1 // ignore-tidy-filelength
7 Within the check phase of type check, we check each item one at a time
8 (bodies of function expressions are checked as part of the containing
9 function). Inference is used to supply types wherever they are unknown.
11 By far the most complex case is checking the body of a function. This
12 can be broken down into several distinct phases:
14 - gather: creates type variables to represent the type of each local
15 variable and pattern binding.
17 - main: the main pass does the lion's share of the work: it
18 determines the types of all expressions, resolves
19 methods, checks for most invalid conditions, and so forth. In
20 some cases, where a type is unknown, it may create a type or region
21 variable and use that as the type of an expression.
23 In the process of checking, various constraints will be placed on
24 these type variables through the subtyping relationships requested
25 through the `demand` module. The `infer` module is in charge
26 of resolving those constraints.
28 - regionck: after main is complete, the regionck pass goes over all
29 types looking for regions and making sure that they did not escape
30 into places they are not in scope. This may also influence the
31 final assignments of the various region variables if there is some
34 - vtable: find and records the impls to use for each trait bound that
35 appears on a type parameter.
37 - writeback: writes the final types within a function body, replacing
38 type variables with their final inferred types. These final types
39 are written into the `tcx.node_types` table, which should *never* contain
40 any reference to a type variable.
44 While type checking a function, the intermediate types for the
45 expressions, blocks, and so forth contained within the function are
46 stored in `fcx.node_types` and `fcx.node_substs`. These types
47 may contain unresolved type variables. After type checking is
48 complete, the functions in the writeback module are used to take the
49 types from this table, resolve them, and then write them into their
50 permanent home in the type context `tcx`.
52 This means that during inferencing you should use `fcx.write_ty()`
53 and `fcx.expr_ty()` / `fcx.node_ty()` to write/obtain the types of
54 nodes within the function.
56 The types of top-level items, which never contain unbound type
57 variables, are stored directly into the `tcx` tables.
59 N.B., a type variable is not the same thing as a type parameter. A
60 type variable is rather an "instance" of a type parameter: that is,
61 given a generic function `fn foo<T>(t: T)`: while checking the
62 function `foo`, the type `ty_param(0)` refers to the type `T`, which
63 is treated in abstract. When `foo()` is called, however, `T` will be
64 substituted for a fresh type variable `N`. This variable will
65 eventually be resolved to some concrete type (which might itself be
86 mod generator_interior;
90 use crate::astconv::{AstConv, PathSeg};
91 use errors::{Applicability, DiagnosticBuilder, DiagnosticId, pluralise};
92 use rustc::hir::{self, ExprKind, GenericArg, ItemKind, Node, PatKind, QPath};
93 use rustc::hir::def::{CtorOf, Res, DefKind};
94 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
95 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
96 use rustc::hir::itemlikevisit::ItemLikeVisitor;
97 use rustc::hir::ptr::P;
98 use crate::middle::lang_items;
99 use crate::namespace::Namespace;
100 use rustc::infer::{self, InferCtxt, InferOk, InferResult};
101 use rustc::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
102 use rustc_index::vec::Idx;
103 use rustc_target::spec::abi::Abi;
104 use rustc::infer::opaque_types::OpaqueTypeDecl;
105 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
106 use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
107 use rustc::middle::region;
108 use rustc::mir::interpret::{ConstValue, GlobalId};
109 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
111 self, AdtKind, CanonicalUserType, Ty, TyCtxt, Const, GenericParamDefKind,
112 ToPolyTraitRef, ToPredicate, RegionKind, UserType
114 use rustc::ty::adjustment::{
115 Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast
117 use rustc::ty::fold::TypeFoldable;
118 use rustc::ty::query::Providers;
119 use rustc::ty::subst::{
120 GenericArgKind, Subst, InternalSubsts, SubstsRef, UserSelfTy, UserSubsts,
122 use rustc::ty::util::{Representability, IntTypeExt, Discr};
123 use rustc::ty::layout::VariantIdx;
124 use syntax_pos::{self, BytePos, Span, MultiSpan};
125 use syntax_pos::hygiene::DesugaringKind;
128 use syntax::feature_gate::{GateIssue, emit_feature_err};
129 use syntax::source_map::{DUMMY_SP, original_sp};
130 use syntax::symbol::{kw, sym};
131 use syntax::util::parser::ExprPrecedence;
133 use std::cell::{Cell, RefCell, Ref, RefMut};
134 use std::collections::hash_map::Entry;
137 use std::mem::replace;
138 use std::ops::{self, Deref};
141 use crate::require_c_abi_if_c_variadic;
142 use crate::session::Session;
143 use crate::session::config::EntryFnType;
144 use crate::TypeAndSubsts;
146 use crate::util::captures::Captures;
147 use crate::util::common::{ErrorReported, indenter};
148 use crate::util::nodemap::{DefIdMap, DefIdSet, FxHashSet, HirIdMap};
150 pub use self::Expectation::*;
151 use self::autoderef::Autoderef;
152 use self::callee::DeferredCallResolution;
153 use self::coercion::{CoerceMany, DynamicCoerceMany};
154 pub use self::compare_method::{compare_impl_method, compare_const_impl};
155 use self::method::{MethodCallee, SelfSource};
156 use self::TupleArgumentsFlag::*;
158 /// The type of a local binding, including the revealed type for anon types.
159 #[derive(Copy, Clone, Debug)]
160 pub struct LocalTy<'tcx> {
162 revealed_ty: Ty<'tcx>
165 /// A wrapper for `InferCtxt`'s `in_progress_tables` field.
166 #[derive(Copy, Clone)]
167 struct MaybeInProgressTables<'a, 'tcx> {
168 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
171 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
172 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
173 match self.maybe_tables {
174 Some(tables) => tables.borrow(),
176 bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables")
181 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
182 match self.maybe_tables {
183 Some(tables) => tables.borrow_mut(),
185 bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables")
191 /// Closures defined within the function. For example:
194 /// bar(move|| { ... })
197 /// Here, the function `foo()` and the closure passed to
198 /// `bar()` will each have their own `FnCtxt`, but they will
199 /// share the inherited fields.
200 pub struct Inherited<'a, 'tcx> {
201 infcx: InferCtxt<'a, 'tcx>,
203 tables: MaybeInProgressTables<'a, 'tcx>,
205 locals: RefCell<HirIdMap<LocalTy<'tcx>>>,
207 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
209 // Some additional `Sized` obligations badly affect type inference.
210 // These obligations are added in a later stage of typeck.
211 deferred_sized_obligations: RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
213 // When we process a call like `c()` where `c` is a closure type,
214 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
215 // `FnOnce` closure. In that case, we defer full resolution of the
216 // call until upvar inference can kick in and make the
217 // decision. We keep these deferred resolutions grouped by the
218 // def-id of the closure, so that once we decide, we can easily go
219 // back and process them.
220 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
222 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
224 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
226 // Opaque types found in explicit return types and their
227 // associated fresh inference variable. Writeback resolves these
228 // variables to get the concrete type, which can be used to
229 // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
230 opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
232 /// Each type parameter has an implicit region bound that
233 /// indicates it must outlive at least the function body (the user
234 /// may specify stronger requirements). This field indicates the
235 /// region of the callee. If it is `None`, then the parameter
236 /// environment is for an item or something where the "callee" is
238 implicit_region_bound: Option<ty::Region<'tcx>>,
240 body_id: Option<hir::BodyId>,
243 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
244 type Target = InferCtxt<'a, 'tcx>;
245 fn deref(&self) -> &Self::Target {
250 /// When type-checking an expression, we propagate downward
251 /// whatever type hint we are able in the form of an `Expectation`.
252 #[derive(Copy, Clone, Debug)]
253 pub enum Expectation<'tcx> {
254 /// We know nothing about what type this expression should have.
257 /// This expression should have the type given (or some subtype).
258 ExpectHasType(Ty<'tcx>),
260 /// This expression will be cast to the `Ty`.
261 ExpectCastableToType(Ty<'tcx>),
263 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
264 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
265 ExpectRvalueLikeUnsized(Ty<'tcx>),
268 impl<'a, 'tcx> Expectation<'tcx> {
269 // Disregard "castable to" expectations because they
270 // can lead us astray. Consider for example `if cond
271 // {22} else {c} as u8` -- if we propagate the
272 // "castable to u8" constraint to 22, it will pick the
273 // type 22u8, which is overly constrained (c might not
274 // be a u8). In effect, the problem is that the
275 // "castable to" expectation is not the tightest thing
276 // we can say, so we want to drop it in this case.
277 // The tightest thing we can say is "must unify with
278 // else branch". Note that in the case of a "has type"
279 // constraint, this limitation does not hold.
281 // If the expected type is just a type variable, then don't use
282 // an expected type. Otherwise, we might write parts of the type
283 // when checking the 'then' block which are incompatible with the
285 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
287 ExpectHasType(ety) => {
288 let ety = fcx.shallow_resolve(ety);
289 if !ety.is_ty_var() {
295 ExpectRvalueLikeUnsized(ety) => {
296 ExpectRvalueLikeUnsized(ety)
302 /// Provides an expectation for an rvalue expression given an *optional*
303 /// hint, which is not required for type safety (the resulting type might
304 /// be checked higher up, as is the case with `&expr` and `box expr`), but
305 /// is useful in determining the concrete type.
307 /// The primary use case is where the expected type is a fat pointer,
308 /// like `&[isize]`. For example, consider the following statement:
310 /// let x: &[isize] = &[1, 2, 3];
312 /// In this case, the expected type for the `&[1, 2, 3]` expression is
313 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
314 /// expectation `ExpectHasType([isize])`, that would be too strong --
315 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
316 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
317 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
318 /// which still is useful, because it informs integer literals and the like.
319 /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
320 /// for examples of where this comes up,.
321 fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
322 match fcx.tcx.struct_tail_without_normalization(ty).kind {
323 ty::Slice(_) | ty::Str | ty::Dynamic(..) => {
324 ExpectRvalueLikeUnsized(ty)
326 _ => ExpectHasType(ty)
330 // Resolves `expected` by a single level if it is a variable. If
331 // there is no expected type or resolution is not possible (e.g.,
332 // no constraints yet present), just returns `None`.
333 fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
335 NoExpectation => NoExpectation,
336 ExpectCastableToType(t) => {
337 ExpectCastableToType(fcx.resolve_vars_if_possible(&t))
339 ExpectHasType(t) => {
340 ExpectHasType(fcx.resolve_vars_if_possible(&t))
342 ExpectRvalueLikeUnsized(t) => {
343 ExpectRvalueLikeUnsized(fcx.resolve_vars_if_possible(&t))
348 fn to_option(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
349 match self.resolve(fcx) {
350 NoExpectation => None,
351 ExpectCastableToType(ty) |
353 ExpectRvalueLikeUnsized(ty) => Some(ty),
357 /// It sometimes happens that we want to turn an expectation into
358 /// a **hard constraint** (i.e., something that must be satisfied
359 /// for the program to type-check). `only_has_type` will return
360 /// such a constraint, if it exists.
361 fn only_has_type(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
362 match self.resolve(fcx) {
363 ExpectHasType(ty) => Some(ty),
364 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
368 /// Like `only_has_type`, but instead of returning `None` if no
369 /// hard constraint exists, creates a fresh type variable.
370 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> Ty<'tcx> {
371 self.only_has_type(fcx)
373 fcx.next_ty_var(TypeVariableOrigin {
374 kind: TypeVariableOriginKind::MiscVariable,
381 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
388 fn maybe_mut_place(m: hir::Mutability) -> Self {
390 hir::MutMutable => Needs::MutPlace,
391 hir::MutImmutable => Needs::None,
396 #[derive(Copy, Clone)]
397 pub struct UnsafetyState {
399 pub unsafety: hir::Unsafety,
400 pub unsafe_push_count: u32,
405 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
406 UnsafetyState { def, unsafety, unsafe_push_count: 0, from_fn: true }
409 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
410 match self.unsafety {
411 // If this unsafe, then if the outer function was already marked as
412 // unsafe we shouldn't attribute the unsafe'ness to the block. This
413 // way the block can be warned about instead of ignoring this
414 // extraneous block (functions are never warned about).
415 hir::Unsafety::Unsafe if self.from_fn => *self,
418 let (unsafety, def, count) = match blk.rules {
419 hir::PushUnsafeBlock(..) =>
420 (unsafety, blk.hir_id, self.unsafe_push_count.checked_add(1).unwrap()),
421 hir::PopUnsafeBlock(..) =>
422 (unsafety, blk.hir_id, self.unsafe_push_count.checked_sub(1).unwrap()),
423 hir::UnsafeBlock(..) =>
424 (hir::Unsafety::Unsafe, blk.hir_id, self.unsafe_push_count),
426 (unsafety, self.def, self.unsafe_push_count),
430 unsafe_push_count: count,
437 #[derive(Debug, Copy, Clone)]
443 /// Tracks whether executing a node may exit normally (versus
444 /// return/break/panic, which "diverge", leaving dead code in their
445 /// wake). Tracked semi-automatically (through type variables marked
446 /// as diverging), with some manual adjustments for control-flow
447 /// primitives (approximating a CFG).
448 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
450 /// Potentially unknown, some cases converge,
451 /// others require a CFG to determine them.
454 /// Definitely known to diverge and therefore
455 /// not reach the next sibling or its parent.
457 /// The `Span` points to the expression
458 /// that caused us to diverge
459 /// (e.g. `return`, `break`, etc).
461 /// In some cases (e.g. a `match` expression
462 /// where all arms diverge), we may be
463 /// able to provide a more informative
464 /// message to the user.
465 /// If this is `None`, a default messsage
466 /// will be generated, which is suitable
468 custom_note: Option<&'static str>
471 /// Same as `Always` but with a reachability
472 /// warning already emitted.
476 // Convenience impls for combining `Diverges`.
478 impl ops::BitAnd for Diverges {
480 fn bitand(self, other: Self) -> Self {
481 cmp::min(self, other)
485 impl ops::BitOr for Diverges {
487 fn bitor(self, other: Self) -> Self {
488 cmp::max(self, other)
492 impl ops::BitAndAssign for Diverges {
493 fn bitand_assign(&mut self, other: Self) {
494 *self = *self & other;
498 impl ops::BitOrAssign for Diverges {
499 fn bitor_assign(&mut self, other: Self) {
500 *self = *self | other;
505 /// Creates a `Diverges::Always` with the provided `span` and the default note message.
506 fn always(span: Span) -> Diverges {
513 fn is_always(self) -> bool {
514 // Enum comparison ignores the
515 // contents of fields, so we just
516 // fill them in with garbage here.
517 self >= Diverges::Always {
524 pub struct BreakableCtxt<'tcx> {
527 // this is `null` for loops where break with a value is illegal,
528 // such as `while`, `for`, and `while let`
529 coerce: Option<DynamicCoerceMany<'tcx>>,
532 pub struct EnclosingBreakables<'tcx> {
533 stack: Vec<BreakableCtxt<'tcx>>,
534 by_id: HirIdMap<usize>,
537 impl<'tcx> EnclosingBreakables<'tcx> {
538 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
539 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
540 bug!("could not find enclosing breakable with id {}", target_id);
546 pub struct FnCtxt<'a, 'tcx> {
549 /// The parameter environment used for proving trait obligations
550 /// in this function. This can change when we descend into
551 /// closures (as they bring new things into scope), hence it is
552 /// not part of `Inherited` (as of the time of this writing,
553 /// closures do not yet change the environment, but they will
555 param_env: ty::ParamEnv<'tcx>,
557 /// Number of errors that had been reported when we started
558 /// checking this function. On exit, if we find that *more* errors
559 /// have been reported, we will skip regionck and other work that
560 /// expects the types within the function to be consistent.
561 // FIXME(matthewjasper) This should not exist, and it's not correct
562 // if type checking is run in parallel.
563 err_count_on_creation: usize,
565 /// If `Some`, this stores coercion information for returned
566 /// expressions. If `None`, this is in a context where return is
567 /// inappropriate, such as a const expression.
