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 self.opt_find_breakable(target_id).unwrap_or_else(|| {
540 bug!("could not find enclosing breakable with id {}", target_id);
544 fn opt_find_breakable(&mut self, target_id: hir::HirId) -> Option<&mut BreakableCtxt<'tcx>> {
545 match self.by_id.get(&target_id) {
546 Some(ix) => Some(&mut self.stack[*ix]),
552 pub struct FnCtxt<'a, 'tcx> {
555 /// The parameter environment used for proving trait obligations
556 /// in this function. This can change when we descend into
557 /// closures (as they bring new things into scope), hence it is
558 /// not part of `Inherited` (as of the time of this writing,
559 /// closures do not yet change the environment, but they will
561 param_env: ty::ParamEnv<'tcx>,
563 /// Number of errors that had been reported when we started
564 /// checking this function. On exit, if we find that *more* errors
565 /// have been reported, we will skip regionck and other work that
566 /// expects the types within the function to be consistent.
567 // FIXME(matthewjasper) This should not exist, and it's not correct
568 // if type checking is run in parallel.
569 err_count_on_creation: usize,
571 /// If `Some`, this stores coercion information for returned
572 /// expressions. If `None`, this is in a context where return is
573 /// inappropriate, such as a const expression.
575 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
576 /// can track all the return expressions and then use them to
577 /// compute a useful coercion from the set, similar to a match
578 /// expression or other branching context. You can use methods
579 /// like `expected_ty` to access the declared return type (if
581 ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
583 /// First span of a return site that we find. Used in error messages.
584 ret_coercion_span: RefCell<Option<Span>>,
586 yield_ty: Option<Ty<'tcx>>,
588 ps: RefCell<UnsafetyState>,
590 /// Whether the last checked node generates a divergence (e.g.,
591 /// `return` will set this to `Always`). In general, when entering
592 /// an expression or other node in the tree, the initial value
593 /// indicates whether prior parts of the containing expression may
594 /// have diverged. It is then typically set to `Maybe` (and the
595 /// old value remembered) for processing the subparts of the
596 /// current expression. As each subpart is processed, they may set
597 /// the flag to `Always`, etc. Finally, at the end, we take the
598 /// result and "union" it with the original value, so that when we
599 /// return the flag indicates if any subpart of the parent
600 /// expression (up to and including this part) has diverged. So,
601 /// if you read it after evaluating a subexpression `X`, the value
602 /// you get indicates whether any subexpression that was
603 /// evaluating up to and including `X` diverged.
605 /// We currently use this flag only for diagnostic purposes:
607 /// - To warn about unreachable code: if, after processing a
608 /// sub-expression but before we have applied the effects of the
609 /// current node, we see that the flag is set to `Always`, we
610 /// can issue a warning. This corresponds to something like
611 /// `foo(return)`; we warn on the `foo()` expression. (We then
612 /// update the flag to `WarnedAlways` to suppress duplicate
613 /// reports.) Similarly, if we traverse to a fresh statement (or
614 /// tail expression) from a `Always` setting, we will issue a
615 /// warning. This corresponds to something like `{return;
616 /// foo();}` or `{return; 22}`, where we would warn on the
619 /// An expression represents dead code if, after checking it,
620 /// the diverges flag is set to something other than `Maybe`.
621 diverges: Cell<Diverges>,
623 /// Whether any child nodes have any type errors.
624 has_errors: Cell<bool>,
626 enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
628 inh: &'a Inherited<'a, 'tcx>,
631 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
632 type Target = Inherited<'a, 'tcx>;
633 fn deref(&self) -> &Self::Target {
638 /// Helper type of a temporary returned by `Inherited::build(...)`.
639 /// Necessary because we can't write the following bound:
640 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
641 pub struct InheritedBuilder<'tcx> {
642 infcx: infer::InferCtxtBuilder<'tcx>,
646 impl Inherited<'_, 'tcx> {
647 pub fn build(tcx: TyCtxt<'tcx>, def_id: DefId) -> InheritedBuilder<'tcx> {
648 let hir_id_root = if def_id.is_local() {
649 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
650 DefId::local(hir_id.owner)
656 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
662 impl<'tcx> InheritedBuilder<'tcx> {
663 fn enter<F, R>(&mut self, f: F) -> R
665 F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
667 let def_id = self.def_id;
668 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
672 impl Inherited<'a, 'tcx> {
673 fn new(infcx: InferCtxt<'a, 'tcx>, def_id: DefId) -> Self {
675 let item_id = tcx.hir().as_local_hir_id(def_id);
676 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by(id));
677 let implicit_region_bound = body_id.map(|body_id| {
678 let body = tcx.hir().body(body_id);
679 tcx.mk_region(ty::ReScope(region::Scope {
680 id: body.value.hir_id.local_id,
681 data: region::ScopeData::CallSite
686 tables: MaybeInProgressTables {
687 maybe_tables: infcx.in_progress_tables,
690 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
691 locals: RefCell::new(Default::default()),
692 deferred_sized_obligations: RefCell::new(Vec::new()),
693 deferred_call_resolutions: RefCell::new(Default::default()),
694 deferred_cast_checks: RefCell::new(Vec::new()),
695 deferred_generator_interiors: RefCell::new(Vec::new()),
696 opaque_types: RefCell::new(Default::default()),
697 implicit_region_bound,
702 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
703 debug!("register_predicate({:?})", obligation);
704 if obligation.has_escaping_bound_vars() {
705 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}",
710 .register_predicate_obligation(self, obligation);
713 fn register_predicates<I>(&self, obligations: I)
714 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>>
716 for obligation in obligations {
717 self.register_predicate(obligation);
721 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
722 self.register_predicates(infer_ok.obligations);
726 fn normalize_associated_types_in<T>(&self,
729 param_env: ty::ParamEnv<'tcx>,
731 where T : TypeFoldable<'tcx>
733 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
734 self.register_infer_ok_obligations(ok)
738 struct CheckItemTypesVisitor<'tcx> {
742 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
743 fn visit_item(&mut self, i: &'tcx hir::Item) {
744 check_item_type(self.tcx, i);
746 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
747 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
750 pub fn check_wf_new(tcx: TyCtxt<'_>) {
751 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
752 tcx.hir().krate().par_visit_all_item_likes(&mut visit);
755 fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
756 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
759 fn typeck_item_bodies(tcx: TyCtxt<'_>, crate_num: CrateNum) {
760 debug_assert!(crate_num == LOCAL_CRATE);
761 tcx.par_body_owners(|body_owner_def_id| {
762 tcx.ensure().typeck_tables_of(body_owner_def_id);
766 fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
767 wfcheck::check_item_well_formed(tcx, def_id);
770 fn check_trait_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
771 wfcheck::check_trait_item(tcx, def_id);
774 fn check_impl_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
775 wfcheck::check_impl_item(tcx, def_id);
778 pub fn provide(providers: &mut Providers<'_>) {
779 method::provide(providers);
780 *providers = Providers {
786 check_item_well_formed,
787 check_trait_item_well_formed,
788 check_impl_item_well_formed,
789 check_mod_item_types,
794 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
795 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
798 /// If this `DefId` is a "primary tables entry", returns
799 /// `Some((body_id, header, decl))` with information about
800 /// it's body-id, fn-header and fn-decl (if any). Otherwise,
803 /// If this function returns `Some`, then `typeck_tables(def_id)` will
804 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
805 /// may not succeed. In some cases where this function returns `None`
806 /// (notably closures), `typeck_tables(def_id)` would wind up
807 /// redirecting to the owning function.
811 ) -> Option<(hir::BodyId, Option<&hir::Ty>, Option<&hir::FnHeader>, Option<&hir::FnDecl>)> {
812 match tcx.hir().get(id) {
813 Node::Item(item) => {
815 hir::ItemKind::Const(ref ty, body) |
816 hir::ItemKind::Static(ref ty, _, body) =>
817 Some((body, Some(ty), None, None)),
818 hir::ItemKind::Fn(ref decl, ref header, .., body) =>
819 Some((body, None, Some(header), Some(decl))),
824 Node::TraitItem(item) => {
826 hir::TraitItemKind::Const(ref ty, Some(body)) =>
827 Some((body, Some(ty), None, None)),
828 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
829 Some((body, None, Some(&sig.header), Some(&sig.decl))),
834 Node::ImplItem(item) => {
836 hir::ImplItemKind::Const(ref ty, body) =>
837 Some((body, Some(ty), None, None)),
838 hir::ImplItemKind::Method(ref sig, body) =>
839 Some((body, None, Some(&sig.header), Some(&sig.decl))),
844 Node::AnonConst(constant) => Some((constant.body, None, None, None)),
849 fn has_typeck_tables(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
850 // Closures' tables come from their outermost function,
851 // as they are part of the same "inference environment".
852 let outer_def_id = tcx.closure_base_def_id(def_id);
853 if outer_def_id != def_id {
854 return tcx.has_typeck_tables(outer_def_id);
857 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
858 primary_body_of(tcx, id).is_some()
861 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: DefId) -> &DefIdSet {
862 &*tcx.typeck_tables_of(def_id).used_trait_imports
865 fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
866 // Closures' tables come from their outermost function,
867 // as they are part of the same "inference environment".
868 let outer_def_id = tcx.closure_base_def_id(def_id);
869 if outer_def_id != def_id {
870 return tcx.typeck_tables_of(outer_def_id);
873 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
874 let span = tcx.hir().span(id);
876 // Figure out what primary body this item has.
877 let (body_id, body_ty, fn_header, fn_decl) = primary_body_of(tcx, id)
879 span_bug!(span, "can't type-check body of {:?}", def_id);
881 let body = tcx.hir().body(body_id);
883 let tables = Inherited::build(tcx, def_id).enter(|inh| {
884 let param_env = tcx.param_env(def_id);
885 let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
886 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
887 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
888 AstConv::ty_of_fn(&fcx, header.unsafety, header.abi, decl)
893 check_abi(tcx, span, fn_sig.abi());
895 // Compute the fty from point of view of inside the fn.
897 tcx.liberate_late_bound_regions(def_id, &fn_sig);
899 inh.normalize_associated_types_in(body.value.span,
904 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
907 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
908 let expected_type = body_ty.and_then(|ty| match ty.kind {
909 hir::TyKind::Infer => Some(AstConv::ast_ty_to_ty(&fcx, ty)),
911 }).unwrap_or_else(|| tcx.type_of(def_id));
912 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
913 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
915 let revealed_ty = if tcx.features().impl_trait_in_bindings {
916 fcx.instantiate_opaque_types_from_value(
925 // Gather locals in statics (because of block expressions).
926 GatherLocalsVisitor { fcx: &fcx, parent_id: id, }.visit_body(body);
928 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
930 fcx.write_ty(id, revealed_ty);
935 // All type checking constraints were added, try to fallback unsolved variables.
936 fcx.select_obligations_where_possible(false, |_| {});
937 let mut fallback_has_occurred = false;
938 for ty in &fcx.unsolved_variables() {
939 fallback_has_occurred |= fcx.fallback_if_possible(ty);
941 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
943 // Even though coercion casts provide type hints, we check casts after fallback for
944 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
947 // Closure and generator analysis may run after fallback
948 // because they don't constrain other type variables.
949 fcx.closure_analyze(body);
950 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
951 fcx.resolve_generator_interiors(def_id);
953 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
954 let ty = fcx.normalize_ty(span, ty);
955 fcx.require_type_is_sized(ty, span, code);
957 fcx.select_all_obligations_or_error();
959 if fn_decl.is_some() {
960 fcx.regionck_fn(id, body);
962 fcx.regionck_expr(body);
965 fcx.resolve_type_vars_in_body(body)
968 // Consistency check our TypeckTables instance can hold all ItemLocalIds
969 // it will need to hold.
970 assert_eq!(tables.local_id_root, Some(DefId::local(id.owner)));
975 fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
976 if !tcx.sess.target.target.is_abi_supported(abi) {
977 struct_span_err!(tcx.sess, span, E0570,
978 "The ABI `{}` is not supported for the current target", abi).emit()
982 struct GatherLocalsVisitor<'a, 'tcx> {
983 fcx: &'a FnCtxt<'a, 'tcx>,
984 parent_id: hir::HirId,
987 impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
988 fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
991 // infer the variable's type
992 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
993 kind: TypeVariableOriginKind::TypeInference,
996 self.fcx.locals.borrow_mut().insert(nid, LocalTy {
1003 // take type that the user specified
1004 self.fcx.locals.borrow_mut().insert(nid, typ);
1011 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
1012 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1013 NestedVisitorMap::None
1016 // Add explicitly-declared locals.
1017 fn visit_local(&mut self, local: &'tcx hir::Local) {
1018 let local_ty = match local.ty {
1020 let o_ty = self.fcx.to_ty(&ty);
1022 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
1023 self.fcx.instantiate_opaque_types_from_value(
1032 let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(
1033 &UserType::Ty(revealed_ty)
1035 debug!("visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
1036 ty.hir_id, o_ty, revealed_ty, c_ty);
1037 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
1039 Some(LocalTy { decl_ty: o_ty, revealed_ty })
1043 self.assign(local.span, local.hir_id, local_ty);
1045 debug!("local variable {:?} is assigned type {}",
1047 self.fcx.ty_to_string(
1048 self.fcx.locals.borrow().get(&local.hir_id).unwrap().clone().decl_ty));
1049 intravisit::walk_local(self, local);
1052 // Add pattern bindings.
1053 fn visit_pat(&mut self, p: &'tcx hir::Pat) {
1054 if let PatKind::Binding(_, _, ident, _) = p.kind {
1055 let var_ty = self.assign(p.span, p.hir_id, None);
1057 if !self.fcx.tcx.features().unsized_locals {
1058 self.fcx.require_type_is_sized(var_ty, p.span,
1059 traits::VariableType(p.hir_id));
1062 debug!("pattern binding {} is assigned to {} with type {:?}",
1064 self.fcx.ty_to_string(
1065 self.fcx.locals.borrow().get(&p.hir_id).unwrap().clone().decl_ty),
1068 intravisit::walk_pat(self, p);
1071 // Don't descend into the bodies of nested closures
1074 _: intravisit::FnKind<'tcx>,
1075 _: &'tcx hir::FnDecl,
1082 /// When `check_fn` is invoked on a generator (i.e., a body that
1083 /// includes yield), it returns back some information about the yield
1085 struct GeneratorTypes<'tcx> {
1086 /// Type of value that is yielded.
