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
80 mod generator_interior;
90 use crate::astconv::{AstConv, PathSeg};
91 use crate::middle::lang_items;
92 use crate::namespace::Namespace;
93 use rustc::hir::map::Map;
94 use rustc::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
95 use rustc::infer::error_reporting::TypeAnnotationNeeded::E0282;
96 use rustc::infer::opaque_types::OpaqueTypeDecl;
97 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
98 use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
99 use rustc::infer::{self, InferCtxt, InferOk, InferResult};
100 use rustc::middle::region;
101 use rustc::mir::interpret::ConstValue;
102 use rustc::session::parse::feature_err;
103 use rustc::traits::error_reporting::recursive_type_with_infinite_size_error;
104 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
105 use rustc::ty::adjustment::{
106 Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast,
108 use rustc::ty::fold::{TypeFoldable, TypeFolder};
109 use rustc::ty::layout::VariantIdx;
110 use rustc::ty::query::Providers;
111 use rustc::ty::subst::{GenericArgKind, InternalSubsts, Subst, SubstsRef, UserSelfTy, UserSubsts};
112 use rustc::ty::util::{Discr, IntTypeExt, Representability};
114 self, AdtKind, CanonicalUserType, Const, GenericParamDefKind, RegionKind, ToPolyTraitRef,
115 ToPredicate, Ty, TyCtxt, UserType,
117 use rustc_data_structures::captures::Captures;
118 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
119 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
120 use rustc_hir as hir;
121 use rustc_hir::def::{CtorOf, DefKind, Res};
122 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet, LOCAL_CRATE};
123 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
124 use rustc_hir::itemlikevisit::ItemLikeVisitor;
125 use rustc_hir::{ExprKind, GenericArg, HirIdMap, Item, ItemKind, Node, PatKind, QPath};
126 use rustc_index::vec::Idx;
127 use rustc_span::hygiene::DesugaringKind;
128 use rustc_span::source_map::{original_sp, DUMMY_SP};
129 use rustc_span::symbol::{kw, sym, Ident};
130 use rustc_span::{self, BytePos, MultiSpan, Span};
131 use rustc_target::spec::abi::Abi;
134 use syntax::util::parser::ExprPrecedence;
136 use rustc_error_codes::*;
138 use std::cell::{Cell, Ref, RefCell, RefMut};
140 use std::collections::hash_map::Entry;
142 use std::mem::replace;
143 use std::ops::{self, Deref};
147 use crate::require_c_abi_if_c_variadic;
148 use crate::session::config::EntryFnType;
149 use crate::session::Session;
150 use crate::util::common::{indenter, ErrorReported};
151 use crate::TypeAndSubsts;
153 use self::autoderef::Autoderef;
154 use self::callee::DeferredCallResolution;
155 use self::coercion::{CoerceMany, DynamicCoerceMany};
156 use self::compare_method::{compare_const_impl, compare_impl_method, compare_ty_impl};
157 use self::method::{MethodCallee, SelfSource};
158 pub use self::Expectation::*;
159 use self::TupleArgumentsFlag::*;
162 macro_rules! type_error_struct {
163 ($session:expr, $span:expr, $typ:expr, $code:ident, $($message:tt)*) => ({
164 if $typ.references_error() {
165 $session.diagnostic().struct_dummy()
167 rustc_errors::struct_span_err!($session, $span, $code, $($message)*)
172 /// The type of a local binding, including the revealed type for anon types.
173 #[derive(Copy, Clone, Debug)]
174 pub struct LocalTy<'tcx> {
176 revealed_ty: Ty<'tcx>,
179 /// A wrapper for `InferCtxt`'s `in_progress_tables` field.
180 #[derive(Copy, Clone)]
181 struct MaybeInProgressTables<'a, 'tcx> {
182 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
185 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
186 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
187 match self.maybe_tables {
188 Some(tables) => tables.borrow(),
189 None => bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables"),
193 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
194 match self.maybe_tables {
195 Some(tables) => tables.borrow_mut(),
196 None => bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables"),
201 /// Closures defined within the function. For example:
204 /// bar(move|| { ... })
207 /// Here, the function `foo()` and the closure passed to
208 /// `bar()` will each have their own `FnCtxt`, but they will
209 /// share the inherited fields.
210 pub struct Inherited<'a, 'tcx> {
211 infcx: InferCtxt<'a, 'tcx>,
213 tables: MaybeInProgressTables<'a, 'tcx>,
215 locals: RefCell<HirIdMap<LocalTy<'tcx>>>,
217 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
219 // Some additional `Sized` obligations badly affect type inference.
220 // These obligations are added in a later stage of typeck.
221 deferred_sized_obligations: RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
223 // When we process a call like `c()` where `c` is a closure type,
224 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
225 // `FnOnce` closure. In that case, we defer full resolution of the
226 // call until upvar inference can kick in and make the
227 // decision. We keep these deferred resolutions grouped by the
228 // def-id of the closure, so that once we decide, we can easily go
229 // back and process them.
230 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
232 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
234 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
236 // Opaque types found in explicit return types and their
237 // associated fresh inference variable. Writeback resolves these
238 // variables to get the concrete type, which can be used to
239 // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
240 opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
242 /// A map from inference variables created from opaque
243 /// type instantiations (`ty::Infer`) to the actual opaque
244 /// type (`ty::Opaque`). Used during fallback to map unconstrained
245 /// opaque type inference variables to their corresponding
247 opaque_types_vars: RefCell<FxHashMap<Ty<'tcx>, Ty<'tcx>>>,
249 /// Each type parameter has an implicit region bound that
250 /// indicates it must outlive at least the function body (the user
251 /// may specify stronger requirements). This field indicates the
252 /// region of the callee. If it is `None`, then the parameter
253 /// environment is for an item or something where the "callee" is
255 implicit_region_bound: Option<ty::Region<'tcx>>,
257 body_id: Option<hir::BodyId>,
260 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
261 type Target = InferCtxt<'a, 'tcx>;
262 fn deref(&self) -> &Self::Target {
267 /// When type-checking an expression, we propagate downward
268 /// whatever type hint we are able in the form of an `Expectation`.
269 #[derive(Copy, Clone, Debug)]
270 pub enum Expectation<'tcx> {
271 /// We know nothing about what type this expression should have.
274 /// This expression should have the type given (or some subtype).
275 ExpectHasType(Ty<'tcx>),
277 /// This expression will be cast to the `Ty`.
278 ExpectCastableToType(Ty<'tcx>),
280 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
281 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
282 ExpectRvalueLikeUnsized(Ty<'tcx>),
285 impl<'a, 'tcx> Expectation<'tcx> {
286 // Disregard "castable to" expectations because they
287 // can lead us astray. Consider for example `if cond
288 // {22} else {c} as u8` -- if we propagate the
289 // "castable to u8" constraint to 22, it will pick the
290 // type 22u8, which is overly constrained (c might not
291 // be a u8). In effect, the problem is that the
292 // "castable to" expectation is not the tightest thing
293 // we can say, so we want to drop it in this case.
294 // The tightest thing we can say is "must unify with
295 // else branch". Note that in the case of a "has type"
296 // constraint, this limitation does not hold.
298 // If the expected type is just a type variable, then don't use
299 // an expected type. Otherwise, we might write parts of the type
300 // when checking the 'then' block which are incompatible with the
302 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
304 ExpectHasType(ety) => {
305 let ety = fcx.shallow_resolve(ety);
306 if !ety.is_ty_var() { ExpectHasType(ety) } else { NoExpectation }
308 ExpectRvalueLikeUnsized(ety) => ExpectRvalueLikeUnsized(ety),
313 /// Provides an expectation for an rvalue expression given an *optional*
314 /// hint, which is not required for type safety (the resulting type might
315 /// be checked higher up, as is the case with `&expr` and `box expr`), but
316 /// is useful in determining the concrete type.
318 /// The primary use case is where the expected type is a fat pointer,
319 /// like `&[isize]`. For example, consider the following statement:
321 /// let x: &[isize] = &[1, 2, 3];
323 /// In this case, the expected type for the `&[1, 2, 3]` expression is
324 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
325 /// expectation `ExpectHasType([isize])`, that would be too strong --
326 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
327 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
328 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
329 /// which still is useful, because it informs integer literals and the like.
330 /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
331 /// for examples of where this comes up,.
332 fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
333 match fcx.tcx.struct_tail_without_normalization(ty).kind {
334 ty::Slice(_) | ty::Str | ty::Dynamic(..) => ExpectRvalueLikeUnsized(ty),
335 _ => ExpectHasType(ty),
339 // Resolves `expected` by a single level if it is a variable. If
340 // there is no expected type or resolution is not possible (e.g.,
341 // no constraints yet present), just returns `None`.
342 fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
344 NoExpectation => NoExpectation,
345 ExpectCastableToType(t) => ExpectCastableToType(fcx.resolve_vars_if_possible(&t)),
346 ExpectHasType(t) => ExpectHasType(fcx.resolve_vars_if_possible(&t)),
347 ExpectRvalueLikeUnsized(t) => ExpectRvalueLikeUnsized(fcx.resolve_vars_if_possible(&t)),
351 fn to_option(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
352 match self.resolve(fcx) {
353 NoExpectation => None,
354 ExpectCastableToType(ty) | ExpectHasType(ty) | ExpectRvalueLikeUnsized(ty) => Some(ty),
358 /// It sometimes happens that we want to turn an expectation into
359 /// a **hard constraint** (i.e., something that must be satisfied
360 /// for the program to type-check). `only_has_type` will return
361 /// such a constraint, if it exists.
362 fn only_has_type(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
363 match self.resolve(fcx) {
364 ExpectHasType(ty) => Some(ty),
365 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
369 /// Like `only_has_type`, but instead of returning `None` if no
370 /// hard constraint exists, creates a fresh type variable.
371 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> Ty<'tcx> {
372 self.only_has_type(fcx).unwrap_or_else(|| {
373 fcx.next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span })
378 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
385 fn maybe_mut_place(m: hir::Mutability) -> Self {
387 hir::Mutability::Mut => Needs::MutPlace,
388 hir::Mutability::Not => Needs::None,
393 #[derive(Copy, Clone)]
394 pub struct UnsafetyState {
396 pub unsafety: hir::Unsafety,
397 pub unsafe_push_count: u32,
402 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
403 UnsafetyState { def, unsafety, unsafe_push_count: 0, from_fn: true }
406 pub fn recurse(&mut self, blk: &hir::Block<'_>) -> UnsafetyState {
407 use hir::BlockCheckMode;
408 match self.unsafety {
409 // If this unsafe, then if the outer function was already marked as
410 // unsafe we shouldn't attribute the unsafe'ness to the block. This
411 // way the block can be warned about instead of ignoring this
412 // extraneous block (functions are never warned about).
413 hir::Unsafety::Unsafe if self.from_fn => *self,
416 let (unsafety, def, count) = match blk.rules {
417 BlockCheckMode::PushUnsafeBlock(..) => {
418 (unsafety, blk.hir_id, self.unsafe_push_count.checked_add(1).unwrap())
420 BlockCheckMode::PopUnsafeBlock(..) => {
421 (unsafety, blk.hir_id, self.unsafe_push_count.checked_sub(1).unwrap())
423 BlockCheckMode::UnsafeBlock(..) => {
424 (hir::Unsafety::Unsafe, blk.hir_id, self.unsafe_push_count)
426 BlockCheckMode::DefaultBlock => (unsafety, self.def, self.unsafe_push_count),
428 UnsafetyState { def, unsafety, unsafe_push_count: count, from_fn: false }
434 #[derive(Debug, Copy, Clone)]
440 /// Tracks whether executing a node may exit normally (versus
441 /// return/break/panic, which "diverge", leaving dead code in their
442 /// wake). Tracked semi-automatically (through type variables marked
443 /// as diverging), with some manual adjustments for control-flow
444 /// primitives (approximating a CFG).
445 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
447 /// Potentially unknown, some cases converge,
448 /// others require a CFG to determine them.
451 /// Definitely known to diverge and therefore
452 /// not reach the next sibling or its parent.
454 /// The `Span` points to the expression
455 /// that caused us to diverge
456 /// (e.g. `return`, `break`, etc).
458 /// In some cases (e.g. a `match` expression
459 /// where all arms diverge), we may be
460 /// able to provide a more informative
461 /// message to the user.
462 /// If this is `None`, a default messsage
463 /// will be generated, which is suitable
465 custom_note: Option<&'static str>,
468 /// Same as `Always` but with a reachability
469 /// warning already emitted.
473 // Convenience impls for combining `Diverges`.
475 impl ops::BitAnd for Diverges {
477 fn bitand(self, other: Self) -> Self {
478 cmp::min(self, other)
482 impl ops::BitOr for Diverges {
484 fn bitor(self, other: Self) -> Self {
485 cmp::max(self, other)
489 impl ops::BitAndAssign for Diverges {
490 fn bitand_assign(&mut self, other: Self) {
491 *self = *self & other;
495 impl ops::BitOrAssign for Diverges {
496 fn bitor_assign(&mut self, other: Self) {
497 *self = *self | other;
502 /// Creates a `Diverges::Always` with the provided `span` and the default note message.
503 fn always(span: Span) -> Diverges {
504 Diverges::Always { span, custom_note: None }
507 fn is_always(self) -> bool {
508 // Enum comparison ignores the
509 // contents of fields, so we just
510 // fill them in with garbage here.
511 self >= Diverges::Always { span: DUMMY_SP, custom_note: None }
515 pub struct BreakableCtxt<'tcx> {
518 // this is `null` for loops where break with a value is illegal,
519 // such as `while`, `for`, and `while let`
520 coerce: Option<DynamicCoerceMany<'tcx>>,
523 pub struct EnclosingBreakables<'tcx> {
524 stack: Vec<BreakableCtxt<'tcx>>,
525 by_id: HirIdMap<usize>,
528 impl<'tcx> EnclosingBreakables<'tcx> {
529 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
530 self.opt_find_breakable(target_id).unwrap_or_else(|| {
531 bug!("could not find enclosing breakable with id {}", target_id);
535 fn opt_find_breakable(&mut self, target_id: hir::HirId) -> Option<&mut BreakableCtxt<'tcx>> {
536 match self.by_id.get(&target_id) {
537 Some(ix) => Some(&mut self.stack[*ix]),
543 pub struct FnCtxt<'a, 'tcx> {
546 /// The parameter environment used for proving trait obligations
547 /// in this function. This can change when we descend into
548 /// closures (as they bring new things into scope), hence it is
549 /// not part of `Inherited` (as of the time of this writing,
550 /// closures do not yet change the environment, but they will
552 param_env: ty::ParamEnv<'tcx>,
554 /// Number of errors that had been reported when we started
555 /// checking this function. On exit, if we find that *more* errors
556 /// have been reported, we will skip regionck and other work that
557 /// expects the types within the function to be consistent.
558 // FIXME(matthewjasper) This should not exist, and it's not correct
559 // if type checking is run in parallel.
560 err_count_on_creation: usize,
562 /// If `Some`, this stores coercion information for returned
563 /// expressions. If `None`, this is in a context where return is
564 /// inappropriate, such as a const expression.
566 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
567 /// can track all the return expressions and then use them to
568 /// compute a useful coercion from the set, similar to a match
569 /// expression or other branching context. You can use methods
570 /// like `expected_ty` to access the declared return type (if
572 ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
574 /// First span of a return site that we find. Used in error messages.
575 ret_coercion_span: RefCell<Option<Span>>,
577 yield_ty: Option<Ty<'tcx>>,
579 ps: RefCell<UnsafetyState>,
581 /// Whether the last checked node generates a divergence (e.g.,
582 /// `return` will set this to `Always`). In general, when entering
583 /// an expression or other node in the tree, the initial value
584 /// indicates whether prior parts of the containing expression may
585 /// have diverged. It is then typically set to `Maybe` (and the
586 /// old value remembered) for processing the subparts of the
587 /// current expression. As each subpart is processed, they may set
588 /// the flag to `Always`, etc. Finally, at the end, we take the
589 /// result and "union" it with the original value, so that when we
590 /// return the flag indicates if any subpart of the parent
591 /// expression (up to and including this part) has diverged. So,
592 /// if you read it after evaluating a subexpression `X`, the value
593 /// you get indicates whether any subexpression that was
594 /// evaluating up to and including `X` diverged.
596 /// We currently use this flag only for diagnostic purposes:
598 /// - To warn about unreachable code: if, after processing a
599 /// sub-expression but before we have applied the effects of the
600 /// current node, we see that the flag is set to `Always`, we
601 /// can issue a warning. This corresponds to something like
602 /// `foo(return)`; we warn on the `foo()` expression. (We then
603 /// update the flag to `WarnedAlways` to suppress duplicate
604 /// reports.) Similarly, if we traverse to a fresh statement (or
605 /// tail expression) from a `Always` setting, we will issue a
606 /// warning. This corresponds to something like `{return;
607 /// foo();}` or `{return; 22}`, where we would warn on the
610 /// An expression represents dead code if, after checking it,
611 /// the diverges flag is set to something other than `Maybe`.
612 diverges: Cell<Diverges>,
614 /// Whether any child nodes have any type errors.
615 has_errors: Cell<bool>,
617 enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
619 inh: &'a Inherited<'a, 'tcx>,
622 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
623 type Target = Inherited<'a, 'tcx>;
624 fn deref(&self) -> &Self::Target {
629 /// Helper type of a temporary returned by `Inherited::build(...)`.
