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<'_>,
2254 assoc: &ty::AssocItem,
2261 Some(match ty.kind {
2262 ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
2263 ty::Ref(reg, _ref_ty, mutability) => {
2264 let reg = match &format!("{}", reg)[..] {
2265 "'_" | "" => String::new(),
2266 reg => format!("{} ", reg),
2268 if assoc.fn_has_self_parameter && i == 0 {
2269 format!("&{}{}self", reg, mutability.prefix_str())
2271 format!("_: {:?}", ty)
2275 if assoc.fn_has_self_parameter && i == 0 {
2276 format!("self: {:?}", ty)
2278 format!("_: {:?}", ty)
2283 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
2284 .filter_map(|arg| arg)
2285 .collect::<Vec<String>>()
2287 let output = sig.output();
2288 let output = if !output.is_unit() { format!(" -> {:?}", output) } else { String::new() };
2290 let unsafety = sig.unsafety.prefix_str();
2291 let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
2293 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
2294 // not be present in the `fn` definition, not will we account for renamed
2295 // lifetimes between the `impl` and the `trait`, but this should be good enough to
2296 // fill in a significant portion of the missing code, and other subsequent
2297 // suggestions can help the user fix the code.
2299 "{}fn {}{}({}){}{} {{ todo!() }}",
2300 unsafety, ident, generics, args, output, where_clauses
2304 /// Return placeholder code for the given associated item.
2305 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
2306 /// structured suggestion.
2307 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
2309 ty::AssocKind::Fn => {
2310 // We skip the binder here because the binder would deanonymize all
2311 // late-bound regions, and we don't want method signatures to show up
2312 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
2313 // regions just fine, showing `fn(&MyType)`.
2316 tcx.fn_sig(assoc.def_id).skip_binder(),
2318 tcx.predicates_of(assoc.def_id),
2322 ty::AssocKind::Type => format!("type {} = Type;", assoc.ident),
2323 // FIXME(type_alias_impl_trait): we should print bounds here too.
2324 ty::AssocKind::OpaqueTy => format!("type {} = Type;", assoc.ident),
2325 ty::AssocKind::Const => {
2326 let ty = tcx.type_of(assoc.def_id);
2327 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
2328 format!("const {}: {:?} = {};", assoc.ident, ty, val)
2333 /// Checks whether a type can be represented in memory. In particular, it
2334 /// identifies types that contain themselves without indirection through a
2335 /// pointer, which would mean their size is unbounded.
2336 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
2337 let rty = tcx.type_of(item_def_id);
2339 // Check that it is possible to represent this type. This call identifies
2340 // (1) types that contain themselves and (2) types that contain a different
2341 // recursive type. It is only necessary to throw an error on those that
2342 // contain themselves. For case 2, there must be an inner type that will be
2343 // caught by case 1.