1089 /// Types that are captured (see `GeneratorInterior` for more).
1092 /// Indicates if the generator is movable or static (immovable).
1093 movability: hir::GeneratorMovability,
1096 /// Helper used for fns and closures. Does the grungy work of checking a function
1097 /// body and returns the function context used for that purpose, since in the case of a fn item
1098 /// there is still a bit more to do.
1101 /// * inherited: other fields inherited from the enclosing fn (if any)
1102 fn check_fn<'a, 'tcx>(
1103 inherited: &'a Inherited<'a, 'tcx>,
1104 param_env: ty::ParamEnv<'tcx>,
1105 fn_sig: ty::FnSig<'tcx>,
1106 decl: &'tcx hir::FnDecl,
1108 body: &'tcx hir::Body,
1109 can_be_generator: Option<hir::GeneratorMovability>,
1110 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
1111 let mut fn_sig = fn_sig.clone();
1113 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1115 // Create the function context. This is either derived from scratch or,
1116 // in the case of closures, based on the outer context.
1117 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1118 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1120 let declared_ret_ty = fn_sig.output();
1121 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1122 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(
1127 debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
1128 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1129 fn_sig = fcx.tcx.mk_fn_sig(
1130 fn_sig.inputs().iter().cloned(),
1137 let span = body.value.span;
1139 fn_maybe_err(fcx.tcx, span, fn_sig.abi);
1141 if body.generator_kind.is_some() && can_be_generator.is_some() {
1142 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
1143 kind: TypeVariableOriginKind::TypeInference,
1146 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1147 fcx.yield_ty = Some(yield_ty);
1150 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id(fn_id));
1151 let outer_hir_id = fcx.tcx.hir().as_local_hir_id(outer_def_id).unwrap();
1152 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id, }.visit_body(body);
1154 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
1155 // (as it's created inside the body itself, not passed in from outside).
1156 let maybe_va_list = if fn_sig.c_variadic {
1157 let va_list_did = fcx.tcx.require_lang_item(
1158 lang_items::VaListTypeLangItem,
1159 Some(body.params.last().unwrap().span),
1161 let region = fcx.tcx.mk_region(ty::ReScope(region::Scope {
1162 id: body.value.hir_id.local_id,
1163 data: region::ScopeData::CallSite
1166 Some(fcx.tcx.type_of(va_list_did).subst(fcx.tcx, &[region.into()]))
1171 // Add formal parameters.
1172 for (param_ty, param) in
1173 fn_sig.inputs().iter().copied()
1174 .chain(maybe_va_list)
1177 // Check the pattern.
1178 fcx.check_pat_top(¶m.pat, param_ty, None);
1180 // Check that argument is Sized.
1181 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1182 // for simple cases like `fn foo(x: Trait)`,
1183 // where we would error once on the parameter as a whole, and once on the binding `x`.
1184 if param.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1185 fcx.require_type_is_sized(param_ty, decl.output.span(), traits::SizedArgumentType);
1188 fcx.write_ty(param.hir_id, param_ty);
1191 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1193 fcx.check_return_expr(&body.value);
1195 // We insert the deferred_generator_interiors entry after visiting the body.
1196 // This ensures that all nested generators appear before the entry of this generator.
1197 // resolve_generator_interiors relies on this property.
1198 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
1199 let interior = fcx.next_ty_var(TypeVariableOrigin {
1200 kind: TypeVariableOriginKind::MiscVariable,
1203 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
1204 Some(GeneratorTypes {
1205 yield_ty: fcx.yield_ty.unwrap(),
1207 movability: can_be_generator.unwrap(),
1213 // Finalize the return check by taking the LUB of the return types
1214 // we saw and assigning it to the expected return type. This isn't
1215 // really expected to fail, since the coercions would have failed
1216 // earlier when trying to find a LUB.
1218 // However, the behavior around `!` is sort of complex. In the
1219 // event that the `actual_return_ty` comes back as `!`, that
1220 // indicates that the fn either does not return or "returns" only
1221 // values of type `!`. In this case, if there is an expected
1222 // return type that is *not* `!`, that should be ok. But if the
1223 // return type is being inferred, we want to "fallback" to `!`:
1225 // let x = move || panic!();
1227 // To allow for that, I am creating a type variable with diverging
1228 // fallback. This was deemed ever so slightly better than unifying
1229 // the return value with `!` because it allows for the caller to
1230 // make more assumptions about the return type (e.g., they could do
1232 // let y: Option<u32> = Some(x());
1234 // which would then cause this return type to become `u32`, not
1236 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1237 let mut actual_return_ty = coercion.complete(&fcx);
1238 if actual_return_ty.is_never() {
1239 actual_return_ty = fcx.next_diverging_ty_var(
1240 TypeVariableOrigin {
1241 kind: TypeVariableOriginKind::DivergingFn,
1246 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1248 // Check that the main return type implements the termination trait.
1249 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1250 if let Some((def_id, EntryFnType::Main)) = fcx.tcx.entry_fn(LOCAL_CRATE) {
1251 let main_id = fcx.tcx.hir().as_local_hir_id(def_id).unwrap();
1252 if main_id == fn_id {
1253 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1254 let trait_ref = ty::TraitRef::new(term_id, substs);
1255 let return_ty_span = decl.output.span();
1256 let cause = traits::ObligationCause::new(
1257 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1259 inherited.register_predicate(
1260 traits::Obligation::new(
1261 cause, param_env, trait_ref.to_predicate()));
1266 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1267 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1268 if panic_impl_did == fcx.tcx.hir().local_def_id(fn_id) {
1269 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1270 // at this point we don't care if there are duplicate handlers or if the handler has
1271 // the wrong signature as this value we'll be used when writing metadata and that
1272 // only happens if compilation succeeded
1273 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1275 if declared_ret_ty.kind != ty::Never {
1276 fcx.tcx.sess.span_err(
1278 "return type should be `!`",
1282 let inputs = fn_sig.inputs();
1283 let span = fcx.tcx.hir().span(fn_id);
1284 if inputs.len() == 1 {
1285 let arg_is_panic_info = match inputs[0].kind {
1286 ty::Ref(region, ty, mutbl) => match ty.kind {
1287 ty::Adt(ref adt, _) => {
1288 adt.did == panic_info_did &&
1289 mutbl == hir::Mutability::MutImmutable &&
1290 *region != RegionKind::ReStatic
1297 if !arg_is_panic_info {
1298 fcx.tcx.sess.span_err(
1299 decl.inputs[0].span,
1300 "argument should be `&PanicInfo`",
1304 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1305 if let ItemKind::Fn(_, _, ref generics, _) = item.kind {
1306 if !generics.params.is_empty() {
1307 fcx.tcx.sess.span_err(
1309 "should have no type parameters",
1315 let span = fcx.tcx.sess.source_map().def_span(span);
1316 fcx.tcx.sess.span_err(span, "function should have one argument");
1319 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1324 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1325 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1326 if alloc_error_handler_did == fcx.tcx.hir().local_def_id(fn_id) {
1327 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1328 if declared_ret_ty.kind != ty::Never {
1329 fcx.tcx.sess.span_err(
1331 "return type should be `!`",
1335 let inputs = fn_sig.inputs();
1336 let span = fcx.tcx.hir().span(fn_id);
1337 if inputs.len() == 1 {
1338 let arg_is_alloc_layout = match inputs[0].kind {
1339 ty::Adt(ref adt, _) => {
1340 adt.did == alloc_layout_did
1345 if !arg_is_alloc_layout {
1346 fcx.tcx.sess.span_err(
1347 decl.inputs[0].span,
1348 "argument should be `Layout`",
1352 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1353 if let ItemKind::Fn(_, _, ref generics, _) = item.kind {
1354 if !generics.params.is_empty() {
1355 fcx.tcx.sess.span_err(
1357 "`#[alloc_error_handler]` function should have no type \
1364 let span = fcx.tcx.sess.source_map().def_span(span);
1365 fcx.tcx.sess.span_err(span, "function should have one argument");
1368 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1376 fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1377 let def_id = tcx.hir().local_def_id(id);
1378 let def = tcx.adt_def(def_id);
1379 def.destructor(tcx); // force the destructor to be evaluated
1380 check_representable(tcx, span, def_id);
1382 if def.repr.simd() {
1383 check_simd(tcx, span, def_id);
1386 check_transparent(tcx, span, def_id);
1387 check_packed(tcx, span, def_id);
1390 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1391 let def_id = tcx.hir().local_def_id(id);
1392 let def = tcx.adt_def(def_id);
1393 def.destructor(tcx); // force the destructor to be evaluated
1394 check_representable(tcx, span, def_id);
1395 check_transparent(tcx, span, def_id);
1396 check_union_fields(tcx, span, def_id);
1397 check_packed(tcx, span, def_id);
1400 /// When the `#![feature(untagged_unions)]` gate is active,
1401 /// check that the fields of the `union` does not contain fields that need dropping.
1402 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: DefId) -> bool {
1403 let item_type = tcx.type_of(item_def_id);
1404 if let ty::Adt(def, substs) = item_type.kind {
1405 assert!(def.is_union());
1406 let fields = &def.non_enum_variant().fields;
1407 for field in fields {
1408 let field_ty = field.ty(tcx, substs);
1409 // We are currently checking the type this field came from, so it must be local.
1410 let field_span = tcx.hir().span_if_local(field.did).unwrap();
1411 let param_env = tcx.param_env(field.did);
1412 if field_ty.needs_drop(tcx, param_env) {
1413 struct_span_err!(tcx.sess, field_span, E0740,
1414 "unions may not contain fields that need dropping")
1415 .span_note(field_span,
1416 "`std::mem::ManuallyDrop` can be used to wrap the type")
1422 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind);
1427 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
1428 /// projections that would result in "inheriting lifetimes".
1429 fn check_opaque<'tcx>(
1432 substs: SubstsRef<'tcx>,
1434 origin: &hir::OpaqueTyOrigin,
1436 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
1437 check_opaque_for_cycles(tcx, def_id, substs, span, origin);
1440 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
1441 /// in "inheriting lifetimes".
1442 fn check_opaque_for_inheriting_lifetimes(
1447 let item = tcx.hir().expect_item(
1448 tcx.hir().as_local_hir_id(def_id).expect("opaque type is not local"));
1449 debug!("check_opaque_for_inheriting_lifetimes: def_id={:?} span={:?} item={:?}",
1450 def_id, span, item);
1453 struct ProhibitOpaqueVisitor<'tcx> {
1454 opaque_identity_ty: Ty<'tcx>,
1455 generics: &'tcx ty::Generics,
1458 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
1459 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
1460 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
1461 if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) }
1464 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1465 debug!("check_opaque_for_inheriting_lifetimes: (visit_region) r={:?}", r);
1466 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
1467 return *index < self.generics.parent_count as u32;
1470 r.super_visit_with(self)
1474 let prohibit_opaque = match item.kind {
1475 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn, .. }) |
1476 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn, .. }) => {
1477 let mut visitor = ProhibitOpaqueVisitor {
1478 opaque_identity_ty: tcx.mk_opaque(
1479 def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1480 generics: tcx.generics_of(def_id),
1482 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1484 tcx.predicates_of(def_id).predicates.iter().any(
1485 |(predicate, _)| predicate.visit_with(&mut visitor))
1490 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1491 if prohibit_opaque {
1492 let is_async = match item.kind {
1493 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1494 hir::OpaqueTyOrigin::AsyncFn => true,
1497 _ => unreachable!(),
1500 tcx.sess.span_err(span, &format!(
1501 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1503 if is_async { "async fn" } else { "impl Trait" },
1508 /// Checks that an opaque type does not contain cycles.
1509 fn check_opaque_for_cycles<'tcx>(
1512 substs: SubstsRef<'tcx>,
1514 origin: &hir::OpaqueTyOrigin,
1516 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1517 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1519 tcx.sess, span, E0733,
1520 "recursion in an `async fn` requires boxing",
1522 .span_label(span, "recursive `async fn`")
1523 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`.")
1526 let mut err = struct_span_err!(
1527 tcx.sess, span, E0720,
1528 "opaque type expands to a recursive type",
1530 err.span_label(span, "expands to a recursive type");
1531 if let ty::Opaque(..) = partially_expanded_type.kind {
1532 err.note("type resolves to itself");
1534 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1541 // Forbid defining intrinsics in Rust code,
1542 // as they must always be defined by the compiler.
1543 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1544 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1545 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1549 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
1551 "check_item_type(it.hir_id={}, it.name={})",
1553 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1555 let _indenter = indenter();
1557 // Consts can play a role in type-checking, so they are included here.
