1 // ignore-tidy-filelength
7 Within the check phase of type check, we check each item one at a time
8 (bodies of function expressions are checked as part of the containing
9 function). Inference is used to supply types wherever they are unknown.
11 By far the most complex case is checking the body of a function. This
12 can be broken down into several distinct phases:
14 - gather: creates type variables to represent the type of each local
15 variable and pattern binding.
17 - main: the main pass does the lion's share of the work: it
18 determines the types of all expressions, resolves
19 methods, checks for most invalid conditions, and so forth. In
20 some cases, where a type is unknown, it may create a type or region
21 variable and use that as the type of an expression.
23 In the process of checking, various constraints will be placed on
24 these type variables through the subtyping relationships requested
25 through the `demand` module. The `infer` module is in charge
26 of resolving those constraints.
28 - regionck: after main is complete, the regionck pass goes over all
29 types looking for regions and making sure that they did not escape
30 into places they are not in scope. This may also influence the
31 final assignments of the various region variables if there is some
34 - vtable: find and records the impls to use for each trait bound that
35 appears on a type parameter.
37 - writeback: writes the final types within a function body, replacing
38 type variables with their final inferred types. These final types
39 are written into the `tcx.node_types` table, which should *never* contain
40 any reference to a type variable.
44 While type checking a function, the intermediate types for the
45 expressions, blocks, and so forth contained within the function are
46 stored in `fcx.node_types` and `fcx.node_substs`. These types
47 may contain unresolved type variables. After type checking is
48 complete, the functions in the writeback module are used to take the
49 types from this table, resolve them, and then write them into their
50 permanent home in the type context `tcx`.
52 This means that during inferencing you should use `fcx.write_ty()`
53 and `fcx.expr_ty()` / `fcx.node_ty()` to write/obtain the types of
54 nodes within the function.
56 The types of top-level items, which never contain unbound type
57 variables, are stored directly into the `tcx` tables.
59 N.B., a type variable is not the same thing as a type parameter. A
60 type variable is rather an "instance" of a type parameter: that is,
61 given a generic function `fn foo<T>(t: T)`: while checking the
62 function `foo`, the type `ty_param(0)` refers to the type `T`, which
63 is treated in abstract. When `foo()` is called, however, `T` will be
64 substituted for a fresh type variable `N`. This variable will
65 eventually be resolved to some concrete type (which might itself be
86 mod generator_interior;
90 use crate::astconv::{AstConv, PathSeg};
91 use errors::{Applicability, DiagnosticBuilder, DiagnosticId, pluralise};
92 use rustc::hir::{self, ExprKind, GenericArg, ItemKind, Node, PatKind, QPath};
93 use rustc::hir::def::{CtorOf, Res, DefKind};
94 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
95 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
96 use rustc::hir::itemlikevisit::ItemLikeVisitor;
97 use rustc::hir::ptr::P;
98 use crate::middle::lang_items;
99 use crate::namespace::Namespace;
100 use rustc::infer::{self, InferCtxt, InferOk, InferResult};
101 use rustc::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
102 use rustc_index::vec::Idx;
103 use rustc_target::spec::abi::Abi;
104 use rustc::infer::opaque_types::OpaqueTypeDecl;
105 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
106 use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
107 use rustc::middle::region;
108 use rustc::mir::interpret::{ConstValue, GlobalId};
109 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
111 self, AdtKind, CanonicalUserType, Ty, TyCtxt, Const, GenericParamDefKind,
112 ToPolyTraitRef, ToPredicate, RegionKind, UserType
114 use rustc::ty::adjustment::{
115 Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast
117 use rustc::ty::fold::TypeFoldable;
118 use rustc::ty::query::Providers;
119 use rustc::ty::subst::{
120 GenericArgKind, Subst, InternalSubsts, SubstsRef, UserSelfTy, UserSubsts,
122 use rustc::ty::util::{Representability, IntTypeExt, Discr};
123 use rustc::ty::layout::VariantIdx;
124 use syntax_pos::{self, BytePos, Span, MultiSpan};
125 use syntax_pos::hygiene::DesugaringKind;
128 use syntax::feature_gate::{GateIssue, emit_feature_err};
129 use syntax::source_map::{DUMMY_SP, original_sp};
130 use syntax::symbol::{kw, sym};
131 use syntax::util::parser::ExprPrecedence;
133 use std::cell::{Cell, RefCell, Ref, RefMut};
134 use std::collections::hash_map::Entry;
137 use std::mem::replace;
138 use std::ops::{self, Deref};
141 use crate::require_c_abi_if_c_variadic;
142 use crate::session::Session;
143 use crate::session::config::EntryFnType;
144 use crate::TypeAndSubsts;
146 use crate::util::captures::Captures;
147 use crate::util::common::{ErrorReported, indenter};
148 use crate::util::nodemap::{DefIdMap, DefIdSet, FxHashSet, HirIdMap};
150 pub use self::Expectation::*;
151 use self::autoderef::Autoderef;
152 use self::callee::DeferredCallResolution;
153 use self::coercion::{CoerceMany, DynamicCoerceMany};
154 pub use self::compare_method::{compare_impl_method, compare_const_impl};
155 use self::method::{MethodCallee, SelfSource};
156 use self::TupleArgumentsFlag::*;
158 /// The type of a local binding, including the revealed type for anon types.
159 #[derive(Copy, Clone, Debug)]
160 pub struct LocalTy<'tcx> {
162 revealed_ty: Ty<'tcx>
165 /// A wrapper for `InferCtxt`'s `in_progress_tables` field.
166 #[derive(Copy, Clone)]
167 struct MaybeInProgressTables<'a, 'tcx> {
168 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
171 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
172 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
173 match self.maybe_tables {
174 Some(tables) => tables.borrow(),
176 bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables")
181 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
182 match self.maybe_tables {
183 Some(tables) => tables.borrow_mut(),
185 bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables")
191 /// Closures defined within the function. For example:
194 /// bar(move|| { ... })
197 /// Here, the function `foo()` and the closure passed to
198 /// `bar()` will each have their own `FnCtxt`, but they will
199 /// share the inherited fields.
200 pub struct Inherited<'a, 'tcx> {
201 infcx: InferCtxt<'a, 'tcx>,
203 tables: MaybeInProgressTables<'a, 'tcx>,
205 locals: RefCell<HirIdMap<LocalTy<'tcx>>>,
207 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
209 // Some additional `Sized` obligations badly affect type inference.
210 // These obligations are added in a later stage of typeck.
211 deferred_sized_obligations: RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
213 // When we process a call like `c()` where `c` is a closure type,
214 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
215 // `FnOnce` closure. In that case, we defer full resolution of the
216 // call until upvar inference can kick in and make the
217 // decision. We keep these deferred resolutions grouped by the
218 // def-id of the closure, so that once we decide, we can easily go
219 // back and process them.
220 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
222 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
224 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
226 // Opaque types found in explicit return types and their
227 // associated fresh inference variable. Writeback resolves these
228 // variables to get the concrete type, which can be used to
229 // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
230 opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
232 /// Each type parameter has an implicit region bound that
233 /// indicates it must outlive at least the function body (the user
234 /// may specify stronger requirements). This field indicates the
235 /// region of the callee. If it is `None`, then the parameter
236 /// environment is for an item or something where the "callee" is
238 implicit_region_bound: Option<ty::Region<'tcx>>,
240 body_id: Option<hir::BodyId>,
243 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
244 type Target = InferCtxt<'a, 'tcx>;
245 fn deref(&self) -> &Self::Target {
250 /// When type-checking an expression, we propagate downward
251 /// whatever type hint we are able in the form of an `Expectation`.
252 #[derive(Copy, Clone, Debug)]
253 pub enum Expectation<'tcx> {
254 /// We know nothing about what type this expression should have.
257 /// This expression should have the type given (or some subtype).
258 ExpectHasType(Ty<'tcx>),
260 /// This expression will be cast to the `Ty`.
261 ExpectCastableToType(Ty<'tcx>),
263 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
264 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
265 ExpectRvalueLikeUnsized(Ty<'tcx>),
268 impl<'a, 'tcx> Expectation<'tcx> {
269 // Disregard "castable to" expectations because they
270 // can lead us astray. Consider for example `if cond
271 // {22} else {c} as u8` -- if we propagate the
272 // "castable to u8" constraint to 22, it will pick the
273 // type 22u8, which is overly constrained (c might not
274 // be a u8). In effect, the problem is that the
275 // "castable to" expectation is not the tightest thing
276 // we can say, so we want to drop it in this case.
277 // The tightest thing we can say is "must unify with
278 // else branch". Note that in the case of a "has type"
279 // constraint, this limitation does not hold.
281 // If the expected type is just a type variable, then don't use
282 // an expected type. Otherwise, we might write parts of the type
283 // when checking the 'then' block which are incompatible with the
285 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
287 ExpectHasType(ety) => {
288 let ety = fcx.shallow_resolve(ety);
289 if !ety.is_ty_var() {
295 ExpectRvalueLikeUnsized(ety) => {
296 ExpectRvalueLikeUnsized(ety)
302 /// Provides an expectation for an rvalue expression given an *optional*
303 /// hint, which is not required for type safety (the resulting type might
304 /// be checked higher up, as is the case with `&expr` and `box expr`), but
305 /// is useful in determining the concrete type.
307 /// The primary use case is where the expected type is a fat pointer,
308 /// like `&[isize]`. For example, consider the following statement:
310 /// let x: &[isize] = &[1, 2, 3];
312 /// In this case, the expected type for the `&[1, 2, 3]` expression is
313 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
314 /// expectation `ExpectHasType([isize])`, that would be too strong --
315 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
316 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
317 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
318 /// which still is useful, because it informs integer literals and the like.
319 /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
320 /// for examples of where this comes up,.
321 fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
322 match fcx.tcx.struct_tail_without_normalization(ty).kind {
323 ty::Slice(_) | ty::Str | ty::Dynamic(..) => {
324 ExpectRvalueLikeUnsized(ty)
326 _ => ExpectHasType(ty)
330 // Resolves `expected` by a single level if it is a variable. If
331 // there is no expected type or resolution is not possible (e.g.,
332 // no constraints yet present), just returns `None`.
333 fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
335 NoExpectation => NoExpectation,
336 ExpectCastableToType(t) => {
337 ExpectCastableToType(fcx.resolve_vars_if_possible(&t))
339 ExpectHasType(t) => {
340 ExpectHasType(fcx.resolve_vars_if_possible(&t))
342 ExpectRvalueLikeUnsized(t) => {
343 ExpectRvalueLikeUnsized(fcx.resolve_vars_if_possible(&t))
348 fn to_option(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
349 match self.resolve(fcx) {
350 NoExpectation => None,
351 ExpectCastableToType(ty) |
353 ExpectRvalueLikeUnsized(ty) => Some(ty),
357 /// It sometimes happens that we want to turn an expectation into
358 /// a **hard constraint** (i.e., something that must be satisfied
359 /// for the program to type-check). `only_has_type` will return
360 /// such a constraint, if it exists.
361 fn only_has_type(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
362 match self.resolve(fcx) {
363 ExpectHasType(ty) => Some(ty),
364 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
368 /// Like `only_has_type`, but instead of returning `None` if no
369 /// hard constraint exists, creates a fresh type variable.
370 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> Ty<'tcx> {
371 self.only_has_type(fcx)
373 fcx.next_ty_var(TypeVariableOrigin {
374 kind: TypeVariableOriginKind::MiscVariable,
381 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
388 fn maybe_mut_place(m: hir::Mutability) -> Self {
390 hir::MutMutable => Needs::MutPlace,
391 hir::MutImmutable => Needs::None,
396 #[derive(Copy, Clone)]
397 pub struct UnsafetyState {
399 pub unsafety: hir::Unsafety,
400 pub unsafe_push_count: u32,
405 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
406 UnsafetyState { def, unsafety, unsafe_push_count: 0, from_fn: true }
409 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
410 match self.unsafety {
411 // If this unsafe, then if the outer function was already marked as
412 // unsafe we shouldn't attribute the unsafe'ness to the block. This
413 // way the block can be warned about instead of ignoring this
414 // extraneous block (functions are never warned about).
415 hir::Unsafety::Unsafe if self.from_fn => *self,
418 let (unsafety, def, count) = match blk.rules {
419 hir::PushUnsafeBlock(..) =>
420 (unsafety, blk.hir_id, self.unsafe_push_count.checked_add(1).unwrap()),
421 hir::PopUnsafeBlock(..) =>
422 (unsafety, blk.hir_id, self.unsafe_push_count.checked_sub(1).unwrap()),
423 hir::UnsafeBlock(..) =>
424 (hir::Unsafety::Unsafe, blk.hir_id, self.unsafe_push_count),
426 (unsafety, self.def, self.unsafe_push_count),
430 unsafe_push_count: count,
437 #[derive(Debug, Copy, Clone)]
443 /// Tracks whether executing a node may exit normally (versus
444 /// return/break/panic, which "diverge", leaving dead code in their
445 /// wake). Tracked semi-automatically (through type variables marked
446 /// as diverging), with some manual adjustments for control-flow
447 /// primitives (approximating a CFG).
448 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
450 /// Potentially unknown, some cases converge,
451 /// others require a CFG to determine them.
454 /// Definitely known to diverge and therefore
455 /// not reach the next sibling or its parent.
457 /// The `Span` points to the expression
458 /// that caused us to diverge
459 /// (e.g. `return`, `break`, etc).
461 /// In some cases (e.g. a `match` expression
462 /// where all arms diverge), we may be
463 /// able to provide a more informative
464 /// message to the user.
465 /// If this is `None`, a default messsage
466 /// will be generated, which is suitable
468 custom_note: Option<&'static str>
471 /// Same as `Always` but with a reachability
472 /// warning already emitted.
476 // Convenience impls for combining `Diverges`.
478 impl ops::BitAnd for Diverges {
480 fn bitand(self, other: Self) -> Self {
481 cmp::min(self, other)
485 impl ops::BitOr for Diverges {
487 fn bitor(self, other: Self) -> Self {
488 cmp::max(self, other)
492 impl ops::BitAndAssign for Diverges {
493 fn bitand_assign(&mut self, other: Self) {
494 *self = *self & other;
498 impl ops::BitOrAssign for Diverges {
499 fn bitor_assign(&mut self, other: Self) {
500 *self = *self | other;
505 /// Creates a `Diverges::Always` with the provided `span` and the default note message.
506 fn always(span: Span) -> Diverges {
513 fn is_always(self) -> bool {
514 // Enum comparison ignores the
515 // contents of fields, so we just
516 // fill them in with garbage here.
517 self >= Diverges::Always {
524 pub struct BreakableCtxt<'tcx> {
527 // this is `null` for loops where break with a value is illegal,
528 // such as `while`, `for`, and `while let`
529 coerce: Option<DynamicCoerceMany<'tcx>>,
532 pub struct EnclosingBreakables<'tcx> {
533 stack: Vec<BreakableCtxt<'tcx>>,
534 by_id: HirIdMap<usize>,
537 impl<'tcx> EnclosingBreakables<'tcx> {
538 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
539 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
540 bug!("could not find enclosing breakable with id {}", target_id);
546 pub struct FnCtxt<'a, 'tcx> {
549 /// The parameter environment used for proving trait obligations
550 /// in this function. This can change when we descend into
551 /// closures (as they bring new things into scope), hence it is
552 /// not part of `Inherited` (as of the time of this writing,
553 /// closures do not yet change the environment, but they will
555 param_env: ty::ParamEnv<'tcx>,
557 /// Number of errors that had been reported when we started
558 /// checking this function. On exit, if we find that *more* errors
559 /// have been reported, we will skip regionck and other work that
560 /// expects the types within the function to be consistent.
