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, GenericArgCountMismatch, PathSeg};
92 use rustc_ast::util::parser::ExprPrecedence;
93 use rustc_attr as attr;
94 use rustc_data_structures::captures::Captures;
95 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
96 use rustc_errors::ErrorReported;
97 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, DiagnosticId};
99 use rustc_hir::def::{CtorOf, DefKind, Res};
100 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet, LocalDefId, LOCAL_CRATE};
101 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
102 use rustc_hir::itemlikevisit::ItemLikeVisitor;
103 use rustc_hir::lang_items;
104 use rustc_hir::{ExprKind, GenericArg, HirIdMap, Item, ItemKind, Node, PatKind, QPath};
105 use rustc_index::bit_set::BitSet;
106 use rustc_index::vec::Idx;
107 use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
108 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
109 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
110 use rustc_infer::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
111 use rustc_infer::infer::{self, InferCtxt, InferOk, InferResult, TyCtxtInferExt};
112 use rustc_middle::hir::map::blocks::FnLikeNode;
113 use rustc_middle::middle::region;
114 use rustc_middle::mir::interpret::ConstValue;
115 use rustc_middle::ty::adjustment::{
116 Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast,
118 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
119 use rustc_middle::ty::query::Providers;
120 use rustc_middle::ty::subst::{
121 GenericArgKind, InternalSubsts, Subst, SubstsRef, UserSelfTy, UserSubsts,
123 use rustc_middle::ty::util::{Discr, IntTypeExt, Representability};
124 use rustc_middle::ty::{
125 self, AdtKind, CanonicalUserType, Const, GenericParamDefKind, RegionKind, ToPolyTraitRef,
126 ToPredicate, Ty, TyCtxt, UserType, WithConstness,
128 use rustc_session::config::{self, EntryFnType};
129 use rustc_session::lint;
130 use rustc_session::parse::feature_err;
131 use rustc_session::Session;
132 use rustc_span::hygiene::DesugaringKind;
133 use rustc_span::source_map::{original_sp, DUMMY_SP};
134 use rustc_span::symbol::{kw, sym, Ident};
135 use rustc_span::{self, BytePos, MultiSpan, Span};
136 use rustc_target::abi::VariantIdx;
137 use rustc_target::spec::abi::Abi;
138 use rustc_trait_selection::infer::InferCtxtExt as _;
139 use rustc_trait_selection::opaque_types::{InferCtxtExt as _, OpaqueTypeDecl};
140 use rustc_trait_selection::traits::error_reporting::recursive_type_with_infinite_size_error;
141 use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
142 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
143 use rustc_trait_selection::traits::{
144 self, ObligationCause, ObligationCauseCode, TraitEngine, TraitEngineExt,
147 use std::cell::{Cell, Ref, RefCell, RefMut};
149 use std::collections::hash_map::Entry;
151 use std::mem::replace;
152 use std::ops::{self, Deref};
155 use crate::require_c_abi_if_c_variadic;
156 use crate::util::common::indenter;
158 use self::autoderef::Autoderef;
159 use self::callee::DeferredCallResolution;
160 use self::coercion::{CoerceMany, DynamicCoerceMany};
161 use self::compare_method::{compare_const_impl, compare_impl_method, compare_ty_impl};
162 use self::method::{MethodCallee, SelfSource};
163 pub use self::Expectation::*;
164 use self::TupleArgumentsFlag::*;
167 macro_rules! type_error_struct {
168 ($session:expr, $span:expr, $typ:expr, $code:ident, $($message:tt)*) => ({
169 if $typ.references_error() {
170 $session.diagnostic().struct_dummy()
172 rustc_errors::struct_span_err!($session, $span, $code, $($message)*)
177 /// The type of a local binding, including the revealed type for anon types.
178 #[derive(Copy, Clone, Debug)]
179 pub struct LocalTy<'tcx> {
181 revealed_ty: Ty<'tcx>,
184 /// A wrapper for `InferCtxt`'s `in_progress_tables` field.
185 #[derive(Copy, Clone)]
186 struct MaybeInProgressTables<'a, 'tcx> {
187 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
190 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
191 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
192 match self.maybe_tables {
193 Some(tables) => tables.borrow(),
194 None => bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables"),
198 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
199 match self.maybe_tables {
200 Some(tables) => tables.borrow_mut(),
201 None => bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables"),
206 /// Closures defined within the function. For example:
209 /// bar(move|| { ... })
212 /// Here, the function `foo()` and the closure passed to
213 /// `bar()` will each have their own `FnCtxt`, but they will
214 /// share the inherited fields.
215 pub struct Inherited<'a, 'tcx> {
216 infcx: InferCtxt<'a, 'tcx>,
218 tables: MaybeInProgressTables<'a, 'tcx>,
220 locals: RefCell<HirIdMap<LocalTy<'tcx>>>,
222 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
224 // Some additional `Sized` obligations badly affect type inference.
225 // These obligations are added in a later stage of typeck.
226 deferred_sized_obligations: RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
228 // When we process a call like `c()` where `c` is a closure type,
229 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
230 // `FnOnce` closure. In that case, we defer full resolution of the
231 // call until upvar inference can kick in and make the
232 // decision. We keep these deferred resolutions grouped by the
233 // def-id of the closure, so that once we decide, we can easily go
234 // back and process them.
235 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'tcx>>>>,
237 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
239 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
241 // Opaque types found in explicit return types and their
242 // associated fresh inference variable. Writeback resolves these
243 // variables to get the concrete type, which can be used to
244 // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
245 opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
247 /// A map from inference variables created from opaque
248 /// type instantiations (`ty::Infer`) to the actual opaque
249 /// type (`ty::Opaque`). Used during fallback to map unconstrained
250 /// opaque type inference variables to their corresponding
252 opaque_types_vars: RefCell<FxHashMap<Ty<'tcx>, Ty<'tcx>>>,
254 /// Each type parameter has an implicit region bound that
255 /// indicates it must outlive at least the function body (the user
256 /// may specify stronger requirements). This field indicates the
257 /// region of the callee. If it is `None`, then the parameter
258 /// environment is for an item or something where the "callee" is
260 implicit_region_bound: Option<ty::Region<'tcx>>,
262 body_id: Option<hir::BodyId>,
265 impl<'a, 'tcx> Deref for Inherited<'a, 'tcx> {
266 type Target = InferCtxt<'a, 'tcx>;
267 fn deref(&self) -> &Self::Target {
272 /// When type-checking an expression, we propagate downward
273 /// whatever type hint we are able in the form of an `Expectation`.
274 #[derive(Copy, Clone, Debug)]
275 pub enum Expectation<'tcx> {
276 /// We know nothing about what type this expression should have.
279 /// This expression should have the type given (or some subtype).
280 ExpectHasType(Ty<'tcx>),
282 /// This expression will be cast to the `Ty`.
283 ExpectCastableToType(Ty<'tcx>),
285 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
286 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
287 ExpectRvalueLikeUnsized(Ty<'tcx>),
290 impl<'a, 'tcx> Expectation<'tcx> {
291 // Disregard "castable to" expectations because they
292 // can lead us astray. Consider for example `if cond
293 // {22} else {c} as u8` -- if we propagate the
294 // "castable to u8" constraint to 22, it will pick the
295 // type 22u8, which is overly constrained (c might not
296 // be a u8). In effect, the problem is that the
297 // "castable to" expectation is not the tightest thing
298 // we can say, so we want to drop it in this case.
299 // The tightest thing we can say is "must unify with
300 // else branch". Note that in the case of a "has type"
301 // constraint, this limitation does not hold.
303 // If the expected type is just a type variable, then don't use
304 // an expected type. Otherwise, we might write parts of the type
305 // when checking the 'then' block which are incompatible with the
307 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
309 ExpectHasType(ety) => {
310 let ety = fcx.shallow_resolve(ety);
311 if !ety.is_ty_var() { ExpectHasType(ety) } else { NoExpectation }
313 ExpectRvalueLikeUnsized(ety) => ExpectRvalueLikeUnsized(ety),
318 /// Provides an expectation for an rvalue expression given an *optional*
319 /// hint, which is not required for type safety (the resulting type might
320 /// be checked higher up, as is the case with `&expr` and `box expr`), but
321 /// is useful in determining the concrete type.
323 /// The primary use case is where the expected type is a fat pointer,
324 /// like `&[isize]`. For example, consider the following statement:
326 /// let x: &[isize] = &[1, 2, 3];
328 /// In this case, the expected type for the `&[1, 2, 3]` expression is
329 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
330 /// expectation `ExpectHasType([isize])`, that would be too strong --
331 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
332 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
333 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
334 /// which still is useful, because it informs integer literals and the like.
335 /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
336 /// for examples of where this comes up,.
337 fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
338 match fcx.tcx.struct_tail_without_normalization(ty).kind {
339 ty::Slice(_) | ty::Str | ty::Dynamic(..) => ExpectRvalueLikeUnsized(ty),
340 _ => ExpectHasType(ty),
344 // Resolves `expected` by a single level if it is a variable. If
345 // there is no expected type or resolution is not possible (e.g.,
346 // no constraints yet present), just returns `None`.
347 fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
349 NoExpectation => NoExpectation,
350 ExpectCastableToType(t) => ExpectCastableToType(fcx.resolve_vars_if_possible(&t)),
351 ExpectHasType(t) => ExpectHasType(fcx.resolve_vars_if_possible(&t)),
352 ExpectRvalueLikeUnsized(t) => ExpectRvalueLikeUnsized(fcx.resolve_vars_if_possible(&t)),
356 fn to_option(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
357 match self.resolve(fcx) {
358 NoExpectation => None,
359 ExpectCastableToType(ty) | ExpectHasType(ty) | ExpectRvalueLikeUnsized(ty) => Some(ty),
363 /// It sometimes happens that we want to turn an expectation into
364 /// a **hard constraint** (i.e., something that must be satisfied
365 /// for the program to type-check). `only_has_type` will return
366 /// such a constraint, if it exists.
367 fn only_has_type(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
368 match self.resolve(fcx) {
369 ExpectHasType(ty) => Some(ty),
370 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
374 /// Like `only_has_type`, but instead of returning `None` if no
375 /// hard constraint exists, creates a fresh type variable.
376 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> Ty<'tcx> {
377 self.only_has_type(fcx).unwrap_or_else(|| {
378 fcx.next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span })
383 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
390 fn maybe_mut_place(m: hir::Mutability) -> Self {
392 hir::Mutability::Mut => Needs::MutPlace,
393 hir::Mutability::Not => Needs::None,
398 #[derive(Copy, Clone)]
399 pub struct UnsafetyState {
401 pub unsafety: hir::Unsafety,
402 pub unsafe_push_count: u32,
407 pub fn function(unsafety: hir::Unsafety, def: hir::HirId) -> UnsafetyState {
408 UnsafetyState { def, unsafety, unsafe_push_count: 0, from_fn: true }
411 pub fn recurse(&mut self, blk: &hir::Block<'_>) -> UnsafetyState {
412 use hir::BlockCheckMode;
413 match self.unsafety {
414 // If this unsafe, then if the outer function was already marked as
415 // unsafe we shouldn't attribute the unsafe'ness to the block. This
416 // way the block can be warned about instead of ignoring this
417 // extraneous block (functions are never warned about).
418 hir::Unsafety::Unsafe if self.from_fn => *self,
421 let (unsafety, def, count) = match blk.rules {
422 BlockCheckMode::PushUnsafeBlock(..) => {
423 (unsafety, blk.hir_id, self.unsafe_push_count.checked_add(1).unwrap())
425 BlockCheckMode::PopUnsafeBlock(..) => {
426 (unsafety, blk.hir_id, self.unsafe_push_count.checked_sub(1).unwrap())
428 BlockCheckMode::UnsafeBlock(..) => {
429 (hir::Unsafety::Unsafe, blk.hir_id, self.unsafe_push_count)
431 BlockCheckMode::DefaultBlock => (unsafety, self.def, self.unsafe_push_count),
433 UnsafetyState { def, unsafety, unsafe_push_count: count, from_fn: false }
439 #[derive(Debug, Copy, Clone)]
445 /// Tracks whether executing a node may exit normally (versus
446 /// return/break/panic, which "diverge", leaving dead code in their
447 /// wake). Tracked semi-automatically (through type variables marked
448 /// as diverging), with some manual adjustments for control-flow
449 /// primitives (approximating a CFG).
450 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
452 /// Potentially unknown, some cases converge,
453 /// others require a CFG to determine them.
456 /// Definitely known to diverge and therefore
457 /// not reach the next sibling or its parent.
459 /// The `Span` points to the expression
460 /// that caused us to diverge
461 /// (e.g. `return`, `break`, etc).
463 /// In some cases (e.g. a `match` expression
464 /// where all arms diverge), we may be
465 /// able to provide a more informative
466 /// message to the user.
467 /// If this is `None`, a default message
468 /// will be generated, which is suitable
470 custom_note: Option<&'static str>,
473 /// Same as `Always` but with a reachability
474 /// warning already emitted.
478 // Convenience impls for combining `Diverges`.
480 impl ops::BitAnd for Diverges {
482 fn bitand(self, other: Self) -> Self {
483 cmp::min(self, other)
487 impl ops::BitOr for Diverges {
489 fn bitor(self, other: Self) -> Self {
490 cmp::max(self, other)
494 impl ops::BitAndAssign for Diverges {
495 fn bitand_assign(&mut self, other: Self) {
496 *self = *self & other;
500 impl ops::BitOrAssign for Diverges {
501 fn bitor_assign(&mut self, other: Self) {
502 *self = *self | other;
507 /// Creates a `Diverges::Always` with the provided `span` and the default note message.
508 fn always(span: Span) -> Diverges {
509 Diverges::Always { span, custom_note: None }
512 fn is_always(self) -> bool {
513 // Enum comparison ignores the
514 // contents of fields, so we just
515 // fill them in with garbage here.
516 self >= Diverges::Always { span: DUMMY_SP, custom_note: None }
520 pub struct BreakableCtxt<'tcx> {
523 // this is `null` for loops where break with a value is illegal,
524 // such as `while`, `for`, and `while let`
525 coerce: Option<DynamicCoerceMany<'tcx>>,
528 pub struct EnclosingBreakables<'tcx> {
529 stack: Vec<BreakableCtxt<'tcx>>,
530 by_id: HirIdMap<usize>,
533 impl<'tcx> EnclosingBreakables<'tcx> {
534 fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
535 self.opt_find_breakable(target_id).unwrap_or_else(|| {
536 bug!("could not find enclosing breakable with id {}", target_id);
540 fn opt_find_breakable(&mut self, target_id: hir::HirId) -> Option<&mut BreakableCtxt<'tcx>> {
541 match self.by_id.get(&target_id) {
542 Some(ix) => Some(&mut self.stack[*ix]),
548 pub struct FnCtxt<'a, 'tcx> {
551 /// The parameter environment used for proving trait obligations
552 /// in this function. This can change when we descend into
553 /// closures (as they bring new things into scope), hence it is
554 /// not part of `Inherited` (as of the time of this writing,
555 /// closures do not yet change the environment, but they will
557 param_env: ty::ParamEnv<'tcx>,
559 /// Number of errors that had been reported when we started
560 /// checking this function. On exit, if we find that *more* errors
561 /// have been reported, we will skip regionck and other work that
562 /// expects the types within the function to be consistent.
563 // FIXME(matthewjasper) This should not exist, and it's not correct
564 // if type checking is run in parallel.
565 err_count_on_creation: usize,
567 /// If `Some`, this stores coercion information for returned
568 /// expressions. If `None`, this is in a context where return is
569 /// inappropriate, such as a const expression.
571 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
572 /// can track all the return expressions and then use them to
573 /// compute a useful coercion from the set, similar to a match
574 /// expression or other branching context. You can use methods
575 /// like `expected_ty` to access the declared return type (if
577 ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
579 /// First span of a return site that we find. Used in error messages.
580 ret_coercion_span: RefCell<Option<Span>>,
582 resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
584 ps: RefCell<UnsafetyState>,
586 /// Whether the last checked node generates a divergence (e.g.,
587 /// `return` will set this to `Always`). In general, when entering
588 /// an expression or other node in the tree, the initial value
589 /// indicates whether prior parts of the containing expression may
590 /// have diverged. It is then typically set to `Maybe` (and the
591 /// old value remembered) for processing the subparts of the
592 /// current expression. As each subpart is processed, they may set
593 /// the flag to `Always`, etc. Finally, at the end, we take the
594 /// result and "union" it with the original value, so that when we
595 /// return the flag indicates if any subpart of the parent
596 /// expression (up to and including this part) has diverged. So,
597 /// if you read it after evaluating a subexpression `X`, the value
598 /// you get indicates whether any subexpression that was
599 /// evaluating up to and including `X` diverged.
601 /// We currently use this flag only for diagnostic purposes:
603 /// - To warn about unreachable code: if, after processing a
604 /// sub-expression but before we have applied the effects of the
605 /// current node, we see that the flag is set to `Always`, we
606 /// can issue a warning. This corresponds to something like
607 /// `foo(return)`; we warn on the `foo()` expression. (We then
608 /// update the flag to `WarnedAlways` to suppress duplicate
609 /// reports.) Similarly, if we traverse to a fresh statement (or
610 /// tail expression) from a `Always` setting, we will issue a
611 /// warning. This corresponds to something like `{return;
612 /// foo();}` or `{return; 22}`, where we would warn on the
615 /// An expression represents dead code if, after checking it,
616 /// the diverges flag is set to something other than `Maybe`.
617 diverges: Cell<Diverges>,
619 /// Whether any child nodes have any type errors.
620 has_errors: Cell<bool>,
622 enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
624 inh: &'a Inherited<'a, 'tcx>,
627 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
628 type Target = Inherited<'a, 'tcx>;
629 fn deref(&self) -> &Self::Target {
634 /// Helper type of a temporary returned by `Inherited::build(...)`.
635 /// Necessary because we can't write the following bound:
636 /// `F: for<'b, 'tcx> where 'tcx FnOnce(Inherited<'b, 'tcx>)`.