2344 match rty.is_representable(tcx, sp) {
2345 Representability::SelfRecursive(spans) => {
2346 let mut err = recursive_type_with_infinite_size_error(tcx, item_def_id);
2348 err.span_label(span, "recursive without indirection");
2353 Representability::Representable | Representability::ContainsRecursive => (),
2358 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2359 let t = tcx.type_of(def_id);
2360 if let ty::Adt(def, substs) = t.kind {
2361 if def.is_struct() {
2362 let fields = &def.non_enum_variant().fields;
2363 if fields.is_empty() {
2364 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
2367 let e = fields[0].ty(tcx, substs);
2368 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
2369 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
2370 .span_label(sp, "SIMD elements must have the same type")
2375 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
2376 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
2382 "SIMD vector element type should be machine type"
2392 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2393 let repr = tcx.adt_def(def_id).repr;
2395 for attr in tcx.get_attrs(def_id).iter() {
2396 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
2397 if let attr::ReprPacked(pack) = r {
2398 if let Some(repr_pack) = repr.pack {
2399 if pack as u64 != repr_pack.bytes() {
2404 "type has conflicting packed representation hints"
2412 if repr.align.is_some() {
2417 "type has conflicting packed and align representation hints"
2421 if let Some(def_spans) = check_packed_inner(tcx, def_id, &mut vec![]) {
2422 let mut err = struct_span_err!(
2426 "packed type cannot transitively contain a `#[repr(align)]` type"
2429 let hir = tcx.hir();
2430 if let Some(hir_id) = hir.as_local_hir_id(def_spans[0].0) {
2431 if let Node::Item(Item { ident, .. }) = hir.get(hir_id) {
2433 tcx.def_span(def_spans[0].0),
2434 &format!("`{}` has a `#[repr(align)]` attribute", ident),
2439 if def_spans.len() > 2 {
2440 let mut first = true;
2441 for (adt_def, span) in def_spans.iter().skip(1).rev() {
2442 if let Some(hir_id) = hir.as_local_hir_id(*adt_def) {
2443 if let Node::Item(Item { ident, .. }) = hir.get(hir_id) {
2448 "`{}` contains a field of type `{}`",
2449 tcx.type_of(def_id),
2453 format!("...which contains a field of type `{}`", ident)
2468 fn check_packed_inner(
2471 stack: &mut Vec<DefId>,
2472 ) -> Option<Vec<(DefId, Span)>> {
2473 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind {
2474 if def.is_struct() || def.is_union() {
2475 if def.repr.align.is_some() {
2476 return Some(vec![(def.did, DUMMY_SP)]);
2480 for field in &def.non_enum_variant().fields {
2481 if let ty::Adt(def, _) = field.ty(tcx, substs).kind {
2482 if !stack.contains(&def.did) {
2483 if let Some(mut defs) = check_packed_inner(tcx, def.did, stack) {
2484 defs.push((def.did, field.ident.span));
2497 /// Emit an error when encountering more or less than one variant in a transparent enum.
2498 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2499 let variant_spans: Vec<_> = adt
2502 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
2504 let msg = format!("needs exactly one variant, but has {}", adt.variants.len(),);
2505 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2506 err.span_label(sp, &msg);
2507 if let [start @ .., end] = &*variant_spans {
2508 for variant_span in start {
2509 err.span_label(*variant_span, "");
2511 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2516 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2518 fn bad_non_zero_sized_fields<'tcx>(
2520 adt: &'tcx ty::AdtDef,
2522 field_spans: impl Iterator<Item = Span>,
2525 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2526 let mut err = struct_span_err!(
2530 "{}transparent {} {}",
2531 if adt.is_enum() { "the variant of a " } else { "" },
2535 err.span_label(sp, &msg);
2536 for sp in field_spans {
2537 err.span_label(sp, "this field is non-zero-sized");
2542 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2543 let adt = tcx.adt_def(def_id);
2544 if !adt.repr.transparent() {
2547 let sp = tcx.sess.source_map().guess_head_span(sp);
2549 if adt.is_union() && !tcx.features().transparent_unions {
2551 &tcx.sess.parse_sess,
2552 sym::transparent_unions,
2554 "transparent unions are unstable",
2559 if adt.variants.len() != 1 {
2560 bad_variant_count(tcx, adt, sp, def_id);
2561 if adt.variants.is_empty() {
2562 // Don't bother checking the fields. No variants (and thus no fields) exist.