561 // FIXME(matthewjasper) This should not exist, and it's not correct
562 // if type checking is run in parallel.
563 err_count_on_creation: usize,
565 /// If `Some`, this stores coercion information for returned
566 /// expressions. If `None`, this is in a context where return is
567 /// inappropriate, such as a const expression.
569 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
570 /// can track all the return expressions and then use them to
571 /// compute a useful coercion from the set, similar to a match
572 /// expression or other branching context. You can use methods
573 /// like `expected_ty` to access the declared return type (if
575 ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
577 /// First span of a return site that we find. Used in error messages.
578 ret_coercion_span: RefCell<Option<Span>>,
580 yield_ty: Option<Ty<'tcx>>,
582 ps: RefCell<UnsafetyState>,
584 /// Whether the last checked node generates a divergence (e.g.,
585 /// `return` will set this to `Always`). In general, when entering
586 /// an expression or other node in the tree, the initial value
587 /// indicates whether prior parts of the containing expression may
588 /// have diverged. It is then typically set to `Maybe` (and the
589 /// old value remembered) for processing the subparts of the
590 /// current expression. As each subpart is processed, they may set
591 /// the flag to `Always`, etc. Finally, at the end, we take the
592 /// result and "union" it with the original value, so that when we
593 /// return the flag indicates if any subpart of the parent
594 /// expression (up to and including this part) has diverged. So,
595 /// if you read it after evaluating a subexpression `X`, the value
596 /// you get indicates whether any subexpression that was
597 /// evaluating up to and including `X` diverged.
599 /// We currently use this flag only for diagnostic purposes:
601 /// - To warn about unreachable code: if, after processing a
602 /// sub-expression but before we have applied the effects of the
603 /// current node, we see that the flag is set to `Always`, we
604 /// can issue a warning. This corresponds to something like
605 /// `foo(return)`; we warn on the `foo()` expression. (We then
606 /// update the flag to `WarnedAlways` to suppress duplicate
607 /// reports.) Similarly, if we traverse to a fresh statement (or
608 /// tail expression) from a `Always` setting, we will issue a
609 /// warning. This corresponds to something like `{return;
610 /// foo();}` or `{return; 22}`, where we would warn on the
613 /// An expression represents dead code if, after checking it,
614 /// the diverges flag is set to something other than `Maybe`.
615 diverges: Cell<Diverges>,
617 /// Whether any child nodes have any type errors.
618 has_errors: Cell<bool>,
620 enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
622 inh: &'a Inherited<'a, 'tcx>,
625 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
626 type Target = Inherited<'a, 'tcx>;
627 fn deref(&self) -> &Self::Target {
632 /// Helper type of a temporary returned by `Inherited::build(...)`.
633 /// Necessary because we can't write the following bound:
634 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
635 pub struct InheritedBuilder<'tcx> {
636 infcx: infer::InferCtxtBuilder<'tcx>,
640 impl Inherited<'_, 'tcx> {
641 pub fn build(tcx: TyCtxt<'tcx>, def_id: DefId) -> InheritedBuilder<'tcx> {
642 let hir_id_root = if def_id.is_local() {
643 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
644 DefId::local(hir_id.owner)
650 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
656 impl<'tcx> InheritedBuilder<'tcx> {
657 fn enter<F, R>(&mut self, f: F) -> R
659 F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
661 let def_id = self.def_id;
662 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
666 impl Inherited<'a, 'tcx> {
667 fn new(infcx: InferCtxt<'a, 'tcx>, def_id: DefId) -> Self {
669 let item_id = tcx.hir().as_local_hir_id(def_id);
670 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by(id));
671 let implicit_region_bound = body_id.map(|body_id| {
672 let body = tcx.hir().body(body_id);
673 tcx.mk_region(ty::ReScope(region::Scope {
674 id: body.value.hir_id.local_id,
675 data: region::ScopeData::CallSite
680 tables: MaybeInProgressTables {
681 maybe_tables: infcx.in_progress_tables,
684 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
685 locals: RefCell::new(Default::default()),
686 deferred_sized_obligations: RefCell::new(Vec::new()),
687 deferred_call_resolutions: RefCell::new(Default::default()),
688 deferred_cast_checks: RefCell::new(Vec::new()),
689 deferred_generator_interiors: RefCell::new(Vec::new()),
690 opaque_types: RefCell::new(Default::default()),
691 implicit_region_bound,
696 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
697 debug!("register_predicate({:?})", obligation);
698 if obligation.has_escaping_bound_vars() {
699 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}",
704 .register_predicate_obligation(self, obligation);
707 fn register_predicates<I>(&self, obligations: I)
708 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>>
710 for obligation in obligations {
711 self.register_predicate(obligation);
715 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
716 self.register_predicates(infer_ok.obligations);
720 fn normalize_associated_types_in<T>(&self,
723 param_env: ty::ParamEnv<'tcx>,
725 where T : TypeFoldable<'tcx>
727 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
728 self.register_infer_ok_obligations(ok)
732 struct CheckItemTypesVisitor<'tcx> {
736 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
737 fn visit_item(&mut self, i: &'tcx hir::Item) {
738 check_item_type(self.tcx, i);
740 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
741 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
744 pub fn check_wf_new(tcx: TyCtxt<'_>) {
745 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
746 tcx.hir().krate().par_visit_all_item_likes(&mut visit);
749 fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
750 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
753 fn typeck_item_bodies(tcx: TyCtxt<'_>, crate_num: CrateNum) {
754 debug_assert!(crate_num == LOCAL_CRATE);
755 tcx.par_body_owners(|body_owner_def_id| {
756 tcx.ensure().typeck_tables_of(body_owner_def_id);
760 fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
761 wfcheck::check_item_well_formed(tcx, def_id);
764 fn check_trait_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
765 wfcheck::check_trait_item(tcx, def_id);
768 fn check_impl_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
769 wfcheck::check_impl_item(tcx, def_id);
772 pub fn provide(providers: &mut Providers<'_>) {
773 method::provide(providers);
774 *providers = Providers {
780 check_item_well_formed,
781 check_trait_item_well_formed,
782 check_impl_item_well_formed,
783 check_mod_item_types,
788 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
789 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
792 /// If this `DefId` is a "primary tables entry", returns
793 /// `Some((body_id, header, decl))` with information about
794 /// it's body-id, fn-header and fn-decl (if any). Otherwise,
797 /// If this function returns `Some`, then `typeck_tables(def_id)` will
798 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
799 /// may not succeed. In some cases where this function returns `None`
800 /// (notably closures), `typeck_tables(def_id)` would wind up
801 /// redirecting to the owning function.
805 ) -> Option<(hir::BodyId, Option<&hir::Ty>, Option<&hir::FnHeader>, Option<&hir::FnDecl>)> {
806 match tcx.hir().get(id) {
807 Node::Item(item) => {
809 hir::ItemKind::Const(ref ty, body) |
810 hir::ItemKind::Static(ref ty, _, body) =>
811 Some((body, Some(ty), None, None)),
812 hir::ItemKind::Fn(ref decl, ref header, .., body) =>
813 Some((body, None, Some(header), Some(decl))),
818 Node::TraitItem(item) => {
820 hir::TraitItemKind::Const(ref ty, Some(body)) =>
821 Some((body, Some(ty), None, None)),
822 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
823 Some((body, None, Some(&sig.header), Some(&sig.decl))),
828 Node::ImplItem(item) => {
830 hir::ImplItemKind::Const(ref ty, body) =>
831 Some((body, Some(ty), None, None)),
832 hir::ImplItemKind::Method(ref sig, body) =>
833 Some((body, None, Some(&sig.header), Some(&sig.decl))),
838 Node::AnonConst(constant) => Some((constant.body, None, None, None)),
843 fn has_typeck_tables(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
844 // Closures' tables come from their outermost function,
845 // as they are part of the same "inference environment".
846 let outer_def_id = tcx.closure_base_def_id(def_id);
847 if outer_def_id != def_id {
848 return tcx.has_typeck_tables(outer_def_id);
851 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
852 primary_body_of(tcx, id).is_some()
855 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: DefId) -> &DefIdSet {
856 &*tcx.typeck_tables_of(def_id).used_trait_imports
859 fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
860 // Closures' tables come from their outermost function,
861 // as they are part of the same "inference environment".
862 let outer_def_id = tcx.closure_base_def_id(def_id);
863 if outer_def_id != def_id {
864 return tcx.typeck_tables_of(outer_def_id);
867 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
868 let span = tcx.hir().span(id);
870 // Figure out what primary body this item has.
871 let (body_id, body_ty, fn_header, fn_decl) = primary_body_of(tcx, id)
873 span_bug!(span, "can't type-check body of {:?}", def_id);
875 let body = tcx.hir().body(body_id);
877 let tables = Inherited::build(tcx, def_id).enter(|inh| {
878 let param_env = tcx.param_env(def_id);
879 let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
880 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
881 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
882 AstConv::ty_of_fn(&fcx, header.unsafety, header.abi, decl)
887 check_abi(tcx, span, fn_sig.abi());
889 // Compute the fty from point of view of inside the fn.
891 tcx.liberate_late_bound_regions(def_id, &fn_sig);
893 inh.normalize_associated_types_in(body.value.span,
898 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
901 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
902 let expected_type = body_ty.and_then(|ty| match ty.kind {
903 hir::TyKind::Infer => Some(AstConv::ast_ty_to_ty(&fcx, ty)),
905 }).unwrap_or_else(|| tcx.type_of(def_id));
906 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
907 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
909 let revealed_ty = if tcx.features().impl_trait_in_bindings {
910 fcx.instantiate_opaque_types_from_value(
919 // Gather locals in statics (because of block expressions).
920 GatherLocalsVisitor { fcx: &fcx, parent_id: id, }.visit_body(body);
922 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
924 fcx.write_ty(id, revealed_ty);
929 // All type checking constraints were added, try to fallback unsolved variables.
930 fcx.select_obligations_where_possible(false, |_| {});
931 let mut fallback_has_occurred = false;
932 for ty in &fcx.unsolved_variables() {
933 fallback_has_occurred |= fcx.fallback_if_possible(ty);
935 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
937 // Even though coercion casts provide type hints, we check casts after fallback for
938 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
941 // Closure and generator analysis may run after fallback
942 // because they don't constrain other type variables.
943 fcx.closure_analyze(body);
944 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
945 fcx.resolve_generator_interiors(def_id);
947 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
948 let ty = fcx.normalize_ty(span, ty);
949 fcx.require_type_is_sized(ty, span, code);
951 fcx.select_all_obligations_or_error();
953 if fn_decl.is_some() {
954 fcx.regionck_fn(id, body);
956 fcx.regionck_expr(body);
959 fcx.resolve_type_vars_in_body(body)
962 // Consistency check our TypeckTables instance can hold all ItemLocalIds
963 // it will need to hold.
964 assert_eq!(tables.local_id_root, Some(DefId::local(id.owner)));
969 fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
970 if !tcx.sess.target.target.is_abi_supported(abi) {
971 struct_span_err!(tcx.sess, span, E0570,
972 "The ABI `{}` is not supported for the current target", abi).emit()
976 struct GatherLocalsVisitor<'a, 'tcx> {
977 fcx: &'a FnCtxt<'a, 'tcx>,
978 parent_id: hir::HirId,
981 impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
982 fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
985 // infer the variable's type
986 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
987 kind: TypeVariableOriginKind::TypeInference,
990 self.fcx.locals.borrow_mut().insert(nid, LocalTy {
997 // take type that the user specified
998 self.fcx.locals.borrow_mut().insert(nid, typ);
1005 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
1006 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1007 NestedVisitorMap::None
1010 // Add explicitly-declared locals.
1011 fn visit_local(&mut self, local: &'tcx hir::Local) {
1012 let local_ty = match local.ty {
1014 let o_ty = self.fcx.to_ty(&ty);
1016 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
1017 self.fcx.instantiate_opaque_types_from_value(
1026 let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(
1027 &UserType::Ty(revealed_ty)
1029 debug!("visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
1030 ty.hir_id, o_ty, revealed_ty, c_ty);
1031 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
1033 Some(LocalTy { decl_ty: o_ty, revealed_ty })
1037 self.assign(local.span, local.hir_id, local_ty);
1039 debug!("local variable {:?} is assigned type {}",
1041 self.fcx.ty_to_string(
1042 self.fcx.locals.borrow().get(&local.hir_id).unwrap().clone().decl_ty));
1043 intravisit::walk_local(self, local);
1046 // Add pattern bindings.
1047 fn visit_pat(&mut self, p: &'tcx hir::Pat) {
1048 if let PatKind::Binding(_, _, ident, _) = p.kind {
1049 let var_ty = self.assign(p.span, p.hir_id, None);
1051 if !self.fcx.tcx.features().unsized_locals {
1052 self.fcx.require_type_is_sized(var_ty, p.span,
1053 traits::VariableType(p.hir_id));
1056 debug!("pattern binding {} is assigned to {} with type {:?}",
1058 self.fcx.ty_to_string(
1059 self.fcx.locals.borrow().get(&p.hir_id).unwrap().clone().decl_ty),
1062 intravisit::walk_pat(self, p);
1065 // Don't descend into the bodies of nested closures
1068 _: intravisit::FnKind<'tcx>,
1069 _: &'tcx hir::FnDecl,
1076 /// When `check_fn` is invoked on a generator (i.e., a body that
1077 /// includes yield), it returns back some information about the yield
1079 struct GeneratorTypes<'tcx> {
1080 /// Type of value that is yielded.
1083 /// Types that are captured (see `GeneratorInterior` for more).
1086 /// Indicates if the generator is movable or static (immovable).
1087 movability: hir::GeneratorMovability,
1090 /// Helper used for fns and closures. Does the grungy work of checking a function
1091 /// body and returns the function context used for that purpose, since in the case of a fn item
1092 /// there is still a bit more to do.
1095 /// * inherited: other fields inherited from the enclosing fn (if any)
1096 fn check_fn<'a, 'tcx>(
1097 inherited: &'a Inherited<'a, 'tcx>,
1098 param_env: ty::ParamEnv<'tcx>,
1099 fn_sig: ty::FnSig<'tcx>,
1100 decl: &'tcx hir::FnDecl,
1102 body: &'tcx hir::Body,
1103 can_be_generator: Option<hir::GeneratorMovability>,
1104 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
1105 let mut fn_sig = fn_sig.clone();
1107 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1109 // Create the function context. This is either derived from scratch or,
1110 // in the case of closures, based on the outer context.
1111 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1112 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1114 let declared_ret_ty = fn_sig.output();
1115 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1116 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(
1121 debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
1122 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1123 fn_sig = fcx.tcx.mk_fn_sig(
1124 fn_sig.inputs().iter().cloned(),
1131 let span = body.value.span;
1133 fn_maybe_err(fcx.tcx, span, fn_sig.abi);
1135 if body.generator_kind.is_some() && can_be_generator.is_some() {
1136 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
1137 kind: TypeVariableOriginKind::TypeInference,
1140 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1141 fcx.yield_ty = Some(yield_ty);
1144 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id(fn_id));
1145 let outer_hir_id = fcx.tcx.hir().as_local_hir_id(outer_def_id).unwrap();
1146 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id, }.visit_body(body);
1148 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
1149 // (as it's created inside the body itself, not passed in from outside).
1150 let maybe_va_list = if fn_sig.c_variadic {
1151 let va_list_did = fcx.tcx.require_lang_item(
1152 lang_items::VaListTypeLangItem,
1153 Some(body.params.last().unwrap().span),
1155 let region = fcx.tcx.mk_region(ty::ReScope(region::Scope {
1156 id: body.value.hir_id.local_id,
1157 data: region::ScopeData::CallSite
1160 Some(fcx.tcx.type_of(va_list_did).subst(fcx.tcx, &[region.into()]))
1165 // Add formal parameters.
