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_union_fields(tcx, span, def_id);
1391 check_packed(tcx, span, def_id);
1394 /// When the `#![feature(untagged_unions)]` gate is active,
1395 /// check that the fields of the `union` does not contain fields that need dropping.
1396 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: DefId) -> bool {
1397 let item_type = tcx.type_of(item_def_id);
1398 if let ty::Adt(def, substs) = item_type.kind {
1399 assert!(def.is_union());
1400 let fields = &def.non_enum_variant().fields;
1401 for field in fields {
1402 let field_ty = field.ty(tcx, substs);
1403 // We are currently checking the type this field came from, so it must be local.
1404 let field_span = tcx.hir().span_if_local(field.did).unwrap();
1405 let param_env = tcx.param_env(field.did);
1406 if field_ty.needs_drop(tcx, param_env) {
1407 struct_span_err!(tcx.sess, field_span, E0740,
1408 "unions may not contain fields that need dropping")
1409 .span_note(field_span,
1410 "`std::mem::ManuallyDrop` can be used to wrap the type")
1416 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind);
1421 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
1422 /// projections that would result in "inheriting lifetimes".
1423 fn check_opaque<'tcx>(
1426 substs: SubstsRef<'tcx>,
1428 origin: &hir::OpaqueTyOrigin,
1430 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
1431 check_opaque_for_cycles(tcx, def_id, substs, span, origin);
1434 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
1435 /// in "inheriting lifetimes".
1436 fn check_opaque_for_inheriting_lifetimes(
1441 let item = tcx.hir().expect_item(
1442 tcx.hir().as_local_hir_id(def_id).expect("opaque type is not local"));
1443 debug!("check_opaque_for_inheriting_lifetimes: def_id={:?} span={:?} item={:?}",
1444 def_id, span, item);
1447 struct ProhibitOpaqueVisitor<'tcx> {
1448 opaque_identity_ty: Ty<'tcx>,
1449 generics: &'tcx ty::Generics,
1452 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
1453 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
1454 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
1455 if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) }
1458 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1459 debug!("check_opaque_for_inheriting_lifetimes: (visit_region) r={:?}", r);
1460 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
1461 return *index < self.generics.parent_count as u32;
1464 r.super_visit_with(self)
1468 let prohibit_opaque = match item.kind {
1469 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn, .. }) |
1470 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn, .. }) => {
1471 let mut visitor = ProhibitOpaqueVisitor {
1472 opaque_identity_ty: tcx.mk_opaque(
1473 def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1474 generics: tcx.generics_of(def_id),
1476 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1478 tcx.predicates_of(def_id).predicates.iter().any(
1479 |(predicate, _)| predicate.visit_with(&mut visitor))
1484 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1485 if prohibit_opaque {
1486 let is_async = match item.kind {
1487 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1488 hir::OpaqueTyOrigin::AsyncFn => true,
1491 _ => unreachable!(),
1494 tcx.sess.span_err(span, &format!(
1495 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1497 if is_async { "async fn" } else { "impl Trait" },
1502 /// Checks that an opaque type does not contain cycles.
1503 fn check_opaque_for_cycles<'tcx>(
1506 substs: SubstsRef<'tcx>,
1508 origin: &hir::OpaqueTyOrigin,
1510 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1511 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1513 tcx.sess, span, E0733,
1514 "recursion in an `async fn` requires boxing",
1516 .span_label(span, "recursive `async fn`")
1517 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`.")
1520 let mut err = struct_span_err!(
1521 tcx.sess, span, E0720,
1522 "opaque type expands to a recursive type",
1524 err.span_label(span, "expands to a recursive type");
1525 if let ty::Opaque(..) = partially_expanded_type.kind {
1526 err.note("type resolves to itself");
1528 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1535 // Forbid defining intrinsics in Rust code,
1536 // as they must always be defined by the compiler.
1537 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1538 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1539 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1543 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
1545 "check_item_type(it.hir_id={}, it.name={})",
1547 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1549 let _indenter = indenter();
1551 // Consts can play a role in type-checking, so they are included here.
1552 hir::ItemKind::Static(..) => {
1553 let def_id = tcx.hir().local_def_id(it.hir_id);
1554 tcx.typeck_tables_of(def_id);
1555 maybe_check_static_with_link_section(tcx, def_id, it.span);
1557 hir::ItemKind::Const(..) => {
1558 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1560 hir::ItemKind::Enum(ref enum_definition, _) => {
1561 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1563 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1564 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1565 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1566 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1567 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1568 check_impl_items_against_trait(
1575 let trait_def_id = impl_trait_ref.def_id;
1576 check_on_unimplemented(tcx, trait_def_id, it);
1579 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1580 let def_id = tcx.hir().local_def_id(it.hir_id);
1581 check_on_unimplemented(tcx, def_id, it);
1583 for item in items.iter() {
1584 let item = tcx.hir().trait_item(item.id);
1585 if let hir::TraitItemKind::Method(sig, _) = &item.kind {
1586 let abi = sig.header.abi;
1587 fn_maybe_err(tcx, item.ident.span, abi);
1591 hir::ItemKind::Struct(..) => {
1592 check_struct(tcx, it.hir_id, it.span);
1594 hir::ItemKind::Union(..) => {
1595 check_union(tcx, it.hir_id, it.span);
1597 hir::ItemKind::OpaqueTy(hir::OpaqueTy{origin, ..}) => {
1598 let def_id = tcx.hir().local_def_id(it.hir_id);
1600 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1601 check_opaque(tcx, def_id, substs, it.span, &origin);
1603 hir::ItemKind::TyAlias(..) => {
1604 let def_id = tcx.hir().local_def_id(it.hir_id);
1605 let pty_ty = tcx.type_of(def_id);
1606 let generics = tcx.generics_of(def_id);
1607 check_bounds_are_used(tcx, &generics, pty_ty);
1609 hir::ItemKind::ForeignMod(ref m) => {
1610 check_abi(tcx, it.span, m.abi);
1612 if m.abi == Abi::RustIntrinsic {
1613 for item in &m.items {
1614 intrinsic::check_intrinsic_type(tcx, item);
1616 } else if m.abi == Abi::PlatformIntrinsic {
1617 for item in &m.items {
1618 intrinsic::check_platform_intrinsic_type(tcx, item);
1621 for item in &m.items {
1622 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1623 let own_counts = generics.own_counts();
1624 if generics.params.len() - own_counts.lifetimes != 0 {
1625 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1626 (_, 0) => ("type", "types", Some("u32")),
1627 // We don't specify an example value, because we can't generate
1628 // a valid value for any type.
1629 (0, _) => ("const", "consts", None),
1630 _ => ("type or const", "types or consts", None),
1636 "foreign items may not have {} parameters",
1640 &format!("can't have {} parameters", kinds),
1642 // FIXME: once we start storing spans for type arguments, turn this
1643 // into a suggestion.
1645 "replace the {} parameters with concrete {}{}",
1648 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1653 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.kind {
1654 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1659 _ => { /* nothing to do */ }
1663 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1664 // Only restricted on wasm32 target for now
1665 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1669 // If `#[link_section]` is missing, then nothing to verify
1670 let attrs = tcx.codegen_fn_attrs(id);
1671 if attrs.link_section.is_none() {
1675 // For the wasm32 target statics with `#[link_section]` are placed into custom
1676 // sections of the final output file, but this isn't link custom sections of
1677 // other executable formats. Namely we can only embed a list of bytes,
1678 // nothing with pointers to anything else or relocations. If any relocation
1679 // show up, reject them here.
1680 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1681 // the consumer's responsibility to ensure all bytes that have been read
1682 // have defined values.
1683 let instance = ty::Instance::mono(tcx, id);
1684 let cid = GlobalId {
1688 let param_env = ty::ParamEnv::reveal_all();
1689 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1690 let alloc = if let ConstValue::ByRef { alloc, .. } = static_.val {
1693 bug!("Matching on non-ByRef static")
1695 if alloc.relocations().len() != 0 {
1696 let msg = "statics with a custom `#[link_section]` must be a \
1697 simple list of bytes on the wasm target with no \
1698 extra levels of indirection such as references";
1699 tcx.sess.span_err(span, msg);
1704 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item) {
1705 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1706 // an error would be reported if this fails.
1707 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1710 fn report_forbidden_specialization(
1712 impl_item: &hir::ImplItem,
1715 let mut err = struct_span_err!(
1716 tcx.sess, impl_item.span, E0520,
1717 "`{}` specializes an item from a parent `impl`, but \
1718 that item is not marked `default`",
1720 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1723 match tcx.span_of_impl(parent_impl) {
1725 err.span_label(span, "parent `impl` is here");
1726 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1730 err.note(&format!("parent implementation is in crate `{}`", cname));
1737 fn check_specialization_validity<'tcx>(
1739 trait_def: &ty::TraitDef,
1740 trait_item: &ty::AssocItem,
1742 impl_item: &hir::ImplItem,
1744 let kind = match impl_item.kind {
1745 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1746 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1747 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1748 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1751 let mut ancestor_impls = trait_def.ancestors(tcx, impl_id)
1753 .filter_map(|parent| {
1754 if parent.is_from_trait() {
1757 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
1762 if ancestor_impls.peek().is_none() {
1763 // No parent, nothing to specialize.
1767 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
1769 // Parent impl exists, and contains the parent item we're trying to specialize, but
1770 // doesn't mark it `default`.
1771 Some(parent_item) if tcx.impl_item_is_final(&parent_item) => {
1772 Some(Err(parent_impl.def_id()))
1775 // Parent impl contains item and makes it specializable.
1780 // Parent impl doesn't mention the item. This means it's inherited from the
1781 // grandparent. In that case, if parent is a `default impl`, inherited items use the
1782 // "defaultness" from the grandparent, else they are final.
1783 None => if tcx.impl_is_default(parent_impl.def_id()) {
1786 Some(Err(parent_impl.def_id()))
1791 // If `opt_result` is `None`, we have only encoutered `default impl`s that don't contain the
1792 // item. This is allowed, the item isn't actually getting specialized here.
1793 let result = opt_result.unwrap_or(Ok(()));
1795 if let Err(parent_impl) = result {
1796 report_forbidden_specialization(tcx, impl_item, parent_impl);
1800 fn check_impl_items_against_trait<'tcx>(
1804 impl_trait_ref: ty::TraitRef<'tcx>,
1805 impl_item_refs: &[hir::ImplItemRef],
1807 let impl_span = tcx.sess.source_map().def_span(impl_span);
1809 // If the trait reference itself is erroneous (so the compilation is going
1810 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1811 // isn't populated for such impls.
1812 if impl_trait_ref.references_error() { return; }
1814 // Locate trait definition and items
1815 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1816 let mut overridden_associated_type = None;
1818 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1820 // Check existing impl methods to see if they are both present in trait
1821 // and compatible with trait signature
1822 for impl_item in impl_items() {
1823 let ty_impl_item = tcx.associated_item(
1824 tcx.hir().local_def_id(impl_item.hir_id));
1825 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1826 .find(|ac| Namespace::from(&impl_item.kind) == Namespace::from(ac.kind) &&
1827 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1829 // Not compatible, but needed for the error message
1830 tcx.associated_items(impl_trait_ref.def_id)
1831 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1834 // Check that impl definition matches trait definition
1835 if let Some(ty_trait_item) = ty_trait_item {
1836 match impl_item.kind {
1837 hir::ImplItemKind::Const(..) => {
1838 // Find associated const definition.