2567 // For each field, figure out if it's known to be a ZST and align(1)
2568 let field_infos = adt.all_fields().map(|field| {
2569 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2570 let param_env = tcx.param_env(field.did);
2571 let layout = tcx.layout_of(param_env.and(ty));
2572 // We are currently checking the type this field came from, so it must be local
2573 let span = tcx.hir().span_if_local(field.did).unwrap();
2574 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2575 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2579 let non_zst_fields =
2580 field_infos.clone().filter_map(|(span, zst, _align1)| if !zst { Some(span) } else { None });
2581 let non_zst_count = non_zst_fields.clone().count();
2582 if non_zst_count != 1 {
2583 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2585 for (span, zst, align1) in field_infos {
2591 "zero-sized field in transparent {} has alignment larger than 1",
2594 .span_label(span, "has alignment larger than 1")
2600 #[allow(trivial_numeric_casts)]
2601 pub fn check_enum<'tcx>(
2604 vs: &'tcx [hir::Variant<'tcx>],
2607 let def_id = tcx.hir().local_def_id(id);
2608 let def = tcx.adt_def(def_id);
2609 def.destructor(tcx); // force the destructor to be evaluated
2612 let attributes = tcx.get_attrs(def_id);
2613 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2618 "unsupported representation for zero-variant enum"
2620 .span_label(sp, "zero-variant enum")
2625 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2626 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2627 if !tcx.features().repr128 {
2629 &tcx.sess.parse_sess,
2632 "repr with 128-bit type is unstable",
2639 if let Some(ref e) = v.disr_expr {
2640 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2644 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2645 let is_unit = |var: &hir::Variant<'_>| match var.data {
2646 hir::VariantData::Unit(..) => true,
2650 let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();
2651 let has_non_units = vs.iter().any(|var| !is_unit(var));
2652 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2653 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2655 if disr_non_unit || (disr_units && has_non_units) {
2657 struct_span_err!(tcx.sess, sp, E0732, "`#[repr(inttype)]` must be specified");
2662 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2663 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2664 // Check for duplicate discriminant values
2665 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2666 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2667 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2668 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2669 let i_span = match variant_i.disr_expr {
2670 Some(ref expr) => tcx.hir().span(expr.hir_id),
2671 None => tcx.hir().span(variant_i_hir_id),
2673 let span = match v.disr_expr {
2674 Some(ref expr) => tcx.hir().span(expr.hir_id),
2681 "discriminant value `{}` already exists",
2684 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2685 .span_label(span, format!("enum already has `{}`", disr_vals[i]))
2688 disr_vals.push(discr);
2691 check_representable(tcx, sp, def_id);
2692 check_transparent(tcx, sp, def_id);
2695 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span) {
2700 "expected unit struct, unit variant or constant, found {}{}",
2702 tcx.sess.source_map().span_to_snippet(span).map_or(String::new(), |s| format!(" `{}`", s)),
2707 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2708 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2712 fn item_def_id(&self) -> Option<DefId> {
2716 fn default_constness_for_trait_bounds(&self) -> hir::Constness {
2717 // FIXME: refactor this into a method
2718 let node = self.tcx.hir().get(self.body_id);
2719 if let Some(fn_like) = FnLikeNode::from_node(node) {
2722 hir::Constness::NotConst
2726 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2728 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2729 let item_id = tcx.hir().ty_param_owner(hir_id);
2730 let item_def_id = tcx.hir().local_def_id(item_id);
2731 let generics = tcx.generics_of(item_def_id);
2732 let index = generics.param_def_id_to_index[&def_id];
2733 ty::GenericPredicates {
2735 predicates: tcx.arena.alloc_from_iter(self.param_env.caller_bounds.iter().filter_map(
2736 |&predicate| match predicate {
2737 ty::Predicate::Trait(ref data, _)
2738 if data.skip_binder().self_ty().is_param(index) =>
2740 // HACK(eddyb) should get the original `Span`.