1166 for (param_ty, param) in
1167 fn_sig.inputs().iter().copied()
1168 .chain(maybe_va_list)
1171 // Check the pattern.
1172 fcx.check_pat_top(¶m.pat, param_ty, None);
1174 // Check that argument is Sized.
1175 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1176 // for simple cases like `fn foo(x: Trait)`,
1177 // where we would error once on the parameter as a whole, and once on the binding `x`.
1178 if param.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1179 fcx.require_type_is_sized(param_ty, decl.output.span(), traits::SizedArgumentType);
1182 fcx.write_ty(param.hir_id, param_ty);
1185 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1187 fcx.check_return_expr(&body.value);
1189 // We insert the deferred_generator_interiors entry after visiting the body.
1190 // This ensures that all nested generators appear before the entry of this generator.
1191 // resolve_generator_interiors relies on this property.
1192 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
1193 let interior = fcx.next_ty_var(TypeVariableOrigin {
1194 kind: TypeVariableOriginKind::MiscVariable,
1197 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
1198 Some(GeneratorTypes {
1199 yield_ty: fcx.yield_ty.unwrap(),
1201 movability: can_be_generator.unwrap(),
1207 // Finalize the return check by taking the LUB of the return types
1208 // we saw and assigning it to the expected return type. This isn't
1209 // really expected to fail, since the coercions would have failed
1210 // earlier when trying to find a LUB.
1212 // However, the behavior around `!` is sort of complex. In the
1213 // event that the `actual_return_ty` comes back as `!`, that
1214 // indicates that the fn either does not return or "returns" only
1215 // values of type `!`. In this case, if there is an expected
1216 // return type that is *not* `!`, that should be ok. But if the
1217 // return type is being inferred, we want to "fallback" to `!`:
1219 // let x = move || panic!();
1221 // To allow for that, I am creating a type variable with diverging
1222 // fallback. This was deemed ever so slightly better than unifying
1223 // the return value with `!` because it allows for the caller to
1224 // make more assumptions about the return type (e.g., they could do
1226 // let y: Option<u32> = Some(x());
1228 // which would then cause this return type to become `u32`, not
1230 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1231 let mut actual_return_ty = coercion.complete(&fcx);
1232 if actual_return_ty.is_never() {
1233 actual_return_ty = fcx.next_diverging_ty_var(
1234 TypeVariableOrigin {
1235 kind: TypeVariableOriginKind::DivergingFn,
1240 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1242 // Check that the main return type implements the termination trait.
1243 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1244 if let Some((def_id, EntryFnType::Main)) = fcx.tcx.entry_fn(LOCAL_CRATE) {
1245 let main_id = fcx.tcx.hir().as_local_hir_id(def_id).unwrap();
1246 if main_id == fn_id {
1247 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1248 let trait_ref = ty::TraitRef::new(term_id, substs);
1249 let return_ty_span = decl.output.span();
1250 let cause = traits::ObligationCause::new(
1251 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1253 inherited.register_predicate(
1254 traits::Obligation::new(
1255 cause, param_env, trait_ref.to_predicate()));
1260 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1261 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1262 if panic_impl_did == fcx.tcx.hir().local_def_id(fn_id) {
1263 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1264 // at this point we don't care if there are duplicate handlers or if the handler has
1265 // the wrong signature as this value we'll be used when writing metadata and that
1266 // only happens if compilation succeeded
1267 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1269 if declared_ret_ty.kind != ty::Never {
1270 fcx.tcx.sess.span_err(
1272 "return type should be `!`",
1276 let inputs = fn_sig.inputs();
1277 let span = fcx.tcx.hir().span(fn_id);
1278 if inputs.len() == 1 {
1279 let arg_is_panic_info = match inputs[0].kind {
1280 ty::Ref(region, ty, mutbl) => match ty.kind {
1281 ty::Adt(ref adt, _) => {
1282 adt.did == panic_info_did &&
1283 mutbl == hir::Mutability::MutImmutable &&
1284 *region != RegionKind::ReStatic
1291 if !arg_is_panic_info {
1292 fcx.tcx.sess.span_err(
1293 decl.inputs[0].span,
1294 "argument should be `&PanicInfo`",
1298 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1299 if let ItemKind::Fn(_, _, ref generics, _) = item.kind {
1300 if !generics.params.is_empty() {
1301 fcx.tcx.sess.span_err(
1303 "should have no type parameters",
1309 let span = fcx.tcx.sess.source_map().def_span(span);
1310 fcx.tcx.sess.span_err(span, "function should have one argument");
1313 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1318 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1319 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1320 if alloc_error_handler_did == fcx.tcx.hir().local_def_id(fn_id) {
1321 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1322 if declared_ret_ty.kind != ty::Never {
1323 fcx.tcx.sess.span_err(
1325 "return type should be `!`",
1329 let inputs = fn_sig.inputs();
1330 let span = fcx.tcx.hir().span(fn_id);
1331 if inputs.len() == 1 {
1332 let arg_is_alloc_layout = match inputs[0].kind {
1333 ty::Adt(ref adt, _) => {
1334 adt.did == alloc_layout_did
1339 if !arg_is_alloc_layout {
1340 fcx.tcx.sess.span_err(
1341 decl.inputs[0].span,
1342 "argument should be `Layout`",
1346 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1347 if let ItemKind::Fn(_, _, ref generics, _) = item.kind {
1348 if !generics.params.is_empty() {
1349 fcx.tcx.sess.span_err(
1351 "`#[alloc_error_handler]` function should have no type \
1358 let span = fcx.tcx.sess.source_map().def_span(span);
1359 fcx.tcx.sess.span_err(span, "function should have one argument");
1362 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1370 fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1371 let def_id = tcx.hir().local_def_id(id);
1372 let def = tcx.adt_def(def_id);
1373 def.destructor(tcx); // force the destructor to be evaluated
1374 check_representable(tcx, span, def_id);
1376 if def.repr.simd() {
1377 check_simd(tcx, span, def_id);
1380 check_transparent(tcx, span, def_id);
1381 check_packed(tcx, span, def_id);
1384 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1385 let def_id = tcx.hir().local_def_id(id);
1386 let def = tcx.adt_def(def_id);
1387 def.destructor(tcx); // force the destructor to be evaluated
1388 check_representable(tcx, span, def_id);
1389 check_transparent(tcx, span, def_id);
1390 check_union_fields(tcx, span, def_id);
1391 check_packed(tcx, span, def_id);
1394 /// When the `#![feature(untagged_unions)]` gate is active,
1395 /// check that the fields of the `union` does not contain fields that need dropping.
1396 fn check_union_fields(tcx: TyCtxt<'_>, _: Span, item_def_id: DefId) -> bool {
1397 // Without the feature we check Copy types only later
1398 if !tcx.features().untagged_unions {
1401 let item_type = tcx.type_of(item_def_id);
1402 if let ty::Adt(def, substs) = item_type.sty {
1404 let fields = &def.non_enum_variant().fields;
1405 for field in fields {
1406 let field_ty = field.ty(tcx, substs);
1407 // We are currently checking the type this field came from, so it must be local.
1408 let field_span = tcx.hir().span_if_local(field.did).unwrap();
1409 let param_env = tcx.param_env(field.did);
1410 if field_ty.needs_drop(tcx, param_env) {
1411 struct_span_err!(tcx.sess, field_span, E0740,
1412 "unions may not contain fields that need dropping")
1413 .span_note(field_span,
1414 "`std::mem::ManuallyDrop` can be used to wrap the type")
1424 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
1425 /// projections that would result in "inheriting lifetimes".
1426 fn check_opaque<'tcx>(
1429 substs: SubstsRef<'tcx>,
1431 origin: &hir::OpaqueTyOrigin,
1433 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
1434 check_opaque_for_cycles(tcx, def_id, substs, span, origin);
1437 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
1438 /// in "inheriting lifetimes".
1439 fn check_opaque_for_inheriting_lifetimes(
1444 let item = tcx.hir().expect_item(
1445 tcx.hir().as_local_hir_id(def_id).expect("opaque type is not local"));
1446 debug!("check_opaque_for_inheriting_lifetimes: def_id={:?} span={:?} item={:?}",
1447 def_id, span, item);
1450 struct ProhibitOpaqueVisitor<'tcx> {
1451 opaque_identity_ty: Ty<'tcx>,
1452 generics: &'tcx ty::Generics,
1455 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
1456 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
1457 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
1458 if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) }
1461 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1462 debug!("check_opaque_for_inheriting_lifetimes: (visit_region) r={:?}", r);
1463 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
1464 return *index < self.generics.parent_count as u32;
1467 r.super_visit_with(self)
1471 let prohibit_opaque = match item.kind {
1472 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn, .. }) |
1473 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn, .. }) => {
1474 let mut visitor = ProhibitOpaqueVisitor {
1475 opaque_identity_ty: tcx.mk_opaque(
1476 def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1477 generics: tcx.generics_of(def_id),
1479 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1481 tcx.predicates_of(def_id).predicates.iter().any(
1482 |(predicate, _)| predicate.visit_with(&mut visitor))
1487 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1488 if prohibit_opaque {
1489 let is_async = match item.kind {
1490 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1491 hir::OpaqueTyOrigin::AsyncFn => true,
1494 _ => unreachable!(),
1497 tcx.sess.span_err(span, &format!(
1498 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1500 if is_async { "async fn" } else { "impl Trait" },
1505 /// Checks that an opaque type does not contain cycles.
1506 fn check_opaque_for_cycles<'tcx>(
1509 substs: SubstsRef<'tcx>,
1511 origin: &hir::OpaqueTyOrigin,
1513 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1514 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1516 tcx.sess, span, E0733,
1517 "recursion in an `async fn` requires boxing",
1519 .span_label(span, "recursive `async fn`")
1520 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`.")
1523 let mut err = struct_span_err!(
1524 tcx.sess, span, E0720,
1525 "opaque type expands to a recursive type",
1527 err.span_label(span, "expands to a recursive type");
1528 if let ty::Opaque(..) = partially_expanded_type.kind {
1529 err.note("type resolves to itself");
1531 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1538 // Forbid defining intrinsics in Rust code,
1539 // as they must always be defined by the compiler.
1540 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1541 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1542 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1546 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
1548 "check_item_type(it.hir_id={}, it.name={})",
1550 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1552 let _indenter = indenter();
1554 // Consts can play a role in type-checking, so they are included here.
1555 hir::ItemKind::Static(..) => {
1556 let def_id = tcx.hir().local_def_id(it.hir_id);
1557 tcx.typeck_tables_of(def_id);
1558 maybe_check_static_with_link_section(tcx, def_id, it.span);
1560 hir::ItemKind::Const(..) => {
1561 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1563 hir::ItemKind::Enum(ref enum_definition, _) => {
1564 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1566 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1567 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1568 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1569 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1570 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1571 check_impl_items_against_trait(
1578 let trait_def_id = impl_trait_ref.def_id;
1579 check_on_unimplemented(tcx, trait_def_id, it);
1582 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1583 let def_id = tcx.hir().local_def_id(it.hir_id);
1584 check_on_unimplemented(tcx, def_id, it);
1586 for item in items.iter() {
1587 let item = tcx.hir().trait_item(item.id);
1588 if let hir::TraitItemKind::Method(sig, _) = &item.kind {
1589 let abi = sig.header.abi;
1590 fn_maybe_err(tcx, item.ident.span, abi);
1594 hir::ItemKind::Struct(..) => {
1595 check_struct(tcx, it.hir_id, it.span);
1597 hir::ItemKind::Union(..) => {
1598 check_union(tcx, it.hir_id, it.span);
1600 hir::ItemKind::OpaqueTy(hir::OpaqueTy{origin, ..}) => {
1601 let def_id = tcx.hir().local_def_id(it.hir_id);
1603 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1604 check_opaque(tcx, def_id, substs, it.span, &origin);
1606 hir::ItemKind::TyAlias(..) => {
1607 let def_id = tcx.hir().local_def_id(it.hir_id);
1608 let pty_ty = tcx.type_of(def_id);
1609 let generics = tcx.generics_of(def_id);
1610 check_bounds_are_used(tcx, &generics, pty_ty);
1612 hir::ItemKind::ForeignMod(ref m) => {
1613 check_abi(tcx, it.span, m.abi);
1615 if m.abi == Abi::RustIntrinsic {
1616 for item in &m.items {
1617 intrinsic::check_intrinsic_type(tcx, item);
1619 } else if m.abi == Abi::PlatformIntrinsic {
1620 for item in &m.items {
1621 intrinsic::check_platform_intrinsic_type(tcx, item);
1624 for item in &m.items {
1625 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1626 let own_counts = generics.own_counts();
1627 if generics.params.len() - own_counts.lifetimes != 0 {
1628 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1629 (_, 0) => ("type", "types", Some("u32")),
1630 // We don't specify an example value, because we can't generate
1631 // a valid value for any type.
1632 (0, _) => ("const", "consts", None),
1633 _ => ("type or const", "types or consts", None),
1639 "foreign items may not have {} parameters",
1643 &format!("can't have {} parameters", kinds),
1645 // FIXME: once we start storing spans for type arguments, turn this
1646 // into a suggestion.
1648 "replace the {} parameters with concrete {}{}",
1651 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1656 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.kind {
1657 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1662 _ => { /* nothing to do */ }
1666 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1667 // Only restricted on wasm32 target for now
1668 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1672 // If `#[link_section]` is missing, then nothing to verify
1673 let attrs = tcx.codegen_fn_attrs(id);
1674 if attrs.link_section.is_none() {
1678 // For the wasm32 target statics with `#[link_section]` are placed into custom
1679 // sections of the final output file, but this isn't link custom sections of
1680 // other executable formats. Namely we can only embed a list of bytes,
1681 // nothing with pointers to anything else or relocations. If any relocation
1682 // show up, reject them here.
1683 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1684 // the consumer's responsibility to ensure all bytes that have been read
1685 // have defined values.
1686 let instance = ty::Instance::mono(tcx, id);
1687 let cid = GlobalId {
1691 let param_env = ty::ParamEnv::reveal_all();
1692 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1693 let alloc = if let ConstValue::ByRef { alloc, .. } = static_.val {
1696 bug!("Matching on non-ByRef static")
1698 if alloc.relocations().len() != 0 {
1699 let msg = "statics with a custom `#[link_section]` must be a \
1700 simple list of bytes on the wasm target with no \
1701 extra levels of indirection such as references";
1702 tcx.sess.span_err(span, msg);
1707 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item) {
1708 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1709 // an error would be reported if this fails.
1710 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1713 fn report_forbidden_specialization(
1715 impl_item: &hir::ImplItem,
1718 let mut err = struct_span_err!(
1719 tcx.sess, impl_item.span, E0520,
1720 "`{}` specializes an item from a parent `impl`, but \
1721 that item is not marked `default`",
1723 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1726 match tcx.span_of_impl(parent_impl) {
1728 err.span_label(span, "parent `impl` is here");
1729 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1733 err.note(&format!("parent implementation is in crate `{}`", cname));
1740 fn check_specialization_validity<'tcx>(
1742 trait_def: &ty::TraitDef,
1743 trait_item: &ty::AssocItem,
1745 impl_item: &hir::ImplItem,
1747 let kind = match impl_item.kind {
1748 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1749 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1750 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1751 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1754 let mut ancestor_impls = trait_def.ancestors(tcx, impl_id)
1756 .filter_map(|parent| {
1757 if parent.is_from_trait() {
1760 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
1765 if ancestor_impls.peek().is_none() {
1766 // No parent, nothing to specialize.
1770 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
1772 // Parent impl exists, and contains the parent item we're trying to specialize, but
1773 // doesn't mark it `default`.
1774 Some(parent_item) if tcx.impl_item_is_final(&parent_item) => {
1775 Some(Err(parent_impl.def_id()))
1778 // Parent impl contains item and makes it specializable.