1839 if ty_trait_item.kind == ty::AssocKind::Const {
1840 compare_const_impl(tcx,
1846 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1847 "item `{}` is an associated const, \
1848 which doesn't match its trait `{}`",
1851 err.span_label(impl_item.span, "does not match trait");
1852 // We can only get the spans from local trait definition
1853 // Same for E0324 and E0325
1854 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1855 err.span_label(trait_span, "item in trait");
1860 hir::ImplItemKind::Method(..) => {
1861 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1862 if ty_trait_item.kind == ty::AssocKind::Method {
1863 compare_impl_method(tcx,
1870 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1871 "item `{}` is an associated method, \
1872 which doesn't match its trait `{}`",
1875 err.span_label(impl_item.span, "does not match trait");
1876 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1877 err.span_label(trait_span, "item in trait");
1882 hir::ImplItemKind::OpaqueTy(..) |
1883 hir::ImplItemKind::TyAlias(_) => {
1884 if ty_trait_item.kind == ty::AssocKind::Type {
1885 if ty_trait_item.defaultness.has_value() {
1886 overridden_associated_type = Some(impl_item);
1889 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1890 "item `{}` is an associated type, \
1891 which doesn't match its trait `{}`",
1894 err.span_label(impl_item.span, "does not match trait");
1895 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1896 err.span_label(trait_span, "item in trait");
1903 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1907 // Check for missing items from trait
1908 let mut missing_items = Vec::new();
1909 let mut invalidated_items = Vec::new();
1910 let associated_type_overridden = overridden_associated_type.is_some();
1911 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1912 let is_implemented = trait_def.ancestors(tcx, impl_id)
1913 .leaf_def(tcx, trait_item.ident, trait_item.kind)
1914 .map(|node_item| !node_item.node.is_from_trait())
1917 if !is_implemented && !tcx.impl_is_default(impl_id) {
1918 if !trait_item.defaultness.has_value() {
1919 missing_items.push(trait_item);
1920 } else if associated_type_overridden {
1921 invalidated_items.push(trait_item.ident);
1926 if !missing_items.is_empty() {
1927 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1928 "not all trait items implemented, missing: `{}`",
1929 missing_items.iter()
1930 .map(|trait_item| trait_item.ident.to_string())
1931 .collect::<Vec<_>>().join("`, `"));
1932 err.span_label(impl_span, format!("missing `{}` in implementation",
1933 missing_items.iter()
1934 .map(|trait_item| trait_item.ident.to_string())
1935 .collect::<Vec<_>>().join("`, `")));
1936 for trait_item in missing_items {
1937 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1938 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1940 err.note_trait_signature(trait_item.ident.to_string(),
1941 trait_item.signature(tcx));
1947 if !invalidated_items.is_empty() {
1948 let invalidator = overridden_associated_type.unwrap();
1949 span_err!(tcx.sess, invalidator.span, E0399,
1950 "the following trait items need to be reimplemented \
1951 as `{}` was overridden: `{}`",
1953 invalidated_items.iter()
1954 .map(|name| name.to_string())
1955 .collect::<Vec<_>>().join("`, `"))
1959 /// Checks whether a type can be represented in memory. In particular, it
1960 /// identifies types that contain themselves without indirection through a
1961 /// pointer, which would mean their size is unbounded.
1962 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
1963 let rty = tcx.type_of(item_def_id);
1965 // Check that it is possible to represent this type. This call identifies
1966 // (1) types that contain themselves and (2) types that contain a different
1967 // recursive type. It is only necessary to throw an error on those that
1968 // contain themselves. For case 2, there must be an inner type that will be
1969 // caught by case 1.
1970 match rty.is_representable(tcx, sp) {
1971 Representability::SelfRecursive(spans) => {
1972 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1974 err.span_label(span, "recursive without indirection");
1979 Representability::Representable | Representability::ContainsRecursive => (),
1984 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1985 let t = tcx.type_of(def_id);
1986 if let ty::Adt(def, substs) = t.kind {
1987 if def.is_struct() {
1988 let fields = &def.non_enum_variant().fields;
1989 if fields.is_empty() {
1990 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1993 let e = fields[0].ty(tcx, substs);
1994 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1995 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1996 .span_label(sp, "SIMD elements must have the same type")
2001 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
2002 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
2004 span_err!(tcx.sess, sp, E0077,
2005 "SIMD vector element type should be machine type");
2013 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2014 let repr = tcx.adt_def(def_id).repr;
2016 for attr in tcx.get_attrs(def_id).iter() {
2017 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
2018 if let attr::ReprPacked(pack) = r {
2019 if let Some(repr_pack) = repr.pack {
2020 if pack as u64 != repr_pack.bytes() {
2022 tcx.sess, sp, E0634,
2023 "type has conflicting packed representation hints"
2030 if repr.align.is_some() {
2031 struct_span_err!(tcx.sess, sp, E0587,
2032 "type has conflicting packed and align representation hints").emit();
2034 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
2035 struct_span_err!(tcx.sess, sp, E0588,
2036 "packed type cannot transitively contain a `[repr(align)]` type").emit();
2041 fn check_packed_inner(tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec<DefId>) -> bool {
2042 let t = tcx.type_of(def_id);
2043 if stack.contains(&def_id) {
2044 debug!("check_packed_inner: {:?} is recursive", t);
2047 if let ty::Adt(def, substs) = t.kind {
2048 if def.is_struct() || def.is_union() {
2049 if tcx.adt_def(def.did).repr.align.is_some() {
2052 // push struct def_id before checking fields
2054 for field in &def.non_enum_variant().fields {
2055 let f = field.ty(tcx, substs);
2056 if let ty::Adt(def, _) = f.kind {
2057 if check_packed_inner(tcx, def.did, stack) {
2062 // only need to pop if not early out
2069 /// Emit an error when encountering more or less than one variant in a transparent enum.
2070 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2071 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
2072 tcx.hir().span_if_local(variant.def_id).unwrap()
2075 "needs exactly one variant, but has {}",
2078 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2079 err.span_label(sp, &msg);
2080 if let &[ref start @ .., ref end] = &variant_spans[..] {
2081 for variant_span in start {
2082 err.span_label(*variant_span, "");
2084 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2089 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2091 fn bad_non_zero_sized_fields<'tcx>(
2093 adt: &'tcx ty::AdtDef,
2095 field_spans: impl Iterator<Item = Span>,
2098 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2099 let mut err = struct_span_err!(
2103 "{}transparent {} {}",
2104 if adt.is_enum() { "the variant of a " } else { "" },
2108 err.span_label(sp, &msg);
2109 for sp in field_spans {
2110 err.span_label(sp, "this field is non-zero-sized");
2115 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2116 let adt = tcx.adt_def(def_id);
2117 if !adt.repr.transparent() {
2120 let sp = tcx.sess.source_map().def_span(sp);
2123 if !tcx.features().transparent_enums {
2125 &tcx.sess.parse_sess,
2126 sym::transparent_enums,
2128 GateIssue::Language,
2129 "transparent enums are unstable",
2132 if adt.variants.len() != 1 {
2133 bad_variant_count(tcx, adt, sp, def_id);
2134 if adt.variants.is_empty() {
2135 // Don't bother checking the fields. No variants (and thus no fields) exist.
2141 if adt.is_union() && !tcx.features().transparent_unions {
2142 emit_feature_err(&tcx.sess.parse_sess,
2143 sym::transparent_unions,
2145 GateIssue::Language,
2146 "transparent unions are unstable");
2149 // For each field, figure out if it's known to be a ZST and align(1)
2150 let field_infos = adt.all_fields().map(|field| {
2151 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2152 let param_env = tcx.param_env(field.did);
2153 let layout = tcx.layout_of(param_env.and(ty));
2154 // We are currently checking the type this field came from, so it must be local
2155 let span = tcx.hir().span_if_local(field.did).unwrap();
2156 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2157 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2161 let non_zst_fields = field_infos.clone().filter_map(|(span, zst, _align1)| if !zst {
2166 let non_zst_count = non_zst_fields.clone().count();
2167 if non_zst_count != 1 {
2168 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2170 for (span, zst, align1) in field_infos {
2176 "zero-sized field in transparent {} has alignment larger than 1",
2178 ).span_label(span, "has alignment larger than 1").emit();
2183 #[allow(trivial_numeric_casts)]
2184 pub fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, vs: &'tcx [hir::Variant], id: hir::HirId) {
2185 let def_id = tcx.hir().local_def_id(id);
2186 let def = tcx.adt_def(def_id);
2187 def.destructor(tcx); // force the destructor to be evaluated
2190 let attributes = tcx.get_attrs(def_id);
2191 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2193 tcx.sess, attr.span, E0084,
2194 "unsupported representation for zero-variant enum")
2195 .span_label(sp, "zero-variant enum")
2200 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2201 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2202 if !tcx.features().repr128 {
2203 emit_feature_err(&tcx.sess.parse_sess,
2206 GateIssue::Language,
2207 "repr with 128-bit type is unstable");
2212 if let Some(ref e) = v.disr_expr {
2213 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2217 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2219 |var: &hir::Variant| match var.data {
2220 hir::VariantData::Unit(..) => true,
2224 let has_disr = |var: &hir::Variant| var.disr_expr.is_some();
2225 let has_non_units = vs.iter().any(|var| !is_unit(var));
2226 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2227 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2229 if disr_non_unit || (disr_units && has_non_units) {
2230 let mut err = struct_span_err!(tcx.sess, sp, E0732,
2231 "`#[repr(inttype)]` must be specified");
2236 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2237 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2238 // Check for duplicate discriminant values
2239 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2240 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2241 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2242 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2243 let i_span = match variant_i.disr_expr {
2244 Some(ref expr) => tcx.hir().span(expr.hir_id),
2245 None => tcx.hir().span(variant_i_hir_id)
2247 let span = match v.disr_expr {
2248 Some(ref expr) => tcx.hir().span(expr.hir_id),
2251 struct_span_err!(tcx.sess, span, E0081,
2252 "discriminant value `{}` already exists", disr_vals[i])
2253 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2254 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
2257 disr_vals.push(discr);
2260 check_representable(tcx, sp, def_id);
2261 check_transparent(tcx, sp, def_id);
2264 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span, qpath: &QPath) {
2265 span_err!(tcx.sess, span, E0533,
2266 "expected unit struct/variant or constant, found {} `{}`",
2268 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
2271 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2272 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2276 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2278 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2279 let item_id = tcx.hir().ty_param_owner(hir_id);
2280 let item_def_id = tcx.hir().local_def_id(item_id);
2281 let generics = tcx.generics_of(item_def_id);
2282 let index = generics.param_def_id_to_index[&def_id];
2283 ty::GenericPredicates {
2285 predicates: tcx.arena.alloc_from_iter(
2286 self.param_env.caller_bounds.iter().filter_map(|&predicate| match predicate {
2287 ty::Predicate::Trait(ref data)
2288 if data.skip_binder().self_ty().is_param(index) => {
2289 // HACK(eddyb) should get the original `Span`.