569 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
570 /// can track all the return expressions and then use them to
571 /// compute a useful coercion from the set, similar to a match
572 /// expression or other branching context. You can use methods
573 /// like `expected_ty` to access the declared return type (if
575 ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
577 /// First span of a return site that we find. Used in error messages.
578 ret_coercion_span: RefCell<Option<Span>>,
580 yield_ty: Option<Ty<'tcx>>,
582 ps: RefCell<UnsafetyState>,
584 /// Whether the last checked node generates a divergence (e.g.,
585 /// `return` will set this to `Always`). In general, when entering
586 /// an expression or other node in the tree, the initial value
587 /// indicates whether prior parts of the containing expression may
588 /// have diverged. It is then typically set to `Maybe` (and the
589 /// old value remembered) for processing the subparts of the
590 /// current expression. As each subpart is processed, they may set
591 /// the flag to `Always`, etc. Finally, at the end, we take the
592 /// result and "union" it with the original value, so that when we
593 /// return the flag indicates if any subpart of the parent
594 /// expression (up to and including this part) has diverged. So,
595 /// if you read it after evaluating a subexpression `X`, the value
596 /// you get indicates whether any subexpression that was
597 /// evaluating up to and including `X` diverged.
599 /// We currently use this flag only for diagnostic purposes:
601 /// - To warn about unreachable code: if, after processing a
602 /// sub-expression but before we have applied the effects of the
603 /// current node, we see that the flag is set to `Always`, we
604 /// can issue a warning. This corresponds to something like
605 /// `foo(return)`; we warn on the `foo()` expression. (We then
606 /// update the flag to `WarnedAlways` to suppress duplicate
607 /// reports.) Similarly, if we traverse to a fresh statement (or
608 /// tail expression) from a `Always` setting, we will issue a
609 /// warning. This corresponds to something like `{return;
610 /// foo();}` or `{return; 22}`, where we would warn on the
613 /// An expression represents dead code if, after checking it,
614 /// the diverges flag is set to something other than `Maybe`.
615 diverges: Cell<Diverges>,
617 /// Whether any child nodes have any type errors.
618 has_errors: Cell<bool>,
620 enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
622 inh: &'a Inherited<'a, 'tcx>,
625 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
626 type Target = Inherited<'a, 'tcx>;
627 fn deref(&self) -> &Self::Target {
632 /// Helper type of a temporary returned by `Inherited::build(...)`.
633 /// Necessary because we can't write the following bound:
634 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
635 pub struct InheritedBuilder<'tcx> {
636 infcx: infer::InferCtxtBuilder<'tcx>,
640 impl Inherited<'_, 'tcx> {
641 pub fn build(tcx: TyCtxt<'tcx>, def_id: DefId) -> InheritedBuilder<'tcx> {
642 let hir_id_root = if def_id.is_local() {
643 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
644 DefId::local(hir_id.owner)
650 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
656 impl<'tcx> InheritedBuilder<'tcx> {
657 fn enter<F, R>(&mut self, f: F) -> R
659 F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
661 let def_id = self.def_id;
662 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
666 impl Inherited<'a, 'tcx> {
667 fn new(infcx: InferCtxt<'a, 'tcx>, def_id: DefId) -> Self {
669 let item_id = tcx.hir().as_local_hir_id(def_id);
670 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by(id));
671 let implicit_region_bound = body_id.map(|body_id| {
672 let body = tcx.hir().body(body_id);
673 tcx.mk_region(ty::ReScope(region::Scope {
674 id: body.value.hir_id.local_id,
675 data: region::ScopeData::CallSite
680 tables: MaybeInProgressTables {
681 maybe_tables: infcx.in_progress_tables,
684 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
685 locals: RefCell::new(Default::default()),
686 deferred_sized_obligations: RefCell::new(Vec::new()),
687 deferred_call_resolutions: RefCell::new(Default::default()),
688 deferred_cast_checks: RefCell::new(Vec::new()),
689 deferred_generator_interiors: RefCell::new(Vec::new()),
690 opaque_types: RefCell::new(Default::default()),
691 implicit_region_bound,
696 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
697 debug!("register_predicate({:?})", obligation);
698 if obligation.has_escaping_bound_vars() {
699 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}",
704 .register_predicate_obligation(self, obligation);
707 fn register_predicates<I>(&self, obligations: I)
708 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>>
710 for obligation in obligations {
711 self.register_predicate(obligation);
715 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
716 self.register_predicates(infer_ok.obligations);
720 fn normalize_associated_types_in<T>(&self,
723 param_env: ty::ParamEnv<'tcx>,
725 where T : TypeFoldable<'tcx>
727 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
728 self.register_infer_ok_obligations(ok)
732 struct CheckItemTypesVisitor<'tcx> {
736 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
737 fn visit_item(&mut self, i: &'tcx hir::Item) {
738 check_item_type(self.tcx, i);
740 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
741 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
744 pub fn check_wf_new(tcx: TyCtxt<'_>) {
745 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
746 tcx.hir().krate().par_visit_all_item_likes(&mut visit);
749 fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
750 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
753 fn typeck_item_bodies(tcx: TyCtxt<'_>, crate_num: CrateNum) {
754 debug_assert!(crate_num == LOCAL_CRATE);
755 tcx.par_body_owners(|body_owner_def_id| {
756 tcx.ensure().typeck_tables_of(body_owner_def_id);
760 fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
761 wfcheck::check_item_well_formed(tcx, def_id);
764 fn check_trait_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
765 wfcheck::check_trait_item(tcx, def_id);
768 fn check_impl_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
769 wfcheck::check_impl_item(tcx, def_id);
772 pub fn provide(providers: &mut Providers<'_>) {
773 method::provide(providers);
774 *providers = Providers {
780 check_item_well_formed,
781 check_trait_item_well_formed,
782 check_impl_item_well_formed,
783 check_mod_item_types,
788 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
789 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
792 /// If this `DefId` is a "primary tables entry", returns
793 /// `Some((body_id, header, decl))` with information about
794 /// it's body-id, fn-header and fn-decl (if any). Otherwise,
797 /// If this function returns `Some`, then `typeck_tables(def_id)` will
798 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
799 /// may not succeed. In some cases where this function returns `None`
800 /// (notably closures), `typeck_tables(def_id)` would wind up
801 /// redirecting to the owning function.
805 ) -> Option<(hir::BodyId, Option<&hir::Ty>, Option<&hir::FnHeader>, Option<&hir::FnDecl>)> {
806 match tcx.hir().get(id) {
807 Node::Item(item) => {
809 hir::ItemKind::Const(ref ty, body) |
810 hir::ItemKind::Static(ref ty, _, body) =>
811 Some((body, Some(ty), None, None)),
812 hir::ItemKind::Fn(ref decl, ref header, .., body) =>
813 Some((body, None, Some(header), Some(decl))),
818 Node::TraitItem(item) => {
820 hir::TraitItemKind::Const(ref ty, Some(body)) =>
821 Some((body, Some(ty), None, None)),
822 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
823 Some((body, None, Some(&sig.header), Some(&sig.decl))),
828 Node::ImplItem(item) => {
830 hir::ImplItemKind::Const(ref ty, body) =>
831 Some((body, Some(ty), None, None)),
832 hir::ImplItemKind::Method(ref sig, body) =>
833 Some((body, None, Some(&sig.header), Some(&sig.decl))),
838 Node::AnonConst(constant) => Some((constant.body, None, None, None)),
843 fn has_typeck_tables(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
844 // Closures' tables come from their outermost function,
845 // as they are part of the same "inference environment".
846 let outer_def_id = tcx.closure_base_def_id(def_id);
847 if outer_def_id != def_id {
848 return tcx.has_typeck_tables(outer_def_id);
851 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
852 primary_body_of(tcx, id).is_some()
855 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: DefId) -> &DefIdSet {
856 &*tcx.typeck_tables_of(def_id).used_trait_imports
859 fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
860 // Closures' tables come from their outermost function,
861 // as they are part of the same "inference environment".
862 let outer_def_id = tcx.closure_base_def_id(def_id);
863 if outer_def_id != def_id {
864 return tcx.typeck_tables_of(outer_def_id);
867 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
868 let span = tcx.hir().span(id);
870 // Figure out what primary body this item has.
871 let (body_id, body_ty, fn_header, fn_decl) = primary_body_of(tcx, id)
873 span_bug!(span, "can't type-check body of {:?}", def_id);
875 let body = tcx.hir().body(body_id);
877 let tables = Inherited::build(tcx, def_id).enter(|inh| {
878 let param_env = tcx.param_env(def_id);
879 let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
880 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
881 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
882 AstConv::ty_of_fn(&fcx, header.unsafety, header.abi, decl)
887 check_abi(tcx, span, fn_sig.abi());
889 // Compute the fty from point of view of inside the fn.
891 tcx.liberate_late_bound_regions(def_id, &fn_sig);
893 inh.normalize_associated_types_in(body.value.span,
898 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
901 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
902 let expected_type = body_ty.and_then(|ty| match ty.kind {
903 hir::TyKind::Infer => Some(AstConv::ast_ty_to_ty(&fcx, ty)),
905 }).unwrap_or_else(|| tcx.type_of(def_id));
906 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
907 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
909 let revealed_ty = if tcx.features().impl_trait_in_bindings {
910 fcx.instantiate_opaque_types_from_value(
919 // Gather locals in statics (because of block expressions).
920 GatherLocalsVisitor { fcx: &fcx, parent_id: id, }.visit_body(body);
922 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
924 fcx.write_ty(id, revealed_ty);
929 // All type checking constraints were added, try to fallback unsolved variables.
930 fcx.select_obligations_where_possible(false, |_| {});
931 let mut fallback_has_occurred = false;
932 for ty in &fcx.unsolved_variables() {
933 fallback_has_occurred |= fcx.fallback_if_possible(ty);
935 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
937 // Even though coercion casts provide type hints, we check casts after fallback for
938 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
941 // Closure and generator analysis may run after fallback
942 // because they don't constrain other type variables.
943 fcx.closure_analyze(body);
944 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
945 fcx.resolve_generator_interiors(def_id);
947 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
948 let ty = fcx.normalize_ty(span, ty);
949 fcx.require_type_is_sized(ty, span, code);
951 fcx.select_all_obligations_or_error();
953 if fn_decl.is_some() {
954 fcx.regionck_fn(id, body);
956 fcx.regionck_expr(body);
959 fcx.resolve_type_vars_in_body(body)
962 // Consistency check our TypeckTables instance can hold all ItemLocalIds
963 // it will need to hold.
964 assert_eq!(tables.local_id_root, Some(DefId::local(id.owner)));
969 fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
970 if !tcx.sess.target.target.is_abi_supported(abi) {
971 struct_span_err!(tcx.sess, span, E0570,
972 "The ABI `{}` is not supported for the current target", abi).emit()
976 struct GatherLocalsVisitor<'a, 'tcx> {
977 fcx: &'a FnCtxt<'a, 'tcx>,
978 parent_id: hir::HirId,
981 impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
982 fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
985 // infer the variable's type
986 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
987 kind: TypeVariableOriginKind::TypeInference,
990 self.fcx.locals.borrow_mut().insert(nid, LocalTy {
997 // take type that the user specified
998 self.fcx.locals.borrow_mut().insert(nid, typ);
1005 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
1006 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
1007 NestedVisitorMap::None
1010 // Add explicitly-declared locals.
1011 fn visit_local(&mut self, local: &'tcx hir::Local) {
1012 let local_ty = match local.ty {
1014 let o_ty = self.fcx.to_ty(&ty);
1016 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
1017 self.fcx.instantiate_opaque_types_from_value(
1026 let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(
1027 &UserType::Ty(revealed_ty)
1029 debug!("visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
1030 ty.hir_id, o_ty, revealed_ty, c_ty);
1031 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
1033 Some(LocalTy { decl_ty: o_ty, revealed_ty })
1037 self.assign(local.span, local.hir_id, local_ty);
1039 debug!("local variable {:?} is assigned type {}",
1041 self.fcx.ty_to_string(
1042 self.fcx.locals.borrow().get(&local.hir_id).unwrap().clone().decl_ty));
1043 intravisit::walk_local(self, local);
1046 // Add pattern bindings.
1047 fn visit_pat(&mut self, p: &'tcx hir::Pat) {
1048 if let PatKind::Binding(_, _, ident, _) = p.kind {
1049 let var_ty = self.assign(p.span, p.hir_id, None);
1051 if !self.fcx.tcx.features().unsized_locals {
1052 self.fcx.require_type_is_sized(var_ty, p.span,
1053 traits::VariableType(p.hir_id));
1056 debug!("pattern binding {} is assigned to {} with type {:?}",
1058 self.fcx.ty_to_string(
1059 self.fcx.locals.borrow().get(&p.hir_id).unwrap().clone().decl_ty),
1062 intravisit::walk_pat(self, p);
1065 // Don't descend into the bodies of nested closures
1068 _: intravisit::FnKind<'tcx>,
1069 _: &'tcx hir::FnDecl,
1076 /// When `check_fn` is invoked on a generator (i.e., a body that
1077 /// includes yield), it returns back some information about the yield
1079 struct GeneratorTypes<'tcx> {
1080 /// Type of value that is yielded.
1083 /// Types that are captured (see `GeneratorInterior` for more).
1086 /// Indicates if the generator is movable or static (immovable).
1087 movability: hir::GeneratorMovability,
1090 /// Helper used for fns and closures. Does the grungy work of checking a function
1091 /// body and returns the function context used for that purpose, since in the case of a fn item
1092 /// there is still a bit more to do.
1095 /// * inherited: other fields inherited from the enclosing fn (if any)
1096 fn check_fn<'a, 'tcx>(
1097 inherited: &'a Inherited<'a, 'tcx>,
1098 param_env: ty::ParamEnv<'tcx>,
1099 fn_sig: ty::FnSig<'tcx>,
1100 decl: &'tcx hir::FnDecl,
1102 body: &'tcx hir::Body,
1103 can_be_generator: Option<hir::GeneratorMovability>,
1104 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
1105 let mut fn_sig = fn_sig.clone();
1107 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1109 // Create the function context. This is either derived from scratch or,
1110 // in the case of closures, based on the outer context.
1111 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1112 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1114 let declared_ret_ty = fn_sig.output();
1115 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1116 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(
1121 debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
1122 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1123 fn_sig = fcx.tcx.mk_fn_sig(
1124 fn_sig.inputs().iter().cloned(),
1131 let span = body.value.span;
1133 fn_maybe_err(fcx.tcx, span, fn_sig.abi);
1135 if body.generator_kind.is_some() && can_be_generator.is_some() {
1136 let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
1137 kind: TypeVariableOriginKind::TypeInference,
1140 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1141 fcx.yield_ty = Some(yield_ty);
1144 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id(fn_id));
1145 let outer_hir_id = fcx.tcx.hir().as_local_hir_id(outer_def_id).unwrap();
1146 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id, }.visit_body(body);
1148 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
1149 // (as it's created inside the body itself, not passed in from outside).
1150 let maybe_va_list = if fn_sig.c_variadic {
1151 let va_list_did = fcx.tcx.require_lang_item(
1152 lang_items::VaListTypeLangItem,
1153 Some(body.params.last().unwrap().span),
1155 let region = fcx.tcx.mk_region(ty::ReScope(region::Scope {
1156 id: body.value.hir_id.local_id,
1157 data: region::ScopeData::CallSite
1160 Some(fcx.tcx.type_of(va_list_did).subst(fcx.tcx, &[region.into()]))
1165 // Add formal parameters.
1166 for (param_ty, param) in
1167 fn_sig.inputs().iter().copied()
1168 .chain(maybe_va_list)
1171 // Check the pattern.
1172 fcx.check_pat_top(¶m.pat, param_ty, None);
1174 // Check that argument is Sized.
1175 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1176 // for simple cases like `fn foo(x: Trait)`,
1177 // where we would error once on the parameter as a whole, and once on the binding `x`.