2741 let span = tcx.def_span(def_id);
2742 Some((predicate, span))
2750 fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
2752 Some(def) => infer::EarlyBoundRegion(span, def.name),
2753 None => infer::MiscVariable(span),
2755 Some(self.next_region_var(v))
2758 fn allow_ty_infer(&self) -> bool {
2762 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2763 if let Some(param) = param {
2764 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2769 self.next_ty_var(TypeVariableOrigin {
2770 kind: TypeVariableOriginKind::TypeInference,
2779 param: Option<&ty::GenericParamDef>,
2781 ) -> &'tcx Const<'tcx> {
2782 if let Some(param) = param {
2783 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2788 self.next_const_var(
2790 ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
2795 fn projected_ty_from_poly_trait_ref(
2799 item_segment: &hir::PathSegment<'_>,
2800 poly_trait_ref: ty::PolyTraitRef<'tcx>,
2802 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2804 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2808 let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
2817 self.tcx().mk_projection(item_def_id, item_substs)
2820 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2821 if ty.has_escaping_bound_vars() {
2822 ty // FIXME: normalization and escaping regions
2824 self.normalize_associated_types_in(span, &ty)
2828 fn set_tainted_by_errors(&self) {
2829 self.infcx.set_tainted_by_errors()
2832 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2833 self.write_ty(hir_id, ty)
2837 /// Controls whether the arguments are tupled. This is used for the call
2840 /// Tupling means that all call-side arguments are packed into a tuple and
2841 /// passed as a single parameter. For example, if tupling is enabled, this
2844 /// fn f(x: (isize, isize))
2846 /// Can be called as:
2853 #[derive(Clone, Eq, PartialEq)]
2854 enum TupleArgumentsFlag {
2859 /// Controls how we perform fallback for unconstrained
2862 /// Do not fallback type variables to opaque types.
2864 /// Perform all possible kinds of fallback, including
2865 /// turning type variables to opaque types.
2869 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2871 inh: &'a Inherited<'a, 'tcx>,
2872 param_env: ty::ParamEnv<'tcx>,
2873 body_id: hir::HirId,
2874 ) -> FnCtxt<'a, 'tcx> {
2878 err_count_on_creation: inh.tcx.sess.err_count(),
2880 ret_coercion_span: RefCell::new(None),
2881 resume_yield_tys: None,
2882 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
2883 diverges: Cell::new(Diverges::Maybe),
2884 has_errors: Cell::new(false),
2885 enclosing_breakables: RefCell::new(EnclosingBreakables {
2887 by_id: Default::default(),
2893 pub fn sess(&self) -> &Session {
2897 pub fn errors_reported_since_creation(&self) -> bool {
2898 self.tcx.sess.err_count() > self.err_count_on_creation
2901 /// Produces warning on the given node, if the current point in the
2902 /// function is unreachable, and there hasn't been another warning.
2903 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2904 // FIXME: Combine these two 'if' expressions into one once
2905 // let chains are implemented
2906 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2907 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2908 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2909 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2910 if !span.is_desugaring(DesugaringKind::CondTemporary)
2911 && !span.is_desugaring(DesugaringKind::Async)
2912 && !orig_span.is_desugaring(DesugaringKind::Await)
2914 self.diverges.set(Diverges::WarnedAlways);
2916 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2918 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, |lint| {
2919 let msg = format!("unreachable {}", kind);
2921 .span_label(span, &msg)
2925 .unwrap_or("any code following this expression is unreachable"),
2933 pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
2934 ObligationCause::new(span, self.body_id, code)
2937 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2938 self.cause(span, ObligationCauseCode::MiscObligation)
2941 /// Resolves type and const variables in `ty` if possible. Unlike the infcx
2942 /// version (resolve_vars_if_possible), this version will
2943 /// also select obligations if it seems useful, in an effort
2944 /// to get more type information.
2945 fn resolve_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2946 debug!("resolve_vars_with_obligations(ty={:?})", ty);
2948 // No Infer()? Nothing needs doing.
2949 if !ty.has_infer_types_or_consts() {
2950 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2954 // If `ty` is a type variable, see whether we already know what it is.