2290 let span = tcx.def_span(def_id);
2291 Some((predicate, span))
2301 def: Option<&ty::GenericParamDef>,
2303 ) -> Option<ty::Region<'tcx>> {
2305 Some(def) => infer::EarlyBoundRegion(span, def.name),
2306 None => infer::MiscVariable(span)
2308 Some(self.next_region_var(v))
2311 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2312 if let Some(param) = param {
2313 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2318 self.next_ty_var(TypeVariableOrigin {
2319 kind: TypeVariableOriginKind::TypeInference,
2328 param: Option<&ty::GenericParamDef>,
2330 ) -> &'tcx Const<'tcx> {
2331 if let Some(param) = param {
2332 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2337 self.next_const_var(ty, ConstVariableOrigin {
2338 kind: ConstVariableOriginKind::ConstInference,
2344 fn projected_ty_from_poly_trait_ref(&self,
2347 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2350 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2352 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2356 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2359 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2360 if ty.has_escaping_bound_vars() {
2361 ty // FIXME: normalization and escaping regions
2363 self.normalize_associated_types_in(span, &ty)
2367 fn set_tainted_by_errors(&self) {
2368 self.infcx.set_tainted_by_errors()
2371 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2372 self.write_ty(hir_id, ty)
2376 /// Controls whether the arguments are tupled. This is used for the call
2379 /// Tupling means that all call-side arguments are packed into a tuple and
2380 /// passed as a single parameter. For example, if tupling is enabled, this
2383 /// fn f(x: (isize, isize))
2385 /// Can be called as:
2392 #[derive(Clone, Eq, PartialEq)]
2393 enum TupleArgumentsFlag {
2398 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2400 inh: &'a Inherited<'a, 'tcx>,
2401 param_env: ty::ParamEnv<'tcx>,
2402 body_id: hir::HirId,
2403 ) -> FnCtxt<'a, 'tcx> {
2407 err_count_on_creation: inh.tcx.sess.err_count(),
2409 ret_coercion_span: RefCell::new(None),
2411 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2412 hir::CRATE_HIR_ID)),
2413 diverges: Cell::new(Diverges::Maybe),
2414 has_errors: Cell::new(false),
2415 enclosing_breakables: RefCell::new(EnclosingBreakables {
2417 by_id: Default::default(),
2423 pub fn sess(&self) -> &Session {
2427 pub fn errors_reported_since_creation(&self) -> bool {
2428 self.tcx.sess.err_count() > self.err_count_on_creation
2431 /// Produces warning on the given node, if the current point in the
2432 /// function is unreachable, and there hasn't been another warning.
2433 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2434 // FIXME: Combine these two 'if' expressions into one once
2435 // let chains are implemented
2436 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2437 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2438 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2439 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2440 if !span.is_desugaring(DesugaringKind::CondTemporary) &&
2441 !span.is_desugaring(DesugaringKind::Async) &&
2442 !orig_span.is_desugaring(DesugaringKind::Await)
2444 self.diverges.set(Diverges::WarnedAlways);
2446 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2448 let msg = format!("unreachable {}", kind);
2449 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2450 .span_label(span, &msg)
2453 custom_note.unwrap_or("any code following this expression is unreachable"),
2462 code: ObligationCauseCode<'tcx>)
2463 -> ObligationCause<'tcx> {
2464 ObligationCause::new(span, self.body_id, code)
2467 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2468 self.cause(span, ObligationCauseCode::MiscObligation)
2471 /// Resolves type and const variables in `ty` if possible. Unlike the infcx
2472 /// version (resolve_vars_if_possible), this version will
2473 /// also select obligations if it seems useful, in an effort
2474 /// to get more type information.
2475 fn resolve_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2476 debug!("resolve_vars_with_obligations(ty={:?})", ty);
2478 // No Infer()? Nothing needs doing.
2479 if !ty.has_infer_types() && !ty.has_infer_consts() {
2480 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2484 // If `ty` is a type variable, see whether we already know what it is.
2485 ty = self.resolve_vars_if_possible(&ty);
2486 if !ty.has_infer_types() && !ty.has_infer_consts() {
2487 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2491 // If not, try resolving pending obligations as much as
2492 // possible. This can help substantially when there are
2493 // indirect dependencies that don't seem worth tracking
2495 self.select_obligations_where_possible(false, |_| {});
2496 ty = self.resolve_vars_if_possible(&ty);
2498 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2502 fn record_deferred_call_resolution(
2504 closure_def_id: DefId,
2505 r: DeferredCallResolution<'tcx>,
2507 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2508 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2511 fn remove_deferred_call_resolutions(
2513 closure_def_id: DefId,
2514 ) -> Vec<DeferredCallResolution<'tcx>> {
2515 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2516 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2519 pub fn tag(&self) -> String {
2520 format!("{:p}", self)
2523 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2524 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2525 span_bug!(span, "no type for local variable {}",
2526 self.tcx.hir().node_to_string(nid))
2531 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2532 debug!("write_ty({:?}, {:?}) in fcx {}",
2533 id, self.resolve_vars_if_possible(&ty), self.tag());
2534 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2536 if ty.references_error() {
2537 self.has_errors.set(true);
2538 self.set_tainted_by_errors();
2542 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2543 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2546 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2547 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2550 pub fn write_method_call(&self,
2552 method: MethodCallee<'tcx>) {
2553 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2554 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2555 self.write_substs(hir_id, method.substs);
2557 // When the method is confirmed, the `method.substs` includes
2558 // parameters from not just the method, but also the impl of
2559 // the method -- in particular, the `Self` type will be fully
2560 // resolved. However, those are not something that the "user
2561 // specified" -- i.e., those types come from the inferred type
2562 // of the receiver, not something the user wrote. So when we
2563 // create the user-substs, we want to replace those earlier
2564 // types with just the types that the user actually wrote --
2565 // that is, those that appear on the *method itself*.
2567 // As an example, if the user wrote something like
2568 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2569 // type of `foo` (possibly adjusted), but we don't want to
2570 // include that. We want just the `[_, u32]` part.
2571 if !method.substs.is_noop() {
2572 let method_generics = self.tcx.generics_of(method.def_id);
2573 if !method_generics.params.is_empty() {
2574 let user_type_annotation = self.infcx.probe(|_| {
2575 let user_substs = UserSubsts {
2576 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2577 let i = param.index as usize;
2578 if i < method_generics.parent_count {
2579 self.infcx.var_for_def(DUMMY_SP, param)
2584 user_self_ty: None, // not relevant here
2587 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2593 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2594 self.write_user_type_annotation(hir_id, user_type_annotation);
2599 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2600 if !substs.is_noop() {
2601 debug!("write_substs({:?}, {:?}) in fcx {}",
2606 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2610 /// Given the substs that we just converted from the HIR, try to
2611 /// canonicalize them and store them as user-given substitutions
2612 /// (i.e., substitutions that must be respected by the NLL check).
2614 /// This should be invoked **before any unifications have
2615 /// occurred**, so that annotations like `Vec<_>` are preserved
2617 pub fn write_user_type_annotation_from_substs(
2621 substs: SubstsRef<'tcx>,
2622 user_self_ty: Option<UserSelfTy<'tcx>>,
2625 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2626 user_self_ty={:?} in fcx {}",
2627 hir_id, def_id, substs, user_self_ty, self.tag(),
2630 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2631 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2632 &UserType::TypeOf(def_id, UserSubsts {
2637 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2638 self.write_user_type_annotation(hir_id, canonicalized);
2642 pub fn write_user_type_annotation(
2645 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2648 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2649 hir_id, canonical_user_type_annotation, self.tag(),
2652 if !canonical_user_type_annotation.is_identity() {
2653 self.tables.borrow_mut().user_provided_types_mut().insert(
2654 hir_id, canonical_user_type_annotation
2657 debug!("write_user_type_annotation: skipping identity substs");
2661 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2662 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2668 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2669 Entry::Vacant(entry) => { entry.insert(adj); },
2670 Entry::Occupied(mut entry) => {
2671 debug!(" - composing on top of {:?}", entry.get());
2672 match (&entry.get()[..], &adj[..]) {
2673 // Applying any adjustment on top of a NeverToAny
2674 // is a valid NeverToAny adjustment, because it can't
2676 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2678 Adjustment { kind: Adjust::Deref(_), .. },
2679 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2681 Adjustment { kind: Adjust::Deref(_), .. },
2682 .. // Any following adjustments are allowed.
2684 // A reborrow has no effect before a dereference.
2686 // FIXME: currently we never try to compose autoderefs
2687 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2689 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2690 expr, entry.get(), adj)
2692 *entry.get_mut() = adj;
2697 /// Basically whenever we are converting from a type scheme into
2698 /// the fn body space, we always want to normalize associated
2699 /// types as well. This function combines the two.
2700 fn instantiate_type_scheme<T>(&self,
2702 substs: SubstsRef<'tcx>,
2705 where T : TypeFoldable<'tcx>
2707 let value = value.subst(self.tcx, substs);
2708 let result = self.normalize_associated_types_in(span, &value);
2709 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2716 /// As `instantiate_type_scheme`, but for the bounds found in a
2717 /// generic type scheme.
2718 fn instantiate_bounds(
2722 substs: SubstsRef<'tcx>,
2723 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
2724 let bounds = self.tcx.predicates_of(def_id);
2725 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
2726 let result = bounds.instantiate(self.tcx, substs);
2727 let result = self.normalize_associated_types_in(span, &result);
2729 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
2738 /// Replaces the opaque types from the given value with type variables,
2739 /// and records the `OpaqueTypeMap` for later use during writeback. See
2740 /// `InferCtxt::instantiate_opaque_types` for more details.
2741 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2743 parent_id: hir::HirId,
2747 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2748 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2752 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2753 self.instantiate_opaque_types(
2762 let mut opaque_types = self.opaque_types.borrow_mut();
2763 for (ty, decl) in opaque_type_map {
2764 let _ = opaque_types.insert(ty, decl);
2770 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2771 where T : TypeFoldable<'tcx>
2773 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2776 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2778 where T : TypeFoldable<'tcx>
2780 self.inh.partially_normalize_associated_types_in(span,
2786 pub fn require_type_meets(&self,
2789 code: traits::ObligationCauseCode<'tcx>,
2792 self.register_bound(
2795 traits::ObligationCause::new(span, self.body_id, code));
2798 pub fn require_type_is_sized(
2802 code: traits::ObligationCauseCode<'tcx>,
2804 if !ty.references_error() {
2805 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2806 self.require_type_meets(ty, span, code, lang_item);
2810 pub fn require_type_is_sized_deferred(
2814 code: traits::ObligationCauseCode<'tcx>,
2816 if !ty.references_error() {
2817 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2821 pub fn register_bound(
2825 cause: traits::ObligationCause<'tcx>,
2827 if !ty.references_error() {
2828 self.fulfillment_cx.borrow_mut()
2829 .register_bound(self, self.param_env, ty, def_id, cause);
2833 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2834 let t = AstConv::ast_ty_to_ty(self, ast_t);
2835 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2839 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2840 let ty = self.to_ty(ast_ty);
2841 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2843 if Self::can_contain_user_lifetime_bounds(ty) {
2844 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2845 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2846 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2852 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2853 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2854 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2857 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2858 AstConv::ast_const_to_const(self, ast_c, ty)
2861 // If the type given by the user has free regions, save it for later, since
2862 // NLL would like to enforce those. Also pass in types that involve
2863 // projections, since those can resolve to `'static` bounds (modulo #54940,
2864 // which hopefully will be fixed by the time you see this comment, dear
2865 // reader, although I have my doubts). Also pass in types with inference
2866 // types, because they may be repeated. Other sorts of things are already
2867 // sufficiently enforced with erased regions. =)
2868 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2870 T: TypeFoldable<'tcx>
2872 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2875 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2876 match self.tables.borrow().node_types().get(id) {
2878 None if self.is_tainted_by_errors() => self.tcx.types.err,
2880 bug!("no type for node {}: {} in fcx {}",
2881 id, self.tcx.hir().node_to_string(id),
2887 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2888 /// outlive the region `r`.