1558 hir::ItemKind::Static(..) => {
1559 let def_id = tcx.hir().local_def_id(it.hir_id);
1560 tcx.typeck_tables_of(def_id);
1561 maybe_check_static_with_link_section(tcx, def_id, it.span);
1563 hir::ItemKind::Const(..) => {
1564 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1566 hir::ItemKind::Enum(ref enum_definition, _) => {
1567 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1569 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1570 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1571 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1572 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1573 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1574 check_impl_items_against_trait(
1581 let trait_def_id = impl_trait_ref.def_id;
1582 check_on_unimplemented(tcx, trait_def_id, it);
1585 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1586 let def_id = tcx.hir().local_def_id(it.hir_id);
1587 check_on_unimplemented(tcx, def_id, it);
1589 for item in items.iter() {
1590 let item = tcx.hir().trait_item(item.id);
1591 if let hir::TraitItemKind::Method(sig, _) = &item.kind {
1592 let abi = sig.header.abi;
1593 fn_maybe_err(tcx, item.ident.span, abi);
1597 hir::ItemKind::Struct(..) => {
1598 check_struct(tcx, it.hir_id, it.span);
1600 hir::ItemKind::Union(..) => {
1601 check_union(tcx, it.hir_id, it.span);
1603 hir::ItemKind::OpaqueTy(hir::OpaqueTy{origin, ..}) => {
1604 let def_id = tcx.hir().local_def_id(it.hir_id);
1606 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1607 check_opaque(tcx, def_id, substs, it.span, &origin);
1609 hir::ItemKind::TyAlias(..) => {
1610 let def_id = tcx.hir().local_def_id(it.hir_id);
1611 let pty_ty = tcx.type_of(def_id);
1612 let generics = tcx.generics_of(def_id);
1613 check_bounds_are_used(tcx, &generics, pty_ty);
1615 hir::ItemKind::ForeignMod(ref m) => {
1616 check_abi(tcx, it.span, m.abi);
1618 if m.abi == Abi::RustIntrinsic {
1619 for item in &m.items {
1620 intrinsic::check_intrinsic_type(tcx, item);
1622 } else if m.abi == Abi::PlatformIntrinsic {
1623 for item in &m.items {
1624 intrinsic::check_platform_intrinsic_type(tcx, item);
1627 for item in &m.items {
1628 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1629 let own_counts = generics.own_counts();
1630 if generics.params.len() - own_counts.lifetimes != 0 {
1631 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1632 (_, 0) => ("type", "types", Some("u32")),
1633 // We don't specify an example value, because we can't generate
1634 // a valid value for any type.
1635 (0, _) => ("const", "consts", None),
1636 _ => ("type or const", "types or consts", None),
1642 "foreign items may not have {} parameters",
1646 &format!("can't have {} parameters", kinds),
1648 // FIXME: once we start storing spans for type arguments, turn this
1649 // into a suggestion.
1651 "replace the {} parameters with concrete {}{}",
1654 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1659 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.kind {
1660 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1665 _ => { /* nothing to do */ }
1669 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1670 // Only restricted on wasm32 target for now
1671 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1675 // If `#[link_section]` is missing, then nothing to verify
1676 let attrs = tcx.codegen_fn_attrs(id);
1677 if attrs.link_section.is_none() {
1681 // For the wasm32 target statics with `#[link_section]` are placed into custom
1682 // sections of the final output file, but this isn't link custom sections of
1683 // other executable formats. Namely we can only embed a list of bytes,
1684 // nothing with pointers to anything else or relocations. If any relocation
1685 // show up, reject them here.
1686 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1687 // the consumer's responsibility to ensure all bytes that have been read
1688 // have defined values.
1689 let instance = ty::Instance::mono(tcx, id);
1690 let cid = GlobalId {
1694 let param_env = ty::ParamEnv::reveal_all();
1695 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1696 let alloc = if let ConstValue::ByRef { alloc, .. } = static_.val {
1699 bug!("Matching on non-ByRef static")
1701 if alloc.relocations().len() != 0 {
1702 let msg = "statics with a custom `#[link_section]` must be a \
1703 simple list of bytes on the wasm target with no \
1704 extra levels of indirection such as references";
1705 tcx.sess.span_err(span, msg);
1710 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item) {
1711 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1712 // an error would be reported if this fails.
1713 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1716 fn report_forbidden_specialization(
1718 impl_item: &hir::ImplItem,
1721 let mut err = struct_span_err!(
1722 tcx.sess, impl_item.span, E0520,
1723 "`{}` specializes an item from a parent `impl`, but \
1724 that item is not marked `default`",
1726 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1729 match tcx.span_of_impl(parent_impl) {
1731 err.span_label(span, "parent `impl` is here");
1732 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1736 err.note(&format!("parent implementation is in crate `{}`", cname));
1743 fn check_specialization_validity<'tcx>(
1745 trait_def: &ty::TraitDef,
1746 trait_item: &ty::AssocItem,
1748 impl_item: &hir::ImplItem,
1750 let kind = match impl_item.kind {
1751 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1752 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1753 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1754 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1757 let mut ancestor_impls = trait_def.ancestors(tcx, impl_id)
1759 .filter_map(|parent| {
1760 if parent.is_from_trait() {
1763 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
1768 if ancestor_impls.peek().is_none() {
1769 // No parent, nothing to specialize.
1773 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
1775 // Parent impl exists, and contains the parent item we're trying to specialize, but
1776 // doesn't mark it `default`.
1777 Some(parent_item) if tcx.impl_item_is_final(&parent_item) => {
1778 Some(Err(parent_impl.def_id()))
1781 // Parent impl contains item and makes it specializable.
1786 // Parent impl doesn't mention the item. This means it's inherited from the
1787 // grandparent. In that case, if parent is a `default impl`, inherited items use the
1788 // "defaultness" from the grandparent, else they are final.
1789 None => if tcx.impl_is_default(parent_impl.def_id()) {
1792 Some(Err(parent_impl.def_id()))
1797 // If `opt_result` is `None`, we have only encoutered `default impl`s that don't contain the
1798 // item. This is allowed, the item isn't actually getting specialized here.
1799 let result = opt_result.unwrap_or(Ok(()));
1801 if let Err(parent_impl) = result {
1802 report_forbidden_specialization(tcx, impl_item, parent_impl);
1806 fn check_impl_items_against_trait<'tcx>(
1810 impl_trait_ref: ty::TraitRef<'tcx>,
1811 impl_item_refs: &[hir::ImplItemRef],
1813 let impl_span = tcx.sess.source_map().def_span(impl_span);
1815 // If the trait reference itself is erroneous (so the compilation is going
1816 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1817 // isn't populated for such impls.
1818 if impl_trait_ref.references_error() { return; }
1820 // Locate trait definition and items
1821 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1822 let mut overridden_associated_type = None;
1824 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1826 // Check existing impl methods to see if they are both present in trait
1827 // and compatible with trait signature
1828 for impl_item in impl_items() {
1829 let ty_impl_item = tcx.associated_item(
1830 tcx.hir().local_def_id(impl_item.hir_id));
1831 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1832 .find(|ac| Namespace::from(&impl_item.kind) == Namespace::from(ac.kind) &&
1833 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1835 // Not compatible, but needed for the error message
1836 tcx.associated_items(impl_trait_ref.def_id)
1837 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1840 // Check that impl definition matches trait definition
1841 if let Some(ty_trait_item) = ty_trait_item {
1842 match impl_item.kind {
1843 hir::ImplItemKind::Const(..) => {
1844 // Find associated const definition.
1845 if ty_trait_item.kind == ty::AssocKind::Const {
1846 compare_const_impl(tcx,
1852 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1853 "item `{}` is an associated const, \
1854 which doesn't match its trait `{}`",
1857 err.span_label(impl_item.span, "does not match trait");
1858 // We can only get the spans from local trait definition
1859 // Same for E0324 and E0325
1860 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1861 err.span_label(trait_span, "item in trait");
1866 hir::ImplItemKind::Method(..) => {
1867 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1868 if ty_trait_item.kind == ty::AssocKind::Method {
1869 compare_impl_method(tcx,
1876 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1877 "item `{}` is an associated method, \
1878 which doesn't match its trait `{}`",
1881 err.span_label(impl_item.span, "does not match trait");
1882 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1883 err.span_label(trait_span, "item in trait");
1888 hir::ImplItemKind::OpaqueTy(..) |
1889 hir::ImplItemKind::TyAlias(_) => {
1890 if ty_trait_item.kind == ty::AssocKind::Type {
1891 if ty_trait_item.defaultness.has_value() {
1892 overridden_associated_type = Some(impl_item);
1895 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1896 "item `{}` is an associated type, \
1897 which doesn't match its trait `{}`",
1900 err.span_label(impl_item.span, "does not match trait");
1901 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1902 err.span_label(trait_span, "item in trait");
1909 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1913 // Check for missing items from trait
1914 let mut missing_items = Vec::new();
1915 let mut invalidated_items = Vec::new();
1916 let associated_type_overridden = overridden_associated_type.is_some();
1917 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1918 let is_implemented = trait_def.ancestors(tcx, impl_id)
1919 .leaf_def(tcx, trait_item.ident, trait_item.kind)
1920 .map(|node_item| !node_item.node.is_from_trait())
1923 if !is_implemented && !tcx.impl_is_default(impl_id) {
1924 if !trait_item.defaultness.has_value() {
1925 missing_items.push(trait_item);
1926 } else if associated_type_overridden {
1927 invalidated_items.push(trait_item.ident);
1932 if !missing_items.is_empty() {
1933 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1934 "not all trait items implemented, missing: `{}`",
1935 missing_items.iter()
1936 .map(|trait_item| trait_item.ident.to_string())
1937 .collect::<Vec<_>>().join("`, `"));
1938 err.span_label(impl_span, format!("missing `{}` in implementation",
1939 missing_items.iter()
1940 .map(|trait_item| trait_item.ident.to_string())
1941 .collect::<Vec<_>>().join("`, `")));
1942 for trait_item in missing_items {
1943 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1944 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1946 err.note_trait_signature(trait_item.ident.to_string(),
1947 trait_item.signature(tcx));
1953 if !invalidated_items.is_empty() {
1954 let invalidator = overridden_associated_type.unwrap();
1955 span_err!(tcx.sess, invalidator.span, E0399,
1956 "the following trait items need to be reimplemented \
1957 as `{}` was overridden: `{}`",
1959 invalidated_items.iter()
1960 .map(|name| name.to_string())
1961 .collect::<Vec<_>>().join("`, `"))
1965 /// Checks whether a type can be represented in memory. In particular, it
1966 /// identifies types that contain themselves without indirection through a
1967 /// pointer, which would mean their size is unbounded.
1968 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
1969 let rty = tcx.type_of(item_def_id);
1971 // Check that it is possible to represent this type. This call identifies
1972 // (1) types that contain themselves and (2) types that contain a different
1973 // recursive type. It is only necessary to throw an error on those that
1974 // contain themselves. For case 2, there must be an inner type that will be
1975 // caught by case 1.
1976 match rty.is_representable(tcx, sp) {
1977 Representability::SelfRecursive(spans) => {
1978 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1980 err.span_label(span, "recursive without indirection");
1985 Representability::Representable | Representability::ContainsRecursive => (),
1990 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1991 let t = tcx.type_of(def_id);
1992 if let ty::Adt(def, substs) = t.kind {
1993 if def.is_struct() {
1994 let fields = &def.non_enum_variant().fields;
1995 if fields.is_empty() {
1996 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1999 let e = fields[0].ty(tcx, substs);
2000 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
2001 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
2002 .span_label(sp, "SIMD elements must have the same type")
2007 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
2008 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
2010 span_err!(tcx.sess, sp, E0077,
2011 "SIMD vector element type should be machine type");
2019 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2020 let repr = tcx.adt_def(def_id).repr;
2022 for attr in tcx.get_attrs(def_id).iter() {
2023 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
2024 if let attr::ReprPacked(pack) = r {
2025 if let Some(repr_pack) = repr.pack {
2026 if pack as u64 != repr_pack.bytes() {
2028 tcx.sess, sp, E0634,
2029 "type has conflicting packed representation hints"
2036 if repr.align.is_some() {
2037 struct_span_err!(tcx.sess, sp, E0587,
2038 "type has conflicting packed and align representation hints").emit();
2040 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
2041 struct_span_err!(tcx.sess, sp, E0588,
2042 "packed type cannot transitively contain a `[repr(align)]` type").emit();
2047 fn check_packed_inner(tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec<DefId>) -> bool {
2048 let t = tcx.type_of(def_id);
2049 if stack.contains(&def_id) {
2050 debug!("check_packed_inner: {:?} is recursive", t);
2053 if let ty::Adt(def, substs) = t.kind {
2054 if def.is_struct() || def.is_union() {
2055 if tcx.adt_def(def.did).repr.align.is_some() {
2058 // push struct def_id before checking fields
2060 for field in &def.non_enum_variant().fields {
2061 let f = field.ty(tcx, substs);
2062 if let ty::Adt(def, _) = f.kind {
2063 if check_packed_inner(tcx, def.did, stack) {
2068 // only need to pop if not early out
2075 /// Emit an error when encountering more or less than one variant in a transparent enum.
2076 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2077 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
2078 tcx.hir().span_if_local(variant.def_id).unwrap()
2081 "needs exactly one variant, but has {}",
2084 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2085 err.span_label(sp, &msg);
2086 if let &[ref start @ .., ref end] = &variant_spans[..] {
2087 for variant_span in start {
2088 err.span_label(*variant_span, "");
2090 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2095 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2097 fn bad_non_zero_sized_fields<'tcx>(
2099 adt: &'tcx ty::AdtDef,
2101 field_spans: impl Iterator<Item = Span>,
2104 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2105 let mut err = struct_span_err!(
2109 "{}transparent {} {}",
2110 if adt.is_enum() { "the variant of a " } else { "" },
2114 err.span_label(sp, &msg);
2115 for sp in field_spans {
2116 err.span_label(sp, "this field is non-zero-sized");
2121 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2122 let adt = tcx.adt_def(def_id);
2123 if !adt.repr.transparent() {
2126 let sp = tcx.sess.source_map().def_span(sp);
2129 if !tcx.features().transparent_enums {
2131 &tcx.sess.parse_sess,
2132 sym::transparent_enums,
2134 GateIssue::Language,
2135 "transparent enums are unstable",
2138 if adt.variants.len() != 1 {
2139 bad_variant_count(tcx, adt, sp, def_id);
2140 if adt.variants.is_empty() {
2141 // Don't bother checking the fields. No variants (and thus no fields) exist.