637 pub struct InheritedBuilder<'tcx> {
638 infcx: infer::InferCtxtBuilder<'tcx>,
642 impl Inherited<'_, 'tcx> {
643 pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
644 let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
647 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_owner),
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: LocalDefId) -> Self {
666 let item_id = tcx.hir().local_def_id_to_hir_id(def_id);
667 let body_id = tcx.hir().maybe_body_owned_by(item_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 visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
743 tcx.hir().krate().par_visit_all_item_likes(&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.to_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::Fn(ref sig, hir::TraitFn::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::Fn(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 // FIXME(#71104) Should really be using just `as_local_hir_id` but
842 // some `LocalDefId` do not seem to have a corresponding HirId.
844 def_id.as_local().and_then(|def_id| tcx.hir().opt_local_def_id_to_hir_id(def_id))
846 primary_body_of(tcx, id).is_some()
852 fn used_trait_imports(tcx: TyCtxt<'_>, def_id: DefId) -> &DefIdSet {
853 &*tcx.typeck_tables_of(def_id).used_trait_imports
856 /// Inspects the substs of opaque types, replacing any inference variables
857 /// with proper generic parameter from the identity substs.
859 /// This is run after we normalize the function signature, to fix any inference
860 /// variables introduced by the projection of associated types. This ensures that
861 /// any opaque types used in the signature continue to refer to generic parameters,
862 /// allowing them to be considered for defining uses in the function body
864 /// For example, consider this code.
869 /// fn use_it(self) -> Self::MyItem
871 /// impl<T, I> MyTrait for T where T: Iterator<Item = I> {
872 /// type MyItem = impl Iterator<Item = I>;
873 /// fn use_it(self) -> Self::MyItem {
879 /// When we normalize the signature of `use_it` from the impl block,
880 /// we will normalize `Self::MyItem` to the opaque type `impl Iterator<Item = I>`
881 /// However, this projection result may contain inference variables, due
882 /// to the way that projection works. We didn't have any inference variables
883 /// in the signature to begin with - leaving them in will cause us to incorrectly
884 /// conclude that we don't have a defining use of `MyItem`. By mapping inference
885 /// variables back to the actual generic parameters, we will correctly see that
886 /// we have a defining use of `MyItem`
887 fn fixup_opaque_types<'tcx, T>(tcx: TyCtxt<'tcx>, val: &T) -> T
889 T: TypeFoldable<'tcx>,
891 struct FixupFolder<'tcx> {
895 impl<'tcx> TypeFolder<'tcx> for FixupFolder<'tcx> {
896 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
900 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
902 ty::Opaque(def_id, substs) => {
903 debug!("fixup_opaque_types: found type {:?}", ty);
904 // Here, we replace any inference variables that occur within
905 // the substs of an opaque type. By definition, any type occurring
906 // in the substs has a corresponding generic parameter, which is what
907 // we replace it with.
908 // This replacement is only run on the function signature, so any
909 // inference variables that we come across must be the rust of projection
910 // (there's no other way for a user to get inference variables into
911 // a function signature).
912 if ty.needs_infer() {
913 let new_substs = InternalSubsts::for_item(self.tcx, def_id, |param, _| {
914 let old_param = substs[param.index as usize];
915 match old_param.unpack() {
916 GenericArgKind::Type(old_ty) => {
917 if let ty::Infer(_) = old_ty.kind {
918 // Replace inference type with a generic parameter
919 self.tcx.mk_param_from_def(param)
921 old_param.fold_with(self)
924 GenericArgKind::Const(old_const) => {
925 if let ty::ConstKind::Infer(_) = old_const.val {
926 // This should never happen - we currently do not support
927 // 'const projections', e.g.:
928 // `impl<T: SomeTrait> MyTrait for T where <T as SomeTrait>::MyConst == 25`
929 // which should be the only way for us to end up with a const inference
930 // variable after projection. If Rust ever gains support for this kind
931 // of projection, this should *probably* be changed to
932 // `self.tcx.mk_param_from_def(param)`
934 "Found infer const: `{:?}` in opaque type: {:?}",
939 old_param.fold_with(self)
942 GenericArgKind::Lifetime(old_region) => {
943 if let RegionKind::ReVar(_) = old_region {
944 self.tcx.mk_param_from_def(param)
946 old_param.fold_with(self)
951 let new_ty = self.tcx.mk_opaque(def_id, new_substs);
952 debug!("fixup_opaque_types: new type: {:?}", new_ty);
958 _ => ty.super_fold_with(self),
963 debug!("fixup_opaque_types({:?})", val);
964 val.fold_with(&mut FixupFolder { tcx })
967 fn typeck_tables_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &ty::TypeckTables<'tcx> {
968 let fallback = move || tcx.type_of(def_id);
969 typeck_tables_of_with_fallback(tcx, def_id, fallback)
972 /// Used only to get `TypeckTables` for type inference during error recovery.
973 /// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
974 fn diagnostic_only_typeck_tables_of<'tcx>(
977 ) -> &ty::TypeckTables<'tcx> {
978 assert!(def_id.is_local());
979 let fallback = move || {
980 let span = tcx.hir().span(tcx.hir().as_local_hir_id(def_id).unwrap());
981 tcx.sess.delay_span_bug(span, "diagnostic only typeck table used");
984 typeck_tables_of_with_fallback(tcx, def_id, fallback)
987 fn typeck_tables_of_with_fallback<'tcx>(
990 fallback: impl Fn() -> Ty<'tcx> + 'tcx,
991 ) -> &'tcx ty::TypeckTables<'tcx> {
992 // Closures' tables come from their outermost function,
993 // as they are part of the same "inference environment".
994 let outer_def_id = tcx.closure_base_def_id(def_id);
995 if outer_def_id != def_id {
996 return tcx.typeck_tables_of(outer_def_id);
999 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
1000 let span = tcx.hir().span(id);
1002 // Figure out what primary body this item has.
1003 let (body_id, body_ty, fn_header, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
1004 span_bug!(span, "can't type-check body of {:?}", def_id);
1006 let body = tcx.hir().body(body_id);
1008 let tables = Inherited::build(tcx, def_id.expect_local()).enter(|inh| {
1009 let param_env = tcx.param_env(def_id);
1010 let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
1011 let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
1012 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
1018 &hir::Generics::empty(),
1025 check_abi(tcx, span, fn_sig.abi());
1027 // Compute the fty from point of view of inside the fn.
1028 let fn_sig = tcx.liberate_late_bound_regions(def_id, &fn_sig);
1029 let fn_sig = inh.normalize_associated_types_in(
1036 let fn_sig = fixup_opaque_types(tcx, &fn_sig);
1038 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
1041 let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
1042 let expected_type = body_ty
1043 .and_then(|ty| match ty.kind {
1044 hir::TyKind::Infer => Some(AstConv::ast_ty_to_ty(&fcx, ty)),
1047 .unwrap_or_else(fallback);
1048 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
1049 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
1051 let revealed_ty = if tcx.features().impl_trait_in_bindings {
1052 fcx.instantiate_opaque_types_from_value(id, &expected_type, body.value.span)
1057 // Gather locals in statics (because of block expressions).
1058 GatherLocalsVisitor { fcx: &fcx, parent_id: id }.visit_body(body);
1060 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
1062 fcx.write_ty(id, revealed_ty);
1067 // All type checking constraints were added, try to fallback unsolved variables.
1068 fcx.select_obligations_where_possible(false, |_| {});
1069 let mut fallback_has_occurred = false;
1071 // We do fallback in two passes, to try to generate
1072 // better error messages.
1073 // The first time, we do *not* replace opaque types.
1074 for ty in &fcx.unsolved_variables() {
1075 fallback_has_occurred |= fcx.fallback_if_possible(ty, FallbackMode::NoOpaque);
1077 // We now see if we can make progress. This might
1078 // cause us to unify inference variables for opaque types,
1079 // since we may have unified some other type variables
1080 // during the first phase of fallback.
1081 // This means that we only replace inference variables with their underlying
1082 // opaque types as a last resort.
1084 // In code like this:
1087 // type MyType = impl Copy;
1088 // fn produce() -> MyType { true }
1089 // fn bad_produce() -> MyType { panic!() }
1092 // we want to unify the opaque inference variable in `bad_produce`
1093 // with the diverging fallback for `panic!` (e.g. `()` or `!`).
1094 // This will produce a nice error message about conflicting concrete
1095 // types for `MyType`.
1097 // If we had tried to fallback the opaque inference variable to `MyType`,
1098 // we will generate a confusing type-check error that does not explicitly
1099 // refer to opaque types.
1100 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
1102 // We now run fallback again, but this time we allow it to replace
1103 // unconstrained opaque type variables, in addition to performing
1104 // other kinds of fallback.
1105 for ty in &fcx.unsolved_variables() {
1106 fallback_has_occurred |= fcx.fallback_if_possible(ty, FallbackMode::All);
1109 // See if we can make any more progress.
1110 fcx.select_obligations_where_possible(fallback_has_occurred, |_| {});
1112 // Even though coercion casts provide type hints, we check casts after fallback for
1113 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
1116 // Closure and generator analysis may run after fallback
1117 // because they don't constrain other type variables.
1118 fcx.closure_analyze(body);
1119 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
1120 fcx.resolve_generator_interiors(def_id);
1122 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
1123 let ty = fcx.normalize_ty(span, ty);
1124 fcx.require_type_is_sized(ty, span, code);
1127 fcx.select_all_obligations_or_error();
1129 if fn_decl.is_some() {
1130 fcx.regionck_fn(id, body);
1132 fcx.regionck_expr(body);
1135 fcx.resolve_type_vars_in_body(body)
1138 // Consistency check our TypeckTables instance can hold all ItemLocalIds
1139 // it will need to hold.
1140 assert_eq!(tables.hir_owner, Some(id.owner));
1145 fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
1146 if !tcx.sess.target.target.is_abi_supported(abi) {
1151 "The ABI `{}` is not supported for the current target",
1158 struct GatherLocalsVisitor<'a, 'tcx> {
1159 fcx: &'a FnCtxt<'a, 'tcx>,
1160 parent_id: hir::HirId,
1163 impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
1164 fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
1167 // Infer the variable's type.
1168 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
1169 kind: TypeVariableOriginKind::TypeInference,
1175 .insert(nid, LocalTy { decl_ty: var_ty, revealed_ty: var_ty });
1179 // Take type that the user specified.
1180 self.fcx.locals.borrow_mut().insert(nid, typ);
1187 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
1188 type Map = intravisit::ErasedMap<'tcx>;
1190 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1191 NestedVisitorMap::None
1194 // Add explicitly-declared locals.
1195 fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) {
1196 let local_ty = match local.ty {
1198 let o_ty = self.fcx.to_ty(&ty);
1200 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
1201 self.fcx.instantiate_opaque_types_from_value(self.parent_id, &o_ty, ty.span)
1210 .canonicalize_user_type_annotation(&UserType::Ty(revealed_ty));
1212 "visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
1213 ty.hir_id, o_ty, revealed_ty, c_ty
1215 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
1217 Some(LocalTy { decl_ty: o_ty, revealed_ty })
1221 self.assign(local.span, local.hir_id, local_ty);
1224 "local variable {:?} is assigned type {}",
1226 self.fcx.ty_to_string(&*self.fcx.locals.borrow().get(&local.hir_id).unwrap().decl_ty)
1228 intravisit::walk_local(self, local);
1231 // Add pattern bindings.
1232 fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
1233 if let PatKind::Binding(_, _, ident, _) = p.kind {
1234 let var_ty = self.assign(p.span, p.hir_id, None);
1236 if !self.fcx.tcx.features().unsized_locals {
1237 self.fcx.require_type_is_sized(var_ty, p.span, traits::VariableType(p.hir_id));
1241 "pattern binding {} is assigned to {} with type {:?}",
1243 self.fcx.ty_to_string(&*self.fcx.locals.borrow().get(&p.hir_id).unwrap().decl_ty),
1247 intravisit::walk_pat(self, p);
1250 // Don't descend into the bodies of nested closures.
1253 _: intravisit::FnKind<'tcx>,
1254 _: &'tcx hir::FnDecl<'tcx>,
1262 /// When `check_fn` is invoked on a generator (i.e., a body that
1263 /// includes yield), it returns back some information about the yield
1265 struct GeneratorTypes<'tcx> {
1266 /// Type of generator argument / values returned by `yield`.
1267 resume_ty: Ty<'tcx>,
1269 /// Type of value that is yielded.
1272 /// Types that are captured (see `GeneratorInterior` for more).
1275 /// Indicates if the generator is movable or static (immovable).
1276 movability: hir::Movability,
1279 /// Helper used for fns and closures. Does the grungy work of checking a function
1280 /// body and returns the function context used for that purpose, since in the case of a fn item
1281 /// there is still a bit more to do.
1284 /// * inherited: other fields inherited from the enclosing fn (if any)
1285 fn check_fn<'a, 'tcx>(
1286 inherited: &'a Inherited<'a, 'tcx>,
1287 param_env: ty::ParamEnv<'tcx>,
1288 fn_sig: ty::FnSig<'tcx>,
1289 decl: &'tcx hir::FnDecl<'tcx>,
1291 body: &'tcx hir::Body<'tcx>,
1292 can_be_generator: Option<hir::Movability>,
1293 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
1294 let mut fn_sig = fn_sig;
1296 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1298 // Create the function context. This is either derived from scratch or,
1299 // in the case of closures, based on the outer context.
1300 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
1301 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1304 let sess = tcx.sess;
1305 let hir = tcx.hir();
1307 let declared_ret_ty = fn_sig.output();
1308 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1309 let revealed_ret_ty =
1310 fcx.instantiate_opaque_types_from_value(fn_id, &declared_ret_ty, decl.output.span());
1311 debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
1312 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1313 fn_sig = tcx.mk_fn_sig(
1314 fn_sig.inputs().iter().cloned(),
1321 let span = body.value.span;
1323 fn_maybe_err(tcx, span, fn_sig.abi);
1325 if body.generator_kind.is_some() && can_be_generator.is_some() {
1327 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
1328 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1330 // Resume type defaults to `()` if the generator has no argument.
1331 let resume_ty = fn_sig.inputs().get(0).copied().unwrap_or_else(|| tcx.mk_unit());
1333 fcx.resume_yield_tys = Some((resume_ty, yield_ty));
1336 let outer_def_id = tcx.closure_base_def_id(hir.local_def_id(fn_id));
1337 let outer_hir_id = hir.as_local_hir_id(outer_def_id).unwrap();
1338 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_hir_id }.visit_body(body);
1340 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
1341 // (as it's created inside the body itself, not passed in from outside).
1342 let maybe_va_list = if fn_sig.c_variadic {
1343 let va_list_did = tcx.require_lang_item(
1344 lang_items::VaListTypeLangItem,
1345 Some(body.params.last().unwrap().span),
1347 let region = tcx.mk_region(ty::ReScope(region::Scope {
1348 id: body.value.hir_id.local_id,
1349 data: region::ScopeData::CallSite,
1352 Some(tcx.type_of(va_list_did).subst(tcx, &[region.into()]))
1357 // Add formal parameters.
1358 let inputs_hir = hir.fn_decl_by_hir_id(fn_id).map(|decl| &decl.inputs);
1359 let inputs_fn = fn_sig.inputs().iter().copied();
1360 for (idx, (param_ty, param)) in inputs_fn.chain(maybe_va_list).zip(body.params).enumerate() {
1361 // Check the pattern.
1362 fcx.check_pat_top(¶m.pat, param_ty, try { inputs_hir?.get(idx)?.span }, false);
1364 // Check that argument is Sized.
1365 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1366 // for simple cases like `fn foo(x: Trait)`,
1367 // where we would error once on the parameter as a whole, and once on the binding `x`.
1368 if param.pat.simple_ident().is_none() && !tcx.features().unsized_locals {
1369 fcx.require_type_is_sized(param_ty, param.pat.span, traits::SizedArgumentType);
1372 fcx.write_ty(param.hir_id, param_ty);
1375 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
1377 fcx.check_return_expr(&body.value);
1379 // We insert the deferred_generator_interiors entry after visiting the body.
1380 // This ensures that all nested generators appear before the entry of this generator.
1381 // resolve_generator_interiors relies on this property.
1382 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
1384 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span });
1385 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
1387 let (resume_ty, yield_ty) = fcx.resume_yield_tys.unwrap();
1388 Some(GeneratorTypes {
1392 movability: can_be_generator.unwrap(),
1398 // Finalize the return check by taking the LUB of the return types
1399 // we saw and assigning it to the expected return type. This isn't
1400 // really expected to fail, since the coercions would have failed
1401 // earlier when trying to find a LUB.
1403 // However, the behavior around `!` is sort of complex. In the
1404 // event that the `actual_return_ty` comes back as `!`, that
1405 // indicates that the fn either does not return or "returns" only
1406 // values of type `!`. In this case, if there is an expected
1407 // return type that is *not* `!`, that should be ok. But if the
1408 // return type is being inferred, we want to "fallback" to `!`:
1410 // let x = move || panic!();
1412 // To allow for that, I am creating a type variable with diverging
1413 // fallback. This was deemed ever so slightly better than unifying
1414 // the return value with `!` because it allows for the caller to
1415 // make more assumptions about the return type (e.g., they could do
1417 // let y: Option<u32> = Some(x());
1419 // which would then cause this return type to become `u32`, not
1421 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1422 let mut actual_return_ty = coercion.complete(&fcx);
1423 if actual_return_ty.is_never() {
1424 actual_return_ty = fcx.next_diverging_ty_var(TypeVariableOrigin {
1425 kind: TypeVariableOriginKind::DivergingFn,
1429 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1431 // Check that the main return type implements the termination trait.
