() {
3591 error.obligation.cause.span = hir_ty.span;
3603 // AST fragment checking
3606 expected: Expectation<'tcx>)
3612 ast::LitKind::Str(..) => tcx.mk_static_str(),
3613 ast::LitKind::ByteStr(ref v) => {
3614 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3615 tcx.mk_array(tcx.types.u8, v.len() as u64))
3617 ast::LitKind::Byte(_) => tcx.types.u8,
3618 ast::LitKind::Char(_) => tcx.types.char,
3619 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3620 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3621 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3622 let opt_ty = expected.to_option(self).and_then(|ty| {
3624 ty::Int(_) | ty::Uint(_) => Some(ty),
3625 ty::Char => Some(tcx.types.u8),
3626 ty::RawPtr(..) => Some(tcx.types.usize),
3627 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3631 opt_ty.unwrap_or_else(|| self.next_int_var())
3633 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3634 ast::LitKind::FloatUnsuffixed(_) => {
3635 let opt_ty = expected.to_option(self).and_then(|ty| {
3637 ty::Float(_) => Some(ty),
3641 opt_ty.unwrap_or_else(|| self.next_float_var())
3643 ast::LitKind::Bool(_) => tcx.types.bool,
3644 ast::LitKind::Err(_) => tcx.types.err,
3648 // Determine the `Self` type, using fresh variables for all variables
3649 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3650 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3652 pub fn impl_self_ty(&self,
3653 span: Span, // (potential) receiver for this impl
3655 -> TypeAndSubsts<'tcx> {
3656 let ity = self.tcx.type_of(did);
3657 debug!("impl_self_ty: ity={:?}", ity);
3659 let substs = self.fresh_substs_for_item(span, did);
3660 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3662 TypeAndSubsts { substs: substs, ty: substd_ty }
3665 /// Unifies the output type with the expected type early, for more coercions
3666 /// and forward type information on the input expressions.
3667 fn expected_inputs_for_expected_output(&self,
3669 expected_ret: Expectation<'tcx>,
3670 formal_ret: Ty<'tcx>,
3671 formal_args: &[Ty<'tcx>])
3673 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3674 let ret_ty = match expected_ret.only_has_type(self) {
3676 None => return Vec::new()
3678 let expect_args = self.fudge_inference_if_ok(|| {
3679 // Attempt to apply a subtyping relationship between the formal
3680 // return type (likely containing type variables if the function
3681 // is polymorphic) and the expected return type.
3682 // No argument expectations are produced if unification fails.
3683 let origin = self.misc(call_span);
3684 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3686 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3687 // to identity so the resulting type is not constrained.
3690 // Process any obligations locally as much as
3691 // we can. We don't care if some things turn
3692 // out unconstrained or ambiguous, as we're
3693 // just trying to get hints here.
3694 self.save_and_restore_in_snapshot_flag(|_| {
3695 let mut fulfill = TraitEngine::new(self.tcx);
3696 for obligation in ok.obligations {
3697 fulfill.register_predicate_obligation(self, obligation);
3699 fulfill.select_where_possible(self)
3700 }).map_err(|_| ())?;
3702 Err(_) => return Err(()),
3705 // Record all the argument types, with the substitutions
3706 // produced from the above subtyping unification.
3707 Ok(formal_args.iter().map(|ty| {
3708 self.resolve_vars_if_possible(ty)
3710 }).unwrap_or_default();
3711 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3712 formal_args, formal_ret,
3713 expect_args, expected_ret);
3717 pub fn check_struct_path(&self,
3720 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3721 let path_span = match *qpath {
3722 QPath::Resolved(_, ref path) => path.span,
3723 QPath::TypeRelative(ref qself, _) => qself.span
3725 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3726 let variant = match def {
3728 self.set_tainted_by_errors();
3731 Res::Def(DefKind::Variant, _) => {
3733 ty::Adt(adt, substs) => {
3734 Some((adt.variant_of_res(def), adt.did, substs))
3736 _ => bug!("unexpected type: {:?}", ty)
3739 Res::Def(DefKind::Struct, _)
3740 | Res::Def(DefKind::Union, _)
3741 | Res::Def(DefKind::TyAlias, _)
3742 | Res::Def(DefKind::AssocTy, _)
3743 | Res::SelfTy(..) => {
3745 ty::Adt(adt, substs) if !adt.is_enum() => {
3746 Some((adt.non_enum_variant(), adt.did, substs))
3751 _ => bug!("unexpected definition: {:?}", def)
3754 if let Some((variant, did, substs)) = variant {
3755 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3756 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3758 // Check bounds on type arguments used in the path.