630 /// Necessary because we can't write the following bound:
631 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
632 pub struct InheritedBuilder<'tcx> {
633 infcx: infer::InferCtxtBuilder<'tcx>,
637 impl Inherited<'_, 'tcx> {
638 pub fn build(tcx: TyCtxt<'tcx>, def_id: DefId) -> InheritedBuilder<'tcx> {
639 let hir_id_root = if def_id.is_local() {
640 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
641 DefId::local(hir_id.owner)
647 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
653 impl<'tcx> InheritedBuilder<'tcx> {
654 fn enter<F, R>(&mut self, f: F) -> R
656 F: for<'a> FnOnce(Inherited<'a, 'tcx>) -> R,
658 let def_id = self.def_id;
659 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
663 impl Inherited<'a, 'tcx> {
664 fn new(infcx: InferCtxt<'a, 'tcx>, def_id: DefId) -> Self {
666 let item_id = tcx.hir().as_local_hir_id(def_id);
667 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by(id));
668 let implicit_region_bound = body_id.map(|body_id| {
669 let body = tcx.hir().body(body_id);
670 tcx.mk_region(ty::ReScope(region::Scope {
671 id: body.value.hir_id.local_id,
672 data: region::ScopeData::CallSite,
677 tables: MaybeInProgressTables { maybe_tables: infcx.in_progress_tables },
679 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
680 locals: RefCell::new(Default::default()),
681 deferred_sized_obligations: RefCell::new(Vec::new()),
682 deferred_call_resolutions: RefCell::new(Default::default()),
683 deferred_cast_checks: RefCell::new(Vec::new()),
684 deferred_generator_interiors: RefCell::new(Vec::new()),
685 opaque_types: RefCell::new(Default::default()),
686 opaque_types_vars: RefCell::new(Default::default()),
687 implicit_region_bound,
692 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
693 debug!("register_predicate({:?})", obligation);
694 if obligation.has_escaping_bound_vars() {
695 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
697 self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
700 fn register_predicates<I>(&self, obligations: I)
702 I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
704 for obligation in obligations {
705 self.register_predicate(obligation);
709 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
710 self.register_predicates(infer_ok.obligations);
714 fn normalize_associated_types_in<T>(
718 param_env: ty::ParamEnv<'tcx>,
722 T: TypeFoldable<'tcx>,
724 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
725 self.register_infer_ok_obligations(ok)
729 struct CheckItemTypesVisitor<'tcx> {
733 impl ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'tcx> {
734 fn visit_item(&mut self, i: &'tcx hir::Item<'tcx>) {
735 check_item_type(self.tcx, i);
737 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem<'tcx>) {}
738 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem<'tcx>) {}
741 pub fn check_wf_new(tcx: TyCtxt<'_>) {
742 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
743 tcx.hir().krate().par_visit_all_item_likes(&mut visit);
746 fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
747 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
750 fn typeck_item_bodies(tcx: TyCtxt<'_>, crate_num: CrateNum) {
751 debug_assert!(crate_num == LOCAL_CRATE);
752 tcx.par_body_owners(|body_owner_def_id| {
753 tcx.ensure().typeck_tables_of(body_owner_def_id);
757 fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
758 wfcheck::check_item_well_formed(tcx, def_id);
761 fn check_trait_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
762 wfcheck::check_trait_item(tcx, def_id);
765 fn check_impl_item_well_formed(tcx: TyCtxt<'_>, def_id: DefId) {
766 wfcheck::check_impl_item(tcx, def_id);
769 pub fn provide(providers: &mut Providers<'_>) {
770 method::provide(providers);
771 *providers = Providers {
774 diagnostic_only_typeck_tables_of,
778 check_item_well_formed,
779 check_trait_item_well_formed,
780 check_impl_item_well_formed,
781 check_mod_item_types,
786 fn adt_destructor(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::Destructor> {
787 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
790 /// If this `DefId` is a "primary tables entry", returns
791 /// `Some((body_id, header, decl))` with information about
792 /// it's body-id, fn-header and fn-decl (if any). Otherwise,
795 /// If this function returns `Some`, then `typeck_tables(def_id)` will
796 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
797 /// may not succeed. In some cases where this function returns `None`
798 /// (notably closures), `typeck_tables(def_id)` would wind up
799 /// redirecting to the owning function.
803 ) -> Option<(hir::BodyId, Option<&hir::Ty<'_>>, Option<&hir::FnHeader>, Option<&hir::FnDecl<'_>>)> {
804 match tcx.hir().get(id) {
805 Node::Item(item) => match item.kind {
806 hir::ItemKind::Const(ref ty, body) | hir::ItemKind::Static(ref ty, _, body) => {
807 Some((body, Some(ty), None, None))
809 hir::ItemKind::Fn(ref sig, .., body) => {
810 Some((body, None, Some(&sig.header), Some(&sig.decl)))
814 Node::TraitItem(item) => match item.kind {
815 hir::TraitItemKind::Const(ref ty, Some(body)) => Some((body, Some(ty), None, None)),
816 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) => {
817 Some((body, None, Some(&sig.header), Some(&sig.decl)))
821 Node::ImplItem(item) => match item.kind {
822 hir::ImplItemKind::Const(ref ty, body) => Some((body, Some(ty), None, None)),
823 hir::ImplItemKind::Method(ref sig, body) => {
824 Some((body, None, Some(&sig.header), Some(&sig.decl)))
828 Node::AnonConst(constant) => Some((constant.body, None, None, None)),
833 fn has_typeck_tables(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
834 // Closures' tables come from their outermost function,
835 // as they are part of the same "inference environment".
836 let outer_def_id = tcx.closure_base_def_id(def_id);
837 if outer_def_id != def_id {
838 return tcx.has_typeck_tables(outer_def_id);
841 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
842 primary_body_of(tcx, id).is_some()
845 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: DefId) -> &DefIdSet {
846 &*tcx.typeck_tables_of(def_id).used_trait_imports
849 /// Inspects the substs of opaque types, replacing any inference variables
850 /// with proper generic parameter from the identity substs.
852 /// This is run after we normalize the function signature, to fix any inference
853 /// variables introduced by the projection of associated types. This ensures that
854 /// any opaque types used in the signature continue to refer to generic parameters,
855 /// allowing them to be considered for defining uses in the function body
857 /// For example, consider this code.
862 /// fn use_it(self) -> Self::MyItem
864 /// impl<T, I> MyTrait for T where T: Iterator<Item = I> {
865 /// type MyItem = impl Iterator<Item = I>;
866 /// fn use_it(self) -> Self::MyItem {
872 /// When we normalize the signature of `use_it` from the impl block,
873 /// we will normalize `Self::MyItem` to the opaque type `impl Iterator<Item = I>`
874 /// However, this projection result may contain inference variables, due
875 /// to the way that projection works. We didn't have any inference variables
876 /// in the signature to begin with - leaving them in will cause us to incorrectly
877 /// conclude that we don't have a defining use of `MyItem`. By mapping inference
878 /// variables back to the actual generic parameters, we will correctly see that
879 /// we have a defining use of `MyItem`
880 fn fixup_opaque_types<'tcx, T>(tcx: TyCtxt<'tcx>, val: &T) -> T
882 T: TypeFoldable<'tcx>,
884 struct FixupFolder<'tcx> {
888 impl<'tcx> TypeFolder<'tcx> for FixupFolder<'tcx> {
889 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
893 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
895 ty::Opaque(def_id, substs) => {
896 debug!("fixup_opaque_types: found type {:?}", ty);
897 // Here, we replace any inference variables that occur within
898 // the substs of an opaque type. By definition, any type occuring
899 // in the substs has a corresponding generic parameter, which is what
900 // we replace it with.
901 // This replacement is only run on the function signature, so any
902 // inference variables that we come across must be the rust of projection
903 // (there's no other way for a user to get inference variables into
904 // a function signature).
905 if ty.needs_infer() {
906 let new_substs = InternalSubsts::for_item(self.tcx, def_id, |param, _| {
907 let old_param = substs[param.index as usize];
908 match old_param.unpack() {
909 GenericArgKind::Type(old_ty) => {
910 if let ty::Infer(_) = old_ty.kind {
911 // Replace inference type with a generic parameter
912 self.tcx.mk_param_from_def(param)
914 old_param.fold_with(self)
917 GenericArgKind::Const(old_const) => {
918 if let ty::ConstKind::Infer(_) = old_const.val {
919 // This should never happen - we currently do not support
920 // 'const projections', e.g.:
921 // `impl<T: SomeTrait> MyTrait for T where <T as SomeTrait>::MyConst == 25`
922 // which should be the only way for us to end up with a const inference
923 // variable after projection. If Rust ever gains support for this kind
924 // of projection, this should *probably* be changed to
925 // `self.tcx.mk_param_from_def(param)`
927 "Found infer const: `{:?}` in opaque type: {:?}",
932 old_param.fold_with(self)
935 GenericArgKind::Lifetime(old_region) => {
936 if let RegionKind::ReVar(_) = old_region {
937 self.tcx.mk_param_from_def(param)
939 old_param.fold_with(self)
944 let new_ty = self.tcx.mk_opaque(def_id, new_substs);
945 debug!("fixup_opaque_types: new type: {:?}", new_ty);
951 _ => ty.super_fold_with(self),
956 debug!("fixup_opaque_types({:?})", val);
957 val.fold_with(&mut FixupFolder { tcx })
960 fn typeck_tables_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &ty::TypeckTables<'tcx> {
961 let fallback = move || tcx.type_of(def_id);
962 typeck_tables_of_with_fallback(tcx, def_id, fallback)
965 /// Used only to get `TypeckTables` for type inference during error recovery.
966 /// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
967 fn diagnostic_only_typeck_tables_of<'tcx>(
970 ) -> &ty::TypeckTables<'tcx> {
971 assert!(def_id.is_local());
972 let fallback = move || {
973 let span = tcx.hir().span(tcx.hir().as_local_hir_id(def_id).unwrap());
974 tcx.sess.delay_span_bug(span, "diagnostic only typeck table used");
977 typeck_tables_of_with_fallback(tcx, def_id, fallback)
980 fn typeck_tables_of_with_fallback<'tcx>(
983 fallback: impl Fn() -> Ty<'tcx> + 'tcx,
984 ) -> &'tcx ty::TypeckTables<'tcx> {
985 // Closures' tables come from their outermost function,
986 // as they are part of the same "inference environment".
987 let outer_def_id = tcx.closure_base_def_id(def_id);
988 if outer_def_id != def_id {
989 return tcx.typeck_tables_of(outer_def_id);
992 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
993 let span = tcx.hir().span(id);
995 // Figure out what primary body this item has.
996 let (body_id, body_ty, fn_header, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
997 span_bug!(span, "can't type-check body of {:?}", def_id);
999 let body = tcx.hir().body(body_id);
1001 let tables = Inherited::build(tcx, def_id).enter(|inh| {
1002 let param_env = tcx.param_env(def_id);
1003 let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
1004 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
1005 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
1006 AstConv::ty_of_fn(&fcx, header.unsafety, header.abi, decl, &[], None)
1011 check_abi(tcx, span, fn_sig.abi());
1013 // Compute the fty from point of view of inside the fn.
1014 let fn_sig = tcx.liberate_late_bound_regions(def_id, &fn_sig);
1015 let fn_sig = inh.normalize_associated_types_in(
1022 let fn_sig = fixup_opaque_types(tcx, &fn_sig);
1024 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
1027 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
1028 let expected_type = body_ty
1029 .and_then(|ty| match ty.kind {
1030 hir::TyKind::Infer => Some(AstConv::ast_ty_to_ty(&fcx, ty)),
1033 .unwrap_or_else(fallback);
1034 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
1035 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
1037 let revealed_ty = if tcx.features().impl_trait_in_bindings {
1038 fcx.instantiate_opaque_types_from_value(id, &expected_type, body.value.span)
1043 // Gather locals in statics (because of block expressions).
1044 GatherLocalsVisitor { fcx: &fcx, parent_id: id }.visit_body(body);
1046 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
1048 fcx.write_ty(id, revealed_ty);
1053 // All type checking constraints were added, try to fallback unsolved variables.
1054 fcx.select_obligations_where_possible(false, |_| {});
1055 let mut fallback_has_occurred = false;
1057 // We do fallback in two passes, to try to generate
1058 // better error messages.
1059 // The first time, we do *not* replace opaque types.
1060 for ty in &fcx.unsolved_variables() {
1061 fallback_has_occurred |= fcx.fallback_if_possible(ty, FallbackMode::NoOpaque);
1063 // We now see if we can make progress. This might
1064 // cause us to unify inference variables for opaque types,
1065 // since we may have unified some other type variables
1066 // during the first phase of fallback.
1067 // This means that we only replace inference variables with their underlying
1068 // opaque types as a last resort.
1070 // In code like this:
1073 // type MyType = impl Copy;
1074 // fn produce() -> MyType { true }
1075 // fn bad_produce() -> MyType { panic!() }
1078 // we want to unify the opaque inference variable in `bad_produce`
1079 // with the diverging fallback for `panic!` (e.g. `()` or `!`).
1080 // This will produce a nice error message about conflicting concrete
1081 // types for `MyType`.
1083 // If we had tried to fallback the opaque inference variable to `MyType`,
1084 // we will generate a confusing type-check error that does not explicitly
1085 // refer to opaque types.
1086 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
1088 // We now run fallback again, but this time we allow it to replace
1089 // unconstrained opaque type variables, in addition to performing
1090 // other kinds of fallback.
1091 for ty in &fcx.unsolved_variables() {
1092 fallback_has_occurred |= fcx.fallback_if_possible(ty, FallbackMode::All);
1095 // See if we can make any more progress.
1096 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
1098 // Even though coercion casts provide type hints, we check casts after fallback for
1099 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
1102 // Closure and generator analysis may run after fallback
1103 // because they don't constrain other type variables.
1104 fcx.closure_analyze(body);
1105 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
1106 fcx.resolve_generator_interiors(def_id);
1108 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
1109 let ty = fcx.normalize_ty(span, ty);
1110 fcx.require_type_is_sized(ty, span, code);
1113 fcx.select_all_obligations_or_error();
1115 if fn_decl.is_some() {
1116 fcx.regionck_fn(id, body);
1118 fcx.regionck_expr(body);
1121 fcx.resolve_type_vars_in_body(body)
1124 // Consistency check our TypeckTables instance can hold all ItemLocalIds
1125 // it will need to hold.
1126 assert_eq!(tables.local_id_root, Some(DefId::local(id.owner)));
1131 fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
1132 if !tcx.sess.target.target.is_abi_supported(abi) {
1137 "The ABI `{}` is not supported for the current target",
1144 struct GatherLocalsVisitor<'a, 'tcx> {
1145 fcx: &'a FnCtxt<'a, 'tcx>,
1146 parent_id: hir::HirId,
1149 impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
1150 fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
1153 // infer the variable's type
1154 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
1155 kind: TypeVariableOriginKind::TypeInference,
1161 .insert(nid, LocalTy { decl_ty: var_ty, revealed_ty: var_ty });
1165 // take type that the user specified
1166 self.fcx.locals.borrow_mut().insert(nid, typ);
1173 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
1174 type Map = Map<'tcx>;
1176 fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
1177 NestedVisitorMap::None
1180 // Add explicitly-declared locals.
1181 fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) {
1182 let local_ty = match local.ty {
1184 let o_ty = self.fcx.to_ty(&ty);
1186 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
1187 self.fcx.instantiate_opaque_types_from_value(self.parent_id, &o_ty, ty.span)
1196 .canonicalize_user_type_annotation(&UserType::Ty(revealed_ty));
1198 "visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
1199 ty.hir_id, o_ty, revealed_ty, c_ty
1201 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
1203 Some(LocalTy { decl_ty: o_ty, revealed_ty })
1207 self.assign(local.span, local.hir_id, local_ty);
1210 "local variable {:?} is assigned type {}",
1213 .ty_to_string(self.fcx.locals.borrow().get(&local.hir_id).unwrap().clone().decl_ty)
1215 intravisit::walk_local(self, local);
1218 // Add pattern bindings.
1219 fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
1220 if let PatKind::Binding(_, _, ident, _) = p.kind {
1221 let var_ty = self.assign(p.span, p.hir_id, None);
1223 if !self.fcx.tcx.features().unsized_locals {
1224 self.fcx.require_type_is_sized(var_ty, p.span, traits::VariableType(p.hir_id));
1228 "pattern binding {} is assigned to {} with type {:?}",
1231 .ty_to_string(self.fcx.locals.borrow().get(&p.hir_id).unwrap().clone().decl_ty),
1235 intravisit::walk_pat(self, p);
1238 // Don't descend into the bodies of nested closures
1241 _: intravisit::FnKind<'tcx>,
1242 _: &'tcx hir::FnDecl<'tcx>,
1250 /// When `check_fn` is invoked on a generator (i.e., a body that
1251 /// includes yield), it returns back some information about the yield
1253 struct GeneratorTypes<'tcx> {
1254 /// Type of value that is yielded.
1257 /// Types that are captured (see `GeneratorInterior` for more).
1260 /// Indicates if the generator is movable or static (immovable).
1261 movability: hir::Movability,
1264 /// Helper used for fns and closures. Does the grungy work of checking a function
1265 /// body and returns the function context used for that purpose, since in the case of a fn item
1266 /// there is still a bit more to do.
1269 /// * inherited: other fields inherited from the enclosing fn (if any)
1270 fn check_fn<'a, 'tcx>(
1271 inherited: &'a Inherited<'a, 'tcx>,
1272 param_env: ty::ParamEnv<'tcx>,
1273 fn_sig: ty::FnSig<'tcx>,
1274 decl: &'tcx hir::FnDecl<'tcx>,
1276 body: &'tcx hir::Body<'tcx>,
1277 can_be_generator: Option<hir::Movability>,
1278 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
1279 let mut fn_sig = fn_sig.clone();
1281 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1283 // Create the function context. This is either derived from scratch or,
1284 // in the case of closures, based on the outer context.
1285 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1286 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1289 let sess = tcx.sess;
1290 let hir = tcx.hir();
1292 let declared_ret_ty = fn_sig.output();
1293 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1294 let revealed_ret_ty =
1295 fcx.instantiate_opaque_types_from_value(fn_id, &declared_ret_ty, decl.output.span());
1296 debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
1297 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1298 fn_sig = tcx.mk_fn_sig(
1299 fn_sig.inputs().iter().cloned(),
1306 let span = body.value.span;
1308 fn_maybe_err(tcx, span, fn_sig.abi);
1310 if body.generator_kind.is_some() && can_be_generator.is_some() {
1312 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
1313 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1314 fcx.yield_ty = Some(yield_ty);
1317 let outer_def_id = tcx.closure_base_def_id(hir.local_def_id(fn_id));
1318 let outer_hir_id = hir.as_local_hir_id(outer_def_id).unwrap();
1319 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id }.visit_body(body);
1321 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
1322 // (as it's created inside the body itself, not passed in from outside).