1432 if let Some(term_id) = tcx.lang_items().termination() {
1433 if let Some((def_id, EntryFnType::Main)) = tcx.entry_fn(LOCAL_CRATE) {
1434 let main_id = hir.as_local_hir_id(def_id).unwrap();
1435 if main_id == fn_id {
1436 let substs = tcx.mk_substs_trait(declared_ret_ty, &[]);
1437 let trait_ref = ty::TraitRef::new(term_id, substs);
1438 let return_ty_span = decl.output.span();
1439 let cause = traits::ObligationCause::new(
1442 ObligationCauseCode::MainFunctionType,
1445 inherited.register_predicate(traits::Obligation::new(
1448 trait_ref.without_const().to_predicate(),
1454 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1455 if let Some(panic_impl_did) = tcx.lang_items().panic_impl() {
1456 if panic_impl_did == hir.local_def_id(fn_id) {
1457 if let Some(panic_info_did) = tcx.lang_items().panic_info() {
1458 if declared_ret_ty.kind != ty::Never {
1459 sess.span_err(decl.output.span(), "return type should be `!`");
1462 let inputs = fn_sig.inputs();
1463 let span = hir.span(fn_id);
1464 if inputs.len() == 1 {
1465 let arg_is_panic_info = match inputs[0].kind {
1466 ty::Ref(region, ty, mutbl) => match ty.kind {
1467 ty::Adt(ref adt, _) => {
1468 adt.did == panic_info_did
1469 && mutbl == hir::Mutability::Not
1470 && *region != RegionKind::ReStatic
1477 if !arg_is_panic_info {
1478 sess.span_err(decl.inputs[0].span, "argument should be `&PanicInfo`");
1481 if let Node::Item(item) = hir.get(fn_id) {
1482 if let ItemKind::Fn(_, ref generics, _) = item.kind {
1483 if !generics.params.is_empty() {
1484 sess.span_err(span, "should have no type parameters");
1489 let span = sess.source_map().guess_head_span(span);
1490 sess.span_err(span, "function should have one argument");
1493 sess.err("language item required, but not found: `panic_info`");
1498 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1499 if let Some(alloc_error_handler_did) = tcx.lang_items().oom() {
1500 if alloc_error_handler_did == hir.local_def_id(fn_id) {
1501 if let Some(alloc_layout_did) = tcx.lang_items().alloc_layout() {
1502 if declared_ret_ty.kind != ty::Never {
1503 sess.span_err(decl.output.span(), "return type should be `!`");
1506 let inputs = fn_sig.inputs();
1507 let span = hir.span(fn_id);
1508 if inputs.len() == 1 {
1509 let arg_is_alloc_layout = match inputs[0].kind {
1510 ty::Adt(ref adt, _) => adt.did == alloc_layout_did,
1514 if !arg_is_alloc_layout {
1515 sess.span_err(decl.inputs[0].span, "argument should be `Layout`");
1518 if let Node::Item(item) = hir.get(fn_id) {
1519 if let ItemKind::Fn(_, ref generics, _) = item.kind {
1520 if !generics.params.is_empty() {
1523 "`#[alloc_error_handler]` function should have no type \
1530 let span = sess.source_map().guess_head_span(span);
1531 sess.span_err(span, "function should have one argument");
1534 sess.err("language item required, but not found: `alloc_layout`");
1542 fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1543 let def_id = tcx.hir().local_def_id(id);
1544 let def = tcx.adt_def(def_id);
1545 def.destructor(tcx); // force the destructor to be evaluated
1546 check_representable(tcx, span, def_id);
1548 if def.repr.simd() {
1549 check_simd(tcx, span, def_id);
1552 check_transparent(tcx, span, def_id);
1553 check_packed(tcx, span, def_id);
1556 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
1557 let def_id = tcx.hir().local_def_id(id);
1558 let def = tcx.adt_def(def_id);
1559 def.destructor(tcx); // force the destructor to be evaluated
1560 check_representable(tcx, span, def_id);
1561 check_transparent(tcx, span, def_id);
1562 check_union_fields(tcx, span, def_id);
1563 check_packed(tcx, span, def_id);
1566 /// When the `#![feature(untagged_unions)]` gate is active,
1567 /// check that the fields of the `union` does not contain fields that need dropping.
1568 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: DefId) -> bool {
1569 let item_type = tcx.type_of(item_def_id);
1570 if let ty::Adt(def, substs) = item_type.kind {
1571 assert!(def.is_union());
1572 let fields = &def.non_enum_variant().fields;
1573 let param_env = tcx.param_env(item_def_id);
1574 for field in fields {
1575 let field_ty = field.ty(tcx, substs);
1576 // We are currently checking the type this field came from, so it must be local.
1577 let field_span = tcx.hir().span_if_local(field.did).unwrap();
1578 if field_ty.needs_drop(tcx, param_env) {
1583 "unions may not contain fields that need dropping"
1585 .span_note(field_span, "`std::mem::ManuallyDrop` can be used to wrap the type")
1591 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind);
1596 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
1597 /// projections that would result in "inheriting lifetimes".
1598 fn check_opaque<'tcx>(
1601 substs: SubstsRef<'tcx>,
1603 origin: &hir::OpaqueTyOrigin,
1605 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
1606 check_opaque_for_cycles(tcx, def_id, substs, span, origin);
1609 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
1610 /// in "inheriting lifetimes".
1611 fn check_opaque_for_inheriting_lifetimes(tcx: TyCtxt<'tcx>, def_id: DefId, span: Span) {
1613 tcx.hir().expect_item(tcx.hir().as_local_hir_id(def_id).expect("opaque type is not local"));
1615 "check_opaque_for_inheriting_lifetimes: def_id={:?} span={:?} item={:?}",
1620 struct ProhibitOpaqueVisitor<'tcx> {
1621 opaque_identity_ty: Ty<'tcx>,
1622 generics: &'tcx ty::Generics,
1625 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
1626 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
1627 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
1628 if t == self.opaque_identity_ty { false } else { t.super_visit_with(self) }
1631 fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
1632 debug!("check_opaque_for_inheriting_lifetimes: (visit_region) r={:?}", r);
1633 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
1634 return *index < self.generics.parent_count as u32;
1637 r.super_visit_with(self)
1641 let prohibit_opaque = match item.kind {
1642 ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn, .. })
1643 | ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::FnReturn, .. }) => {
1644 let mut visitor = ProhibitOpaqueVisitor {
1645 opaque_identity_ty: tcx
1646 .mk_opaque(def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1647 generics: tcx.generics_of(def_id),
1649 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1651 tcx.predicates_of(def_id)
1654 .any(|(predicate, _)| predicate.visit_with(&mut visitor))
1659 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1660 if prohibit_opaque {
1661 let is_async = match item.kind {
1662 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1663 hir::OpaqueTyOrigin::AsyncFn => true,
1666 _ => unreachable!(),
1672 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1674 if is_async { "async fn" } else { "impl Trait" },
1680 /// Checks that an opaque type does not contain cycles.
1681 fn check_opaque_for_cycles<'tcx>(
1684 substs: SubstsRef<'tcx>,
1686 origin: &hir::OpaqueTyOrigin,
1688 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1689 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1690 struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing",)
1691 .span_label(span, "recursive `async fn`")
1692 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
1696 struct_span_err!(tcx.sess, span, E0720, "opaque type expands to a recursive type",);
1697 err.span_label(span, "expands to a recursive type");
1698 if let ty::Opaque(..) = partially_expanded_type.kind {
1699 err.note("type resolves to itself");
1701 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1708 // Forbid defining intrinsics in Rust code,
1709 // as they must always be defined by the compiler.
1710 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1711 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1712 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1716 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item<'tcx>) {
1718 "check_item_type(it.hir_id={}, it.name={})",
1720 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1722 let _indenter = indenter();
1724 // Consts can play a role in type-checking, so they are included here.
1725 hir::ItemKind::Static(..) => {
1726 let def_id = tcx.hir().local_def_id(it.hir_id);
1727 tcx.typeck_tables_of(def_id);
1728 maybe_check_static_with_link_section(tcx, def_id, it.span);
1730 hir::ItemKind::Const(..) => {
1731 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1733 hir::ItemKind::Enum(ref enum_definition, _) => {
1734 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1736 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1737 hir::ItemKind::Impl { ref items, .. } => {
1738 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1739 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1740 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1741 check_impl_items_against_trait(tcx, it.span, impl_def_id, impl_trait_ref, items);
1742 let trait_def_id = impl_trait_ref.def_id;
1743 check_on_unimplemented(tcx, trait_def_id, it);
1746 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1747 let def_id = tcx.hir().local_def_id(it.hir_id);
1748 check_on_unimplemented(tcx, def_id, it);
1750 for item in items.iter() {
1751 let item = tcx.hir().trait_item(item.id);
1752 if let hir::TraitItemKind::Fn(sig, _) = &item.kind {
1753 let abi = sig.header.abi;
1754 fn_maybe_err(tcx, item.ident.span, abi);
1758 hir::ItemKind::Struct(..) => {
1759 check_struct(tcx, it.hir_id, it.span);
1761 hir::ItemKind::Union(..) => {
1762 check_union(tcx, it.hir_id, it.span);
1764 hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
1765 let def_id = tcx.hir().local_def_id(it.hir_id);
1767 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1768 check_opaque(tcx, def_id, substs, it.span, &origin);
1770 hir::ItemKind::TyAlias(..) => {
1771 let def_id = tcx.hir().local_def_id(it.hir_id);
1772 let pty_ty = tcx.type_of(def_id);
1773 let generics = tcx.generics_of(def_id);
1774 check_type_params_are_used(tcx, &generics, pty_ty);
1776 hir::ItemKind::ForeignMod(ref m) => {
1777 check_abi(tcx, it.span, m.abi);
1779 if m.abi == Abi::RustIntrinsic {
1780 for item in m.items {
1781 intrinsic::check_intrinsic_type(tcx, item);
1783 } else if m.abi == Abi::PlatformIntrinsic {
1784 for item in m.items {
1785 intrinsic::check_platform_intrinsic_type(tcx, item);
1788 for item in m.items {
1789 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1790 let own_counts = generics.own_counts();
1791 if generics.params.len() - own_counts.lifetimes != 0 {
1792 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1793 (_, 0) => ("type", "types", Some("u32")),
1794 // We don't specify an example value, because we can't generate
1795 // a valid value for any type.
1796 (0, _) => ("const", "consts", None),
1797 _ => ("type or const", "types or consts", None),
1803 "foreign items may not have {} parameters",
1806 .span_label(item.span, &format!("can't have {} parameters", kinds))
1808 // FIXME: once we start storing spans for type arguments, turn this
1809 // into a suggestion.
1811 "replace the {} parameters with concrete {}{}",
1814 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1820 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.kind {
1821 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1826 _ => { /* nothing to do */ }
1830 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1831 // Only restricted on wasm32 target for now
1832 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1836 // If `#[link_section]` is missing, then nothing to verify
1837 let attrs = tcx.codegen_fn_attrs(id);
1838 if attrs.link_section.is_none() {
1842 // For the wasm32 target statics with `#[link_section]` are placed into custom
1843 // sections of the final output file, but this isn't link custom sections of
1844 // other executable formats. Namely we can only embed a list of bytes,
1845 // nothing with pointers to anything else or relocations. If any relocation
1846 // show up, reject them here.
1847 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1848 // the consumer's responsibility to ensure all bytes that have been read
1849 // have defined values.
1850 match tcx.const_eval_poly(id) {
1851 Ok(ConstValue::ByRef { alloc, .. }) => {
1852 if alloc.relocations().len() != 0 {
1853 let msg = "statics with a custom `#[link_section]` must be a \
1854 simple list of bytes on the wasm target with no \
1855 extra levels of indirection such as references";
1856 tcx.sess.span_err(span, msg);
1859 Ok(_) => bug!("Matching on non-ByRef static"),
1864 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item<'_>) {
1865 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1866 // an error would be reported if this fails.
1867 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1870 fn report_forbidden_specialization(
1872 impl_item: &hir::ImplItem<'_>,
1875 let mut err = struct_span_err!(
1879 "`{}` specializes an item from a parent `impl`, but \
1880 that item is not marked `default`",
1883 err.span_label(impl_item.span, format!("cannot specialize default item `{}`", impl_item.ident));
1885 match tcx.span_of_impl(parent_impl) {
1887 err.span_label(span, "parent `impl` is here");
1889 "to specialize, `{}` in the parent `impl` must be marked `default`",
1894 err.note(&format!("parent implementation is in crate `{}`", cname));
1901 fn check_specialization_validity<'tcx>(
1903 trait_def: &ty::TraitDef,
1904 trait_item: &ty::AssocItem,
1906 impl_item: &hir::ImplItem<'_>,
1908 let kind = match impl_item.kind {
1909 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1910 hir::ImplItemKind::Fn(..) => ty::AssocKind::Fn,
1911 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1912 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1915 let ancestors = match trait_def.ancestors(tcx, impl_id) {
1916 Ok(ancestors) => ancestors,
1919 let mut ancestor_impls = ancestors
1921 .filter_map(|parent| {
1922 if parent.is_from_trait() {
1925 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
1930 if ancestor_impls.peek().is_none() {
1931 // No parent, nothing to specialize.
1935 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
1937 // Parent impl exists, and contains the parent item we're trying to specialize, but
1938 // doesn't mark it `default`.
1939 Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
1940 Some(Err(parent_impl.def_id()))
1943 // Parent impl contains item and makes it specializable.
1944 Some(_) => Some(Ok(())),
1946 // Parent impl doesn't mention the item. This means it's inherited from the
1947 // grandparent. In that case, if parent is a `default impl`, inherited items use the
1948 // "defaultness" from the grandparent, else they are final.
1950 if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
1953 Some(Err(parent_impl.def_id()))
1959 // If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the
1960 // item. This is allowed, the item isn't actually getting specialized here.
1961 let result = opt_result.unwrap_or(Ok(()));
1963 if let Err(parent_impl) = result {
1964 report_forbidden_specialization(tcx, impl_item, parent_impl);
1968 fn check_impl_items_against_trait<'tcx>(
1970 full_impl_span: Span,
1972 impl_trait_ref: ty::TraitRef<'tcx>,
1973 impl_item_refs: &[hir::ImplItemRef<'_>],
1975 let impl_span = tcx.sess.source_map().guess_head_span(full_impl_span);
1977 // If the trait reference itself is erroneous (so the compilation is going
1978 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1979 // isn't populated for such impls.
1980 if impl_trait_ref.references_error() {
1984 // Negative impls are not expected to have any items
1985 match tcx.impl_polarity(impl_id) {
1986 ty::ImplPolarity::Reservation | ty::ImplPolarity::Positive => {}
1987 ty::ImplPolarity::Negative => {
1988 if let [first_item_ref, ..] = impl_item_refs {
1989 let first_item_span = tcx.hir().impl_item(first_item_ref.id).span;
1994 "negative impls cannot have any items"
2002 // Locate trait definition and items
2003 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
2005 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
2007 // Check existing impl methods to see if they are both present in trait
2008 // and compatible with trait signature
2009 for impl_item in impl_items() {
2010 let namespace = impl_item.kind.namespace();
2011 let ty_impl_item = tcx.associated_item(tcx.hir().local_def_id(impl_item.hir_id));
2012 let ty_trait_item = tcx
2013 .associated_items(impl_trait_ref.def_id)
2014 .find_by_name_and_namespace(tcx, ty_impl_item.ident, namespace, impl_trait_ref.def_id)
2016 // Not compatible, but needed for the error message
2017 tcx.associated_items(impl_trait_ref.def_id)
2018 .filter_by_name(tcx, ty_impl_item.ident, impl_trait_ref.def_id)
2022 // Check that impl definition matches trait definition
2023 if let Some(ty_trait_item) = ty_trait_item {
2024 match impl_item.kind {
2025 hir::ImplItemKind::Const(..) => {
2026 // Find associated const definition.
2027 if ty_trait_item.kind == ty::AssocKind::Const {
2036 let mut err = struct_span_err!(
2040 "item `{}` is an associated const, \
2041 which doesn't match its trait `{}`",
2043 impl_trait_ref.print_only_trait_path()
2045 err.span_label(impl_item.span, "does not match trait");
2046 // We can only get the spans from local trait definition
2047 // Same for E0324 and E0325
2048 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
2049 err.span_label(trait_span, "item in trait");
2054 hir::ImplItemKind::Fn(..) => {
2055 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
2056 if ty_trait_item.kind == ty::AssocKind::Fn {
2057 compare_impl_method(
2066 let mut err = struct_span_err!(
2070 "item `{}` is an associated method, \
2071 which doesn't match its trait `{}`",
2073 impl_trait_ref.print_only_trait_path()
2075 err.span_label(impl_item.span, "does not match trait");
2076 if let Some(trait_span) = opt_trait_span {
2077 err.span_label(trait_span, "item in trait");
2082 hir::ImplItemKind::OpaqueTy(..) | hir::ImplItemKind::TyAlias(_) => {
2083 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
2084 if ty_trait_item.kind == ty::AssocKind::Type {
2094 let mut err = struct_span_err!(
2098 "item `{}` is an associated type, \
2099 which doesn't match its trait `{}`",
2101 impl_trait_ref.print_only_trait_path()
2103 err.span_label(impl_item.span, "does not match trait");
2104 if let Some(trait_span) = opt_trait_span {
2105 err.span_label(trait_span, "item in trait");
2112 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
2116 // Check for missing items from trait
2117 let mut missing_items = Vec::new();
2118 if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id) {
2119 for trait_item in tcx.associated_items(impl_trait_ref.def_id).in_definition_order() {
2120 let is_implemented = ancestors
2121 .leaf_def(tcx, trait_item.ident, trait_item.kind)
2122 .map(|node_item| !node_item.defining_node.is_from_trait())
2125 if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
2126 if !trait_item.defaultness.has_value() {
2127 missing_items.push(*trait_item);
2133 if !missing_items.is_empty() {
2134 missing_items_err(tcx, impl_span, &missing_items, full_impl_span);
2138 fn missing_items_err(
2141 missing_items: &[ty::AssocItem],
2142 full_impl_span: Span,
2144 let missing_items_msg = missing_items
2146 .map(|trait_item| trait_item.ident.to_string())
2147 .collect::<Vec<_>>()
2150 let mut err = struct_span_err!(
2154 "not all trait items implemented, missing: `{}`",
2157 err.span_label(impl_span, format!("missing `{}` in implementation", missing_items_msg));
2159 // `Span` before impl block closing brace.
2160 let hi = full_impl_span.hi() - BytePos(1);
2161 // Point at the place right before the closing brace of the relevant `impl` to suggest
2162 // adding the associated item at the end of its body.
2163 let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi);
2164 // Obtain the level of indentation ending in `sugg_sp`.