2955 ty = self.resolve_vars_if_possible(&ty);
2956 if !ty.has_infer_types_or_consts() {
2957 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2961 // If not, try resolving pending obligations as much as
2962 // possible. This can help substantially when there are
2963 // indirect dependencies that don't seem worth tracking
2965 self.select_obligations_where_possible(false, |_| {});
2966 ty = self.resolve_vars_if_possible(&ty);
2968 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2972 fn record_deferred_call_resolution(
2974 closure_def_id: DefId,
2975 r: DeferredCallResolution<'tcx>,
2977 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2978 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2981 fn remove_deferred_call_resolutions(
2983 closure_def_id: DefId,
2984 ) -> Vec<DeferredCallResolution<'tcx>> {
2985 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2986 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2989 pub fn tag(&self) -> String {
2990 format!("{:p}", self)
2993 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
2994 self.locals.borrow().get(&nid).cloned().unwrap_or_else(|| {
2995 span_bug!(span, "no type for local variable {}", self.tcx.hir().node_to_string(nid))
3000 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
3002 "write_ty({:?}, {:?}) in fcx {}",
3004 self.resolve_vars_if_possible(&ty),
3007 self.tables.borrow_mut().node_types_mut().insert(id, ty);
3009 if ty.references_error() {
3010 self.has_errors.set(true);
3011 self.set_tainted_by_errors();
3015 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
3016 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
3019 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
3020 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
3023 pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
3024 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
3025 self.write_resolution(hir_id, Ok((DefKind::AssocFn, method.def_id)));
3026 self.write_substs(hir_id, method.substs);
3028 // When the method is confirmed, the `method.substs` includes
3029 // parameters from not just the method, but also the impl of
3030 // the method -- in particular, the `Self` type will be fully
3031 // resolved. However, those are not something that the "user
3032 // specified" -- i.e., those types come from the inferred type
3033 // of the receiver, not something the user wrote. So when we
3034 // create the user-substs, we want to replace those earlier
3035 // types with just the types that the user actually wrote --
3036 // that is, those that appear on the *method itself*.
3038 // As an example, if the user wrote something like
3039 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
3040 // type of `foo` (possibly adjusted), but we don't want to
3041 // include that. We want just the `[_, u32]` part.
3042 if !method.substs.is_noop() {
3043 let method_generics = self.tcx.generics_of(method.def_id);
3044 if !method_generics.params.is_empty() {
3045 let user_type_annotation = self.infcx.probe(|_| {
3046 let user_substs = UserSubsts {
3047 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
3048 let i = param.index as usize;
3049 if i < method_generics.parent_count {
3050 self.infcx.var_for_def(DUMMY_SP, param)
3055 user_self_ty: None, // not relevant here
3058 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
3064 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
3065 self.write_user_type_annotation(hir_id, user_type_annotation);
3070 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
3071 if !substs.is_noop() {
3072 debug!("write_substs({:?}, {:?}) in fcx {}", node_id, substs, self.tag());
3074 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
3078 /// Given the substs that we just converted from the HIR, try to
3079 /// canonicalize them and store them as user-given substitutions
3080 /// (i.e., substitutions that must be respected by the NLL check).
3082 /// This should be invoked **before any unifications have
3083 /// occurred**, so that annotations like `Vec<_>` are preserved
3085 pub fn write_user_type_annotation_from_substs(
3089 substs: SubstsRef<'tcx>,
3090 user_self_ty: Option<UserSelfTy<'tcx>>,
3093 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
3094 user_self_ty={:?} in fcx {}",
3102 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
3103 let canonicalized = self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
3105 UserSubsts { substs, user_self_ty },
3107 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
3108 self.write_user_type_annotation(hir_id, canonicalized);
3112 pub fn write_user_type_annotation(
3115 canonical_user_type_annotation: CanonicalUserType<'tcx>,
3118 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
3120 canonical_user_type_annotation,
3124 if !canonical_user_type_annotation.is_identity() {
3127 .user_provided_types_mut()
3128 .insert(hir_id, canonical_user_type_annotation);
3130 debug!("write_user_type_annotation: skipping identity substs");
3134 pub fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment<'tcx>>) {
3135 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
3141 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
3142 Entry::Vacant(entry) => {
3145 Entry::Occupied(mut entry) => {
3146 debug!(" - composing on top of {:?}", entry.get());
3147 match (&entry.get()[..], &adj[..]) {
3148 // Applying any adjustment on top of a NeverToAny
3149 // is a valid NeverToAny adjustment, because it can't
3151 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
3153 Adjustment { kind: Adjust::Deref(_), .. },
3154 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
3156 Adjustment { kind: Adjust::Deref(_), .. },
3157 .. // Any following adjustments are allowed.