1178 if param.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1179 fcx.require_type_is_sized(param_ty, decl.output.span(), traits::SizedArgumentType);
1182 fcx.write_ty(param.hir_id, param_ty);
1185 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1187 fcx.check_return_expr(&body.value);
1189 // We insert the deferred_generator_interiors entry after visiting the body.
1190 // This ensures that all nested generators appear before the entry of this generator.
1191 // resolve_generator_interiors relies on this property.
1192 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
1193 let interior = fcx.next_ty_var(TypeVariableOrigin {
1194 kind: TypeVariableOriginKind::MiscVariable,
1197 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
1198 Some(GeneratorTypes {
1199 yield_ty: fcx.yield_ty.unwrap(),
1201 movability: can_be_generator.unwrap(),
1207 // Finalize the return check by taking the LUB of the return types
1208 // we saw and assigning it to the expected return type. This isn't
1209 // really expected to fail, since the coercions would have failed
1210 // earlier when trying to find a LUB.
1212 // However, the behavior around `!` is sort of complex. In the
1213 // event that the `actual_return_ty` comes back as `!`, that
1214 // indicates that the fn either does not return or "returns" only
1215 // values of type `!`. In this case, if there is an expected
1216 // return type that is *not* `!`, that should be ok. But if the
1217 // return type is being inferred, we want to "fallback" to `!`:
1219 // let x = move || panic!();
1221 // To allow for that, I am creating a type variable with diverging
1222 // fallback. This was deemed ever so slightly better than unifying
1223 // the return value with `!` because it allows for the caller to
1224 // make more assumptions about the return type (e.g., they could do
1226 // let y: Option<u32> = Some(x());
1228 // which would then cause this return type to become `u32`, not
1230 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1231 let mut actual_return_ty = coercion.complete(&fcx);
1232 if actual_return_ty.is_never() {
1233 actual_return_ty = fcx.next_diverging_ty_var(
1234 TypeVariableOrigin {
1235 kind: TypeVariableOriginKind::DivergingFn,
1240 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1242 // Check that the main return type implements the termination trait.
1243 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1244 if let Some((def_id, EntryFnType::Main)) = fcx.tcx.entry_fn(LOCAL_CRATE) {
1245 let main_id = fcx.tcx.hir().as_local_hir_id(def_id).unwrap();
1246 if main_id == fn_id {
1247 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1248 let trait_ref = ty::TraitRef::new(term_id, substs);
1249 let return_ty_span = decl.output.span();
1250 let cause = traits::ObligationCause::new(
1251 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1253 inherited.register_predicate(
1254 traits::Obligation::new(
1255 cause, param_env, trait_ref.to_predicate()));
1260 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1261 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1262 if panic_impl_did == fcx.tcx.hir().local_def_id(fn_id) {
1263 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1264 // at this point we don't care if there are duplicate handlers or if the handler has
1265 // the wrong signature as this value we'll be used when writing metadata and that
1266 // only happens if compilation succeeded
1267 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1269 if declared_ret_ty.kind != ty::Never {
1270 fcx.tcx.sess.span_err(
1272 "return type should be `!`",
1276 let inputs = fn_sig.inputs();
1277 let span = fcx.tcx.hir().span(fn_id);
1278 if inputs.len() == 1 {
1279 let arg_is_panic_info = match inputs[0].kind {
1280 ty::Ref(region, ty, mutbl) => match ty.kind {
1281 ty::Adt(ref adt, _) => {
1282 adt.did == panic_info_did &&
1283 mutbl == hir::Mutability::MutImmutable &&
1284 *region != RegionKind::ReStatic
1291 if !arg_is_panic_info {
1292 fcx.tcx.sess.span_err(
1293 decl.inputs[0].span,
1294 "argument should be `&PanicInfo`",
1298 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1299 if let ItemKind::Fn(_, _, ref generics, _) = item.kind {
1300 if !generics.params.is_empty() {
1301 fcx.tcx.sess.span_err(
1303 "should have no type parameters",
1309 let span = fcx.tcx.sess.source_map().def_span(span);
1310 fcx.tcx.sess.span_err(span, "function should have one argument");
1313 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1318 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1319 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1320 if alloc_error_handler_did == fcx.tcx.hir().local_def_id(fn_id) {
1321 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1322 if declared_ret_ty.kind != ty::Never {
1323 fcx.tcx.sess.span_err(
1325 "return type should be `!`",
1329 let inputs = fn_sig.inputs();
1330 let span = fcx.tcx.hir().span(fn_id);
1331 if inputs.len() == 1 {
1332 let arg_is_alloc_layout = match inputs[0].kind {
1333 ty::Adt(ref adt, _) => {
1334 adt.did == alloc_layout_did
1339 if !arg_is_alloc_layout {
1340 fcx.tcx.sess.span_err(
1341 decl.inputs[0].span,
1342 "argument should be `Layout`",
1346 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1347 if let ItemKind::Fn(_, _, ref generics, _) = item.kind {
1348 if !generics.params.is_empty() {
1349 fcx.tcx.sess.span_err(
1351 "`#[alloc_error_handler]` function should have no type \
1358 let span = fcx.tcx.sess.source_map().def_span(span);
1359 fcx.tcx.sess.span_err(span, "function should have one argument");
1362 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1370 fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1371 let def_id = tcx.hir().local_def_id(id);
1372 let def = tcx.adt_def(def_id);
1373 def.destructor(tcx); // force the destructor to be evaluated
1374 check_representable(tcx, span, def_id);
1376 if def.repr.simd() {
1377 check_simd(tcx, span, def_id);
1380 check_transparent(tcx, span, def_id);
1381 check_packed(tcx, span, def_id);
1384 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1385 let def_id = tcx.hir().local_def_id(id);
1386 let def = tcx.adt_def(def_id);
1387 def.destructor(tcx); // force the destructor to be evaluated
1388 check_representable(tcx, span, def_id);
1389 check_transparent(tcx, span, def_id);
1390 check_packed(tcx, span, def_id);
1393 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
1394 /// projections that would result in "inheriting lifetimes".
1395 fn check_opaque<'tcx>(
1398 substs: SubstsRef<'tcx>,
1400 origin: &hir::OpaqueTyOrigin,
1402 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
1403 check_opaque_for_cycles(tcx, def_id, substs, span, origin);
1406 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
1407 /// in "inheriting lifetimes".
1408 fn check_opaque_for_inheriting_lifetimes(
1413 let item = tcx.hir().expect_item(
1414 tcx.hir().as_local_hir_id(def_id).expect("opaque type is not local"));
1415 debug!("check_opaque_for_inheriting_lifetimes: def_id={:?} span={:?} item={:?}",
1416 def_id, span, item);
1419 struct ProhibitOpaqueVisitor<'tcx> {
1420 opaque_identity_ty: Ty<'tcx>,
1421 generics: &'tcx ty::Generics,
1424 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
1425 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
1426 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
1427 if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) }
1430 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1431 debug!("check_opaque_for_inheriting_lifetimes: (visit_region) r={:?}", r);
1432 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
1433 return *index < self.generics.parent_count as u32;
1436 r.super_visit_with(self)
1440 let prohibit_opaque = match item.kind {
1441 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn, .. }) |
1442 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn, .. }) => {
1443 let mut visitor = ProhibitOpaqueVisitor {
1444 opaque_identity_ty: tcx.mk_opaque(
1445 def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1446 generics: tcx.generics_of(def_id),
1448 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1450 tcx.predicates_of(def_id).predicates.iter().any(
1451 |(predicate, _)| predicate.visit_with(&mut visitor))
1456 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1457 if prohibit_opaque {
1458 let is_async = match item.kind {
1459 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1460 hir::OpaqueTyOrigin::AsyncFn => true,
1463 _ => unreachable!(),
1466 tcx.sess.span_err(span, &format!(
1467 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1469 if is_async { "async fn" } else { "impl Trait" },
1474 /// Checks that an opaque type does not contain cycles.
1475 fn check_opaque_for_cycles<'tcx>(
1478 substs: SubstsRef<'tcx>,
1480 origin: &hir::OpaqueTyOrigin,
1482 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1483 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1485 tcx.sess, span, E0733,
1486 "recursion in an `async fn` requires boxing",
1488 .span_label(span, "recursive `async fn`")
1489 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`.")
1492 let mut err = struct_span_err!(
1493 tcx.sess, span, E0720,
1494 "opaque type expands to a recursive type",
1496 err.span_label(span, "expands to a recursive type");
1497 if let ty::Opaque(..) = partially_expanded_type.kind {
1498 err.note("type resolves to itself");
1500 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1507 // Forbid defining intrinsics in Rust code,
1508 // as they must always be defined by the compiler.
1509 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1510 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1511 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1515 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
1517 "check_item_type(it.hir_id={}, it.name={})",
1519 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1521 let _indenter = indenter();
1523 // Consts can play a role in type-checking, so they are included here.
1524 hir::ItemKind::Static(..) => {
1525 let def_id = tcx.hir().local_def_id(it.hir_id);
1526 tcx.typeck_tables_of(def_id);
1527 maybe_check_static_with_link_section(tcx, def_id, it.span);
1529 hir::ItemKind::Const(..) => {
1530 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1532 hir::ItemKind::Enum(ref enum_definition, _) => {
1533 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1535 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1536 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1537 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1538 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1539 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1540 check_impl_items_against_trait(
1547 let trait_def_id = impl_trait_ref.def_id;
1548 check_on_unimplemented(tcx, trait_def_id, it);
1551 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1552 let def_id = tcx.hir().local_def_id(it.hir_id);
1553 check_on_unimplemented(tcx, def_id, it);
1555 for item in items.iter() {
1556 let item = tcx.hir().trait_item(item.id);
1557 if let hir::TraitItemKind::Method(sig, _) = &item.kind {
1558 let abi = sig.header.abi;
1559 fn_maybe_err(tcx, item.ident.span, abi);
1563 hir::ItemKind::Struct(..) => {
1564 check_struct(tcx, it.hir_id, it.span);
1566 hir::ItemKind::Union(..) => {
1567 check_union(tcx, it.hir_id, it.span);
1569 hir::ItemKind::OpaqueTy(hir::OpaqueTy{origin, ..}) => {
1570 let def_id = tcx.hir().local_def_id(it.hir_id);
1572 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1573 check_opaque(tcx, def_id, substs, it.span, &origin);
1575 hir::ItemKind::TyAlias(..) => {
1576 let def_id = tcx.hir().local_def_id(it.hir_id);
1577 let pty_ty = tcx.type_of(def_id);
1578 let generics = tcx.generics_of(def_id);
1579 check_bounds_are_used(tcx, &generics, pty_ty);
1581 hir::ItemKind::ForeignMod(ref m) => {
1582 check_abi(tcx, it.span, m.abi);
1584 if m.abi == Abi::RustIntrinsic {
1585 for item in &m.items {
1586 intrinsic::check_intrinsic_type(tcx, item);
1588 } else if m.abi == Abi::PlatformIntrinsic {
1589 for item in &m.items {
1590 intrinsic::check_platform_intrinsic_type(tcx, item);
1593 for item in &m.items {
1594 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1595 let own_counts = generics.own_counts();
1596 if generics.params.len() - own_counts.lifetimes != 0 {
1597 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1598 (_, 0) => ("type", "types", Some("u32")),
1599 // We don't specify an example value, because we can't generate
1600 // a valid value for any type.
1601 (0, _) => ("const", "consts", None),
1602 _ => ("type or const", "types or consts", None),
1608 "foreign items may not have {} parameters",
1612 &format!("can't have {} parameters", kinds),
1614 // FIXME: once we start storing spans for type arguments, turn this
1615 // into a suggestion.
1617 "replace the {} parameters with concrete {}{}",
1620 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1625 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.kind {
1626 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1631 _ => { /* nothing to do */ }
1635 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1636 // Only restricted on wasm32 target for now
1637 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1641 // If `#[link_section]` is missing, then nothing to verify
1642 let attrs = tcx.codegen_fn_attrs(id);
1643 if attrs.link_section.is_none() {
1647 // For the wasm32 target statics with `#[link_section]` are placed into custom
1648 // sections of the final output file, but this isn't link custom sections of
1649 // other executable formats. Namely we can only embed a list of bytes,
1650 // nothing with pointers to anything else or relocations. If any relocation
1651 // show up, reject them here.
1652 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1653 // the consumer's responsibility to ensure all bytes that have been read
1654 // have defined values.
1655 let instance = ty::Instance::mono(tcx, id);
1656 let cid = GlobalId {
1660 let param_env = ty::ParamEnv::reveal_all();
1661 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1662 let alloc = if let ConstValue::ByRef { alloc, .. } = static_.val {
1665 bug!("Matching on non-ByRef static")
1667 if alloc.relocations().len() != 0 {
1668 let msg = "statics with a custom `#[link_section]` must be a \
1669 simple list of bytes on the wasm target with no \
1670 extra levels of indirection such as references";
1671 tcx.sess.span_err(span, msg);
1676 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item) {
1677 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1678 // an error would be reported if this fails.
1679 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1682 fn report_forbidden_specialization(
1684 impl_item: &hir::ImplItem,
1687 let mut err = struct_span_err!(
1688 tcx.sess, impl_item.span, E0520,
1689 "`{}` specializes an item from a parent `impl`, but \
1690 that item is not marked `default`",
1692 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1695 match tcx.span_of_impl(parent_impl) {
1697 err.span_label(span, "parent `impl` is here");
1698 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1702 err.note(&format!("parent implementation is in crate `{}`", cname));
1709 fn check_specialization_validity<'tcx>(
1711 trait_def: &ty::TraitDef,
1712 trait_item: &ty::AssocItem,
1714 impl_item: &hir::ImplItem,
1716 let kind = match impl_item.kind {
1717 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1718 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1719 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1720 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1723 let mut ancestor_impls = trait_def.ancestors(tcx, impl_id)
1725 .filter_map(|parent| {
1726 if parent.is_from_trait() {
1729 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
1734 if ancestor_impls.peek().is_none() {
1735 // No parent, nothing to specialize.
1739 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
1741 // Parent impl exists, and contains the parent item we're trying to specialize, but
1742 // doesn't mark it `default`.
1743 Some(parent_item) if tcx.impl_item_is_final(&parent_item) => {
1744 Some(Err(parent_impl.def_id()))
1747 // Parent impl contains item and makes it specializable.
1752 // Parent impl doesn't mention the item. This means it's inherited from the
1753 // grandparent. In that case, if parent is a `default impl`, inherited items use the
1754 // "defaultness" from the grandparent, else they are final.
1755 None => if tcx.impl_is_default(parent_impl.def_id()) {
1758 Some(Err(parent_impl.def_id()))
1763 // If `opt_result` is `None`, we have only encoutered `default impl`s that don't contain the
1764 // item. This is allowed, the item isn't actually getting specialized here.
1765 let result = opt_result.unwrap_or(Ok(()));
1767 if let Err(parent_impl) = result {
1768 report_forbidden_specialization(tcx, impl_item, parent_impl);
1772 fn check_impl_items_against_trait<'tcx>(
1776 impl_trait_ref: ty::TraitRef<'tcx>,
1777 impl_item_refs: &[hir::ImplItemRef],
1779 let impl_span = tcx.sess.source_map().def_span(impl_span);
1781 // If the trait reference itself is erroneous (so the compilation is going
1782 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1783 // isn't populated for such impls.
1784 if impl_trait_ref.references_error() { return; }
1786 // Locate trait definition and items
1787 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1788 let mut overridden_associated_type = None;
1790 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1792 // Check existing impl methods to see if they are both present in trait
1793 // and compatible with trait signature
1794 for impl_item in impl_items() {
1795 let ty_impl_item = tcx.associated_item(
1796 tcx.hir().local_def_id(impl_item.hir_id));
1797 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1798 .find(|ac| Namespace::from(&impl_item.kind) == Namespace::from(ac.kind) &&
1799 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1801 // Not compatible, but needed for the error message
1802 tcx.associated_items(impl_trait_ref.def_id)
1803 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1806 // Check that impl definition matches trait definition
1807 if let Some(ty_trait_item) = ty_trait_item {
1808 match impl_item.kind {
1809 hir::ImplItemKind::Const(..) => {
1810 // Find associated const definition.