2165 let indentation = tcx.sess.source_map().span_to_margin(sugg_sp).unwrap_or(0);
2166 // Make the whitespace that will make the suggestion have the right indentation.
2167 let padding: String = (0..indentation).map(|_| " ").collect();
2169 for trait_item in missing_items {
2170 let snippet = suggestion_signature(&trait_item, tcx);
2171 let code = format!("{}{}\n{}", padding, snippet, padding);
2172 let msg = format!("implement the missing item: `{}`", snippet);
2173 let appl = Applicability::HasPlaceholders;
2174 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
2175 err.span_label(span, format!("`{}` from trait", trait_item.ident));
2176 err.tool_only_span_suggestion(sugg_sp, &msg, code, appl);
2178 err.span_suggestion_hidden(sugg_sp, &msg, code, appl);
2184 /// Resugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions.
2185 fn bounds_from_generic_predicates(
2187 predicates: ty::GenericPredicates<'_>,
2188 ) -> (String, String) {
2189 let mut types: FxHashMap<Ty<'_>, Vec<DefId>> = FxHashMap::default();
2190 let mut projections = vec![];
2191 for (predicate, _) in predicates.predicates {
2192 debug!("predicate {:?}", predicate);
2194 ty::Predicate::Trait(trait_predicate, _) => {
2195 let entry = types.entry(trait_predicate.skip_binder().self_ty()).or_default();
2196 let def_id = trait_predicate.skip_binder().def_id();
2197 if Some(def_id) != tcx.lang_items().sized_trait() {
2198 // Type params are `Sized` by default, do not add that restriction to the list
2199 // if it is a positive requirement.
2200 entry.push(trait_predicate.skip_binder().def_id());
2203 ty::Predicate::Projection(projection_pred) => {
2204 projections.push(projection_pred);
2209 let generics = if types.is_empty() {
2216 .filter_map(|t| match t.kind {
2217 ty::Param(_) => Some(t.to_string()),
2218 // Avoid suggesting the following:
2219 // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {}
2222 .collect::<Vec<_>>()
2226 let mut where_clauses = vec![];
2227 for (ty, bounds) in types {
2228 for bound in &bounds {
2229 where_clauses.push(format!("{}: {}", ty, tcx.def_path_str(*bound)));
2232 for projection in &projections {
2233 let p = projection.skip_binder();
2234 // FIXME: this is not currently supported syntax, we should be looking at the `types` and
2235 // insert the associated types where they correspond, but for now let's be "lazy" and
2236 // propose this instead of the following valid resugaring:
2237 // `T: Trait, Trait::Assoc = K` → `T: Trait<Assoc = K>`
2238 where_clauses.push(format!("{} = {}", tcx.def_path_str(p.projection_ty.item_def_id), p.ty));
2240 let where_clauses = if where_clauses.is_empty() {
2243 format!(" where {}", where_clauses.join(", "))
2245 (generics, where_clauses)
2248 /// Return placeholder code for the given function.
2249 fn fn_sig_suggestion(
2251 sig: &ty::FnSig<'_>,
2253 predicates: ty::GenericPredicates<'_>,
2259 Some(match ty.kind {
2260 ty::Param(param) if param.name == kw::SelfUpper => "self".to_string(),
2261 ty::Ref(reg, ref_ty, mutability) => {
2262 let reg = match &format!("{}", reg)[..] {
2263 "'_" | "" => String::new(),
2264 reg => format!("{} ", reg),
2267 ty::Param(param) if param.name == kw::SelfUpper => {
2268 format!("&{}{}self", reg, mutability.prefix_str())
2270 _ => format!("_: {:?}", ty),
2273 _ => format!("_: {:?}", ty),
2276 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
2277 .filter_map(|arg| arg)
2278 .collect::<Vec<String>>()
2280 let output = sig.output();
2281 let output = if !output.is_unit() { format!(" -> {:?}", output) } else { String::new() };
2283 let unsafety = sig.unsafety.prefix_str();
2284 let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
2286 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
2287 // not be present in the `fn` definition, not will we account for renamed
2288 // lifetimes between the `impl` and the `trait`, but this should be good enough to
2289 // fill in a significant portion of the missing code, and other subsequent
2290 // suggestions can help the user fix the code.
2292 "{}fn {}{}({}){}{} {{ todo!() }}",
2293 unsafety, ident, generics, args, output, where_clauses
2297 /// Return placeholder code for the given associated item.
2298 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
2299 /// structured suggestion.
2300 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
2302 ty::AssocKind::Fn => {
2303 // We skip the binder here because the binder would deanonymize all
2304 // late-bound regions, and we don't want method signatures to show up
2305 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
2306 // regions just fine, showing `fn(&MyType)`.
2309 tcx.fn_sig(assoc.def_id).skip_binder(),
2311 tcx.predicates_of(assoc.def_id),
2314 ty::AssocKind::Type => format!("type {} = Type;", assoc.ident),
2315 // FIXME(type_alias_impl_trait): we should print bounds here too.
2316 ty::AssocKind::OpaqueTy => format!("type {} = Type;", assoc.ident),
2317 ty::AssocKind::Const => {
2318 let ty = tcx.type_of(assoc.def_id);
2319 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
2320 format!("const {}: {:?} = {};", assoc.ident, ty, val)
2325 /// Checks whether a type can be represented in memory. In particular, it
2326 /// identifies types that contain themselves without indirection through a
2327 /// pointer, which would mean their size is unbounded.
2328 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
2329 let rty = tcx.type_of(item_def_id);
2331 // Check that it is possible to represent this type. This call identifies
2332 // (1) types that contain themselves and (2) types that contain a different
2333 // recursive type. It is only necessary to throw an error on those that
2334 // contain themselves. For case 2, there must be an inner type that will be
2335 // caught by case 1.
2336 match rty.is_representable(tcx, sp) {
2337 Representability::SelfRecursive(spans) => {
2338 let mut err = recursive_type_with_infinite_size_error(tcx, item_def_id);
2340 err.span_label(span, "recursive without indirection");
2345 Representability::Representable | Representability::ContainsRecursive => (),
2350 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2351 let t = tcx.type_of(def_id);
2352 if let ty::Adt(def, substs) = t.kind {
2353 if def.is_struct() {
2354 let fields = &def.non_enum_variant().fields;
2355 if fields.is_empty() {
2356 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
2359 let e = fields[0].ty(tcx, substs);
2360 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
2361 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
2362 .span_label(sp, "SIMD elements must have the same type")
2367 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
2368 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
2374 "SIMD vector element type should be machine type"
2384 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2385 let repr = tcx.adt_def(def_id).repr;
2387 for attr in tcx.get_attrs(def_id).iter() {
2388 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
2389 if let attr::ReprPacked(pack) = r {
2390 if let Some(repr_pack) = repr.pack {
2391 if pack as u64 != repr_pack.bytes() {
2396 "type has conflicting packed representation hints"
2404 if repr.align.is_some() {
2409 "type has conflicting packed and align representation hints"
2413 if let Some(def_spans) = check_packed_inner(tcx, def_id, &mut vec![]) {
2414 let mut err = struct_span_err!(
2418 "packed type cannot transitively contain a `#[repr(align)]` type"
2421 let hir = tcx.hir();
2422 if let Some(hir_id) = hir.as_local_hir_id(def_spans[0].0) {
2423 if let Node::Item(Item { ident, .. }) = hir.get(hir_id) {
2425 tcx.def_span(def_spans[0].0),
2426 &format!("`{}` has a `#[repr(align)]` attribute", ident),
2431 if def_spans.len() > 2 {
2432 let mut first = true;
2433 for (adt_def, span) in def_spans.iter().skip(1).rev() {
2434 if let Some(hir_id) = hir.as_local_hir_id(*adt_def) {
2435 if let Node::Item(Item { ident, .. }) = hir.get(hir_id) {
2440 "`{}` contains a field of type `{}`",
2441 tcx.type_of(def_id),
2445 format!("...which contains a field of type `{}`", ident)
2460 fn check_packed_inner(
2463 stack: &mut Vec<DefId>,
2464 ) -> Option<Vec<(DefId, Span)>> {
2465 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind {
2466 if def.is_struct() || def.is_union() {
2467 if def.repr.align.is_some() {
2468 return Some(vec![(def.did, DUMMY_SP)]);
2472 for field in &def.non_enum_variant().fields {
2473 if let ty::Adt(def, _) = field.ty(tcx, substs).kind {
2474 if !stack.contains(&def.did) {
2475 if let Some(mut defs) = check_packed_inner(tcx, def.did, stack) {
2476 defs.push((def.did, field.ident.span));
2489 /// Emit an error when encountering more or less than one variant in a transparent enum.
2490 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2491 let variant_spans: Vec<_> = adt
2494 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
2496 let msg = format!("needs exactly one variant, but has {}", adt.variants.len(),);
2497 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2498 err.span_label(sp, &msg);
2499 if let [start @ .., end] = &*variant_spans {
2500 for variant_span in start {
2501 err.span_label(*variant_span, "");
2503 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2508 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2510 fn bad_non_zero_sized_fields<'tcx>(
2512 adt: &'tcx ty::AdtDef,
2514 field_spans: impl Iterator<Item = Span>,
2517 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2518 let mut err = struct_span_err!(
2522 "{}transparent {} {}",
2523 if adt.is_enum() { "the variant of a " } else { "" },
2527 err.span_label(sp, &msg);
2528 for sp in field_spans {
2529 err.span_label(sp, "this field is non-zero-sized");
2534 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2535 let adt = tcx.adt_def(def_id);
2536 if !adt.repr.transparent() {
2539 let sp = tcx.sess.source_map().guess_head_span(sp);
2541 if adt.is_union() && !tcx.features().transparent_unions {
2543 &tcx.sess.parse_sess,
2544 sym::transparent_unions,
2546 "transparent unions are unstable",
2551 if adt.variants.len() != 1 {
2552 bad_variant_count(tcx, adt, sp, def_id);
2553 if adt.variants.is_empty() {
2554 // Don't bother checking the fields. No variants (and thus no fields) exist.
2559 // For each field, figure out if it's known to be a ZST and align(1)
2560 let field_infos = adt.all_fields().map(|field| {
2561 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2562 let param_env = tcx.param_env(field.did);
2563 let layout = tcx.layout_of(param_env.and(ty));
2564 // We are currently checking the type this field came from, so it must be local
2565 let span = tcx.hir().span_if_local(field.did).unwrap();
2566 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2567 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2571 let non_zst_fields =
2572 field_infos.clone().filter_map(|(span, zst, _align1)| if !zst { Some(span) } else { None });
2573 let non_zst_count = non_zst_fields.clone().count();
2574 if non_zst_count != 1 {
2575 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2577 for (span, zst, align1) in field_infos {
2583 "zero-sized field in transparent {} has alignment larger than 1",
2586 .span_label(span, "has alignment larger than 1")
2592 #[allow(trivial_numeric_casts)]
2593 pub fn check_enum<'tcx>(
2596 vs: &'tcx [hir::Variant<'tcx>],
2599 let def_id = tcx.hir().local_def_id(id);
2600 let def = tcx.adt_def(def_id);
2601 def.destructor(tcx); // force the destructor to be evaluated
2604 let attributes = tcx.get_attrs(def_id);
2605 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2610 "unsupported representation for zero-variant enum"
2612 .span_label(sp, "zero-variant enum")
2617 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2618 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2619 if !tcx.features().repr128 {
2621 &tcx.sess.parse_sess,
2624 "repr with 128-bit type is unstable",
2631 if let Some(ref e) = v.disr_expr {
2632 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2636 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2637 let is_unit = |var: &hir::Variant<'_>| match var.data {
2638 hir::VariantData::Unit(..) => true,
2642 let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();
2643 let has_non_units = vs.iter().any(|var| !is_unit(var));
2644 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2645 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2647 if disr_non_unit || (disr_units && has_non_units) {
2649 struct_span_err!(tcx.sess, sp, E0732, "`#[repr(inttype)]` must be specified");
2654 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2655 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2656 // Check for duplicate discriminant values
2657 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2658 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2659 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2660 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2661 let i_span = match variant_i.disr_expr {
2662 Some(ref expr) => tcx.hir().span(expr.hir_id),
2663 None => tcx.hir().span(variant_i_hir_id),
2665 let span = match v.disr_expr {
2666 Some(ref expr) => tcx.hir().span(expr.hir_id),
2673 "discriminant value `{}` already exists",
2676 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2677 .span_label(span, format!("enum already has `{}`", disr_vals[i]))
2680 disr_vals.push(discr);
2683 check_representable(tcx, sp, def_id);
2684 check_transparent(tcx, sp, def_id);
2687 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span) {
2692 "expected unit struct, unit variant or constant, found {}{}",
2694 tcx.sess.source_map().span_to_snippet(span).map_or(String::new(), |s| format!(" `{}`", s)),
2699 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2700 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2704 fn item_def_id(&self) -> Option<DefId> {
2708 fn default_constness_for_trait_bounds(&self) -> hir::Constness {
2709 // FIXME: refactor this into a method
2710 let node = self.tcx.hir().get(self.body_id);
2711 if let Some(fn_like) = FnLikeNode::from_node(node) {
2714 hir::Constness::NotConst
2718 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2720 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2721 let item_id = tcx.hir().ty_param_owner(hir_id);
2722 let item_def_id = tcx.hir().local_def_id(item_id);
2723 let generics = tcx.generics_of(item_def_id);
2724 let index = generics.param_def_id_to_index[&def_id];
2725 ty::GenericPredicates {
2727 predicates: tcx.arena.alloc_from_iter(self.param_env.caller_bounds.iter().filter_map(
2728 |&predicate| match predicate {
2729 ty::Predicate::Trait(ref data, _)
2730 if data.skip_binder().self_ty().is_param(index) =>
2732 // HACK(eddyb) should get the original `Span`.
2733 let span = tcx.def_span(def_id);
2734 Some((predicate, span))
2742 fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
2744 Some(def) => infer::EarlyBoundRegion(span, def.name),
2745 None => infer::MiscVariable(span),
2747 Some(self.next_region_var(v))
2750 fn allow_ty_infer(&self) -> bool {
2754 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2755 if let Some(param) = param {
2756 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2761 self.next_ty_var(TypeVariableOrigin {
2762 kind: TypeVariableOriginKind::TypeInference,
2771 param: Option<&ty::GenericParamDef>,
2773 ) -> &'tcx Const<'tcx> {
2774 if let Some(param) = param {
2775 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2780 self.next_const_var(
2782 ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
2787 fn projected_ty_from_poly_trait_ref(
2791 item_segment: &hir::PathSegment<'_>,
2792 poly_trait_ref: ty::PolyTraitRef<'tcx>,
2794 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2796 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2800 let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
2809 self.tcx().mk_projection(item_def_id, item_substs)
2812 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2813 if ty.has_escaping_bound_vars() {
2814 ty // FIXME: normalization and escaping regions
2816 self.normalize_associated_types_in(span, &ty)
2820 fn set_tainted_by_errors(&self) {
2821 self.infcx.set_tainted_by_errors()
2824 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2825 self.write_ty(hir_id, ty)
2829 /// Controls whether the arguments are tupled. This is used for the call
2832 /// Tupling means that all call-side arguments are packed into a tuple and
2833 /// passed as a single parameter. For example, if tupling is enabled, this
2836 /// fn f(x: (isize, isize))
2838 /// Can be called as:
2845 #[derive(Clone, Eq, PartialEq)]
2846 enum TupleArgumentsFlag {
2851 /// Controls how we perform fallback for unconstrained
2854 /// Do not fallback type variables to opaque types.
2856 /// Perform all possible kinds of fallback, including
2857 /// turning type variables to opaque types.
2861 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2863 inh: &'a Inherited<'a, 'tcx>,
2864 param_env: ty::ParamEnv<'tcx>,
2865 body_id: hir::HirId,
2866 ) -> FnCtxt<'a, 'tcx> {
2870 err_count_on_creation: inh.tcx.sess.err_count(),
2872 ret_coercion_span: RefCell::new(None),
2873 resume_yield_tys: None,
2874 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
2875 diverges: Cell::new(Diverges::Maybe),
2876 has_errors: Cell::new(false),
2877 enclosing_breakables: RefCell::new(EnclosingBreakables {
2879 by_id: Default::default(),
2885 pub fn sess(&self) -> &Session {
2889 pub fn errors_reported_since_creation(&self) -> bool {
2890 self.tcx.sess.err_count() > self.err_count_on_creation
2893 /// Produces warning on the given node, if the current point in the
2894 /// function is unreachable, and there hasn't been another warning.
2895 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2896 // FIXME: Combine these two 'if' expressions into one once
2897 // let chains are implemented
2898 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2899 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2900 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2901 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2902 if !span.is_desugaring(DesugaringKind::CondTemporary)
2903 && !span.is_desugaring(DesugaringKind::Async)
2904 && !orig_span.is_desugaring(DesugaringKind::Await)
2906 self.diverges.set(Diverges::WarnedAlways);
2908 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2910 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, |lint| {
2911 let msg = format!("unreachable {}", kind);
2913 .span_label(span, &msg)
2917 .unwrap_or("any code following this expression is unreachable"),
2925 pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
2926 ObligationCause::new(span, self.body_id, code)
2929 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2930 self.cause(span, ObligationCauseCode::MiscObligation)
2933 /// Resolves type and const variables in `ty` if possible. Unlike the infcx
2934 /// version (resolve_vars_if_possible), this version will
2935 /// also select obligations if it seems useful, in an effort
2936 /// to get more type information.
2937 fn resolve_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2938 debug!("resolve_vars_with_obligations(ty={:?})", ty);
2940 // No Infer()? Nothing needs doing.
2941 if !ty.has_infer_types_or_consts() {
2942 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2946 // If `ty` is a type variable, see whether we already know what it is.