1323 let maybe_va_list = if fn_sig.c_variadic {
1324 let va_list_did = tcx.require_lang_item(
1325 lang_items::VaListTypeLangItem,
1326 Some(body.params.last().unwrap().span),
1328 let region = tcx.mk_region(ty::ReScope(region::Scope {
1329 id: body.value.hir_id.local_id,
1330 data: region::ScopeData::CallSite,
1333 Some(tcx.type_of(va_list_did).subst(tcx, &[region.into()]))
1338 // Add formal parameters.
1339 let inputs_hir = hir.fn_decl_by_hir_id(fn_id).map(|decl| &decl.inputs);
1340 let inputs_fn = fn_sig.inputs().iter().copied();
1341 for (idx, (param_ty, param)) in inputs_fn.chain(maybe_va_list).zip(body.params).enumerate() {
1342 // Check the pattern.
1343 fcx.check_pat_top(¶m.pat, param_ty, try { inputs_hir?.get(idx)?.span }, false);
1345 // Check that argument is Sized.
1346 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1347 // for simple cases like `fn foo(x: Trait)`,
1348 // where we would error once on the parameter as a whole, and once on the binding `x`.
1349 if param.pat.simple_ident().is_none() && !tcx.features().unsized_locals {
1350 fcx.require_type_is_sized(param_ty, decl.output.span(), traits::SizedArgumentType);
1353 fcx.write_ty(param.hir_id, param_ty);
1356 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1358 fcx.check_return_expr(&body.value);
1360 // We insert the deferred_generator_interiors entry after visiting the body.
1361 // This ensures that all nested generators appear before the entry of this generator.
1362 // resolve_generator_interiors relies on this property.
1363 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
1365 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span });
1366 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
1367 Some(GeneratorTypes {
1368 yield_ty: fcx.yield_ty.unwrap(),
1370 movability: can_be_generator.unwrap(),
1376 // Finalize the return check by taking the LUB of the return types
1377 // we saw and assigning it to the expected return type. This isn't
1378 // really expected to fail, since the coercions would have failed
1379 // earlier when trying to find a LUB.
1381 // However, the behavior around `!` is sort of complex. In the
1382 // event that the `actual_return_ty` comes back as `!`, that
1383 // indicates that the fn either does not return or "returns" only
1384 // values of type `!`. In this case, if there is an expected
1385 // return type that is *not* `!`, that should be ok. But if the
1386 // return type is being inferred, we want to "fallback" to `!`:
1388 // let x = move || panic!();
1390 // To allow for that, I am creating a type variable with diverging
1391 // fallback. This was deemed ever so slightly better than unifying
1392 // the return value with `!` because it allows for the caller to
1393 // make more assumptions about the return type (e.g., they could do
1395 // let y: Option<u32> = Some(x());
1397 // which would then cause this return type to become `u32`, not
1399 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1400 let mut actual_return_ty = coercion.complete(&fcx);
1401 if actual_return_ty.is_never() {
1402 actual_return_ty = fcx.next_diverging_ty_var(TypeVariableOrigin {
1403 kind: TypeVariableOriginKind::DivergingFn,
1407 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1409 // Check that the main return type implements the termination trait.
1410 if let Some(term_id) = tcx.lang_items().termination() {
1411 if let Some((def_id, EntryFnType::Main)) = tcx.entry_fn(LOCAL_CRATE) {
1412 let main_id = hir.as_local_hir_id(def_id).unwrap();
1413 if main_id == fn_id {
1414 let substs = tcx.mk_substs_trait(declared_ret_ty, &[]);
1415 let trait_ref = ty::TraitRef::new(term_id, substs);
1416 let return_ty_span = decl.output.span();
1417 let cause = traits::ObligationCause::new(
1420 ObligationCauseCode::MainFunctionType,
1423 inherited.register_predicate(traits::Obligation::new(
1426 trait_ref.to_predicate(),
1432 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1433 if let Some(panic_impl_did) = tcx.lang_items().panic_impl() {
1434 if panic_impl_did == hir.local_def_id(fn_id) {
1435 if let Some(panic_info_did) = tcx.lang_items().panic_info() {
1436 if declared_ret_ty.kind != ty::Never {
1437 sess.span_err(decl.output.span(), "return type should be `!`");
1440 let inputs = fn_sig.inputs();
1441 let span = hir.span(fn_id);
1442 if inputs.len() == 1 {
1443 let arg_is_panic_info = match inputs[0].kind {
1444 ty::Ref(region, ty, mutbl) => match ty.kind {
1445 ty::Adt(ref adt, _) => {
1446 adt.did == panic_info_did
1447 && mutbl == hir::Mutability::Not
1448 && *region != RegionKind::ReStatic
1455 if !arg_is_panic_info {
1456 sess.span_err(decl.inputs[0].span, "argument should be `&PanicInfo`");
1459 if let Node::Item(item) = hir.get(fn_id) {
1460 if let ItemKind::Fn(_, ref generics, _) = item.kind {
1461 if !generics.params.is_empty() {
1462 sess.span_err(span, "should have no type parameters");
1467 let span = sess.source_map().def_span(span);
1468 sess.span_err(span, "function should have one argument");
1471 sess.err("language item required, but not found: `panic_info`");
1476 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1477 if let Some(alloc_error_handler_did) = tcx.lang_items().oom() {
1478 if alloc_error_handler_did == hir.local_def_id(fn_id) {
1479 if let Some(alloc_layout_did) = tcx.lang_items().alloc_layout() {
1480 if declared_ret_ty.kind != ty::Never {
1481 sess.span_err(decl.output.span(), "return type should be `!`");
1484 let inputs = fn_sig.inputs();
1485 let span = hir.span(fn_id);
1486 if inputs.len() == 1 {
1487 let arg_is_alloc_layout = match inputs[0].kind {
1488 ty::Adt(ref adt, _) => adt.did == alloc_layout_did,
1492 if !arg_is_alloc_layout {
1493 sess.span_err(decl.inputs[0].span, "argument should be `Layout`");
1496 if let Node::Item(item) = hir.get(fn_id) {
1497 if let ItemKind::Fn(_, ref generics, _) = item.kind {
1498 if !generics.params.is_empty() {
1501 "`#[alloc_error_handler]` function should have no type \
1508 let span = sess.source_map().def_span(span);
1509 sess.span_err(span, "function should have one argument");
1512 sess.err("language item required, but not found: `alloc_layout`");
1520 fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1521 let def_id = tcx.hir().local_def_id(id);
1522 let def = tcx.adt_def(def_id);
1523 def.destructor(tcx); // force the destructor to be evaluated
1524 check_representable(tcx, span, def_id);
1526 if def.repr.simd() {
1527 check_simd(tcx, span, def_id);
1530 check_transparent(tcx, span, def_id);
1531 check_packed(tcx, span, def_id);
1534 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1535 let def_id = tcx.hir().local_def_id(id);
1536 let def = tcx.adt_def(def_id);
1537 def.destructor(tcx); // force the destructor to be evaluated
1538 check_representable(tcx, span, def_id);
1539 check_transparent(tcx, span, def_id);
1540 check_union_fields(tcx, span, def_id);
1541 check_packed(tcx, span, def_id);
1544 /// When the `#![feature(untagged_unions)]` gate is active,
1545 /// check that the fields of the `union` does not contain fields that need dropping.
1546 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: DefId) -> bool {
1547 let item_type = tcx.type_of(item_def_id);
1548 if let ty::Adt(def, substs) = item_type.kind {
1549 assert!(def.is_union());
1550 let fields = &def.non_enum_variant().fields;
1551 for field in fields {
1552 let field_ty = field.ty(tcx, substs);
1553 // We are currently checking the type this field came from, so it must be local.
1554 let field_span = tcx.hir().span_if_local(field.did).unwrap();
1555 let param_env = tcx.param_env(field.did);
1556 if field_ty.needs_drop(tcx, param_env) {
1561 "unions may not contain fields that need dropping"
1563 .span_note(field_span, "`std::mem::ManuallyDrop` can be used to wrap the type")
1569 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind);
1574 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
1575 /// projections that would result in "inheriting lifetimes".
1576 fn check_opaque<'tcx>(
1579 substs: SubstsRef<'tcx>,
1581 origin: &hir::OpaqueTyOrigin,
1583 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
1584 check_opaque_for_cycles(tcx, def_id, substs, span, origin);
1587 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
1588 /// in "inheriting lifetimes".
1589 fn check_opaque_for_inheriting_lifetimes(tcx: TyCtxt<'tcx>, def_id: DefId, span: Span) {
1591 tcx.hir().expect_item(tcx.hir().as_local_hir_id(def_id).expect("opaque type is not local"));
1593 "check_opaque_for_inheriting_lifetimes: def_id={:?} span={:?} item={:?}",
1598 struct ProhibitOpaqueVisitor<'tcx> {
1599 opaque_identity_ty: Ty<'tcx>,
1600 generics: &'tcx ty::Generics,
1603 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
1604 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
1605 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
1606 if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) }
1609 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1610 debug!("check_opaque_for_inheriting_lifetimes: (visit_region) r={:?}", r);
1611 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
1612 return *index < self.generics.parent_count as u32;
1615 r.super_visit_with(self)
1619 let prohibit_opaque = match item.kind {
1620 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn, .. })
1621 | ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn, .. }) => {
1622 let mut visitor = ProhibitOpaqueVisitor {
1623 opaque_identity_ty: tcx
1624 .mk_opaque(def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1625 generics: tcx.generics_of(def_id),
1627 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1629 tcx.predicates_of(def_id)
1632 .any(|(predicate, _)| predicate.visit_with(&mut visitor))
1637 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1638 if prohibit_opaque {
1639 let is_async = match item.kind {
1640 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1641 hir::OpaqueTyOrigin::AsyncFn => true,
1644 _ => unreachable!(),
1647 tcx.sess.span_err(span, &format!(
1648 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1650 if is_async { "async fn" } else { "impl Trait" },
1655 /// Checks that an opaque type does not contain cycles.
1656 fn check_opaque_for_cycles<'tcx>(
1659 substs: SubstsRef<'tcx>,
1661 origin: &hir::OpaqueTyOrigin,
1663 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1664 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1665 struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing",)
1666 .span_label(span, "recursive `async fn`")
1667 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
1671 struct_span_err!(tcx.sess, span, E0720, "opaque type expands to a recursive type",);
1672 err.span_label(span, "expands to a recursive type");
1673 if let ty::Opaque(..) = partially_expanded_type.kind {
1674 err.note("type resolves to itself");
1676 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1683 // Forbid defining intrinsics in Rust code,
1684 // as they must always be defined by the compiler.
1685 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1686 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1687 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1691 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item<'tcx>) {
1693 "check_item_type(it.hir_id={}, it.name={})",
1695 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1697 let _indenter = indenter();
1699 // Consts can play a role in type-checking, so they are included here.
1700 hir::ItemKind::Static(..) => {
1701 let def_id = tcx.hir().local_def_id(it.hir_id);
1702 tcx.typeck_tables_of(def_id);
1703 maybe_check_static_with_link_section(tcx, def_id, it.span);
1705 hir::ItemKind::Const(..) => {
1706 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1708 hir::ItemKind::Enum(ref enum_definition, _) => {
1709 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1711 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1712 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1713 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1714 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1715 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1716 check_impl_items_against_trait(
1723 let trait_def_id = impl_trait_ref.def_id;
1724 check_on_unimplemented(tcx, trait_def_id, it);
1727 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1728 let def_id = tcx.hir().local_def_id(it.hir_id);
1729 check_on_unimplemented(tcx, def_id, it);
1731 for item in items.iter() {
1732 let item = tcx.hir().trait_item(item.id);
1733 if let hir::TraitItemKind::Method(sig, _) = &item.kind {
1734 let abi = sig.header.abi;
1735 fn_maybe_err(tcx, item.ident.span, abi);
1739 hir::ItemKind::Struct(..) => {
1740 check_struct(tcx, it.hir_id, it.span);
1742 hir::ItemKind::Union(..) => {
1743 check_union(tcx, it.hir_id, it.span);
1745 hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
1746 let def_id = tcx.hir().local_def_id(it.hir_id);
1748 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1749 check_opaque(tcx, def_id, substs, it.span, &origin);
1751 hir::ItemKind::TyAlias(..) => {
1752 let def_id = tcx.hir().local_def_id(it.hir_id);
1753 let pty_ty = tcx.type_of(def_id);
1754 let generics = tcx.generics_of(def_id);
1755 check_bounds_are_used(tcx, &generics, pty_ty);
1757 hir::ItemKind::ForeignMod(ref m) => {
1758 check_abi(tcx, it.span, m.abi);
1760 if m.abi == Abi::RustIntrinsic {
1761 for item in m.items {
1762 intrinsic::check_intrinsic_type(tcx, item);
1764 } else if m.abi == Abi::PlatformIntrinsic {
1765 for item in m.items {
1766 intrinsic::check_platform_intrinsic_type(tcx, item);
1769 for item in m.items {
1770 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1771 let own_counts = generics.own_counts();
1772 if generics.params.len() - own_counts.lifetimes != 0 {
1773 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1774 (_, 0) => ("type", "types", Some("u32")),
1775 // We don't specify an example value, because we can't generate
1776 // a valid value for any type.
1777 (0, _) => ("const", "consts", None),
1778 _ => ("type or const", "types or consts", None),
1784 "foreign items may not have {} parameters",
1787 .span_label(item.span, &format!("can't have {} parameters", kinds))
1789 // FIXME: once we start storing spans for type arguments, turn this
1790 // into a suggestion.
1792 "replace the {} parameters with concrete {}{}",
1795 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1801 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.kind {
1802 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1807 _ => { /* nothing to do */ }
1811 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1812 // Only restricted on wasm32 target for now
1813 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1817 // If `#[link_section]` is missing, then nothing to verify
1818 let attrs = tcx.codegen_fn_attrs(id);
1819 if attrs.link_section.is_none() {
1823 // For the wasm32 target statics with `#[link_section]` are placed into custom
1824 // sections of the final output file, but this isn't link custom sections of
1825 // other executable formats. Namely we can only embed a list of bytes,
1826 // nothing with pointers to anything else or relocations. If any relocation
1827 // show up, reject them here.
1828 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1829 // the consumer's responsibility to ensure all bytes that have been read
1830 // have defined values.
1831 if let Ok(static_) = tcx.const_eval_poly(id) {
1832 let alloc = if let ty::ConstKind::Value(ConstValue::ByRef { alloc, .. }) = static_.val {
1835 bug!("Matching on non-ByRef static")
1837 if alloc.relocations().len() != 0 {
1838 let msg = "statics with a custom `#[link_section]` must be a \
1839 simple list of bytes on the wasm target with no \
1840 extra levels of indirection such as references";
1841 tcx.sess.span_err(span, msg);
1846 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item<'_>) {
1847 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1848 // an error would be reported if this fails.
1849 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1852 fn report_forbidden_specialization(
1854 impl_item: &hir::ImplItem<'_>,
1857 let mut err = struct_span_err!(
1861 "`{}` specializes an item from a parent `impl`, but \
1862 that item is not marked `default`",
1865 err.span_label(impl_item.span, format!("cannot specialize default item `{}`", impl_item.ident));
1867 match tcx.span_of_impl(parent_impl) {
1869 err.span_label(span, "parent `impl` is here");
1871 "to specialize, `{}` in the parent `impl` must be marked `default`",
1876 err.note(&format!("parent implementation is in crate `{}`", cname));
1883 fn check_specialization_validity<'tcx>(
1885 trait_def: &ty::TraitDef,
1886 trait_item: &ty::AssocItem,
1888 impl_item: &hir::ImplItem<'_>,
1890 let kind = match impl_item.kind {
1891 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1892 hir::ImplItemKind::Method(..) => ty::AssocKind::Method,
1893 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1894 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1897 let mut ancestor_impls = trait_def
1898 .ancestors(tcx, impl_id)
1900 .filter_map(|parent| {
1901 if parent.is_from_trait() {
1904 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
1909 if ancestor_impls.peek().is_none() {
1910 // No parent, nothing to specialize.
1914 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
1916 // Parent impl exists, and contains the parent item we're trying to specialize, but
1917 // doesn't mark it `default`.
1918 Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
1919 Some(Err(parent_impl.def_id()))
1922 // Parent impl contains item and makes it specializable.
1923 Some(_) => Some(Ok(())),
1925 // Parent impl doesn't mention the item. This means it's inherited from the
1926 // grandparent. In that case, if parent is a `default impl`, inherited items use the
1927 // "defaultness" from the grandparent, else they are final.
1929 if traits::impl_is_default(tcx, parent_impl.def_id()) {
1932 Some(Err(parent_impl.def_id()))
1938 // If `opt_result` is `None`, we have only encoutered `default impl`s that don't contain the
1939 // item. This is allowed, the item isn't actually getting specialized here.
1940 let result = opt_result.unwrap_or(Ok(()));
1942 if let Err(parent_impl) = result {
1943 report_forbidden_specialization(tcx, impl_item, parent_impl);
1947 fn check_impl_items_against_trait<'tcx>(
1949 full_impl_span: Span,
1951 impl_trait_ref: ty::TraitRef<'tcx>,
1952 impl_item_refs: &[hir::ImplItemRef<'_>],
1954 let impl_span = tcx.sess.source_map().def_span(full_impl_span);
1956 // If the trait reference itself is erroneous (so the compilation is going
1957 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1958 // isn't populated for such impls.