1811 if ty_trait_item.kind == ty::AssocKind::Const {
1812 compare_const_impl(tcx,
1818 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1819 "item `{}` is an associated const, \
1820 which doesn't match its trait `{}`",
1823 err.span_label(impl_item.span, "does not match trait");
1824 // We can only get the spans from local trait definition
1825 // Same for E0324 and E0325
1826 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1827 err.span_label(trait_span, "item in trait");
1832 hir::ImplItemKind::Method(..) => {
1833 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1834 if ty_trait_item.kind == ty::AssocKind::Method {
1835 compare_impl_method(tcx,
1842 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1843 "item `{}` is an associated method, \
1844 which doesn't match its trait `{}`",
1847 err.span_label(impl_item.span, "does not match trait");
1848 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1849 err.span_label(trait_span, "item in trait");
1854 hir::ImplItemKind::OpaqueTy(..) |
1855 hir::ImplItemKind::TyAlias(_) => {
1856 if ty_trait_item.kind == ty::AssocKind::Type {
1857 if ty_trait_item.defaultness.has_value() {
1858 overridden_associated_type = Some(impl_item);
1861 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1862 "item `{}` is an associated type, \
1863 which doesn't match its trait `{}`",
1866 err.span_label(impl_item.span, "does not match trait");
1867 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1868 err.span_label(trait_span, "item in trait");
1875 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1879 // Check for missing items from trait
1880 let mut missing_items = Vec::new();
1881 let mut invalidated_items = Vec::new();
1882 let associated_type_overridden = overridden_associated_type.is_some();
1883 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1884 let is_implemented = trait_def.ancestors(tcx, impl_id)
1885 .leaf_def(tcx, trait_item.ident, trait_item.kind)
1886 .map(|node_item| !node_item.node.is_from_trait())
1889 if !is_implemented && !tcx.impl_is_default(impl_id) {
1890 if !trait_item.defaultness.has_value() {
1891 missing_items.push(trait_item);
1892 } else if associated_type_overridden {
1893 invalidated_items.push(trait_item.ident);
1898 if !missing_items.is_empty() {
1899 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1900 "not all trait items implemented, missing: `{}`",
1901 missing_items.iter()
1902 .map(|trait_item| trait_item.ident.to_string())
1903 .collect::<Vec<_>>().join("`, `"));
1904 err.span_label(impl_span, format!("missing `{}` in implementation",
1905 missing_items.iter()
1906 .map(|trait_item| trait_item.ident.to_string())
1907 .collect::<Vec<_>>().join("`, `")));
1908 for trait_item in missing_items {
1909 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1910 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1912 err.note_trait_signature(trait_item.ident.to_string(),
1913 trait_item.signature(tcx));
1919 if !invalidated_items.is_empty() {
1920 let invalidator = overridden_associated_type.unwrap();
1921 span_err!(tcx.sess, invalidator.span, E0399,
1922 "the following trait items need to be reimplemented \
1923 as `{}` was overridden: `{}`",
1925 invalidated_items.iter()
1926 .map(|name| name.to_string())
1927 .collect::<Vec<_>>().join("`, `"))
1931 /// Checks whether a type can be represented in memory. In particular, it
1932 /// identifies types that contain themselves without indirection through a
1933 /// pointer, which would mean their size is unbounded.
1934 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
1935 let rty = tcx.type_of(item_def_id);
1937 // Check that it is possible to represent this type. This call identifies
1938 // (1) types that contain themselves and (2) types that contain a different
1939 // recursive type. It is only necessary to throw an error on those that
1940 // contain themselves. For case 2, there must be an inner type that will be
1941 // caught by case 1.
1942 match rty.is_representable(tcx, sp) {
1943 Representability::SelfRecursive(spans) => {
1944 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1946 err.span_label(span, "recursive without indirection");
1951 Representability::Representable | Representability::ContainsRecursive => (),
1956 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1957 let t = tcx.type_of(def_id);
1958 if let ty::Adt(def, substs) = t.kind {
1959 if def.is_struct() {
1960 let fields = &def.non_enum_variant().fields;
1961 if fields.is_empty() {
1962 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1965 let e = fields[0].ty(tcx, substs);
1966 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1967 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1968 .span_label(sp, "SIMD elements must have the same type")
1973 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1974 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1976 span_err!(tcx.sess, sp, E0077,
1977 "SIMD vector element type should be machine type");
1985 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
1986 let repr = tcx.adt_def(def_id).repr;
1988 for attr in tcx.get_attrs(def_id).iter() {
1989 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
1990 if let attr::ReprPacked(pack) = r {
1991 if let Some(repr_pack) = repr.pack {
1992 if pack as u64 != repr_pack.bytes() {
1994 tcx.sess, sp, E0634,
1995 "type has conflicting packed representation hints"
2002 if repr.align.is_some() {
2003 struct_span_err!(tcx.sess, sp, E0587,
2004 "type has conflicting packed and align representation hints").emit();
2006 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
2007 struct_span_err!(tcx.sess, sp, E0588,
2008 "packed type cannot transitively contain a `[repr(align)]` type").emit();
2013 fn check_packed_inner(tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec<DefId>) -> bool {
2014 let t = tcx.type_of(def_id);
2015 if stack.contains(&def_id) {
2016 debug!("check_packed_inner: {:?} is recursive", t);
2019 if let ty::Adt(def, substs) = t.kind {
2020 if def.is_struct() || def.is_union() {
2021 if tcx.adt_def(def.did).repr.align.is_some() {
2024 // push struct def_id before checking fields
2026 for field in &def.non_enum_variant().fields {
2027 let f = field.ty(tcx, substs);
2028 if let ty::Adt(def, _) = f.kind {
2029 if check_packed_inner(tcx, def.did, stack) {
2034 // only need to pop if not early out
2041 /// Emit an error when encountering more or less than one variant in a transparent enum.
2042 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2043 let variant_spans: Vec<_> = adt.variants.iter().map(|variant| {
2044 tcx.hir().span_if_local(variant.def_id).unwrap()
2047 "needs exactly one variant, but has {}",
2050 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2051 err.span_label(sp, &msg);
2052 if let &[ref start @ .., ref end] = &variant_spans[..] {
2053 for variant_span in start {
2054 err.span_label(*variant_span, "");
2056 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2061 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2063 fn bad_non_zero_sized_fields<'tcx>(
2065 adt: &'tcx ty::AdtDef,
2067 field_spans: impl Iterator<Item = Span>,
2070 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2071 let mut err = struct_span_err!(
2075 "{}transparent {} {}",
2076 if adt.is_enum() { "the variant of a " } else { "" },
2080 err.span_label(sp, &msg);
2081 for sp in field_spans {
2082 err.span_label(sp, "this field is non-zero-sized");
2087 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2088 let adt = tcx.adt_def(def_id);
2089 if !adt.repr.transparent() {
2092 let sp = tcx.sess.source_map().def_span(sp);
2095 if !tcx.features().transparent_enums {
2097 &tcx.sess.parse_sess,
2098 sym::transparent_enums,
2100 GateIssue::Language,
2101 "transparent enums are unstable",
2104 if adt.variants.len() != 1 {
2105 bad_variant_count(tcx, adt, sp, def_id);
2106 if adt.variants.is_empty() {
2107 // Don't bother checking the fields. No variants (and thus no fields) exist.
2113 if adt.is_union() && !tcx.features().transparent_unions {
2114 emit_feature_err(&tcx.sess.parse_sess,
2115 sym::transparent_unions,
2117 GateIssue::Language,
2118 "transparent unions are unstable");
2121 // For each field, figure out if it's known to be a ZST and align(1)
2122 let field_infos = adt.all_fields().map(|field| {
2123 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2124 let param_env = tcx.param_env(field.did);
2125 let layout = tcx.layout_of(param_env.and(ty));
2126 // We are currently checking the type this field came from, so it must be local
2127 let span = tcx.hir().span_if_local(field.did).unwrap();
2128 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2129 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2133 let non_zst_fields = field_infos.clone().filter_map(|(span, zst, _align1)| if !zst {
2138 let non_zst_count = non_zst_fields.clone().count();
2139 if non_zst_count != 1 {
2140 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2142 for (span, zst, align1) in field_infos {
2148 "zero-sized field in transparent {} has alignment larger than 1",
2150 ).span_label(span, "has alignment larger than 1").emit();
2155 #[allow(trivial_numeric_casts)]
2156 pub fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, vs: &'tcx [hir::Variant], id: hir::HirId) {
2157 let def_id = tcx.hir().local_def_id(id);
2158 let def = tcx.adt_def(def_id);
2159 def.destructor(tcx); // force the destructor to be evaluated
2162 let attributes = tcx.get_attrs(def_id);
2163 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2165 tcx.sess, attr.span, E0084,
2166 "unsupported representation for zero-variant enum")
2167 .span_label(sp, "zero-variant enum")
2172 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2173 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2174 if !tcx.features().repr128 {
2175 emit_feature_err(&tcx.sess.parse_sess,
2178 GateIssue::Language,
2179 "repr with 128-bit type is unstable");
2184 if let Some(ref e) = v.disr_expr {
2185 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2189 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2191 |var: &hir::Variant| match var.data {
2192 hir::VariantData::Unit(..) => true,
2196 let has_disr = |var: &hir::Variant| var.disr_expr.is_some();
2197 let has_non_units = vs.iter().any(|var| !is_unit(var));
2198 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2199 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2201 if disr_non_unit || (disr_units && has_non_units) {
2202 let mut err = struct_span_err!(tcx.sess, sp, E0732,
2203 "`#[repr(inttype)]` must be specified");
2208 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2209 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2210 // Check for duplicate discriminant values
2211 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2212 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2213 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2214 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2215 let i_span = match variant_i.disr_expr {
2216 Some(ref expr) => tcx.hir().span(expr.hir_id),
2217 None => tcx.hir().span(variant_i_hir_id)
2219 let span = match v.disr_expr {
2220 Some(ref expr) => tcx.hir().span(expr.hir_id),
2223 struct_span_err!(tcx.sess, span, E0081,
2224 "discriminant value `{}` already exists", disr_vals[i])
2225 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2226 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
2229 disr_vals.push(discr);
2232 check_representable(tcx, sp, def_id);
2233 check_transparent(tcx, sp, def_id);
2236 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span, qpath: &QPath) {
2237 span_err!(tcx.sess, span, E0533,
2238 "expected unit struct/variant or constant, found {} `{}`",
2240 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
2243 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2244 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2248 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2250 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2251 let item_id = tcx.hir().ty_param_owner(hir_id);
2252 let item_def_id = tcx.hir().local_def_id(item_id);
2253 let generics = tcx.generics_of(item_def_id);
2254 let index = generics.param_def_id_to_index[&def_id];
2255 ty::GenericPredicates {
2257 predicates: tcx.arena.alloc_from_iter(
2258 self.param_env.caller_bounds.iter().filter_map(|&predicate| match predicate {
2259 ty::Predicate::Trait(ref data)
2260 if data.skip_binder().self_ty().is_param(index) => {
2261 // HACK(eddyb) should get the original `Span`.
2262 let span = tcx.def_span(def_id);
2263 Some((predicate, span))
2273 def: Option<&ty::GenericParamDef>,
2275 ) -> Option<ty::Region<'tcx>> {
2277 Some(def) => infer::EarlyBoundRegion(span, def.name),
2278 None => infer::MiscVariable(span)
2280 Some(self.next_region_var(v))
2283 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2284 if let Some(param) = param {
2285 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2290 self.next_ty_var(TypeVariableOrigin {
2291 kind: TypeVariableOriginKind::TypeInference,
2300 param: Option<&ty::GenericParamDef>,
2302 ) -> &'tcx Const<'tcx> {
2303 if let Some(param) = param {
2304 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2309 self.next_const_var(ty, ConstVariableOrigin {
2310 kind: ConstVariableOriginKind::ConstInference,
2316 fn projected_ty_from_poly_trait_ref(&self,
2319 poly_trait_ref: ty::PolyTraitRef<'tcx>)
2322 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2324 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2328 self.tcx().mk_projection(item_def_id, trait_ref.substs)
2331 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2332 if ty.has_escaping_bound_vars() {
2333 ty // FIXME: normalization and escaping regions
2335 self.normalize_associated_types_in(span, &ty)
2339 fn set_tainted_by_errors(&self) {
2340 self.infcx.set_tainted_by_errors()
2343 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2344 self.write_ty(hir_id, ty)
2348 /// Controls whether the arguments are tupled. This is used for the call
2351 /// Tupling means that all call-side arguments are packed into a tuple and
2352 /// passed as a single parameter. For example, if tupling is enabled, this
2355 /// fn f(x: (isize, isize))
2357 /// Can be called as:
2364 #[derive(Clone, Eq, PartialEq)]
2365 enum TupleArgumentsFlag {
2370 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2372 inh: &'a Inherited<'a, 'tcx>,
2373 param_env: ty::ParamEnv<'tcx>,
2374 body_id: hir::HirId,
2375 ) -> FnCtxt<'a, 'tcx> {
2379 err_count_on_creation: inh.tcx.sess.err_count(),
2381 ret_coercion_span: RefCell::new(None),
2383 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2384 hir::CRATE_HIR_ID)),
2385 diverges: Cell::new(Diverges::Maybe),
2386 has_errors: Cell::new(false),
2387 enclosing_breakables: RefCell::new(EnclosingBreakables {
2389 by_id: Default::default(),
2395 pub fn sess(&self) -> &Session {
2399 pub fn errors_reported_since_creation(&self) -> bool {
2400 self.tcx.sess.err_count() > self.err_count_on_creation
2403 /// Produces warning on the given node, if the current point in the
2404 /// function is unreachable, and there hasn't been another warning.
2405 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2406 // FIXME: Combine these two 'if' expressions into one once
2407 // let chains are implemented
2408 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2409 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2410 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2411 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2412 if !span.is_desugaring(DesugaringKind::CondTemporary) &&
2413 !span.is_desugaring(DesugaringKind::Async) &&
2414 !orig_span.is_desugaring(DesugaringKind::Await)
2416 self.diverges.set(Diverges::WarnedAlways);
2418 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2420 let msg = format!("unreachable {}", kind);
2421 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2422 .span_label(span, &msg)
2425 custom_note.unwrap_or("any code following this expression is unreachable"),
2434 code: ObligationCauseCode<'tcx>)
2435 -> ObligationCause<'tcx> {
2436 ObligationCause::new(span, self.body_id, code)
2439 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2440 self.cause(span, ObligationCauseCode::MiscObligation)
2443 /// Resolves type variables in `ty` if possible. Unlike the infcx
2444 /// version (resolve_vars_if_possible), this version will
2445 /// also select obligations if it seems useful, in an effort
2446 /// to get more type information.
2447 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2448 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2450 // No Infer()? Nothing needs doing.
2451 if !ty.has_infer_types() {
2452 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2456 // If `ty` is a type variable, see whether we already know what it is.