2947 ty = self.resolve_vars_if_possible(&ty);
2948 if !ty.has_infer_types_or_consts() {
2949 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2953 // If not, try resolving pending obligations as much as
2954 // possible. This can help substantially when there are
2955 // indirect dependencies that don't seem worth tracking
2957 self.select_obligations_where_possible(false, |_| {});
2958 ty = self.resolve_vars_if_possible(&ty);
2960 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2964 fn record_deferred_call_resolution(
2966 closure_def_id: DefId,
2967 r: DeferredCallResolution<'tcx>,
2969 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2970 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2973 fn remove_deferred_call_resolutions(
2975 closure_def_id: DefId,
2976 ) -> Vec<DeferredCallResolution<'tcx>> {
2977 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2978 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2981 pub fn tag(&self) -> String {
2982 format!("{:p}", self)
2985 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2986 self.locals.borrow().get(&nid).cloned().unwrap_or_else(|| {
2987 span_bug!(span, "no type for local variable {}", self.tcx.hir().node_to_string(nid))
2992 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2994 "write_ty({:?}, {:?}) in fcx {}",
2996 self.resolve_vars_if_possible(&ty),
2999 self.tables.borrow_mut().node_types_mut().insert(id, ty);
3001 if ty.references_error() {
3002 self.has_errors.set(true);
3003 self.set_tainted_by_errors();
3007 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
3008 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
3011 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
3012 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
3015 pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
3016 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
3017 self.write_resolution(hir_id, Ok((DefKind::AssocFn, method.def_id)));
3018 self.write_substs(hir_id, method.substs);
3020 // When the method is confirmed, the `method.substs` includes
3021 // parameters from not just the method, but also the impl of
3022 // the method -- in particular, the `Self` type will be fully
3023 // resolved. However, those are not something that the "user
3024 // specified" -- i.e., those types come from the inferred type
3025 // of the receiver, not something the user wrote. So when we
3026 // create the user-substs, we want to replace those earlier
3027 // types with just the types that the user actually wrote --
3028 // that is, those that appear on the *method itself*.
3030 // As an example, if the user wrote something like
3031 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
3032 // type of `foo` (possibly adjusted), but we don't want to
3033 // include that. We want just the `[_, u32]` part.
3034 if !method.substs.is_noop() {
3035 let method_generics = self.tcx.generics_of(method.def_id);
3036 if !method_generics.params.is_empty() {
3037 let user_type_annotation = self.infcx.probe(|_| {
3038 let user_substs = UserSubsts {
3039 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
3040 let i = param.index as usize;
3041 if i < method_generics.parent_count {
3042 self.infcx.var_for_def(DUMMY_SP, param)
3047 user_self_ty: None, // not relevant here
3050 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
3056 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
3057 self.write_user_type_annotation(hir_id, user_type_annotation);
3062 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
3063 if !substs.is_noop() {
3064 debug!("write_substs({:?}, {:?}) in fcx {}", node_id, substs, self.tag());
3066 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
3070 /// Given the substs that we just converted from the HIR, try to
3071 /// canonicalize them and store them as user-given substitutions
3072 /// (i.e., substitutions that must be respected by the NLL check).
3074 /// This should be invoked **before any unifications have
3075 /// occurred**, so that annotations like `Vec<_>` are preserved
3077 pub fn write_user_type_annotation_from_substs(
3081 substs: SubstsRef<'tcx>,
3082 user_self_ty: Option<UserSelfTy<'tcx>>,
3085 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
3086 user_self_ty={:?} in fcx {}",
3094 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
3095 let canonicalized = self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
3097 UserSubsts { substs, user_self_ty },
3099 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
3100 self.write_user_type_annotation(hir_id, canonicalized);
3104 pub fn write_user_type_annotation(
3107 canonical_user_type_annotation: CanonicalUserType<'tcx>,
3110 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
3112 canonical_user_type_annotation,
3116 if !canonical_user_type_annotation.is_identity() {
3119 .user_provided_types_mut()
3120 .insert(hir_id, canonical_user_type_annotation);
3122 debug!("write_user_type_annotation: skipping identity substs");
3126 pub fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment<'tcx>>) {
3127 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
3133 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
3134 Entry::Vacant(entry) => {
3137 Entry::Occupied(mut entry) => {
3138 debug!(" - composing on top of {:?}", entry.get());
3139 match (&entry.get()[..], &adj[..]) {
3140 // Applying any adjustment on top of a NeverToAny
3141 // is a valid NeverToAny adjustment, because it can't
3143 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
3145 Adjustment { kind: Adjust::Deref(_), .. },
3146 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
3148 Adjustment { kind: Adjust::Deref(_), .. },
3149 .. // Any following adjustments are allowed.
3151 // A reborrow has no effect before a dereference.
3153 // FIXME: currently we never try to compose autoderefs
3154 // and ReifyFnPointer/UnsafeFnPointer, but we could.
3156 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
3157 expr, entry.get(), adj)
3159 *entry.get_mut() = adj;
3164 /// Basically whenever we are converting from a type scheme into
3165 /// the fn body space, we always want to normalize associated
3166 /// types as well. This function combines the two.
3167 fn instantiate_type_scheme<T>(&self, span: Span, substs: SubstsRef<'tcx>, value: &T) -> T
3169 T: TypeFoldable<'tcx>,
3171 let value = value.subst(self.tcx, substs);
3172 let result = self.normalize_associated_types_in(span, &value);
3173 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}", value, substs, result);
3177 /// As `instantiate_type_scheme`, but for the bounds found in a
3178 /// generic type scheme.
3179 fn instantiate_bounds(
3183 substs: SubstsRef<'tcx>,
3184 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
3185 let bounds = self.tcx.predicates_of(def_id);
3186 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
3187 let result = bounds.instantiate(self.tcx, substs);
3188 let result = self.normalize_associated_types_in(span, &result);
3190 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
3191 bounds, substs, result, spans,
3196 /// Replaces the opaque types from the given value with type variables,
3197 /// and records the `OpaqueTypeMap` for later use during writeback. See
3198 /// `InferCtxt::instantiate_opaque_types` for more details.
3199 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
3201 parent_id: hir::HirId,
3205 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
3207 "instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
3208 parent_def_id, value
3211 let (value, opaque_type_map) =
3212 self.register_infer_ok_obligations(self.instantiate_opaque_types(
3220 let mut opaque_types = self.opaque_types.borrow_mut();
3221 let mut opaque_types_vars = self.opaque_types_vars.borrow_mut();
3222 for (ty, decl) in opaque_type_map {
3223 let _ = opaque_types.insert(ty, decl);
3224 let _ = opaque_types_vars.insert(decl.concrete_ty, decl.opaque_type);
3230 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
3232 T: TypeFoldable<'tcx>,
3234 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
3237 fn normalize_associated_types_in_as_infer_ok<T>(
3241 ) -> InferOk<'tcx, T>
3243 T: TypeFoldable<'tcx>,
3245 self.inh.partially_normalize_associated_types_in(span, self.body_id, self.param_env, value)
3248 pub fn require_type_meets(
3252 code: traits::ObligationCauseCode<'tcx>,
3255 self.register_bound(ty, def_id, traits::ObligationCause::new(span, self.body_id, code));
3258 pub fn require_type_is_sized(
3262 code: traits::ObligationCauseCode<'tcx>,
3264 if !ty.references_error() {
3265 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
3266 self.require_type_meets(ty, span, code, lang_item);
3270 pub fn require_type_is_sized_deferred(
3274 code: traits::ObligationCauseCode<'tcx>,
3276 if !ty.references_error() {
3277 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
3281 pub fn register_bound(
3285 cause: traits::ObligationCause<'tcx>,
3287 if !ty.references_error() {
3288 self.fulfillment_cx.borrow_mut().register_bound(
3298 pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> {
3299 let t = AstConv::ast_ty_to_ty(self, ast_t);
3300 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
3304 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
3305 let ty = self.to_ty(ast_ty);
3306 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
3308 if Self::can_contain_user_lifetime_bounds(ty) {
3309 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
3310 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
3311 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
3317 pub fn to_const(&self, ast_c: &hir::AnonConst) -> &'tcx ty::Const<'tcx> {
3318 let const_def_id = self.tcx.hir().local_def_id(ast_c.hir_id).expect_local();
3319 let c = ty::Const::from_anon_const(self.tcx, const_def_id);
3321 // HACK(eddyb) emulate what a `WellFormedConst` obligation would do.
3322 // This code should be replaced with the proper WF handling ASAP.
3323 if let ty::ConstKind::Unevaluated(def_id, substs, promoted) = c.val {
3324 assert!(promoted.is_none());
3326 // HACK(eddyb) let's hope these are always empty.
3327 // let obligations = self.nominal_obligations(def_id, substs);
3328 // self.out.extend(obligations);
3330 let cause = traits::ObligationCause::new(
3331 self.tcx.def_span(const_def_id.to_def_id()),
3333 traits::MiscObligation,
3335 self.register_predicate(traits::Obligation::new(
3338 ty::Predicate::ConstEvaluatable(def_id, substs),
3345 // If the type given by the user has free regions, save it for later, since
3346 // NLL would like to enforce those. Also pass in types that involve
3347 // projections, since those can resolve to `'static` bounds (modulo #54940,
3348 // which hopefully will be fixed by the time you see this comment, dear
3349 // reader, although I have my doubts). Also pass in types with inference
3350 // types, because they may be repeated. Other sorts of things are already
3351 // sufficiently enforced with erased regions. =)
3352 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
3354 T: TypeFoldable<'tcx>,
3356 t.has_free_regions() || t.has_projections() || t.has_infer_types()
3359 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
3360 match self.tables.borrow().node_types().get(id) {
3362 None if self.is_tainted_by_errors() => self.tcx.types.err,
3365 "no type for node {}: {} in fcx {}",
3367 self.tcx.hir().node_to_string(id),
3374 /// Registers an obligation for checking later, during regionck, that the type `ty` must
3375 /// outlive the region `r`.
3376 pub fn register_wf_obligation(
3380 code: traits::ObligationCauseCode<'tcx>,
3382 // WF obligations never themselves fail, so no real need to give a detailed cause:
3383 let cause = traits::ObligationCause::new(span, self.body_id, code);
3384 self.register_predicate(traits::Obligation::new(
3387 ty::Predicate::WellFormed(ty),
3391 /// Registers obligations that all types appearing in `substs` are well-formed.
3392 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr<'_>) {
3393 for ty in substs.types() {
3394 if !ty.references_error() {
3395 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
3400 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
3401 /// type/region parameter was instantiated (`substs`), creates and registers suitable
3402 /// trait/region obligations.
3404 /// For example, if there is a function:
3407 /// fn foo<'a,T:'a>(...)
3410 /// and a reference:
3416 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
3417 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
3418 pub fn add_obligations_for_parameters(
3420 cause: traits::ObligationCause<'tcx>,
3421 predicates: &ty::InstantiatedPredicates<'tcx>,
3423 assert!(!predicates.has_escaping_bound_vars());
3425 debug!("add_obligations_for_parameters(predicates={:?})", predicates);
3427 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
3428 self.register_predicate(obligation);
3432 // FIXME(arielb1): use this instead of field.ty everywhere
3433 // Only for fields! Returns <none> for methods>
3434 // Indifferent to privacy flags
3438 field: &'tcx ty::FieldDef,
3439 substs: SubstsRef<'tcx>,
3441 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
3444 fn check_casts(&self) {
3445 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3446 for cast in deferred_cast_checks.drain(..) {
3451 fn resolve_generator_interiors(&self, def_id: DefId) {
3452 let mut generators = self.deferred_generator_interiors.borrow_mut();
3453 for (body_id, interior, kind) in generators.drain(..) {
3454 self.select_obligations_where_possible(false, |_| {});
3455 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
3459 // Tries to apply a fallback to `ty` if it is an unsolved variable.
3461 // - Unconstrained ints are replaced with `i32`.
3463 // - Unconstrained floats are replaced with with `f64`.
3465 // - Non-numerics get replaced with `!` when `#![feature(never_type_fallback)]`
3466 // is enabled. Otherwise, they are replaced with `()`.
3468 // Fallback becomes very dubious if we have encountered type-checking errors.
3469 // In that case, fallback to Error.
3470 // The return value indicates whether fallback has occurred.
3471 fn fallback_if_possible(&self, ty: Ty<'tcx>, mode: FallbackMode) -> bool {
3472 use rustc_middle::ty::error::UnconstrainedNumeric::Neither;
3473 use rustc_middle::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt};
3475 assert!(ty.is_ty_infer());
3476 let fallback = match self.type_is_unconstrained_numeric(ty) {
3477 _ if self.is_tainted_by_errors() => self.tcx().types.err,
3478 UnconstrainedInt => self.tcx.types.i32,
3479 UnconstrainedFloat => self.tcx.types.f64,
3480 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
3482 // This type variable was created from the instantiation of an opaque
3483 // type. The fact that we're attempting to perform fallback for it
3484 // means that the function neither constrained it to a concrete
3485 // type, nor to the opaque type itself.
3487 // For example, in this code:
3490 // type MyType = impl Copy;
3491 // fn defining_use() -> MyType { true }
3492 // fn other_use() -> MyType { defining_use() }
3495 // `defining_use` will constrain the instantiated inference
3496 // variable to `bool`, while `other_use` will constrain
3497 // the instantiated inference variable to `MyType`.
3499 // When we process opaque types during writeback, we
3500 // will handle cases like `other_use`, and not count
3501 // them as defining usages
3503 // However, we also need to handle cases like this:
3506 // pub type Foo = impl Copy;
3507 // fn produce() -> Option<Foo> {
3512 // In the above snippet, the inference variable created by
3513 // instantiating `Option<Foo>` will be completely unconstrained.
3514 // We treat this as a non-defining use by making the inference
3515 // variable fall back to the opaque type itself.
3516 if let FallbackMode::All = mode {
3517 if let Some(opaque_ty) = self.opaque_types_vars.borrow().get(ty) {
3519 "fallback_if_possible: falling back opaque type var {:?} to {:?}",
3531 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
3532 self.demand_eqtype(rustc_span::DUMMY_SP, ty, fallback);
3536 fn select_all_obligations_or_error(&self) {
3537 debug!("select_all_obligations_or_error");
3538 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
3539 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
3543 /// Select as many obligations as we can at present.
3544 fn select_obligations_where_possible(
3546 fallback_has_occurred: bool,
3547 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
3549 let result = self.fulfillment_cx.borrow_mut().select_where_possible(self);
3550 if let Err(mut errors) = result {
3551 mutate_fullfillment_errors(&mut errors);
3552 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
3556 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
3557 /// returns a type of `&T`, but the actual type we assign to the
3558 /// *expression* is `T`. So this function just peels off the return
3559 /// type by one layer to yield `T`.
3560 fn make_overloaded_place_return_type(
3562 method: MethodCallee<'tcx>,
3563 ) -> ty::TypeAndMut<'tcx> {
3564 // extract method return type, which will be &T;
3565 let ret_ty = method.sig.output();
3567 // method returns &T, but the type as visible to user is T, so deref
3568 ret_ty.builtin_deref(true).unwrap()
3573 expr: &hir::Expr<'_>,
3574 base_expr: &'tcx hir::Expr<'tcx>,
3578 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3579 // FIXME(#18741) -- this is almost but not quite the same as the
3580 // autoderef that normal method probing does. They could likely be
3583 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3584 let mut result = None;
3585 while result.is_none() && autoderef.next().is_some() {
3586 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3588 autoderef.finalize(self);
3592 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3593 /// (and otherwise adjust) `base_expr`, looking for a type which either
3594 /// supports builtin indexing or overloaded indexing.
3595 /// This loop implements one step in that search; the autoderef loop
3596 /// is implemented by `lookup_indexing`.
3599 expr: &hir::Expr<'_>,
3600 base_expr: &hir::Expr<'_>,
3601 autoderef: &Autoderef<'a, 'tcx>,
3604 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3605 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3607 "try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3609 expr, base_expr, adjusted_ty, index_ty
3612 for &unsize in &[false, true] {
3613 let mut self_ty = adjusted_ty;
3615 // We only unsize arrays here.
3616 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3617 self_ty = self.tcx.mk_slice(element_ty);
3623 // If some lookup succeeds, write callee into table and extract index/element
3624 // type from the method signature.
3625 // If some lookup succeeded, install method in table
3626 let input_ty = self.next_ty_var(TypeVariableOrigin {
3627 kind: TypeVariableOriginKind::AutoDeref,
3628 span: base_expr.span,
3630 let method = self.try_overloaded_place_op(
3638 let result = method.map(|ok| {
3639 debug!("try_index_step: success, using overloaded indexing");
3640 let method = self.register_infer_ok_obligations(ok);
3642 let mut adjustments = autoderef.adjust_steps(self, needs);
3643 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3644 let mutbl = match r_mutbl {
3645 hir::Mutability::Not => AutoBorrowMutability::Not,
3646 hir::Mutability::Mut => AutoBorrowMutability::Mut {
3647 // Indexing can be desugared to a method call,
3648 // so maybe we could use two-phase here.
3649 // See the documentation of AllowTwoPhase for why that's
3650 // not the case today.
3651 allow_two_phase_borrow: AllowTwoPhase::No,
3654 adjustments.push(Adjustment {
3655 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3658 .mk_ref(region, ty::TypeAndMut { mutbl: r_mutbl, ty: adjusted_ty }),
3662 adjustments.push(Adjustment {
3663 kind: Adjust::Pointer(PointerCast::Unsize),
3664 target: method.sig.inputs()[0],
3667 self.apply_adjustments(base_expr, adjustments);
3669 self.write_method_call(expr.hir_id, method);
3670 (input_ty, self.make_overloaded_place_return_type(method).ty)
3672 if result.is_some() {
3680 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3681 let (tr, name) = match (op, is_mut) {
3682 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3683 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3684 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3685 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3687 (tr, ast::Ident::with_dummy_span(name))
3690 fn try_overloaded_place_op(
3694 arg_tys: &[Ty<'tcx>],
3697 ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
3698 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})", span, base_ty, needs, op);
3700 // Try Mut first, if needed.
3701 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3702 let method = match (needs, mut_tr) {
3703 (Needs::MutPlace, Some(trait_did)) => {
3704 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3709 // Otherwise, fall back to the immutable version.