2147 if adt.is_union() && !tcx.features().transparent_unions {
2148 emit_feature_err(&tcx.sess.parse_sess,
2149 sym::transparent_unions,
2151 GateIssue::Language,
2152 "transparent unions are unstable");
2155 // For each field, figure out if it's known to be a ZST and align(1)
2156 let field_infos = adt.all_fields().map(|field| {
2157 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2158 let param_env = tcx.param_env(field.did);
2159 let layout = tcx.layout_of(param_env.and(ty));
2160 // We are currently checking the type this field came from, so it must be local
2161 let span = tcx.hir().span_if_local(field.did).unwrap();
2162 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2163 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2167 let non_zst_fields = field_infos.clone().filter_map(|(span, zst, _align1)| if !zst {
2172 let non_zst_count = non_zst_fields.clone().count();
2173 if non_zst_count != 1 {
2174 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2176 for (span, zst, align1) in field_infos {
2182 "zero-sized field in transparent {} has alignment larger than 1",
2184 ).span_label(span, "has alignment larger than 1").emit();
2189 #[allow(trivial_numeric_casts)]
2190 pub fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, vs: &'tcx [hir::Variant], id: hir::HirId) {
2191 let def_id = tcx.hir().local_def_id(id);
2192 let def = tcx.adt_def(def_id);
2193 def.destructor(tcx); // force the destructor to be evaluated
2196 let attributes = tcx.get_attrs(def_id);
2197 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2199 tcx.sess, attr.span, E0084,
2200 "unsupported representation for zero-variant enum")
2201 .span_label(sp, "zero-variant enum")
2206 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2207 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2208 if !tcx.features().repr128 {
2209 emit_feature_err(&tcx.sess.parse_sess,
2212 GateIssue::Language,
2213 "repr with 128-bit type is unstable");
2218 if let Some(ref e) = v.disr_expr {
2219 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2223 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2225 |var: &hir::Variant| match var.data {
2226 hir::VariantData::Unit(..) => true,
2230 let has_disr = |var: &hir::Variant| var.disr_expr.is_some();
2231 let has_non_units = vs.iter().any(|var| !is_unit(var));
2232 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2233 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2235 if disr_non_unit || (disr_units && has_non_units) {
2236 let mut err = struct_span_err!(tcx.sess, sp, E0732,
2237 "`#[repr(inttype)]` must be specified");
2242 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2243 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2244 // Check for duplicate discriminant values
2245 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2246 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2247 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2248 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2249 let i_span = match variant_i.disr_expr {
2250 Some(ref expr) => tcx.hir().span(expr.hir_id),
2251 None => tcx.hir().span(variant_i_hir_id)
2253 let span = match v.disr_expr {
2254 Some(ref expr) => tcx.hir().span(expr.hir_id),
2257 struct_span_err!(tcx.sess, span, E0081,
2258 "discriminant value `{}` already exists", disr_vals[i])
2259 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2260 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
2263 disr_vals.push(discr);
2266 check_representable(tcx, sp, def_id);
2267 check_transparent(tcx, sp, def_id);
2270 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span, qpath: &QPath) {
2271 span_err!(tcx.sess, span, E0533,
2272 "expected unit struct, unit variant or constant, found {} `{}`",
2274 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
2277 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2278 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2282 fn item_def_id(&self) -> Option<DefId> {
2286 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2288 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2289 let item_id = tcx.hir().ty_param_owner(hir_id);
2290 let item_def_id = tcx.hir().local_def_id(item_id);
2291 let generics = tcx.generics_of(item_def_id);
2292 let index = generics.param_def_id_to_index[&def_id];
2293 ty::GenericPredicates {
2295 predicates: tcx.arena.alloc_from_iter(
2296 self.param_env.caller_bounds.iter().filter_map(|&predicate| match predicate {
2297 ty::Predicate::Trait(ref data)
2298 if data.skip_binder().self_ty().is_param(index) => {
2299 // HACK(eddyb) should get the original `Span`.
2300 let span = tcx.def_span(def_id);
2301 Some((predicate, span))
2311 def: Option<&ty::GenericParamDef>,
2313 ) -> Option<ty::Region<'tcx>> {
2315 Some(def) => infer::EarlyBoundRegion(span, def.name),
2316 None => infer::MiscVariable(span)
2318 Some(self.next_region_var(v))
2321 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2322 if let Some(param) = param {
2323 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2328 self.next_ty_var(TypeVariableOrigin {
2329 kind: TypeVariableOriginKind::TypeInference,
2338 param: Option<&ty::GenericParamDef>,
2340 ) -> &'tcx Const<'tcx> {
2341 if let Some(param) = param {
2342 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2347 self.next_const_var(ty, ConstVariableOrigin {
2348 kind: ConstVariableOriginKind::ConstInference,
2354 fn projected_ty_from_poly_trait_ref(&self,
2357 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2360 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2362 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2366 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2369 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2370 if ty.has_escaping_bound_vars() {
2371 ty // FIXME: normalization and escaping regions
2373 self.normalize_associated_types_in(span, &ty)
2377 fn set_tainted_by_errors(&self) {
2378 self.infcx.set_tainted_by_errors()
2381 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2382 self.write_ty(hir_id, ty)
2386 /// Controls whether the arguments are tupled. This is used for the call
2389 /// Tupling means that all call-side arguments are packed into a tuple and
2390 /// passed as a single parameter. For example, if tupling is enabled, this
2393 /// fn f(x: (isize, isize))
2395 /// Can be called as:
2402 #[derive(Clone, Eq, PartialEq)]
2403 enum TupleArgumentsFlag {
2408 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2410 inh: &'a Inherited<'a, 'tcx>,
2411 param_env: ty::ParamEnv<'tcx>,
2412 body_id: hir::HirId,
2413 ) -> FnCtxt<'a, 'tcx> {
2417 err_count_on_creation: inh.tcx.sess.err_count(),
2419 ret_coercion_span: RefCell::new(None),
2421 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2422 hir::CRATE_HIR_ID)),
2423 diverges: Cell::new(Diverges::Maybe),
2424 has_errors: Cell::new(false),
2425 enclosing_breakables: RefCell::new(EnclosingBreakables {
2427 by_id: Default::default(),
2433 pub fn sess(&self) -> &Session {
2437 pub fn errors_reported_since_creation(&self) -> bool {
2438 self.tcx.sess.err_count() > self.err_count_on_creation
2441 /// Produces warning on the given node, if the current point in the
2442 /// function is unreachable, and there hasn't been another warning.
2443 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2444 // FIXME: Combine these two 'if' expressions into one once
2445 // let chains are implemented
2446 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2447 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2448 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2449 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2450 if !span.is_desugaring(DesugaringKind::CondTemporary) &&
2451 !span.is_desugaring(DesugaringKind::Async) &&
2452 !orig_span.is_desugaring(DesugaringKind::Await)
2454 self.diverges.set(Diverges::WarnedAlways);
2456 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2458 let msg = format!("unreachable {}", kind);
2459 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2460 .span_label(span, &msg)
2463 custom_note.unwrap_or("any code following this expression is unreachable"),
2472 code: ObligationCauseCode<'tcx>)
2473 -> ObligationCause<'tcx> {
2474 ObligationCause::new(span, self.body_id, code)
2477 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2478 self.cause(span, ObligationCauseCode::MiscObligation)
2481 /// Resolves type and const variables in `ty` if possible. Unlike the infcx
2482 /// version (resolve_vars_if_possible), this version will
2483 /// also select obligations if it seems useful, in an effort
2484 /// to get more type information.
2485 fn resolve_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2486 debug!("resolve_vars_with_obligations(ty={:?})", ty);
2488 // No Infer()? Nothing needs doing.
2489 if !ty.has_infer_types() && !ty.has_infer_consts() {
2490 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2494 // If `ty` is a type variable, see whether we already know what it is.
2495 ty = self.resolve_vars_if_possible(&ty);
2496 if !ty.has_infer_types() && !ty.has_infer_consts() {
2497 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2501 // If not, try resolving pending obligations as much as
2502 // possible. This can help substantially when there are
2503 // indirect dependencies that don't seem worth tracking
2505 self.select_obligations_where_possible(false, |_| {});
2506 ty = self.resolve_vars_if_possible(&ty);
2508 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2512 fn record_deferred_call_resolution(
2514 closure_def_id: DefId,
2515 r: DeferredCallResolution<'tcx>,
2517 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2518 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2521 fn remove_deferred_call_resolutions(
2523 closure_def_id: DefId,
2524 ) -> Vec<DeferredCallResolution<'tcx>> {
2525 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2526 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2529 pub fn tag(&self) -> String {
2530 format!("{:p}", self)
2533 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2534 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2535 span_bug!(span, "no type for local variable {}",
2536 self.tcx.hir().node_to_string(nid))
2541 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2542 debug!("write_ty({:?}, {:?}) in fcx {}",
2543 id, self.resolve_vars_if_possible(&ty), self.tag());
2544 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2546 if ty.references_error() {
2547 self.has_errors.set(true);
2548 self.set_tainted_by_errors();
2552 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2553 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2556 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2557 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2560 pub fn write_method_call(&self,
2562 method: MethodCallee<'tcx>) {
2563 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2564 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2565 self.write_substs(hir_id, method.substs);
2567 // When the method is confirmed, the `method.substs` includes
2568 // parameters from not just the method, but also the impl of
2569 // the method -- in particular, the `Self` type will be fully
2570 // resolved. However, those are not something that the "user
2571 // specified" -- i.e., those types come from the inferred type
2572 // of the receiver, not something the user wrote. So when we
2573 // create the user-substs, we want to replace those earlier
2574 // types with just the types that the user actually wrote --
2575 // that is, those that appear on the *method itself*.
2577 // As an example, if the user wrote something like
2578 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2579 // type of `foo` (possibly adjusted), but we don't want to
2580 // include that. We want just the `[_, u32]` part.
2581 if !method.substs.is_noop() {
2582 let method_generics = self.tcx.generics_of(method.def_id);
2583 if !method_generics.params.is_empty() {
2584 let user_type_annotation = self.infcx.probe(|_| {
2585 let user_substs = UserSubsts {
2586 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2587 let i = param.index as usize;
2588 if i < method_generics.parent_count {
2589 self.infcx.var_for_def(DUMMY_SP, param)
2594 user_self_ty: None, // not relevant here
2597 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2603 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2604 self.write_user_type_annotation(hir_id, user_type_annotation);
2609 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2610 if !substs.is_noop() {
2611 debug!("write_substs({:?}, {:?}) in fcx {}",
2616 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2620 /// Given the substs that we just converted from the HIR, try to
2621 /// canonicalize them and store them as user-given substitutions
2622 /// (i.e., substitutions that must be respected by the NLL check).
2624 /// This should be invoked **before any unifications have
2625 /// occurred**, so that annotations like `Vec<_>` are preserved
2627 pub fn write_user_type_annotation_from_substs(
2631 substs: SubstsRef<'tcx>,
2632 user_self_ty: Option<UserSelfTy<'tcx>>,
2635 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2636 user_self_ty={:?} in fcx {}",
2637 hir_id, def_id, substs, user_self_ty, self.tag(),
2640 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2641 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2642 &UserType::TypeOf(def_id, UserSubsts {
2647 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2648 self.write_user_type_annotation(hir_id, canonicalized);
2652 pub fn write_user_type_annotation(
2655 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2658 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2659 hir_id, canonical_user_type_annotation, self.tag(),
2662 if !canonical_user_type_annotation.is_identity() {
2663 self.tables.borrow_mut().user_provided_types_mut().insert(
2664 hir_id, canonical_user_type_annotation
2667 debug!("write_user_type_annotation: skipping identity substs");
2671 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2672 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2678 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2679 Entry::Vacant(entry) => { entry.insert(adj); },
2680 Entry::Occupied(mut entry) => {
2681 debug!(" - composing on top of {:?}", entry.get());
2682 match (&entry.get()[..], &adj[..]) {
2683 // Applying any adjustment on top of a NeverToAny
2684 // is a valid NeverToAny adjustment, because it can't
2686 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2688 Adjustment { kind: Adjust::Deref(_), .. },
2689 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2691 Adjustment { kind: Adjust::Deref(_), .. },
2692 .. // Any following adjustments are allowed.
2694 // A reborrow has no effect before a dereference.
2696 // FIXME: currently we never try to compose autoderefs
2697 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2699 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2700 expr, entry.get(), adj)
2702 *entry.get_mut() = adj;
2707 /// Basically whenever we are converting from a type scheme into
2708 /// the fn body space, we always want to normalize associated
2709 /// types as well. This function combines the two.
2710 fn instantiate_type_scheme<T>(&self,
2712 substs: SubstsRef<'tcx>,
2715 where T : TypeFoldable<'tcx>
2717 let value = value.subst(self.tcx, substs);
2718 let result = self.normalize_associated_types_in(span, &value);
2719 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2726 /// As `instantiate_type_scheme`, but for the bounds found in a
2727 /// generic type scheme.
2728 fn instantiate_bounds(
2732 substs: SubstsRef<'tcx>,
2733 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
2734 let bounds = self.tcx.predicates_of(def_id);
2735 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
2736 let result = bounds.instantiate(self.tcx, substs);
2737 let result = self.normalize_associated_types_in(span, &result);
2739 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
2748 /// Replaces the opaque types from the given value with type variables,
2749 /// and records the `OpaqueTypeMap` for later use during writeback. See
2750 /// `InferCtxt::instantiate_opaque_types` for more details.