2457 ty = self.resolve_vars_if_possible(&ty);
2458 if !ty.has_infer_types() {
2459 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2463 // If not, try resolving pending obligations as much as
2464 // possible. This can help substantially when there are
2465 // indirect dependencies that don't seem worth tracking
2467 self.select_obligations_where_possible(false, |_| {});
2468 ty = self.resolve_vars_if_possible(&ty);
2470 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2474 fn record_deferred_call_resolution(
2476 closure_def_id: DefId,
2477 r: DeferredCallResolution<'tcx>,
2479 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2480 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2483 fn remove_deferred_call_resolutions(
2485 closure_def_id: DefId,
2486 ) -> Vec<DeferredCallResolution<'tcx>> {
2487 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2488 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2491 pub fn tag(&self) -> String {
2492 format!("{:p}", self)
2495 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2496 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2497 span_bug!(span, "no type for local variable {}",
2498 self.tcx.hir().node_to_string(nid))
2503 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2504 debug!("write_ty({:?}, {:?}) in fcx {}",
2505 id, self.resolve_vars_if_possible(&ty), self.tag());
2506 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2508 if ty.references_error() {
2509 self.has_errors.set(true);
2510 self.set_tainted_by_errors();
2514 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2515 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2518 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2519 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2522 pub fn write_method_call(&self,
2524 method: MethodCallee<'tcx>) {
2525 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2526 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2527 self.write_substs(hir_id, method.substs);
2529 // When the method is confirmed, the `method.substs` includes
2530 // parameters from not just the method, but also the impl of
2531 // the method -- in particular, the `Self` type will be fully
2532 // resolved. However, those are not something that the "user
2533 // specified" -- i.e., those types come from the inferred type
2534 // of the receiver, not something the user wrote. So when we
2535 // create the user-substs, we want to replace those earlier
2536 // types with just the types that the user actually wrote --
2537 // that is, those that appear on the *method itself*.
2539 // As an example, if the user wrote something like
2540 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2541 // type of `foo` (possibly adjusted), but we don't want to
2542 // include that. We want just the `[_, u32]` part.
2543 if !method.substs.is_noop() {
2544 let method_generics = self.tcx.generics_of(method.def_id);
2545 if !method_generics.params.is_empty() {
2546 let user_type_annotation = self.infcx.probe(|_| {
2547 let user_substs = UserSubsts {
2548 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2549 let i = param.index as usize;
2550 if i < method_generics.parent_count {
2551 self.infcx.var_for_def(DUMMY_SP, param)
2556 user_self_ty: None, // not relevant here
2559 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2565 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2566 self.write_user_type_annotation(hir_id, user_type_annotation);
2571 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2572 if !substs.is_noop() {
2573 debug!("write_substs({:?}, {:?}) in fcx {}",
2578 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2582 /// Given the substs that we just converted from the HIR, try to
2583 /// canonicalize them and store them as user-given substitutions
2584 /// (i.e., substitutions that must be respected by the NLL check).
2586 /// This should be invoked **before any unifications have
2587 /// occurred**, so that annotations like `Vec<_>` are preserved
2589 pub fn write_user_type_annotation_from_substs(
2593 substs: SubstsRef<'tcx>,
2594 user_self_ty: Option<UserSelfTy<'tcx>>,
2597 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2598 user_self_ty={:?} in fcx {}",
2599 hir_id, def_id, substs, user_self_ty, self.tag(),
2602 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2603 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2604 &UserType::TypeOf(def_id, UserSubsts {
2609 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2610 self.write_user_type_annotation(hir_id, canonicalized);
2614 pub fn write_user_type_annotation(
2617 canonical_user_type_annotation: CanonicalUserType<'tcx>,
2620 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2621 hir_id, canonical_user_type_annotation, self.tag(),
2624 if !canonical_user_type_annotation.is_identity() {
2625 self.tables.borrow_mut().user_provided_types_mut().insert(
2626 hir_id, canonical_user_type_annotation
2629 debug!("write_user_type_annotation: skipping identity substs");
2633 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2634 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2640 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2641 Entry::Vacant(entry) => { entry.insert(adj); },
2642 Entry::Occupied(mut entry) => {
2643 debug!(" - composing on top of {:?}", entry.get());
2644 match (&entry.get()[..], &adj[..]) {
2645 // Applying any adjustment on top of a NeverToAny
2646 // is a valid NeverToAny adjustment, because it can't
2648 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2650 Adjustment { kind: Adjust::Deref(_), .. },
2651 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2653 Adjustment { kind: Adjust::Deref(_), .. },
2654 .. // Any following adjustments are allowed.
2656 // A reborrow has no effect before a dereference.
2658 // FIXME: currently we never try to compose autoderefs
2659 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2661 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2662 expr, entry.get(), adj)
2664 *entry.get_mut() = adj;
2669 /// Basically whenever we are converting from a type scheme into
2670 /// the fn body space, we always want to normalize associated
2671 /// types as well. This function combines the two.
2672 fn instantiate_type_scheme<T>(&self,
2674 substs: SubstsRef<'tcx>,
2677 where T : TypeFoldable<'tcx>
2679 let value = value.subst(self.tcx, substs);
2680 let result = self.normalize_associated_types_in(span, &value);
2681 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2688 /// As `instantiate_type_scheme`, but for the bounds found in a
2689 /// generic type scheme.
2690 fn instantiate_bounds(
2694 substs: SubstsRef<'tcx>,
2695 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
2696 let bounds = self.tcx.predicates_of(def_id);
2697 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
2698 let result = bounds.instantiate(self.tcx, substs);
2699 let result = self.normalize_associated_types_in(span, &result);
2701 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
2710 /// Replaces the opaque types from the given value with type variables,
2711 /// and records the `OpaqueTypeMap` for later use during writeback. See
2712 /// `InferCtxt::instantiate_opaque_types` for more details.
2713 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2715 parent_id: hir::HirId,
2719 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2720 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2724 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2725 self.instantiate_opaque_types(
2734 let mut opaque_types = self.opaque_types.borrow_mut();
2735 for (ty, decl) in opaque_type_map {
2736 let old_value = opaque_types.insert(ty, decl);
2737 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2743 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2744 where T : TypeFoldable<'tcx>
2746 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2749 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2751 where T : TypeFoldable<'tcx>
2753 self.inh.partially_normalize_associated_types_in(span,
2759 pub fn require_type_meets(&self,
2762 code: traits::ObligationCauseCode<'tcx>,
2765 self.register_bound(
2768 traits::ObligationCause::new(span, self.body_id, code));
2771 pub fn require_type_is_sized(
2775 code: traits::ObligationCauseCode<'tcx>,
2777 if !ty.references_error() {
2778 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
2779 self.require_type_meets(ty, span, code, lang_item);
2783 pub fn require_type_is_sized_deferred(
2787 code: traits::ObligationCauseCode<'tcx>,
2789 if !ty.references_error() {
2790 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2794 pub fn register_bound(
2798 cause: traits::ObligationCause<'tcx>,
2800 if !ty.references_error() {
2801 self.fulfillment_cx.borrow_mut()
2802 .register_bound(self, self.param_env, ty, def_id, cause);
2806 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2807 let t = AstConv::ast_ty_to_ty(self, ast_t);
2808 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2812 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2813 let ty = self.to_ty(ast_ty);
2814 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2816 if Self::can_contain_user_lifetime_bounds(ty) {
2817 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
2818 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2819 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2825 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
2826 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
2827 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
2830 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
2831 AstConv::ast_const_to_const(self, ast_c, ty)
2834 // If the type given by the user has free regions, save it for later, since
2835 // NLL would like to enforce those. Also pass in types that involve
2836 // projections, since those can resolve to `'static` bounds (modulo #54940,
2837 // which hopefully will be fixed by the time you see this comment, dear
2838 // reader, although I have my doubts). Also pass in types with inference
2839 // types, because they may be repeated. Other sorts of things are already
2840 // sufficiently enforced with erased regions. =)
2841 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
2843 T: TypeFoldable<'tcx>
2845 t.has_free_regions() || t.has_projections() || t.has_infer_types()
2848 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2849 match self.tables.borrow().node_types().get(id) {
2851 None if self.is_tainted_by_errors() => self.tcx.types.err,
2853 bug!("no type for node {}: {} in fcx {}",
2854 id, self.tcx.hir().node_to_string(id),
2860 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2861 /// outlive the region `r`.
2862 pub fn register_wf_obligation(
2866 code: traits::ObligationCauseCode<'tcx>,
2868 // WF obligations never themselves fail, so no real need to give a detailed cause:
2869 let cause = traits::ObligationCause::new(span, self.body_id, code);
2870 self.register_predicate(
2871 traits::Obligation::new(cause, self.param_env, ty::Predicate::WellFormed(ty)),
2875 /// Registers obligations that all types appearing in `substs` are well-formed.
2876 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr) {
2877 for ty in substs.types() {
2878 if !ty.references_error() {
2879 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2884 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2885 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2886 /// trait/region obligations.
2888 /// For example, if there is a function:
2891 /// fn foo<'a,T:'a>(...)
2894 /// and a reference:
2900 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2901 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2902 pub fn add_obligations_for_parameters(&self,
2903 cause: traits::ObligationCause<'tcx>,
2904 predicates: &ty::InstantiatedPredicates<'tcx>)
2906 assert!(!predicates.has_escaping_bound_vars());
2908 debug!("add_obligations_for_parameters(predicates={:?})",
2911 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2912 self.register_predicate(obligation);
2916 // FIXME(arielb1): use this instead of field.ty everywhere
2917 // Only for fields! Returns <none> for methods>
2918 // Indifferent to privacy flags
2922 field: &'tcx ty::FieldDef,
2923 substs: SubstsRef<'tcx>,
2925 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2928 fn check_casts(&self) {
2929 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2930 for cast in deferred_cast_checks.drain(..) {
2935 fn resolve_generator_interiors(&self, def_id: DefId) {
2936 let mut generators = self.deferred_generator_interiors.borrow_mut();
2937 for (body_id, interior, kind) in generators.drain(..) {
2938 self.select_obligations_where_possible(false, |_| {});
2939 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
2943 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2944 // Non-numerics get replaced with ! or () (depending on whether
2945 // feature(never_type) is enabled, unconstrained ints with i32,
2946 // unconstrained floats with f64.
2947 // Fallback becomes very dubious if we have encountered type-checking errors.
2948 // In that case, fallback to Error.
2949 // The return value indicates whether fallback has occurred.
2950 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2951 use rustc::ty::error::UnconstrainedNumeric::Neither;
2952 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2954 assert!(ty.is_ty_infer());
2955 let fallback = match self.type_is_unconstrained_numeric(ty) {
2956 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2957 UnconstrainedInt => self.tcx.types.i32,
2958 UnconstrainedFloat => self.tcx.types.f64,
2959 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2960 Neither => return false,
2962 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
2963 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2967 fn select_all_obligations_or_error(&self) {
2968 debug!("select_all_obligations_or_error");
2969 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2970 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2974 /// Select as many obligations as we can at present.
2975 fn select_obligations_where_possible(
2977 fallback_has_occurred: bool,
2978 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
2980 if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2981 mutate_fullfillment_errors(&mut errors);
2982 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2986 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2987 /// returns a type of `&T`, but the actual type we assign to the
2988 /// *expression* is `T`. So this function just peels off the return
2989 /// type by one layer to yield `T`.
2990 fn make_overloaded_place_return_type(&self,
2991 method: MethodCallee<'tcx>)
2992 -> ty::TypeAndMut<'tcx>
2994 // extract method return type, which will be &T;
2995 let ret_ty = method.sig.output();
2997 // method returns &T, but the type as visible to user is T, so deref
2998 ret_ty.builtin_deref(true).unwrap()
3004 base_expr: &'tcx hir::Expr,
3008 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3009 // FIXME(#18741) -- this is almost but not quite the same as the
3010 // autoderef that normal method probing does. They could likely be
3013 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3014 let mut result = None;
3015 while result.is_none() && autoderef.next().is_some() {
3016 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3018 autoderef.finalize(self);
3022 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3023 /// (and otherwise adjust) `base_expr`, looking for a type which either
3024 /// supports builtin indexing or overloaded indexing.
3025 /// This loop implements one step in that search; the autoderef loop
3026 /// is implemented by `lookup_indexing`.
3030 base_expr: &hir::Expr,
3031 autoderef: &Autoderef<'a, 'tcx>,
3034 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3035 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3036 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3043 for &unsize in &[false, true] {
3044 let mut self_ty = adjusted_ty;
3046 // We only unsize arrays here.
3047 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3048 self_ty = self.tcx.mk_slice(element_ty);
3054 // If some lookup succeeds, write callee into table and extract index/element
3055 // type from the method signature.
3056 // If some lookup succeeded, install method in table
3057 let input_ty = self.next_ty_var(TypeVariableOrigin {
3058 kind: TypeVariableOriginKind::AutoDeref,
3059 span: base_expr.span,
3061 let method = self.try_overloaded_place_op(
3062 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
3064 let result = method.map(|ok| {
3065 debug!("try_index_step: success, using overloaded indexing");
3066 let method = self.register_infer_ok_obligations(ok);
3068 let mut adjustments = autoderef.adjust_steps(self, needs);
3069 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3070 let mutbl = match r_mutbl {
3071 hir::MutImmutable => AutoBorrowMutability::Immutable,
3072 hir::MutMutable => AutoBorrowMutability::Mutable {
3073 // Indexing can be desugared to a method call,
3074 // so maybe we could use two-phase here.
3075 // See the documentation of AllowTwoPhase for why that's
3076 // not the case today.
3077 allow_two_phase_borrow: AllowTwoPhase::No,
3080 adjustments.push(Adjustment {
3081 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3082 target: self.tcx.mk_ref(region, ty::TypeAndMut {
3089 adjustments.push(Adjustment {
3090 kind: Adjust::Pointer(PointerCast::Unsize),
3091 target: method.sig.inputs()[0]
3094 self.apply_adjustments(base_expr, adjustments);
3096 self.write_method_call(expr.hir_id, method);
3097 (input_ty, self.make_overloaded_place_return_type(method).ty)
3099 if result.is_some() {
3107 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3108 let (tr, name) = match (op, is_mut) {
3109 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3110 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3111 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3112 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3114 (tr, ast::Ident::with_dummy_span(name))
3117 fn try_overloaded_place_op(&self,
3120 arg_tys: &[Ty<'tcx>],
3123 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
3125 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
3131 // Try Mut first, if needed.
3132 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3133 let method = match (needs, mut_tr) {
3134 (Needs::MutPlace, Some(trait_did)) => {
3135 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3140 // Otherwise, fall back to the immutable version.
3141 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3142 let method = match (method, imm_tr) {
3143 (None, Some(trait_did)) => {
3144 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3146 (method, _) => method,
3152 fn check_method_argument_types(
3155 expr: &'tcx hir::Expr,
3156 method: Result<MethodCallee<'tcx>, ()>,
3157 args_no_rcvr: &'tcx [hir::Expr],
3158 tuple_arguments: TupleArgumentsFlag,
3159 expected: Expectation<'tcx>,
3162 let has_error = match method {
3164 method.substs.references_error() || method.sig.references_error()
3169 let err_inputs = self.err_args(args_no_rcvr.len());
3171 let err_inputs = match tuple_arguments {
3172 DontTupleArguments => err_inputs,
3173 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3176 self.check_argument_types(
3186 return self.tcx.types.err;
3189 let method = method.unwrap();
3190 // HACK(eddyb) ignore self in the definition (see above).
3191 let expected_arg_tys = self.expected_inputs_for_expected_output(
3194 method.sig.output(),
3195 &method.sig.inputs()[1..]
3197 self.check_argument_types(
3200 &method.sig.inputs()[1..],
3201 &expected_arg_tys[..],
3203 method.sig.c_variadic,
3205 self.tcx.hir().span_if_local(method.def_id),
3210 fn self_type_matches_expected_vid(
3212 trait_ref: ty::PolyTraitRef<'tcx>,
3213 expected_vid: ty::TyVid,
3215 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3217 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3218 trait_ref, self_ty, expected_vid
3220 match self_ty.kind {
3221 ty::Infer(ty::TyVar(found_vid)) => {
3222 // FIXME: consider using `sub_root_var` here so we
3223 // can see through subtyping.
3224 let found_vid = self.root_var(found_vid);
3225 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3226 expected_vid == found_vid
3232 fn obligations_for_self_ty<'b>(
3235 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3238 // FIXME: consider using `sub_root_var` here so we
3239 // can see through subtyping.