3710 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3711 match (method, imm_tr) {
3712 (None, Some(trait_did)) => {
3713 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3715 (method, _) => method,
3719 fn check_method_argument_types(
3722 expr: &'tcx hir::Expr<'tcx>,
3723 method: Result<MethodCallee<'tcx>, ()>,
3724 args_no_rcvr: &'tcx [hir::Expr<'tcx>],
3725 tuple_arguments: TupleArgumentsFlag,
3726 expected: Expectation<'tcx>,
3728 let has_error = match method {
3729 Ok(method) => method.substs.references_error() || method.sig.references_error(),
3733 let err_inputs = self.err_args(args_no_rcvr.len());
3735 let err_inputs = match tuple_arguments {
3736 DontTupleArguments => err_inputs,
3737 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3740 self.check_argument_types(
3750 return self.tcx.types.err;
3753 let method = method.unwrap();
3754 // HACK(eddyb) ignore self in the definition (see above).
3755 let expected_arg_tys = self.expected_inputs_for_expected_output(
3758 method.sig.output(),
3759 &method.sig.inputs()[1..],
3761 self.check_argument_types(
3764 &method.sig.inputs()[1..],
3765 &expected_arg_tys[..],
3767 method.sig.c_variadic,
3769 self.tcx.hir().span_if_local(method.def_id),
3774 fn self_type_matches_expected_vid(
3776 trait_ref: ty::PolyTraitRef<'tcx>,
3777 expected_vid: ty::TyVid,
3779 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3781 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3782 trait_ref, self_ty, expected_vid
3784 match self_ty.kind {
3785 ty::Infer(ty::TyVar(found_vid)) => {
3786 // FIXME: consider using `sub_root_var` here so we
3787 // can see through subtyping.
3788 let found_vid = self.root_var(found_vid);
3789 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3790 expected_vid == found_vid
3796 fn obligations_for_self_ty<'b>(
3799 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3802 // FIXME: consider using `sub_root_var` here so we
3803 // can see through subtyping.
3804 let ty_var_root = self.root_var(self_ty);
3806 "obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3809 self.fulfillment_cx.borrow().pending_obligations()
3814 .pending_obligations()
3816 .filter_map(move |obligation| match obligation.predicate {
3817 ty::Predicate::Projection(ref data) => {
3818 Some((data.to_poly_trait_ref(self.tcx), obligation))
3820 ty::Predicate::Trait(ref data, _) => Some((data.to_poly_trait_ref(), obligation)),
3821 ty::Predicate::Subtype(..) => None,
3822 ty::Predicate::RegionOutlives(..) => None,
3823 ty::Predicate::TypeOutlives(..) => None,
3824 ty::Predicate::WellFormed(..) => None,
3825 ty::Predicate::ObjectSafe(..) => None,
3826 ty::Predicate::ConstEvaluatable(..) => None,
3827 // N.B., this predicate is created by breaking down a
3828 // `ClosureType: FnFoo()` predicate, where
3829 // `ClosureType` represents some `Closure`. It can't
3830 // possibly be referring to the current closure,
3831 // because we haven't produced the `Closure` for
3832 // this closure yet; this is exactly why the other
3833 // code is looking for a self type of a unresolved
3834 // inference variable.
3835 ty::Predicate::ClosureKind(..) => None,
3837 .filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3840 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3841 self.obligations_for_self_ty(self_ty)
3842 .any(|(tr, _)| Some(tr.def_id()) == self.tcx.lang_items().sized_trait())
3845 /// Generic function that factors out common logic from function calls,
3846 /// method calls and overloaded operators.
3847 fn check_argument_types(
3850 expr: &'tcx hir::Expr<'tcx>,
3851 fn_inputs: &[Ty<'tcx>],
3852 expected_arg_tys: &[Ty<'tcx>],
3853 args: &'tcx [hir::Expr<'tcx>],
3855 tuple_arguments: TupleArgumentsFlag,
3856 def_span: Option<Span>,
3859 // Grab the argument types, supplying fresh type variables
3860 // if the wrong number of arguments were supplied
3861 let supplied_arg_count = if tuple_arguments == DontTupleArguments { args.len() } else { 1 };
3863 // All the input types from the fn signature must outlive the call
3864 // so as to validate implied bounds.
3865 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3866 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3869 let expected_arg_count = fn_inputs.len();
3871 let param_count_error = |expected_count: usize,
3876 let (span, start_span, args) = match &expr.kind {
3877 hir::ExprKind::Call(hir::Expr { span, .. }, args) => (*span, *span, &args[..]),
3878 hir::ExprKind::MethodCall(path_segment, span, args) => (
3880 // `sp` doesn't point at the whole `foo.bar()`, only at `bar`.
3883 .and_then(|args| args.args.iter().last())
3884 // Account for `foo.bar::<T>()`.
3886 // Skip the closing `>`.
3889 .next_point(tcx.sess.source_map().next_point(arg.span()))
3892 &args[1..], // Skip the receiver.
3894 k => span_bug!(sp, "checking argument types on a non-call: `{:?}`", k),
3896 let arg_spans = if args.is_empty() {
3898 // ^^^-- supplied 0 arguments
3900 // expected 2 arguments
3901 vec![tcx.sess.source_map().next_point(start_span).with_hi(sp.hi())]
3904 // ^^^ - - - supplied 3 arguments
3906 // expected 2 arguments
3907 args.iter().map(|arg| arg.span).collect::<Vec<Span>>()
3910 let mut err = tcx.sess.struct_span_err_with_code(
3913 "this function takes {}{} but {} {} supplied",
3914 if c_variadic { "at least " } else { "" },
3915 potentially_plural_count(expected_count, "argument"),
3916 potentially_plural_count(arg_count, "argument"),
3917 if arg_count == 1 { "was" } else { "were" }
3919 DiagnosticId::Error(error_code.to_owned()),
3921 let label = format!("supplied {}", potentially_plural_count(arg_count, "argument"));
3922 for (i, span) in arg_spans.into_iter().enumerate() {
3925 if arg_count == 0 || i + 1 == arg_count { &label } else { "" },
3929 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().guess_head_span(sp)) {
3930 err.span_label(def_s, "defined here");
3933 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3934 // remove closing `)` from the span
3935 let sugg_span = sugg_span.shrink_to_lo();
3936 err.span_suggestion(
3938 "expected the unit value `()`; create it with empty parentheses",
3940 Applicability::MachineApplicable,
3947 if c_variadic { "at least " } else { "" },
3948 potentially_plural_count(expected_count, "argument")
3955 let mut expected_arg_tys = expected_arg_tys.to_vec();
3957 let formal_tys = if tuple_arguments == TupleArguments {
3958 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3959 match tuple_type.kind {
3960 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3961 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3962 expected_arg_tys = vec![];
3963 self.err_args(args.len())
3965 ty::Tuple(arg_types) => {
3966 expected_arg_tys = match expected_arg_tys.get(0) {
3967 Some(&ty) => match ty.kind {
3968 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3973 arg_types.iter().map(|k| k.expect_ty()).collect()
3980 "cannot use call notation; the first type parameter \
3981 for the function trait is neither a tuple nor unit"
3984 expected_arg_tys = vec![];
3985 self.err_args(args.len())
3988 } else if expected_arg_count == supplied_arg_count {
3990 } else if c_variadic {
3991 if supplied_arg_count >= expected_arg_count {
3994 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
3995 expected_arg_tys = vec![];
3996 self.err_args(supplied_arg_count)
3999 // is the missing argument of type `()`?
4000 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
4001 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
4002 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
4003 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
4007 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
4009 expected_arg_tys = vec![];
4010 self.err_args(supplied_arg_count)
4014 "check_argument_types: formal_tys={:?}",
4015 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>()
4018 // If there is no expectation, expect formal_tys.
4019 let expected_arg_tys =
4020 if !expected_arg_tys.is_empty() { expected_arg_tys } else { formal_tys.clone() };
4022 let mut final_arg_types: Vec<(usize, Ty<'_>, Ty<'_>)> = vec![];
4024 // Check the arguments.
4025 // We do this in a pretty awful way: first we type-check any arguments
4026 // that are not closures, then we type-check the closures. This is so
4027 // that we have more information about the types of arguments when we
4028 // type-check the functions. This isn't really the right way to do this.
4029 for &check_closures in &[false, true] {
4030 debug!("check_closures={}", check_closures);
4032 // More awful hacks: before we check argument types, try to do
4033 // an "opportunistic" vtable resolution of any trait bounds on
4034 // the call. This helps coercions.
4036 self.select_obligations_where_possible(false, |errors| {
4037 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
4038 self.point_at_arg_instead_of_call_if_possible(
4040 &final_arg_types[..],
4047 // For C-variadic functions, we don't have a declared type for all of
4048 // the arguments hence we only do our usual type checking with
4049 // the arguments who's types we do know.
4050 let t = if c_variadic {
4052 } else if tuple_arguments == TupleArguments {
4057 for (i, arg) in args.iter().take(t).enumerate() {
4058 // Warn only for the first loop (the "no closures" one).
4059 // Closure arguments themselves can't be diverging, but
4060 // a previous argument can, e.g., `foo(panic!(), || {})`.
4061 if !check_closures {
4062 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
4065 let is_closure = match arg.kind {
4066 ExprKind::Closure(..) => true,
4070 if is_closure != check_closures {
4074 debug!("checking the argument");
4075 let formal_ty = formal_tys[i];
4077 // The special-cased logic below has three functions:
4078 // 1. Provide as good of an expected type as possible.
4079 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
4081 let checked_ty = self.check_expr_with_expectation(&arg, expected);
4083 // 2. Coerce to the most detailed type that could be coerced
4084 // to, which is `expected_ty` if `rvalue_hint` returns an
4085 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
4086 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
4087 // We're processing function arguments so we definitely want to use
4088 // two-phase borrows.
4089 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
4090 final_arg_types.push((i, checked_ty, coerce_ty));
4092 // 3. Relate the expected type and the formal one,
4093 // if the expected type was used for the coercion.
4094 self.demand_suptype(arg.span, formal_ty, coerce_ty);
4098 // We also need to make sure we at least write the ty of the other
4099 // arguments which we skipped above.
4101 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
4102 use crate::structured_errors::{StructuredDiagnostic, VariadicError};
4103 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
4106 for arg in args.iter().skip(expected_arg_count) {
4107 let arg_ty = self.check_expr(&arg);
4109 // There are a few types which get autopromoted when passed via varargs
4110 // in C but we just error out instead and require explicit casts.
4111 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
4113 ty::Float(ast::FloatTy::F32) => {
4114 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
4116 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
4117 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
4119 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
4120 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
4123 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
4124 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
4125 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
4133 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
4134 vec![self.tcx.types.err; len]
4137 /// Given a vec of evaluated `FulfillmentError`s and an `fn` call argument expressions, we walk
4138 /// the checked and coerced types for each argument to see if any of the `FulfillmentError`s
4139 /// reference a type argument. The reason to walk also the checked type is that the coerced type
4140 /// can be not easily comparable with predicate type (because of coercion). If the types match
4141 /// for either checked or coerced type, and there's only *one* argument that does, we point at
4142 /// the corresponding argument's expression span instead of the `fn` call path span.
4143 fn point_at_arg_instead_of_call_if_possible(
4145 errors: &mut Vec<traits::FulfillmentError<'_>>,
4146 final_arg_types: &[(usize, Ty<'tcx>, Ty<'tcx>)],
4148 args: &'tcx [hir::Expr<'tcx>],
4150 // We *do not* do this for desugared call spans to keep good diagnostics when involving
4151 // the `?` operator.
4152 if call_sp.desugaring_kind().is_some() {
4156 for error in errors {
4157 // Only if the cause is somewhere inside the expression we want try to point at arg.
4158 // Otherwise, it means that the cause is somewhere else and we should not change
4159 // anything because we can break the correct span.
4160 if !call_sp.contains(error.obligation.cause.span) {
4164 if let ty::Predicate::Trait(predicate, _) = error.obligation.predicate {
4165 // Collect the argument position for all arguments that could have caused this
4166 // `FulfillmentError`.
4167 let mut referenced_in = final_arg_types
4169 .map(|&(i, checked_ty, _)| (i, checked_ty))
4170 .chain(final_arg_types.iter().map(|&(i, _, coerced_ty)| (i, coerced_ty)))
4171 .flat_map(|(i, ty)| {
4172 let ty = self.resolve_vars_if_possible(&ty);
4173 // We walk the argument type because the argument's type could have
4174 // been `Option<T>`, but the `FulfillmentError` references `T`.
4175 if ty.walk().any(|arg| arg == predicate.skip_binder().self_ty().into()) {
4181 .collect::<Vec<_>>();
4183 // Both checked and coerced types could have matched, thus we need to remove
4185 referenced_in.sort();
4186 referenced_in.dedup();
4188 if let (Some(ref_in), None) = (referenced_in.pop(), referenced_in.pop()) {
4189 // We make sure that only *one* argument matches the obligation failure
4190 // and we assign the obligation's span to its expression's.
4191 error.obligation.cause.span = args[ref_in].span;
4192 error.points_at_arg_span = true;
4198 /// Given a vec of evaluated `FulfillmentError`s and an `fn` call expression, we walk the
4199 /// `PathSegment`s and resolve their type parameters to see if any of the `FulfillmentError`s
4200 /// were caused by them. If they were, we point at the corresponding type argument's span
4201 /// instead of the `fn` call path span.
4202 fn point_at_type_arg_instead_of_call_if_possible(
4204 errors: &mut Vec<traits::FulfillmentError<'_>>,
4205 call_expr: &'tcx hir::Expr<'tcx>,
4207 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
4208 if let hir::ExprKind::Path(qpath) = &path.kind {
4209 if let hir::QPath::Resolved(_, path) = &qpath {
4210 for error in errors {
4211 if let ty::Predicate::Trait(predicate, _) = error.obligation.predicate {
4212 // If any of the type arguments in this path segment caused the
4213 // `FullfillmentError`, point at its span (#61860).
4217 .filter_map(|seg| seg.args.as_ref())
4218 .flat_map(|a| a.args.iter())
4220 if let hir::GenericArg::Type(hir_ty) = &arg {
4221 if let hir::TyKind::Path(hir::QPath::TypeRelative(..)) =
4224 // Avoid ICE with associated types. As this is best
4225 // effort only, it's ok to ignore the case. It
4226 // would trigger in `is_send::<T::AssocType>();`
4227 // from `typeck-default-trait-impl-assoc-type.rs`.
4229 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
4230 let ty = self.resolve_vars_if_possible(&ty);
4231 if ty == predicate.skip_binder().self_ty() {
4232 error.obligation.cause.span = hir_ty.span;
4244 // AST fragment checking
4245 fn check_lit(&self, lit: &hir::Lit, expected: Expectation<'tcx>) -> Ty<'tcx> {
4249 ast::LitKind::Str(..) => tcx.mk_static_str(),
4250 ast::LitKind::ByteStr(ref v) => {
4251 tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.u8, v.len() as u64))
4253 ast::LitKind::Byte(_) => tcx.types.u8,
4254 ast::LitKind::Char(_) => tcx.types.char,
4255 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
4256 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
4257 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
4258 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind {
4259 ty::Int(_) | ty::Uint(_) => Some(ty),
4260 ty::Char => Some(tcx.types.u8),
4261 ty::RawPtr(..) => Some(tcx.types.usize),
4262 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
4265 opt_ty.unwrap_or_else(|| self.next_int_var())
4267 ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => tcx.mk_mach_float(t),
4268 ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => {
4269 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind {
4270 ty::Float(_) => Some(ty),
4273 opt_ty.unwrap_or_else(|| self.next_float_var())
4275 ast::LitKind::Bool(_) => tcx.types.bool,
4276 ast::LitKind::Err(_) => tcx.types.err,
4280 /// Unifies the output type with the expected type early, for more coercions
4281 /// and forward type information on the input expressions.
4282 fn expected_inputs_for_expected_output(
4285 expected_ret: Expectation<'tcx>,
4286 formal_ret: Ty<'tcx>,
4287 formal_args: &[Ty<'tcx>],
4288 ) -> Vec<Ty<'tcx>> {
4289 let formal_ret = self.resolve_vars_with_obligations(formal_ret);
4290 let ret_ty = match expected_ret.only_has_type(self) {
4292 None => return Vec::new(),
4294 let expect_args = self
4295 .fudge_inference_if_ok(|| {
4296 // Attempt to apply a subtyping relationship between the formal
4297 // return type (likely containing type variables if the function
4298 // is polymorphic) and the expected return type.
4299 // No argument expectations are produced if unification fails.
4300 let origin = self.misc(call_span);
4301 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
4303 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
4304 // to identity so the resulting type is not constrained.
4307 // Process any obligations locally as much as
4308 // we can. We don't care if some things turn
4309 // out unconstrained or ambiguous, as we're
4310 // just trying to get hints here.
4311 self.save_and_restore_in_snapshot_flag(|_| {
4312 let mut fulfill = TraitEngine::new(self.tcx);
4313 for obligation in ok.obligations {
4314 fulfill.register_predicate_obligation(self, obligation);
4316 fulfill.select_where_possible(self)
4320 Err(_) => return Err(()),
4323 // Record all the argument types, with the substitutions
4324 // produced from the above subtyping unification.
4325 Ok(formal_args.iter().map(|ty| self.resolve_vars_if_possible(ty)).collect())
4327 .unwrap_or_default();
4329 "expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
4330 formal_args, formal_ret, expect_args, expected_ret
4335 pub fn check_struct_path(
4339 ) -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
4340 let path_span = match *qpath {
4341 QPath::Resolved(_, ref path) => path.span,
4342 QPath::TypeRelative(ref qself, _) => qself.span,
4344 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
4345 let variant = match def {
4347 self.set_tainted_by_errors();
4350 Res::Def(DefKind::Variant, _) => match ty.kind {
4351 ty::Adt(adt, substs) => Some((adt.variant_of_res(def), adt.did, substs)),
4352 _ => bug!("unexpected type: {:?}", ty),
4354 Res::Def(DefKind::Struct, _)
4355 | Res::Def(DefKind::Union, _)
4356 | Res::Def(DefKind::TyAlias, _)
4357 | Res::Def(DefKind::AssocTy, _)
4358 | Res::SelfTy(..) => match ty.kind {
4359 ty::Adt(adt, substs) if !adt.is_enum() => {
4360 Some((adt.non_enum_variant(), adt.did, substs))
4364 _ => bug!("unexpected definition: {:?}", def),
4367 if let Some((variant, did, substs)) = variant {
4368 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
4369 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
4371 // Check bounds on type arguments used in the path.