1783 // Parent impl doesn't mention the item. This means it's inherited from the
1784 // grandparent. In that case, if parent is a `default impl`, inherited items use the
1785 // "defaultness" from the grandparent, else they are final.
1786 None => if tcx.impl_is_default(parent_impl.def_id()) {
1789 Some(Err(parent_impl.def_id()))
1794 // If `opt_result` is `None`, we have only encoutered `default impl`s that don't contain the
1795 // item. This is allowed, the item isn't actually getting specialized here.
1796 let result = opt_result.unwrap_or(Ok(()));
1798 if let Err(parent_impl) = result {
1799 report_forbidden_specialization(tcx, impl_item, parent_impl);
1803 fn check_impl_items_against_trait<'tcx>(
1807 impl_trait_ref: ty::TraitRef<'tcx>,
1808 impl_item_refs: &[hir::ImplItemRef],
1810 let impl_span = tcx.sess.source_map().def_span(impl_span);
1812 // If the trait reference itself is erroneous (so the compilation is going
1813 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1814 // isn't populated for such impls.
1815 if impl_trait_ref.references_error() { return; }
1817 // Locate trait definition and items
1818 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1819 let mut overridden_associated_type = None;
1821 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1823 // Check existing impl methods to see if they are both present in trait
1824 // and compatible with trait signature
1825 for impl_item in impl_items() {
1826 let ty_impl_item = tcx.associated_item(
1827 tcx.hir().local_def_id(impl_item.hir_id));
1828 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1829 .find(|ac| Namespace::from(&impl_item.kind) == Namespace::from(ac.kind) &&
1830 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1832 // Not compatible, but needed for the error message
1833 tcx.associated_items(impl_trait_ref.def_id)
1834 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1837 // Check that impl definition matches trait definition
1838 if let Some(ty_trait_item) = ty_trait_item {
1839 match impl_item.kind {
1840 hir::ImplItemKind::Const(..) => {
1841 // Find associated const definition.
1842 if ty_trait_item.kind == ty::AssocKind::Const {
1843 compare_const_impl(tcx,
1849 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1850 "item `{}` is an associated const, \
1851 which doesn't match its trait `{}`",
1854 err.span_label(impl_item.span, "does not match trait");
1855 // We can only get the spans from local trait definition
1856 // Same for E0324 and E0325
1857 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1858 err.span_label(trait_span, "item in trait");
1863 hir::ImplItemKind::Method(..) => {
1864 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1865 if ty_trait_item.kind == ty::AssocKind::Method {
1866 compare_impl_method(tcx,
1873 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1874 "item `{}` is an associated method, \
1875 which doesn't match its trait `{}`",
1878 err.span_label(impl_item.span, "does not match trait");
1879 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1880 err.span_label(trait_span, "item in trait");
1885 hir::ImplItemKind::OpaqueTy(..) |
1886 hir::ImplItemKind::TyAlias(_) => {
1887 if ty_trait_item.kind == ty::AssocKind::Type {
1888 if ty_trait_item.defaultness.has_value() {
1889 overridden_associated_type = Some(impl_item);
1892 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1893 "item `{}` is an associated type, \
1894 which doesn't match its trait `{}`",
1897 err.span_label(impl_item.span, "does not match trait");
1898 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1899 err.span_label(trait_span, "item in trait");
1906 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1910 // Check for missing items from trait
1911 let mut missing_items = Vec::new();
1912 let mut invalidated_items = Vec::new();
1913 let associated_type_overridden = overridden_associated_type.is_some();
1914 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1915 let is_implemented = trait_def.ancestors(tcx, impl_id)
1916 .leaf_def(tcx, trait_item.ident, trait_item.kind)
1917 .map(|node_item| !node_item.node.is_from_trait())
1920 if !is_implemented && !tcx.impl_is_default(impl_id) {
1921 if !trait_item.defaultness.has_value() {
1922 missing_items.push(trait_item);
1923 } else if associated_type_overridden {
1924 invalidated_items.push(trait_item.ident);
1929 if !missing_items.is_empty() {
1930 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1931 "not all trait items implemented, missing: `{}`",
1932 missing_items.iter()
1933 .map(|trait_item| trait_item.ident.to_string())
1934 .collect::<Vec<_>>().join("`, `"));
1935 err.span_label(impl_span, format!("missing `{}` in implementation",
1936 missing_items.iter()
1937 .map(|trait_item| trait_item.ident.to_string())
1938 .collect::<Vec<_>>().join("`, `")));
1939 for trait_item in missing_items {
1940 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1941 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1943 err.note_trait_signature(trait_item.ident.to_string(),
1944 trait_item.signature(tcx));
1950 if !invalidated_items.is_empty() {
1951 let invalidator = overridden_associated_type.unwrap();
1952 span_err!(tcx.sess, invalidator.span, E0399,
1953 "the following trait items need to be reimplemented \
1954 as `{}` was overridden: `{}`",
1956 invalidated_items.iter()
1957 .map(|name| name.to_string())
1958 .collect::<Vec<_>>().join("`, `"))
1962 /// Checks whether a type can be represented in memory. In particular, it
1963 /// identifies types that contain themselves without indirection through a
1964 /// pointer, which would mean their size is unbounded.
1965 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
1966 let rty = tcx.type_of(item_def_id);
1968 // Check that it is possible to represent this type. This call identifies
1969 // (1) types that contain themselves and (2) types that contain a different
1970 // recursive type. It is only necessary to throw an error on those that
1971 // contain themselves. For case 2, there must be an inner type that will be
1972 // caught by case 1.
1973 match rty.is_representable(tcx, sp) {
1974 Representability::SelfRecursive(spans) => {
1975 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1977 err.span_label(span, "recursive without indirection");
1982 Representability::Representable | Representability::ContainsRecursive => (),
1987 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1988 let t = tcx.type_of(def_id);
1989 if let ty::Adt(def, substs) = t.kind {
1990 if def.is_struct() {
1991 let fields = &def.non_enum_variant().fields;
1992 if fields.is_empty() {
1993 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1996 let e = fields[0].ty(tcx, substs);
1997 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1998 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1999 .span_label(sp, "SIMD elements must have the same type")
2004 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
2005 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
2007 span_err!(tcx.sess, sp, E0077,
2008 "SIMD vector element type should be machine type");
2016 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2017 let repr = tcx.adt_def(def_id).repr;
2019 for attr in tcx.get_attrs(def_id).iter() {
2020 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
2021 if let attr::ReprPacked(pack) = r {
2022 if let Some(repr_pack) = repr.pack {
2023 if pack as u64 != repr_pack.bytes() {
2025 tcx.sess, sp, E0634,
2026 "type has conflicting packed representation hints"
2033 if repr.align.is_some() {
2034 struct_span_err!(tcx.sess, sp, E0587,
2035 "type has conflicting packed and align representation hints").emit();
2037 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
2038 struct_span_err!(tcx.sess, sp, E0588,
2039 "packed type cannot transitively contain a `[repr(align)]` type").emit();
2044 fn check_packed_inner(tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec<DefId>) -> bool {
2045 let t = tcx.type_of(def_id);
2046 if stack.contains(&def_id) {
2047 debug!("check_packed_inner: {:?} is recursive", t);
2050 if let ty::Adt(def, substs) = t.kind {
2051 if def.is_struct() || def.is_union() {
2052 if tcx.adt_def(def.did).repr.align.is_some() {
2055 // push struct def_id before checking fields
2057 for field in &def.non_enum_variant().fields {
2058 let f = field.ty(tcx, substs);
2059 if let ty::Adt(def, _) = f.kind {
2060 if check_packed_inner(tcx, def.did, stack) {
2065 // only need to pop if not early out
2072 /// Emit an error when encountering more or less than one variant in a transparent enum.
2073 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2074 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
2075 tcx.hir().span_if_local(variant.def_id).unwrap()
2078 "needs exactly one variant, but has {}",
2081 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2082 err.span_label(sp, &msg);
2083 if let &[ref start @ .., ref end] = &variant_spans[..] {
2084 for variant_span in start {
2085 err.span_label(*variant_span, "");
2087 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2092 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2094 fn bad_non_zero_sized_fields<'tcx>(
2096 adt: &'tcx ty::AdtDef,
2098 field_spans: impl Iterator<Item = Span>,
2101 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2102 let mut err = struct_span_err!(
2106 "{}transparent {} {}",
2107 if adt.is_enum() { "the variant of a " } else { "" },
2111 err.span_label(sp, &msg);
2112 for sp in field_spans {
2113 err.span_label(sp, "this field is non-zero-sized");
2118 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2119 let adt = tcx.adt_def(def_id);
2120 if !adt.repr.transparent() {
2123 let sp = tcx.sess.source_map().def_span(sp);
2126 if !tcx.features().transparent_enums {
2128 &tcx.sess.parse_sess,
2129 sym::transparent_enums,
2131 GateIssue::Language,
2132 "transparent enums are unstable",
2135 if adt.variants.len() != 1 {
2136 bad_variant_count(tcx, adt, sp, def_id);
2137 if adt.variants.is_empty() {
2138 // Don't bother checking the fields. No variants (and thus no fields) exist.
2144 if adt.is_union() && !tcx.features().transparent_unions {
2145 emit_feature_err(&tcx.sess.parse_sess,
2146 sym::transparent_unions,
2148 GateIssue::Language,
2149 "transparent unions are unstable");
2152 // For each field, figure out if it's known to be a ZST and align(1)
2153 let field_infos = adt.all_fields().map(|field| {
2154 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2155 let param_env = tcx.param_env(field.did);
2156 let layout = tcx.layout_of(param_env.and(ty));
2157 // We are currently checking the type this field came from, so it must be local
2158 let span = tcx.hir().span_if_local(field.did).unwrap();
2159 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2160 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2164 let non_zst_fields = field_infos.clone().filter_map(|(span, zst, _align1)| if !zst {
2169 let non_zst_count = non_zst_fields.clone().count();
2170 if non_zst_count != 1 {
2171 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2173 for (span, zst, align1) in field_infos {
2179 "zero-sized field in transparent {} has alignment larger than 1",
2181 ).span_label(span, "has alignment larger than 1").emit();
2186 #[allow(trivial_numeric_casts)]
2187 pub fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, vs: &'tcx [hir::Variant], id: hir::HirId) {
2188 let def_id = tcx.hir().local_def_id(id);
2189 let def = tcx.adt_def(def_id);
2190 def.destructor(tcx); // force the destructor to be evaluated
2193 let attributes = tcx.get_attrs(def_id);
2194 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2196 tcx.sess, attr.span, E0084,
2197 "unsupported representation for zero-variant enum")
2198 .span_label(sp, "zero-variant enum")
2203 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2204 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2205 if !tcx.features().repr128 {
2206 emit_feature_err(&tcx.sess.parse_sess,
2209 GateIssue::Language,
2210 "repr with 128-bit type is unstable");
2215 if let Some(ref e) = v.disr_expr {
2216 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2220 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2222 |var: &hir::Variant| match var.data {
2223 hir::VariantData::Unit(..) => true,
2227 let has_disr = |var: &hir::Variant| var.disr_expr.is_some();
2228 let has_non_units = vs.iter().any(|var| !is_unit(var));
2229 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2230 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2232 if disr_non_unit || (disr_units && has_non_units) {
2233 let mut err = struct_span_err!(tcx.sess, sp, E0732,
2234 "`#[repr(inttype)]` must be specified");
2239 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2240 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2241 // Check for duplicate discriminant values
2242 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2243 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2244 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2245 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2246 let i_span = match variant_i.disr_expr {
2247 Some(ref expr) => tcx.hir().span(expr.hir_id),
2248 None => tcx.hir().span(variant_i_hir_id)
2250 let span = match v.disr_expr {
2251 Some(ref expr) => tcx.hir().span(expr.hir_id),
2254 struct_span_err!(tcx.sess, span, E0081,
2255 "discriminant value `{}` already exists", disr_vals[i])
2256 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2257 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
2260 disr_vals.push(discr);
2263 check_representable(tcx, sp, def_id);
2264 check_transparent(tcx, sp, def_id);
2267 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span, qpath: &QPath) {
2268 span_err!(tcx.sess, span, E0533,
2269 "expected unit struct/variant or constant, found {} `{}`",
2271 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
2274 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2275 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2279 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
2280 -> &'tcx ty::GenericPredicates<'tcx>
2283 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2284 let item_id = tcx.hir().ty_param_owner(hir_id);
2285 let item_def_id = tcx.hir().local_def_id(item_id);
2286 let generics = tcx.generics_of(item_def_id);
2287 let index = generics.param_def_id_to_index[&def_id];
2288 tcx.arena.alloc(ty::GenericPredicates {
2290 predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
2292 ty::Predicate::Trait(ref data)
2293 if data.skip_binder().self_ty().is_param(index) => {
2294 // HACK(eddyb) should get the original `Span`.
2295 let span = tcx.def_span(def_id);
2296 Some((predicate, span))
2306 def: Option<&ty::GenericParamDef>,
2308 ) -> Option<ty::Region<'tcx>> {
2310 Some(def) => infer::EarlyBoundRegion(span, def.name),
2311 None => infer::MiscVariable(span)
2313 Some(self.next_region_var(v))
2316 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2317 if let Some(param) = param {
2318 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2323 self.next_ty_var(TypeVariableOrigin {
2324 kind: TypeVariableOriginKind::TypeInference,
2333 param: Option<&ty::GenericParamDef>,
2335 ) -> &'tcx Const<'tcx> {
2336 if let Some(param) = param {
2337 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2342 self.next_const_var(ty, ConstVariableOrigin {
2343 kind: ConstVariableOriginKind::ConstInference,
2349 fn projected_ty_from_poly_trait_ref(&self,
2352 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2355 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2357 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2361 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2364 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2365 if ty.has_escaping_bound_vars() {
2366 ty // FIXME: normalization and escaping regions
2368 self.normalize_associated_types_in(span, &ty)
2372 fn set_tainted_by_errors(&self) {
2373 self.infcx.set_tainted_by_errors()
2376 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2377 self.write_ty(hir_id, ty)
2381 /// Controls whether the arguments are tupled. This is used for the call
2384 /// Tupling means that all call-side arguments are packed into a tuple and
2385 /// passed as a single parameter. For example, if tupling is enabled, this
2388 /// fn f(x: (isize, isize))
2390 /// Can be called as:
2397 #[derive(Clone, Eq, PartialEq)]
2398 enum TupleArgumentsFlag {
2403 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2405 inh: &'a Inherited<'a, 'tcx>,
2406 param_env: ty::ParamEnv<'tcx>,
2407 body_id: hir::HirId,
2408 ) -> FnCtxt<'a, 'tcx> {
2412 err_count_on_creation: inh.tcx.sess.err_count(),
2414 ret_coercion_span: RefCell::new(None),
2416 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2417 hir::CRATE_HIR_ID)),
2418 diverges: Cell::new(Diverges::Maybe),
2419 has_errors: Cell::new(false),
2420 enclosing_breakables: RefCell::new(EnclosingBreakables {
2422 by_id: Default::default(),
2428 pub fn sess(&self) -> &Session {
2432 pub fn errors_reported_since_creation(&self) -> bool {
2433 self.tcx.sess.err_count() > self.err_count_on_creation
2436 /// Produces warning on the given node, if the current point in the
2437 /// function is unreachable, and there hasn't been another warning.