2889 pub fn register_wf_obligation(
2893 code: traits::ObligationCauseCode<'tcx>,
2895 // WF obligations never themselves fail, so no real need to give a detailed cause:
2896 let cause = traits::ObligationCause::new(span, self.body_id, code);
2897 self.register_predicate(
2898 traits::Obligation::new(cause, self.param_env, ty::Predicate::WellFormed(ty)),
2902 /// Registers obligations that all types appearing in `substs` are well-formed.
2903 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2904 for ty in substs.types() {
2905 if !ty.references_error() {
2906 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2911 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2912 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2913 /// trait/region obligations.
2915 /// For example, if there is a function:
2918 /// fn foo<'a,T:'a>(...)
2921 /// and a reference:
2927 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2928 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2929 pub fn add_obligations_for_parameters(&self,
2930 cause: traits::ObligationCause<'tcx>,
2931 predicates: &ty::InstantiatedPredicates<'tcx>)
2933 assert!(!predicates.has_escaping_bound_vars());
2935 debug!("add_obligations_for_parameters(predicates={:?})",
2938 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2939 self.register_predicate(obligation);
2943 // FIXME(arielb1): use this instead of field.ty everywhere
2944 // Only for fields! Returns <none> for methods>
2945 // Indifferent to privacy flags
2949 field: &'tcx ty::FieldDef,
2950 substs: SubstsRef<'tcx>,
2952 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2955 fn check_casts(&self) {
2956 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2957 for cast in deferred_cast_checks.drain(..) {
2962 fn resolve_generator_interiors(&self, def_id: DefId) {
2963 let mut generators = self.deferred_generator_interiors.borrow_mut();
2964 for (body_id, interior, kind) in generators.drain(..) {
2965 self.select_obligations_where_possible(false, |_| {});
2966 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2970 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2971 // Non-numerics get replaced with ! or () (depending on whether
2972 // feature(never_type) is enabled, unconstrained ints with i32,
2973 // unconstrained floats with f64.
2974 // Fallback becomes very dubious if we have encountered type-checking errors.
2975 // In that case, fallback to Error.
2976 // The return value indicates whether fallback has occurred.
2977 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2978 use rustc::ty::error::UnconstrainedNumeric::Neither;
2979 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2981 assert!(ty.is_ty_infer());
2982 let fallback = match self.type_is_unconstrained_numeric(ty) {
2983 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2984 UnconstrainedInt => self.tcx.types.i32,
2985 UnconstrainedFloat => self.tcx.types.f64,
2986 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2987 Neither => return false,
2989 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2990 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2994 fn select_all_obligations_or_error(&self) {
2995 debug!("select_all_obligations_or_error");
2996 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2997 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
3001 /// Select as many obligations as we can at present.
3002 fn select_obligations_where_possible(
3004 fallback_has_occurred: bool,
3005 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
3007 if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
3008 mutate_fullfillment_errors(&mut errors);
3009 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
3013 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
3014 /// returns a type of `&T`, but the actual type we assign to the
3015 /// *expression* is `T`. So this function just peels off the return
3016 /// type by one layer to yield `T`.
3017 fn make_overloaded_place_return_type(&self,
3018 method: MethodCallee<'tcx>)
3019 -> ty::TypeAndMut<'tcx>
3021 // extract method return type, which will be &T;
3022 let ret_ty = method.sig.output();
3024 // method returns &T, but the type as visible to user is T, so deref
3025 ret_ty.builtin_deref(true).unwrap()
3031 base_expr: &'tcx hir::Expr,
3035 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3036 // FIXME(#18741) -- this is almost but not quite the same as the
3037 // autoderef that normal method probing does. They could likely be
3040 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3041 let mut result = None;
3042 while result.is_none() && autoderef.next().is_some() {
3043 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3045 autoderef.finalize(self);
3049 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3050 /// (and otherwise adjust) `base_expr`, looking for a type which either
3051 /// supports builtin indexing or overloaded indexing.
3052 /// This loop implements one step in that search; the autoderef loop
3053 /// is implemented by `lookup_indexing`.
3057 base_expr: &hir::Expr,
3058 autoderef: &Autoderef<'a, 'tcx>,
3061 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3062 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3063 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3070 for &unsize in &[false, true] {
3071 let mut self_ty = adjusted_ty;
3073 // We only unsize arrays here.
3074 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3075 self_ty = self.tcx.mk_slice(element_ty);
3081 // If some lookup succeeds, write callee into table and extract index/element
3082 // type from the method signature.
3083 // If some lookup succeeded, install method in table
3084 let input_ty = self.next_ty_var(TypeVariableOrigin {
3085 kind: TypeVariableOriginKind::AutoDeref,
3086 span: base_expr.span,
3088 let method = self.try_overloaded_place_op(
3089 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
3091 let result = method.map(|ok| {
3092 debug!("try_index_step: success, using overloaded indexing");
3093 let method = self.register_infer_ok_obligations(ok);
3095 let mut adjustments = autoderef.adjust_steps(self, needs);
3096 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3097 let mutbl = match r_mutbl {
3098 hir::MutImmutable => AutoBorrowMutability::Immutable,
3099 hir::MutMutable => AutoBorrowMutability::Mutable {
3100 // Indexing can be desugared to a method call,
3101 // so maybe we could use two-phase here.
3102 // See the documentation of AllowTwoPhase for why that's
3103 // not the case today.
3104 allow_two_phase_borrow: AllowTwoPhase::No,
3107 adjustments.push(Adjustment {
3108 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3109 target: self.tcx.mk_ref(region, ty::TypeAndMut {
3116 adjustments.push(Adjustment {
3117 kind: Adjust::Pointer(PointerCast::Unsize),
3118 target: method.sig.inputs()[0]
3121 self.apply_adjustments(base_expr, adjustments);
3123 self.write_method_call(expr.hir_id, method);
3124 (input_ty, self.make_overloaded_place_return_type(method).ty)
3126 if result.is_some() {
3134 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3135 let (tr, name) = match (op, is_mut) {
3136 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3137 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3138 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3139 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3141 (tr, ast::Ident::with_dummy_span(name))
3144 fn try_overloaded_place_op(&self,
3147 arg_tys: &[Ty<'tcx>],
3150 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3152 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3158 // Try Mut first, if needed.
3159 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3160 let method = match (needs, mut_tr) {
3161 (Needs::MutPlace, Some(trait_did)) => {
3162 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3167 // Otherwise, fall back to the immutable version.
3168 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3169 let method = match (method, imm_tr) {
3170 (None, Some(trait_did)) => {
3171 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3173 (method, _) => method,
3179 fn check_method_argument_types(
3182 expr: &'tcx hir::Expr,
3183 method: Result<MethodCallee<'tcx>, ()>,
3184 args_no_rcvr: &'tcx [hir::Expr],
3185 tuple_arguments: TupleArgumentsFlag,
3186 expected: Expectation<'tcx>,
3189 let has_error = match method {
3191 method.substs.references_error() || method.sig.references_error()
3196 let err_inputs = self.err_args(args_no_rcvr.len());
3198 let err_inputs = match tuple_arguments {
3199 DontTupleArguments => err_inputs,
3200 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3203 self.check_argument_types(
3213 return self.tcx.types.err;
3216 let method = method.unwrap();
3217 // HACK(eddyb) ignore self in the definition (see above).
3218 let expected_arg_tys = self.expected_inputs_for_expected_output(
3221 method.sig.output(),
3222 &method.sig.inputs()[1..]
3224 self.check_argument_types(
3227 &method.sig.inputs()[1..],
3228 &expected_arg_tys[..],
3230 method.sig.c_variadic,
3232 self.tcx.hir().span_if_local(method.def_id),
3237 fn self_type_matches_expected_vid(
3239 trait_ref: ty::PolyTraitRef<'tcx>,
3240 expected_vid: ty::TyVid,
3242 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3244 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3245 trait_ref, self_ty, expected_vid
3247 match self_ty.kind {
3248 ty::Infer(ty::TyVar(found_vid)) => {
3249 // FIXME: consider using `sub_root_var` here so we
3250 // can see through subtyping.
3251 let found_vid = self.root_var(found_vid);
3252 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3253 expected_vid == found_vid
3259 fn obligations_for_self_ty<'b>(
3262 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3265 // FIXME: consider using `sub_root_var` here so we
3266 // can see through subtyping.
3267 let ty_var_root = self.root_var(self_ty);
3268 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3269 self_ty, ty_var_root,
3270 self.fulfillment_cx.borrow().pending_obligations());
3274 .pending_obligations()
3276 .filter_map(move |obligation| match obligation.predicate {
3277 ty::Predicate::Projection(ref data) =>
3278 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3279 ty::Predicate::Trait(ref data) =>
3280 Some((data.to_poly_trait_ref(), obligation)),
3281 ty::Predicate::Subtype(..) => None,
3282 ty::Predicate::RegionOutlives(..) => None,
3283 ty::Predicate::TypeOutlives(..) => None,
3284 ty::Predicate::WellFormed(..) => None,
3285 ty::Predicate::ObjectSafe(..) => None,
3286 ty::Predicate::ConstEvaluatable(..) => None,
3287 // N.B., this predicate is created by breaking down a
3288 // `ClosureType: FnFoo()` predicate, where
3289 // `ClosureType` represents some `Closure`. It can't
3290 // possibly be referring to the current closure,
3291 // because we haven't produced the `Closure` for
3292 // this closure yet; this is exactly why the other
3293 // code is looking for a self type of a unresolved
3294 // inference variable.
3295 ty::Predicate::ClosureKind(..) => None,
3296 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3299 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3300 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3301 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3305 /// Generic function that factors out common logic from function calls,
3306 /// method calls and overloaded operators.
3307 fn check_argument_types(
3310 expr: &'tcx hir::Expr,
3311 fn_inputs: &[Ty<'tcx>],
3312 expected_arg_tys: &[Ty<'tcx>],
3313 args: &'tcx [hir::Expr],
3315 tuple_arguments: TupleArgumentsFlag,
3316 def_span: Option<Span>,
3319 // Grab the argument types, supplying fresh type variables
3320 // if the wrong number of arguments were supplied
3321 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3327 // All the input types from the fn signature must outlive the call
3328 // so as to validate implied bounds.