3159 // A reborrow has no effect before a dereference.
3161 // FIXME: currently we never try to compose autoderefs
3162 // and ReifyFnPointer/UnsafeFnPointer, but we could.
3164 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
3165 expr, entry.get(), adj)
3167 *entry.get_mut() = adj;
3172 /// Basically whenever we are converting from a type scheme into
3173 /// the fn body space, we always want to normalize associated
3174 /// types as well. This function combines the two.
3175 fn instantiate_type_scheme<T>(&self, span: Span, substs: SubstsRef<'tcx>, value: &T) -> T
3177 T: TypeFoldable<'tcx>,
3179 let value = value.subst(self.tcx, substs);
3180 let result = self.normalize_associated_types_in(span, &value);
3181 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}", value, substs, result);
3185 /// As `instantiate_type_scheme`, but for the bounds found in a
3186 /// generic type scheme.
3187 fn instantiate_bounds(
3191 substs: SubstsRef<'tcx>,
3192 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
3193 let bounds = self.tcx.predicates_of(def_id);
3194 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
3195 let result = bounds.instantiate(self.tcx, substs);
3196 let result = self.normalize_associated_types_in(span, &result);
3198 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
3199 bounds, substs, result, spans,
3204 /// Replaces the opaque types from the given value with type variables,
3205 /// and records the `OpaqueTypeMap` for later use during writeback. See
3206 /// `InferCtxt::instantiate_opaque_types` for more details.
3207 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
3209 parent_id: hir::HirId,
3213 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
3215 "instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
3216 parent_def_id, value
3219 let (value, opaque_type_map) =
3220 self.register_infer_ok_obligations(self.instantiate_opaque_types(
3228 let mut opaque_types = self.opaque_types.borrow_mut();
3229 let mut opaque_types_vars = self.opaque_types_vars.borrow_mut();
3230 for (ty, decl) in opaque_type_map {
3231 let _ = opaque_types.insert(ty, decl);
3232 let _ = opaque_types_vars.insert(decl.concrete_ty, decl.opaque_type);
3238 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
3240 T: TypeFoldable<'tcx>,
3242 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
3245 fn normalize_associated_types_in_as_infer_ok<T>(
3249 ) -> InferOk<'tcx, T>
3251 T: TypeFoldable<'tcx>,
3253 self.inh.partially_normalize_associated_types_in(span, self.body_id, self.param_env, value)
3256 pub fn require_type_meets(
3260 code: traits::ObligationCauseCode<'tcx>,
3263 self.register_bound(ty, def_id, traits::ObligationCause::new(span, self.body_id, code));
3266 pub fn require_type_is_sized(
3270 code: traits::ObligationCauseCode<'tcx>,
3272 if !ty.references_error() {
3273 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
3274 self.require_type_meets(ty, span, code, lang_item);
3278 pub fn require_type_is_sized_deferred(
3282 code: traits::ObligationCauseCode<'tcx>,
3284 if !ty.references_error() {
3285 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
3289 pub fn register_bound(
3293 cause: traits::ObligationCause<'tcx>,
3295 if !ty.references_error() {
3296 self.fulfillment_cx.borrow_mut().register_bound(
3306 pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> {
3307 let t = AstConv::ast_ty_to_ty(self, ast_t);
3308 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
3312 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
3313 let ty = self.to_ty(ast_ty);
3314 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
3316 if Self::can_contain_user_lifetime_bounds(ty) {
3317 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
3318 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
3319 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
3325 pub fn to_const(&self, ast_c: &hir::AnonConst) -> &'tcx ty::Const<'tcx> {
3326 let const_def_id = self.tcx.hir().local_def_id(ast_c.hir_id).expect_local();
3327 let c = ty::Const::from_anon_const(self.tcx, const_def_id);
3329 // HACK(eddyb) emulate what a `WellFormedConst` obligation would do.