2751 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2753 parent_id: hir::HirId,
2757 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2758 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2762 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2763 self.instantiate_opaque_types(
2772 let mut opaque_types = self.opaque_types.borrow_mut();
2773 for (ty, decl) in opaque_type_map {
2774 let _ = opaque_types.insert(ty, decl);
2780 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2781 where T : TypeFoldable<'tcx>
2783 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2786 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2788 where T : TypeFoldable<'tcx>
2790 self.inh.partially_normalize_associated_types_in(span,
2796 pub fn require_type_meets(&self,
2799 code: traits::ObligationCauseCode<'tcx>,
2802 self.register_bound(
2805 traits::ObligationCause::new(span, self.body_id, code));
2808 pub fn require_type_is_sized(
2812 code: traits::ObligationCauseCode<'tcx>,
2814 if !ty.references_error() {
2815 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2816 self.require_type_meets(ty, span, code, lang_item);
2820 pub fn require_type_is_sized_deferred(
2824 code: traits::ObligationCauseCode<'tcx>,
2826 if !ty.references_error() {
2827 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2831 pub fn register_bound(
2835 cause: traits::ObligationCause<'tcx>,
2837 if !ty.references_error() {
2838 self.fulfillment_cx.borrow_mut()
2839 .register_bound(self, self.param_env, ty, def_id, cause);
2843 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2844 let t = AstConv::ast_ty_to_ty(self, ast_t);
2845 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2849 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2850 let ty = self.to_ty(ast_ty);
2851 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2853 if Self::can_contain_user_lifetime_bounds(ty) {
2854 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2855 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2856 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2862 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2863 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2864 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2867 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2868 AstConv::ast_const_to_const(self, ast_c, ty)
2871 // If the type given by the user has free regions, save it for later, since
2872 // NLL would like to enforce those. Also pass in types that involve
2873 // projections, since those can resolve to `'static` bounds (modulo #54940,
2874 // which hopefully will be fixed by the time you see this comment, dear
2875 // reader, although I have my doubts). Also pass in types with inference
2876 // types, because they may be repeated. Other sorts of things are already
2877 // sufficiently enforced with erased regions. =)
2878 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2880 T: TypeFoldable<'tcx>
2882 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2885 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2886 match self.tables.borrow().node_types().get(id) {
2888 None if self.is_tainted_by_errors() => self.tcx.types.err,
2890 bug!("no type for node {}: {} in fcx {}",
2891 id, self.tcx.hir().node_to_string(id),
2897 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2898 /// outlive the region `r`.
2899 pub fn register_wf_obligation(
2903 code: traits::ObligationCauseCode<'tcx>,
2905 // WF obligations never themselves fail, so no real need to give a detailed cause:
2906 let cause = traits::ObligationCause::new(span, self.body_id, code);
2907 self.register_predicate(
2908 traits::Obligation::new(cause, self.param_env, ty::Predicate::WellFormed(ty)),
2912 /// Registers obligations that all types appearing in `substs` are well-formed.
2913 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2914 for ty in substs.types() {
2915 if !ty.references_error() {
2916 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2921 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2922 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2923 /// trait/region obligations.
2925 /// For example, if there is a function:
2928 /// fn foo<'a,T:'a>(...)
2931 /// and a reference:
2937 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2938 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2939 pub fn add_obligations_for_parameters(&self,
2940 cause: traits::ObligationCause<'tcx>,
2941 predicates: &ty::InstantiatedPredicates<'tcx>)
2943 assert!(!predicates.has_escaping_bound_vars());
2945 debug!("add_obligations_for_parameters(predicates={:?})",
2948 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2949 self.register_predicate(obligation);
2953 // FIXME(arielb1): use this instead of field.ty everywhere
2954 // Only for fields! Returns <none> for methods>
2955 // Indifferent to privacy flags
2959 field: &'tcx ty::FieldDef,
2960 substs: SubstsRef<'tcx>,
2962 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2965 fn check_casts(&self) {
2966 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2967 for cast in deferred_cast_checks.drain(..) {
2972 fn resolve_generator_interiors(&self, def_id: DefId) {
2973 let mut generators = self.deferred_generator_interiors.borrow_mut();
2974 for (body_id, interior, kind) in generators.drain(..) {
2975 self.select_obligations_where_possible(false, |_| {});
2976 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2980 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2981 // Non-numerics get replaced with ! or () (depending on whether
2982 // feature(never_type) is enabled, unconstrained ints with i32,
2983 // unconstrained floats with f64.
2984 // Fallback becomes very dubious if we have encountered type-checking errors.
2985 // In that case, fallback to Error.
2986 // The return value indicates whether fallback has occurred.
2987 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2988 use rustc::ty::error::UnconstrainedNumeric::Neither;
2989 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2991 assert!(ty.is_ty_infer());
2992 let fallback = match self.type_is_unconstrained_numeric(ty) {
2993 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2994 UnconstrainedInt => self.tcx.types.i32,
2995 UnconstrainedFloat => self.tcx.types.f64,
2996 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2997 Neither => return false,
2999 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
3000 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
3004 fn select_all_obligations_or_error(&self) {
3005 debug!("select_all_obligations_or_error");
3006 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
3007 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
3011 /// Select as many obligations as we can at present.
3012 fn select_obligations_where_possible(
3014 fallback_has_occurred: bool,
3015 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
3017 if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
3018 mutate_fullfillment_errors(&mut errors);
3019 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
3023 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
3024 /// returns a type of `&T`, but the actual type we assign to the
3025 /// *expression* is `T`. So this function just peels off the return
3026 /// type by one layer to yield `T`.
3027 fn make_overloaded_place_return_type(&self,
3028 method: MethodCallee<'tcx>)
3029 -> ty::TypeAndMut<'tcx>
3031 // extract method return type, which will be &T;
3032 let ret_ty = method.sig.output();
3034 // method returns &T, but the type as visible to user is T, so deref
3035 ret_ty.builtin_deref(true).unwrap()
3041 base_expr: &'tcx hir::Expr,
3045 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3046 // FIXME(#18741) -- this is almost but not quite the same as the
3047 // autoderef that normal method probing does. They could likely be
3050 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3051 let mut result = None;
3052 while result.is_none() && autoderef.next().is_some() {
3053 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3055 autoderef.finalize(self);
3059 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3060 /// (and otherwise adjust) `base_expr`, looking for a type which either
3061 /// supports builtin indexing or overloaded indexing.
3062 /// This loop implements one step in that search; the autoderef loop
3063 /// is implemented by `lookup_indexing`.
3067 base_expr: &hir::Expr,
3068 autoderef: &Autoderef<'a, 'tcx>,
3071 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3072 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3073 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3080 for &unsize in &[false, true] {
3081 let mut self_ty = adjusted_ty;
3083 // We only unsize arrays here.
3084 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3085 self_ty = self.tcx.mk_slice(element_ty);
3091 // If some lookup succeeds, write callee into table and extract index/element
3092 // type from the method signature.
3093 // If some lookup succeeded, install method in table
3094 let input_ty = self.next_ty_var(TypeVariableOrigin {
3095 kind: TypeVariableOriginKind::AutoDeref,
3096 span: base_expr.span,
3098 let method = self.try_overloaded_place_op(
3099 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
3101 let result = method.map(|ok| {
3102 debug!("try_index_step: success, using overloaded indexing");
3103 let method = self.register_infer_ok_obligations(ok);
3105 let mut adjustments = autoderef.adjust_steps(self, needs);
3106 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3107 let mutbl = match r_mutbl {
3108 hir::MutImmutable => AutoBorrowMutability::Immutable,
3109 hir::MutMutable => AutoBorrowMutability::Mutable {
3110 // Indexing can be desugared to a method call,
3111 // so maybe we could use two-phase here.
3112 // See the documentation of AllowTwoPhase for why that's
3113 // not the case today.
3114 allow_two_phase_borrow: AllowTwoPhase::No,
3117 adjustments.push(Adjustment {
3118 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3119 target: self.tcx.mk_ref(region, ty::TypeAndMut {
3126 adjustments.push(Adjustment {
3127 kind: Adjust::Pointer(PointerCast::Unsize),
3128 target: method.sig.inputs()[0]
3131 self.apply_adjustments(base_expr, adjustments);
3133 self.write_method_call(expr.hir_id, method);
3134 (input_ty, self.make_overloaded_place_return_type(method).ty)
3136 if result.is_some() {
3144 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3145 let (tr, name) = match (op, is_mut) {
3146 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3147 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3148 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3149 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3151 (tr, ast::Ident::with_dummy_span(name))
3154 fn try_overloaded_place_op(&self,
3157 arg_tys: &[Ty<'tcx>],
3160 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3162 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3168 // Try Mut first, if needed.
3169 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3170 let method = match (needs, mut_tr) {
3171 (Needs::MutPlace, Some(trait_did)) => {
3172 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3177 // Otherwise, fall back to the immutable version.
3178 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3179 let method = match (method, imm_tr) {
3180 (None, Some(trait_did)) => {
3181 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3183 (method, _) => method,
3189 fn check_method_argument_types(
3192 expr: &'tcx hir::Expr,
3193 method: Result<MethodCallee<'tcx>, ()>,
3194 args_no_rcvr: &'tcx [hir::Expr],
3195 tuple_arguments: TupleArgumentsFlag,
3196 expected: Expectation<'tcx>,
3199 let has_error = match method {
3201 method.substs.references_error() || method.sig.references_error()
3206 let err_inputs = self.err_args(args_no_rcvr.len());
3208 let err_inputs = match tuple_arguments {
3209 DontTupleArguments => err_inputs,
3210 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3213 self.check_argument_types(
3223 return self.tcx.types.err;
3226 let method = method.unwrap();
3227 // HACK(eddyb) ignore self in the definition (see above).
3228 let expected_arg_tys = self.expected_inputs_for_expected_output(
3231 method.sig.output(),
3232 &method.sig.inputs()[1..]
3234 self.check_argument_types(
3237 &method.sig.inputs()[1..],
3238 &expected_arg_tys[..],
3240 method.sig.c_variadic,
3242 self.tcx.hir().span_if_local(method.def_id),
3247 fn self_type_matches_expected_vid(
3249 trait_ref: ty::PolyTraitRef<'tcx>,
3250 expected_vid: ty::TyVid,
3252 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3254 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3255 trait_ref, self_ty, expected_vid
3257 match self_ty.kind {
3258 ty::Infer(ty::TyVar(found_vid)) => {
3259 // FIXME: consider using `sub_root_var` here so we
3260 // can see through subtyping.
3261 let found_vid = self.root_var(found_vid);
3262 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3263 expected_vid == found_vid
3269 fn obligations_for_self_ty<'b>(
3272 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3275 // FIXME: consider using `sub_root_var` here so we
3276 // can see through subtyping.
3277 let ty_var_root = self.root_var(self_ty);
3278 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3279 self_ty, ty_var_root,
3280 self.fulfillment_cx.borrow().pending_obligations());
3284 .pending_obligations()
3286 .filter_map(move |obligation| match obligation.predicate {
3287 ty::Predicate::Projection(ref data) =>
3288 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3289 ty::Predicate::Trait(ref data) =>
3290 Some((data.to_poly_trait_ref(), obligation)),
3291 ty::Predicate::Subtype(..) => None,
3292 ty::Predicate::RegionOutlives(..) => None,
3293 ty::Predicate::TypeOutlives(..) => None,
3294 ty::Predicate::WellFormed(..) => None,
3295 ty::Predicate::ObjectSafe(..) => None,
3296 ty::Predicate::ConstEvaluatable(..) => None,
3297 // N.B., this predicate is created by breaking down a
3298 // `ClosureType: FnFoo()` predicate, where
3299 // `ClosureType` represents some `Closure`. It can't
3300 // possibly be referring to the current closure,
3301 // because we haven't produced the `Closure` for
3302 // this closure yet; this is exactly why the other
3303 // code is looking for a self type of a unresolved
3304 // inference variable.
3305 ty::Predicate::ClosureKind(..) => None,
3306 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3309 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3310 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3311 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3315 /// Generic function that factors out common logic from function calls,
3316 /// method calls and overloaded operators.
3317 fn check_argument_types(
3320 expr: &'tcx hir::Expr,
3321 fn_inputs: &[Ty<'tcx>],
3322 expected_arg_tys: &[Ty<'tcx>],
3323 args: &'tcx [hir::Expr],
3325 tuple_arguments: TupleArgumentsFlag,
3326 def_span: Option<Span>,
3329 // Grab the argument types, supplying fresh type variables
3330 // if the wrong number of arguments were supplied
3331 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3337 // All the input types from the fn signature must outlive the call
3338 // so as to validate implied bounds.
3339 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3340 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3343 let expected_arg_count = fn_inputs.len();
3345 let param_count_error = |expected_count: usize,
3350 let mut err = tcx.sess.struct_span_err_with_code(sp,
3351 &format!("this function takes {}{} but {} {} supplied",
3352 if c_variadic { "at least " } else { "" },
3353 potentially_plural_count(expected_count, "parameter"),
3354 potentially_plural_count(arg_count, "parameter"),
3355 if arg_count == 1 {"was"} else {"were"}),
3356 DiagnosticId::Error(error_code.to_owned()));
3358 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3359 err.span_label(def_s, "defined here");
3362 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3363 // remove closing `)` from the span
3364 let sugg_span = sugg_span.shrink_to_lo();
3365 err.span_suggestion(
3367 "expected the unit value `()`; create it with empty parentheses",
3369 Applicability::MachineApplicable);
3371 err.span_label(sp, format!("expected {}{}",
3372 if c_variadic { "at least " } else { "" },
3373 potentially_plural_count(expected_count, "parameter")));
3378 let mut expected_arg_tys = expected_arg_tys.to_vec();
3380 let formal_tys = if tuple_arguments == TupleArguments {
3381 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3382 match tuple_type.kind {
3383 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3384 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3385 expected_arg_tys = vec![];
3386 self.err_args(args.len())
3388 ty::Tuple(arg_types) => {
3389 expected_arg_tys = match expected_arg_tys.get(0) {
3390 Some(&ty) => match ty.kind {
3391 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3396 arg_types.iter().map(|k| k.expect_ty()).collect()
3399 span_err!(tcx.sess, sp, E0059,
3400 "cannot use call notation; the first type parameter \
3401 for the function trait is neither a tuple nor unit");
3402 expected_arg_tys = vec![];
3403 self.err_args(args.len())
3406 } else if expected_arg_count == supplied_arg_count {
3408 } else if c_variadic {
3409 if supplied_arg_count >= expected_arg_count {
3412 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3413 expected_arg_tys = vec![];
3414 self.err_args(supplied_arg_count)
3417 // is the missing argument of type `()`?