2438 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2439 // FIXME: Combine these two 'if' expressions into one once
2440 // let chains are implemented
2441 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2442 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2443 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2444 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2445 if !span.is_desugaring(DesugaringKind::CondTemporary) &&
2446 !span.is_desugaring(DesugaringKind::Async) &&
2447 !orig_span.is_desugaring(DesugaringKind::Await)
2449 self.diverges.set(Diverges::WarnedAlways);
2451 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2453 let msg = format!("unreachable {}", kind);
2454 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2455 .span_label(span, &msg)
2458 custom_note.unwrap_or("any code following this expression is unreachable"),
2467 code: ObligationCauseCode<'tcx>)
2468 -> ObligationCause<'tcx> {
2469 ObligationCause::new(span, self.body_id, code)
2472 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2473 self.cause(span, ObligationCauseCode::MiscObligation)
2476 /// Resolves type variables in `ty` if possible. Unlike the infcx
2477 /// version (resolve_vars_if_possible), this version will
2478 /// also select obligations if it seems useful, in an effort
2479 /// to get more type information.
2480 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2481 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2483 // No Infer()? Nothing needs doing.
2484 if !ty.has_infer_types() {
2485 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2489 // If `ty` is a type variable, see whether we already know what it is.
2490 ty = self.resolve_vars_if_possible(&ty);
2491 if !ty.has_infer_types() {
2492 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2496 // If not, try resolving pending obligations as much as
2497 // possible. This can help substantially when there are
2498 // indirect dependencies that don't seem worth tracking
2500 self.select_obligations_where_possible(false, |_| {});
2501 ty = self.resolve_vars_if_possible(&ty);
2503 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2507 fn record_deferred_call_resolution(
2509 closure_def_id: DefId,
2510 r: DeferredCallResolution<'tcx>,
2512 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2513 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2516 fn remove_deferred_call_resolutions(
2518 closure_def_id: DefId,
2519 ) -> Vec<DeferredCallResolution<'tcx>> {
2520 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2521 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2524 pub fn tag(&self) -> String {
2525 format!("{:p}", self)
2528 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2529 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2530 span_bug!(span, "no type for local variable {}",
2531 self.tcx.hir().node_to_string(nid))
2536 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2537 debug!("write_ty({:?}, {:?}) in fcx {}",
2538 id, self.resolve_vars_if_possible(&ty), self.tag());
2539 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2541 if ty.references_error() {
2542 self.has_errors.set(true);
2543 self.set_tainted_by_errors();
2547 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2548 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2551 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2552 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2555 pub fn write_method_call(&self,
2557 method: MethodCallee<'tcx>) {
2558 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2559 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2560 self.write_substs(hir_id, method.substs);
2562 // When the method is confirmed, the `method.substs` includes
2563 // parameters from not just the method, but also the impl of
2564 // the method -- in particular, the `Self` type will be fully
2565 // resolved. However, those are not something that the "user
2566 // specified" -- i.e., those types come from the inferred type
2567 // of the receiver, not something the user wrote. So when we
2568 // create the user-substs, we want to replace those earlier
2569 // types with just the types that the user actually wrote --
2570 // that is, those that appear on the *method itself*.
2572 // As an example, if the user wrote something like
2573 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2574 // type of `foo` (possibly adjusted), but we don't want to
2575 // include that. We want just the `[_, u32]` part.
2576 if !method.substs.is_noop() {
2577 let method_generics = self.tcx.generics_of(method.def_id);
2578 if !method_generics.params.is_empty() {
2579 let user_type_annotation = self.infcx.probe(|_| {
2580 let user_substs = UserSubsts {
2581 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2582 let i = param.index as usize;
2583 if i < method_generics.parent_count {
2584 self.infcx.var_for_def(DUMMY_SP, param)
2589 user_self_ty: None, // not relevant here
2592 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2598 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2599 self.write_user_type_annotation(hir_id, user_type_annotation);
2604 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2605 if !substs.is_noop() {
2606 debug!("write_substs({:?}, {:?}) in fcx {}",
2611 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2615 /// Given the substs that we just converted from the HIR, try to
2616 /// canonicalize them and store them as user-given substitutions
2617 /// (i.e., substitutions that must be respected by the NLL check).
2619 /// This should be invoked **before any unifications have
2620 /// occurred**, so that annotations like `Vec<_>` are preserved
2622 pub fn write_user_type_annotation_from_substs(
2626 substs: SubstsRef<'tcx>,
2627 user_self_ty: Option<UserSelfTy<'tcx>>,
2630 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2631 user_self_ty={:?} in fcx {}",
2632 hir_id, def_id, substs, user_self_ty, self.tag(),
2635 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2636 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2637 &UserType::TypeOf(def_id, UserSubsts {
2642 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2643 self.write_user_type_annotation(hir_id, canonicalized);
2647 pub fn write_user_type_annotation(
2650 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2653 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2654 hir_id, canonical_user_type_annotation, self.tag(),
2657 if !canonical_user_type_annotation.is_identity() {
2658 self.tables.borrow_mut().user_provided_types_mut().insert(
2659 hir_id, canonical_user_type_annotation
2662 debug!("write_user_type_annotation: skipping identity substs");
2666 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2667 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2673 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2674 Entry::Vacant(entry) => { entry.insert(adj); },
2675 Entry::Occupied(mut entry) => {
2676 debug!(" - composing on top of {:?}", entry.get());
2677 match (&entry.get()[..], &adj[..]) {
2678 // Applying any adjustment on top of a NeverToAny
2679 // is a valid NeverToAny adjustment, because it can't
2681 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2683 Adjustment { kind: Adjust::Deref(_), .. },
2684 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2686 Adjustment { kind: Adjust::Deref(_), .. },
2687 .. // Any following adjustments are allowed.
2689 // A reborrow has no effect before a dereference.
2691 // FIXME: currently we never try to compose autoderefs
2692 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2694 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2695 expr, entry.get(), adj)
2697 *entry.get_mut() = adj;
2702 /// Basically whenever we are converting from a type scheme into
2703 /// the fn body space, we always want to normalize associated
2704 /// types as well. This function combines the two.
2705 fn instantiate_type_scheme<T>(&self,
2707 substs: SubstsRef<'tcx>,
2710 where T : TypeFoldable<'tcx>
2712 let value = value.subst(self.tcx, substs);
2713 let result = self.normalize_associated_types_in(span, &value);
2714 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2721 /// As `instantiate_type_scheme`, but for the bounds found in a
2722 /// generic type scheme.
2723 fn instantiate_bounds(
2727 substs: SubstsRef<'tcx>,
2728 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
2729 let bounds = self.tcx.predicates_of(def_id);
2730 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
2731 let result = bounds.instantiate(self.tcx, substs);
2732 let result = self.normalize_associated_types_in(span, &result);
2734 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
2743 /// Replaces the opaque types from the given value with type variables,
2744 /// and records the `OpaqueTypeMap` for later use during writeback. See
2745 /// `InferCtxt::instantiate_opaque_types` for more details.
2746 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2748 parent_id: hir::HirId,
2752 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2753 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2757 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2758 self.instantiate_opaque_types(
2767 let mut opaque_types = self.opaque_types.borrow_mut();
2768 for (ty, decl) in opaque_type_map {
2769 let old_value = opaque_types.insert(ty, decl);
2770 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2776 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2777 where T : TypeFoldable<'tcx>
2779 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2782 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2784 where T : TypeFoldable<'tcx>
2786 self.inh.partially_normalize_associated_types_in(span,
2792 pub fn require_type_meets(&self,
2795 code: traits::ObligationCauseCode<'tcx>,
2798 self.register_bound(
2801 traits::ObligationCause::new(span, self.body_id, code));
2804 pub fn require_type_is_sized(
2808 code: traits::ObligationCauseCode<'tcx>,
2810 if !ty.references_error() {
2811 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2812 self.require_type_meets(ty, span, code, lang_item);
2816 pub fn require_type_is_sized_deferred(
2820 code: traits::ObligationCauseCode<'tcx>,
2822 if !ty.references_error() {
2823 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2827 pub fn register_bound(
2831 cause: traits::ObligationCause<'tcx>,
2833 if !ty.references_error() {
2834 self.fulfillment_cx.borrow_mut()
2835 .register_bound(self, self.param_env, ty, def_id, cause);
2839 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2840 let t = AstConv::ast_ty_to_ty(self, ast_t);
2841 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2845 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2846 let ty = self.to_ty(ast_ty);
2847 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2849 if Self::can_contain_user_lifetime_bounds(ty) {
2850 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2851 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2852 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2858 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2859 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2860 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2863 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2864 AstConv::ast_const_to_const(self, ast_c, ty)
2867 // If the type given by the user has free regions, save it for later, since
2868 // NLL would like to enforce those. Also pass in types that involve
2869 // projections, since those can resolve to `'static` bounds (modulo #54940,
2870 // which hopefully will be fixed by the time you see this comment, dear
2871 // reader, although I have my doubts). Also pass in types with inference
2872 // types, because they may be repeated. Other sorts of things are already
2873 // sufficiently enforced with erased regions. =)
2874 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2876 T: TypeFoldable<'tcx>
2878 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2881 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2882 match self.tables.borrow().node_types().get(id) {
2884 None if self.is_tainted_by_errors() => self.tcx.types.err,
2886 bug!("no type for node {}: {} in fcx {}",
2887 id, self.tcx.hir().node_to_string(id),
2893 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2894 /// outlive the region `r`.
2895 pub fn register_wf_obligation(
2899 code: traits::ObligationCauseCode<'tcx>,
2901 // WF obligations never themselves fail, so no real need to give a detailed cause:
2902 let cause = traits::ObligationCause::new(span, self.body_id, code);
2903 self.register_predicate(
2904 traits::Obligation::new(cause, self.param_env, ty::Predicate::WellFormed(ty)),
2908 /// Registers obligations that all types appearing in `substs` are well-formed.
2909 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2910 for ty in substs.types() {
2911 if !ty.references_error() {
2912 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2917 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2918 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2919 /// trait/region obligations.
2921 /// For example, if there is a function:
2924 /// fn foo<'a,T:'a>(...)
2927 /// and a reference:
2933 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2934 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2935 pub fn add_obligations_for_parameters(&self,
2936 cause: traits::ObligationCause<'tcx>,
2937 predicates: &ty::InstantiatedPredicates<'tcx>)
2939 assert!(!predicates.has_escaping_bound_vars());
2941 debug!("add_obligations_for_parameters(predicates={:?})",
2944 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2945 self.register_predicate(obligation);
2949 // FIXME(arielb1): use this instead of field.ty everywhere
2950 // Only for fields! Returns <none> for methods>
2951 // Indifferent to privacy flags
2955 field: &'tcx ty::FieldDef,
2956 substs: SubstsRef<'tcx>,
2958 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2961 fn check_casts(&self) {
2962 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2963 for cast in deferred_cast_checks.drain(..) {
2968 fn resolve_generator_interiors(&self, def_id: DefId) {
2969 let mut generators = self.deferred_generator_interiors.borrow_mut();
2970 for (body_id, interior, kind) in generators.drain(..) {
2971 self.select_obligations_where_possible(false, |_| {});
2972 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2976 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2977 // Non-numerics get replaced with ! or () (depending on whether
2978 // feature(never_type) is enabled, unconstrained ints with i32,
2979 // unconstrained floats with f64.
2980 // Fallback becomes very dubious if we have encountered type-checking errors.
2981 // In that case, fallback to Error.
2982 // The return value indicates whether fallback has occurred.
2983 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2984 use rustc::ty::error::UnconstrainedNumeric::Neither;
2985 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2987 assert!(ty.is_ty_infer());
2988 let fallback = match self.type_is_unconstrained_numeric(ty) {
2989 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2990 UnconstrainedInt => self.tcx.types.i32,
2991 UnconstrainedFloat => self.tcx.types.f64,
2992 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2993 Neither => return false,
2995 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2996 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
3000 fn select_all_obligations_or_error(&self) {
3001 debug!("select_all_obligations_or_error");
3002 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
3003 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
3007 /// Select as many obligations as we can at present.
3008 fn select_obligations_where_possible(
3010 fallback_has_occurred: bool,
3011 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
3013 if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
3014 mutate_fullfillment_errors(&mut errors);
3015 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
3019 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
3020 /// returns a type of `&T`, but the actual type we assign to the
3021 /// *expression* is `T`. So this function just peels off the return
3022 /// type by one layer to yield `T`.
3023 fn make_overloaded_place_return_type(&self,
3024 method: MethodCallee<'tcx>)
3025 -> ty::TypeAndMut<'tcx>
3027 // extract method return type, which will be &T;
3028 let ret_ty = method.sig.output();
3030 // method returns &T, but the type as visible to user is T, so deref
3031 ret_ty.builtin_deref(true).unwrap()
3037 base_expr: &'tcx hir::Expr,
3041 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3042 // FIXME(#18741) -- this is almost but not quite the same as the
3043 // autoderef that normal method probing does. They could likely be
3046 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3047 let mut result = None;
3048 while result.is_none() && autoderef.next().is_some() {
3049 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3051 autoderef.finalize(self);
3055 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3056 /// (and otherwise adjust) `base_expr`, looking for a type which either
3057 /// supports builtin indexing or overloaded indexing.
3058 /// This loop implements one step in that search; the autoderef loop
3059 /// is implemented by `lookup_indexing`.
3063 base_expr: &hir::Expr,
3064 autoderef: &Autoderef<'a, 'tcx>,
3067 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3068 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3069 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3076 for &unsize in &[false, true] {
3077 let mut self_ty = adjusted_ty;
3079 // We only unsize arrays here.
3080 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3081 self_ty = self.tcx.mk_slice(element_ty);
3087 // If some lookup succeeds, write callee into table and extract index/element
3088 // type from the method signature.
3089 // If some lookup succeeded, install method in table
3090 let input_ty = self.next_ty_var(TypeVariableOrigin {
3091 kind: TypeVariableOriginKind::AutoDeref,
3092 span: base_expr.span,
3094 let method = self.try_overloaded_place_op(
3095 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
3097 let result = method.map(|ok| {
3098 debug!("try_index_step: success, using overloaded indexing");
3099 let method = self.register_infer_ok_obligations(ok);
3101 let mut adjustments = autoderef.adjust_steps(self, needs);
3102 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3103 let mutbl = match r_mutbl {
3104 hir::MutImmutable => AutoBorrowMutability::Immutable,
3105 hir::MutMutable => AutoBorrowMutability::Mutable {
3106 // Indexing can be desugared to a method call,
3107 // so maybe we could use two-phase here.
3108 // See the documentation of AllowTwoPhase for why that's
3109 // not the case today.
3110 allow_two_phase_borrow: AllowTwoPhase::No,
3113 adjustments.push(Adjustment {
3114 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3115 target: self.tcx.mk_ref(region, ty::TypeAndMut {
3122 adjustments.push(Adjustment {
3123 kind: Adjust::Pointer(PointerCast::Unsize),
3124 target: method.sig.inputs()[0]
3127 self.apply_adjustments(base_expr, adjustments);
3129 self.write_method_call(expr.hir_id, method);
3130 (input_ty, self.make_overloaded_place_return_type(method).ty)
3132 if result.is_some() {
3140 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3141 let (tr, name) = match (op, is_mut) {
3142 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3143 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3144 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3145 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3147 (tr, ast::Ident::with_dummy_span(name))
3150 fn try_overloaded_place_op(&self,
3153 arg_tys: &[Ty<'tcx>],
3156 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3158 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3164 // Try Mut first, if needed.
3165 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3166 let method = match (needs, mut_tr) {
3167 (Needs::MutPlace, Some(trait_did)) => {
3168 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3173 // Otherwise, fall back to the immutable version.