3759 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
3760 let cause = traits::ObligationCause::new(
3763 traits::ItemObligation(did),
3765 self.add_obligations_for_parameters(cause, &bounds);
3769 struct_span_err!(self.tcx.sess, path_span, E0071,
3770 "expected struct, variant or union type, found {}",
3771 ty.sort_string(self.tcx))
3772 .span_label(path_span, "not a struct")
3778 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3779 // The newly resolved definition is written into `type_dependent_defs`.
3780 fn finish_resolving_struct_path(&self,
3787 QPath::Resolved(ref maybe_qself, ref path) => {
3788 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3789 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3792 QPath::TypeRelative(ref qself, ref segment) => {
3793 let ty = self.to_ty(qself);
3795 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
3800 let result = AstConv::associated_path_to_ty(
3809 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3810 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3812 // Write back the new resolution.
3813 self.write_resolution(hir_id, result);
3815 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3820 /// Resolves an associated value path into a base type and associated constant, or method
3821 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3822 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3826 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3828 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3829 let (ty, qself, item_segment) = match *qpath {
3830 QPath::Resolved(ref opt_qself, ref path) => {
3832 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3833 &path.segments[..]);
3835 QPath::TypeRelative(ref qself, ref segment) => {
3836 (self.to_ty(qself), qself, segment)
3839 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3840 // Return directly on cache hit. This is useful to avoid doubly reporting
3841 // errors with default match binding modes. See #44614.
3842 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3843 .unwrap_or(Res::Err);
3844 return (def, Some(ty), slice::from_ref(&**item_segment));
3846 let item_name = item_segment.ident;
3847 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3848 let result = match error {
3849 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3850 _ => Err(ErrorReported),
3852 if item_name.name != kw::Invalid {
3853 self.report_method_error(
3857 SelfSource::QPath(qself),
3860 ).map(|mut e| e.emit());
3865 // Write back the new resolution.
3866 self.write_resolution(hir_id, result);
3868 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3870 slice::from_ref(&**item_segment),
3874 pub fn check_decl_initializer(
3876 local: &'tcx hir::Local,
3877 init: &'tcx hir::Expr,
3879 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3880 // for #42640 (default match binding modes).
3883 let ref_bindings = local.pat.contains_explicit_ref_binding();
3885 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3886 if let Some(m) = ref_bindings {
3887 // Somewhat subtle: if we have a `ref` binding in the pattern,
3888 // we want to avoid introducing coercions for the RHS. This is
3889 // both because it helps preserve sanity and, in the case of
3890 // ref mut, for soundness (issue #23116). In particular, in
3891 // the latter case, we need to be clear that the type of the
3892 // referent for the reference that results is *equal to* the
3893 // type of the place it is referencing, and not some
3894 // supertype thereof.
3895 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3896 self.demand_eqtype(init.span, local_ty, init_ty);
3899 self.check_expr_coercable_to_type(init, local_ty)
3903 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3904 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3905 self.write_ty(local.hir_id, t);
3907 if let Some(ref init) = local.init {
3908 let init_ty = self.check_decl_initializer(local, &init);
3909 self.overwrite_local_ty_if_err(local, t, init_ty);
3912 self.check_pat_top(&local.pat, t, None);
3913 let pat_ty = self.node_ty(local.pat.hir_id);
3914 self.overwrite_local_ty_if_err(local, t, pat_ty);
3917 fn overwrite_local_ty_if_err(&self, local: &'tcx hir::Local, decl_ty: Ty<'tcx>, ty: Ty<'tcx>) {
3918 if ty.references_error() {
3919 // Override the types everywhere with `types.err` to avoid knock down errors.
3920 self.write_ty(local.hir_id, ty);
3921 self.write_ty(local.pat.hir_id, ty);
3922 let local_ty = LocalTy {
3926 self.locals.borrow_mut().insert(local.hir_id, local_ty);
3927 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
3931 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
3932 err.span_suggestion_short(
3933 span.shrink_to_hi(),
3934 "consider using a semicolon here",
3936 Applicability::MachineApplicable,
3940 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3941 // Don't do all the complex logic below for `DeclItem`.
3943 hir::StmtKind::Item(..) => return,
3944 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3947 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3949 // Hide the outer diverging and `has_errors` flags.
3950 let old_diverges = self.diverges.get();
3951 let old_has_errors = self.has_errors.get();
3952 self.diverges.set(Diverges::Maybe);
3953 self.has_errors.set(false);
3956 hir::StmtKind::Local(ref l) => {
3957 self.check_decl_local(&l);
3960 hir::StmtKind::Item(_) => {}
3961 hir::StmtKind::Expr(ref expr) => {
3962 // Check with expected type of `()`.