3418 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3419 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3420 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3421 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3425 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3427 expected_arg_tys = vec![];
3428 self.err_args(supplied_arg_count)
3431 debug!("check_argument_types: formal_tys={:?}",
3432 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3434 // If there is no expectation, expect formal_tys.
3435 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3441 let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
3443 // Check the arguments.
3444 // We do this in a pretty awful way: first we type-check any arguments
3445 // that are not closures, then we type-check the closures. This is so
3446 // that we have more information about the types of arguments when we
3447 // type-check the functions. This isn't really the right way to do this.
3448 for &check_closures in &[false, true] {
3449 debug!("check_closures={}", check_closures);
3451 // More awful hacks: before we check argument types, try to do
3452 // an "opportunistic" vtable resolution of any trait bounds on
3453 // the call. This helps coercions.
3455 self.select_obligations_where_possible(false, |errors| {
3456 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
3457 self.point_at_arg_instead_of_call_if_possible(
3459 &final_arg_types[..],
3466 // For C-variadic functions, we don't have a declared type for all of
3467 // the arguments hence we only do our usual type checking with
3468 // the arguments who's types we do know.
3469 let t = if c_variadic {
3471 } else if tuple_arguments == TupleArguments {
3476 for (i, arg) in args.iter().take(t).enumerate() {
3477 // Warn only for the first loop (the "no closures" one).
3478 // Closure arguments themselves can't be diverging, but
3479 // a previous argument can, e.g., `foo(panic!(), || {})`.
3480 if !check_closures {
3481 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3484 let is_closure = match arg.kind {
3485 ExprKind::Closure(..) => true,
3489 if is_closure != check_closures {
3493 debug!("checking the argument");
3494 let formal_ty = formal_tys[i];
3496 // The special-cased logic below has three functions:
3497 // 1. Provide as good of an expected type as possible.
3498 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3500 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3502 // 2. Coerce to the most detailed type that could be coerced
3503 // to, which is `expected_ty` if `rvalue_hint` returns an
3504 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3505 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3506 // We're processing function arguments so we definitely want to use
3507 // two-phase borrows.
3508 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3509 final_arg_types.push((i, coerce_ty));
3511 // 3. Relate the expected type and the formal one,
3512 // if the expected type was used for the coercion.
3513 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3517 // We also need to make sure we at least write the ty of the other
3518 // arguments which we skipped above.
3520 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3521 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3522 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3525 for arg in args.iter().skip(expected_arg_count) {
3526 let arg_ty = self.check_expr(&arg);
3528 // There are a few types which get autopromoted when passed via varargs
3529 // in C but we just error out instead and require explicit casts.
3530 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3532 ty::Float(ast::FloatTy::F32) => {
3533 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3535 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3536 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3538 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3539 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3542 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3543 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3544 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3552 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3553 vec![self.tcx.types.err; len]
3556 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
3557 /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
3558 /// reference a type argument. If they do, and there's only *one* argument that does, we point
3559 /// at the corresponding argument's expression span instead of the `fn` call path span.
3560 fn point_at_arg_instead_of_call_if_possible(
3562 errors: &mut Vec<traits::FulfillmentError<'_>>,
3563 final_arg_types: &[(usize, Ty<'tcx>)],
3565 args: &'tcx [hir::Expr],
3567 if !call_sp.desugaring_kind().is_some() {
3568 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3569 // the `?` operator.
3570 for error in errors {
3571 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3572 // Collect the argument position for all arguments that could have caused this
3573 // `FullfillmentError`.
3574 let mut referenced_in = final_arg_types.iter()
3575 .flat_map(|(i, ty)| {
3576 let ty = self.resolve_vars_if_possible(ty);
3577 // We walk the argument type because the argument's type could have
3578 // been `Option<T>`, but the `FullfillmentError` references `T`.
3580 .filter(|&ty| ty == predicate.skip_binder().self_ty())
3583 if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
3584 // We make sure that only *one* argument matches the obligation failure
3585 // and thet the obligation's span to its expression's.
3586 error.obligation.cause.span = args[ref_in].span;
3587 error.points_at_arg_span = true;
3594 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call expression, we walk the
3595 /// `PathSegment`s and resolve their type parameters to see if any of the `FullfillmentError`s
3596 /// were caused by them. If they were, we point at the corresponding type argument's span
3597 /// instead of the `fn` call path span.
3598 fn point_at_type_arg_instead_of_call_if_possible(
3600 errors: &mut Vec<traits::FulfillmentError<'_>>,
3601 call_expr: &'tcx hir::Expr,
3603 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
3604 if let hir::ExprKind::Path(qpath) = &path.kind {
3605 if let hir::QPath::Resolved(_, path) = &qpath {
3606 for error in errors {
3607 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3608 // If any of the type arguments in this path segment caused the
3609 // `FullfillmentError`, point at its span (#61860).
3610 for arg in path.segments.iter()
3611 .filter_map(|seg| seg.args.as_ref())
3612 .flat_map(|a| a.args.iter())
3614 if let hir::GenericArg::Type(hir_ty) = &arg {
3615 if let hir::TyKind::Path(
3616 hir::QPath::TypeRelative(..),
3618 // Avoid ICE with associated types. As this is best
3619 // effort only, it's ok to ignore the case. It
3620 // would trigger in `is_send::<T::AssocType>();`
3621 // from `typeck-default-trait-impl-assoc-type.rs`.
3623 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
3624 let ty = self.resolve_vars_if_possible(&ty);
3625 if ty == predicate.skip_binder().self_ty() {
3626 error.obligation.cause.span = hir_ty.span;
3638 // AST fragment checking
3641 expected: Expectation<'tcx>)
3647 ast::LitKind::Str(..) => tcx.mk_static_str(),
3648 ast::LitKind::ByteStr(ref v) => {
3649 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3650 tcx.mk_array(tcx.types.u8, v.len() as u64))
3652 ast::LitKind::Byte(_) => tcx.types.u8,
3653 ast::LitKind::Char(_) => tcx.types.char,
3654 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3655 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3656 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3657 let opt_ty = expected.to_option(self).and_then(|ty| {
3659 ty::Int(_) | ty::Uint(_) => Some(ty),
3660 ty::Char => Some(tcx.types.u8),
3661 ty::RawPtr(..) => Some(tcx.types.usize),
3662 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3666 opt_ty.unwrap_or_else(|| self.next_int_var())
3668 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3669 ast::LitKind::FloatUnsuffixed(_) => {
3670 let opt_ty = expected.to_option(self).and_then(|ty| {
3672 ty::Float(_) => Some(ty),
3676 opt_ty.unwrap_or_else(|| self.next_float_var())
3678 ast::LitKind::Bool(_) => tcx.types.bool,
3679 ast::LitKind::Err(_) => tcx.types.err,
3683 // Determine the `Self` type, using fresh variables for all variables
3684 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3685 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3687 pub fn impl_self_ty(&self,
3688 span: Span, // (potential) receiver for this impl
3690 -> TypeAndSubsts<'tcx> {
3691 let ity = self.tcx.type_of(did);
3692 debug!("impl_self_ty: ity={:?}", ity);
3694 let substs = self.fresh_substs_for_item(span, did);
3695 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3697 TypeAndSubsts { substs: substs, ty: substd_ty }
3700 /// Unifies the output type with the expected type early, for more coercions
3701 /// and forward type information on the input expressions.
3702 fn expected_inputs_for_expected_output(&self,
3704 expected_ret: Expectation<'tcx>,
3705 formal_ret: Ty<'tcx>,
3706 formal_args: &[Ty<'tcx>])
3708 let formal_ret = self.resolve_vars_with_obligations(formal_ret);
3709 let ret_ty = match expected_ret.only_has_type(self) {
3711 None => return Vec::new()
3713 let expect_args = self.fudge_inference_if_ok(|| {
3714 // Attempt to apply a subtyping relationship between the formal
3715 // return type (likely containing type variables if the function
3716 // is polymorphic) and the expected return type.
3717 // No argument expectations are produced if unification fails.
3718 let origin = self.misc(call_span);
3719 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3721 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3722 // to identity so the resulting type is not constrained.
3725 // Process any obligations locally as much as
3726 // we can. We don't care if some things turn
3727 // out unconstrained or ambiguous, as we're
3728 // just trying to get hints here.
3729 self.save_and_restore_in_snapshot_flag(|_| {
3730 let mut fulfill = TraitEngine::new(self.tcx);
3731 for obligation in ok.obligations {
3732 fulfill.register_predicate_obligation(self, obligation);
3734 fulfill.select_where_possible(self)
3735 }).map_err(|_| ())?;
3737 Err(_) => return Err(()),
3740 // Record all the argument types, with the substitutions
3741 // produced from the above subtyping unification.
3742 Ok(formal_args.iter().map(|ty| {
3743 self.resolve_vars_if_possible(ty)
3745 }).unwrap_or_default();
3746 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3747 formal_args, formal_ret,
3748 expect_args, expected_ret);
3752 pub fn check_struct_path(&self,
3755 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3756 let path_span = match *qpath {
3757 QPath::Resolved(_, ref path) => path.span,
3758 QPath::TypeRelative(ref qself, _) => qself.span
3760 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3761 let variant = match def {
3763 self.set_tainted_by_errors();
3766 Res::Def(DefKind::Variant, _) => {
3768 ty::Adt(adt, substs) => {
3769 Some((adt.variant_of_res(def), adt.did, substs))
3771 _ => bug!("unexpected type: {:?}", ty)
3774 Res::Def(DefKind::Struct, _)
3775 | Res::Def(DefKind::Union, _)
3776 | Res::Def(DefKind::TyAlias, _)
3777 | Res::Def(DefKind::AssocTy, _)
3778 | Res::SelfTy(..) => {
3780 ty::Adt(adt, substs) if !adt.is_enum() => {
3781 Some((adt.non_enum_variant(), adt.did, substs))
3786 _ => bug!("unexpected definition: {:?}", def)
3789 if let Some((variant, did, substs)) = variant {
3790 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3791 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3793 // Check bounds on type arguments used in the path.
3794 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
3795 let cause = traits::ObligationCause::new(
3798 traits::ItemObligation(did),
3800 self.add_obligations_for_parameters(cause, &bounds);
3804 struct_span_err!(self.tcx.sess, path_span, E0071,
3805 "expected struct, variant or union type, found {}",
3806 ty.sort_string(self.tcx))
3807 .span_label(path_span, "not a struct")
3813 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3814 // The newly resolved definition is written into `type_dependent_defs`.
3815 fn finish_resolving_struct_path(&self,
3822 QPath::Resolved(ref maybe_qself, ref path) => {
3823 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3824 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3827 QPath::TypeRelative(ref qself, ref segment) => {
3828 let ty = self.to_ty(qself);
3830 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
3835 let result = AstConv::associated_path_to_ty(
3844 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3845 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3847 // Write back the new resolution.
3848 self.write_resolution(hir_id, result);
3850 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3855 /// Resolves an associated value path into a base type and associated constant, or method
3856 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3857 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3861 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3863 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3864 let (ty, qself, item_segment) = match *qpath {
3865 QPath::Resolved(ref opt_qself, ref path) => {
3867 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3868 &path.segments[..]);
3870 QPath::TypeRelative(ref qself, ref segment) => {
3871 (self.to_ty(qself), qself, segment)
3874 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3875 // Return directly on cache hit. This is useful to avoid doubly reporting
3876 // errors with default match binding modes. See #44614.
3877 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3878 .unwrap_or(Res::Err);
3879 return (def, Some(ty), slice::from_ref(&**item_segment));
3881 let item_name = item_segment.ident;
3882 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3883 let result = match error {
3884 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3885 _ => Err(ErrorReported),
3887 if item_name.name != kw::Invalid {
3888 self.report_method_error(
3892 SelfSource::QPath(qself),
3895 ).map(|mut e| e.emit());
3900 // Write back the new resolution.
3901 self.write_resolution(hir_id, result);
3903 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3905 slice::from_ref(&**item_segment),
3909 pub fn check_decl_initializer(
3911 local: &'tcx hir::Local,
3912 init: &'tcx hir::Expr,
3914 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3915 // for #42640 (default match binding modes).
3918 let ref_bindings = local.pat.contains_explicit_ref_binding();
3920 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3921 if let Some(m) = ref_bindings {
3922 // Somewhat subtle: if we have a `ref` binding in the pattern,
3923 // we want to avoid introducing coercions for the RHS. This is
3924 // both because it helps preserve sanity and, in the case of
3925 // ref mut, for soundness (issue #23116). In particular, in
3926 // the latter case, we need to be clear that the type of the
3927 // referent for the reference that results is *equal to* the
3928 // type of the place it is referencing, and not some
3929 // supertype thereof.
3930 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3931 self.demand_eqtype(init.span, local_ty, init_ty);
3934 self.check_expr_coercable_to_type(init, local_ty)
3938 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3939 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3940 self.write_ty(local.hir_id, t);
3942 if let Some(ref init) = local.init {
3943 let init_ty = self.check_decl_initializer(local, &init);
3944 self.overwrite_local_ty_if_err(local, t, init_ty);
3947 self.check_pat_top(&local.pat, t, None);
3948 let pat_ty = self.node_ty(local.pat.hir_id);
3949 self.overwrite_local_ty_if_err(local, t, pat_ty);
3952 fn overwrite_local_ty_if_err(&self, local: &'tcx hir::Local, decl_ty: Ty<'tcx>, ty: Ty<'tcx>) {
3953 if ty.references_error() {
3954 // Override the types everywhere with `types.err` to avoid knock down errors.
3955 self.write_ty(local.hir_id, ty);
3956 self.write_ty(local.pat.hir_id, ty);
3957 let local_ty = LocalTy {
3961 self.locals.borrow_mut().insert(local.hir_id, local_ty);
3962 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
3966 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
3967 err.span_suggestion_short(
3968 span.shrink_to_hi(),
3969 "consider using a semicolon here",
3971 Applicability::MachineApplicable,
3975 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3976 // Don't do all the complex logic below for `DeclItem`.
3978 hir::StmtKind::Item(..) => return,
3979 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3982 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3984 // Hide the outer diverging and `has_errors` flags.