3329 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3330 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3333 let expected_arg_count = fn_inputs.len();
3335 let param_count_error = |expected_count: usize,
3340 let mut err = tcx.sess.struct_span_err_with_code(sp,
3341 &format!("this function takes {}{} but {} {} supplied",
3342 if c_variadic { "at least " } else { "" },
3343 potentially_plural_count(expected_count, "parameter"),
3344 potentially_plural_count(arg_count, "parameter"),
3345 if arg_count == 1 {"was"} else {"were"}),
3346 DiagnosticId::Error(error_code.to_owned()));
3348 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3349 err.span_label(def_s, "defined here");
3352 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3353 // remove closing `)` from the span
3354 let sugg_span = sugg_span.shrink_to_lo();
3355 err.span_suggestion(
3357 "expected the unit value `()`; create it with empty parentheses",
3359 Applicability::MachineApplicable);
3361 err.span_label(sp, format!("expected {}{}",
3362 if c_variadic { "at least " } else { "" },
3363 potentially_plural_count(expected_count, "parameter")));
3368 let mut expected_arg_tys = expected_arg_tys.to_vec();
3370 let formal_tys = if tuple_arguments == TupleArguments {
3371 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3372 match tuple_type.kind {
3373 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3374 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3375 expected_arg_tys = vec![];
3376 self.err_args(args.len())
3378 ty::Tuple(arg_types) => {
3379 expected_arg_tys = match expected_arg_tys.get(0) {
3380 Some(&ty) => match ty.kind {
3381 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3386 arg_types.iter().map(|k| k.expect_ty()).collect()
3389 span_err!(tcx.sess, sp, E0059,
3390 "cannot use call notation; the first type parameter \
3391 for the function trait is neither a tuple nor unit");
3392 expected_arg_tys = vec![];
3393 self.err_args(args.len())
3396 } else if expected_arg_count == supplied_arg_count {
3398 } else if c_variadic {
3399 if supplied_arg_count >= expected_arg_count {
3402 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3403 expected_arg_tys = vec![];
3404 self.err_args(supplied_arg_count)
3407 // is the missing argument of type `()`?
3408 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3409 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3410 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3411 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3415 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3417 expected_arg_tys = vec![];
3418 self.err_args(supplied_arg_count)
3421 debug!("check_argument_types: formal_tys={:?}",
3422 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3424 // If there is no expectation, expect formal_tys.
3425 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3431 let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
3433 // Check the arguments.
3434 // We do this in a pretty awful way: first we type-check any arguments
3435 // that are not closures, then we type-check the closures. This is so
3436 // that we have more information about the types of arguments when we
3437 // type-check the functions. This isn't really the right way to do this.
3438 for &check_closures in &[false, true] {
3439 debug!("check_closures={}", check_closures);
3441 // More awful hacks: before we check argument types, try to do
3442 // an "opportunistic" vtable resolution of any trait bounds on
3443 // the call. This helps coercions.
3445 self.select_obligations_where_possible(false, |errors| {
3446 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
3447 self.point_at_arg_instead_of_call_if_possible(
3449 &final_arg_types[..],
3456 // For C-variadic functions, we don't have a declared type for all of
3457 // the arguments hence we only do our usual type checking with
3458 // the arguments who's types we do know.
3459 let t = if c_variadic {
3461 } else if tuple_arguments == TupleArguments {
3466 for (i, arg) in args.iter().take(t).enumerate() {
3467 // Warn only for the first loop (the "no closures" one).
3468 // Closure arguments themselves can't be diverging, but
3469 // a previous argument can, e.g., `foo(panic!(), || {})`.
3470 if !check_closures {
3471 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3474 let is_closure = match arg.kind {
3475 ExprKind::Closure(..) => true,
3479 if is_closure != check_closures {
3483 debug!("checking the argument");
3484 let formal_ty = formal_tys[i];
3486 // The special-cased logic below has three functions:
3487 // 1. Provide as good of an expected type as possible.
3488 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3490 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3492 // 2. Coerce to the most detailed type that could be coerced
3493 // to, which is `expected_ty` if `rvalue_hint` returns an
3494 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3495 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3496 // We're processing function arguments so we definitely want to use
3497 // two-phase borrows.
3498 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3499 final_arg_types.push((i, coerce_ty));
3501 // 3. Relate the expected type and the formal one,
3502 // if the expected type was used for the coercion.
3503 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3507 // We also need to make sure we at least write the ty of the other
3508 // arguments which we skipped above.
3510 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3511 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3512 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3515 for arg in args.iter().skip(expected_arg_count) {
3516 let arg_ty = self.check_expr(&arg);
3518 // There are a few types which get autopromoted when passed via varargs
3519 // in C but we just error out instead and require explicit casts.
3520 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3522 ty::Float(ast::FloatTy::F32) => {
3523 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3525 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3526 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3528 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3529 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3532 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3533 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3534 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3542 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3543 vec![self.tcx.types.err; len]
3546 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
3547 /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
3548 /// reference a type argument. If they do, and there's only *one* argument that does, we point
3549 /// at the corresponding argument's expression span instead of the `fn` call path span.
3550 fn point_at_arg_instead_of_call_if_possible(
3552 errors: &mut Vec<traits::FulfillmentError<'_>>,
3553 final_arg_types: &[(usize, Ty<'tcx>)],
3555 args: &'tcx [hir::Expr],
3557 if !call_sp.desugaring_kind().is_some() {
3558 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3559 // the `?` operator.
3560 for error in errors {
3561 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3562 // Collect the argument position for all arguments that could have caused this
3563 // `FullfillmentError`.
3564 let mut referenced_in = final_arg_types.iter()
3565 .flat_map(|(i, ty)| {
3566 let ty = self.resolve_vars_if_possible(ty);
3567 // We walk the argument type because the argument's type could have
3568 // been `Option<T>`, but the `FullfillmentError` references `T`.
3570 .filter(|&ty| ty == predicate.skip_binder().self_ty())
3573 if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
3574 // We make sure that only *one* argument matches the obligation failure
3575 // and thet the obligation's span to its expression's.
3576 error.obligation.cause.span = args[ref_in].span;
3577 error.points_at_arg_span = true;
3584 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call expression, we walk the
3585 /// `PathSegment`s and resolve their type parameters to see if any of the `FullfillmentError`s
3586 /// were caused by them. If they were, we point at the corresponding type argument's span
3587 /// instead of the `fn` call path span.
3588 fn point_at_type_arg_instead_of_call_if_possible(
3590 errors: &mut Vec<traits::FulfillmentError<'_>>,
3591 call_expr: &'tcx hir::Expr,
3593 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
3594 if let hir::ExprKind::Path(qpath) = &path.kind {
3595 if let hir::QPath::Resolved(_, path) = &qpath {
3596 for error in errors {
3597 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3598 // If any of the type arguments in this path segment caused the
3599 // `FullfillmentError`, point at its span (#61860).
3600 for arg in path.segments.iter()
3601 .filter_map(|seg| seg.args.as_ref())
3602 .flat_map(|a| a.args.iter())
3604 if let hir::GenericArg::Type(hir_ty) = &arg {
3605 if let hir::TyKind::Path(
3606 hir::QPath::TypeRelative(..),
3608 // Avoid ICE with associated types. As this is best
3609 // effort only, it's ok to ignore the case. It
3610 // would trigger in `is_send::<T::AssocType>();`
3611 // from `typeck-default-trait-impl-assoc-type.rs`.
3613 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
3614 let ty = self.resolve_vars_if_possible(&ty);
3615 if ty == predicate.skip_binder().self_ty() {
3616 error.obligation.cause.span = hir_ty.span;
3628 // AST fragment checking
3631 expected: Expectation<'tcx>)
3637 ast::LitKind::Str(..) => tcx.mk_static_str(),
3638 ast::LitKind::ByteStr(ref v) => {
3639 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3640 tcx.mk_array(tcx.types.u8, v.len() as u64))
3642 ast::LitKind::Byte(_) => tcx.types.u8,
3643 ast::LitKind::Char(_) => tcx.types.char,
3644 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3645 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3646 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3647 let opt_ty = expected.to_option(self).and_then(|ty| {
3649 ty::Int(_) | ty::Uint(_) => Some(ty),
3650 ty::Char => Some(tcx.types.u8),
3651 ty::RawPtr(..) => Some(tcx.types.usize),
3652 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3656 opt_ty.unwrap_or_else(|| self.next_int_var())
3658 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3659 ast::LitKind::FloatUnsuffixed(_) => {
3660 let opt_ty = expected.to_option(self).and_then(|ty| {
3662 ty::Float(_) => Some(ty),
3666 opt_ty.unwrap_or_else(|| self.next_float_var())
3668 ast::LitKind::Bool(_) => tcx.types.bool,
3669 ast::LitKind::Err(_) => tcx.types.err,
3673 // Determine the `Self` type, using fresh variables for all variables
3674 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3675 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3677 pub fn impl_self_ty(&self,
3678 span: Span, // (potential) receiver for this impl
3680 -> TypeAndSubsts<'tcx> {
3681 let ity = self.tcx.type_of(did);
3682 debug!("impl_self_ty: ity={:?}", ity);
3684 let substs = self.fresh_substs_for_item(span, did);
3685 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3687 TypeAndSubsts { substs: substs, ty: substd_ty }
3690 /// Unifies the output type with the expected type early, for more coercions
3691 /// and forward type information on the input expressions.
3692 fn expected_inputs_for_expected_output(&self,
3694 expected_ret: Expectation<'tcx>,
3695 formal_ret: Ty<'tcx>,
3696 formal_args: &[Ty<'tcx>])
3698 let formal_ret = self.resolve_vars_with_obligations(formal_ret);
3699 let ret_ty = match expected_ret.only_has_type(self) {
3701 None => return Vec::new()
3703 let expect_args = self.fudge_inference_if_ok(|| {
3704 // Attempt to apply a subtyping relationship between the formal
3705 // return type (likely containing type variables if the function
3706 // is polymorphic) and the expected return type.
3707 // No argument expectations are produced if unification fails.
3708 let origin = self.misc(call_span);
3709 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3711 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3712 // to identity so the resulting type is not constrained.
3715 // Process any obligations locally as much as
3716 // we can. We don't care if some things turn
3717 // out unconstrained or ambiguous, as we're
3718 // just trying to get hints here.
3719 self.save_and_restore_in_snapshot_flag(|_| {
3720 let mut fulfill = TraitEngine::new(self.tcx);
3721 for obligation in ok.obligations {
3722 fulfill.register_predicate_obligation(self, obligation);
3724 fulfill.select_where_possible(self)
3725 }).map_err(|_| ())?;
3727 Err(_) => return Err(()),
3730 // Record all the argument types, with the substitutions
3731 // produced from the above subtyping unification.