3174 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3175 let method = match (method, imm_tr) {
3176 (None, Some(trait_did)) => {
3177 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3179 (method, _) => method,
3185 fn check_method_argument_types(
3188 expr: &'tcx hir::Expr,
3189 method: Result<MethodCallee<'tcx>, ()>,
3190 args_no_rcvr: &'tcx [hir::Expr],
3191 tuple_arguments: TupleArgumentsFlag,
3192 expected: Expectation<'tcx>,
3195 let has_error = match method {
3197 method.substs.references_error() || method.sig.references_error()
3202 let err_inputs = self.err_args(args_no_rcvr.len());
3204 let err_inputs = match tuple_arguments {
3205 DontTupleArguments => err_inputs,
3206 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3209 self.check_argument_types(
3219 return self.tcx.types.err;
3222 let method = method.unwrap();
3223 // HACK(eddyb) ignore self in the definition (see above).
3224 let expected_arg_tys = self.expected_inputs_for_expected_output(
3227 method.sig.output(),
3228 &method.sig.inputs()[1..]
3230 self.check_argument_types(
3233 &method.sig.inputs()[1..],
3234 &expected_arg_tys[..],
3236 method.sig.c_variadic,
3238 self.tcx.hir().span_if_local(method.def_id),
3243 fn self_type_matches_expected_vid(
3245 trait_ref: ty::PolyTraitRef<'tcx>,
3246 expected_vid: ty::TyVid,
3248 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3250 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3251 trait_ref, self_ty, expected_vid
3253 match self_ty.kind {
3254 ty::Infer(ty::TyVar(found_vid)) => {
3255 // FIXME: consider using `sub_root_var` here so we
3256 // can see through subtyping.
3257 let found_vid = self.root_var(found_vid);
3258 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3259 expected_vid == found_vid
3265 fn obligations_for_self_ty<'b>(
3268 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3271 // FIXME: consider using `sub_root_var` here so we
3272 // can see through subtyping.
3273 let ty_var_root = self.root_var(self_ty);
3274 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3275 self_ty, ty_var_root,
3276 self.fulfillment_cx.borrow().pending_obligations());
3280 .pending_obligations()
3282 .filter_map(move |obligation| match obligation.predicate {
3283 ty::Predicate::Projection(ref data) =>
3284 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3285 ty::Predicate::Trait(ref data) =>
3286 Some((data.to_poly_trait_ref(), obligation)),
3287 ty::Predicate::Subtype(..) => None,
3288 ty::Predicate::RegionOutlives(..) => None,
3289 ty::Predicate::TypeOutlives(..) => None,
3290 ty::Predicate::WellFormed(..) => None,
3291 ty::Predicate::ObjectSafe(..) => None,
3292 ty::Predicate::ConstEvaluatable(..) => None,
3293 // N.B., this predicate is created by breaking down a
3294 // `ClosureType: FnFoo()` predicate, where
3295 // `ClosureType` represents some `Closure`. It can't
3296 // possibly be referring to the current closure,
3297 // because we haven't produced the `Closure` for
3298 // this closure yet; this is exactly why the other
3299 // code is looking for a self type of a unresolved
3300 // inference variable.
3301 ty::Predicate::ClosureKind(..) => None,
3302 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3305 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3306 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3307 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3311 /// Generic function that factors out common logic from function calls,
3312 /// method calls and overloaded operators.
3313 fn check_argument_types(
3316 expr: &'tcx hir::Expr,
3317 fn_inputs: &[Ty<'tcx>],
3318 expected_arg_tys: &[Ty<'tcx>],
3319 args: &'tcx [hir::Expr],
3321 tuple_arguments: TupleArgumentsFlag,
3322 def_span: Option<Span>,
3325 // Grab the argument types, supplying fresh type variables
3326 // if the wrong number of arguments were supplied
3327 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3333 // All the input types from the fn signature must outlive the call
3334 // so as to validate implied bounds.
3335 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3336 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3339 let expected_arg_count = fn_inputs.len();
3341 let param_count_error = |expected_count: usize,
3346 let mut err = tcx.sess.struct_span_err_with_code(sp,
3347 &format!("this function takes {}{} but {} {} supplied",
3348 if c_variadic { "at least " } else { "" },
3349 potentially_plural_count(expected_count, "parameter"),
3350 potentially_plural_count(arg_count, "parameter"),
3351 if arg_count == 1 {"was"} else {"were"}),
3352 DiagnosticId::Error(error_code.to_owned()));
3354 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3355 err.span_label(def_s, "defined here");
3358 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3359 // remove closing `)` from the span
3360 let sugg_span = sugg_span.shrink_to_lo();
3361 err.span_suggestion(
3363 "expected the unit value `()`; create it with empty parentheses",
3365 Applicability::MachineApplicable);
3367 err.span_label(sp, format!("expected {}{}",
3368 if c_variadic { "at least " } else { "" },
3369 potentially_plural_count(expected_count, "parameter")));
3374 let mut expected_arg_tys = expected_arg_tys.to_vec();
3376 let formal_tys = if tuple_arguments == TupleArguments {
3377 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3378 match tuple_type.kind {
3379 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3380 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3381 expected_arg_tys = vec![];
3382 self.err_args(args.len())
3384 ty::Tuple(arg_types) => {
3385 expected_arg_tys = match expected_arg_tys.get(0) {
3386 Some(&ty) => match ty.kind {
3387 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3392 arg_types.iter().map(|k| k.expect_ty()).collect()
3395 span_err!(tcx.sess, sp, E0059,
3396 "cannot use call notation; the first type parameter \
3397 for the function trait is neither a tuple nor unit");
3398 expected_arg_tys = vec![];
3399 self.err_args(args.len())
3402 } else if expected_arg_count == supplied_arg_count {
3404 } else if c_variadic {
3405 if supplied_arg_count >= expected_arg_count {
3408 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3409 expected_arg_tys = vec![];
3410 self.err_args(supplied_arg_count)
3413 // is the missing argument of type `()`?
3414 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3415 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3416 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3417 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3421 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3423 expected_arg_tys = vec![];
3424 self.err_args(supplied_arg_count)
3427 debug!("check_argument_types: formal_tys={:?}",
3428 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3430 // If there is no expectation, expect formal_tys.
3431 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3437 let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
3439 // Check the arguments.
3440 // We do this in a pretty awful way: first we type-check any arguments
3441 // that are not closures, then we type-check the closures. This is so
3442 // that we have more information about the types of arguments when we
3443 // type-check the functions. This isn't really the right way to do this.
3444 for &check_closures in &[false, true] {
3445 debug!("check_closures={}", check_closures);
3447 // More awful hacks: before we check argument types, try to do
3448 // an "opportunistic" vtable resolution of any trait bounds on
3449 // the call. This helps coercions.
3451 self.select_obligations_where_possible(false, |errors| {
3452 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
3453 self.point_at_arg_instead_of_call_if_possible(
3455 &final_arg_types[..],
3462 // For C-variadic functions, we don't have a declared type for all of
3463 // the arguments hence we only do our usual type checking with
3464 // the arguments who's types we do know.
3465 let t = if c_variadic {
3467 } else if tuple_arguments == TupleArguments {
3472 for (i, arg) in args.iter().take(t).enumerate() {
3473 // Warn only for the first loop (the "no closures" one).
3474 // Closure arguments themselves can't be diverging, but
3475 // a previous argument can, e.g., `foo(panic!(), || {})`.
3476 if !check_closures {
3477 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3480 let is_closure = match arg.kind {
3481 ExprKind::Closure(..) => true,
3485 if is_closure != check_closures {
3489 debug!("checking the argument");
3490 let formal_ty = formal_tys[i];
3492 // The special-cased logic below has three functions:
3493 // 1. Provide as good of an expected type as possible.
3494 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3496 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3498 // 2. Coerce to the most detailed type that could be coerced
3499 // to, which is `expected_ty` if `rvalue_hint` returns an
3500 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3501 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3502 // We're processing function arguments so we definitely want to use
3503 // two-phase borrows.
3504 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3505 final_arg_types.push((i, coerce_ty));
3507 // 3. Relate the expected type and the formal one,
3508 // if the expected type was used for the coercion.
3509 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3513 // We also need to make sure we at least write the ty of the other
3514 // arguments which we skipped above.
3516 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3517 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3518 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3521 for arg in args.iter().skip(expected_arg_count) {
3522 let arg_ty = self.check_expr(&arg);
3524 // There are a few types which get autopromoted when passed via varargs
3525 // in C but we just error out instead and require explicit casts.
3526 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3528 ty::Float(ast::FloatTy::F32) => {
3529 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3531 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3532 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3534 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3535 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3538 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3539 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3540 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3548 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3549 vec![self.tcx.types.err; len]
3552 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
3553 /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
3554 /// reference a type argument. If they do, and there's only *one* argument that does, we point
3555 /// at the corresponding argument's expression span instead of the `fn` call path span.
3556 fn point_at_arg_instead_of_call_if_possible(
3558 errors: &mut Vec<traits::FulfillmentError<'_>>,
3559 final_arg_types: &[(usize, Ty<'tcx>)],
3561 args: &'tcx [hir::Expr],
3563 if !call_sp.desugaring_kind().is_some() {
3564 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3565 // the `?` operator.
3566 for error in errors {
3567 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3568 // Collect the argument position for all arguments that could have caused this
3569 // `FullfillmentError`.
3570 let mut referenced_in = final_arg_types.iter()
3571 .flat_map(|(i, ty)| {
3572 let ty = self.resolve_vars_if_possible(ty);
3573 // We walk the argument type because the argument's type could have
3574 // been `Option<T>`, but the `FullfillmentError` references `T`.
3576 .filter(|&ty| ty == predicate.skip_binder().self_ty())
3579 if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
3580 // We make sure that only *one* argument matches the obligation failure
3581 // and thet the obligation's span to its expression's.
3582 error.obligation.cause.span = args[ref_in].span;
3583 error.points_at_arg_span = true;
3590 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call expression, we walk the
3591 /// `PathSegment`s and resolve their type parameters to see if any of the `FullfillmentError`s
3592 /// were caused by them. If they were, we point at the corresponding type argument's span
3593 /// instead of the `fn` call path span.
3594 fn point_at_type_arg_instead_of_call_if_possible(
3596 errors: &mut Vec<traits::FulfillmentError<'_>>,
3597 call_expr: &'tcx hir::Expr,
3599 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
3600 if let hir::ExprKind::Path(qpath) = &path.kind {
3601 if let hir::QPath::Resolved(_, path) = &qpath {
3602 for error in errors {
3603 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3604 // If any of the type arguments in this path segment caused the
3605 // `FullfillmentError`, point at its span (#61860).
3606 for arg in path.segments.iter()
3607 .filter_map(|seg| seg.args.as_ref())
3608 .flat_map(|a| a.args.iter())
3610 if let hir::GenericArg::Type(hir_ty) = &arg {
3611 if let hir::TyKind::Path(
3612 hir::QPath::TypeRelative(..),
3614 // Avoid ICE with associated types. As this is best
3615 // effort only, it's ok to ignore the case. It
3616 // would trigger in `is_send::<T::AssocType>();`
3617 // from `typeck-default-trait-impl-assoc-type.rs`.
3619 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
3620 let ty = self.resolve_vars_if_possible(&ty);
3621 if ty == predicate.skip_binder().self_ty() {
3622 error.obligation.cause.span = hir_ty.span;
3634 // AST fragment checking
3637 expected: Expectation<'tcx>)
3643 ast::LitKind::Str(..) => tcx.mk_static_str(),
3644 ast::LitKind::ByteStr(ref v) => {
3645 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3646 tcx.mk_array(tcx.types.u8, v.len() as u64))
3648 ast::LitKind::Byte(_) => tcx.types.u8,
3649 ast::LitKind::Char(_) => tcx.types.char,
3650 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3651 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3652 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3653 let opt_ty = expected.to_option(self).and_then(|ty| {
3655 ty::Int(_) | ty::Uint(_) => Some(ty),
3656 ty::Char => Some(tcx.types.u8),
3657 ty::RawPtr(..) => Some(tcx.types.usize),
3658 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3662 opt_ty.unwrap_or_else(|| self.next_int_var())
3664 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3665 ast::LitKind::FloatUnsuffixed(_) => {
3666 let opt_ty = expected.to_option(self).and_then(|ty| {
3668 ty::Float(_) => Some(ty),
3672 opt_ty.unwrap_or_else(|| self.next_float_var())
3674 ast::LitKind::Bool(_) => tcx.types.bool,
3675 ast::LitKind::Err(_) => tcx.types.err,
3679 // Determine the `Self` type, using fresh variables for all variables
3680 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3681 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3683 pub fn impl_self_ty(&self,
3684 span: Span, // (potential) receiver for this impl
3686 -> TypeAndSubsts<'tcx> {
3687 let ity = self.tcx.type_of(did);
3688 debug!("impl_self_ty: ity={:?}", ity);
3690 let substs = self.fresh_substs_for_item(span, did);
3691 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3693 TypeAndSubsts { substs: substs, ty: substd_ty }
3696 /// Unifies the output type with the expected type early, for more coercions
3697 /// and forward type information on the input expressions.
3698 fn expected_inputs_for_expected_output(&self,
3700 expected_ret: Expectation<'tcx>,
3701 formal_ret: Ty<'tcx>,
3702 formal_args: &[Ty<'tcx>])
3704 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3705 let ret_ty = match expected_ret.only_has_type(self) {
3707 None => return Vec::new()
3709 let expect_args = self.fudge_inference_if_ok(|| {
3710 // Attempt to apply a subtyping relationship between the formal
3711 // return type (likely containing type variables if the function
3712 // is polymorphic) and the expected return type.
3713 // No argument expectations are produced if unification fails.
3714 let origin = self.misc(call_span);
3715 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3717 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3718 // to identity so the resulting type is not constrained.
3721 // Process any obligations locally as much as
3722 // we can. We don't care if some things turn
3723 // out unconstrained or ambiguous, as we're
3724 // just trying to get hints here.
3725 self.save_and_restore_in_snapshot_flag(|_| {
3726 let mut fulfill = TraitEngine::new(self.tcx);
3727 for obligation in ok.obligations {
3728 fulfill.register_predicate_obligation(self, obligation);
3730 fulfill.select_where_possible(self)
3731 }).map_err(|_| ())?;
3733 Err(_) => return Err(()),
3736 // Record all the argument types, with the substitutions
3737 // produced from the above subtyping unification.
3738 Ok(formal_args.iter().map(|ty| {
3739 self.resolve_vars_if_possible(ty)
3741 }).unwrap_or_default();
3742 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3743 formal_args, formal_ret,
3744 expect_args, expected_ret);
3748 pub fn check_struct_path(&self,
3751 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3752 let path_span = match *qpath {
3753 QPath::Resolved(_, ref path) => path.span,
3754 QPath::TypeRelative(ref qself, _) => qself.span
3756 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3757 let variant = match def {
3759 self.set_tainted_by_errors();
3762 Res::Def(DefKind::Variant, _) => {
3764 ty::Adt(adt, substs) => {
3765 Some((adt.variant_of_res(def), adt.did, substs))
3767 _ => bug!("unexpected type: {:?}", ty)
3770 Res::Def(DefKind::Struct, _)
3771 | Res::Def(DefKind::Union, _)
3772 | Res::Def(DefKind::TyAlias, _)
3773 | Res::Def(DefKind::AssocTy, _)
3774 | Res::SelfTy(..) => {
3776 ty::Adt(adt, substs) if !adt.is_enum() => {
3777 Some((adt.non_enum_variant(), adt.did, substs))
3782 _ => bug!("unexpected definition: {:?}", def)
3785 if let Some((variant, did, substs)) = variant {
3786 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3787 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3789 // Check bounds on type arguments used in the path.
3790 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
3791 let cause = traits::ObligationCause::new(
3794 traits::ItemObligation(did),
3796 self.add_obligations_for_parameters(cause, &bounds);
3800 struct_span_err!(self.tcx.sess, path_span, E0071,
3801 "expected struct, variant or union type, found {}",
3802 ty.sort_string(self.tcx))
3803 .span_label(path_span, "not a struct")
3809 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3810 // The newly resolved definition is written into `type_dependent_defs`.