4372 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
4374 traits::ObligationCause::new(path_span, self.body_id, traits::ItemObligation(did));
4375 self.add_obligations_for_parameters(cause, &bounds);
4383 "expected struct, variant or union type, found {}",
4384 ty.sort_string(self.tcx)
4386 .span_label(path_span, "not a struct")
4392 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4393 // The newly resolved definition is written into `type_dependent_defs`.
4394 fn finish_resolving_struct_path(
4399 ) -> (Res, Ty<'tcx>) {
4401 QPath::Resolved(ref maybe_qself, ref path) => {
4402 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4403 let ty = AstConv::res_to_ty(self, self_ty, path, true);
4406 QPath::TypeRelative(ref qself, ref segment) => {
4407 let ty = self.to_ty(qself);
4409 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
4415 AstConv::associated_path_to_ty(self, hir_id, path_span, ty, res, segment, true);
4416 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
4417 let result = result.map(|(_, kind, def_id)| (kind, def_id));
4419 // Write back the new resolution.
4420 self.write_resolution(hir_id, result);
4422 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
4427 /// Resolves an associated value path into a base type and associated constant, or method
4428 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
4429 pub fn resolve_ty_and_res_ufcs<'b>(
4431 qpath: &'b QPath<'b>,
4434 ) -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment<'b>]) {
4435 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
4436 let (ty, qself, item_segment) = match *qpath {
4437 QPath::Resolved(ref opt_qself, ref path) => {
4440 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4444 QPath::TypeRelative(ref qself, ref segment) => (self.to_ty(qself), qself, segment),
4446 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
4447 // Return directly on cache hit. This is useful to avoid doubly reporting
4448 // errors with default match binding modes. See #44614.
4450 cached_result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err);
4451 return (def, Some(ty), slice::from_ref(&**item_segment));
4453 let item_name = item_segment.ident;
4454 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
4455 let result = match error {
4456 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
4457 _ => Err(ErrorReported),
4459 if item_name.name != kw::Invalid {
4460 self.report_method_error(
4464 SelfSource::QPath(qself),
4468 .map(|mut e| e.emit());
4473 // Write back the new resolution.
4474 self.write_resolution(hir_id, result);
4476 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
4478 slice::from_ref(&**item_segment),
4482 pub fn check_decl_initializer(
4484 local: &'tcx hir::Local<'tcx>,
4485 init: &'tcx hir::Expr<'tcx>,
4487 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
4488 // for #42640 (default match binding modes).
4491 let ref_bindings = local.pat.contains_explicit_ref_binding();
4493 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
4494 if let Some(m) = ref_bindings {
4495 // Somewhat subtle: if we have a `ref` binding in the pattern,
4496 // we want to avoid introducing coercions for the RHS. This is
4497 // both because it helps preserve sanity and, in the case of
4498 // ref mut, for soundness (issue #23116). In particular, in
4499 // the latter case, we need to be clear that the type of the
4500 // referent for the reference that results is *equal to* the
4501 // type of the place it is referencing, and not some
4502 // supertype thereof.
4503 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4504 self.demand_eqtype(init.span, local_ty, init_ty);
4507 self.check_expr_coercable_to_type(init, local_ty)
4511 /// Type check a `let` statement.
4512 pub fn check_decl_local(&self, local: &'tcx hir::Local<'tcx>) {
4513 // Determine and write the type which we'll check the pattern against.
4514 let ty = self.local_ty(local.span, local.hir_id).decl_ty;
4515 self.write_ty(local.hir_id, ty);
4517 // Type check the initializer.
4518 if let Some(ref init) = local.init {
4519 let init_ty = self.check_decl_initializer(local, &init);
4520 self.overwrite_local_ty_if_err(local, ty, init_ty);
4523 // Does the expected pattern type originate from an expression and what is the span?
4524 let (origin_expr, ty_span) = match (local.ty, local.init) {
4525 (Some(ty), _) => (false, Some(ty.span)), // Bias towards the explicit user type.
4526 (_, Some(init)) => (true, Some(init.span)), // No explicit type; so use the scrutinee.
4527 _ => (false, None), // We have `let $pat;`, so the expected type is unconstrained.
4530 // Type check the pattern. Override if necessary to avoid knock-on errors.
4531 self.check_pat_top(&local.pat, ty, ty_span, origin_expr);
4532 let pat_ty = self.node_ty(local.pat.hir_id);
4533 self.overwrite_local_ty_if_err(local, ty, pat_ty);
4536 fn overwrite_local_ty_if_err(
4538 local: &'tcx hir::Local<'tcx>,
4542 if ty.references_error() {
4543 // Override the types everywhere with `types.err` to avoid knock on errors.
4544 self.write_ty(local.hir_id, ty);
4545 self.write_ty(local.pat.hir_id, ty);
4546 let local_ty = LocalTy { decl_ty, revealed_ty: ty };
4547 self.locals.borrow_mut().insert(local.hir_id, local_ty);
4548 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
4552 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
4553 err.span_suggestion_short(
4554 span.shrink_to_hi(),
4555 "consider using a semicolon here",
4557 Applicability::MachineApplicable,
4561 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>) {
4562 // Don't do all the complex logic below for `DeclItem`.
4564 hir::StmtKind::Item(..) => return,
4565 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
4568 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
4570 // Hide the outer diverging and `has_errors` flags.
4571 let old_diverges = self.diverges.replace(Diverges::Maybe);
4572 let old_has_errors = self.has_errors.replace(false);
4575 hir::StmtKind::Local(ref l) => {
4576 self.check_decl_local(&l);
4579 hir::StmtKind::Item(_) => {}
4580 hir::StmtKind::Expr(ref expr) => {
4581 // Check with expected type of `()`.
4582 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
4583 self.suggest_semicolon_at_end(expr.span, err);
4586 hir::StmtKind::Semi(ref expr) => {
4587 self.check_expr(&expr);
4591 // Combine the diverging and `has_error` flags.
4592 self.diverges.set(self.diverges.get() | old_diverges);
4593 self.has_errors.set(self.has_errors.get() | old_has_errors);
4596 pub fn check_block_no_value(&self, blk: &'tcx hir::Block<'tcx>) {
4597 let unit = self.tcx.mk_unit();
4598 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4600 // if the block produces a `!` value, that can always be
4601 // (effectively) coerced to unit.
4603 self.demand_suptype(blk.span, unit, ty);
4607 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
4608 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
4609 /// when given code like the following:
4611 /// if false { return 0i32; } else { 1u32 }
4612 /// // ^^^^ point at this instead of the whole `if` expression
4614 fn get_expr_coercion_span(&self, expr: &hir::Expr<'_>) -> rustc_span::Span {
4615 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
4616 let arm_spans: Vec<Span> = arms
4619 self.in_progress_tables
4620 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
4621 .and_then(|arm_ty| {
4622 if arm_ty.is_never() {
4625 Some(match &arm.body.kind {
4626 // Point at the tail expression when possible.
4627 hir::ExprKind::Block(block, _) => {
4628 block.expr.as_ref().map(|e| e.span).unwrap_or(block.span)
4636 if arm_spans.len() == 1 {
4637 return arm_spans[0];
4643 fn check_block_with_expected(
4645 blk: &'tcx hir::Block<'tcx>,
4646 expected: Expectation<'tcx>,
4649 let mut fcx_ps = self.ps.borrow_mut();
4650 let unsafety_state = fcx_ps.recurse(blk);
4651 replace(&mut *fcx_ps, unsafety_state)
4654 // In some cases, blocks have just one exit, but other blocks
4655 // can be targeted by multiple breaks. This can happen both
4656 // with labeled blocks as well as when we desugar
4657 // a `try { ... }` expression.
4661 // 'a: { if true { break 'a Err(()); } Ok(()) }
4663 // Here we would wind up with two coercions, one from
4664 // `Err(())` and the other from the tail expression
4665 // `Ok(())`. If the tail expression is omitted, that's a
4666 // "forced unit" -- unless the block diverges, in which
4667 // case we can ignore the tail expression (e.g., `'a: {
4668 // break 'a 22; }` would not force the type of the block
4670 let tail_expr = blk.expr.as_ref();
4671 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4672 let coerce = if blk.targeted_by_break {
4673 CoerceMany::new(coerce_to_ty)
4675 let tail_expr: &[&hir::Expr<'_>] = match tail_expr {
4676 Some(e) => slice::from_ref(e),
4679 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4682 let prev_diverges = self.diverges.get();
4683 let ctxt = BreakableCtxt { coerce: Some(coerce), may_break: false };
4685 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4686 for s in blk.stmts {
4690 // check the tail expression **without** holding the
4691 // `enclosing_breakables` lock below.
4692 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4694 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4695 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4696 let coerce = ctxt.coerce.as_mut().unwrap();
4697 if let Some(tail_expr_ty) = tail_expr_ty {
4698 let tail_expr = tail_expr.unwrap();
4699 let span = self.get_expr_coercion_span(tail_expr);
4700 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4701 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4703 // Subtle: if there is no explicit tail expression,
4704 // that is typically equivalent to a tail expression
4705 // of `()` -- except if the block diverges. In that
4706 // case, there is no value supplied from the tail
4707 // expression (assuming there are no other breaks,
4708 // this implies that the type of the block will be
4711 // #41425 -- label the implicit `()` as being the
4712 // "found type" here, rather than the "expected type".
4713 if !self.diverges.get().is_always() {
4714 // #50009 -- Do not point at the entire fn block span, point at the return type
4715 // span, as it is the cause of the requirement, and
4716 // `consider_hint_about_removing_semicolon` will point at the last expression
4717 // if it were a relevant part of the error. This improves usability in editors
4718 // that highlight errors inline.
4719 let mut sp = blk.span;
4720 let mut fn_span = None;
4721 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4722 let ret_sp = decl.output.span();
4723 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4724 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4725 // output would otherwise be incorrect and even misleading. Make sure
4726 // the span we're aiming at correspond to a `fn` body.
4727 if block_sp == blk.span {
4729 fn_span = Some(ident.span);
4733 coerce.coerce_forced_unit(
4737 if let Some(expected_ty) = expected.only_has_type(self) {
4738 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4740 if let Some(fn_span) = fn_span {
4743 "implicitly returns `()` as its body has no tail or `return` \
4755 // If we can break from the block, then the block's exit is always reachable
4756 // (... as long as the entry is reachable) - regardless of the tail of the block.
4757 self.diverges.set(prev_diverges);
4760 let mut ty = ctxt.coerce.unwrap().complete(self);
4762 if self.has_errors.get() || ty.references_error() {
4763 ty = self.tcx.types.err
4766 self.write_ty(blk.hir_id, ty);
4768 *self.ps.borrow_mut() = prev;
4772 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4773 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4775 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })
4776 | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(_, body_id), .. }) => {
4777 let body = self.tcx.hir().body(body_id);
4778 if let ExprKind::Block(block, _) = &body.value.kind {
4779 return Some(block.span);
4787 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4788 fn get_parent_fn_decl(
4791 ) -> Option<(&'tcx hir::FnDecl<'tcx>, ast::Ident)> {
4792 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4793 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4796 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4797 fn get_node_fn_decl(
4800 ) -> Option<(&'tcx hir::FnDecl<'tcx>, ast::Ident, bool)> {
4802 Node::Item(&hir::Item { ident, kind: hir::ItemKind::Fn(ref sig, ..), .. }) => {
4803 // This is less than ideal, it will not suggest a return type span on any
4804 // method called `main`, regardless of whether it is actually the entry point,
4805 // but it will still present it as the reason for the expected type.
4806 Some((&sig.decl, ident, ident.name != sym::main))
4808 Node::TraitItem(&hir::TraitItem {
4810 kind: hir::TraitItemKind::Fn(ref sig, ..),
4812 }) => Some((&sig.decl, ident, true)),
4813 Node::ImplItem(&hir::ImplItem {
4815 kind: hir::ImplItemKind::Fn(ref sig, ..),
4817 }) => Some((&sig.decl, ident, false)),
4822 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4823 /// suggestion can be made, `None` otherwise.
4824 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, bool)> {
4825 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4826 // `while` before reaching it, as block tail returns are not available in them.
4827 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4828 let parent = self.tcx.hir().get(blk_id);
4829 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4833 /// On implicit return expressions with mismatched types, provides the following suggestions:
4835 /// - Points out the method's return type as the reason for the expected type.
4836 /// - Possible missing semicolon.
4837 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4838 pub fn suggest_mismatched_types_on_tail(
4840 err: &mut DiagnosticBuilder<'_>,
4841 expr: &'tcx hir::Expr<'tcx>,
4847 let expr = expr.peel_drop_temps();
4848 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4849 let mut pointing_at_return_type = false;
4850 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4851 pointing_at_return_type =
4852 self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest);
4854 pointing_at_return_type
4857 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4858 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4860 /// fn foo(x: usize) -> usize { x }
4861 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4865 err: &mut DiagnosticBuilder<'_>,
4866 expr: &hir::Expr<'_>,
4870 let hir = self.tcx.hir();
4871 let (def_id, sig) = match found.kind {
4872 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4873 ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig()),
4877 let sig = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig).0;
4878 let sig = self.normalize_associated_types_in(expr.span, &sig);
4879 if self.can_coerce(sig.output(), expected) {
4880 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4881 (String::new(), Applicability::MachineApplicable)
4883 ("...".to_string(), Applicability::HasPlaceholders)
4885 let mut msg = "call this function";
4886 match hir.get_if_local(def_id) {
4887 Some(Node::Item(hir::Item { kind: ItemKind::Fn(.., body_id), .. }))
4888 | Some(Node::ImplItem(hir::ImplItem {
4889 kind: hir::ImplItemKind::Fn(_, body_id),
4892 | Some(Node::TraitItem(hir::TraitItem {
4893 kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Provided(body_id)),
4896 let body = hir.body(*body_id);
4900 .map(|param| match ¶m.pat.kind {
4901 hir::PatKind::Binding(_, _, ident, None)
4902 if ident.name != kw::SelfLower =>
4906 _ => "_".to_string(),
4908 .collect::<Vec<_>>()
4911 Some(Node::Expr(hir::Expr {
4912 kind: ExprKind::Closure(_, _, body_id, _, _),
4913 span: full_closure_span,
4916 if *full_closure_span == expr.span {
4919 msg = "call this closure";
4920 let body = hir.body(*body_id);
4924 .map(|param| match ¶m.pat.kind {
4925 hir::PatKind::Binding(_, _, ident, None)
4926 if ident.name != kw::SelfLower =>
4930 _ => "_".to_string(),
4932 .collect::<Vec<_>>()
4935 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4936 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4937 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4938 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4939 msg = "instantiate this tuple variant";
4941 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4942 msg = "instantiate this tuple struct";
4947 Some(Node::ForeignItem(hir::ForeignItem {
4948 kind: hir::ForeignItemKind::Fn(_, idents, _),
4954 if ident.name != kw::SelfLower {
4960 .collect::<Vec<_>>()
4963 Some(Node::TraitItem(hir::TraitItem {
4964 kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Required(idents)),
4970 if ident.name != kw::SelfLower {
4976 .collect::<Vec<_>>()
4981 err.span_suggestion_verbose(
4982 expr.span.shrink_to_hi(),
4983 &format!("use parentheses to {}", msg),
4984 format!("({})", sugg_call),
4992 pub fn suggest_ref_or_into(
4994 err: &mut DiagnosticBuilder<'_>,
4995 expr: &hir::Expr<'_>,
4999 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
5000 err.span_suggestion(sp, msg, suggestion, Applicability::MachineApplicable);
5001 } else if let (ty::FnDef(def_id, ..), true) =
5002 (&found.kind, self.suggest_fn_call(err, expr, expected, found))
5004 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
5005 let sp = self.sess().source_map().guess_head_span(sp);
5006 err.span_label(sp, &format!("{} defined here", found));
5008 } else if !self.check_for_cast(err, expr, found, expected) {
5009 let is_struct_pat_shorthand_field =
5010 self.is_hir_id_from_struct_pattern_shorthand_field(expr.hir_id, expr.span);
5011 let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id);
5012 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
5013 let mut suggestions = iter::repeat(&expr_text)
5014 .zip(methods.iter())
5015 .filter_map(|(receiver, method)| {
5016 let method_call = format!(".{}()", method.ident);
5017 if receiver.ends_with(&method_call) {
5018 None // do not suggest code that is already there (#53348)
5020 let method_call_list = [".to_vec()", ".to_string()"];
5021 let sugg = if receiver.ends_with(".clone()")
5022 && method_call_list.contains(&method_call.as_str())
5024 let max_len = receiver.rfind('.').unwrap();
5025 format!("{}{}", &receiver[..max_len], method_call)
5027 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
5028 format!("({}){}", receiver, method_call)
5030 format!("{}{}", receiver, method_call)
5033 Some(if is_struct_pat_shorthand_field {
5034 format!("{}: {}", receiver, sugg)
5041 if suggestions.peek().is_some() {
5042 err.span_suggestions(
5044 "try using a conversion method",
5046 Applicability::MaybeIncorrect,
5053 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
5054 /// in the heap by calling `Box::new()`.
5055 fn suggest_boxing_when_appropriate(
5057 err: &mut DiagnosticBuilder<'_>,
5058 expr: &hir::Expr<'_>,
5062 if self.tcx.hir().is_const_context(expr.hir_id) {
5063 // Do not suggest `Box::new` in const context.
5066 if !expected.is_box() || found.is_box() {
5069 let boxed_found = self.tcx.mk_box(found);
5070 if let (true, Ok(snippet)) = (
5071 self.can_coerce(boxed_found, expected),
5072 self.sess().source_map().span_to_snippet(expr.span),
5074 err.span_suggestion(
5076 "store this in the heap by calling `Box::new`",
5077 format!("Box::new({})", snippet),
5078 Applicability::MachineApplicable,
5081 "for more on the distinction between the stack and the heap, read \
5082 https://doc.rust-lang.org/book/ch15-01-box.html, \
5083 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
5084 https://doc.rust-lang.org/std/boxed/index.html",
5089 /// When encountering an `impl Future` where `BoxFuture` is expected, suggest `Box::pin`.