3732 Ok(formal_args.iter().map(|ty| {
3733 self.resolve_vars_if_possible(ty)
3735 }).unwrap_or_default();
3736 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3737 formal_args, formal_ret,
3738 expect_args, expected_ret);
3742 pub fn check_struct_path(&self,
3745 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3746 let path_span = match *qpath {
3747 QPath::Resolved(_, ref path) => path.span,
3748 QPath::TypeRelative(ref qself, _) => qself.span
3750 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3751 let variant = match def {
3753 self.set_tainted_by_errors();
3756 Res::Def(DefKind::Variant, _) => {
3758 ty::Adt(adt, substs) => {
3759 Some((adt.variant_of_res(def), adt.did, substs))
3761 _ => bug!("unexpected type: {:?}", ty)
3764 Res::Def(DefKind::Struct, _)
3765 | Res::Def(DefKind::Union, _)
3766 | Res::Def(DefKind::TyAlias, _)
3767 | Res::Def(DefKind::AssocTy, _)
3768 | Res::SelfTy(..) => {
3770 ty::Adt(adt, substs) if !adt.is_enum() => {
3771 Some((adt.non_enum_variant(), adt.did, substs))
3776 _ => bug!("unexpected definition: {:?}", def)
3779 if let Some((variant, did, substs)) = variant {
3780 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3781 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3783 // Check bounds on type arguments used in the path.
3784 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
3785 let cause = traits::ObligationCause::new(
3788 traits::ItemObligation(did),
3790 self.add_obligations_for_parameters(cause, &bounds);
3794 struct_span_err!(self.tcx.sess, path_span, E0071,
3795 "expected struct, variant or union type, found {}",
3796 ty.sort_string(self.tcx))
3797 .span_label(path_span, "not a struct")
3803 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3804 // The newly resolved definition is written into `type_dependent_defs`.
3805 fn finish_resolving_struct_path(&self,
3812 QPath::Resolved(ref maybe_qself, ref path) => {
3813 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3814 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3817 QPath::TypeRelative(ref qself, ref segment) => {
3818 let ty = self.to_ty(qself);
3820 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
3825 let result = AstConv::associated_path_to_ty(
3834 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3835 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3837 // Write back the new resolution.
3838 self.write_resolution(hir_id, result);
3840 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3845 /// Resolves an associated value path into a base type and associated constant, or method
3846 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3847 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3851 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3853 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3854 let (ty, qself, item_segment) = match *qpath {
3855 QPath::Resolved(ref opt_qself, ref path) => {
3857 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3858 &path.segments[..]);
3860 QPath::TypeRelative(ref qself, ref segment) => {
3861 (self.to_ty(qself), qself, segment)
3864 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3865 // Return directly on cache hit. This is useful to avoid doubly reporting
3866 // errors with default match binding modes. See #44614.
3867 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3868 .unwrap_or(Res::Err);
3869 return (def, Some(ty), slice::from_ref(&**item_segment));
3871 let item_name = item_segment.ident;
3872 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3873 let result = match error {
3874 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3875 _ => Err(ErrorReported),
3877 if item_name.name != kw::Invalid {
3878 self.report_method_error(
3882 SelfSource::QPath(qself),
3885 ).map(|mut e| e.emit());
3890 // Write back the new resolution.
3891 self.write_resolution(hir_id, result);
3893 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3895 slice::from_ref(&**item_segment),
3899 pub fn check_decl_initializer(
3901 local: &'tcx hir::Local,
3902 init: &'tcx hir::Expr,
3904 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3905 // for #42640 (default match binding modes).
3908 let ref_bindings = local.pat.contains_explicit_ref_binding();
3910 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3911 if let Some(m) = ref_bindings {
3912 // Somewhat subtle: if we have a `ref` binding in the pattern,
3913 // we want to avoid introducing coercions for the RHS. This is
3914 // both because it helps preserve sanity and, in the case of
3915 // ref mut, for soundness (issue #23116). In particular, in
3916 // the latter case, we need to be clear that the type of the
3917 // referent for the reference that results is *equal to* the
3918 // type of the place it is referencing, and not some
3919 // supertype thereof.
3920 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3921 self.demand_eqtype(init.span, local_ty, init_ty);
3924 self.check_expr_coercable_to_type(init, local_ty)
3928 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3929 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3930 self.write_ty(local.hir_id, t);
3932 if let Some(ref init) = local.init {
3933 let init_ty = self.check_decl_initializer(local, &init);
3934 self.overwrite_local_ty_if_err(local, t, init_ty);
3937 self.check_pat_top(&local.pat, t, None);
3938 let pat_ty = self.node_ty(local.pat.hir_id);
3939 self.overwrite_local_ty_if_err(local, t, pat_ty);
3942 fn overwrite_local_ty_if_err(&self, local: &'tcx hir::Local, decl_ty: Ty<'tcx>, ty: Ty<'tcx>) {
3943 if ty.references_error() {
3944 // Override the types everywhere with `types.err` to avoid knock down errors.
3945 self.write_ty(local.hir_id, ty);
3946 self.write_ty(local.pat.hir_id, ty);
3947 let local_ty = LocalTy {
3951 self.locals.borrow_mut().insert(local.hir_id, local_ty);
3952 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
3956 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
3957 err.span_suggestion_short(
3958 span.shrink_to_hi(),
3959 "consider using a semicolon here",
3961 Applicability::MachineApplicable,
3965 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3966 // Don't do all the complex logic below for `DeclItem`.
3968 hir::StmtKind::Item(..) => return,
3969 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3972 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3974 // Hide the outer diverging and `has_errors` flags.
3975 let old_diverges = self.diverges.get();
3976 let old_has_errors = self.has_errors.get();
3977 self.diverges.set(Diverges::Maybe);
3978 self.has_errors.set(false);
3981 hir::StmtKind::Local(ref l) => {
3982 self.check_decl_local(&l);
3985 hir::StmtKind::Item(_) => {}
3986 hir::StmtKind::Expr(ref expr) => {
3987 // Check with expected type of `()`.
3989 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
3990 self.suggest_semicolon_at_end(expr.span, err);
3993 hir::StmtKind::Semi(ref expr) => {
3994 self.check_expr(&expr);
3998 // Combine the diverging and `has_error` flags.
3999 self.diverges.set(self.diverges.get() | old_diverges);
4000 self.has_errors.set(self.has_errors.get() | old_has_errors);
4003 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
4004 let unit = self.tcx.mk_unit();
4005 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4007 // if the block produces a `!` value, that can always be
4008 // (effectively) coerced to unit.
4010 self.demand_suptype(blk.span, unit, ty);
4014 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
4015 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
4016 /// when given code like the following:
4018 /// if false { return 0i32; } else { 1u32 }
4019 /// // ^^^^ point at this instead of the whole `if` expression
4021 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
4022 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
4023 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
4024 self.in_progress_tables
4025 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
4026 .and_then(|arm_ty| {
4027 if arm_ty.is_never() {
4030 Some(match &arm.body.kind {
4031 // Point at the tail expression when possible.
4032 hir::ExprKind::Block(block, _) => block.expr
4035 .unwrap_or(block.span),
4041 if arm_spans.len() == 1 {
4042 return arm_spans[0];
4048 fn check_block_with_expected(
4050 blk: &'tcx hir::Block,
4051 expected: Expectation<'tcx>,
4054 let mut fcx_ps = self.ps.borrow_mut();
4055 let unsafety_state = fcx_ps.recurse(blk);
4056 replace(&mut *fcx_ps, unsafety_state)
4059 // In some cases, blocks have just one exit, but other blocks
4060 // can be targeted by multiple breaks. This can happen both
4061 // with labeled blocks as well as when we desugar
4062 // a `try { ... }` expression.
4066 // 'a: { if true { break 'a Err(()); } Ok(()) }
4068 // Here we would wind up with two coercions, one from
4069 // `Err(())` and the other from the tail expression
4070 // `Ok(())`. If the tail expression is omitted, that's a
4071 // "forced unit" -- unless the block diverges, in which
4072 // case we can ignore the tail expression (e.g., `'a: {
4073 // break 'a 22; }` would not force the type of the block
4075 let tail_expr = blk.expr.as_ref();
4076 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4077 let coerce = if blk.targeted_by_break {
4078 CoerceMany::new(coerce_to_ty)
4080 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4081 Some(e) => slice::from_ref(e),
4084 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4087 let prev_diverges = self.diverges.get();
4088 let ctxt = BreakableCtxt {
4089 coerce: Some(coerce),
4093 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4094 for s in &blk.stmts {
4098 // check the tail expression **without** holding the
4099 // `enclosing_breakables` lock below.
4100 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4102 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4103 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4104 let coerce = ctxt.coerce.as_mut().unwrap();
4105 if let Some(tail_expr_ty) = tail_expr_ty {
4106 let tail_expr = tail_expr.unwrap();
4107 let span = self.get_expr_coercion_span(tail_expr);
4108 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4109 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4111 // Subtle: if there is no explicit tail expression,
4112 // that is typically equivalent to a tail expression
4113 // of `()` -- except if the block diverges. In that
4114 // case, there is no value supplied from the tail
4115 // expression (assuming there are no other breaks,
4116 // this implies that the type of the block will be
4119 // #41425 -- label the implicit `()` as being the
4120 // "found type" here, rather than the "expected type".
4121 if !self.diverges.get().is_always() {
4122 // #50009 -- Do not point at the entire fn block span, point at the return type
4123 // span, as it is the cause of the requirement, and
4124 // `consider_hint_about_removing_semicolon` will point at the last expression
4125 // if it were a relevant part of the error. This improves usability in editors
4126 // that highlight errors inline.
4127 let mut sp = blk.span;
4128 let mut fn_span = None;
4129 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4130 let ret_sp = decl.output.span();
4131 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4132 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4133 // output would otherwise be incorrect and even misleading. Make sure
4134 // the span we're aiming at correspond to a `fn` body.
4135 if block_sp == blk.span {
4137 fn_span = Some(ident.span);
4141 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4142 if let Some(expected_ty) = expected.only_has_type(self) {
4143 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4145 if let Some(fn_span) = fn_span {
4148 "implicitly returns `()` as its body has no tail or `return` \
4158 // If we can break from the block, then the block's exit is always reachable
4159 // (... as long as the entry is reachable) - regardless of the tail of the block.
4160 self.diverges.set(prev_diverges);
4163 let mut ty = ctxt.coerce.unwrap().complete(self);
4165 if self.has_errors.get() || ty.references_error() {
4166 ty = self.tcx.types.err
4169 self.write_ty(blk.hir_id, ty);
4171 *self.ps.borrow_mut() = prev;
4175 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4176 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4178 Node::Item(&hir::Item {
4179 kind: hir::ItemKind::Fn(_, _, _, body_id), ..
4181 Node::ImplItem(&hir::ImplItem {
4182 kind: hir::ImplItemKind::Method(_, body_id), ..
4184 let body = self.tcx.hir().body(body_id);
4185 if let ExprKind::Block(block, _) = &body.value.kind {
4186 return Some(block.span);
4194 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4195 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
4196 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4197 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4200 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4201 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
4203 Node::Item(&hir::Item {
4204 ident, kind: hir::ItemKind::Fn(ref decl, ..), ..