1959 if impl_trait_ref.references_error() {
1963 // Locate trait definition and items
1964 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1965 let mut overridden_associated_type = None;
1967 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1969 // Check existing impl methods to see if they are both present in trait
1970 // and compatible with trait signature
1971 for impl_item in impl_items() {
1972 let ty_impl_item = tcx.associated_item(tcx.hir().local_def_id(impl_item.hir_id));
1973 let ty_trait_item = tcx
1974 .associated_items(impl_trait_ref.def_id)
1976 Namespace::from(&impl_item.kind) == Namespace::from(ac.kind)
1977 && tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id)
1980 // Not compatible, but needed for the error message
1981 tcx.associated_items(impl_trait_ref.def_id)
1982 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1985 // Check that impl definition matches trait definition
1986 if let Some(ty_trait_item) = ty_trait_item {
1987 match impl_item.kind {
1988 hir::ImplItemKind::Const(..) => {
1989 // Find associated const definition.
1990 if ty_trait_item.kind == ty::AssocKind::Const {
1999 let mut err = struct_span_err!(
2003 "item `{}` is an associated const, \
2004 which doesn't match its trait `{}`",
2006 impl_trait_ref.print_only_trait_path()
2008 err.span_label(impl_item.span, "does not match trait");
2009 // We can only get the spans from local trait definition
2010 // Same for E0324 and E0325
2011 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
2012 err.span_label(trait_span, "item in trait");
2017 hir::ImplItemKind::Method(..) => {
2018 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
2019 if ty_trait_item.kind == ty::AssocKind::Method {
2020 compare_impl_method(
2029 let mut err = struct_span_err!(
2033 "item `{}` is an associated method, \
2034 which doesn't match its trait `{}`",
2036 impl_trait_ref.print_only_trait_path()
2038 err.span_label(impl_item.span, "does not match trait");
2039 if let Some(trait_span) = opt_trait_span {
2040 err.span_label(trait_span, "item in trait");
2045 hir::ImplItemKind::OpaqueTy(..) | hir::ImplItemKind::TyAlias(_) => {
2046 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
2047 if ty_trait_item.kind == ty::AssocKind::Type {
2048 if ty_trait_item.defaultness.has_value() {
2049 overridden_associated_type = Some(impl_item);
2060 let mut err = struct_span_err!(
2064 "item `{}` is an associated type, \
2065 which doesn't match its trait `{}`",
2067 impl_trait_ref.print_only_trait_path()
2069 err.span_label(impl_item.span, "does not match trait");
2070 if let Some(trait_span) = opt_trait_span {
2071 err.span_label(trait_span, "item in trait");
2078 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
2082 // Check for missing items from trait
2083 let mut missing_items = Vec::new();
2084 let mut invalidated_items = Vec::new();
2085 let associated_type_overridden = overridden_associated_type.is_some();
2086 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
2087 let is_implemented = trait_def
2088 .ancestors(tcx, impl_id)
2089 .leaf_def(tcx, trait_item.ident, trait_item.kind)
2090 .map(|node_item| !node_item.node.is_from_trait())
2093 if !is_implemented && !traits::impl_is_default(tcx, impl_id) {
2094 if !trait_item.defaultness.has_value() {
2095 missing_items.push(trait_item);
2096 } else if associated_type_overridden {
2097 invalidated_items.push(trait_item.ident);
2102 if !missing_items.is_empty() {
2103 missing_items_err(tcx, impl_span, &missing_items, full_impl_span);
2106 if !invalidated_items.is_empty() {
2107 let invalidator = overridden_associated_type.unwrap();
2112 "the following trait items need to be reimplemented as `{}` was overridden: `{}`",
2114 invalidated_items.iter().map(|name| name.to_string()).collect::<Vec<_>>().join("`, `")
2120 fn missing_items_err(
2123 missing_items: &[ty::AssocItem],
2124 full_impl_span: Span,
2126 let missing_items_msg = missing_items
2128 .map(|trait_item| trait_item.ident.to_string())
2129 .collect::<Vec<_>>()
2132 let mut err = struct_span_err!(
2136 "not all trait items implemented, missing: `{}`",
2139 err.span_label(impl_span, format!("missing `{}` in implementation", missing_items_msg));
2141 // `Span` before impl block closing brace.
2142 let hi = full_impl_span.hi() - BytePos(1);
2143 // Point at the place right before the closing brace of the relevant `impl` to suggest
2144 // adding the associated item at the end of its body.
2145 let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi);
2146 // Obtain the level of indentation ending in `sugg_sp`.
2147 let indentation = tcx.sess.source_map().span_to_margin(sugg_sp).unwrap_or(0);
2148 // Make the whitespace that will make the suggestion have the right indentation.
2149 let padding: String = (0..indentation).map(|_| " ").collect();
2151 for trait_item in missing_items {
2152 let snippet = suggestion_signature(&trait_item, tcx);
2153 let code = format!("{}{}\n{}", padding, snippet, padding);
2154 let msg = format!("implement the missing item: `{}`", snippet);
2155 let appl = Applicability::HasPlaceholders;
2156 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
2157 err.span_label(span, format!("`{}` from trait", trait_item.ident));
2158 err.tool_only_span_suggestion(sugg_sp, &msg, code, appl);
2160 err.span_suggestion_hidden(sugg_sp, &msg, code, appl);
2166 /// Return placeholder code for the given function.
2167 fn fn_sig_suggestion(sig: &ty::FnSig<'_>, ident: Ident) -> String {
2172 Some(match ty.kind {
2173 ty::Param(param) if param.name == kw::SelfUpper => "self".to_string(),
2174 ty::Ref(reg, ref_ty, mutability) => {
2175 let reg = match &format!("{}", reg)[..] {
2176 "'_" | "" => String::new(),
2177 reg => format!("{} ", reg),
2180 ty::Param(param) if param.name == kw::SelfUpper => {
2181 format!("&{}{}self", reg, mutability.prefix_str())
2183 _ => format!("_: {:?}", ty),
2186 _ => format!("_: {:?}", ty),
2189 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
2190 .filter_map(|arg| arg)
2191 .collect::<Vec<String>>()
2193 let output = sig.output();
2194 let output = if !output.is_unit() { format!(" -> {:?}", output) } else { String::new() };
2196 let unsafety = sig.unsafety.prefix_str();
2197 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
2198 // not be present in the `fn` definition, not will we account for renamed
2199 // lifetimes between the `impl` and the `trait`, but this should be good enough to
2200 // fill in a significant portion of the missing code, and other subsequent
2201 // suggestions can help the user fix the code.
2202 format!("{}fn {}({}){} {{ unimplemented!() }}", unsafety, ident, args, output)
2205 /// Return placeholder code for the given associated item.
2206 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
2207 /// structured suggestion.
2208 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
2210 ty::AssocKind::Method => {
2211 // We skip the binder here because the binder would deanonymize all
2212 // late-bound regions, and we don't want method signatures to show up
2213 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
2214 // regions just fine, showing `fn(&MyType)`.
2215 fn_sig_suggestion(tcx.fn_sig(assoc.def_id).skip_binder(), assoc.ident)
2217 ty::AssocKind::Type => format!("type {} = Type;", assoc.ident),
2218 // FIXME(type_alias_impl_trait): we should print bounds here too.
2219 ty::AssocKind::OpaqueTy => format!("type {} = Type;", assoc.ident),
2220 ty::AssocKind::Const => {
2221 let ty = tcx.type_of(assoc.def_id);
2222 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
2223 format!("const {}: {:?} = {};", assoc.ident, ty, val)
2228 /// Checks whether a type can be represented in memory. In particular, it
2229 /// identifies types that contain themselves without indirection through a
2230 /// pointer, which would mean their size is unbounded.
2231 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
2232 let rty = tcx.type_of(item_def_id);
2234 // Check that it is possible to represent this type. This call identifies
2235 // (1) types that contain themselves and (2) types that contain a different
2236 // recursive type. It is only necessary to throw an error on those that
2237 // contain themselves. For case 2, there must be an inner type that will be
2238 // caught by case 1.
2239 match rty.is_representable(tcx, sp) {
2240 Representability::SelfRecursive(spans) => {
2241 let mut err = recursive_type_with_infinite_size_error(tcx, item_def_id);
2243 err.span_label(span, "recursive without indirection");
2248 Representability::Representable | Representability::ContainsRecursive => (),
2253 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2254 let t = tcx.type_of(def_id);
2255 if let ty::Adt(def, substs) = t.kind {
2256 if def.is_struct() {
2257 let fields = &def.non_enum_variant().fields;
2258 if fields.is_empty() {
2259 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
2262 let e = fields[0].ty(tcx, substs);
2263 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
2264 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
2265 .span_label(sp, "SIMD elements must have the same type")
2270 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
2271 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
2277 "SIMD vector element type should be machine type"
2287 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2288 let repr = tcx.adt_def(def_id).repr;
2290 for attr in tcx.get_attrs(def_id).iter() {
2291 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
2292 if let attr::ReprPacked(pack) = r {
2293 if let Some(repr_pack) = repr.pack {
2294 if pack as u64 != repr_pack.bytes() {
2299 "type has conflicting packed representation hints"
2307 if repr.align.is_some() {
2312 "type has conflicting packed and align representation hints"
2316 if let Some(def_spans) = check_packed_inner(tcx, def_id, &mut vec![]) {
2317 let mut err = struct_span_err!(
2321 "packed type cannot transitively contain a `#[repr(align)]` type"
2324 let hir = tcx.hir();
2325 if let Some(hir_id) = hir.as_local_hir_id(def_spans[0].0) {
2326 if let Node::Item(Item { ident, .. }) = hir.get(hir_id) {
2328 tcx.def_span(def_spans[0].0),
2329 &format!("`{}` has a `#[repr(align)]` attribute", ident),
2334 if def_spans.len() > 2 {
2335 let mut first = true;
2336 for (adt_def, span) in def_spans.iter().skip(1).rev() {
2337 if let Some(hir_id) = hir.as_local_hir_id(*adt_def) {
2338 if let Node::Item(Item { ident, .. }) = hir.get(hir_id) {
2343 "`{}` contains a field of type `{}`",
2344 tcx.type_of(def_id),
2348 format!("...which contains a field of type `{}`", ident)
2363 fn check_packed_inner(
2366 stack: &mut Vec<DefId>,
2367 ) -> Option<Vec<(DefId, Span)>> {
2368 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind {
2369 if def.is_struct() || def.is_union() {
2370 if def.repr.align.is_some() {
2371 return Some(vec![(def.did, DUMMY_SP)]);
2375 for field in &def.non_enum_variant().fields {
2376 if let ty::Adt(def, _) = field.ty(tcx, substs).kind {
2377 if !stack.contains(&def.did) {
2378 if let Some(mut defs) = check_packed_inner(tcx, def.did, stack) {
2379 defs.push((def.did, field.ident.span));
2392 /// Emit an error when encountering more or less than one variant in a transparent enum.
2393 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2394 let variant_spans: Vec<_> = adt
2397 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
2399 let msg = format!("needs exactly one variant, but has {}", adt.variants.len(),);
2400 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2401 err.span_label(sp, &msg);
2402 if let [start @ .., end] = &*variant_spans {
2403 for variant_span in start {
2404 err.span_label(*variant_span, "");
2406 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2411 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2413 fn bad_non_zero_sized_fields<'tcx>(
2415 adt: &'tcx ty::AdtDef,
2417 field_spans: impl Iterator<Item = Span>,
2420 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2421 let mut err = struct_span_err!(
2425 "{}transparent {} {}",
2426 if adt.is_enum() { "the variant of a " } else { "" },
2430 err.span_label(sp, &msg);
2431 for sp in field_spans {
2432 err.span_label(sp, "this field is non-zero-sized");
2437 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2438 let adt = tcx.adt_def(def_id);
2439 if !adt.repr.transparent() {
2442 let sp = tcx.sess.source_map().def_span(sp);
2444 if adt.is_enum() && !tcx.features().transparent_enums {
2446 &tcx.sess.parse_sess,
2447 sym::transparent_enums,
2449 "transparent enums are unstable",
2454 if adt.is_union() && !tcx.features().transparent_unions {
2456 &tcx.sess.parse_sess,
2457 sym::transparent_unions,
2459 "transparent unions are unstable",
2464 if adt.variants.len() != 1 {
2465 bad_variant_count(tcx, adt, sp, def_id);
2466 if adt.variants.is_empty() {
2467 // Don't bother checking the fields. No variants (and thus no fields) exist.
2472 // For each field, figure out if it's known to be a ZST and align(1)
2473 let field_infos = adt.all_fields().map(|field| {
2474 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2475 let param_env = tcx.param_env(field.did);
2476 let layout = tcx.layout_of(param_env.and(ty));
2477 // We are currently checking the type this field came from, so it must be local
2478 let span = tcx.hir().span_if_local(field.did).unwrap();
2479 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2480 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2484 let non_zst_fields =
2485 field_infos.clone().filter_map(|(span, zst, _align1)| if !zst { Some(span) } else { None });
2486 let non_zst_count = non_zst_fields.clone().count();
2487 if non_zst_count != 1 {
2488 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2490 for (span, zst, align1) in field_infos {
2496 "zero-sized field in transparent {} has alignment larger than 1",
2499 .span_label(span, "has alignment larger than 1")
2505 #[allow(trivial_numeric_casts)]
2506 pub fn check_enum<'tcx>(
2509 vs: &'tcx [hir::Variant<'tcx>],
2512 let def_id = tcx.hir().local_def_id(id);
2513 let def = tcx.adt_def(def_id);
2514 def.destructor(tcx); // force the destructor to be evaluated
2517 let attributes = tcx.get_attrs(def_id);
2518 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2523 "unsupported representation for zero-variant enum"
2525 .span_label(sp, "zero-variant enum")
2530 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2531 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2532 if !tcx.features().repr128 {
2534 &tcx.sess.parse_sess,
2537 "repr with 128-bit type is unstable",
2544 if let Some(ref e) = v.disr_expr {
2545 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2549 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2550 let is_unit = |var: &hir::Variant<'_>| match var.data {
2551 hir::VariantData::Unit(..) => true,
2555 let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();
2556 let has_non_units = vs.iter().any(|var| !is_unit(var));
2557 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2558 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2560 if disr_non_unit || (disr_units && has_non_units) {
2562 struct_span_err!(tcx.sess, sp, E0732, "`#[repr(inttype)]` must be specified");
2567 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2568 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2569 // Check for duplicate discriminant values
2570 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2571 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2572 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2573 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2574 let i_span = match variant_i.disr_expr {
2575 Some(ref expr) => tcx.hir().span(expr.hir_id),
2576 None => tcx.hir().span(variant_i_hir_id),
2578 let span = match v.disr_expr {
2579 Some(ref expr) => tcx.hir().span(expr.hir_id),
2586 "discriminant value `{}` already exists",
2589 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2590 .span_label(span, format!("enum already has `{}`", disr_vals[i]))
2593 disr_vals.push(discr);
2596 check_representable(tcx, sp, def_id);
2597 check_transparent(tcx, sp, def_id);
2600 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span, qpath: &QPath<'_>) {
2605 "expected unit struct, unit variant or constant, found {} `{}`",
2607 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false))
2612 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2613 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2617 fn item_def_id(&self) -> Option<DefId> {
2621 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2623 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2624 let item_id = tcx.hir().ty_param_owner(hir_id);
2625 let item_def_id = tcx.hir().local_def_id(item_id);
2626 let generics = tcx.generics_of(item_def_id);
2627 let index = generics.param_def_id_to_index[&def_id];
2628 ty::GenericPredicates {
2630 predicates: tcx.arena.alloc_from_iter(self.param_env.caller_bounds.iter().filter_map(
2631 |&predicate| match predicate {
2632 ty::Predicate::Trait(ref data)
2633 if data.skip_binder().self_ty().is_param(index) =>
2635 // HACK(eddyb) should get the original `Span`.
2636 let span = tcx.def_span(def_id);
2637 Some((predicate, span))
2645 fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
2647 Some(def) => infer::EarlyBoundRegion(span, def.name),
2648 None => infer::MiscVariable(span),
2650 Some(self.next_region_var(v))
2653 fn allow_ty_infer(&self) -> bool {
2657 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2658 if let Some(param) = param {
2659 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2664 self.next_ty_var(TypeVariableOrigin {
2665 kind: TypeVariableOriginKind::TypeInference,
2674 param: Option<&ty::GenericParamDef>,
2676 ) -> &'tcx Const<'tcx> {
2677 if let Some(param) = param {
2678 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2683 self.next_const_var(
2685 ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
2690 fn projected_ty_from_poly_trait_ref(
2694 item_segment: &hir::PathSegment<'_>,
2695 poly_trait_ref: ty::PolyTraitRef<'tcx>,
2697 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2699 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2703 let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
2712 self.tcx().mk_projection(item_def_id, item_substs)
2715 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2716 if ty.has_escaping_bound_vars() {
2717 ty // FIXME: normalization and escaping regions
2719 self.normalize_associated_types_in(span, &ty)
2723 fn set_tainted_by_errors(&self) {
2724 self.infcx.set_tainted_by_errors()
2727 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2728 self.write_ty(hir_id, ty)
2732 /// Controls whether the arguments are tupled. This is used for the call
2735 /// Tupling means that all call-side arguments are packed into a tuple and
2736 /// passed as a single parameter. For example, if tupling is enabled, this
2739 /// fn f(x: (isize, isize))
2741 /// Can be called as:
2748 #[derive(Clone, Eq, PartialEq)]
2749 enum TupleArgumentsFlag {
2754 /// Controls how we perform fallback for unconstrained
2757 /// Do not fallback type variables to opaque types.
2759 /// Perform all possible kinds of fallback, including
2760 /// turning type variables to opaque types.
2764 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2766 inh: &'a Inherited<'a, 'tcx>,
2767 param_env: ty::ParamEnv<'tcx>,
2768 body_id: hir::HirId,
2769 ) -> FnCtxt<'a, 'tcx> {
2773 err_count_on_creation: inh.tcx.sess.err_count(),
2775 ret_coercion_span: RefCell::new(None),
2777 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
2778 diverges: Cell::new(Diverges::Maybe),
2779 has_errors: Cell::new(false),
2780 enclosing_breakables: RefCell::new(EnclosingBreakables {
2782 by_id: Default::default(),
2788 pub fn sess(&self) -> &Session {
2792 pub fn errors_reported_since_creation(&self) -> bool {
2793 self.tcx.sess.err_count() > self.err_count_on_creation
2796 /// Produces warning on the given node, if the current point in the
2797 /// function is unreachable, and there hasn't been another warning.