3964 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
3965 self.suggest_semicolon_at_end(expr.span, err);
3968 hir::StmtKind::Semi(ref expr) => {
3969 self.check_expr(&expr);
3973 // Combine the diverging and `has_error` flags.
3974 self.diverges.set(self.diverges.get() | old_diverges);
3975 self.has_errors.set(self.has_errors.get() | old_has_errors);
3978 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
3979 let unit = self.tcx.mk_unit();
3980 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
3982 // if the block produces a `!` value, that can always be
3983 // (effectively) coerced to unit.
3985 self.demand_suptype(blk.span, unit, ty);
3989 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
3990 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
3991 /// when given code like the following:
3993 /// if false { return 0i32; } else { 1u32 }
3994 /// // ^^^^ point at this instead of the whole `if` expression
3996 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
3997 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
3998 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
3999 self.in_progress_tables
4000 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
4001 .and_then(|arm_ty| {
4002 if arm_ty.is_never() {
4005 Some(match &arm.body.kind {
4006 // Point at the tail expression when possible.
4007 hir::ExprKind::Block(block, _) => block.expr
4010 .unwrap_or(block.span),
4016 if arm_spans.len() == 1 {
4017 return arm_spans[0];
4023 fn check_block_with_expected(
4025 blk: &'tcx hir::Block,
4026 expected: Expectation<'tcx>,
4029 let mut fcx_ps = self.ps.borrow_mut();
4030 let unsafety_state = fcx_ps.recurse(blk);
4031 replace(&mut *fcx_ps, unsafety_state)
4034 // In some cases, blocks have just one exit, but other blocks
4035 // can be targeted by multiple breaks. This can happen both
4036 // with labeled blocks as well as when we desugar
4037 // a `try { ... }` expression.
4041 // 'a: { if true { break 'a Err(()); } Ok(()) }
4043 // Here we would wind up with two coercions, one from
4044 // `Err(())` and the other from the tail expression
4045 // `Ok(())`. If the tail expression is omitted, that's a
4046 // "forced unit" -- unless the block diverges, in which
4047 // case we can ignore the tail expression (e.g., `'a: {
4048 // break 'a 22; }` would not force the type of the block
4050 let tail_expr = blk.expr.as_ref();
4051 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4052 let coerce = if blk.targeted_by_break {
4053 CoerceMany::new(coerce_to_ty)
4055 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4056 Some(e) => slice::from_ref(e),
4059 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4062 let prev_diverges = self.diverges.get();
4063 let ctxt = BreakableCtxt {
4064 coerce: Some(coerce),
4068 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4069 for s in &blk.stmts {
4073 // check the tail expression **without** holding the
4074 // `enclosing_breakables` lock below.
4075 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4077 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4078 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4079 let coerce = ctxt.coerce.as_mut().unwrap();
4080 if let Some(tail_expr_ty) = tail_expr_ty {
4081 let tail_expr = tail_expr.unwrap();
4082 let span = self.get_expr_coercion_span(tail_expr);
4083 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4084 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4086 // Subtle: if there is no explicit tail expression,
4087 // that is typically equivalent to a tail expression
4088 // of `()` -- except if the block diverges. In that
4089 // case, there is no value supplied from the tail
4090 // expression (assuming there are no other breaks,
4091 // this implies that the type of the block will be
4094 // #41425 -- label the implicit `()` as being the
4095 // "found type" here, rather than the "expected type".
4096 if !self.diverges.get().is_always() {
4097 // #50009 -- Do not point at the entire fn block span, point at the return type
4098 // span, as it is the cause of the requirement, and
4099 // `consider_hint_about_removing_semicolon` will point at the last expression
4100 // if it were a relevant part of the error. This improves usability in editors
4101 // that highlight errors inline.
4102 let mut sp = blk.span;
4103 let mut fn_span = None;
4104 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4105 let ret_sp = decl.output.span();
4106 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4107 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4108 // output would otherwise be incorrect and even misleading. Make sure
4109 // the span we're aiming at correspond to a `fn` body.
4110 if block_sp == blk.span {
4112 fn_span = Some(ident.span);
4116 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4117 if let Some(expected_ty) = expected.only_has_type(self) {
4118 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4120 if let Some(fn_span) = fn_span {
4123 "implicitly returns `()` as its body has no tail or `return` \
4133 // If we can break from the block, then the block's exit is always reachable
4134 // (... as long as the entry is reachable) - regardless of the tail of the block.
4135 self.diverges.set(prev_diverges);
4138 let mut ty = ctxt.coerce.unwrap().complete(self);
4140 if self.has_errors.get() || ty.references_error() {
4141 ty = self.tcx.types.err
4144 self.write_ty(blk.hir_id, ty);
4146 *self.ps.borrow_mut() = prev;
4150 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4151 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4153 Node::Item(&hir::Item {
4154 kind: hir::ItemKind::Fn(_, _, _, body_id), ..