3240 let ty_var_root = self.root_var(self_ty);
3241 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3242 self_ty, ty_var_root,
3243 self.fulfillment_cx.borrow().pending_obligations());
3247 .pending_obligations()
3249 .filter_map(move |obligation| match obligation.predicate {
3250 ty::Predicate::Projection(ref data) =>
3251 Some((data.to_poly_trait_ref(self.tcx), obligation)),
3252 ty::Predicate::Trait(ref data) =>
3253 Some((data.to_poly_trait_ref(), obligation)),
3254 ty::Predicate::Subtype(..) => None,
3255 ty::Predicate::RegionOutlives(..) => None,
3256 ty::Predicate::TypeOutlives(..) => None,
3257 ty::Predicate::WellFormed(..) => None,
3258 ty::Predicate::ObjectSafe(..) => None,
3259 ty::Predicate::ConstEvaluatable(..) => None,
3260 // N.B., this predicate is created by breaking down a
3261 // `ClosureType: FnFoo()` predicate, where
3262 // `ClosureType` represents some `Closure`. It can't
3263 // possibly be referring to the current closure,
3264 // because we haven't produced the `Closure` for
3265 // this closure yet; this is exactly why the other
3266 // code is looking for a self type of a unresolved
3267 // inference variable.
3268 ty::Predicate::ClosureKind(..) => None,
3269 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3272 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3273 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
3274 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
3278 /// Generic function that factors out common logic from function calls,
3279 /// method calls and overloaded operators.
3280 fn check_argument_types(
3283 expr: &'tcx hir::Expr,
3284 fn_inputs: &[Ty<'tcx>],
3285 expected_arg_tys: &[Ty<'tcx>],
3286 args: &'tcx [hir::Expr],
3288 tuple_arguments: TupleArgumentsFlag,
3289 def_span: Option<Span>,
3292 // Grab the argument types, supplying fresh type variables
3293 // if the wrong number of arguments were supplied
3294 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
3300 // All the input types from the fn signature must outlive the call
3301 // so as to validate implied bounds.
3302 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3303 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3306 let expected_arg_count = fn_inputs.len();
3308 let param_count_error = |expected_count: usize,
3313 let mut err = tcx.sess.struct_span_err_with_code(sp,
3314 &format!("this function takes {}{} but {} {} supplied",
3315 if c_variadic { "at least " } else { "" },
3316 potentially_plural_count(expected_count, "parameter"),
3317 potentially_plural_count(arg_count, "parameter"),
3318 if arg_count == 1 {"was"} else {"were"}),
3319 DiagnosticId::Error(error_code.to_owned()));
3321 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3322 err.span_label(def_s, "defined here");
3325 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3326 // remove closing `)` from the span
3327 let sugg_span = sugg_span.shrink_to_lo();
3328 err.span_suggestion(
3330 "expected the unit value `()`; create it with empty parentheses",
3332 Applicability::MachineApplicable);
3334 err.span_label(sp, format!("expected {}{}",
3335 if c_variadic { "at least " } else { "" },
3336 potentially_plural_count(expected_count, "parameter")));
3341 let mut expected_arg_tys = expected_arg_tys.to_vec();
3343 let formal_tys = if tuple_arguments == TupleArguments {
3344 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3345 match tuple_type.kind {
3346 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3347 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3348 expected_arg_tys = vec![];
3349 self.err_args(args.len())
3351 ty::Tuple(arg_types) => {
3352 expected_arg_tys = match expected_arg_tys.get(0) {
3353 Some(&ty) => match ty.kind {
3354 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3359 arg_types.iter().map(|k| k.expect_ty()).collect()
3362 span_err!(tcx.sess, sp, E0059,
3363 "cannot use call notation; the first type parameter \
3364 for the function trait is neither a tuple nor unit");
3365 expected_arg_tys = vec![];
3366 self.err_args(args.len())
3369 } else if expected_arg_count == supplied_arg_count {
3371 } else if c_variadic {
3372 if supplied_arg_count >= expected_arg_count {
3375 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3376 expected_arg_tys = vec![];
3377 self.err_args(supplied_arg_count)
3380 // is the missing argument of type `()`?
3381 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3382 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3383 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3384 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3388 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3390 expected_arg_tys = vec![];
3391 self.err_args(supplied_arg_count)
3394 debug!("check_argument_types: formal_tys={:?}",
3395 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
3397 // If there is no expectation, expect formal_tys.
3398 let expected_arg_tys = if !expected_arg_tys.is_empty() {
3404 let mut final_arg_types: Vec<(usize, Ty<'_>)> = vec![];
3406 // Check the arguments.
3407 // We do this in a pretty awful way: first we type-check any arguments
3408 // that are not closures, then we type-check the closures. This is so
3409 // that we have more information about the types of arguments when we
3410 // type-check the functions. This isn't really the right way to do this.
3411 for &check_closures in &[false, true] {
3412 debug!("check_closures={}", check_closures);
3414 // More awful hacks: before we check argument types, try to do
3415 // an "opportunistic" vtable resolution of any trait bounds on
3416 // the call. This helps coercions.
3418 self.select_obligations_where_possible(false, |errors| {
3419 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
3420 self.point_at_arg_instead_of_call_if_possible(
3422 &final_arg_types[..],
3429 // For C-variadic functions, we don't have a declared type for all of
3430 // the arguments hence we only do our usual type checking with
3431 // the arguments who's types we do know.
3432 let t = if c_variadic {
3434 } else if tuple_arguments == TupleArguments {
3439 for (i, arg) in args.iter().take(t).enumerate() {
3440 // Warn only for the first loop (the "no closures" one).
3441 // Closure arguments themselves can't be diverging, but
3442 // a previous argument can, e.g., `foo(panic!(), || {})`.
3443 if !check_closures {
3444 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3447 let is_closure = match arg.kind {
3448 ExprKind::Closure(..) => true,
3452 if is_closure != check_closures {
3456 debug!("checking the argument");
3457 let formal_ty = formal_tys[i];
3459 // The special-cased logic below has three functions:
3460 // 1. Provide as good of an expected type as possible.
3461 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3463 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3465 // 2. Coerce to the most detailed type that could be coerced
3466 // to, which is `expected_ty` if `rvalue_hint` returns an
3467 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3468 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3469 // We're processing function arguments so we definitely want to use
3470 // two-phase borrows.
3471 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3472 final_arg_types.push((i, coerce_ty));
3474 // 3. Relate the expected type and the formal one,
3475 // if the expected type was used for the coercion.
3476 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3480 // We also need to make sure we at least write the ty of the other
3481 // arguments which we skipped above.
3483 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3484 use crate::structured_errors::{VariadicError, StructuredDiagnostic};
3485 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3488 for arg in args.iter().skip(expected_arg_count) {
3489 let arg_ty = self.check_expr(&arg);
3491 // There are a few types which get autopromoted when passed via varargs
3492 // in C but we just error out instead and require explicit casts.
3493 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3495 ty::Float(ast::FloatTy::F32) => {
3496 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3498 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3499 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3501 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3502 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3505 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3506 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3507 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3515 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3516 vec![self.tcx.types.err; len]
3519 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call argument expressions, we
3520 /// walk the resolved types for each argument to see if any of the `FullfillmentError`s
3521 /// reference a type argument. If they do, and there's only *one* argument that does, we point
3522 /// at the corresponding argument's expression span instead of the `fn` call path span.
3523 fn point_at_arg_instead_of_call_if_possible(
3525 errors: &mut Vec<traits::FulfillmentError<'_>>,
3526 final_arg_types: &[(usize, Ty<'tcx>)],
3528 args: &'tcx [hir::Expr],
3530 if !call_sp.desugaring_kind().is_some() {
3531 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3532 // the `?` operator.
3533 for error in errors {
3534 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3535 // Collect the argument position for all arguments that could have caused this
3536 // `FullfillmentError`.
3537 let mut referenced_in = final_arg_types.iter()
3538 .flat_map(|(i, ty)| {
3539 let ty = self.resolve_vars_if_possible(ty);
3540 // We walk the argument type because the argument's type could have
3541 // been `Option<T>`, but the `FullfillmentError` references `T`.
3543 .filter(|&ty| ty == predicate.skip_binder().self_ty())
3546 if let (Some(ref_in), None) = (referenced_in.next(), referenced_in.next()) {
3547 // We make sure that only *one* argument matches the obligation failure
3548 // and thet the obligation's span to its expression's.
3549 error.obligation.cause.span = args[ref_in].span;
3550 error.points_at_arg_span = true;
3557 /// Given a vec of evaluated `FullfillmentError`s and an `fn` call expression, we walk the
3558 /// `PathSegment`s and resolve their type parameters to see if any of the `FullfillmentError`s
3559 /// were caused by them. If they were, we point at the corresponding type argument's span
3560 /// instead of the `fn` call path span.
3561 fn point_at_type_arg_instead_of_call_if_possible(
3563 errors: &mut Vec<traits::FulfillmentError<'_>>,
3564 call_expr: &'tcx hir::Expr,
3566 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
3567 if let hir::ExprKind::Path(qpath) = &path.kind {
3568 if let hir::QPath::Resolved(_, path) = &qpath {
3569 for error in errors {
3570 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
3571 // If any of the type arguments in this path segment caused the
3572 // `FullfillmentError`, point at its span (#61860).
3573 for arg in path.segments.iter()
3574 .filter_map(|seg| seg.args.as_ref())
3575 .flat_map(|a| a.args.iter())
3577 if let hir::GenericArg::Type(hir_ty) = &arg {
3578 if let hir::TyKind::Path(
3579 hir::QPath::TypeRelative(..),
3581 // Avoid ICE with associated types. As this is best
3582 // effort only, it's ok to ignore the case. It
3583 // would trigger in `is_send::<T::AssocType>();`
3584 // from `typeck-default-trait-impl-assoc-type.rs`.
3586 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
3587 let ty = self.resolve_vars_if_possible(&ty);
3588 if ty == predicate.skip_binder().self_ty() {
3589 error.obligation.cause.span = hir_ty.span;
3601 // AST fragment checking
3604 expected: Expectation<'tcx>)
3610 ast::LitKind::Str(..) => tcx.mk_static_str(),
3611 ast::LitKind::ByteStr(ref v) => {
3612 tcx.mk_imm_ref(tcx.lifetimes.re_static,
3613 tcx.mk_array(tcx.types.u8, v.len() as u64))
3615 ast::LitKind::Byte(_) => tcx.types.u8,
3616 ast::LitKind::Char(_) => tcx.types.char,
3617 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3618 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3619 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3620 let opt_ty = expected.to_option(self).and_then(|ty| {
3622 ty::Int(_) | ty::Uint(_) => Some(ty),
3623 ty::Char => Some(tcx.types.u8),
3624 ty::RawPtr(..) => Some(tcx.types.usize),
3625 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3629 opt_ty.unwrap_or_else(|| self.next_int_var())
3631 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3632 ast::LitKind::FloatUnsuffixed(_) => {
3633 let opt_ty = expected.to_option(self).and_then(|ty| {
3635 ty::Float(_) => Some(ty),
3639 opt_ty.unwrap_or_else(|| self.next_float_var())
3641 ast::LitKind::Bool(_) => tcx.types.bool,
3642 ast::LitKind::Err(_) => tcx.types.err,
3646 // Determine the `Self` type, using fresh variables for all variables
3647 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3648 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3650 pub fn impl_self_ty(&self,
3651 span: Span, // (potential) receiver for this impl
3653 -> TypeAndSubsts<'tcx> {
3654 let ity = self.tcx.type_of(did);
3655 debug!("impl_self_ty: ity={:?}", ity);
3657 let substs = self.fresh_substs_for_item(span, did);
3658 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3660 TypeAndSubsts { substs: substs, ty: substd_ty }
3663 /// Unifies the output type with the expected type early, for more coercions
3664 /// and forward type information on the input expressions.
3665 fn expected_inputs_for_expected_output(&self,
3667 expected_ret: Expectation<'tcx>,
3668 formal_ret: Ty<'tcx>,
3669 formal_args: &[Ty<'tcx>])
3671 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3672 let ret_ty = match expected_ret.only_has_type(self) {
3674 None => return Vec::new()
3676 let expect_args = self.fudge_inference_if_ok(|| {
3677 // Attempt to apply a subtyping relationship between the formal
3678 // return type (likely containing type variables if the function
3679 // is polymorphic) and the expected return type.
3680 // No argument expectations are produced if unification fails.
3681 let origin = self.misc(call_span);
3682 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3684 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3685 // to identity so the resulting type is not constrained.
3688 // Process any obligations locally as much as
3689 // we can. We don't care if some things turn
3690 // out unconstrained or ambiguous, as we're
3691 // just trying to get hints here.
3692 self.save_and_restore_in_snapshot_flag(|_| {
3693 let mut fulfill = TraitEngine::new(self.tcx);
3694 for obligation in ok.obligations {
3695 fulfill.register_predicate_obligation(self, obligation);
3697 fulfill.select_where_possible(self)
3698 }).map_err(|_| ())?;
3700 Err(_) => return Err(()),
3703 // Record all the argument types, with the substitutions
3704 // produced from the above subtyping unification.
3705 Ok(formal_args.iter().map(|ty| {
3706 self.resolve_vars_if_possible(ty)
3708 }).unwrap_or_default();
3709 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3710 formal_args, formal_ret,
3711 expect_args, expected_ret);
3715 pub fn check_struct_path(&self,
3718 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3719 let path_span = match *qpath {
3720 QPath::Resolved(_, ref path) => path.span,
3721 QPath::TypeRelative(ref qself, _) => qself.span
3723 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
3724 let variant = match def {
3726 self.set_tainted_by_errors();
3729 Res::Def(DefKind::Variant, _) => {
3731 ty::Adt(adt, substs) => {
3732 Some((adt.variant_of_res(def), adt.did, substs))
3734 _ => bug!("unexpected type: {:?}", ty)
3737 Res::Def(DefKind::Struct, _)
3738 | Res::Def(DefKind::Union, _)
3739 | Res::Def(DefKind::TyAlias, _)
3740 | Res::Def(DefKind::AssocTy, _)
3741 | Res::SelfTy(..) => {
3743 ty::Adt(adt, substs) if !adt.is_enum() => {
3744 Some((adt.non_enum_variant(), adt.did, substs))
3749 _ => bug!("unexpected definition: {:?}", def)
3752 if let Some((variant, did, substs)) = variant {
3753 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3754 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3756 // Check bounds on type arguments used in the path.
3757 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
3758 let cause = traits::ObligationCause::new(
3761 traits::ItemObligation(did),
3763 self.add_obligations_for_parameters(cause, &bounds);
3767 struct_span_err!(self.tcx.sess, path_span, E0071,
3768 "expected struct, variant or union type, found {}",
3769 ty.sort_string(self.tcx))
3770 .span_label(path_span, "not a struct")
3776 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
3777 // The newly resolved definition is written into `type_dependent_defs`.
3778 fn finish_resolving_struct_path(&self,
3785 QPath::Resolved(ref maybe_qself, ref path) => {
3786 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
3787 let ty = AstConv::res_to_ty(self, self_ty, path, true);
3790 QPath::TypeRelative(ref qself, ref segment) => {
3791 let ty = self.to_ty(qself);
3793 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
3798 let result = AstConv::associated_path_to_ty(
3807 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
3808 let result = result.map(|(_, kind, def_id)| (kind, def_id));
3810 // Write back the new resolution.
3811 self.write_resolution(hir_id, result);
3813 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
3818 /// Resolves an associated value path into a base type and associated constant, or method
3819 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
3820 pub fn resolve_ty_and_res_ufcs<'b>(&self,
3824 -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment])
3826 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
3827 let (ty, qself, item_segment) = match *qpath {
3828 QPath::Resolved(ref opt_qself, ref path) => {
3830 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
3831 &path.segments[..]);
3833 QPath::TypeRelative(ref qself, ref segment) => {
3834 (self.to_ty(qself), qself, segment)
3837 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
3838 // Return directly on cache hit. This is useful to avoid doubly reporting
3839 // errors with default match binding modes. See #44614.