2798 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2799 // FIXME: Combine these two 'if' expressions into one once
2800 // let chains are implemented
2801 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2802 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2803 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2804 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2805 if !span.is_desugaring(DesugaringKind::CondTemporary)
2806 && !span.is_desugaring(DesugaringKind::Async)
2807 && !orig_span.is_desugaring(DesugaringKind::Await)
2809 self.diverges.set(Diverges::WarnedAlways);
2811 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2813 let msg = format!("unreachable {}", kind);
2815 .struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, &msg)
2816 .span_label(span, &msg)
2819 custom_note.unwrap_or("any code following this expression is unreachable"),
2826 pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
2827 ObligationCause::new(span, self.body_id, code)
2830 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2831 self.cause(span, ObligationCauseCode::MiscObligation)
2834 /// Resolves type and const variables in `ty` if possible. Unlike the infcx
2835 /// version (resolve_vars_if_possible), this version will
2836 /// also select obligations if it seems useful, in an effort
2837 /// to get more type information.
2838 fn resolve_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2839 debug!("resolve_vars_with_obligations(ty={:?})", ty);
2841 // No Infer()? Nothing needs doing.
2842 if !ty.has_infer_types() && !ty.has_infer_consts() {
2843 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2847 // If `ty` is a type variable, see whether we already know what it is.
2848 ty = self.resolve_vars_if_possible(&ty);
2849 if !ty.has_infer_types() && !ty.has_infer_consts() {
2850 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2854 // If not, try resolving pending obligations as much as
2855 // possible. This can help substantially when there are
2856 // indirect dependencies that don't seem worth tracking
2858 self.select_obligations_where_possible(false, |_| {});
2859 ty = self.resolve_vars_if_possible(&ty);
2861 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2865 fn record_deferred_call_resolution(
2867 closure_def_id: DefId,
2868 r: DeferredCallResolution<'tcx>,
2870 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2871 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2874 fn remove_deferred_call_resolutions(
2876 closure_def_id: DefId,
2877 ) -> Vec<DeferredCallResolution<'tcx>> {
2878 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2879 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2882 pub fn tag(&self) -> String {
2883 format!("{:p}", self)
2886 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2887 self.locals.borrow().get(&nid).cloned().unwrap_or_else(|| {
2888 span_bug!(span, "no type for local variable {}", self.tcx.hir().node_to_string(nid))
2893 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2895 "write_ty({:?}, {:?}) in fcx {}",
2897 self.resolve_vars_if_possible(&ty),
2900 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2902 if ty.references_error() {
2903 self.has_errors.set(true);
2904 self.set_tainted_by_errors();
2908 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
2909 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2912 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
2913 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
2916 pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
2917 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2918 self.write_resolution(hir_id, Ok((DefKind::Method, method.def_id)));
2919 self.write_substs(hir_id, method.substs);
2921 // When the method is confirmed, the `method.substs` includes
2922 // parameters from not just the method, but also the impl of
2923 // the method -- in particular, the `Self` type will be fully
2924 // resolved. However, those are not something that the "user
2925 // specified" -- i.e., those types come from the inferred type
2926 // of the receiver, not something the user wrote. So when we
2927 // create the user-substs, we want to replace those earlier
2928 // types with just the types that the user actually wrote --
2929 // that is, those that appear on the *method itself*.
2931 // As an example, if the user wrote something like
2932 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2933 // type of `foo` (possibly adjusted), but we don't want to
2934 // include that. We want just the `[_, u32]` part.
2935 if !method.substs.is_noop() {
2936 let method_generics = self.tcx.generics_of(method.def_id);
2937 if !method_generics.params.is_empty() {
2938 let user_type_annotation = self.infcx.probe(|_| {
2939 let user_substs = UserSubsts {
2940 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
2941 let i = param.index as usize;
2942 if i < method_generics.parent_count {
2943 self.infcx.var_for_def(DUMMY_SP, param)
2948 user_self_ty: None, // not relevant here
2951 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2957 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2958 self.write_user_type_annotation(hir_id, user_type_annotation);
2963 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
2964 if !substs.is_noop() {
2965 debug!("write_substs({:?}, {:?}) in fcx {}", node_id, substs, self.tag());
2967 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2971 /// Given the substs that we just converted from the HIR, try to
2972 /// canonicalize them and store them as user-given substitutions
2973 /// (i.e., substitutions that must be respected by the NLL check).
2975 /// This should be invoked **before any unifications have
2976 /// occurred**, so that annotations like `Vec<_>` are preserved
2978 pub fn write_user_type_annotation_from_substs(
2982 substs: SubstsRef<'tcx>,
2983 user_self_ty: Option<UserSelfTy<'tcx>>,
2986 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2987 user_self_ty={:?} in fcx {}",
2995 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
2996 let canonicalized = self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
2998 UserSubsts { substs, user_self_ty },
3000 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
3001 self.write_user_type_annotation(hir_id, canonicalized);
3005 pub fn write_user_type_annotation(
3008 canonical_user_type_annotation: CanonicalUserType<'tcx>,
3011 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
3013 canonical_user_type_annotation,
3017 if !canonical_user_type_annotation.is_identity() {
3020 .user_provided_types_mut()
3021 .insert(hir_id, canonical_user_type_annotation);
3023 debug!("write_user_type_annotation: skipping identity substs");
3027 pub fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment<'tcx>>) {
3028 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
3034 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
3035 Entry::Vacant(entry) => {
3038 Entry::Occupied(mut entry) => {
3039 debug!(" - composing on top of {:?}", entry.get());
3040 match (&entry.get()[..], &adj[..]) {
3041 // Applying any adjustment on top of a NeverToAny
3042 // is a valid NeverToAny adjustment, because it can't
3044 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
3046 Adjustment { kind: Adjust::Deref(_), .. },
3047 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
3049 Adjustment { kind: Adjust::Deref(_), .. },
3050 .. // Any following adjustments are allowed.
3052 // A reborrow has no effect before a dereference.
3054 // FIXME: currently we never try to compose autoderefs
3055 // and ReifyFnPointer/UnsafeFnPointer, but we could.
3057 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
3058 expr, entry.get(), adj)
3060 *entry.get_mut() = adj;
3065 /// Basically whenever we are converting from a type scheme into
3066 /// the fn body space, we always want to normalize associated
3067 /// types as well. This function combines the two.
3068 fn instantiate_type_scheme<T>(&self, span: Span, substs: SubstsRef<'tcx>, value: &T) -> T
3070 T: TypeFoldable<'tcx>,
3072 let value = value.subst(self.tcx, substs);
3073 let result = self.normalize_associated_types_in(span, &value);
3074 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}", value, substs, result);
3078 /// As `instantiate_type_scheme`, but for the bounds found in a
3079 /// generic type scheme.
3080 fn instantiate_bounds(
3084 substs: SubstsRef<'tcx>,
3085 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
3086 let bounds = self.tcx.predicates_of(def_id);
3087 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
3088 let result = bounds.instantiate(self.tcx, substs);
3089 let result = self.normalize_associated_types_in(span, &result);
3091 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
3092 bounds, substs, result, spans,
3097 /// Replaces the opaque types from the given value with type variables,
3098 /// and records the `OpaqueTypeMap` for later use during writeback. See
3099 /// `InferCtxt::instantiate_opaque_types` for more details.
3100 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
3102 parent_id: hir::HirId,
3106 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
3108 "instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
3109 parent_def_id, value
3112 let (value, opaque_type_map) =
3113 self.register_infer_ok_obligations(self.instantiate_opaque_types(
3121 let mut opaque_types = self.opaque_types.borrow_mut();
3122 let mut opaque_types_vars = self.opaque_types_vars.borrow_mut();
3123 for (ty, decl) in opaque_type_map {
3124 let _ = opaque_types.insert(ty, decl);
3125 let _ = opaque_types_vars.insert(decl.concrete_ty, decl.opaque_type);
3131 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
3133 T: TypeFoldable<'tcx>,
3135 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
3138 fn normalize_associated_types_in_as_infer_ok<T>(
3142 ) -> InferOk<'tcx, T>
3144 T: TypeFoldable<'tcx>,
3146 self.inh.partially_normalize_associated_types_in(span, self.body_id, self.param_env, value)
3149 pub fn require_type_meets(
3153 code: traits::ObligationCauseCode<'tcx>,
3156 self.register_bound(ty, def_id, traits::ObligationCause::new(span, self.body_id, code));
3159 pub fn require_type_is_sized(
3163 code: traits::ObligationCauseCode<'tcx>,
3165 if !ty.references_error() {
3166 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
3167 self.require_type_meets(ty, span, code, lang_item);
3171 pub fn require_type_is_sized_deferred(
3175 code: traits::ObligationCauseCode<'tcx>,
3177 if !ty.references_error() {
3178 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
3182 pub fn register_bound(
3186 cause: traits::ObligationCause<'tcx>,
3188 if !ty.references_error() {
3189 self.fulfillment_cx.borrow_mut().register_bound(
3199 pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> {
3200 let t = AstConv::ast_ty_to_ty(self, ast_t);
3201 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
3205 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
3206 let ty = self.to_ty(ast_ty);
3207 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
3209 if Self::can_contain_user_lifetime_bounds(ty) {
3210 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
3211 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
3212 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
3218 /// Returns the `DefId` of the constant parameter that the provided expression is a path to.
3219 pub fn const_param_def_id(&self, hir_c: &hir::AnonConst) -> Option<DefId> {
3220 AstConv::const_param_def_id(self, &self.tcx.hir().body(hir_c.body).value)
3223 pub fn to_const(&self, ast_c: &hir::AnonConst, ty: Ty<'tcx>) -> &'tcx ty::Const<'tcx> {
3224 AstConv::ast_const_to_const(self, ast_c, ty)
3227 // If the type given by the user has free regions, save it for later, since
3228 // NLL would like to enforce those. Also pass in types that involve
3229 // projections, since those can resolve to `'static` bounds (modulo #54940,
3230 // which hopefully will be fixed by the time you see this comment, dear
3231 // reader, although I have my doubts). Also pass in types with inference
3232 // types, because they may be repeated. Other sorts of things are already
3233 // sufficiently enforced with erased regions. =)
3234 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
3236 T: TypeFoldable<'tcx>,
3238 t.has_free_regions() || t.has_projections() || t.has_infer_types()
3241 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
3242 match self.tables.borrow().node_types().get(id) {
3244 None if self.is_tainted_by_errors() => self.tcx.types.err,
3247 "no type for node {}: {} in fcx {}",
3249 self.tcx.hir().node_to_string(id),
3256 /// Registers an obligation for checking later, during regionck, that the type `ty` must
3257 /// outlive the region `r`.
3258 pub fn register_wf_obligation(
3262 code: traits::ObligationCauseCode<'tcx>,
3264 // WF obligations never themselves fail, so no real need to give a detailed cause:
3265 let cause = traits::ObligationCause::new(span, self.body_id, code);
3266 self.register_predicate(traits::Obligation::new(
3269 ty::Predicate::WellFormed(ty),
3273 /// Registers obligations that all types appearing in `substs` are well-formed.
3274 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr<'_>) {
3275 for ty in substs.types() {
3276 if !ty.references_error() {
3277 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
3282 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
3283 /// type/region parameter was instantiated (`substs`), creates and registers suitable
3284 /// trait/region obligations.
3286 /// For example, if there is a function:
3289 /// fn foo<'a,T:'a>(...)
3292 /// and a reference:
3298 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
3299 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
3300 pub fn add_obligations_for_parameters(
3302 cause: traits::ObligationCause<'tcx>,
3303 predicates: &ty::InstantiatedPredicates<'tcx>,
3305 assert!(!predicates.has_escaping_bound_vars());
3307 debug!("add_obligations_for_parameters(predicates={:?})", predicates);
3309 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
3310 self.register_predicate(obligation);
3314 // FIXME(arielb1): use this instead of field.ty everywhere
3315 // Only for fields! Returns <none> for methods>
3316 // Indifferent to privacy flags
3320 field: &'tcx ty::FieldDef,
3321 substs: SubstsRef<'tcx>,
3323 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
3326 fn check_casts(&self) {
3327 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3328 for cast in deferred_cast_checks.drain(..) {
3333 fn resolve_generator_interiors(&self, def_id: DefId) {
3334 let mut generators = self.deferred_generator_interiors.borrow_mut();
3335 for (body_id, interior, kind) in generators.drain(..) {
3336 self.select_obligations_where_possible(false, |_| {});
3337 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
3341 // Tries to apply a fallback to `ty` if it is an unsolved variable.
3343 // - Unconstrained ints are replaced with `i32`.
3345 // - Unconstrained floats are replaced with with `f64`.
3347 // - Non-numerics get replaced with `!` when `#![feature(never_type_fallback)]`
3348 // is enabled. Otherwise, they are replaced with `()`.
3350 // Fallback becomes very dubious if we have encountered type-checking errors.
3351 // In that case, fallback to Error.
3352 // The return value indicates whether fallback has occurred.
3353 fn fallback_if_possible(&self, ty: Ty<'tcx>, mode: FallbackMode) -> bool {
3354 use rustc::ty::error::UnconstrainedNumeric::Neither;
3355 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt};
3357 assert!(ty.is_ty_infer());
3358 let fallback = match self.type_is_unconstrained_numeric(ty) {
3359 _ if self.is_tainted_by_errors() => self.tcx().types.err,
3360 UnconstrainedInt => self.tcx.types.i32,
3361 UnconstrainedFloat => self.tcx.types.f64,
3362 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
3364 // This type variable was created from the instantiation of an opaque
3365 // type. The fact that we're attempting to perform fallback for it
3366 // means that the function neither constrained it to a concrete
3367 // type, nor to the opaque type itself.
3369 // For example, in this code:
3372 // type MyType = impl Copy;
3373 // fn defining_use() -> MyType { true }
3374 // fn other_use() -> MyType { defining_use() }
3377 // `defining_use` will constrain the instantiated inference
3378 // variable to `bool`, while `other_use` will constrain
3379 // the instantiated inference variable to `MyType`.
3381 // When we process opaque types during writeback, we
3382 // will handle cases like `other_use`, and not count
3383 // them as defining usages
3385 // However, we also need to handle cases like this:
3388 // pub type Foo = impl Copy;
3389 // fn produce() -> Option<Foo> {
3394 // In the above snippet, the inference varaible created by
3395 // instantiating `Option<Foo>` will be completely unconstrained.
3396 // We treat this as a non-defining use by making the inference
3397 // variable fall back to the opaque type itself.
3398 if let FallbackMode::All = mode {
3399 if let Some(opaque_ty) = self.opaque_types_vars.borrow().get(ty) {
3401 "fallback_if_possible: falling back opaque type var {:?} to {:?}",
3413 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
3414 self.demand_eqtype(rustc_span::DUMMY_SP, ty, fallback);
3418 fn select_all_obligations_or_error(&self) {
3419 debug!("select_all_obligations_or_error");
3420 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
3421 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
3425 /// Select as many obligations as we can at present.
3426 fn select_obligations_where_possible(
3428 fallback_has_occurred: bool,
3429 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
3431 let result = self.fulfillment_cx.borrow_mut().select_where_possible(self);
3432 if let Err(mut errors) = result {
3433 mutate_fullfillment_errors(&mut errors);
3434 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
3438 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
3439 /// returns a type of `&T`, but the actual type we assign to the
3440 /// *expression* is `T`. So this function just peels off the return
3441 /// type by one layer to yield `T`.
3442 fn make_overloaded_place_return_type(
3444 method: MethodCallee<'tcx>,
3445 ) -> ty::TypeAndMut<'tcx> {
3446 // extract method return type, which will be &T;
3447 let ret_ty = method.sig.output();
3449 // method returns &T, but the type as visible to user is T, so deref
3450 ret_ty.builtin_deref(true).unwrap()
3455 expr: &hir::Expr<'_>,
3456 base_expr: &'tcx hir::Expr<'tcx>,
3460 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3461 // FIXME(#18741) -- this is almost but not quite the same as the
3462 // autoderef that normal method probing does. They could likely be
3465 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3466 let mut result = None;
3467 while result.is_none() && autoderef.next().is_some() {
3468 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3470 autoderef.finalize(self);
3474 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3475 /// (and otherwise adjust) `base_expr`, looking for a type which either
3476 /// supports builtin indexing or overloaded indexing.
3477 /// This loop implements one step in that search; the autoderef loop
3478 /// is implemented by `lookup_indexing`.
3481 expr: &hir::Expr<'_>,
3482 base_expr: &hir::Expr<'_>,
3483 autoderef: &Autoderef<'a, 'tcx>,
3486 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3487 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3489 "try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3491 expr, base_expr, adjusted_ty, index_ty
3494 for &unsize in &[false, true] {
3495 let mut self_ty = adjusted_ty;
3497 // We only unsize arrays here.
3498 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3499 self_ty = self.tcx.mk_slice(element_ty);
3505 // If some lookup succeeds, write callee into table and extract index/element
3506 // type from the method signature.
3507 // If some lookup succeeded, install method in table
3508 let input_ty = self.next_ty_var(TypeVariableOrigin {
3509 kind: TypeVariableOriginKind::AutoDeref,
3510 span: base_expr.span,
3512 let method = self.try_overloaded_place_op(
3520 let result = method.map(|ok| {
3521 debug!("try_index_step: success, using overloaded indexing");
3522 let method = self.register_infer_ok_obligations(ok);
3524 let mut adjustments = autoderef.adjust_steps(self, needs);
3525 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3526 let mutbl = match r_mutbl {
3527 hir::Mutability::Not => AutoBorrowMutability::Not,
3528 hir::Mutability::Mut => AutoBorrowMutability::Mut {
3529 // Indexing can be desugared to a method call,
3530 // so maybe we could use two-phase here.
3531 // See the documentation of AllowTwoPhase for why that's
3532 // not the case today.