4156 Node::ImplItem(&hir::ImplItem {
4157 kind: hir::ImplItemKind::Method(_, body_id), ..
4159 let body = self.tcx.hir().body(body_id);
4160 if let ExprKind::Block(block, _) = &body.value.kind {
4161 return Some(block.span);
4169 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4170 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
4171 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4172 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4175 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4176 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
4178 Node::Item(&hir::Item {
4179 ident, kind: hir::ItemKind::Fn(ref decl, ..), ..
4181 // This is less than ideal, it will not suggest a return type span on any
4182 // method called `main`, regardless of whether it is actually the entry point,
4183 // but it will still present it as the reason for the expected type.
4184 Some((decl, ident, ident.name != sym::main))
4186 Node::TraitItem(&hir::TraitItem {
4187 ident, kind: hir::TraitItemKind::Method(hir::MethodSig {
4190 }) => Some((decl, ident, true)),
4191 Node::ImplItem(&hir::ImplItem {
4192 ident, kind: hir::ImplItemKind::Method(hir::MethodSig {
4195 }) => Some((decl, ident, false)),
4200 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4201 /// suggestion can be made, `None` otherwise.
4202 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
4203 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4204 // `while` before reaching it, as block tail returns are not available in them.
4205 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4206 let parent = self.tcx.hir().get(blk_id);
4207 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4211 /// On implicit return expressions with mismatched types, provides the following suggestions:
4213 /// - Points out the method's return type as the reason for the expected type.
4214 /// - Possible missing semicolon.
4215 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4216 pub fn suggest_mismatched_types_on_tail(
4218 err: &mut DiagnosticBuilder<'tcx>,
4219 expr: &'tcx hir::Expr,
4225 let expr = expr.peel_drop_temps();
4226 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4227 let mut pointing_at_return_type = false;
4228 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4229 pointing_at_return_type = self.suggest_missing_return_type(
4230 err, &fn_decl, expected, found, can_suggest);
4232 self.suggest_ref_or_into(err, expr, expected, found);
4233 self.suggest_boxing_when_appropriate(err, expr, expected, found);
4234 pointing_at_return_type
4237 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4238 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4240 /// fn foo(x: usize) -> usize { x }
4241 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4245 err: &mut DiagnosticBuilder<'tcx>,
4250 let hir = self.tcx.hir();
4251 let (def_id, sig) = match found.kind {
4252 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4253 ty::Closure(def_id, substs) => {
4254 // We don't use `closure_sig` to account for malformed closures like
4255 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4256 let closure_sig_ty = substs.as_closure().sig_ty(def_id, self.tcx);
4257 (def_id, match closure_sig_ty.kind {
4258 ty::FnPtr(sig) => sig,
4266 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4268 let sig = self.normalize_associated_types_in(expr.span, &sig);
4269 if self.can_coerce(sig.output(), expected) {
4270 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4271 (String::new(), Applicability::MachineApplicable)
4273 ("...".to_string(), Applicability::HasPlaceholders)
4275 let mut msg = "call this function";
4276 match hir.get_if_local(def_id) {
4277 Some(Node::Item(hir::Item {
4278 kind: ItemKind::Fn(.., body_id),
4281 Some(Node::ImplItem(hir::ImplItem {
4282 kind: hir::ImplItemKind::Method(_, body_id),
4285 Some(Node::TraitItem(hir::TraitItem {
4286 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4289 let body = hir.body(*body_id);
4290 sugg_call = body.params.iter()
4291 .map(|param| match ¶m.pat.kind {
4292 hir::PatKind::Binding(_, _, ident, None)
4293 if ident.name != kw::SelfLower => ident.to_string(),
4294 _ => "_".to_string(),
4295 }).collect::<Vec<_>>().join(", ");
4297 Some(Node::Expr(hir::Expr {
4298 kind: ExprKind::Closure(_, _, body_id, closure_span, _),
4299 span: full_closure_span,
4302 if *full_closure_span == expr.span {
4305 err.span_label(*closure_span, "closure defined here");
4306 msg = "call this closure";
4307 let body = hir.body(*body_id);
4308 sugg_call = body.params.iter()
4309 .map(|param| match ¶m.pat.kind {
4310 hir::PatKind::Binding(_, _, ident, None)
4311 if ident.name != kw::SelfLower => ident.to_string(),
4312 _ => "_".to_string(),
4313 }).collect::<Vec<_>>().join(", ");