3840 let def = cached_result.map(|(kind, def_id)| Res::Def(kind, def_id))
3841 .unwrap_or(Res::Err);
3842 return (def, Some(ty), slice::from_ref(&**item_segment));
3844 let item_name = item_segment.ident;
3845 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
3846 let result = match error {
3847 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
3848 _ => Err(ErrorReported),
3850 if item_name.name != kw::Invalid {
3851 self.report_method_error(
3855 SelfSource::QPath(qself),
3858 ).map(|mut e| e.emit());
3863 // Write back the new resolution.
3864 self.write_resolution(hir_id, result);
3866 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
3868 slice::from_ref(&**item_segment),
3872 pub fn check_decl_initializer(
3874 local: &'tcx hir::Local,
3875 init: &'tcx hir::Expr,
3877 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
3878 // for #42640 (default match binding modes).
3881 let ref_bindings = local.pat.contains_explicit_ref_binding();
3883 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
3884 if let Some(m) = ref_bindings {
3885 // Somewhat subtle: if we have a `ref` binding in the pattern,
3886 // we want to avoid introducing coercions for the RHS. This is
3887 // both because it helps preserve sanity and, in the case of
3888 // ref mut, for soundness (issue #23116). In particular, in
3889 // the latter case, we need to be clear that the type of the
3890 // referent for the reference that results is *equal to* the
3891 // type of the place it is referencing, and not some
3892 // supertype thereof.
3893 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
3894 self.demand_eqtype(init.span, local_ty, init_ty);
3897 self.check_expr_coercable_to_type(init, local_ty)
3901 pub fn check_decl_local(&self, local: &'tcx hir::Local) {
3902 let t = self.local_ty(local.span, local.hir_id).decl_ty;
3903 self.write_ty(local.hir_id, t);
3905 if let Some(ref init) = local.init {
3906 let init_ty = self.check_decl_initializer(local, &init);
3907 self.overwrite_local_ty_if_err(local, t, init_ty);
3910 self.check_pat_top(&local.pat, t, None);
3911 let pat_ty = self.node_ty(local.pat.hir_id);
3912 self.overwrite_local_ty_if_err(local, t, pat_ty);
3915 fn overwrite_local_ty_if_err(&self, local: &'tcx hir::Local, decl_ty: Ty<'tcx>, ty: Ty<'tcx>) {
3916 if ty.references_error() {
3917 // Override the types everywhere with `types.err` to avoid knock down errors.
3918 self.write_ty(local.hir_id, ty);
3919 self.write_ty(local.pat.hir_id, ty);
3920 let local_ty = LocalTy {
3924 self.locals.borrow_mut().insert(local.hir_id, local_ty);
3925 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
3929 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
3930 err.span_suggestion_short(
3931 span.shrink_to_hi(),
3932 "consider using a semicolon here",
3934 Applicability::MachineApplicable,
3938 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt) {
3939 // Don't do all the complex logic below for `DeclItem`.
3941 hir::StmtKind::Item(..) => return,
3942 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
3945 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
3947 // Hide the outer diverging and `has_errors` flags.
3948 let old_diverges = self.diverges.get();
3949 let old_has_errors = self.has_errors.get();
3950 self.diverges.set(Diverges::Maybe);
3951 self.has_errors.set(false);
3954 hir::StmtKind::Local(ref l) => {
3955 self.check_decl_local(&l);
3958 hir::StmtKind::Item(_) => {}
3959 hir::StmtKind::Expr(ref expr) => {
3960 // Check with expected type of `()`.
3962 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
3963 self.suggest_semicolon_at_end(expr.span, err);
3966 hir::StmtKind::Semi(ref expr) => {
3967 self.check_expr(&expr);
3971 // Combine the diverging and `has_error` flags.
3972 self.diverges.set(self.diverges.get() | old_diverges);
3973 self.has_errors.set(self.has_errors.get() | old_has_errors);
3976 pub fn check_block_no_value(&self, blk: &'tcx hir::Block) {
3977 let unit = self.tcx.mk_unit();
3978 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
3980 // if the block produces a `!` value, that can always be
3981 // (effectively) coerced to unit.
3983 self.demand_suptype(blk.span, unit, ty);
3987 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
3988 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
3989 /// when given code like the following:
3991 /// if false { return 0i32; } else { 1u32 }
3992 /// // ^^^^ point at this instead of the whole `if` expression
3994 fn get_expr_coercion_span(&self, expr: &hir::Expr) -> syntax_pos::Span {
3995 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
3996 let arm_spans: Vec<Span> = arms.iter().filter_map(|arm| {
3997 self.in_progress_tables
3998 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
3999 .and_then(|arm_ty| {
4000 if arm_ty.is_never() {
4003 Some(match &arm.body.kind {
4004 // Point at the tail expression when possible.
4005 hir::ExprKind::Block(block, _) => block.expr
4008 .unwrap_or(block.span),
4014 if arm_spans.len() == 1 {
4015 return arm_spans[0];
4021 fn check_block_with_expected(
4023 blk: &'tcx hir::Block,
4024 expected: Expectation<'tcx>,
4027 let mut fcx_ps = self.ps.borrow_mut();
4028 let unsafety_state = fcx_ps.recurse(blk);
4029 replace(&mut *fcx_ps, unsafety_state)
4032 // In some cases, blocks have just one exit, but other blocks
4033 // can be targeted by multiple breaks. This can happen both
4034 // with labeled blocks as well as when we desugar
4035 // a `try { ... }` expression.
4039 // 'a: { if true { break 'a Err(()); } Ok(()) }
4041 // Here we would wind up with two coercions, one from
4042 // `Err(())` and the other from the tail expression
4043 // `Ok(())`. If the tail expression is omitted, that's a
4044 // "forced unit" -- unless the block diverges, in which
4045 // case we can ignore the tail expression (e.g., `'a: {
4046 // break 'a 22; }` would not force the type of the block
4048 let tail_expr = blk.expr.as_ref();
4049 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4050 let coerce = if blk.targeted_by_break {
4051 CoerceMany::new(coerce_to_ty)
4053 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4054 Some(e) => slice::from_ref(e),
4057 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4060 let prev_diverges = self.diverges.get();
4061 let ctxt = BreakableCtxt {
4062 coerce: Some(coerce),
4066 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4067 for s in &blk.stmts {
4071 // check the tail expression **without** holding the
4072 // `enclosing_breakables` lock below.
4073 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4075 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4076 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4077 let coerce = ctxt.coerce.as_mut().unwrap();
4078 if let Some(tail_expr_ty) = tail_expr_ty {
4079 let tail_expr = tail_expr.unwrap();
4080 let span = self.get_expr_coercion_span(tail_expr);
4081 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4082 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4084 // Subtle: if there is no explicit tail expression,
4085 // that is typically equivalent to a tail expression
4086 // of `()` -- except if the block diverges. In that
4087 // case, there is no value supplied from the tail
4088 // expression (assuming there are no other breaks,
4089 // this implies that the type of the block will be
4092 // #41425 -- label the implicit `()` as being the
4093 // "found type" here, rather than the "expected type".
4094 if !self.diverges.get().is_always() {
4095 // #50009 -- Do not point at the entire fn block span, point at the return type
4096 // span, as it is the cause of the requirement, and
4097 // `consider_hint_about_removing_semicolon` will point at the last expression
4098 // if it were a relevant part of the error. This improves usability in editors
4099 // that highlight errors inline.
4100 let mut sp = blk.span;
4101 let mut fn_span = None;
4102 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4103 let ret_sp = decl.output.span();
4104 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4105 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4106 // output would otherwise be incorrect and even misleading. Make sure
4107 // the span we're aiming at correspond to a `fn` body.
4108 if block_sp == blk.span {
4110 fn_span = Some(ident.span);
4114 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4115 if let Some(expected_ty) = expected.only_has_type(self) {
4116 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4118 if let Some(fn_span) = fn_span {
4121 "implicitly returns `()` as its body has no tail or `return` \
4131 // If we can break from the block, then the block's exit is always reachable
4132 // (... as long as the entry is reachable) - regardless of the tail of the block.
4133 self.diverges.set(prev_diverges);
4136 let mut ty = ctxt.coerce.unwrap().complete(self);
4138 if self.has_errors.get() || ty.references_error() {
4139 ty = self.tcx.types.err
4142 self.write_ty(blk.hir_id, ty);
4144 *self.ps.borrow_mut() = prev;
4148 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4149 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4151 Node::Item(&hir::Item {
4152 kind: hir::ItemKind::Fn(_, _, _, body_id), ..
4154 Node::ImplItem(&hir::ImplItem {
4155 kind: hir::ImplItemKind::Method(_, body_id), ..
4157 let body = self.tcx.hir().body(body_id);
4158 if let ExprKind::Block(block, _) = &body.value.kind {
4159 return Some(block.span);
4167 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4168 fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, ast::Ident)> {
4169 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4170 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4173 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4174 fn get_node_fn_decl(&self, node: Node<'tcx>) -> Option<(&'tcx hir::FnDecl, ast::Ident, bool)> {
4176 Node::Item(&hir::Item {
4177 ident, kind: hir::ItemKind::Fn(ref decl, ..), ..
4179 // This is less than ideal, it will not suggest a return type span on any
4180 // method called `main`, regardless of whether it is actually the entry point,
4181 // but it will still present it as the reason for the expected type.
4182 Some((decl, ident, ident.name != sym::main))
4184 Node::TraitItem(&hir::TraitItem {
4185 ident, kind: hir::TraitItemKind::Method(hir::MethodSig {
4188 }) => Some((decl, ident, true)),
4189 Node::ImplItem(&hir::ImplItem {
4190 ident, kind: hir::ImplItemKind::Method(hir::MethodSig {
4193 }) => Some((decl, ident, false)),
4198 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4199 /// suggestion can be made, `None` otherwise.
4200 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl, bool)> {
4201 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4202 // `while` before reaching it, as block tail returns are not available in them.
4203 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4204 let parent = self.tcx.hir().get(blk_id);
4205 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4209 /// On implicit return expressions with mismatched types, provides the following suggestions:
4211 /// - Points out the method's return type as the reason for the expected type.
4212 /// - Possible missing semicolon.
4213 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4214 pub fn suggest_mismatched_types_on_tail(
4216 err: &mut DiagnosticBuilder<'tcx>,
4217 expr: &'tcx hir::Expr,
4223 let expr = expr.peel_drop_temps();
4224 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4225 let mut pointing_at_return_type = false;
4226 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4227 pointing_at_return_type = self.suggest_missing_return_type(
4228 err, &fn_decl, expected, found, can_suggest);
4230 self.suggest_ref_or_into(err, expr, expected, found);
4231 self.suggest_boxing_when_appropriate(err, expr, expected, found);
4232 pointing_at_return_type
4235 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4236 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4238 /// fn foo(x: usize) -> usize { x }
4239 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4243 err: &mut DiagnosticBuilder<'tcx>,
4248 let hir = self.tcx.hir();
4249 let (def_id, sig) = match found.kind {
4250 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4251 ty::Closure(def_id, substs) => {
4252 // We don't use `closure_sig` to account for malformed closures like
4253 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4254 let closure_sig_ty = substs.as_closure().sig_ty(def_id, self.tcx);
4255 (def_id, match closure_sig_ty.kind {
4256 ty::FnPtr(sig) => sig,
4264 .replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig)
4266 let sig = self.normalize_associated_types_in(expr.span, &sig);
4267 if self.can_coerce(sig.output(), expected) {
4268 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4269 (String::new(), Applicability::MachineApplicable)
4271 ("...".to_string(), Applicability::HasPlaceholders)
4273 let mut msg = "call this function";
4274 match hir.get_if_local(def_id) {
4275 Some(Node::Item(hir::Item {
4276 kind: ItemKind::Fn(.., body_id),
4279 Some(Node::ImplItem(hir::ImplItem {
4280 kind: hir::ImplItemKind::Method(_, body_id),
4283 Some(Node::TraitItem(hir::TraitItem {
4284 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4287 let body = hir.body(*body_id);
4288 sugg_call = body.params.iter()
4289 .map(|param| match ¶m.pat.kind {
4290 hir::PatKind::Binding(_, _, ident, None)
4291 if ident.name != kw::SelfLower => ident.to_string(),
4292 _ => "_".to_string(),
4293 }).collect::<Vec<_>>().join(", ");
4295 Some(Node::Expr(hir::Expr {
4296 kind: ExprKind::Closure(_, _, body_id, closure_span, _),
4297 span: full_closure_span,
4300 if *full_closure_span == expr.span {
4303 err.span_label(*closure_span, "closure defined here");
4304 msg = "call this closure";
4305 let body = hir.body(*body_id);
4306 sugg_call = body.params.iter()
4307 .map(|param| match ¶m.pat.kind {
4308 hir::PatKind::Binding(_, _, ident, None)
4309 if ident.name != kw::SelfLower => ident.to_string(),
4310 _ => "_".to_string(),
4311 }).collect::<Vec<_>>().join(", ");
4313 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4314 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4315 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4316 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4317 msg = "instantiate this tuple variant";
4319 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4320 msg = "instantiate this tuple struct";
4325 Some(Node::ForeignItem(hir::ForeignItem {
4326 kind: hir::ForeignItemKind::Fn(_, idents, _),
4329 Some(Node::TraitItem(hir::TraitItem {
4330 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4332 })) => sugg_call = idents.iter()
4333 .map(|ident| if ident.name != kw::SelfLower {
4337 }).collect::<Vec<_>>()
4341 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4342 err.span_suggestion(
4344 &format!("use parentheses to {}", msg),
4345 format!("{}({})", code, sugg_call),
4354 pub fn suggest_ref_or_into(
4356 err: &mut DiagnosticBuilder<'tcx>,
4361 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4362 err.span_suggestion(
4366 Applicability::MachineApplicable,
4368 } else if let (ty::FnDef(def_id, ..), true) = (
4370 self.suggest_fn_call(err, expr, expected, found),
4372 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4373 let sp = self.sess().source_map().def_span(sp);
4374 err.span_label(sp, &format!("{} defined here", found));
4376 } else if !self.check_for_cast(err, expr, found, expected) {
4377 let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
4381 let methods = self.get_conversion_methods(expr.span, expected, found);
4382 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4383 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
4384 .filter_map(|(receiver, method)| {
4385 let method_call = format!(".{}()", method.ident);
4386 if receiver.ends_with(&method_call) {
4387 None // do not suggest code that is already there (#53348)
4389 let method_call_list = [".to_vec()", ".to_string()"];
4390 let sugg = if receiver.ends_with(".clone()")
4391 && method_call_list.contains(&method_call.as_str()) {
4392 let max_len = receiver.rfind(".").unwrap();
4393 format!("{}{}", &receiver[..max_len], method_call)
4395 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
4396 format!("({}){}", receiver, method_call)
4398 format!("{}{}", receiver, method_call)
4401 Some(if is_struct_pat_shorthand_field {
4402 format!("{}: {}", receiver, sugg)
4408 if suggestions.peek().is_some() {
4409 err.span_suggestions(
4411 "try using a conversion method",
4413 Applicability::MaybeIncorrect,
4420 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4421 /// in the heap by calling `Box::new()`.
4422 fn suggest_boxing_when_appropriate(
4424 err: &mut DiagnosticBuilder<'tcx>,
4429 if self.tcx.hir().is_const_context(expr.hir_id) {
4430 // Do not suggest `Box::new` in const context.
4433 if !expected.is_box() || found.is_box() {
4436 let boxed_found = self.tcx.mk_box(found);
4437 if let (true, Ok(snippet)) = (
4438 self.can_coerce(boxed_found, expected),
4439 self.sess().source_map().span_to_snippet(expr.span),
4441 err.span_suggestion(
4443 "store this in the heap by calling `Box::new`",
4444 format!("Box::new({})", snippet),
4445 Applicability::MachineApplicable,
4447 err.note("for more on the distinction between the stack and the \
4448 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4449 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4450 https://doc.rust-lang.org/std/boxed/index.html");
4455 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4459 /// bar_that_returns_u32()
4463 /// This routine checks if the return expression in a block would make sense on its own as a
4464 /// statement and the return type has been left as default or has been specified as `()`. If so,
4465 /// it suggests adding a semicolon.