3533 allow_two_phase_borrow: AllowTwoPhase::No,
3536 adjustments.push(Adjustment {
3537 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3540 .mk_ref(region, ty::TypeAndMut { mutbl: r_mutbl, ty: adjusted_ty }),
3544 adjustments.push(Adjustment {
3545 kind: Adjust::Pointer(PointerCast::Unsize),
3546 target: method.sig.inputs()[0],
3549 self.apply_adjustments(base_expr, adjustments);
3551 self.write_method_call(expr.hir_id, method);
3552 (input_ty, self.make_overloaded_place_return_type(method).ty)
3554 if result.is_some() {
3562 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3563 let (tr, name) = match (op, is_mut) {
3564 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3565 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3566 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3567 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3569 (tr, ast::Ident::with_dummy_span(name))
3572 fn try_overloaded_place_op(
3576 arg_tys: &[Ty<'tcx>],
3579 ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
3580 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})", span, base_ty, needs, op);
3582 // Try Mut first, if needed.
3583 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3584 let method = match (needs, mut_tr) {
3585 (Needs::MutPlace, Some(trait_did)) => {
3586 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3591 // Otherwise, fall back to the immutable version.
3592 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3593 let method = match (method, imm_tr) {
3594 (None, Some(trait_did)) => {
3595 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3597 (method, _) => method,
3603 fn check_method_argument_types(
3606 expr: &'tcx hir::Expr<'tcx>,
3607 method: Result<MethodCallee<'tcx>, ()>,
3608 args_no_rcvr: &'tcx [hir::Expr<'tcx>],
3609 tuple_arguments: TupleArgumentsFlag,
3610 expected: Expectation<'tcx>,
3612 let has_error = match method {
3613 Ok(method) => method.substs.references_error() || method.sig.references_error(),
3617 let err_inputs = self.err_args(args_no_rcvr.len());
3619 let err_inputs = match tuple_arguments {
3620 DontTupleArguments => err_inputs,
3621 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3624 self.check_argument_types(
3634 return self.tcx.types.err;
3637 let method = method.unwrap();
3638 // HACK(eddyb) ignore self in the definition (see above).
3639 let expected_arg_tys = self.expected_inputs_for_expected_output(
3642 method.sig.output(),
3643 &method.sig.inputs()[1..],
3645 self.check_argument_types(
3648 &method.sig.inputs()[1..],
3649 &expected_arg_tys[..],
3651 method.sig.c_variadic,
3653 self.tcx.hir().span_if_local(method.def_id),
3658 fn self_type_matches_expected_vid(
3660 trait_ref: ty::PolyTraitRef<'tcx>,
3661 expected_vid: ty::TyVid,
3663 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3665 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3666 trait_ref, self_ty, expected_vid
3668 match self_ty.kind {
3669 ty::Infer(ty::TyVar(found_vid)) => {
3670 // FIXME: consider using `sub_root_var` here so we
3671 // can see through subtyping.
3672 let found_vid = self.root_var(found_vid);
3673 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3674 expected_vid == found_vid
3680 fn obligations_for_self_ty<'b>(
3683 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3686 // FIXME: consider using `sub_root_var` here so we
3687 // can see through subtyping.
3688 let ty_var_root = self.root_var(self_ty);
3690 "obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3693 self.fulfillment_cx.borrow().pending_obligations()
3698 .pending_obligations()
3700 .filter_map(move |obligation| match obligation.predicate {
3701 ty::Predicate::Projection(ref data) => {
3702 Some((data.to_poly_trait_ref(self.tcx), obligation))
3704 ty::Predicate::Trait(ref data) => Some((data.to_poly_trait_ref(), obligation)),
3705 ty::Predicate::Subtype(..) => None,
3706 ty::Predicate::RegionOutlives(..) => None,
3707 ty::Predicate::TypeOutlives(..) => None,
3708 ty::Predicate::WellFormed(..) => None,
3709 ty::Predicate::ObjectSafe(..) => None,
3710 ty::Predicate::ConstEvaluatable(..) => None,
3711 // N.B., this predicate is created by breaking down a
3712 // `ClosureType: FnFoo()` predicate, where
3713 // `ClosureType` represents some `Closure`. It can't
3714 // possibly be referring to the current closure,
3715 // because we haven't produced the `Closure` for
3716 // this closure yet; this is exactly why the other
3717 // code is looking for a self type of a unresolved
3718 // inference variable.
3719 ty::Predicate::ClosureKind(..) => None,
3721 .filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3724 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3725 self.obligations_for_self_ty(self_ty)
3726 .any(|(tr, _)| Some(tr.def_id()) == self.tcx.lang_items().sized_trait())
3729 /// Generic function that factors out common logic from function calls,
3730 /// method calls and overloaded operators.
3731 fn check_argument_types(
3734 expr: &'tcx hir::Expr<'tcx>,
3735 fn_inputs: &[Ty<'tcx>],
3736 expected_arg_tys: &[Ty<'tcx>],
3737 args: &'tcx [hir::Expr<'tcx>],
3739 tuple_arguments: TupleArgumentsFlag,
3740 def_span: Option<Span>,
3743 // Grab the argument types, supplying fresh type variables
3744 // if the wrong number of arguments were supplied
3745 let supplied_arg_count = if tuple_arguments == DontTupleArguments { args.len() } else { 1 };
3747 // All the input types from the fn signature must outlive the call
3748 // so as to validate implied bounds.
3749 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3750 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3753 let expected_arg_count = fn_inputs.len();
3755 let param_count_error = |expected_count: usize,
3760 let mut err = tcx.sess.struct_span_err_with_code(
3763 "this function takes {}{} but {} {} supplied",
3764 if c_variadic { "at least " } else { "" },
3765 potentially_plural_count(expected_count, "parameter"),
3766 potentially_plural_count(arg_count, "parameter"),
3767 if arg_count == 1 { "was" } else { "were" }
3769 DiagnosticId::Error(error_code.to_owned()),
3772 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
3773 err.span_label(def_s, "defined here");
3776 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3777 // remove closing `)` from the span
3778 let sugg_span = sugg_span.shrink_to_lo();
3779 err.span_suggestion(
3781 "expected the unit value `()`; create it with empty parentheses",
3783 Applicability::MachineApplicable,
3790 if c_variadic { "at least " } else { "" },
3791 potentially_plural_count(expected_count, "parameter")
3798 let mut expected_arg_tys = expected_arg_tys.to_vec();
3800 let formal_tys = if tuple_arguments == TupleArguments {
3801 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3802 match tuple_type.kind {
3803 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3804 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3805 expected_arg_tys = vec![];
3806 self.err_args(args.len())
3808 ty::Tuple(arg_types) => {
3809 expected_arg_tys = match expected_arg_tys.get(0) {
3810 Some(&ty) => match ty.kind {
3811 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3816 arg_types.iter().map(|k| k.expect_ty()).collect()
3823 "cannot use call notation; the first type parameter \
3824 for the function trait is neither a tuple nor unit"
3827 expected_arg_tys = vec![];
3828 self.err_args(args.len())
3831 } else if expected_arg_count == supplied_arg_count {
3833 } else if c_variadic {
3834 if supplied_arg_count >= expected_arg_count {
3837 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3838 expected_arg_tys = vec![];
3839 self.err_args(supplied_arg_count)
3842 // is the missing argument of type `()`?
3843 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
3844 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
3845 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
3846 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
3850 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
3852 expected_arg_tys = vec![];
3853 self.err_args(supplied_arg_count)
3857 "check_argument_types: formal_tys={:?}",
3858 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>()
3861 // If there is no expectation, expect formal_tys.
3862 let expected_arg_tys =
3863 if !expected_arg_tys.is_empty() { expected_arg_tys } else { formal_tys.clone() };
3865 let mut final_arg_types: Vec<(usize, Ty<'_>, Ty<'_>)> = vec![];
3867 // Check the arguments.
3868 // We do this in a pretty awful way: first we type-check any arguments
3869 // that are not closures, then we type-check the closures. This is so
3870 // that we have more information about the types of arguments when we
3871 // type-check the functions. This isn't really the right way to do this.
3872 for &check_closures in &[false, true] {
3873 debug!("check_closures={}", check_closures);
3875 // More awful hacks: before we check argument types, try to do
3876 // an "opportunistic" vtable resolution of any trait bounds on
3877 // the call. This helps coercions.
3879 self.select_obligations_where_possible(false, |errors| {
3880 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
3881 self.point_at_arg_instead_of_call_if_possible(
3883 &final_arg_types[..],
3890 // For C-variadic functions, we don't have a declared type for all of
3891 // the arguments hence we only do our usual type checking with
3892 // the arguments who's types we do know.
3893 let t = if c_variadic {
3895 } else if tuple_arguments == TupleArguments {
3900 for (i, arg) in args.iter().take(t).enumerate() {
3901 // Warn only for the first loop (the "no closures" one).
3902 // Closure arguments themselves can't be diverging, but
3903 // a previous argument can, e.g., `foo(panic!(), || {})`.
3904 if !check_closures {
3905 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
3908 let is_closure = match arg.kind {
3909 ExprKind::Closure(..) => true,
3913 if is_closure != check_closures {
3917 debug!("checking the argument");
3918 let formal_ty = formal_tys[i];
3920 // The special-cased logic below has three functions:
3921 // 1. Provide as good of an expected type as possible.
3922 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3924 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3926 // 2. Coerce to the most detailed type that could be coerced
3927 // to, which is `expected_ty` if `rvalue_hint` returns an
3928 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3929 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3930 // We're processing function arguments so we definitely want to use
3931 // two-phase borrows.
3932 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3933 final_arg_types.push((i, checked_ty, coerce_ty));
3935 // 3. Relate the expected type and the formal one,
3936 // if the expected type was used for the coercion.
3937 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3941 // We also need to make sure we at least write the ty of the other
3942 // arguments which we skipped above.
3944 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3945 use crate::structured_errors::{StructuredDiagnostic, VariadicError};
3946 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3949 for arg in args.iter().skip(expected_arg_count) {
3950 let arg_ty = self.check_expr(&arg);
3952 // There are a few types which get autopromoted when passed via varargs
3953 // in C but we just error out instead and require explicit casts.
3954 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3956 ty::Float(ast::FloatTy::F32) => {
3957 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3959 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3960 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3962 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3963 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3966 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3967 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
3968 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3976 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3977 vec![self.tcx.types.err; len]
3980 /// Given a vec of evaluated `FulfillmentError`s and an `fn` call argument expressions, we walk
3981 /// the checked and coerced types for each argument to see if any of the `FulfillmentError`s
3982 /// reference a type argument. The reason to walk also the checked type is that the coerced type
3983 /// can be not easily comparable with predicate type (because of coercion). If the types match
3984 /// for either checked or coerced type, and there's only *one* argument that does, we point at
3985 /// the corresponding argument's expression span instead of the `fn` call path span.
3986 fn point_at_arg_instead_of_call_if_possible(
3988 errors: &mut Vec<traits::FulfillmentError<'_>>,
3989 final_arg_types: &[(usize, Ty<'tcx>, Ty<'tcx>)],
3991 args: &'tcx [hir::Expr<'tcx>],
3993 // We *do not* do this for desugared call spans to keep good diagnostics when involving
3994 // the `?` operator.
3995 if call_sp.desugaring_kind().is_some() {
3999 for error in errors {
4000 // Only if the cause is somewhere inside the expression we want try to point at arg.
4001 // Otherwise, it means that the cause is somewhere else and we should not change
4002 // anything because we can break the correct span.
4003 if !call_sp.contains(error.obligation.cause.span) {
4007 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
4008 // Collect the argument position for all arguments that could have caused this
4009 // `FulfillmentError`.
4010 let mut referenced_in = final_arg_types
4012 .map(|(i, checked_ty, _)| (i, checked_ty))
4013 .chain(final_arg_types.iter().map(|(i, _, coerced_ty)| (i, coerced_ty)))
4014 .flat_map(|(i, ty)| {
4015 let ty = self.resolve_vars_if_possible(ty);
4016 // We walk the argument type because the argument's type could have
4017 // been `Option<T>`, but the `FulfillmentError` references `T`.
4019 .filter(|&ty| ty == predicate.skip_binder().self_ty())
4022 .collect::<Vec<_>>();
4024 // Both checked and coerced types could have matched, thus we need to remove
4026 referenced_in.dedup();
4028 if let (Some(ref_in), None) = (referenced_in.pop(), referenced_in.pop()) {
4029 // We make sure that only *one* argument matches the obligation failure
4030 // and we assign the obligation's span to its expression's.
4031 error.obligation.cause.span = args[ref_in].span;
4032 error.points_at_arg_span = true;
4038 /// Given a vec of evaluated `FulfillmentError`s and an `fn` call expression, we walk the
4039 /// `PathSegment`s and resolve their type parameters to see if any of the `FulfillmentError`s
4040 /// were caused by them. If they were, we point at the corresponding type argument's span
4041 /// instead of the `fn` call path span.
4042 fn point_at_type_arg_instead_of_call_if_possible(
4044 errors: &mut Vec<traits::FulfillmentError<'_>>,
4045 call_expr: &'tcx hir::Expr<'tcx>,
4047 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
4048 if let hir::ExprKind::Path(qpath) = &path.kind {
4049 if let hir::QPath::Resolved(_, path) = &qpath {
4050 for error in errors {
4051 if let ty::Predicate::Trait(predicate) = error.obligation.predicate {
4052 // If any of the type arguments in this path segment caused the
4053 // `FullfillmentError`, point at its span (#61860).
4057 .filter_map(|seg| seg.args.as_ref())
4058 .flat_map(|a| a.args.iter())
4060 if let hir::GenericArg::Type(hir_ty) = &arg {
4061 if let hir::TyKind::Path(hir::QPath::TypeRelative(..)) =
4064 // Avoid ICE with associated types. As this is best
4065 // effort only, it's ok to ignore the case. It
4066 // would trigger in `is_send::<T::AssocType>();`
4067 // from `typeck-default-trait-impl-assoc-type.rs`.
4069 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
4070 let ty = self.resolve_vars_if_possible(&ty);
4071 if ty == predicate.skip_binder().self_ty() {
4072 error.obligation.cause.span = hir_ty.span;
4084 // AST fragment checking
4085 fn check_lit(&self, lit: &hir::Lit, expected: Expectation<'tcx>) -> Ty<'tcx> {
4089 ast::LitKind::Str(..) => tcx.mk_static_str(),
4090 ast::LitKind::ByteStr(ref v) => {
4091 tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.u8, v.len() as u64))
4093 ast::LitKind::Byte(_) => tcx.types.u8,
4094 ast::LitKind::Char(_) => tcx.types.char,
4095 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
4096 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
4097 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
4098 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind {
4099 ty::Int(_) | ty::Uint(_) => Some(ty),
4100 ty::Char => Some(tcx.types.u8),
4101 ty::RawPtr(..) => Some(tcx.types.usize),
4102 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
4105 opt_ty.unwrap_or_else(|| self.next_int_var())
4107 ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => tcx.mk_mach_float(t),
4108 ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => {
4109 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind {
4110 ty::Float(_) => Some(ty),
4113 opt_ty.unwrap_or_else(|| self.next_float_var())
4115 ast::LitKind::Bool(_) => tcx.types.bool,
4116 ast::LitKind::Err(_) => tcx.types.err,
4120 // Determine the `Self` type, using fresh variables for all variables
4121 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
4122 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
4124 pub fn impl_self_ty(
4126 span: Span, // (potential) receiver for this impl
4128 ) -> TypeAndSubsts<'tcx> {
4129 let ity = self.tcx.type_of(did);
4130 debug!("impl_self_ty: ity={:?}", ity);
4132 let substs = self.fresh_substs_for_item(span, did);
4133 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
4135 TypeAndSubsts { substs: substs, ty: substd_ty }
4138 /// Unifies the output type with the expected type early, for more coercions
4139 /// and forward type information on the input expressions.
4140 fn expected_inputs_for_expected_output(
4143 expected_ret: Expectation<'tcx>,
4144 formal_ret: Ty<'tcx>,
4145 formal_args: &[Ty<'tcx>],
4146 ) -> Vec<Ty<'tcx>> {
4147 let formal_ret = self.resolve_vars_with_obligations(formal_ret);
4148 let ret_ty = match expected_ret.only_has_type(self) {
4150 None => return Vec::new(),
4152 let expect_args = self
4153 .fudge_inference_if_ok(|| {
4154 // Attempt to apply a subtyping relationship between the formal
4155 // return type (likely containing type variables if the function
4156 // is polymorphic) and the expected return type.
4157 // No argument expectations are produced if unification fails.
4158 let origin = self.misc(call_span);
4159 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
4161 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
4162 // to identity so the resulting type is not constrained.
4165 // Process any obligations locally as much as
4166 // we can. We don't care if some things turn
4167 // out unconstrained or ambiguous, as we're
4168 // just trying to get hints here.
4169 self.save_and_restore_in_snapshot_flag(|_| {
4170 let mut fulfill = TraitEngine::new(self.tcx);
4171 for obligation in ok.obligations {
4172 fulfill.register_predicate_obligation(self, obligation);
4174 fulfill.select_where_possible(self)
4178 Err(_) => return Err(()),
4181 // Record all the argument types, with the substitutions
4182 // produced from the above subtyping unification.
4183 Ok(formal_args.iter().map(|ty| self.resolve_vars_if_possible(ty)).collect())
4185 .unwrap_or_default();
4187 "expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
4188 formal_args, formal_ret, expect_args, expected_ret
4193 pub fn check_struct_path(
4197 ) -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
4198 let path_span = match *qpath {
4199 QPath::Resolved(_, ref path) => path.span,
4200 QPath::TypeRelative(ref qself, _) => qself.span,
4202 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
4203 let variant = match def {
4205 self.set_tainted_by_errors();
4208 Res::Def(DefKind::Variant, _) => match ty.kind {
4209 ty::Adt(adt, substs) => Some((adt.variant_of_res(def), adt.did, substs)),
4210 _ => bug!("unexpected type: {:?}", ty),
4212 Res::Def(DefKind::Struct, _)
4213 | Res::Def(DefKind::Union, _)
4214 | Res::Def(DefKind::TyAlias, _)
4215 | Res::Def(DefKind::AssocTy, _)
4216 | Res::SelfTy(..) => match ty.kind {
4217 ty::Adt(adt, substs) if !adt.is_enum() => {
4218 Some((adt.non_enum_variant(), adt.did, substs))
4222 _ => bug!("unexpected definition: {:?}", def),
4225 if let Some((variant, did, substs)) = variant {
4226 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
4227 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
4229 // Check bounds on type arguments used in the path.