5090 fn suggest_calling_boxed_future_when_appropriate(
5092 err: &mut DiagnosticBuilder<'_>,
5093 expr: &hir::Expr<'_>,
5099 if self.tcx.hir().is_const_context(expr.hir_id) {
5100 // Do not suggest `Box::new` in const context.
5103 let pin_did = self.tcx.lang_items().pin_type();
5104 match expected.kind {
5105 ty::Adt(def, _) if Some(def.did) != pin_did => return false,
5106 // This guards the `unwrap` and `mk_box` below.
5107 _ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return false,
5110 let boxed_found = self.tcx.mk_box(found);
5111 let new_found = self.tcx.mk_lang_item(boxed_found, lang_items::PinTypeLangItem).unwrap();
5112 if let (true, Ok(snippet)) = (
5113 self.can_coerce(new_found, expected),
5114 self.sess().source_map().span_to_snippet(expr.span),
5117 ty::Adt(def, _) if def.is_box() => {
5118 err.help("use `Box::pin`");
5121 err.span_suggestion(
5123 "you need to pin and box this expression",
5124 format!("Box::pin({})", snippet),
5125 Applicability::MachineApplicable,
5135 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
5139 /// bar_that_returns_u32()
5143 /// This routine checks if the return expression in a block would make sense on its own as a
5144 /// statement and the return type has been left as default or has been specified as `()`. If so,
5145 /// it suggests adding a semicolon.
5146 fn suggest_missing_semicolon(
5148 err: &mut DiagnosticBuilder<'_>,
5149 expression: &'tcx hir::Expr<'tcx>,
5153 if expected.is_unit() {
5154 // `BlockTailExpression` only relevant if the tail expr would be
5155 // useful on its own.
5156 match expression.kind {
5158 | ExprKind::MethodCall(..)
5159 | ExprKind::Loop(..)
5160 | ExprKind::Match(..)
5161 | ExprKind::Block(..) => {
5162 err.span_suggestion(
5163 cause_span.shrink_to_hi(),
5164 "try adding a semicolon",
5166 Applicability::MachineApplicable,
5174 /// A possible error is to forget to add a return type that is needed:
5178 /// bar_that_returns_u32()
5182 /// This routine checks if the return type is left as default, the method is not part of an
5183 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
5185 fn suggest_missing_return_type(
5187 err: &mut DiagnosticBuilder<'_>,
5188 fn_decl: &hir::FnDecl<'_>,
5193 // Only suggest changing the return type for methods that
5194 // haven't set a return type at all (and aren't `fn main()` or an impl).
5195 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
5196 (&hir::FnRetTy::DefaultReturn(span), true, true, true) => {
5197 err.span_suggestion(
5199 "try adding a return type",
5200 format!("-> {} ", self.resolve_vars_with_obligations(found)),
5201 Applicability::MachineApplicable,
5205 (&hir::FnRetTy::DefaultReturn(span), false, true, true) => {
5206 err.span_label(span, "possibly return type missing here?");
5209 (&hir::FnRetTy::DefaultReturn(span), _, false, true) => {
5210 // `fn main()` must return `()`, do not suggest changing return type
5211 err.span_label(span, "expected `()` because of default return type");
5214 // expectation was caused by something else, not the default return
5215 (&hir::FnRetTy::DefaultReturn(_), _, _, false) => false,
5216 (&hir::FnRetTy::Return(ref ty), _, _, _) => {
5217 // Only point to return type if the expected type is the return type, as if they
5218 // are not, the expectation must have been caused by something else.
5219 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
5221 let ty = AstConv::ast_ty_to_ty(self, ty);
5222 debug!("suggest_missing_return_type: return type {:?}", ty);
5223 debug!("suggest_missing_return_type: expected type {:?}", ty);
5224 if ty.kind == expected.kind {
5225 err.span_label(sp, format!("expected `{}` because of return type", expected));
5233 /// A possible error is to forget to add `.await` when using futures:
5236 /// async fn make_u32() -> u32 {
5240 /// fn take_u32(x: u32) {}
5242 /// async fn foo() {
5243 /// let x = make_u32();
5248 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
5249 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
5250 /// `.await` to the tail of the expression.
5251 fn suggest_missing_await(
5253 err: &mut DiagnosticBuilder<'_>,
5254 expr: &hir::Expr<'_>,
5258 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
5259 // body isn't `async`.
5260 let item_id = self.tcx().hir().get_parent_node(self.body_id);
5261 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
5262 let body = self.tcx().hir().body(body_id);
5263 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
5265 // Check for `Future` implementations by constructing a predicate to
5266 // prove: `<T as Future>::Output == U`
5267 let future_trait = self.tcx.lang_items().future_trait().unwrap();
5268 let item_def_id = self
5270 .associated_items(future_trait)
5271 .in_definition_order()
5276 ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
5277 // `<T as Future>::Output`
5278 projection_ty: ty::ProjectionTy {
5280 substs: self.tcx.mk_substs_trait(
5282 self.fresh_substs_for_item(sp, item_def_id),
5289 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
5290 debug!("suggest_missing_await: trying obligation {:?}", obligation);
5291 if self.infcx.predicate_may_hold(&obligation) {
5292 debug!("suggest_missing_await: obligation held: {:?}", obligation);
5293 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
5294 err.span_suggestion(
5296 "consider using `.await` here",
5297 format!("{}.await", code),
5298 Applicability::MaybeIncorrect,
5301 debug!("suggest_missing_await: no snippet for {:?}", sp);
5304 debug!("suggest_missing_await: obligation did not hold: {:?}", obligation)
5310 /// A common error is to add an extra semicolon:
5313 /// fn foo() -> usize {
5318 /// This routine checks if the final statement in a block is an
5319 /// expression with an explicit semicolon whose type is compatible
5320 /// with `expected_ty`. If so, it suggests removing the semicolon.
5321 fn consider_hint_about_removing_semicolon(
5323 blk: &'tcx hir::Block<'tcx>,
5324 expected_ty: Ty<'tcx>,
5325 err: &mut DiagnosticBuilder<'_>,
5327 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
5328 err.span_suggestion(
5330 "consider removing this semicolon",
5332 Applicability::MachineApplicable,
5337 fn could_remove_semicolon(
5339 blk: &'tcx hir::Block<'tcx>,
5340 expected_ty: Ty<'tcx>,
5342 // Be helpful when the user wrote `{... expr;}` and
5343 // taking the `;` off is enough to fix the error.
5344 let last_stmt = blk.stmts.last()?;
5345 let last_expr = match last_stmt.kind {
5346 hir::StmtKind::Semi(ref e) => e,
5349 let last_expr_ty = self.node_ty(last_expr.hir_id);
5350 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
5353 let original_span = original_sp(last_stmt.span, blk.span);
5354 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
5357 // Instantiates the given path, which must refer to an item with the given
5358 // number of type parameters and type.
5359 pub fn instantiate_value_path(
5361 segments: &[hir::PathSegment<'_>],
5362 self_ty: Option<Ty<'tcx>>,
5366 ) -> (Ty<'tcx>, Res) {
5368 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
5369 segments, self_ty, res, hir_id,
5374 let path_segs = match res {
5375 Res::Local(_) | Res::SelfCtor(_) => vec![],
5376 Res::Def(kind, def_id) => {
5377 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id)
5379 _ => bug!("instantiate_value_path on {:?}", res),
5382 let mut user_self_ty = None;
5383 let mut is_alias_variant_ctor = false;
5385 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
5386 if let Some(self_ty) = self_ty {
5387 let adt_def = self_ty.ty_adt_def().unwrap();
5388 user_self_ty = Some(UserSelfTy { impl_def_id: adt_def.did, self_ty });
5389 is_alias_variant_ctor = true;
5392 Res::Def(DefKind::AssocFn, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
5393 let container = tcx.associated_item(def_id).container;
5394 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
5396 ty::TraitContainer(trait_did) => {
5397 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
5399 ty::ImplContainer(impl_def_id) => {
5400 if segments.len() == 1 {
5401 // `<T>::assoc` will end up here, and so
5402 // can `T::assoc`. It this came from an
5403 // inherent impl, we need to record the
5404 // `T` for posterity (see `UserSelfTy` for
5406 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
5407 user_self_ty = Some(UserSelfTy { impl_def_id, self_ty });
5415 // Now that we have categorized what space the parameters for each
5416 // segment belong to, let's sort out the parameters that the user
5417 // provided (if any) into their appropriate spaces. We'll also report
5418 // errors if type parameters are provided in an inappropriate place.
5420 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
5421 let generics_has_err = AstConv::prohibit_generics(
5423 segments.iter().enumerate().filter_map(|(index, seg)| {
5424 if !generic_segs.contains(&index) || is_alias_variant_ctor {
5432 if let Res::Local(hid) = res {
5433 let ty = self.local_ty(span, hid).decl_ty;
5434 let ty = self.normalize_associated_types_in(span, &ty);
5435 self.write_ty(hir_id, ty);
5439 if generics_has_err {
5440 // Don't try to infer type parameters when prohibited generic arguments were given.
5441 user_self_ty = None;
5444 // Now we have to compare the types that the user *actually*
5445 // provided against the types that were *expected*. If the user
5446 // did not provide any types, then we want to substitute inference
5447 // variables. If the user provided some types, we may still need
5448 // to add defaults. If the user provided *too many* types, that's
5451 let mut infer_args_for_err = FxHashSet::default();
5452 for &PathSeg(def_id, index) in &path_segs {
5453 let seg = &segments[index];
5454 let generics = tcx.generics_of(def_id);
5455 // Argument-position `impl Trait` is treated as a normal generic
5456 // parameter internally, but we don't allow users to specify the
5457 // parameter's value explicitly, so we have to do some error-
5459 if let Err(GenericArgCountMismatch { reported: Some(ErrorReported), .. }) =
5460 AstConv::check_generic_arg_count_for_call(
5461 tcx, span, &generics, &seg, false, // `is_method_call`
5464 infer_args_for_err.insert(index);
5465 self.set_tainted_by_errors(); // See issue #53251.
5469 let has_self = path_segs
5471 .map(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self)
5474 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
5475 let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id));
5477 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
5478 let variant = adt_def.non_enum_variant();
5479 let ctor_def_id = variant.ctor_def_id.unwrap();
5481 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
5486 let mut err = tcx.sess.struct_span_err(
5488 "the `Self` constructor can only be used with tuple or unit structs",
5490 if let Some(adt_def) = ty.ty_adt_def() {
5491 match adt_def.adt_kind() {
5493 err.help("did you mean to use one of the enum's variants?");
5495 AdtKind::Struct | AdtKind::Union => {
5496 err.span_suggestion(
5498 "use curly brackets",
5499 String::from("Self { /* fields */ }"),
5500 Applicability::HasPlaceholders,
5507 return (tcx.types.err, res);
5513 let def_id = res.def_id();
5515 // The things we are substituting into the type should not contain
5516 // escaping late-bound regions, and nor should the base type scheme.
5517 let ty = tcx.type_of(def_id);
5519 let substs = self_ctor_substs.unwrap_or_else(|| {
5520 AstConv::create_substs_for_generic_args(
5526 infer_args_for_err.is_empty(),
5527 // Provide the generic args, and whether types should be inferred.
5529 if let Some(&PathSeg(_, index)) =
5530 path_segs.iter().find(|&PathSeg(did, _)| *did == def_id)
5532 // If we've encountered an `impl Trait`-related error, we're just
5533 // going to infer the arguments for better error messages.
5534 if !infer_args_for_err.contains(&index) {
5535 // Check whether the user has provided generic arguments.
5536 if let Some(ref data) = segments[index].args {
5537 return (Some(data), segments[index].infer_args);
5540 return (None, segments[index].infer_args);
5545 // Provide substitutions for parameters for which (valid) arguments have been provided.
5546 |param, arg| match (¶m.kind, arg) {
5547 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
5548 AstConv::ast_region_to_region(self, lt, Some(param)).into()
5550 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
5551 self.to_ty(ty).into()
5553 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
5554 self.to_const(&ct.value).into()
5556 _ => unreachable!(),
5558 // Provide substitutions for parameters for which arguments are inferred.
5559 |substs, param, infer_args| {
5561 GenericParamDefKind::Lifetime => {
5562 self.re_infer(Some(param), span).unwrap().into()
5564 GenericParamDefKind::Type { has_default, .. } => {
5565 if !infer_args && has_default {
5566 // If we have a default, then we it doesn't matter that we're not
5567 // inferring the type arguments: we provide the default where any
5569 let default = tcx.type_of(param.def_id);
5572 default.subst_spanned(tcx, substs.unwrap(), Some(span)),
5576 // If no type arguments were provided, we have to infer them.
5577 // This case also occurs as a result of some malformed input, e.g.
5578 // a lifetime argument being given instead of a type parameter.
5579 // Using inference instead of `Error` gives better error messages.
5580 self.var_for_def(span, param)
5583 GenericParamDefKind::Const => {
5584 // FIXME(const_generics:defaults)
5585 // No const parameters were provided, we have to infer them.
5586 self.var_for_def(span, param)
5592 assert!(!substs.has_escaping_bound_vars());
5593 assert!(!ty.has_escaping_bound_vars());
5595 // First, store the "user substs" for later.
5596 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
5598 self.add_required_obligations(span, def_id, &substs);
5600 // Substitute the values for the type parameters into the type of
5601 // the referenced item.
5602 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
5604 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
5605 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
5606 // is inherent, there is no `Self` parameter; instead, the impl needs
5607 // type parameters, which we can infer by unifying the provided `Self`
5608 // with the substituted impl type.
5609 // This also occurs for an enum variant on a type alias.
5610 let ty = tcx.type_of(impl_def_id);
5612 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
5613 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
5614 Ok(ok) => self.register_infer_ok_obligations(ok),
5616 self.tcx.sess.delay_span_bug(
5619 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
5628 self.check_rustc_args_require_const(def_id, hir_id, span);
5630 debug!("instantiate_value_path: type of {:?} is {:?}", hir_id, ty_substituted);
5631 self.write_substs(hir_id, substs);
5633 (ty_substituted, res)
5636 /// Add all the obligations that are required, substituting and normalized appropriately.
5637 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
5638 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
5640 for (i, mut obligation) in traits::predicates_for_generics(
5641 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
5648 // This makes the error point at the bound, but we want to point at the argument
5649 if let Some(span) = spans.get(i) {
5650 obligation.cause.code = traits::BindingObligation(def_id, *span);
5652 self.register_predicate(obligation);
5656 fn check_rustc_args_require_const(&self, def_id: DefId, hir_id: hir::HirId, span: Span) {
5657 // We're only interested in functions tagged with
5658 // #[rustc_args_required_const], so ignore anything that's not.
5659 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5663 // If our calling expression is indeed the function itself, we're good!
5664 // If not, generate an error that this can only be called directly.
5665 if let Node::Expr(expr) = self.tcx.hir().get(self.tcx.hir().get_parent_node(hir_id)) {
5666 if let ExprKind::Call(ref callee, ..) = expr.kind {
5667 if callee.hir_id == hir_id {
5673 self.tcx.sess.span_err(
5675 "this function can only be invoked directly, not through a function pointer",
5679 /// Resolves `typ` by a single level if `typ` is a type variable.
5680 /// If no resolution is possible, then an error is reported.
5681 /// Numeric inference variables may be left unresolved.
5682 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5683 let ty = self.resolve_vars_with_obligations(ty);
5684 if !ty.is_ty_var() {
5687 if !self.is_tainted_by_errors() {
5688 self.need_type_info_err((**self).body_id, sp, ty, E0282)
5689 .note("type must be known at this point")
5692 self.demand_suptype(sp, self.tcx.types.err, ty);
5697 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5700 ctxt: BreakableCtxt<'tcx>,
5702 ) -> (BreakableCtxt<'tcx>, R) {
5705 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5706 index = enclosing_breakables.stack.len();
5707 enclosing_breakables.by_id.insert(id, index);
5708 enclosing_breakables.stack.push(ctxt);
5712 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5713 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5714 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5715 enclosing_breakables.stack.pop().expect("missing breakable context")
5720 /// Instantiate a QueryResponse in a probe context, without a
5721 /// good ObligationCause.
5722 fn probe_instantiate_query_response(
5725 original_values: &OriginalQueryValues<'tcx>,
5726 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5727 ) -> InferResult<'tcx, Ty<'tcx>> {
5728 self.instantiate_query_response_and_region_obligations(
5729 &traits::ObligationCause::misc(span, self.body_id),
5736 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5737 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5738 let mut contained_in_place = false;
5740 while let hir::Node::Expr(parent_expr) =
5741 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5743 match &parent_expr.kind {
5744 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5745 if lhs.hir_id == expr_id {
5746 contained_in_place = true;
5752 expr_id = parent_expr.hir_id;
5759 fn check_type_params_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5760 debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty);
5762 assert_eq!(generics.parent, None);
5764 if generics.own_counts().types == 0 {
5768 let mut params_used = BitSet::new_empty(generics.params.len());
5770 if ty.references_error() {
5771 // If there is already another error, do not emit
5772 // an error for not using a type parameter.
5773 assert!(tcx.sess.has_errors());
5777 for leaf in ty.walk() {
5778 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
5779 if let ty::Param(param) = leaf_ty.kind {
5780 debug!("found use of ty param {:?}", param);
5781 params_used.insert(param.index);
5786 for param in &generics.params {
5787 if !params_used.contains(param.index) {
5788 if let ty::GenericParamDefKind::Type { .. } = param.kind {
5789 let span = tcx.def_span(param.def_id);
5794 "type parameter `{}` is unused",
5797 .span_label(span, "unused type parameter")
5804 fn fatally_break_rust(sess: &Session) {
5805 let handler = sess.diagnostic();
5806 handler.span_bug_no_panic(
5808 "It looks like you're trying to break rust; would you like some ICE?",
5810 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5811 handler.note_without_error(
5812 "we would appreciate a joke overview: \
5813 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
5815 handler.note_without_error(&format!(
5816 "rustc {} running on {}",
5817 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5818 config::host_triple(),
5822 fn potentially_plural_count(count: usize, word: &str) -> String {
5823 format!("{} {}{}", count, word, pluralize!(count))