3811 fn finish_resolving_struct_path(&self,
3818 QPath::Resolved(ref maybe_qself, ref path) => {
3819 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3820 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3823 QPath::TypeRelative(ref qself, ref segment) => {
3824 let ty = self.to_ty(qself);
3826 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
3831 let result = AstConv::associated_path_to_ty(
3840 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3841 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3843 // Write back the new resolution.
3844 self.write_resolution(hir_id, result);
3846 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3851 /// Resolves an associated value path into a base type and associated constant, or method
3852 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3853 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3857 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3859 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3860 let (ty, qself, item_segment) = match *qpath {
3861 QPath::Resolved(ref opt_qself, ref path) => {
3863 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3864 &path.segments[..]);
3866 QPath::TypeRelative(ref qself, ref segment) => {
3867 (self.to_ty(qself), qself, segment)
3870 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3871 // Return directly on cache hit. This is useful to avoid doubly reporting
3872 // errors with default match binding modes. See #44614.
3873 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3874 .unwrap_or(Res::Err);
3875 return (def, Some(ty), slice::from_ref(&**item_segment));
3877 let item_name = item_segment.ident;
3878 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3879 let result = match error {
3880 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3881 _ => Err(ErrorReported),
3883 if item_name.name != kw::Invalid {
3884 self.report_method_error(
3888 SelfSource::QPath(qself),
3891 ).map(|mut e| e.emit());
3896 // Write back the new resolution.
3897 self.write_resolution(hir_id, result);
3899 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3901 slice::from_ref(&**item_segment),
3905 pub fn check_decl_initializer(
3907 local: &'tcx hir::Local,
3908 init: &'tcx hir::Expr,
3910 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3911 // for #42640 (default match binding modes).
3914 let ref_bindings = local.pat.contains_explicit_ref_binding();
3916 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3917 if let Some(m) = ref_bindings {
3918 // Somewhat subtle: if we have a `ref` binding in the pattern,
3919 // we want to avoid introducing coercions for the RHS. This is
3920 // both because it helps preserve sanity and, in the case of
3921 // ref mut, for soundness (issue #23116). In particular, in
3922 // the latter case, we need to be clear that the type of the
3923 // referent for the reference that results is *equal to* the
3924 // type of the place it is referencing, and not some
3925 // supertype thereof.
3926 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3927 self.demand_eqtype(init.span, local_ty, init_ty);
3930 self.check_expr_coercable_to_type(init, local_ty)
3934 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3935 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3936 self.write_ty(local.hir_id, t);
3938 if let Some(ref init) = local.init {
3939 let init_ty = self.check_decl_initializer(local, &init);
3940 self.overwrite_local_ty_if_err(local, t, init_ty);
3943 self.check_pat_top(&local.pat, t, None);
3944 let pat_ty = self.node_ty(local.pat.hir_id);
3945 self.overwrite_local_ty_if_err(local, t, pat_ty);
3948 fn overwrite_local_ty_if_err(&self, local: &'tcx hir::Local, decl_ty: Ty<'tcx>, ty: Ty<'tcx>) {
3949 if ty.references_error() {
3950 // Override the types everywhere with `types.err` to avoid knock down errors.
3951 self.write_ty(local.hir_id, ty);
3952 self.write_ty(local.pat.hir_id, ty);
3953 let local_ty = LocalTy {
3957 self.locals.borrow_mut().insert(local.hir_id, local_ty);
3958 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
3962 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
3963 err.span_suggestion_short(
3964 span.shrink_to_hi(),
3965 "consider using a semicolon here",
3967 Applicability::MachineApplicable,
3971 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3972 // Don't do all the complex logic below for `DeclItem`.
3974 hir::StmtKind::Item(..) => return,
3975 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3978 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3980 // Hide the outer diverging and `has_errors` flags.
3981 let old_diverges = self.diverges.get();
3982 let old_has_errors = self.has_errors.get();
3983 self.diverges.set(Diverges::Maybe);
3984 self.has_errors.set(false);
3987 hir::StmtKind::Local(ref l) => {
3988 self.check_decl_local(&l);
3991 hir::StmtKind::Item(_) => {}
3992 hir::StmtKind::Expr(ref expr) => {
3993 // Check with expected type of `()`.
3995 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
3996 self.suggest_semicolon_at_end(expr.span, err);
3999 hir::StmtKind::Semi(ref expr) => {
4000 self.check_expr(&expr);
4004 // Combine the diverging and `has_error` flags.
4005 self.diverges.set(self.diverges.get() | old_diverges);
4006 self.has_errors.set(self.has_errors.get() | old_has_errors);
4009 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
4010 let unit = self.tcx.mk_unit();
4011 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4013 // if the block produces a `!` value, that can always be
4014 // (effectively) coerced to unit.
4016 self.demand_suptype(blk.span, unit, ty);
4020 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
4021 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
4022 /// when given code like the following:
4024 /// if false { return 0i32; } else { 1u32 }
4025 /// // ^^^^ point at this instead of the whole `if` expression
4027 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
4028 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
4029 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
4030 self.in_progress_tables
4031 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
4032 .and_then(|arm_ty| {
4033 if arm_ty.is_never() {
4036 Some(match &arm.body.kind {
4037 // Point at the tail expression when possible.
4038 hir::ExprKind::Block(block, _) => block.expr
4041 .unwrap_or(block.span),
4047 if arm_spans.len() == 1 {
4048 return arm_spans[0];
4054 fn check_block_with_expected(
4056 blk: &'tcx hir::Block,
4057 expected: Expectation<'tcx>,
4060 let mut fcx_ps = self.ps.borrow_mut();
4061 let unsafety_state = fcx_ps.recurse(blk);
4062 replace(&mut *fcx_ps, unsafety_state)
4065 // In some cases, blocks have just one exit, but other blocks
4066 // can be targeted by multiple breaks. This can happen both
4067 // with labeled blocks as well as when we desugar
4068 // a `try { ... }` expression.
4072 // 'a: { if true { break 'a Err(()); } Ok(()) }
4074 // Here we would wind up with two coercions, one from
4075 // `Err(())` and the other from the tail expression
4076 // `Ok(())`. If the tail expression is omitted, that's a
4077 // "forced unit" -- unless the block diverges, in which
4078 // case we can ignore the tail expression (e.g., `'a: {
4079 // break 'a 22; }` would not force the type of the block
4081 let tail_expr = blk.expr.as_ref();
4082 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4083 let coerce = if blk.targeted_by_break {
4084 CoerceMany::new(coerce_to_ty)
4086 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4087 Some(e) => slice::from_ref(e),
4090 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4093 let prev_diverges = self.diverges.get();
4094 let ctxt = BreakableCtxt {
4095 coerce: Some(coerce),
4099 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4100 for s in &blk.stmts {
4104 // check the tail expression **without** holding the
4105 // `enclosing_breakables` lock below.
4106 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4108 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4109 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4110 let coerce = ctxt.coerce.as_mut().unwrap();
4111 if let Some(tail_expr_ty) = tail_expr_ty {
4112 let tail_expr = tail_expr.unwrap();
4113 let span = self.get_expr_coercion_span(tail_expr);
4114 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4115 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4117 // Subtle: if there is no explicit tail expression,
4118 // that is typically equivalent to a tail expression
4119 // of `()` -- except if the block diverges. In that
4120 // case, there is no value supplied from the tail
4121 // expression (assuming there are no other breaks,
4122 // this implies that the type of the block will be
4125 // #41425 -- label the implicit `()` as being the
4126 // "found type" here, rather than the "expected type".
4127 if !self.diverges.get().is_always() {
4128 // #50009 -- Do not point at the entire fn block span, point at the return type
4129 // span, as it is the cause of the requirement, and
4130 // `consider_hint_about_removing_semicolon` will point at the last expression
4131 // if it were a relevant part of the error. This improves usability in editors
4132 // that highlight errors inline.
4133 let mut sp = blk.span;
4134 let mut fn_span = None;
4135 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4136 let ret_sp = decl.output.span();
4137 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4138 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4139 // output would otherwise be incorrect and even misleading. Make sure
4140 // the span we're aiming at correspond to a `fn` body.
4141 if block_sp == blk.span {
4143 fn_span = Some(ident.span);
4147 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4148 if let Some(expected_ty) = expected.only_has_type(self) {
4149 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4151 if let Some(fn_span) = fn_span {
4154 "implicitly returns `()` as its body has no tail or `return` \
4164 // If we can break from the block, then the block's exit is always reachable
4165 // (... as long as the entry is reachable) - regardless of the tail of the block.
4166 self.diverges.set(prev_diverges);
4169 let mut ty = ctxt.coerce.unwrap().complete(self);
4171 if self.has_errors.get() || ty.references_error() {
4172 ty = self.tcx.types.err
4175 self.write_ty(blk.hir_id, ty);
4177 *self.ps.borrow_mut() = prev;
4181 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4182 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4184 Node::Item(&hir::Item {
4185 kind: hir::ItemKind::Fn(_, _, _, body_id), ..
4187 Node::ImplItem(&hir::ImplItem {
4188 kind: hir::ImplItemKind::Method(_, body_id), ..
4190 let body = self.tcx.hir().body(body_id);
4191 if let ExprKind::Block(block, _) = &body.value.kind {
4192 return Some(block.span);
4200 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4201 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
4202 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4203 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4206 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4207 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
4209 Node::Item(&hir::Item {
4210 ident, kind: hir::ItemKind::Fn(ref decl, ..), ..
4212 // This is less than ideal, it will not suggest a return type span on any
4213 // method called `main`, regardless of whether it is actually the entry point,
4214 // but it will still present it as the reason for the expected type.
4215 Some((decl, ident, ident.name != sym::main))
4217 Node::TraitItem(&hir::TraitItem {
4218 ident, kind: hir::TraitItemKind::Method(hir::MethodSig {
4221 }) => Some((decl, ident, true)),
4222 Node::ImplItem(&hir::ImplItem {
4223 ident, kind: hir::ImplItemKind::Method(hir::MethodSig {
4226 }) => Some((decl, ident, false)),
4231 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4232 /// suggestion can be made, `None` otherwise.
4233 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
4234 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4235 // `while` before reaching it, as block tail returns are not available in them.
4236 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4237 let parent = self.tcx.hir().get(blk_id);
4238 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4242 /// On implicit return expressions with mismatched types, provides the following suggestions:
4244 /// - Points out the method's return type as the reason for the expected type.
4245 /// - Possible missing semicolon.
4246 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4247 pub fn suggest_mismatched_types_on_tail(
4249 err: &mut DiagnosticBuilder<'tcx>,
4250 expr: &'tcx hir::Expr,
4256 let expr = expr.peel_drop_temps();
4257 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4258 let mut pointing_at_return_type = false;
4259 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4260 pointing_at_return_type = self.suggest_missing_return_type(
4261 err, &fn_decl, expected, found, can_suggest);
4263 self.suggest_ref_or_into(err, expr, expected, found);
4264 self.suggest_boxing_when_appropriate(err, expr, expected, found);
4265 pointing_at_return_type
4268 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4269 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4271 /// fn foo(x: usize) -> usize { x }
4272 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4276 err: &mut DiagnosticBuilder<'tcx>,
4281 let hir = self.tcx.hir();
4282 let (def_id, sig) = match found.kind {
4283 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4284 ty::Closure(def_id, substs) => {
4285 // We don't use `closure_sig` to account for malformed closures like
4286 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4287 let closure_sig_ty = substs.as_closure().sig_ty(def_id, self.tcx);
4288 (def_id, match closure_sig_ty.kind {
4289 ty::FnPtr(sig) => sig,
4297 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4299 let sig = self.normalize_associated_types_in(expr.span, &sig);
4300 if self.can_coerce(sig.output(), expected) {
4301 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4302 (String::new(), Applicability::MachineApplicable)
4304 ("...".to_string(), Applicability::HasPlaceholders)
4306 let mut msg = "call this function";
4307 match hir.get_if_local(def_id) {
4308 Some(Node::Item(hir::Item {
4309 kind: ItemKind::Fn(.., body_id),
4312 Some(Node::ImplItem(hir::ImplItem {
4313 kind: hir::ImplItemKind::Method(_, body_id),
4316 Some(Node::TraitItem(hir::TraitItem {
4317 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4320 let body = hir.body(*body_id);
4321 sugg_call = body.params.iter()
4322 .map(|param| match ¶m.pat.kind {
4323 hir::PatKind::Binding(_, _, ident, None)
4324 if ident.name != kw::SelfLower => ident.to_string(),
4325 _ => "_".to_string(),
4326 }).collect::<Vec<_>>().join(", ");
4328 Some(Node::Expr(hir::Expr {
4329 kind: ExprKind::Closure(_, _, body_id, closure_span, _),
4330 span: full_closure_span,
4333 if *full_closure_span == expr.span {
4336 err.span_label(*closure_span, "closure defined here");
4337 msg = "call this closure";
4338 let body = hir.body(*body_id);
4339 sugg_call = body.params.iter()
4340 .map(|param| match ¶m.pat.kind {
4341 hir::PatKind::Binding(_, _, ident, None)
4342 if ident.name != kw::SelfLower => ident.to_string(),
4343 _ => "_".to_string(),
4344 }).collect::<Vec<_>>().join(", ");
4346 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4347 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4348 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4349 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4350 msg = "instantiate this tuple variant";
4352 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4353 msg = "instantiate this tuple struct";
4358 Some(Node::ForeignItem(hir::ForeignItem {
4359 kind: hir::ForeignItemKind::Fn(_, idents, _),
4362 Some(Node::TraitItem(hir::TraitItem {
4363 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4365 })) => sugg_call = idents.iter()
4366 .map(|ident| if ident.name != kw::SelfLower {
4370 }).collect::<Vec<_>>()
4374 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4375 err.span_suggestion(
4377 &format!("use parentheses to {}", msg),
4378 format!("{}({})", code, sugg_call),
4387 pub fn suggest_ref_or_into(
4389 err: &mut DiagnosticBuilder<'tcx>,
4394 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4395 err.span_suggestion(
4399 Applicability::MachineApplicable,
4401 } else if let (ty::FnDef(def_id, ..), true) = (
4403 self.suggest_fn_call(err, expr, expected, found),
4405 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4406 let sp = self.sess().source_map().def_span(sp);
4407 err.span_label(sp, &format!("{} defined here", found));
4409 } else if !self.check_for_cast(err, expr, found, expected) {
4410 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4414 let methods = self.get_conversion_methods(expr.span, expected, found);
4415 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4416 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4417 .filter_map(|(receiver, method)| {
4418 let method_call = format!(".{}()", method.ident);
4419 if receiver.ends_with(&method_call) {
4420 None // do not suggest code that is already there (#53348)
4422 let method_call_list = [".to_vec()", ".to_string()"];
4423 let sugg = if receiver.ends_with(".clone()")
4424 && method_call_list.contains(&method_call.as_str()) {
4425 let max_len = receiver.rfind(".").unwrap();
4426 format!("{}{}", &receiver[..max_len], method_call)
4428 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
4429 format!("({}){}", receiver, method_call)
4431 format!("{}{}", receiver, method_call)
4434 Some(if is_struct_pat_shorthand_field {
4435 format!("{}: {}", receiver, sugg)
4441 if suggestions.peek().is_some() {
4442 err.span_suggestions(
4444 "try using a conversion method",
4446 Applicability::MaybeIncorrect,
4453 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4454 /// in the heap by calling `Box::new()`.
4455 fn suggest_boxing_when_appropriate(
4457 err: &mut DiagnosticBuilder<'tcx>,
4462 if self.tcx.hir().is_const_context(expr.hir_id) {
4463 // Do not suggest `Box::new` in const context.