4230 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
4232 traits::ObligationCause::new(path_span, self.body_id, traits::ItemObligation(did));
4233 self.add_obligations_for_parameters(cause, &bounds);
4241 "expected struct, variant or union type, found {}",
4242 ty.sort_string(self.tcx)
4244 .span_label(path_span, "not a struct")
4250 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4251 // The newly resolved definition is written into `type_dependent_defs`.
4252 fn finish_resolving_struct_path(
4257 ) -> (Res, Ty<'tcx>) {
4259 QPath::Resolved(ref maybe_qself, ref path) => {
4260 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4261 let ty = AstConv::res_to_ty(self, self_ty, path, true);
4264 QPath::TypeRelative(ref qself, ref segment) => {
4265 let ty = self.to_ty(qself);
4267 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
4273 AstConv::associated_path_to_ty(self, hir_id, path_span, ty, res, segment, true);
4274 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
4275 let result = result.map(|(_, kind, def_id)| (kind, def_id));
4277 // Write back the new resolution.
4278 self.write_resolution(hir_id, result);
4280 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
4285 /// Resolves an associated value path into a base type and associated constant, or method
4286 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
4287 pub fn resolve_ty_and_res_ufcs<'b>(
4289 qpath: &'b QPath<'b>,
4292 ) -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment<'b>]) {
4293 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
4294 let (ty, qself, item_segment) = match *qpath {
4295 QPath::Resolved(ref opt_qself, ref path) => {
4298 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4302 QPath::TypeRelative(ref qself, ref segment) => (self.to_ty(qself), qself, segment),
4304 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
4305 // Return directly on cache hit. This is useful to avoid doubly reporting
4306 // errors with default match binding modes. See #44614.
4308 cached_result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err);
4309 return (def, Some(ty), slice::from_ref(&**item_segment));
4311 let item_name = item_segment.ident;
4312 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
4313 let result = match error {
4314 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
4315 _ => Err(ErrorReported),
4317 if item_name.name != kw::Invalid {
4318 self.report_method_error(
4322 SelfSource::QPath(qself),
4326 .map(|mut e| e.emit());
4331 // Write back the new resolution.
4332 self.write_resolution(hir_id, result);
4334 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
4336 slice::from_ref(&**item_segment),
4340 pub fn check_decl_initializer(
4342 local: &'tcx hir::Local<'tcx>,
4343 init: &'tcx hir::Expr<'tcx>,
4345 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
4346 // for #42640 (default match binding modes).
4349 let ref_bindings = local.pat.contains_explicit_ref_binding();
4351 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
4352 if let Some(m) = ref_bindings {
4353 // Somewhat subtle: if we have a `ref` binding in the pattern,
4354 // we want to avoid introducing coercions for the RHS. This is
4355 // both because it helps preserve sanity and, in the case of
4356 // ref mut, for soundness (issue #23116). In particular, in
4357 // the latter case, we need to be clear that the type of the
4358 // referent for the reference that results is *equal to* the
4359 // type of the place it is referencing, and not some
4360 // supertype thereof.
4361 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4362 self.demand_eqtype(init.span, local_ty, init_ty);
4365 self.check_expr_coercable_to_type(init, local_ty)
4369 /// Type check a `let` statement.
4370 pub fn check_decl_local(&self, local: &'tcx hir::Local<'tcx>) {
4371 // Determine and write the type which we'll check the pattern against.
4372 let ty = self.local_ty(local.span, local.hir_id).decl_ty;
4373 self.write_ty(local.hir_id, ty);
4375 // Type check the initializer.
4376 if let Some(ref init) = local.init {
4377 let init_ty = self.check_decl_initializer(local, &init);
4378 self.overwrite_local_ty_if_err(local, ty, init_ty);
4381 // Does the expected pattern type originate from an expression and what is the span?
4382 let (origin_expr, ty_span) = match (local.ty, local.init) {
4383 (Some(ty), _) => (false, Some(ty.span)), // Bias towards the explicit user type.
4384 (_, Some(init)) => (true, Some(init.span)), // No explicit type; so use the scrutinee.
4385 _ => (false, None), // We have `let $pat;`, so the expected type is unconstrained.
4388 // Type check the pattern. Override if necessary to avoid knock-on errors.
4389 self.check_pat_top(&local.pat, ty, ty_span, origin_expr);
4390 let pat_ty = self.node_ty(local.pat.hir_id);
4391 self.overwrite_local_ty_if_err(local, ty, pat_ty);
4394 fn overwrite_local_ty_if_err(
4396 local: &'tcx hir::Local<'tcx>,
4400 if ty.references_error() {
4401 // Override the types everywhere with `types.err` to avoid knock on errors.
4402 self.write_ty(local.hir_id, ty);
4403 self.write_ty(local.pat.hir_id, ty);
4404 let local_ty = LocalTy { decl_ty, revealed_ty: ty };
4405 self.locals.borrow_mut().insert(local.hir_id, local_ty);
4406 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
4410 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
4411 err.span_suggestion_short(
4412 span.shrink_to_hi(),
4413 "consider using a semicolon here",
4415 Applicability::MachineApplicable,
4419 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>) {
4420 // Don't do all the complex logic below for `DeclItem`.
4422 hir::StmtKind::Item(..) => return,
4423 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
4426 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
4428 // Hide the outer diverging and `has_errors` flags.
4429 let old_diverges = self.diverges.get();
4430 let old_has_errors = self.has_errors.get();
4431 self.diverges.set(Diverges::Maybe);
4432 self.has_errors.set(false);
4435 hir::StmtKind::Local(ref l) => {
4436 self.check_decl_local(&l);
4439 hir::StmtKind::Item(_) => {}
4440 hir::StmtKind::Expr(ref expr) => {
4441 // Check with expected type of `()`.
4443 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
4444 self.suggest_semicolon_at_end(expr.span, err);
4447 hir::StmtKind::Semi(ref expr) => {
4448 self.check_expr(&expr);
4452 // Combine the diverging and `has_error` flags.
4453 self.diverges.set(self.diverges.get() | old_diverges);
4454 self.has_errors.set(self.has_errors.get() | old_has_errors);
4457 pub fn check_block_no_value(&self, blk: &'tcx hir::Block<'tcx>) {
4458 let unit = self.tcx.mk_unit();
4459 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4461 // if the block produces a `!` value, that can always be
4462 // (effectively) coerced to unit.
4464 self.demand_suptype(blk.span, unit, ty);
4468 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
4469 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
4470 /// when given code like the following:
4472 /// if false { return 0i32; } else { 1u32 }
4473 /// // ^^^^ point at this instead of the whole `if` expression
4475 fn get_expr_coercion_span(&self, expr: &hir::Expr<'_>) -> rustc_span::Span {
4476 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
4477 let arm_spans: Vec<Span> = arms
4480 self.in_progress_tables
4481 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
4482 .and_then(|arm_ty| {
4483 if arm_ty.is_never() {
4486 Some(match &arm.body.kind {
4487 // Point at the tail expression when possible.
4488 hir::ExprKind::Block(block, _) => {
4489 block.expr.as_ref().map(|e| e.span).unwrap_or(block.span)
4497 if arm_spans.len() == 1 {
4498 return arm_spans[0];
4504 fn check_block_with_expected(
4506 blk: &'tcx hir::Block<'tcx>,
4507 expected: Expectation<'tcx>,
4510 let mut fcx_ps = self.ps.borrow_mut();
4511 let unsafety_state = fcx_ps.recurse(blk);
4512 replace(&mut *fcx_ps, unsafety_state)
4515 // In some cases, blocks have just one exit, but other blocks
4516 // can be targeted by multiple breaks. This can happen both
4517 // with labeled blocks as well as when we desugar
4518 // a `try { ... }` expression.
4522 // 'a: { if true { break 'a Err(()); } Ok(()) }
4524 // Here we would wind up with two coercions, one from
4525 // `Err(())` and the other from the tail expression
4526 // `Ok(())`. If the tail expression is omitted, that's a
4527 // "forced unit" -- unless the block diverges, in which
4528 // case we can ignore the tail expression (e.g., `'a: {
4529 // break 'a 22; }` would not force the type of the block
4531 let tail_expr = blk.expr.as_ref();
4532 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4533 let coerce = if blk.targeted_by_break {
4534 CoerceMany::new(coerce_to_ty)
4536 let tail_expr: &[&hir::Expr<'_>] = match tail_expr {
4537 Some(e) => slice::from_ref(e),
4540 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4543 let prev_diverges = self.diverges.get();
4544 let ctxt = BreakableCtxt { coerce: Some(coerce), may_break: false };
4546 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4547 for s in blk.stmts {
4551 // check the tail expression **without** holding the
4552 // `enclosing_breakables` lock below.
4553 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4555 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4556 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4557 let coerce = ctxt.coerce.as_mut().unwrap();
4558 if let Some(tail_expr_ty) = tail_expr_ty {
4559 let tail_expr = tail_expr.unwrap();
4560 let span = self.get_expr_coercion_span(tail_expr);
4561 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4562 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4564 // Subtle: if there is no explicit tail expression,
4565 // that is typically equivalent to a tail expression
4566 // of `()` -- except if the block diverges. In that
4567 // case, there is no value supplied from the tail
4568 // expression (assuming there are no other breaks,
4569 // this implies that the type of the block will be
4572 // #41425 -- label the implicit `()` as being the
4573 // "found type" here, rather than the "expected type".
4574 if !self.diverges.get().is_always() {
4575 // #50009 -- Do not point at the entire fn block span, point at the return type
4576 // span, as it is the cause of the requirement, and
4577 // `consider_hint_about_removing_semicolon` will point at the last expression
4578 // if it were a relevant part of the error. This improves usability in editors
4579 // that highlight errors inline.
4580 let mut sp = blk.span;
4581 let mut fn_span = None;
4582 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4583 let ret_sp = decl.output.span();
4584 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4585 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4586 // output would otherwise be incorrect and even misleading. Make sure
4587 // the span we're aiming at correspond to a `fn` body.
4588 if block_sp == blk.span {
4590 fn_span = Some(ident.span);
4594 coerce.coerce_forced_unit(
4598 if let Some(expected_ty) = expected.only_has_type(self) {
4599 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4601 if let Some(fn_span) = fn_span {
4604 "implicitly returns `()` as its body has no tail or `return` \
4616 // If we can break from the block, then the block's exit is always reachable
4617 // (... as long as the entry is reachable) - regardless of the tail of the block.
4618 self.diverges.set(prev_diverges);
4621 let mut ty = ctxt.coerce.unwrap().complete(self);
4623 if self.has_errors.get() || ty.references_error() {
4624 ty = self.tcx.types.err
4627 self.write_ty(blk.hir_id, ty);
4629 *self.ps.borrow_mut() = prev;
4633 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4634 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4636 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })
4637 | Node::ImplItem(&hir::ImplItem {
4638 kind: hir::ImplItemKind::Method(_, body_id), ..
4640 let body = self.tcx.hir().body(body_id);
4641 if let ExprKind::Block(block, _) = &body.value.kind {
4642 return Some(block.span);
4650 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4651 fn get_parent_fn_decl(
4654 ) -> Option<(&'tcx hir::FnDecl<'tcx>, ast::Ident)> {
4655 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4656 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4659 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4660 fn get_node_fn_decl(
4663 ) -> Option<(&'tcx hir::FnDecl<'tcx>, ast::Ident, bool)> {
4665 Node::Item(&hir::Item { ident, kind: hir::ItemKind::Fn(ref sig, ..), .. }) => {
4666 // This is less than ideal, it will not suggest a return type span on any
4667 // method called `main`, regardless of whether it is actually the entry point,
4668 // but it will still present it as the reason for the expected type.
4669 Some((&sig.decl, ident, ident.name != sym::main))
4671 Node::TraitItem(&hir::TraitItem {
4673 kind: hir::TraitItemKind::Method(ref sig, ..),
4675 }) => Some((&sig.decl, ident, true)),
4676 Node::ImplItem(&hir::ImplItem {
4678 kind: hir::ImplItemKind::Method(ref sig, ..),
4680 }) => Some((&sig.decl, ident, false)),
4685 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4686 /// suggestion can be made, `None` otherwise.
4687 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, bool)> {
4688 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4689 // `while` before reaching it, as block tail returns are not available in them.
4690 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4691 let parent = self.tcx.hir().get(blk_id);
4692 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4696 /// On implicit return expressions with mismatched types, provides the following suggestions:
4698 /// - Points out the method's return type as the reason for the expected type.
4699 /// - Possible missing semicolon.
4700 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4701 pub fn suggest_mismatched_types_on_tail(
4703 err: &mut DiagnosticBuilder<'_>,
4704 expr: &'tcx hir::Expr<'tcx>,
4710 let expr = expr.peel_drop_temps();
4711 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4712 let mut pointing_at_return_type = false;
4713 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4714 pointing_at_return_type =
4715 self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest);
4717 pointing_at_return_type
4720 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4721 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4723 /// fn foo(x: usize) -> usize { x }
4724 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4728 err: &mut DiagnosticBuilder<'_>,
4729 expr: &hir::Expr<'_>,
4733 let hir = self.tcx.hir();
4734 let (def_id, sig) = match found.kind {
4735 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4736 ty::Closure(def_id, substs) => {
4737 // We don't use `closure_sig` to account for malformed closures like
4738 // `|_: [_; continue]| {}` and instead we don't suggest anything.
4739 let closure_sig_ty = substs.as_closure().sig_ty(def_id, self.tcx);
4742 match closure_sig_ty.kind {
4743 ty::FnPtr(sig) => sig,
4751 let sig = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig).0;
4752 let sig = self.normalize_associated_types_in(expr.span, &sig);
4753 if self.can_coerce(sig.output(), expected) {
4754 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4755 (String::new(), Applicability::MachineApplicable)
4757 ("...".to_string(), Applicability::HasPlaceholders)
4759 let mut msg = "call this function";
4760 match hir.get_if_local(def_id) {
4761 Some(Node::Item(hir::Item { kind: ItemKind::Fn(.., body_id), .. }))
4762 | Some(Node::ImplItem(hir::ImplItem {
4763 kind: hir::ImplItemKind::Method(_, body_id),
4766 | Some(Node::TraitItem(hir::TraitItem {
4767 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Provided(body_id)),
4770 let body = hir.body(*body_id);
4774 .map(|param| match ¶m.pat.kind {
4775 hir::PatKind::Binding(_, _, ident, None)
4776 if ident.name != kw::SelfLower =>
4780 _ => "_".to_string(),
4782 .collect::<Vec<_>>()
4785 Some(Node::Expr(hir::Expr {
4786 kind: ExprKind::Closure(_, _, body_id, _, _),
4787 span: full_closure_span,
4790 if *full_closure_span == expr.span {
4793 msg = "call this closure";
4794 let body = hir.body(*body_id);
4798 .map(|param| match ¶m.pat.kind {
4799 hir::PatKind::Binding(_, _, ident, None)
4800 if ident.name != kw::SelfLower =>
4804 _ => "_".to_string(),
4806 .collect::<Vec<_>>()
4809 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4810 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4811 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4812 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4813 msg = "instantiate this tuple variant";
4815 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4816 msg = "instantiate this tuple struct";
4821 Some(Node::ForeignItem(hir::ForeignItem {
4822 kind: hir::ForeignItemKind::Fn(_, idents, _),
4828 if ident.name != kw::SelfLower {
4834 .collect::<Vec<_>>()
4837 Some(Node::TraitItem(hir::TraitItem {
4838 kind: hir::TraitItemKind::Method(.., hir::TraitMethod::Required(idents)),
4844 if ident.name != kw::SelfLower {
4850 .collect::<Vec<_>>()
4855 if let Ok(code) = self.sess().source_map().span_to_snippet(expr.span) {
4856 err.span_suggestion(
4858 &format!("use parentheses to {}", msg),
4859 format!("{}({})", code, sugg_call),
4868 pub fn suggest_ref_or_into(
4870 err: &mut DiagnosticBuilder<'_>,
4871 expr: &hir::Expr<'_>,
4875 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
4876 err.span_suggestion(sp, msg, suggestion, Applicability::MachineApplicable);
4877 } else if let (ty::FnDef(def_id, ..), true) =
4878 (&found.kind, self.suggest_fn_call(err, expr, expected, found))
4880 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
4881 let sp = self.sess().source_map().def_span(sp);
4882 err.span_label(sp, &format!("{} defined here", found));
4884 } else if !self.check_for_cast(err, expr, found, expected) {
4885 let is_struct_pat_shorthand_field =
4886 self.is_hir_id_from_struct_pattern_shorthand_field(expr.hir_id, expr.span);
4887 let methods = self.get_conversion_methods(expr.span, expected, found);
4888 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
4889 let mut suggestions = iter::repeat(&expr_text)
4890 .zip(methods.iter())
4891 .filter_map(|(receiver, method)| {
4892 let method_call = format!(".{}()", method.ident);
4893 if receiver.ends_with(&method_call) {
4894 None // do not suggest code that is already there (#53348)
4896 let method_call_list = [".to_vec()", ".to_string()"];
4897 let sugg = if receiver.ends_with(".clone()")
4898 && method_call_list.contains(&method_call.as_str())
4900 let max_len = receiver.rfind(".").unwrap();
4901 format!("{}{}", &receiver[..max_len], method_call)
4903 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
4904 format!("({}){}", receiver, method_call)
4906 format!("{}{}", receiver, method_call)
4909 Some(if is_struct_pat_shorthand_field {
4910 format!("{}: {}", receiver, sugg)
4917 if suggestions.peek().is_some() {
4918 err.span_suggestions(
4920 "try using a conversion method",
4922 Applicability::MaybeIncorrect,
4929 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
4930 /// in the heap by calling `Box::new()`.