3985 let old_diverges = self.diverges.get();
3986 let old_has_errors = self.has_errors.get();
3987 self.diverges.set(Diverges::Maybe);
3988 self.has_errors.set(false);
3991 hir::StmtKind::Local(ref l) => {
3992 self.check_decl_local(&l);
3995 hir::StmtKind::Item(_) => {}
3996 hir::StmtKind::Expr(ref expr) => {
3997 // Check with expected type of `()`.
3999 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
4000 self.suggest_semicolon_at_end(expr.span, err);
4003 hir::StmtKind::Semi(ref expr) => {
4004 self.check_expr(&expr);
4008 // Combine the diverging and `has_error` flags.
4009 self.diverges.set(self.diverges.get() | old_diverges);
4010 self.has_errors.set(self.has_errors.get() | old_has_errors);
4013 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
4014 let unit = self.tcx.mk_unit();
4015 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4017 // if the block produces a `!` value, that can always be
4018 // (effectively) coerced to unit.
4020 self.demand_suptype(blk.span, unit, ty);
4024 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
4025 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
4026 /// when given code like the following:
4028 /// if false { return 0i32; } else { 1u32 }
4029 /// // ^^^^ point at this instead of the whole `if` expression
4031 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
4032 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
4033 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
4034 self.in_progress_tables
4035 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
4036 .and_then(|arm_ty| {
4037 if arm_ty.is_never() {
4040 Some(match &arm.body.kind {
4041 // Point at the tail expression when possible.
4042 hir::ExprKind::Block(block, _) => block.expr
4045 .unwrap_or(block.span),
4051 if arm_spans.len() == 1 {
4052 return arm_spans[0];
4058 fn check_block_with_expected(
4060 blk: &'tcx hir::Block,
4061 expected: Expectation<'tcx>,
4064 let mut fcx_ps = self.ps.borrow_mut();
4065 let unsafety_state = fcx_ps.recurse(blk);
4066 replace(&mut *fcx_ps, unsafety_state)
4069 // In some cases, blocks have just one exit, but other blocks
4070 // can be targeted by multiple breaks. This can happen both
4071 // with labeled blocks as well as when we desugar
4072 // a `try { ... }` expression.
4076 // 'a: { if true { break 'a Err(()); } Ok(()) }
4078 // Here we would wind up with two coercions, one from
4079 // `Err(())` and the other from the tail expression
4080 // `Ok(())`. If the tail expression is omitted, that's a
4081 // "forced unit" -- unless the block diverges, in which
4082 // case we can ignore the tail expression (e.g., `'a: {
4083 // break 'a 22; }` would not force the type of the block
4085 let tail_expr = blk.expr.as_ref();
4086 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4087 let coerce = if blk.targeted_by_break {
4088 CoerceMany::new(coerce_to_ty)
4090 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4091 Some(e) => slice::from_ref(e),
4094 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4097 let prev_diverges = self.diverges.get();
4098 let ctxt = BreakableCtxt {
4099 coerce: Some(coerce),
4103 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4104 for s in &blk.stmts {
4108 // check the tail expression **without** holding the
4109 // `enclosing_breakables` lock below.
4110 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4112 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4113 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4114 let coerce = ctxt.coerce.as_mut().unwrap();
4115 if let Some(tail_expr_ty) = tail_expr_ty {
4116 let tail_expr = tail_expr.unwrap();
4117 let span = self.get_expr_coercion_span(tail_expr);
4118 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4119 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4121 // Subtle: if there is no explicit tail expression,
4122 // that is typically equivalent to a tail expression
4123 // of `()` -- except if the block diverges. In that
4124 // case, there is no value supplied from the tail
4125 // expression (assuming there are no other breaks,
4126 // this implies that the type of the block will be
4129 // #41425 -- label the implicit `()` as being the
4130 // "found type" here, rather than the "expected type".
4131 if !self.diverges.get().is_always() {
4132 // #50009 -- Do not point at the entire fn block span, point at the return type
4133 // span, as it is the cause of the requirement, and
4134 // `consider_hint_about_removing_semicolon` will point at the last expression
4135 // if it were a relevant part of the error. This improves usability in editors
4136 // that highlight errors inline.
4137 let mut sp = blk.span;
4138 let mut fn_span = None;
4139 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4140 let ret_sp = decl.output.span();
4141 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4142 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4143 // output would otherwise be incorrect and even misleading. Make sure
4144 // the span we're aiming at correspond to a `fn` body.
4145 if block_sp == blk.span {
4147 fn_span = Some(ident.span);
4151 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4152 if let Some(expected_ty) = expected.only_has_type(self) {
4153 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4155 if let Some(fn_span) = fn_span {
4158 "implicitly returns `()` as its body has no tail or `return` \
4168 // If we can break from the block, then the block's exit is always reachable
4169 // (... as long as the entry is reachable) - regardless of the tail of the block.
4170 self.diverges.set(prev_diverges);
4173 let mut ty = ctxt.coerce.unwrap().complete(self);
4175 if self.has_errors.get() || ty.references_error() {
4176 ty = self.tcx.types.err
4179 self.write_ty(blk.hir_id, ty);
4181 *self.ps.borrow_mut() = prev;
4185 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4186 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4188 Node::Item(&hir::Item {
4189 kind: hir::ItemKind::Fn(_, _, _, body_id), ..
4191 Node::ImplItem(&hir::ImplItem {
4192 kind: hir::ImplItemKind::Method(_, body_id), ..
4194 let body = self.tcx.hir().body(body_id);
4195 if let ExprKind::Block(block, _) = &body.value.kind {
4196 return Some(block.span);
4204 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4205 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
4206 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4207 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4210 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4211 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
4213 Node::Item(&hir::Item {
4214 ident, kind: hir::ItemKind::Fn(ref decl, ..), ..
4216 // This is less than ideal, it will not suggest a return type span on any
4217 // method called `main`, regardless of whether it is actually the entry point,
4218 // but it will still present it as the reason for the expected type.
4219 Some((decl, ident, ident.name != sym::main))
4221 Node::TraitItem(&hir::TraitItem {
4222 ident, kind: hir::TraitItemKind::Method(hir::MethodSig {
4225 }) => Some((decl, ident, true)),
4226 Node::ImplItem(&hir::ImplItem {
4227 ident, kind: hir::ImplItemKind::Method(hir::MethodSig {
4230 }) => Some((decl, ident, false)),
4235 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4236 /// suggestion can be made, `None` otherwise.
4237 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
4238 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4239 // `while` before reaching it, as block tail returns are not available in them.
4240 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4241 let parent = self.tcx.hir().get(blk_id);
4242 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4246 /// On implicit return expressions with mismatched types, provides the following suggestions:
4248 /// - Points out the method's return type as the reason for the expected type.
4249 /// - Possible missing semicolon.
4250 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4251 pub fn suggest_mismatched_types_on_tail(
4253 err: &mut DiagnosticBuilder<'tcx>,
4254 expr: &'tcx hir::Expr,
4260 let expr = expr.peel_drop_temps();
4261 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4262 let mut pointing_at_return_type = false;
4263 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4264 pointing_at_return_type = self.suggest_missing_return_type(
4265 err, &fn_decl, expected, found, can_suggest);
4267 self.suggest_ref_or_into(err, expr, expected, found);
4268 self.suggest_boxing_when_appropriate(err, expr, expected, found);
4269 pointing_at_return_type
4272 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4273 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4275 /// fn foo(x: usize) -> usize { x }
4276 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4280 err: &mut DiagnosticBuilder<'tcx>,
4285 let hir = self.tcx.hir();
4286 let (def_id, sig) = match found.kind {
4287 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4288 ty::Closure(def_id, substs) => {
4289 // We don't use `closure_sig` to account for malformed closures like
4290 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4291 let closure_sig_ty = substs.as_closure().sig_ty(def_id, self.tcx);
4292 (def_id, match closure_sig_ty.kind {
4293 ty::FnPtr(sig) => sig,
4301 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4303 let sig = self.normalize_associated_types_in(expr.span, &sig);
4304 if self.can_coerce(sig.output(), expected) {
4305 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4306 (String::new(), Applicability::MachineApplicable)
4308 ("...".to_string(), Applicability::HasPlaceholders)
4310 let mut msg = "call this function";
4311 match hir.get_if_local(def_id) {
4312 Some(Node::Item(hir::Item {
4313 kind: ItemKind::Fn(.., body_id),
4316 Some(Node::ImplItem(hir::ImplItem {
4317 kind: hir::ImplItemKind::Method(_, body_id),
4320 Some(Node::TraitItem(hir::TraitItem {
4321 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4324 let body = hir.body(*body_id);
4325 sugg_call = body.params.iter()
4326 .map(|param| match ¶m.pat.kind {
4327 hir::PatKind::Binding(_, _, ident, None)
4328 if ident.name != kw::SelfLower => ident.to_string(),
4329 _ => "_".to_string(),
4330 }).collect::<Vec<_>>().join(", ");
4332 Some(Node::Expr(hir::Expr {
4333 kind: ExprKind::Closure(_, _, body_id, closure_span, _),
4334 span: full_closure_span,
4337 if *full_closure_span == expr.span {
4340 err.span_label(*closure_span, "closure defined here");
4341 msg = "call this closure";
4342 let body = hir.body(*body_id);
4343 sugg_call = body.params.iter()
4344 .map(|param| match ¶m.pat.kind {
4345 hir::PatKind::Binding(_, _, ident, None)
4346 if ident.name != kw::SelfLower => ident.to_string(),
4347 _ => "_".to_string(),
4348 }).collect::<Vec<_>>().join(", ");
4350 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4351 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4352 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4353 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4354 msg = "instantiate this tuple variant";
4356 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4357 msg = "instantiate this tuple struct";
4362 Some(Node::ForeignItem(hir::ForeignItem {
4363 kind: hir::ForeignItemKind::Fn(_, idents, _),
4366 Some(Node::TraitItem(hir::TraitItem {
4367 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4369 })) => sugg_call = idents.iter()
4370 .map(|ident| if ident.name != kw::SelfLower {
4374 }).collect::<Vec<_>>()
4378 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4379 err.span_suggestion(
4381 &format!("use parentheses to {}", msg),
4382 format!("{}({})", code, sugg_call),
4391 pub fn suggest_ref_or_into(
4393 err: &mut DiagnosticBuilder<'tcx>,
4398 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4399 err.span_suggestion(
4403 Applicability::MachineApplicable,
4405 } else if let (ty::FnDef(def_id, ..), true) = (
4407 self.suggest_fn_call(err, expr, expected, found),
4409 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4410 let sp = self.sess().source_map().def_span(sp);
4411 err.span_label(sp, &format!("{} defined here", found));
4413 } else if !self.check_for_cast(err, expr, found, expected) {
4414 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4418 let methods = self.get_conversion_methods(expr.span, expected, found);
4419 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4420 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4421 .filter_map(|(receiver, method)| {
4422 let method_call = format!(".{}()", method.ident);
4423 if receiver.ends_with(&method_call) {
4424 None // do not suggest code that is already there (#53348)
4426 let method_call_list = [".to_vec()", ".to_string()"];
4427 let sugg = if receiver.ends_with(".clone()")
4428 && method_call_list.contains(&method_call.as_str()) {
4429 let max_len = receiver.rfind(".").unwrap();
4430 format!("{}{}", &receiver[..max_len], method_call)
4432 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
4433 format!("({}){}", receiver, method_call)
4435 format!("{}{}", receiver, method_call)
4438 Some(if is_struct_pat_shorthand_field {
4439 format!("{}: {}", receiver, sugg)
4445 if suggestions.peek().is_some() {
4446 err.span_suggestions(
4448 "try using a conversion method",
4450 Applicability::MaybeIncorrect,
4457 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4458 /// in the heap by calling `Box::new()`.
4459 fn suggest_boxing_when_appropriate(
4461 err: &mut DiagnosticBuilder<'tcx>,
4466 if self.tcx.hir().is_const_context(expr.hir_id) {
4467 // Do not suggest `Box::new` in const context.
4470 if !expected.is_box() || found.is_box() {
4473 let boxed_found = self.tcx.mk_box(found);
4474 if let (true, Ok(snippet)) = (
4475 self.can_coerce(boxed_found, expected),
4476 self.sess().source_map().span_to_snippet(expr.span),
4478 err.span_suggestion(
4480 "store this in the heap by calling `Box::new`",
4481 format!("Box::new({})", snippet),
4482 Applicability::MachineApplicable,
4484 err.note("for more on the distinction between the stack and the \
4485 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4486 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4487 https://doc.rust-lang.org/std/boxed/index.html");
4492 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4496 /// bar_that_returns_u32()
4500 /// This routine checks if the return expression in a block would make sense on its own as a
4501 /// statement and the return type has been left as default or has been specified as `()`. If so,
4502 /// it suggests adding a semicolon.
4503 fn suggest_missing_semicolon(
4505 err: &mut DiagnosticBuilder<'tcx>,
4506 expression: &'tcx hir::Expr,
4510 if expected.is_unit() {
4511 // `BlockTailExpression` only relevant if the tail expr would be
4512 // useful on its own.
4513 match expression.kind {
4514 ExprKind::Call(..) |
4515 ExprKind::MethodCall(..) |
4516 ExprKind::Loop(..) |
4517 ExprKind::Match(..) |
4518 ExprKind::Block(..) => {
4519 let sp = self.tcx.sess.source_map().next_point(cause_span);
4520 err.span_suggestion(
4522 "try adding a semicolon",
4524 Applicability::MachineApplicable);
4531 /// A possible error is to forget to add a return type that is needed:
4535 /// bar_that_returns_u32()
4539 /// This routine checks if the return type is left as default, the method is not part of an
4540 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4542 fn suggest_missing_return_type(
4544 err: &mut DiagnosticBuilder<'tcx>,
4545 fn_decl: &hir::FnDecl,
4550 // Only suggest changing the return type for methods that
4551 // haven't set a return type at all (and aren't `fn main()` or an impl).