4206 // This is less than ideal, it will not suggest a return type span on any
4207 // method called `main`, regardless of whether it is actually the entry point,
4208 // but it will still present it as the reason for the expected type.
4209 Some((decl, ident, ident.name != sym::main))
4211 Node::TraitItem(&hir::TraitItem {
4212 ident, kind: hir::TraitItemKind::Method(hir::MethodSig {
4215 }) => Some((decl, ident, true)),
4216 Node::ImplItem(&hir::ImplItem {
4217 ident, kind: hir::ImplItemKind::Method(hir::MethodSig {
4220 }) => Some((decl, ident, false)),
4225 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4226 /// suggestion can be made, `None` otherwise.
4227 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
4228 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4229 // `while` before reaching it, as block tail returns are not available in them.
4230 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4231 let parent = self.tcx.hir().get(blk_id);
4232 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4236 /// On implicit return expressions with mismatched types, provides the following suggestions:
4238 /// - Points out the method's return type as the reason for the expected type.
4239 /// - Possible missing semicolon.
4240 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4241 pub fn suggest_mismatched_types_on_tail(
4243 err: &mut DiagnosticBuilder<'tcx>,
4244 expr: &'tcx hir::Expr,
4250 let expr = expr.peel_drop_temps();
4251 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4252 let mut pointing_at_return_type = false;
4253 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4254 pointing_at_return_type = self.suggest_missing_return_type(
4255 err, &fn_decl, expected, found, can_suggest);
4257 self.suggest_ref_or_into(err, expr, expected, found);
4258 self.suggest_boxing_when_appropriate(err, expr, expected, found);
4259 pointing_at_return_type
4262 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4263 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4265 /// fn foo(x: usize) -> usize { x }
4266 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4270 err: &mut DiagnosticBuilder<'tcx>,
4275 let hir = self.tcx.hir();
4276 let (def_id, sig) = match found.kind {
4277 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4278 ty::Closure(def_id, substs) => {
4279 // We don't use `closure_sig` to account for malformed closures like
4280 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4281 let closure_sig_ty = substs.as_closure().sig_ty(def_id, self.tcx);
4282 (def_id, match closure_sig_ty.kind {
4283 ty::FnPtr(sig) => sig,
4291 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4293 let sig = self.normalize_associated_types_in(expr.span, &sig);
4294 if self.can_coerce(sig.output(), expected) {
4295 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4296 (String::new(), Applicability::MachineApplicable)
4298 ("...".to_string(), Applicability::HasPlaceholders)
4300 let mut msg = "call this function";
4301 match hir.get_if_local(def_id) {
4302 Some(Node::Item(hir::Item {
4303 kind: ItemKind::Fn(.., body_id),
4306 Some(Node::ImplItem(hir::ImplItem {
4307 kind: hir::ImplItemKind::Method(_, body_id),
4310 Some(Node::TraitItem(hir::TraitItem {
4311 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4314 let body = hir.body(*body_id);
4315 sugg_call = body.params.iter()
4316 .map(|param| match ¶m.pat.kind {
4317 hir::PatKind::Binding(_, _, ident, None)
4318 if ident.name != kw::SelfLower => ident.to_string(),
4319 _ => "_".to_string(),
4320 }).collect::<Vec<_>>().join(", ");
4322 Some(Node::Expr(hir::Expr {
4323 kind: ExprKind::Closure(_, _, body_id, closure_span, _),
4324 span: full_closure_span,
4327 if *full_closure_span == expr.span {
4330 err.span_label(*closure_span, "closure defined here");
4331 msg = "call this closure";
4332 let body = hir.body(*body_id);
4333 sugg_call = body.params.iter()
4334 .map(|param| match ¶m.pat.kind {
4335 hir::PatKind::Binding(_, _, ident, None)
4336 if ident.name != kw::SelfLower => ident.to_string(),
4337 _ => "_".to_string(),
4338 }).collect::<Vec<_>>().join(", ");
4340 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4341 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4342 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4343 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4344 msg = "instantiate this tuple variant";
4346 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4347 msg = "instantiate this tuple struct";
4352 Some(Node::ForeignItem(hir::ForeignItem {
4353 kind: hir::ForeignItemKind::Fn(_, idents, _),
4356 Some(Node::TraitItem(hir::TraitItem {
4357 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4359 })) => sugg_call = idents.iter()
4360 .map(|ident| if ident.name != kw::SelfLower {
4364 }).collect::<Vec<_>>()
4368 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4369 err.span_suggestion(
4371 &format!("use parentheses to {}", msg),
4372 format!("{}({})", code, sugg_call),
4381 pub fn suggest_ref_or_into(
4383 err: &mut DiagnosticBuilder<'tcx>,
4388 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4389 err.span_suggestion(
4393 Applicability::MachineApplicable,
4395 } else if let (ty::FnDef(def_id, ..), true) = (
4397 self.suggest_fn_call(err, expr, expected, found),
4399 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4400 let sp = self.sess().source_map().def_span(sp);
4401 err.span_label(sp, &format!("{} defined here", found));
4403 } else if !self.check_for_cast(err, expr, found, expected) {
4404 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4408 let methods = self.get_conversion_methods(expr.span, expected, found);
4409 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4410 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4411 .filter_map(|(receiver, method)| {
4412 let method_call = format!(".{}()", method.ident);
4413 if receiver.ends_with(&method_call) {
4414 None // do not suggest code that is already there (#53348)
4416 let method_call_list = [".to_vec()", ".to_string()"];
4417 let sugg = if receiver.ends_with(".clone()")
4418 && method_call_list.contains(&method_call.as_str()) {
4419 let max_len = receiver.rfind(".").unwrap();
4420 format!("{}{}", &receiver[..max_len], method_call)
4422 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
4423 format!("({}){}", receiver, method_call)
4425 format!("{}{}", receiver, method_call)
4428 Some(if is_struct_pat_shorthand_field {
4429 format!("{}: {}", receiver, sugg)
4435 if suggestions.peek().is_some() {
4436 err.span_suggestions(
4438 "try using a conversion method",
4440 Applicability::MaybeIncorrect,
4447 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4448 /// in the heap by calling `Box::new()`.
4449 fn suggest_boxing_when_appropriate(
4451 err: &mut DiagnosticBuilder<'tcx>,
4456 if self.tcx.hir().is_const_context(expr.hir_id) {
4457 // Do not suggest `Box::new` in const context.
4460 if !expected.is_box() || found.is_box() {
4463 let boxed_found = self.tcx.mk_box(found);
4464 if let (true, Ok(snippet)) = (
4465 self.can_coerce(boxed_found, expected),
4466 self.sess().source_map().span_to_snippet(expr.span),
4468 err.span_suggestion(
4470 "store this in the heap by calling `Box::new`",
4471 format!("Box::new({})", snippet),
4472 Applicability::MachineApplicable,
4474 err.note("for more on the distinction between the stack and the \
4475 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4476 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4477 https://doc.rust-lang.org/std/boxed/index.html");
4482 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4486 /// bar_that_returns_u32()
4490 /// This routine checks if the return expression in a block would make sense on its own as a
4491 /// statement and the return type has been left as default or has been specified as `()`. If so,
4492 /// it suggests adding a semicolon.
4493 fn suggest_missing_semicolon(
4495 err: &mut DiagnosticBuilder<'tcx>,
4496 expression: &'tcx hir::Expr,
4500 if expected.is_unit() {
4501 // `BlockTailExpression` only relevant if the tail expr would be
4502 // useful on its own.
4503 match expression.kind {
4504 ExprKind::Call(..) |
4505 ExprKind::MethodCall(..) |
4506 ExprKind::Loop(..) |
4507 ExprKind::Match(..) |
4508 ExprKind::Block(..) => {
4509 let sp = self.tcx.sess.source_map().next_point(cause_span);
4510 err.span_suggestion(
4512 "try adding a semicolon",
4514 Applicability::MachineApplicable);
4521 /// A possible error is to forget to add a return type that is needed:
4525 /// bar_that_returns_u32()
4529 /// This routine checks if the return type is left as default, the method is not part of an
4530 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4532 fn suggest_missing_return_type(
4534 err: &mut DiagnosticBuilder<'tcx>,
4535 fn_decl: &hir::FnDecl,
4540 // Only suggest changing the return type for methods that
4541 // haven't set a return type at all (and aren't `fn main()` or an impl).
4542 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4543 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4544 err.span_suggestion(
4546 "try adding a return type",
4547 format!("-> {} ", self.resolve_vars_with_obligations(found)),
4548 Applicability::MachineApplicable);
4551 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4552 err.span_label(span, "possibly return type missing here?");
4555 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4556 // `fn main()` must return `()`, do not suggest changing return type
4557 err.span_label(span, "expected `()` because of default return type");
4560 // expectation was caused by something else, not the default return
4561 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4562 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4563 // Only point to return type if the expected type is the return type, as if they
4564 // are not, the expectation must have been caused by something else.
4565 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
4567 let ty = AstConv::ast_ty_to_ty(self, ty);
4568 debug!("suggest_missing_return_type: return type {:?}", ty);
4569 debug!("suggest_missing_return_type: expected type {:?}", ty);
4570 if ty.kind == expected.kind {
4571 err.span_label(sp, format!("expected `{}` because of return type",
4580 /// A possible error is to forget to add `.await` when using futures:
4583 /// async fn make_u32() -> u32 {
4587 /// fn take_u32(x: u32) {}
4589 /// async fn foo() {
4590 /// let x = make_u32();
4595 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4596 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4597 /// `.await` to the tail of the expression.
4598 fn suggest_missing_await(
4600 err: &mut DiagnosticBuilder<'tcx>,
4605 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4606 // body isn't `async`.
4607 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4608 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4609 let body = self.tcx().hir().body(body_id);
4610 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
4612 // Check for `Future` implementations by constructing a predicate to
4613 // prove: `<T as Future>::Output == U`
4614 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4615 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4616 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4617 // `<T as Future>::Output`
4618 projection_ty: ty::ProjectionTy {
4620 substs: self.tcx.mk_substs_trait(
4622 self.fresh_substs_for_item(sp, item_def_id)
4629 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4630 if self.infcx.predicate_may_hold(&obligation) {
4631 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4632 err.span_suggestion(
4634 "consider using `.await` here",
4635 format!("{}.await", code),
4636 Applicability::MaybeIncorrect,
4644 /// A common error is to add an extra semicolon:
4647 /// fn foo() -> usize {
4652 /// This routine checks if the final statement in a block is an
4653 /// expression with an explicit semicolon whose type is compatible
4654 /// with `expected_ty`. If so, it suggests removing the semicolon.
4655 fn consider_hint_about_removing_semicolon(
4657 blk: &'tcx hir::Block,
4658 expected_ty: Ty<'tcx>,
4659 err: &mut DiagnosticBuilder<'_>,
4661 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4662 err.span_suggestion(
4664 "consider removing this semicolon",
4666 Applicability::MachineApplicable,
4671 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4672 // Be helpful when the user wrote `{... expr;}` and
4673 // taking the `;` off is enough to fix the error.