4315 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4316 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4317 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4318 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4319 msg = "instantiate this tuple variant";
4321 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4322 msg = "instantiate this tuple struct";
4327 Some(Node::ForeignItem(hir::ForeignItem {
4328 kind: hir::ForeignItemKind::Fn(_, idents, _),
4331 Some(Node::TraitItem(hir::TraitItem {
4332 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4334 })) => sugg_call = idents.iter()
4335 .map(|ident| if ident.name != kw::SelfLower {
4339 }).collect::<Vec<_>>()
4343 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4344 err.span_suggestion(
4346 &format!("use parentheses to {}", msg),
4347 format!("{}({})", code, sugg_call),
4356 pub fn suggest_ref_or_into(
4358 err: &mut DiagnosticBuilder<'tcx>,
4363 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4364 err.span_suggestion(
4368 Applicability::MachineApplicable,
4370 } else if let (ty::FnDef(def_id, ..), true) = (
4372 self.suggest_fn_call(err, expr, expected, found),
4374 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4375 let sp = self.sess().source_map().def_span(sp);
4376 err.span_label(sp, &format!("{} defined here", found));
4378 } else if !self.check_for_cast(err, expr, found, expected) {
4379 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4383 let methods = self.get_conversion_methods(expr.span, expected, found);
4384 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4385 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4386 .filter_map(|(receiver, method)| {
4387 let method_call = format!(".{}()", method.ident);
4388 if receiver.ends_with(&method_call) {
4389 None // do not suggest code that is already there (#53348)
4391 let method_call_list = [".to_vec()", ".to_string()"];
4392 let sugg = if receiver.ends_with(".clone()")
4393 && method_call_list.contains(&method_call.as_str()) {
4394 let max_len = receiver.rfind(".").unwrap();
4395 format!("{}{}", &receiver[..max_len], method_call)
4397 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
4398 format!("({}){}", receiver, method_call)
4400 format!("{}{}", receiver, method_call)
4403 Some(if is_struct_pat_shorthand_field {
4404 format!("{}: {}", receiver, sugg)
4410 if suggestions.peek().is_some() {
4411 err.span_suggestions(
4413 "try using a conversion method",
4415 Applicability::MaybeIncorrect,
4422 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4423 /// in the heap by calling `Box::new()`.
4424 fn suggest_boxing_when_appropriate(
4426 err: &mut DiagnosticBuilder<'tcx>,
4431 if self.tcx.hir().is_const_context(expr.hir_id) {
4432 // Do not suggest `Box::new` in const context.
4435 if !expected.is_box() || found.is_box() {
4438 let boxed_found = self.tcx.mk_box(found);
4439 if let (true, Ok(snippet)) = (
4440 self.can_coerce(boxed_found, expected),
4441 self.sess().source_map().span_to_snippet(expr.span),
4443 err.span_suggestion(
4445 "store this in the heap by calling `Box::new`",
4446 format!("Box::new({})", snippet),
4447 Applicability::MachineApplicable,
4449 err.note("for more on the distinction between the stack and the \
4450 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4451 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4452 https://doc.rust-lang.org/std/boxed/index.html");
4457 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4461 /// bar_that_returns_u32()
4465 /// This routine checks if the return expression in a block would make sense on its own as a
4466 /// statement and the return type has been left as default or has been specified as `()`. If so,
4467 /// it suggests adding a semicolon.
4468 fn suggest_missing_semicolon(
4470 err: &mut DiagnosticBuilder<'tcx>,
4471 expression: &'tcx hir::Expr,
4475 if expected.is_unit() {
4476 // `BlockTailExpression` only relevant if the tail expr would be
4477 // useful on its own.
4478 match expression.kind {
4479 ExprKind::Call(..) |
4480 ExprKind::MethodCall(..) |
4481 ExprKind::Loop(..) |
4482 ExprKind::Match(..) |
4483 ExprKind::Block(..) => {
4484 let sp = self.tcx.sess.source_map().next_point(cause_span);
4485 err.span_suggestion(
4487 "try adding a semicolon",
4489 Applicability::MachineApplicable);
4496 /// A possible error is to forget to add a return type that is needed:
4500 /// bar_that_returns_u32()
4504 /// This routine checks if the return type is left as default, the method is not part of an
4505 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4507 fn suggest_missing_return_type(
4509 err: &mut DiagnosticBuilder<'tcx>,
4510 fn_decl: &hir::FnDecl,
4515 // Only suggest changing the return type for methods that
4516 // haven't set a return type at all (and aren't `fn main()` or an impl).