4552 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4553 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4554 err.span_suggestion(
4556 "try adding a return type",
4557 format!("-> {} ", self.resolve_vars_with_obligations(found)),
4558 Applicability::MachineApplicable);
4561 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4562 err.span_label(span, "possibly return type missing here?");
4565 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4566 // `fn main()` must return `()`, do not suggest changing return type
4567 err.span_label(span, "expected `()` because of default return type");
4570 // expectation was caused by something else, not the default return
4571 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4572 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4573 // Only point to return type if the expected type is the return type, as if they
4574 // are not, the expectation must have been caused by something else.
4575 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
4577 let ty = AstConv::ast_ty_to_ty(self, ty);
4578 debug!("suggest_missing_return_type: return type {:?}", ty);
4579 debug!("suggest_missing_return_type: expected type {:?}", ty);
4580 if ty.kind == expected.kind {
4581 err.span_label(sp, format!("expected `{}` because of return type",
4590 /// A possible error is to forget to add `.await` when using futures:
4593 /// async fn make_u32() -> u32 {
4597 /// fn take_u32(x: u32) {}
4599 /// async fn foo() {
4600 /// let x = make_u32();
4605 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4606 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4607 /// `.await` to the tail of the expression.
4608 fn suggest_missing_await(
4610 err: &mut DiagnosticBuilder<'tcx>,
4615 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4616 // body isn't `async`.
4617 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4618 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4619 let body = self.tcx().hir().body(body_id);
4620 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
4622 // Check for `Future` implementations by constructing a predicate to
4623 // prove: `<T as Future>::Output == U`
4624 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4625 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4626 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4627 // `<T as Future>::Output`
4628 projection_ty: ty::ProjectionTy {
4630 substs: self.tcx.mk_substs_trait(
4632 self.fresh_substs_for_item(sp, item_def_id)
4639 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4640 if self.infcx.predicate_may_hold(&obligation) {
4641 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4642 err.span_suggestion(
4644 "consider using `.await` here",
4645 format!("{}.await", code),
4646 Applicability::MaybeIncorrect,
4654 /// A common error is to add an extra semicolon:
4657 /// fn foo() -> usize {
4662 /// This routine checks if the final statement in a block is an
4663 /// expression with an explicit semicolon whose type is compatible
4664 /// with `expected_ty`. If so, it suggests removing the semicolon.
4665 fn consider_hint_about_removing_semicolon(
4667 blk: &'tcx hir::Block,
4668 expected_ty: Ty<'tcx>,
4669 err: &mut DiagnosticBuilder<'_>,
4671 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4672 err.span_suggestion(
4674 "consider removing this semicolon",
4676 Applicability::MachineApplicable,
4681 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4682 // Be helpful when the user wrote `{... expr;}` and
4683 // taking the `;` off is enough to fix the error.
4684 let last_stmt = blk.stmts.last()?;
4685 let last_expr = match last_stmt.kind {
4686 hir::StmtKind::Semi(ref e) => e,
4689 let last_expr_ty = self.node_ty(last_expr.hir_id);
4690 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4693 let original_span = original_sp(last_stmt.span, blk.span);
4694 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4697 // Instantiates the given path, which must refer to an item with the given
4698 // number of type parameters and type.
4699 pub fn instantiate_value_path(&self,
4700 segments: &[hir::PathSegment],
4701 self_ty: Option<Ty<'tcx>>,
4705 -> (Ty<'tcx>, Res) {
4707 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4716 let path_segs = match res {
4717 Res::Local(_) | Res::SelfCtor(_) => vec![],
4718 Res::Def(kind, def_id) =>
4719 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4720 _ => bug!("instantiate_value_path on {:?}", res),
4723 let mut user_self_ty = None;
4724 let mut is_alias_variant_ctor = false;
4726 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4727 if let Some(self_ty) = self_ty {
4728 let adt_def = self_ty.ty_adt_def().unwrap();
4729 user_self_ty = Some(UserSelfTy {
4730 impl_def_id: adt_def.did,
4733 is_alias_variant_ctor = true;
4736 Res::Def(DefKind::Method, def_id)
4737 | Res::Def(DefKind::AssocConst, def_id) => {
4738 let container = tcx.associated_item(def_id).container;
4739 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4741 ty::TraitContainer(trait_did) => {
4742 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4744 ty::ImplContainer(impl_def_id) => {
4745 if segments.len() == 1 {
4746 // `<T>::assoc` will end up here, and so
4747 // can `T::assoc`. It this came from an
4748 // inherent impl, we need to record the
4749 // `T` for posterity (see `UserSelfTy` for
4751 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4752 user_self_ty = Some(UserSelfTy {
4763 // Now that we have categorized what space the parameters for each
4764 // segment belong to, let's sort out the parameters that the user
4765 // provided (if any) into their appropriate spaces. We'll also report
4766 // errors if type parameters are provided in an inappropriate place.
4768 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4769 let generics_has_err = AstConv::prohibit_generics(
4770 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4771 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4778 if let Res::Local(hid) = res {
4779 let ty = self.local_ty(span, hid).decl_ty;
4780 let ty = self.normalize_associated_types_in(span, &ty);
4781 self.write_ty(hir_id, ty);
4785 if generics_has_err {
4786 // Don't try to infer type parameters when prohibited generic arguments were given.
4787 user_self_ty = None;
4790 // Now we have to compare the types that the user *actually*
4791 // provided against the types that were *expected*. If the user
4792 // did not provide any types, then we want to substitute inference
4793 // variables. If the user provided some types, we may still need
4794 // to add defaults. If the user provided *too many* types, that's
4797 let mut infer_args_for_err = FxHashSet::default();
4798 for &PathSeg(def_id, index) in &path_segs {
4799 let seg = &segments[index];
4800 let generics = tcx.generics_of(def_id);
4801 // Argument-position `impl Trait` is treated as a normal generic
4802 // parameter internally, but we don't allow users to specify the
4803 // parameter's value explicitly, so we have to do some error-
4805 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4810 false, // `is_method_call`
4812 if suppress_errors {
4813 infer_args_for_err.insert(index);
4814 self.set_tainted_by_errors(); // See issue #53251.
4818 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4819 tcx.generics_of(*def_id).has_self
4820 }).unwrap_or(false);
4822 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4823 let ty = self.impl_self_ty(span, impl_def_id).ty;
4824 let adt_def = ty.ty_adt_def();
4827 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4828 let variant = adt_def.non_enum_variant();
4829 let ctor_def_id = variant.ctor_def_id.unwrap();
4831 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4836 let mut err = tcx.sess.struct_span_err(span,
4837 "the `Self` constructor can only be used with tuple or unit structs");
4838 if let Some(adt_def) = adt_def {
4839 match adt_def.adt_kind() {
4841 err.help("did you mean to use one of the enum's variants?");
4845 err.span_suggestion(
4847 "use curly brackets",
4848 String::from("Self { /* fields */ }"),
4849 Applicability::HasPlaceholders,
4856 return (tcx.types.err, res)
4862 let def_id = res.def_id();
4864 // The things we are substituting into the type should not contain
4865 // escaping late-bound regions, and nor should the base type scheme.
4866 let ty = tcx.type_of(def_id);
4868 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4874 // Provide the generic args, and whether types should be inferred.
4876 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4879 // If we've encountered an `impl Trait`-related error, we're just
4880 // going to infer the arguments for better error messages.
4881 if !infer_args_for_err.contains(&index) {
4882 // Check whether the user has provided generic arguments.
4883 if let Some(ref data) = segments[index].args {
4884 return (Some(data), segments[index].infer_args);
4887 return (None, segments[index].infer_args);
4892 // Provide substitutions for parameters for which (valid) arguments have been provided.
4894 match (¶m.kind, arg) {
4895 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4896 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4898 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4899 self.to_ty(ty).into()
4901 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4902 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4904 _ => unreachable!(),
4907 // Provide substitutions for parameters for which arguments are inferred.
4908 |substs, param, infer_args| {
4910 GenericParamDefKind::Lifetime => {
4911 self.re_infer(Some(param), span).unwrap().into()
4913 GenericParamDefKind::Type { has_default, .. } => {
4914 if !infer_args && has_default {
4915 // If we have a default, then we it doesn't matter that we're not
4916 // inferring the type arguments: we provide the default where any
4918 let default = tcx.type_of(param.def_id);
4921 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4924 // If no type arguments were provided, we have to infer them.
4925 // This case also occurs as a result of some malformed input, e.g.
4926 // a lifetime argument being given instead of a type parameter.
4927 // Using inference instead of `Error` gives better error messages.
4928 self.var_for_def(span, param)
4931 GenericParamDefKind::Const => {
4932 // FIXME(const_generics:defaults)
4933 // No const parameters were provided, we have to infer them.
4934 self.var_for_def(span, param)
4939 assert!(!substs.has_escaping_bound_vars());
4940 assert!(!ty.has_escaping_bound_vars());
4942 // First, store the "user substs" for later.
4943 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4945 self.add_required_obligations(span, def_id, &substs);
4947 // Substitute the values for the type parameters into the type of
4948 // the referenced item.
4949 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4951 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4952 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4953 // is inherent, there is no `Self` parameter; instead, the impl needs
4954 // type parameters, which we can infer by unifying the provided `Self`
4955 // with the substituted impl type.
4956 // This also occurs for an enum variant on a type alias.
4957 let ty = tcx.type_of(impl_def_id);
4959 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4960 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4961 Ok(ok) => self.register_infer_ok_obligations(ok),
4963 self.tcx.sess.delay_span_bug(span, &format!(
4964 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4972 self.check_rustc_args_require_const(def_id, hir_id, span);
4974 debug!("instantiate_value_path: type of {:?} is {:?}",
4977 self.write_substs(hir_id, substs);
4979 (ty_substituted, res)
4982 /// Add all the obligations that are required, substituting and normalized appropriately.
4983 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
4984 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
4986 for (i, mut obligation) in traits::predicates_for_generics(
4987 traits::ObligationCause::new(
4990 traits::ItemObligation(def_id),
4994 ).into_iter().enumerate() {
4995 // This makes the error point at the bound, but we want to point at the argument
4996 if let Some(span) = spans.get(i) {
4997 obligation.cause.code = traits::BindingObligation(def_id, *span);
4999 self.register_predicate(obligation);
5003 fn check_rustc_args_require_const(&self,
5007 // We're only interested in functions tagged with
5008 // #[rustc_args_required_const], so ignore anything that's not.
5009 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5013 // If our calling expression is indeed the function itself, we're good!
5014 // If not, generate an error that this can only be called directly.
5015 if let Node::Expr(expr) = self.tcx.hir().get(
5016 self.tcx.hir().get_parent_node(hir_id))
5018 if let ExprKind::Call(ref callee, ..) = expr.kind {
5019 if callee.hir_id == hir_id {
5025 self.tcx.sess.span_err(span, "this function can only be invoked \
5026 directly, not through a function pointer");
5029 // Resolves `typ` by a single level if `typ` is a type variable.
5030 // If no resolution is possible, then an error is reported.
5031 // Numeric inference variables may be left unresolved.
5032 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5033 let ty = self.resolve_vars_with_obligations(ty);
5034 if !ty.is_ty_var() {
5037 if !self.is_tainted_by_errors() {
5038 self.need_type_info_err((**self).body_id, sp, ty)
5039 .note("type must be known at this point")
5042 self.demand_suptype(sp, self.tcx.types.err, ty);
5047 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5050 ctxt: BreakableCtxt<'tcx>,
5052 ) -> (BreakableCtxt<'tcx>, R) {
5055 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5056 index = enclosing_breakables.stack.len();
5057 enclosing_breakables.by_id.insert(id, index);
5058 enclosing_breakables.stack.push(ctxt);
5062 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5063 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5064 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5065 enclosing_breakables.stack.pop().expect("missing breakable context")
5070 /// Instantiate a QueryResponse in a probe context, without a
5071 /// good ObligationCause.
5072 fn probe_instantiate_query_response(
5075 original_values: &OriginalQueryValues<'tcx>,
5076 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5077 ) -> InferResult<'tcx, Ty<'tcx>>
5079 self.instantiate_query_response_and_region_obligations(
5080 &traits::ObligationCause::misc(span, self.body_id),
5086 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5087 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5088 let mut contained_in_place = false;
5090 while let hir::Node::Expr(parent_expr) =
5091 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5093 match &parent_expr.kind {
5094 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5095 if lhs.hir_id == expr_id {
5096 contained_in_place = true;
5102 expr_id = parent_expr.hir_id;
5109 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5110 let own_counts = generics.own_counts();
5112 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5118 if own_counts.types == 0 {
5122 // Make a vector of booleans initially `false`; set to `true` when used.
5123 let mut types_used = vec![false; own_counts.types];
5125 for leaf_ty in ty.walk() {
5126 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.kind {
5127 debug!("found use of ty param num {}", index);
5128 types_used[index as usize - own_counts.lifetimes] = true;
5129 } else if let ty::Error = leaf_ty.kind {
5130 // If there is already another error, do not emit
5131 // an error for not using a type parameter.
5132 assert!(tcx.sess.has_errors());
5137 let types = generics.params.iter().filter(|param| match param.kind {
5138 ty::GenericParamDefKind::Type { .. } => true,
5141 for (&used, param) in types_used.iter().zip(types) {
5143 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5144 let span = tcx.hir().span(id);
5145 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5146 .span_label(span, "unused type parameter")
5152 fn fatally_break_rust(sess: &Session) {
5153 let handler = sess.diagnostic();
5154 handler.span_bug_no_panic(
5156 "It looks like you're trying to break rust; would you like some ICE?",
5158 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5159 handler.note_without_error(
5160 "we would appreciate a joke overview: \
5161 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5163 handler.note_without_error(&format!("rustc {} running on {}",
5164 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5165 crate::session::config::host_triple(),
5169 fn potentially_plural_count(count: usize, word: &str) -> String {
5170 format!("{} {}{}", count, word, pluralise!(count))