4931 fn suggest_boxing_when_appropriate(
4933 err: &mut DiagnosticBuilder<'_>,
4934 expr: &hir::Expr<'_>,
4938 if self.tcx.hir().is_const_context(expr.hir_id) {
4939 // Do not suggest `Box::new` in const context.
4942 if !expected.is_box() || found.is_box() {
4945 let boxed_found = self.tcx.mk_box(found);
4946 if let (true, Ok(snippet)) = (
4947 self.can_coerce(boxed_found, expected),
4948 self.sess().source_map().span_to_snippet(expr.span),
4950 err.span_suggestion(
4952 "store this in the heap by calling `Box::new`",
4953 format!("Box::new({})", snippet),
4954 Applicability::MachineApplicable,
4957 "for more on the distinction between the stack and the \
4958 heap, read https://doc.rust-lang.org/book/ch15-01-box.html, \
4959 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
4960 https://doc.rust-lang.org/std/boxed/index.html",
4965 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
4969 /// bar_that_returns_u32()
4973 /// This routine checks if the return expression in a block would make sense on its own as a
4974 /// statement and the return type has been left as default or has been specified as `()`. If so,
4975 /// it suggests adding a semicolon.
4976 fn suggest_missing_semicolon(
4978 err: &mut DiagnosticBuilder<'_>,
4979 expression: &'tcx hir::Expr<'tcx>,
4983 if expected.is_unit() {
4984 // `BlockTailExpression` only relevant if the tail expr would be
4985 // useful on its own.
4986 match expression.kind {
4988 | ExprKind::MethodCall(..)
4989 | ExprKind::Loop(..)
4990 | ExprKind::Match(..)
4991 | ExprKind::Block(..) => {
4992 err.span_suggestion(
4993 cause_span.shrink_to_hi(),
4994 "try adding a semicolon",
4996 Applicability::MachineApplicable,
5004 /// A possible error is to forget to add a return type that is needed:
5008 /// bar_that_returns_u32()
5012 /// This routine checks if the return type is left as default, the method is not part of an
5013 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
5015 fn suggest_missing_return_type(
5017 err: &mut DiagnosticBuilder<'_>,
5018 fn_decl: &hir::FnDecl<'_>,
5023 // Only suggest changing the return type for methods that
5024 // haven't set a return type at all (and aren't `fn main()` or an impl).
5025 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
5026 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
5027 err.span_suggestion(
5029 "try adding a return type",
5030 format!("-> {} ", self.resolve_vars_with_obligations(found)),
5031 Applicability::MachineApplicable,
5035 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
5036 err.span_label(span, "possibly return type missing here?");
5039 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
5040 // `fn main()` must return `()`, do not suggest changing return type
5041 err.span_label(span, "expected `()` because of default return type");
5044 // expectation was caused by something else, not the default return
5045 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => false,
5046 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
5047 // Only point to return type if the expected type is the return type, as if they
5048 // are not, the expectation must have been caused by something else.
5049 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
5051 let ty = AstConv::ast_ty_to_ty(self, ty);
5052 debug!("suggest_missing_return_type: return type {:?}", ty);
5053 debug!("suggest_missing_return_type: expected type {:?}", ty);
5054 if ty.kind == expected.kind {
5055 err.span_label(sp, format!("expected `{}` because of return type", expected));
5063 /// A possible error is to forget to add `.await` when using futures:
5066 /// async fn make_u32() -> u32 {
5070 /// fn take_u32(x: u32) {}
5072 /// async fn foo() {
5073 /// let x = make_u32();
5078 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
5079 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
5080 /// `.await` to the tail of the expression.
5081 fn suggest_missing_await(
5083 err: &mut DiagnosticBuilder<'_>,
5084 expr: &hir::Expr<'_>,
5088 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
5089 // body isn't `async`.
5090 let item_id = self.tcx().hir().get_parent_node(self.body_id);
5091 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
5092 let body = self.tcx().hir().body(body_id);
5093 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
5095 // Check for `Future` implementations by constructing a predicate to
5096 // prove: `<T as Future>::Output == U`
5097 let future_trait = self.tcx.lang_items().future_trait().unwrap();
5098 let item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
5100 ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
5101 // `<T as Future>::Output`
5102 projection_ty: ty::ProjectionTy {
5104 substs: self.tcx.mk_substs_trait(
5106 self.fresh_substs_for_item(sp, item_def_id),
5113 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
5114 debug!("suggest_missing_await: trying obligation {:?}", obligation);
5115 if self.infcx.predicate_may_hold(&obligation) {
5116 debug!("suggest_missing_await: obligation held: {:?}", obligation);
5117 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
5118 err.span_suggestion(
5120 "consider using `.await` here",
5121 format!("{}.await", code),
5122 Applicability::MaybeIncorrect,
5125 debug!("suggest_missing_await: no snippet for {:?}", sp);
5128 debug!("suggest_missing_await: obligation did not hold: {:?}", obligation)
5134 /// A common error is to add an extra semicolon:
5137 /// fn foo() -> usize {
5142 /// This routine checks if the final statement in a block is an
5143 /// expression with an explicit semicolon whose type is compatible
5144 /// with `expected_ty`. If so, it suggests removing the semicolon.
5145 fn consider_hint_about_removing_semicolon(
5147 blk: &'tcx hir::Block<'tcx>,
5148 expected_ty: Ty<'tcx>,
5149 err: &mut DiagnosticBuilder<'_>,
5151 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
5152 err.span_suggestion(
5154 "consider removing this semicolon",
5156 Applicability::MachineApplicable,
5161 fn could_remove_semicolon(
5163 blk: &'tcx hir::Block<'tcx>,
5164 expected_ty: Ty<'tcx>,
5166 // Be helpful when the user wrote `{... expr;}` and
5167 // taking the `;` off is enough to fix the error.
5168 let last_stmt = blk.stmts.last()?;
5169 let last_expr = match last_stmt.kind {
5170 hir::StmtKind::Semi(ref e) => e,
5173 let last_expr_ty = self.node_ty(last_expr.hir_id);
5174 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
5177 let original_span = original_sp(last_stmt.span, blk.span);
5178 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
5181 // Instantiates the given path, which must refer to an item with the given
5182 // number of type parameters and type.
5183 pub fn instantiate_value_path(
5185 segments: &[hir::PathSegment<'_>],
5186 self_ty: Option<Ty<'tcx>>,
5190 ) -> (Ty<'tcx>, Res) {
5192 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
5193 segments, self_ty, res, hir_id,
5198 let path_segs = match res {
5199 Res::Local(_) | Res::SelfCtor(_) => vec![],
5200 Res::Def(kind, def_id) => {
5201 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id)
5203 _ => bug!("instantiate_value_path on {:?}", res),
5206 let mut user_self_ty = None;
5207 let mut is_alias_variant_ctor = false;
5209 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
5210 if let Some(self_ty) = self_ty {
5211 let adt_def = self_ty.ty_adt_def().unwrap();
5212 user_self_ty = Some(UserSelfTy { impl_def_id: adt_def.did, self_ty });
5213 is_alias_variant_ctor = true;
5216 Res::Def(DefKind::Method, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
5217 let container = tcx.associated_item(def_id).container;
5218 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
5220 ty::TraitContainer(trait_did) => {
5221 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
5223 ty::ImplContainer(impl_def_id) => {
5224 if segments.len() == 1 {
5225 // `<T>::assoc` will end up here, and so
5226 // can `T::assoc`. It this came from an
5227 // inherent impl, we need to record the
5228 // `T` for posterity (see `UserSelfTy` for
5230 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
5231 user_self_ty = Some(UserSelfTy { impl_def_id, self_ty });
5239 // Now that we have categorized what space the parameters for each
5240 // segment belong to, let's sort out the parameters that the user
5241 // provided (if any) into their appropriate spaces. We'll also report
5242 // errors if type parameters are provided in an inappropriate place.
5244 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
5245 let generics_has_err = AstConv::prohibit_generics(
5247 segments.iter().enumerate().filter_map(|(index, seg)| {
5248 if !generic_segs.contains(&index) || is_alias_variant_ctor {
5256 if let Res::Local(hid) = res {
5257 let ty = self.local_ty(span, hid).decl_ty;
5258 let ty = self.normalize_associated_types_in(span, &ty);
5259 self.write_ty(hir_id, ty);
5263 if generics_has_err {
5264 // Don't try to infer type parameters when prohibited generic arguments were given.
5265 user_self_ty = None;
5268 // Now we have to compare the types that the user *actually*
5269 // provided against the types that were *expected*. If the user
5270 // did not provide any types, then we want to substitute inference
5271 // variables. If the user provided some types, we may still need
5272 // to add defaults. If the user provided *too many* types, that's
5275 let mut infer_args_for_err = FxHashSet::default();
5276 for &PathSeg(def_id, index) in &path_segs {
5277 let seg = &segments[index];
5278 let generics = tcx.generics_of(def_id);
5279 // Argument-position `impl Trait` is treated as a normal generic
5280 // parameter internally, but we don't allow users to specify the
5281 // parameter's value explicitly, so we have to do some error-
5283 let suppress_errors = AstConv::check_generic_arg_count_for_call(
5284 tcx, span, &generics, &seg, false, // `is_method_call`
5286 if suppress_errors {
5287 infer_args_for_err.insert(index);
5288 self.set_tainted_by_errors(); // See issue #53251.
5292 let has_self = path_segs
5294 .map(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self)
5297 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
5298 let ty = self.impl_self_ty(span, impl_def_id).ty;
5299 let adt_def = ty.ty_adt_def();
5302 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
5303 let variant = adt_def.non_enum_variant();
5304 let ctor_def_id = variant.ctor_def_id.unwrap();
5306 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
5311 let mut err = tcx.sess.struct_span_err(
5313 "the `Self` constructor can only be used with tuple or unit structs",
5315 if let Some(adt_def) = adt_def {
5316 match adt_def.adt_kind() {
5318 err.help("did you mean to use one of the enum's variants?");
5320 AdtKind::Struct | AdtKind::Union => {
5321 err.span_suggestion(
5323 "use curly brackets",
5324 String::from("Self { /* fields */ }"),
5325 Applicability::HasPlaceholders,
5332 return (tcx.types.err, res);
5338 let def_id = res.def_id();
5340 // The things we are substituting into the type should not contain
5341 // escaping late-bound regions, and nor should the base type scheme.
5342 let ty = tcx.type_of(def_id);
5344 let substs = self_ctor_substs.unwrap_or_else(|| {
5345 AstConv::create_substs_for_generic_args(
5351 // Provide the generic args, and whether types should be inferred.
5353 if let Some(&PathSeg(_, index)) =
5354 path_segs.iter().find(|&PathSeg(did, _)| *did == def_id)
5356 // If we've encountered an `impl Trait`-related error, we're just
5357 // going to infer the arguments for better error messages.
5358 if !infer_args_for_err.contains(&index) {
5359 // Check whether the user has provided generic arguments.
5360 if let Some(ref data) = segments[index].args {
5361 return (Some(data), segments[index].infer_args);
5364 return (None, segments[index].infer_args);
5369 // Provide substitutions for parameters for which (valid) arguments have been provided.
5370 |param, arg| match (¶m.kind, arg) {
5371 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
5372 AstConv::ast_region_to_region(self, lt, Some(param)).into()
5374 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
5375 self.to_ty(ty).into()
5377 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
5378 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
5380 _ => unreachable!(),
5382 // Provide substitutions for parameters for which arguments are inferred.
5383 |substs, param, infer_args| {
5385 GenericParamDefKind::Lifetime => {
5386 self.re_infer(Some(param), span).unwrap().into()
5388 GenericParamDefKind::Type { has_default, .. } => {
5389 if !infer_args && has_default {
5390 // If we have a default, then we it doesn't matter that we're not
5391 // inferring the type arguments: we provide the default where any
5393 let default = tcx.type_of(param.def_id);
5396 default.subst_spanned(tcx, substs.unwrap(), Some(span)),
5400 // If no type arguments were provided, we have to infer them.
5401 // This case also occurs as a result of some malformed input, e.g.
5402 // a lifetime argument being given instead of a type parameter.
5403 // Using inference instead of `Error` gives better error messages.
5404 self.var_for_def(span, param)
5407 GenericParamDefKind::Const => {
5408 // FIXME(const_generics:defaults)
5409 // No const parameters were provided, we have to infer them.
5410 self.var_for_def(span, param)
5416 assert!(!substs.has_escaping_bound_vars());
5417 assert!(!ty.has_escaping_bound_vars());
5419 // First, store the "user substs" for later.
5420 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
5422 self.add_required_obligations(span, def_id, &substs);
5424 // Substitute the values for the type parameters into the type of
5425 // the referenced item.
5426 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
5428 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
5429 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
5430 // is inherent, there is no `Self` parameter; instead, the impl needs
5431 // type parameters, which we can infer by unifying the provided `Self`
5432 // with the substituted impl type.
5433 // This also occurs for an enum variant on a type alias.
5434 let ty = tcx.type_of(impl_def_id);
5436 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
5437 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
5438 Ok(ok) => self.register_infer_ok_obligations(ok),
5440 self.tcx.sess.delay_span_bug(span, &format!(
5441 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
5449 self.check_rustc_args_require_const(def_id, hir_id, span);
5451 debug!("instantiate_value_path: type of {:?} is {:?}", hir_id, ty_substituted);
5452 self.write_substs(hir_id, substs);
5454 (ty_substituted, res)
5457 /// Add all the obligations that are required, substituting and normalized appropriately.
5458 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
5459 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
5461 for (i, mut obligation) in traits::predicates_for_generics(
5462 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
5469 // This makes the error point at the bound, but we want to point at the argument
5470 if let Some(span) = spans.get(i) {
5471 obligation.cause.code = traits::BindingObligation(def_id, *span);
5473 self.register_predicate(obligation);
5477 fn check_rustc_args_require_const(&self, def_id: DefId, hir_id: hir::HirId, span: Span) {
5478 // We're only interested in functions tagged with
5479 // #[rustc_args_required_const], so ignore anything that's not.
5480 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5484 // If our calling expression is indeed the function itself, we're good!
5485 // If not, generate an error that this can only be called directly.
5486 if let Node::Expr(expr) = self.tcx.hir().get(self.tcx.hir().get_parent_node(hir_id)) {
5487 if let ExprKind::Call(ref callee, ..) = expr.kind {
5488 if callee.hir_id == hir_id {
5494 self.tcx.sess.span_err(
5496 "this function can only be invoked \
5497 directly, not through a function pointer",
5501 /// Resolves `typ` by a single level if `typ` is a type variable.
5502 /// If no resolution is possible, then an error is reported.
5503 /// Numeric inference variables may be left unresolved.
5504 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5505 let ty = self.resolve_vars_with_obligations(ty);
5506 if !ty.is_ty_var() {
5509 if !self.is_tainted_by_errors() {
5510 self.need_type_info_err((**self).body_id, sp, ty, E0282)
5511 .note("type must be known at this point")
5514 self.demand_suptype(sp, self.tcx.types.err, ty);
5519 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5522 ctxt: BreakableCtxt<'tcx>,
5524 ) -> (BreakableCtxt<'tcx>, R) {
5527 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5528 index = enclosing_breakables.stack.len();
5529 enclosing_breakables.by_id.insert(id, index);
5530 enclosing_breakables.stack.push(ctxt);
5534 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5535 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5536 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5537 enclosing_breakables.stack.pop().expect("missing breakable context")
5542 /// Instantiate a QueryResponse in a probe context, without a
5543 /// good ObligationCause.
5544 fn probe_instantiate_query_response(
5547 original_values: &OriginalQueryValues<'tcx>,
5548 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5549 ) -> InferResult<'tcx, Ty<'tcx>> {
5550 self.instantiate_query_response_and_region_obligations(
5551 &traits::ObligationCause::misc(span, self.body_id),
5558 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5559 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5560 let mut contained_in_place = false;
5562 while let hir::Node::Expr(parent_expr) =
5563 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5565 match &parent_expr.kind {
5566 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5567 if lhs.hir_id == expr_id {
5568 contained_in_place = true;
5574 expr_id = parent_expr.hir_id;
5581 pub fn check_bounds_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5582 let own_counts = generics.own_counts();
5584 "check_bounds_are_used(n_tys={}, n_cts={}, ty={:?})",
5585 own_counts.types, own_counts.consts, ty
5588 if own_counts.types == 0 {
5592 // Make a vector of booleans initially `false`; set to `true` when used.
5593 let mut types_used = vec![false; own_counts.types];
5595 for leaf_ty in ty.walk() {
5596 if let ty::Param(ty::ParamTy { index, .. }) = leaf_ty.kind {
5597 debug!("found use of ty param num {}", index);
5598 types_used[index as usize - own_counts.lifetimes] = true;
5599 } else if let ty::Error = leaf_ty.kind {
5600 // If there is already another error, do not emit
5601 // an error for not using a type parameter.
5602 assert!(tcx.sess.has_errors());
5607 let types = generics.params.iter().filter(|param| match param.kind {
5608 ty::GenericParamDefKind::Type { .. } => true,
5611 for (&used, param) in types_used.iter().zip(types) {
5613 let id = tcx.hir().as_local_hir_id(param.def_id).unwrap();
5614 let span = tcx.hir().span(id);
5615 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5616 .span_label(span, "unused type parameter")
5622 fn fatally_break_rust(sess: &Session) {
5623 let handler = sess.diagnostic();
5624 handler.span_bug_no_panic(
5626 "It looks like you're trying to break rust; would you like some ICE?",
5628 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5629 handler.note_without_error(
5630 "we would appreciate a joke overview: \
5631 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
5633 handler.note_without_error(&format!(
5634 "rustc {} running on {}",
5635 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5636 crate::session::config::host_triple(),
5640 fn potentially_plural_count(count: usize, word: &str) -> String {
5641 format!("{} {}{}", count, word, pluralize!(count))