3330 // This code should be replaced with the proper WF handling ASAP.
3331 if let ty::ConstKind::Unevaluated(def_id, substs, promoted) = c.val {
3332 assert!(promoted.is_none());
3334 // HACK(eddyb) let's hope these are always empty.
3335 // let obligations = self.nominal_obligations(def_id, substs);
3336 // self.out.extend(obligations);
3338 let cause = traits::ObligationCause::new(
3339 self.tcx.def_span(const_def_id.to_def_id()),
3341 traits::MiscObligation,
3343 self.register_predicate(traits::Obligation::new(
3346 ty::Predicate::ConstEvaluatable(def_id, substs),
3353 // If the type given by the user has free regions, save it for later, since
3354 // NLL would like to enforce those. Also pass in types that involve
3355 // projections, since those can resolve to `'static` bounds (modulo #54940,
3356 // which hopefully will be fixed by the time you see this comment, dear
3357 // reader, although I have my doubts). Also pass in types with inference
3358 // types, because they may be repeated. Other sorts of things are already
3359 // sufficiently enforced with erased regions. =)
3360 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
3362 T: TypeFoldable<'tcx>,
3364 t.has_free_regions() || t.has_projections() || t.has_infer_types()
3367 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
3368 match self.tables.borrow().node_types().get(id) {
3370 None if self.is_tainted_by_errors() => self.tcx.types.err,
3373 "no type for node {}: {} in fcx {}",
3375 self.tcx.hir().node_to_string(id),
3382 /// Registers an obligation for checking later, during regionck, that the type `ty` must
3383 /// outlive the region `r`.
3384 pub fn register_wf_obligation(
3388 code: traits::ObligationCauseCode<'tcx>,
3390 // WF obligations never themselves fail, so no real need to give a detailed cause:
3391 let cause = traits::ObligationCause::new(span, self.body_id, code);
3392 self.register_predicate(traits::Obligation::new(
3395 ty::Predicate::WellFormed(ty),
3399 /// Registers obligations that all types appearing in `substs` are well-formed.
3400 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr<'_>) {
3401 for ty in substs.types() {
3402 if !ty.references_error() {
3403 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
3408 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
3409 /// type/region parameter was instantiated (`substs`), creates and registers suitable
3410 /// trait/region obligations.
3412 /// For example, if there is a function:
3415 /// fn foo<'a,T:'a>(...)
3418 /// and a reference:
3424 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
3425 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
3426 pub fn add_obligations_for_parameters(
3428 cause: traits::ObligationCause<'tcx>,
3429 predicates: &ty::InstantiatedPredicates<'tcx>,
3431 assert!(!predicates.has_escaping_bound_vars());
3433 debug!("add_obligations_for_parameters(predicates={:?})", predicates);
3435 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
3436 self.register_predicate(obligation);
3440 // FIXME(arielb1): use this instead of field.ty everywhere
3441 // Only for fields! Returns <none> for methods>
3442 // Indifferent to privacy flags
3446 field: &'tcx ty::FieldDef,
3447 substs: SubstsRef<'tcx>,
3449 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
3452 fn check_casts(&self) {
3453 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3454 for cast in deferred_cast_checks.drain(..) {
3459 fn resolve_generator_interiors(&self, def_id: DefId) {
3460 let mut generators = self.deferred_generator_interiors.borrow_mut();
3461 for (body_id, interior, kind) in generators.drain(..) {
3462 self.select_obligations_where_possible(false, |_| {});
3463 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
3467 // Tries to apply a fallback to `ty` if it is an unsolved variable.