4674 let last_stmt = blk.stmts.last()?;
4675 let last_expr = match last_stmt.kind {
4676 hir::StmtKind::Semi(ref e) => e,
4679 let last_expr_ty = self.node_ty(last_expr.hir_id);
4680 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4683 let original_span = original_sp(last_stmt.span, blk.span);
4684 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4687 // Instantiates the given path, which must refer to an item with the given
4688 // number of type parameters and type.
4689 pub fn instantiate_value_path(&self,
4690 segments: &[hir::PathSegment],
4691 self_ty: Option<Ty<'tcx>>,
4695 -> (Ty<'tcx>, Res) {
4697 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4706 let path_segs = match res {
4707 Res::Local(_) | Res::SelfCtor(_) => vec![],
4708 Res::Def(kind, def_id) =>
4709 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4710 _ => bug!("instantiate_value_path on {:?}", res),
4713 let mut user_self_ty = None;
4714 let mut is_alias_variant_ctor = false;
4716 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4717 if let Some(self_ty) = self_ty {
4718 let adt_def = self_ty.ty_adt_def().unwrap();
4719 user_self_ty = Some(UserSelfTy {
4720 impl_def_id: adt_def.did,
4723 is_alias_variant_ctor = true;
4726 Res::Def(DefKind::Method, def_id)
4727 | Res::Def(DefKind::AssocConst, def_id) => {
4728 let container = tcx.associated_item(def_id).container;
4729 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4731 ty::TraitContainer(trait_did) => {
4732 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4734 ty::ImplContainer(impl_def_id) => {
4735 if segments.len() == 1 {
4736 // `<T>::assoc` will end up here, and so
4737 // can `T::assoc`. It this came from an
4738 // inherent impl, we need to record the
4739 // `T` for posterity (see `UserSelfTy` for
4741 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4742 user_self_ty = Some(UserSelfTy {
4753 // Now that we have categorized what space the parameters for each
4754 // segment belong to, let's sort out the parameters that the user
4755 // provided (if any) into their appropriate spaces. We'll also report
4756 // errors if type parameters are provided in an inappropriate place.
4758 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4759 let generics_has_err = AstConv::prohibit_generics(
4760 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4761 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4768 if let Res::Local(hid) = res {
4769 let ty = self.local_ty(span, hid).decl_ty;
4770 let ty = self.normalize_associated_types_in(span, &ty);
4771 self.write_ty(hir_id, ty);
4775 if generics_has_err {
4776 // Don't try to infer type parameters when prohibited generic arguments were given.
4777 user_self_ty = None;
4780 // Now we have to compare the types that the user *actually*
4781 // provided against the types that were *expected*. If the user
4782 // did not provide any types, then we want to substitute inference
4783 // variables. If the user provided some types, we may still need
4784 // to add defaults. If the user provided *too many* types, that's
4787 let mut infer_args_for_err = FxHashSet::default();
4788 for &PathSeg(def_id, index) in &path_segs {
4789 let seg = &segments[index];
4790 let generics = tcx.generics_of(def_id);
4791 // Argument-position `impl Trait` is treated as a normal generic
4792 // parameter internally, but we don't allow users to specify the
4793 // parameter's value explicitly, so we have to do some error-
4795 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4800 false, // `is_method_call`
4802 if suppress_errors {
4803 infer_args_for_err.insert(index);
4804 self.set_tainted_by_errors(); // See issue #53251.
4808 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4809 tcx.generics_of(*def_id).has_self
4810 }).unwrap_or(false);
4812 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4813 let ty = self.impl_self_ty(span, impl_def_id).ty;
4814 let adt_def = ty.ty_adt_def();
4817 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4818 let variant = adt_def.non_enum_variant();
4819 let ctor_def_id = variant.ctor_def_id.unwrap();
4821 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4826 let mut err = tcx.sess.struct_span_err(span,
4827 "the `Self` constructor can only be used with tuple or unit structs");
4828 if let Some(adt_def) = adt_def {
4829 match adt_def.adt_kind() {
4831 err.help("did you mean to use one of the enum's variants?");
4835 err.span_suggestion(
4837 "use curly brackets",
4838 String::from("Self { /* fields */ }"),
4839 Applicability::HasPlaceholders,
4846 return (tcx.types.err, res)
4852 let def_id = res.def_id();
4854 // The things we are substituting into the type should not contain
4855 // escaping late-bound regions, and nor should the base type scheme.
4856 let ty = tcx.type_of(def_id);
4858 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4864 // Provide the generic args, and whether types should be inferred.
4866 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4869 // If we've encountered an `impl Trait`-related error, we're just
4870 // going to infer the arguments for better error messages.
4871 if !infer_args_for_err.contains(&index) {
4872 // Check whether the user has provided generic arguments.
4873 if let Some(ref data) = segments[index].args {
4874 return (Some(data), segments[index].infer_args);
4877 return (None, segments[index].infer_args);
4882 // Provide substitutions for parameters for which (valid) arguments have been provided.
4884 match (¶m.kind, arg) {
4885 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4886 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4888 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4889 self.to_ty(ty).into()
4891 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4892 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4894 _ => unreachable!(),
4897 // Provide substitutions for parameters for which arguments are inferred.
4898 |substs, param, infer_args| {
4900 GenericParamDefKind::Lifetime => {
4901 self.re_infer(Some(param), span).unwrap().into()
4903 GenericParamDefKind::Type { has_default, .. } => {
4904 if !infer_args && has_default {
4905 // If we have a default, then we it doesn't matter that we're not
4906 // inferring the type arguments: we provide the default where any
4908 let default = tcx.type_of(param.def_id);
4911 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4914 // If no type arguments were provided, we have to infer them.
4915 // This case also occurs as a result of some malformed input, e.g.
4916 // a lifetime argument being given instead of a type parameter.
4917 // Using inference instead of `Error` gives better error messages.
4918 self.var_for_def(span, param)
4921 GenericParamDefKind::Const => {
4922 // FIXME(const_generics:defaults)
4923 // No const parameters were provided, we have to infer them.
4924 self.var_for_def(span, param)
4929 assert!(!substs.has_escaping_bound_vars());
4930 assert!(!ty.has_escaping_bound_vars());
4932 // First, store the "user substs" for later.
4933 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4935 self.add_required_obligations(span, def_id, &substs);
4937 // Substitute the values for the type parameters into the type of
4938 // the referenced item.
4939 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4941 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4942 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4943 // is inherent, there is no `Self` parameter; instead, the impl needs
4944 // type parameters, which we can infer by unifying the provided `Self`
4945 // with the substituted impl type.
4946 // This also occurs for an enum variant on a type alias.
4947 let ty = tcx.type_of(impl_def_id);
4949 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4950 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4951 Ok(ok) => self.register_infer_ok_obligations(ok),
4953 self.tcx.sess.delay_span_bug(span, &format!(
4954 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4962 self.check_rustc_args_require_const(def_id, hir_id, span);
4964 debug!("instantiate_value_path: type of {:?} is {:?}",
4967 self.write_substs(hir_id, substs);
4969 (ty_substituted, res)
4972 /// Add all the obligations that are required, substituting and normalized appropriately.
4973 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
4974 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
4976 for (i, mut obligation) in traits::predicates_for_generics(
4977 traits::ObligationCause::new(
4980 traits::ItemObligation(def_id),
4984 ).into_iter().enumerate() {
4985 // This makes the error point at the bound, but we want to point at the argument
4986 if let Some(span) = spans.get(i) {
4987 obligation.cause.code = traits::BindingObligation(def_id, *span);
4989 self.register_predicate(obligation);
4993 fn check_rustc_args_require_const(&self,
4997 // We're only interested in functions tagged with
4998 // #[rustc_args_required_const], so ignore anything that's not.
4999 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5003 // If our calling expression is indeed the function itself, we're good!
5004 // If not, generate an error that this can only be called directly.
5005 if let Node::Expr(expr) = self.tcx.hir().get(
5006 self.tcx.hir().get_parent_node(hir_id))
5008 if let ExprKind::Call(ref callee, ..) = expr.kind {
5009 if callee.hir_id == hir_id {
5015 self.tcx.sess.span_err(span, "this function can only be invoked \
5016 directly, not through a function pointer");
5019 // Resolves `typ` by a single level if `typ` is a type variable.
5020 // If no resolution is possible, then an error is reported.
5021 // Numeric inference variables may be left unresolved.
5022 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5023 let ty = self.resolve_vars_with_obligations(ty);
5024 if !ty.is_ty_var() {
5027 if !self.is_tainted_by_errors() {
5028 self.need_type_info_err((**self).body_id, sp, ty)
5029 .note("type must be known at this point")
5032 self.demand_suptype(sp, self.tcx.types.err, ty);
5037 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5040 ctxt: BreakableCtxt<'tcx>,
5042 ) -> (BreakableCtxt<'tcx>, R) {
5045 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5046 index = enclosing_breakables.stack.len();
5047 enclosing_breakables.by_id.insert(id, index);
5048 enclosing_breakables.stack.push(ctxt);
5052 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5053 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5054 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5055 enclosing_breakables.stack.pop().expect("missing breakable context")
5060 /// Instantiate a QueryResponse in a probe context, without a
5061 /// good ObligationCause.
5062 fn probe_instantiate_query_response(
5065 original_values: &OriginalQueryValues<'tcx>,
5066 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5067 ) -> InferResult<'tcx, Ty<'tcx>>
5069 self.instantiate_query_response_and_region_obligations(
5070 &traits::ObligationCause::misc(span, self.body_id),
5076 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5077 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5078 let mut contained_in_place = false;
5080 while let hir::Node::Expr(parent_expr) =
5081 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5083 match &parent_expr.kind {
5084 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5085 if lhs.hir_id == expr_id {
5086 contained_in_place = true;
5092 expr_id = parent_expr.hir_id;
5099 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5100 let own_counts = generics.own_counts();
5102 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5108 if own_counts.types == 0 {
5112 // Make a vector of booleans initially `false`; set to `true` when used.
5113 let mut types_used = vec![false; own_counts.types];
5115 for leaf_ty in ty.walk() {
5116 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.kind {
5117 debug!("found use of ty param num {}", index);
5118 types_used[index as usize - own_counts.lifetimes] = true;
5119 } else if let ty::Error = leaf_ty.kind {
5120 // If there is already another error, do not emit
5121 // an error for not using a type parameter.
5122 assert!(tcx.sess.has_errors());
5127 let types = generics.params.iter().filter(|param| match param.kind {
5128 ty::GenericParamDefKind::Type { .. } => true,
5131 for (&used, param) in types_used.iter().zip(types) {
5133 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5134 let span = tcx.hir().span(id);
5135 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5136 .span_label(span, "unused type parameter")
5142 fn fatally_break_rust(sess: &Session) {
5143 let handler = sess.diagnostic();
5144 handler.span_bug_no_panic(
5146 "It looks like you're trying to break rust; would you like some ICE?",
5148 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5149 handler.note_without_error(
5150 "we would appreciate a joke overview: \
5151 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5153 handler.note_without_error(&format!("rustc {} running on {}",
5154 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5155 crate::session::config::host_triple(),
5159 fn potentially_plural_count(count: usize, word: &str) -> String {
5160 format!("{} {}{}", count, word, pluralise!(count))