4517 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4518 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4519 err.span_suggestion(
4521 "try adding a return type",
4522 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
4523 Applicability::MachineApplicable);
4526 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4527 err.span_label(span, "possibly return type missing here?");
4530 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4531 // `fn main()` must return `()`, do not suggest changing return type
4532 err.span_label(span, "expected `()` because of default return type");
4535 // expectation was caused by something else, not the default return
4536 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4537 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4538 // Only point to return type if the expected type is the return type, as if they
4539 // are not, the expectation must have been caused by something else.
4540 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
4542 let ty = AstConv::ast_ty_to_ty(self, ty);
4543 debug!("suggest_missing_return_type: return type {:?}", ty);
4544 debug!("suggest_missing_return_type: expected type {:?}", ty);
4545 if ty.kind == expected.kind {
4546 err.span_label(sp, format!("expected `{}` because of return type",
4555 /// A possible error is to forget to add `.await` when using futures:
4558 /// async fn make_u32() -> u32 {
4562 /// fn take_u32(x: u32) {}
4564 /// async fn foo() {
4565 /// let x = make_u32();
4570 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4571 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4572 /// `.await` to the tail of the expression.
4573 fn suggest_missing_await(
4575 err: &mut DiagnosticBuilder<'tcx>,
4580 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4581 // body isn't `async`.
4582 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4583 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4584 let body = self.tcx().hir().body(body_id);
4585 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
4587 // Check for `Future` implementations by constructing a predicate to
4588 // prove: `<T as Future>::Output == U`
4589 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4590 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4591 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4592 // `<T as Future>::Output`
4593 projection_ty: ty::ProjectionTy {
4595 substs: self.tcx.mk_substs_trait(
4597 self.fresh_substs_for_item(sp, item_def_id)
4604 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4605 if self.infcx.predicate_may_hold(&obligation) {
4606 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4607 err.span_suggestion(
4609 "consider using `.await` here",
4610 format!("{}.await", code),
4611 Applicability::MaybeIncorrect,
4619 /// A common error is to add an extra semicolon:
4622 /// fn foo() -> usize {
4627 /// This routine checks if the final statement in a block is an
4628 /// expression with an explicit semicolon whose type is compatible
4629 /// with `expected_ty`. If so, it suggests removing the semicolon.
4630 fn consider_hint_about_removing_semicolon(
4632 blk: &'tcx hir::Block,
4633 expected_ty: Ty<'tcx>,
4634 err: &mut DiagnosticBuilder<'_>,
4636 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4637 err.span_suggestion(
4639 "consider removing this semicolon",
4641 Applicability::MachineApplicable,
4646 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4647 // Be helpful when the user wrote `{... expr;}` and
4648 // taking the `;` off is enough to fix the error.
4649 let last_stmt = blk.stmts.last()?;
4650 let last_expr = match last_stmt.kind {
4651 hir::StmtKind::Semi(ref e) => e,
4654 let last_expr_ty = self.node_ty(last_expr.hir_id);
4655 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4658 let original_span = original_sp(last_stmt.span, blk.span);
4659 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4662 // Instantiates the given path, which must refer to an item with the given
4663 // number of type parameters and type.
4664 pub fn instantiate_value_path(&self,
4665 segments: &[hir::PathSegment],
4666 self_ty: Option<Ty<'tcx>>,
4670 -> (Ty<'tcx>, Res) {
4672 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4681 let path_segs = match res {
4682 Res::Local(_) | Res::SelfCtor(_) => vec![],
4683 Res::Def(kind, def_id) =>
4684 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4685 _ => bug!("instantiate_value_path on {:?}", res),
4688 let mut user_self_ty = None;
4689 let mut is_alias_variant_ctor = false;
4691 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4692 if let Some(self_ty) = self_ty {
4693 let adt_def = self_ty.ty_adt_def().unwrap();
4694 user_self_ty = Some(UserSelfTy {
4695 impl_def_id: adt_def.did,
4698 is_alias_variant_ctor = true;
4701 Res::Def(DefKind::Method, def_id)
4702 | Res::Def(DefKind::AssocConst, def_id) => {
4703 let container = tcx.associated_item(def_id).container;
4704 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4706 ty::TraitContainer(trait_did) => {
4707 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4709 ty::ImplContainer(impl_def_id) => {
4710 if segments.len() == 1 {
4711 // `<T>::assoc` will end up here, and so
4712 // can `T::assoc`. It this came from an
4713 // inherent impl, we need to record the
4714 // `T` for posterity (see `UserSelfTy` for
4716 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4717 user_self_ty = Some(UserSelfTy {
4728 // Now that we have categorized what space the parameters for each
4729 // segment belong to, let's sort out the parameters that the user
4730 // provided (if any) into their appropriate spaces. We'll also report
4731 // errors if type parameters are provided in an inappropriate place.