4466 if !expected.is_box() || found.is_box() {
4469 let boxed_found = self.tcx.mk_box(found);
4470 if let (true, Ok(snippet)) = (
4471 self.can_coerce(boxed_found, expected),
4472 self.sess().source_map().span_to_snippet(expr.span),
4474 err.span_suggestion(
4476 "store this in the heap by calling `Box::new`",
4477 format!("Box::new({})", snippet),
4478 Applicability::MachineApplicable,
4480 err.note("for more on the distinction between the stack and the \
4481 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4482 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4483 https://doc.rust-lang.org/std/boxed/index.html");
4488 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4492 /// bar_that_returns_u32()
4496 /// This routine checks if the return expression in a block would make sense on its own as a
4497 /// statement and the return type has been left as default or has been specified as `()`. If so,
4498 /// it suggests adding a semicolon.
4499 fn suggest_missing_semicolon(
4501 err: &mut DiagnosticBuilder<'tcx>,
4502 expression: &'tcx hir::Expr,
4506 if expected.is_unit() {
4507 // `BlockTailExpression` only relevant if the tail expr would be
4508 // useful on its own.
4509 match expression.kind {
4510 ExprKind::Call(..) |
4511 ExprKind::MethodCall(..) |
4512 ExprKind::Loop(..) |
4513 ExprKind::Match(..) |
4514 ExprKind::Block(..) => {
4515 let sp = self.tcx.sess.source_map().next_point(cause_span);
4516 err.span_suggestion(
4518 "try adding a semicolon",
4520 Applicability::MachineApplicable);
4527 /// A possible error is to forget to add a return type that is needed:
4531 /// bar_that_returns_u32()
4535 /// This routine checks if the return type is left as default, the method is not part of an
4536 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4538 fn suggest_missing_return_type(
4540 err: &mut DiagnosticBuilder<'tcx>,
4541 fn_decl: &hir::FnDecl,
4546 // Only suggest changing the return type for methods that
4547 // haven't set a return type at all (and aren't `fn main()` or an impl).
4548 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4549 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4550 err.span_suggestion(
4552 "try adding a return type",
4553 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
4554 Applicability::MachineApplicable);
4557 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4558 err.span_label(span, "possibly return type missing here?");
4561 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4562 // `fn main()` must return `()`, do not suggest changing return type
4563 err.span_label(span, "expected `()` because of default return type");
4566 // expectation was caused by something else, not the default return
4567 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4568 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4569 // Only point to return type if the expected type is the return type, as if they
4570 // are not, the expectation must have been caused by something else.
4571 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
4573 let ty = AstConv::ast_ty_to_ty(self, ty);
4574 debug!("suggest_missing_return_type: return type {:?}", ty);
4575 debug!("suggest_missing_return_type: expected type {:?}", ty);
4576 if ty.kind == expected.kind {
4577 err.span_label(sp, format!("expected `{}` because of return type",
4586 /// A possible error is to forget to add `.await` when using futures:
4589 /// async fn make_u32() -> u32 {
4593 /// fn take_u32(x: u32) {}
4595 /// async fn foo() {
4596 /// let x = make_u32();
4601 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4602 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4603 /// `.await` to the tail of the expression.
4604 fn suggest_missing_await(
4606 err: &mut DiagnosticBuilder<'tcx>,
4611 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4612 // body isn't `async`.
4613 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4614 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4615 let body = self.tcx().hir().body(body_id);
4616 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
4618 // Check for `Future` implementations by constructing a predicate to
4619 // prove: `<T as Future>::Output == U`
4620 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4621 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4622 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4623 // `<T as Future>::Output`
4624 projection_ty: ty::ProjectionTy {
4626 substs: self.tcx.mk_substs_trait(
4628 self.fresh_substs_for_item(sp, item_def_id)
4635 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4636 if self.infcx.predicate_may_hold(&obligation) {
4637 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4638 err.span_suggestion(
4640 "consider using `.await` here",
4641 format!("{}.await", code),
4642 Applicability::MaybeIncorrect,
4650 /// A common error is to add an extra semicolon:
4653 /// fn foo() -> usize {
4658 /// This routine checks if the final statement in a block is an
4659 /// expression with an explicit semicolon whose type is compatible
4660 /// with `expected_ty`. If so, it suggests removing the semicolon.
4661 fn consider_hint_about_removing_semicolon(
4663 blk: &'tcx hir::Block,
4664 expected_ty: Ty<'tcx>,
4665 err: &mut DiagnosticBuilder<'_>,
4667 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4668 err.span_suggestion(
4670 "consider removing this semicolon",
4672 Applicability::MachineApplicable,
4677 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4678 // Be helpful when the user wrote `{... expr;}` and
4679 // taking the `;` off is enough to fix the error.
4680 let last_stmt = blk.stmts.last()?;
4681 let last_expr = match last_stmt.kind {
4682 hir::StmtKind::Semi(ref e) => e,
4685 let last_expr_ty = self.node_ty(last_expr.hir_id);
4686 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4689 let original_span = original_sp(last_stmt.span, blk.span);
4690 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4693 // Instantiates the given path, which must refer to an item with the given
4694 // number of type parameters and type.
4695 pub fn instantiate_value_path(&self,
4696 segments: &[hir::PathSegment],
4697 self_ty: Option<Ty<'tcx>>,
4701 -> (Ty<'tcx>, Res) {
4703 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4712 let path_segs = match res {
4713 Res::Local(_) | Res::SelfCtor(_) => vec![],
4714 Res::Def(kind, def_id) =>
4715 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4716 _ => bug!("instantiate_value_path on {:?}", res),
4719 let mut user_self_ty = None;
4720 let mut is_alias_variant_ctor = false;
4722 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4723 if let Some(self_ty) = self_ty {
4724 let adt_def = self_ty.ty_adt_def().unwrap();
4725 user_self_ty = Some(UserSelfTy {
4726 impl_def_id: adt_def.did,
4729 is_alias_variant_ctor = true;
4732 Res::Def(DefKind::Method, def_id)
4733 | Res::Def(DefKind::AssocConst, def_id) => {
4734 let container = tcx.associated_item(def_id).container;
4735 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4737 ty::TraitContainer(trait_did) => {
4738 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4740 ty::ImplContainer(impl_def_id) => {
4741 if segments.len() == 1 {
4742 // `<T>::assoc` will end up here, and so
4743 // can `T::assoc`. It this came from an
4744 // inherent impl, we need to record the
4745 // `T` for posterity (see `UserSelfTy` for
4747 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4748 user_self_ty = Some(UserSelfTy {
4759 // Now that we have categorized what space the parameters for each
4760 // segment belong to, let's sort out the parameters that the user
4761 // provided (if any) into their appropriate spaces. We'll also report
4762 // errors if type parameters are provided in an inappropriate place.
4764 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4765 let generics_has_err = AstConv::prohibit_generics(
4766 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4767 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4774 if let Res::Local(hid) = res {
4775 let ty = self.local_ty(span, hid).decl_ty;
4776 let ty = self.normalize_associated_types_in(span, &ty);
4777 self.write_ty(hir_id, ty);
4781 if generics_has_err {
4782 // Don't try to infer type parameters when prohibited generic arguments were given.
4783 user_self_ty = None;
4786 // Now we have to compare the types that the user *actually*
4787 // provided against the types that were *expected*. If the user
4788 // did not provide any types, then we want to substitute inference
4789 // variables. If the user provided some types, we may still need
4790 // to add defaults. If the user provided *too many* types, that's
4793 let mut infer_args_for_err = FxHashSet::default();
4794 for &PathSeg(def_id, index) in &path_segs {
4795 let seg = &segments[index];
4796 let generics = tcx.generics_of(def_id);
4797 // Argument-position `impl Trait` is treated as a normal generic
4798 // parameter internally, but we don't allow users to specify the
4799 // parameter's value explicitly, so we have to do some error-
4801 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4806 false, // `is_method_call`
4808 if suppress_errors {
4809 infer_args_for_err.insert(index);
4810 self.set_tainted_by_errors(); // See issue #53251.
4814 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4815 tcx.generics_of(*def_id).has_self
4816 }).unwrap_or(false);
4818 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4819 let ty = self.impl_self_ty(span, impl_def_id).ty;
4820 let adt_def = ty.ty_adt_def();
4823 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4824 let variant = adt_def.non_enum_variant();
4825 let ctor_def_id = variant.ctor_def_id.unwrap();
4827 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4832 let mut err = tcx.sess.struct_span_err(span,
4833 "the `Self` constructor can only be used with tuple or unit structs");
4834 if let Some(adt_def) = adt_def {
4835 match adt_def.adt_kind() {
4837 err.help("did you mean to use one of the enum's variants?");
4841 err.span_suggestion(
4843 "use curly brackets",
4844 String::from("Self { /* fields */ }"),
4845 Applicability::HasPlaceholders,
4852 return (tcx.types.err, res)
4858 let def_id = res.def_id();
4860 // The things we are substituting into the type should not contain
4861 // escaping late-bound regions, and nor should the base type scheme.
4862 let ty = tcx.type_of(def_id);
4864 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4870 // Provide the generic args, and whether types should be inferred.
4872 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4875 // If we've encountered an `impl Trait`-related error, we're just
4876 // going to infer the arguments for better error messages.
4877 if !infer_args_for_err.contains(&index) {
4878 // Check whether the user has provided generic arguments.
4879 if let Some(ref data) = segments[index].args {
4880 return (Some(data), segments[index].infer_args);
4883 return (None, segments[index].infer_args);
4888 // Provide substitutions for parameters for which (valid) arguments have been provided.
4890 match (¶m.kind, arg) {
4891 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4892 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4894 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4895 self.to_ty(ty).into()
4897 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4898 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4900 _ => unreachable!(),
4903 // Provide substitutions for parameters for which arguments are inferred.
4904 |substs, param, infer_args| {
4906 GenericParamDefKind::Lifetime => {
4907 self.re_infer(Some(param), span).unwrap().into()
4909 GenericParamDefKind::Type { has_default, .. } => {
4910 if !infer_args && has_default {
4911 // If we have a default, then we it doesn't matter that we're not
4912 // inferring the type arguments: we provide the default where any
4914 let default = tcx.type_of(param.def_id);
4917 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4920 // If no type arguments were provided, we have to infer them.
4921 // This case also occurs as a result of some malformed input, e.g.
4922 // a lifetime argument being given instead of a type parameter.
4923 // Using inference instead of `Error` gives better error messages.
4924 self.var_for_def(span, param)
4927 GenericParamDefKind::Const => {
4928 // FIXME(const_generics:defaults)
4929 // No const parameters were provided, we have to infer them.
4930 self.var_for_def(span, param)
4935 assert!(!substs.has_escaping_bound_vars());
4936 assert!(!ty.has_escaping_bound_vars());
4938 // First, store the "user substs" for later.
4939 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4941 self.add_required_obligations(span, def_id, &substs);
4943 // Substitute the values for the type parameters into the type of
4944 // the referenced item.
4945 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4947 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4948 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4949 // is inherent, there is no `Self` parameter; instead, the impl needs
4950 // type parameters, which we can infer by unifying the provided `Self`
4951 // with the substituted impl type.
4952 // This also occurs for an enum variant on a type alias.
4953 let ty = tcx.type_of(impl_def_id);
4955 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4956 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4957 Ok(ok) => self.register_infer_ok_obligations(ok),
4959 self.tcx.sess.delay_span_bug(span, &format!(
4960 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4968 self.check_rustc_args_require_const(def_id, hir_id, span);
4970 debug!("instantiate_value_path: type of {:?} is {:?}",
4973 self.write_substs(hir_id, substs);
4975 (ty_substituted, res)
4978 /// Add all the obligations that are required, substituting and normalized appropriately.
4979 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
4980 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
4982 for (i, mut obligation) in traits::predicates_for_generics(
4983 traits::ObligationCause::new(
4986 traits::ItemObligation(def_id),
4990 ).into_iter().enumerate() {
4991 // This makes the error point at the bound, but we want to point at the argument
4992 if let Some(span) = spans.get(i) {
4993 obligation.cause.code = traits::BindingObligation(def_id, *span);
4995 self.register_predicate(obligation);
4999 fn check_rustc_args_require_const(&self,
5003 // We're only interested in functions tagged with
5004 // #[rustc_args_required_const], so ignore anything that's not.
5005 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5009 // If our calling expression is indeed the function itself, we're good!
5010 // If not, generate an error that this can only be called directly.
5011 if let Node::Expr(expr) = self.tcx.hir().get(
5012 self.tcx.hir().get_parent_node(hir_id))
5014 if let ExprKind::Call(ref callee, ..) = expr.kind {
5015 if callee.hir_id == hir_id {
5021 self.tcx.sess.span_err(span, "this function can only be invoked \
5022 directly, not through a function pointer");
5025 // Resolves `typ` by a single level if `typ` is a type variable.
5026 // If no resolution is possible, then an error is reported.
5027 // Numeric inference variables may be left unresolved.
5028 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5029 let ty = self.resolve_type_vars_with_obligations(ty);
5030 if !ty.is_ty_var() {
5033 if !self.is_tainted_by_errors() {
5034 self.need_type_info_err((**self).body_id, sp, ty)
5035 .note("type must be known at this point")
5038 self.demand_suptype(sp, self.tcx.types.err, ty);
5043 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5046 ctxt: BreakableCtxt<'tcx>,
5048 ) -> (BreakableCtxt<'tcx>, R) {
5051 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5052 index = enclosing_breakables.stack.len();
5053 enclosing_breakables.by_id.insert(id, index);
5054 enclosing_breakables.stack.push(ctxt);
5058 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5059 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5060 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5061 enclosing_breakables.stack.pop().expect("missing breakable context")
5066 /// Instantiate a QueryResponse in a probe context, without a
5067 /// good ObligationCause.
5068 fn probe_instantiate_query_response(
5071 original_values: &OriginalQueryValues<'tcx>,
5072 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5073 ) -> InferResult<'tcx, Ty<'tcx>>
5075 self.instantiate_query_response_and_region_obligations(
5076 &traits::ObligationCause::misc(span, self.body_id),
5082 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5083 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5084 let mut contained_in_place = false;
5086 while let hir::Node::Expr(parent_expr) =
5087 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5089 match &parent_expr.kind {
5090 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5091 if lhs.hir_id == expr_id {
5092 contained_in_place = true;
5098 expr_id = parent_expr.hir_id;
5105 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5106 let own_counts = generics.own_counts();
5108 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5114 if own_counts.types == 0 {
5118 // Make a vector of booleans initially `false`; set to `true` when used.
5119 let mut types_used = vec![false; own_counts.types];
5121 for leaf_ty in ty.walk() {
5122 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.kind {
5123 debug!("found use of ty param num {}", index);
5124 types_used[index as usize - own_counts.lifetimes] = true;
5125 } else if let ty::Error = leaf_ty.kind {
5126 // If there is already another error, do not emit
5127 // an error for not using a type parameter.
5128 assert!(tcx.sess.has_errors());
5133 let types = generics.params.iter().filter(|param| match param.kind {
5134 ty::GenericParamDefKind::Type { .. } => true,
5137 for (&used, param) in types_used.iter().zip(types) {
5139 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5140 let span = tcx.hir().span(id);
5141 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5142 .span_label(span, "unused type parameter")
5148 fn fatally_break_rust(sess: &Session) {
5149 let handler = sess.diagnostic();
5150 handler.span_bug_no_panic(
5152 "It looks like you're trying to break rust; would you like some ICE?",
5154 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5155 handler.note_without_error(
5156 "we would appreciate a joke overview: \
5157 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5159 handler.note_without_error(&format!("rustc {} running on {}",
5160 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5161 crate::session::config::host_triple(),
5165 fn potentially_plural_count(count: usize, word: &str) -> String {
5166 format!("{} {}{}", count, word, pluralise!(count))