4466 fn suggest_missing_semicolon(
4468 err: &mut DiagnosticBuilder<'tcx>,
4469 expression: &'tcx hir::Expr,
4473 if expected.is_unit() {
4474 // `BlockTailExpression` only relevant if the tail expr would be
4475 // useful on its own.
4476 match expression.kind {
4477 ExprKind::Call(..) |
4478 ExprKind::MethodCall(..) |
4479 ExprKind::Loop(..) |
4480 ExprKind::Match(..) |
4481 ExprKind::Block(..) => {
4482 let sp = self.tcx.sess.source_map().next_point(cause_span);
4483 err.span_suggestion(
4485 "try adding a semicolon",
4487 Applicability::MachineApplicable);
4494 /// A possible error is to forget to add a return type that is needed:
4498 /// bar_that_returns_u32()
4502 /// This routine checks if the return type is left as default, the method is not part of an
4503 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
4505 fn suggest_missing_return_type(
4507 err: &mut DiagnosticBuilder<'tcx>,
4508 fn_decl: &hir::FnDecl,
4513 // Only suggest changing the return type for methods that
4514 // haven't set a return type at all (and aren't `fn main()` or an impl).
4515 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
4516 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
4517 err.span_suggestion(
4519 "try adding a return type",
4520 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
4521 Applicability::MachineApplicable);
4524 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
4525 err.span_label(span, "possibly return type missing here?");
4528 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
4529 // `fn main()` must return `()`, do not suggest changing return type
4530 err.span_label(span, "expected `()` because of default return type");
4533 // expectation was caused by something else, not the default return
4534 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
4535 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
4536 // Only point to return type if the expected type is the return type, as if they
4537 // are not, the expectation must have been caused by something else.
4538 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
4540 let ty = AstConv::ast_ty_to_ty(self, ty);
4541 debug!("suggest_missing_return_type: return type {:?}", ty);
4542 debug!("suggest_missing_return_type: expected type {:?}", ty);
4543 if ty.kind == expected.kind {
4544 err.span_label(sp, format!("expected `{}` because of return type",
4553 /// A possible error is to forget to add `.await` when using futures:
4556 /// async fn make_u32() -> u32 {
4560 /// fn take_u32(x: u32) {}
4562 /// async fn foo() {
4563 /// let x = make_u32();
4568 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
4569 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
4570 /// `.await` to the tail of the expression.
4571 fn suggest_missing_await(
4573 err: &mut DiagnosticBuilder<'tcx>,
4578 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
4579 // body isn't `async`.
4580 let item_id = self.tcx().hir().get_parent_node(self.body_id);
4581 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
4582 let body = self.tcx().hir().body(body_id);
4583 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
4585 // Check for `Future` implementations by constructing a predicate to
4586 // prove: `<T as Future>::Output == U`
4587 let future_trait = self.tcx.lang_items().future_trait().unwrap();
4588 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
4589 let predicate = ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
4590 // `<T as Future>::Output`
4591 projection_ty: ty::ProjectionTy {
4593 substs: self.tcx.mk_substs_trait(
4595 self.fresh_substs_for_item(sp, item_def_id)
4602 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
4603 if self.infcx.predicate_may_hold(&obligation) {
4604 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
4605 err.span_suggestion(
4607 "consider using `.await` here",
4608 format!("{}.await", code),
4609 Applicability::MaybeIncorrect,
4617 /// A common error is to add an extra semicolon:
4620 /// fn foo() -> usize {
4625 /// This routine checks if the final statement in a block is an
4626 /// expression with an explicit semicolon whose type is compatible
4627 /// with `expected_ty`. If so, it suggests removing the semicolon.
4628 fn consider_hint_about_removing_semicolon(
4630 blk: &'tcx hir::Block,
4631 expected_ty: Ty<'tcx>,
4632 err: &mut DiagnosticBuilder<'_>,
4634 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
4635 err.span_suggestion(
4637 "consider removing this semicolon",
4639 Applicability::MachineApplicable,
4644 fn could_remove_semicolon(&self, blk: &'tcx hir::Block, expected_ty: Ty<'tcx>) -> Option<Span> {
4645 // Be helpful when the user wrote `{... expr;}` and
4646 // taking the `;` off is enough to fix the error.
4647 let last_stmt = blk.stmts.last()?;
4648 let last_expr = match last_stmt.kind {
4649 hir::StmtKind::Semi(ref e) => e,
4652 let last_expr_ty = self.node_ty(last_expr.hir_id);
4653 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
4656 let original_span = original_sp(last_stmt.span, blk.span);
4657 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
4660 // Instantiates the given path, which must refer to an item with the given
4661 // number of type parameters and type.
4662 pub fn instantiate_value_path(&self,
4663 segments: &[hir::PathSegment],
4664 self_ty: Option<Ty<'tcx>>,
4668 -> (Ty<'tcx>, Res) {
4670 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
4679 let path_segs = match res {
4680 Res::Local(_) | Res::SelfCtor(_) => vec![],
4681 Res::Def(kind, def_id) =>
4682 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id),
4683 _ => bug!("instantiate_value_path on {:?}", res),
4686 let mut user_self_ty = None;
4687 let mut is_alias_variant_ctor = false;
4689 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
4690 if let Some(self_ty) = self_ty {
4691 let adt_def = self_ty.ty_adt_def().unwrap();
4692 user_self_ty = Some(UserSelfTy {
4693 impl_def_id: adt_def.did,
4696 is_alias_variant_ctor = true;
4699 Res::Def(DefKind::Method, def_id)
4700 | Res::Def(DefKind::AssocConst, def_id) => {
4701 let container = tcx.associated_item(def_id).container;
4702 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
4704 ty::TraitContainer(trait_did) => {
4705 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
4707 ty::ImplContainer(impl_def_id) => {
4708 if segments.len() == 1 {
4709 // `<T>::assoc` will end up here, and so
4710 // can `T::assoc`. It this came from an
4711 // inherent impl, we need to record the
4712 // `T` for posterity (see `UserSelfTy` for
4714 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
4715 user_self_ty = Some(UserSelfTy {
4726 // Now that we have categorized what space the parameters for each
4727 // segment belong to, let's sort out the parameters that the user
4728 // provided (if any) into their appropriate spaces. We'll also report
4729 // errors if type parameters are provided in an inappropriate place.
4731 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
4732 let generics_has_err = AstConv::prohibit_generics(
4733 self, segments.iter().enumerate().filter_map(|(index, seg)| {
4734 if !generic_segs.contains(&index) || is_alias_variant_ctor {
4741 if let Res::Local(hid) = res {
4742 let ty = self.local_ty(span, hid).decl_ty;
4743 let ty = self.normalize_associated_types_in(span, &ty);
4744 self.write_ty(hir_id, ty);
4748 if generics_has_err {
4749 // Don't try to infer type parameters when prohibited generic arguments were given.
4750 user_self_ty = None;
4753 // Now we have to compare the types that the user *actually*
4754 // provided against the types that were *expected*. If the user
4755 // did not provide any types, then we want to substitute inference
4756 // variables. If the user provided some types, we may still need
4757 // to add defaults. If the user provided *too many* types, that's
4760 let mut infer_args_for_err = FxHashSet::default();
4761 for &PathSeg(def_id, index) in &path_segs {
4762 let seg = &segments[index];
4763 let generics = tcx.generics_of(def_id);
4764 // Argument-position `impl Trait` is treated as a normal generic
4765 // parameter internally, but we don't allow users to specify the
4766 // parameter's value explicitly, so we have to do some error-
4768 let suppress_errors = AstConv::check_generic_arg_count_for_call(
4773 false, // `is_method_call`
4775 if suppress_errors {
4776 infer_args_for_err.insert(index);
4777 self.set_tainted_by_errors(); // See issue #53251.
4781 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
4782 tcx.generics_of(*def_id).has_self
4783 }).unwrap_or(false);
4785 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
4786 let ty = self.impl_self_ty(span, impl_def_id).ty;
4787 let adt_def = ty.ty_adt_def();
4790 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
4791 let variant = adt_def.non_enum_variant();
4792 let ctor_def_id = variant.ctor_def_id.unwrap();
4794 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
4799 let mut err = tcx.sess.struct_span_err(span,
4800 "the `Self` constructor can only be used with tuple or unit structs");
4801 if let Some(adt_def) = adt_def {
4802 match adt_def.adt_kind() {
4804 err.help("did you mean to use one of the enum's variants?");
4808 err.span_suggestion(
4810 "use curly brackets",
4811 String::from("Self { /* fields */ }"),
4812 Applicability::HasPlaceholders,
4819 return (tcx.types.err, res)
4825 let def_id = res.def_id();
4827 // The things we are substituting into the type should not contain
4828 // escaping late-bound regions, and nor should the base type scheme.
4829 let ty = tcx.type_of(def_id);
4831 let substs = self_ctor_substs.unwrap_or_else(|| AstConv::create_substs_for_generic_args(
4837 // Provide the generic args, and whether types should be inferred.
4839 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
4842 // If we've encountered an `impl Trait`-related error, we're just
4843 // going to infer the arguments for better error messages.
4844 if !infer_args_for_err.contains(&index) {
4845 // Check whether the user has provided generic arguments.
4846 if let Some(ref data) = segments[index].args {
4847 return (Some(data), segments[index].infer_args);
4850 return (None, segments[index].infer_args);
4855 // Provide substitutions for parameters for which (valid) arguments have been provided.
4857 match (¶m.kind, arg) {
4858 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
4859 AstConv::ast_region_to_region(self, lt, Some(param)).into()
4861 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
4862 self.to_ty(ty).into()
4864 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
4865 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
4867 _ => unreachable!(),
4870 // Provide substitutions for parameters for which arguments are inferred.
4871 |substs, param, infer_args| {
4873 GenericParamDefKind::Lifetime => {
4874 self.re_infer(Some(param), span).unwrap().into()
4876 GenericParamDefKind::Type { has_default, .. } => {
4877 if !infer_args && has_default {
4878 // If we have a default, then we it doesn't matter that we're not
4879 // inferring the type arguments: we provide the default where any
4881 let default = tcx.type_of(param.def_id);
4884 default.subst_spanned(tcx, substs.unwrap(), Some(span))
4887 // If no type arguments were provided, we have to infer them.
4888 // This case also occurs as a result of some malformed input, e.g.
4889 // a lifetime argument being given instead of a type parameter.
4890 // Using inference instead of `Error` gives better error messages.
4891 self.var_for_def(span, param)
4894 GenericParamDefKind::Const => {
4895 // FIXME(const_generics:defaults)
4896 // No const parameters were provided, we have to infer them.
4897 self.var_for_def(span, param)
4902 assert!(!substs.has_escaping_bound_vars());
4903 assert!(!ty.has_escaping_bound_vars());
4905 // First, store the "user substs" for later.
4906 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
4908 self.add_required_obligations(span, def_id, &substs);
4910 // Substitute the values for the type parameters into the type of
4911 // the referenced item.
4912 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
4914 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
4915 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
4916 // is inherent, there is no `Self` parameter; instead, the impl needs
4917 // type parameters, which we can infer by unifying the provided `Self`
4918 // with the substituted impl type.
4919 // This also occurs for an enum variant on a type alias.
4920 let ty = tcx.type_of(impl_def_id);
4922 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
4923 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
4924 Ok(ok) => self.register_infer_ok_obligations(ok),
4926 self.tcx.sess.delay_span_bug(span, &format!(
4927 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
4935 self.check_rustc_args_require_const(def_id, hir_id, span);
4937 debug!("instantiate_value_path: type of {:?} is {:?}",
4940 self.write_substs(hir_id, substs);
4942 (ty_substituted, res)
4945 /// Add all the obligations that are required, substituting and normalized appropriately.
4946 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
4947 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
4949 for (i, mut obligation) in traits::predicates_for_generics(
4950 traits::ObligationCause::new(
4953 traits::ItemObligation(def_id),
4957 ).into_iter().enumerate() {
4958 // This makes the error point at the bound, but we want to point at the argument
4959 if let Some(span) = spans.get(i) {
4960 obligation.cause.code = traits::BindingObligation(def_id, *span);
4962 self.register_predicate(obligation);
4966 fn check_rustc_args_require_const(&self,
4970 // We're only interested in functions tagged with
4971 // #[rustc_args_required_const], so ignore anything that's not.
4972 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
4976 // If our calling expression is indeed the function itself, we're good!
4977 // If not, generate an error that this can only be called directly.
4978 if let Node::Expr(expr) = self.tcx.hir().get(
4979 self.tcx.hir().get_parent_node(hir_id))
4981 if let ExprKind::Call(ref callee, ..) = expr.kind {
4982 if callee.hir_id == hir_id {
4988 self.tcx.sess.span_err(span, "this function can only be invoked \
4989 directly, not through a function pointer");
4992 // Resolves `typ` by a single level if `typ` is a type variable.
4993 // If no resolution is possible, then an error is reported.
4994 // Numeric inference variables may be left unresolved.
4995 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
4996 let ty = self.resolve_type_vars_with_obligations(ty);
4997 if !ty.is_ty_var() {
5000 if !self.is_tainted_by_errors() {
5001 self.need_type_info_err((**self).body_id, sp, ty)
5002 .note("type must be known at this point")
5005 self.demand_suptype(sp, self.tcx.types.err, ty);
5010 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5013 ctxt: BreakableCtxt<'tcx>,
5015 ) -> (BreakableCtxt<'tcx>, R) {
5018 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5019 index = enclosing_breakables.stack.len();
5020 enclosing_breakables.by_id.insert(id, index);
5021 enclosing_breakables.stack.push(ctxt);
5025 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5026 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5027 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5028 enclosing_breakables.stack.pop().expect("missing breakable context")
5033 /// Instantiate a QueryResponse in a probe context, without a
5034 /// good ObligationCause.
5035 fn probe_instantiate_query_response(
5038 original_values: &OriginalQueryValues<'tcx>,
5039 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5040 ) -> InferResult<'tcx, Ty<'tcx>>
5042 self.instantiate_query_response_and_region_obligations(
5043 &traits::ObligationCause::misc(span, self.body_id),
5049 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5050 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5051 let mut contained_in_place = false;
5053 while let hir::Node::Expr(parent_expr) =
5054 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5056 match &parent_expr.kind {
5057 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5058 if lhs.hir_id == expr_id {
5059 contained_in_place = true;
5065 expr_id = parent_expr.hir_id;
5072 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5073 let own_counts = generics.own_counts();
5075 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5081 if own_counts.types == 0 {
5085 // Make a vector of booleans initially `false`; set to `true` when used.
5086 let mut types_used = vec![false; own_counts.types];
5088 for leaf_ty in ty.walk() {
5089 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.kind {
5090 debug!("found use of ty param num {}", index);
5091 types_used[index as usize - own_counts.lifetimes] = true;
5092 } else if let ty::Error = leaf_ty.kind {
5093 // If there is already another error, do not emit
5094 // an error for not using a type parameter.
5095 assert!(tcx.sess.has_errors());
5100 let types = generics.params.iter().filter(|param| match param.kind {
5101 ty::GenericParamDefKind::Type { .. } => true,
5104 for (&used, param) in types_used.iter().zip(types) {
5106 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5107 let span = tcx.hir().span(id);
5108 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5109 .span_label(span, "unused type parameter")
5115 fn fatally_break_rust(sess: &Session) {
5116 let handler = sess.diagnostic();
5117 handler.span_bug_no_panic(
5119 "It looks like you're trying to break rust; would you like some ICE?",
5121 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5122 handler.note_without_error(
5123 "we would appreciate a joke overview: \
5124 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5126 handler.note_without_error(&format!("rustc {} running on {}",
5127 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5128 crate::session::config::host_triple(),
5132 fn potentially_plural_count(count: usize, word: &str) -> String {
5133 format!("{} {}{}", count, word, pluralise!(count))