4733 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4734 let generics_has_err = AstConv::prohibit_generics(
4735 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4736 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4743 if let Res::Local(hid) = res {
4744 let ty = self.local_ty(span, hid).decl_ty;
4745 let ty = self.normalize_associated_types_in(span, &ty);
4746 self.write_ty(hir_id, ty);
4750 if generics_has_err {
4751 // Don't try to infer type parameters when prohibited generic arguments were given.
4752 user_self_ty = None;
4755 // Now we have to compare the types that the user *actually*
4756 // provided against the types that were *expected*. If the user
4757 // did not provide any types, then we want to substitute inference
4758 // variables. If the user provided some types, we may still need
4759 // to add defaults. If the user provided *too many* types, that's
4762 let mut infer_args_for_err = FxHashSet::default();
4763 for &PathSeg(def_id, index) in &path_segs {
4764 let seg = &segments[index];
4765 let generics = tcx.generics_of(def_id);
4766 // Argument-position `impl Trait` is treated as a normal generic
4767 // parameter internally, but we don't allow users to specify the
4768 // parameter's value explicitly, so we have to do some error-
4770 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4775 false, // `is_method_call`
4777 if suppress_errors {
4778 infer_args_for_err.insert(index);
4779 self.set_tainted_by_errors(); // See issue #53251.
4783 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4784 tcx.generics_of(*def_id).has_self
4785 }).unwrap_or(false);
4787 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4788 let ty = self.impl_self_ty(span, impl_def_id).ty;
4789 let adt_def = ty.ty_adt_def();
4792 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4793 let variant = adt_def.non_enum_variant();
4794 let ctor_def_id = variant.ctor_def_id.unwrap();
4796 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4801 let mut err = tcx.sess.struct_span_err(span,
4802 "the `Self` constructor can only be used with tuple or unit structs");
4803 if let Some(adt_def) = adt_def {
4804 match adt_def.adt_kind() {
4806 err.help("did you mean to use one of the enum's variants?");
4810 err.span_suggestion(
4812 "use curly brackets",
4813 String::from("Self { /* fields */ }"),
4814 Applicability::HasPlaceholders,
4821 return (tcx.types.err, res)
4827 let def_id = res.def_id();
4829 // The things we are substituting into the type should not contain
4830 // escaping late-bound regions, and nor should the base type scheme.
4831 let ty = tcx.type_of(def_id);
4833 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4839 // Provide the generic args, and whether types should be inferred.
4841 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4844 // If we've encountered an `impl Trait`-related error, we're just
4845 // going to infer the arguments for better error messages.
4846 if !infer_args_for_err.contains(&index) {
4847 // Check whether the user has provided generic arguments.
4848 if let Some(ref data) = segments[index].args {
4849 return (Some(data), segments[index].infer_args);
4852 return (None, segments[index].infer_args);
4857 // Provide substitutions for parameters for which (valid) arguments have been provided.
4859 match (¶m.kind, arg) {
4860 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4861 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4863 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4864 self.to_ty(ty).into()
4866 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4867 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4869 _ => unreachable!(),
4872 // Provide substitutions for parameters for which arguments are inferred.
4873 |substs, param, infer_args| {
4875 GenericParamDefKind::Lifetime => {
4876 self.re_infer(Some(param), span).unwrap().into()
4878 GenericParamDefKind::Type { has_default, .. } => {
4879 if !infer_args && has_default {
4880 // If we have a default, then we it doesn't matter that we're not
4881 // inferring the type arguments: we provide the default where any
4883 let default = tcx.type_of(param.def_id);
4886 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4889 // If no type arguments were provided, we have to infer them.
4890 // This case also occurs as a result of some malformed input, e.g.
4891 // a lifetime argument being given instead of a type parameter.
4892 // Using inference instead of `Error` gives better error messages.
4893 self.var_for_def(span, param)
4896 GenericParamDefKind::Const => {
4897 // FIXME(const_generics:defaults)
4898 // No const parameters were provided, we have to infer them.
4899 self.var_for_def(span, param)
4904 assert!(!substs.has_escaping_bound_vars());
4905 assert!(!ty.has_escaping_bound_vars());
4907 // First, store the "user substs" for later.
4908 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4910 self.add_required_obligations(span, def_id, &substs);
4912 // Substitute the values for the type parameters into the type of
4913 // the referenced item.
4914 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4916 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4917 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4918 // is inherent, there is no `Self` parameter; instead, the impl needs
4919 // type parameters, which we can infer by unifying the provided `Self`
4920 // with the substituted impl type.
4921 // This also occurs for an enum variant on a type alias.
4922 let ty = tcx.type_of(impl_def_id);
4924 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4925 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4926 Ok(ok) => self.register_infer_ok_obligations(ok),
4928 self.tcx.sess.delay_span_bug(span, &format!(
4929 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4937 self.check_rustc_args_require_const(def_id, hir_id, span);
4939 debug!("instantiate_value_path: type of {:?} is {:?}",
4942 self.write_substs(hir_id, substs);
4944 (ty_substituted, res)
4947 /// Add all the obligations that are required, substituting and normalized appropriately.
4948 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
4949 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
4951 for (i, mut obligation) in traits::predicates_for_generics(
4952 traits::ObligationCause::new(
4955 traits::ItemObligation(def_id),
4959 ).into_iter().enumerate() {
4960 // This makes the error point at the bound, but we want to point at the argument
4961 if let Some(span) = spans.get(i) {
4962 obligation.cause.code = traits::BindingObligation(def_id, *span);
4964 self.register_predicate(obligation);
4968 fn check_rustc_args_require_const(&self,
4972 // We're only interested in functions tagged with
4973 // #[rustc_args_required_const], so ignore anything that's not.
4974 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
4978 // If our calling expression is indeed the function itself, we're good!
4979 // If not, generate an error that this can only be called directly.
4980 if let Node::Expr(expr) = self.tcx.hir().get(
4981 self.tcx.hir().get_parent_node(hir_id))
4983 if let ExprKind::Call(ref callee, ..) = expr.kind {
4984 if callee.hir_id == hir_id {
4990 self.tcx.sess.span_err(span, "this function can only be invoked \
4991 directly, not through a function pointer");
4994 // Resolves `typ` by a single level if `typ` is a type variable.
4995 // If no resolution is possible, then an error is reported.
4996 // Numeric inference variables may be left unresolved.
4997 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4998 let ty = self.resolve_type_vars_with_obligations(ty);
4999 if !ty.is_ty_var() {
5002 if !self.is_tainted_by_errors() {
5003 self.need_type_info_err((**self).body_id, sp, ty)
5004 .note("type must be known at this point")
5007 self.demand_suptype(sp, self.tcx.types.err, ty);
5012 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5015 ctxt: BreakableCtxt<'tcx>,
5017 ) -> (BreakableCtxt<'tcx>, R) {
5020 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5021 index = enclosing_breakables.stack.len();
5022 enclosing_breakables.by_id.insert(id, index);
5023 enclosing_breakables.stack.push(ctxt);
5027 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5028 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5029 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5030 enclosing_breakables.stack.pop().expect("missing breakable context")
5035 /// Instantiate a QueryResponse in a probe context, without a
5036 /// good ObligationCause.
5037 fn probe_instantiate_query_response(
5040 original_values: &OriginalQueryValues<'tcx>,
5041 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5042 ) -> InferResult<'tcx, Ty<'tcx>>
5044 self.instantiate_query_response_and_region_obligations(
5045 &traits::ObligationCause::misc(span, self.body_id),
5051 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5052 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5053 let mut contained_in_place = false;
5055 while let hir::Node::Expr(parent_expr) =
5056 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5058 match &parent_expr.kind {
5059 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5060 if lhs.hir_id == expr_id {
5061 contained_in_place = true;
5067 expr_id = parent_expr.hir_id;
5074 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5075 let own_counts = generics.own_counts();
5077 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5083 if own_counts.types == 0 {
5087 // Make a vector of booleans initially `false`; set to `true` when used.
5088 let mut types_used = vec![false; own_counts.types];
5090 for leaf_ty in ty.walk() {
5091 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.kind {
5092 debug!("found use of ty param num {}", index);
5093 types_used[index as usize - own_counts.lifetimes] = true;
5094 } else if let ty::Error = leaf_ty.kind {
5095 // If there is already another error, do not emit
5096 // an error for not using a type parameter.
5097 assert!(tcx.sess.has_errors());
5102 let types = generics.params.iter().filter(|param| match param.kind {
5103 ty::GenericParamDefKind::Type { .. } => true,
5106 for (&used, param) in types_used.iter().zip(types) {
5108 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5109 let span = tcx.hir().span(id);
5110 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5111 .span_label(span, "unused type parameter")
5117 fn fatally_break_rust(sess: &Session) {
5118 let handler = sess.diagnostic();
5119 handler.span_bug_no_panic(
5121 "It looks like you're trying to break rust; would you like some ICE?",
5123 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5124 handler.note_without_error(
5125 "we would appreciate a joke overview: \
5126 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5128 handler.note_without_error(&format!("rustc {} running on {}",
5129 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5130 crate::session::config::host_triple(),
5134 fn potentially_plural_count(count: usize, word: &str) -> String {
5135 format!("{} {}{}", count, word, pluralise!(count))