3469 // - Unconstrained ints are replaced with `i32`.
3471 // - Unconstrained floats are replaced with with `f64`.
3473 // - Non-numerics get replaced with `!` when `#![feature(never_type_fallback)]`
3474 // is enabled. Otherwise, they are replaced with `()`.
3476 // Fallback becomes very dubious if we have encountered type-checking errors.
3477 // In that case, fallback to Error.
3478 // The return value indicates whether fallback has occurred.
3479 fn fallback_if_possible(&self, ty: Ty<'tcx>, mode: FallbackMode) -> bool {
3480 use rustc_middle::ty::error::UnconstrainedNumeric::Neither;
3481 use rustc_middle::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt};
3483 assert!(ty.is_ty_infer());
3484 let fallback = match self.type_is_unconstrained_numeric(ty) {
3485 _ if self.is_tainted_by_errors() => self.tcx().types.err,
3486 UnconstrainedInt => self.tcx.types.i32,
3487 UnconstrainedFloat => self.tcx.types.f64,
3488 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
3490 // This type variable was created from the instantiation of an opaque
3491 // type. The fact that we're attempting to perform fallback for it
3492 // means that the function neither constrained it to a concrete
3493 // type, nor to the opaque type itself.
3495 // For example, in this code:
3498 // type MyType = impl Copy;
3499 // fn defining_use() -> MyType { true }
3500 // fn other_use() -> MyType { defining_use() }
3503 // `defining_use` will constrain the instantiated inference
3504 // variable to `bool`, while `other_use` will constrain
3505 // the instantiated inference variable to `MyType`.
3507 // When we process opaque types during writeback, we
3508 // will handle cases like `other_use`, and not count
3509 // them as defining usages
3511 // However, we also need to handle cases like this:
3514 // pub type Foo = impl Copy;
3515 // fn produce() -> Option<Foo> {
3520 // In the above snippet, the inference variable created by
3521 // instantiating `Option<Foo>` will be completely unconstrained.
3522 // We treat this as a non-defining use by making the inference
3523 // variable fall back to the opaque type itself.
3524 if let FallbackMode::All = mode {
3525 if let Some(opaque_ty) = self.opaque_types_vars.borrow().get(ty) {
3527 "fallback_if_possible: falling back opaque type var {:?} to {:?}",
3539 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
3540 self.demand_eqtype(rustc_span::DUMMY_SP, ty, fallback);
3544 fn select_all_obligations_or_error(&self) {
3545 debug!("select_all_obligations_or_error");
3546 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
3547 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
3551 /// Select as many obligations as we can at present.
3552 fn select_obligations_where_possible(
3554 fallback_has_occurred: bool,
3555 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
3557 let result = self.fulfillment_cx.borrow_mut().select_where_possible(self);
3558 if let Err(mut errors) = result {
3559 mutate_fullfillment_errors(&mut errors);
3560 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
3564 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
3565 /// returns a type of `&T`, but the actual type we assign to the
3566 /// *expression* is `T`. So this function just peels off the return
3567 /// type by one layer to yield `T`.
3568 fn make_overloaded_place_return_type(
3570 method: MethodCallee<'tcx>,
3571 ) -> ty::TypeAndMut<'tcx> {
3572 // extract method return type, which will be &T;
3573 let ret_ty = method.sig.output();
3575 // method returns &T, but the type as visible to user is T, so deref
3576 ret_ty.builtin_deref(true).unwrap()
3581 expr: &hir::Expr<'_>,
3582 base_expr: &'tcx hir::Expr<'tcx>,
3586 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3587 // FIXME(#18741) -- this is almost but not quite the same as the
3588 // autoderef that normal method probing does. They could likely be
3591 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3592 let mut result = None;
3593 while result.is_none() && autoderef.next().is_some() {
3594 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3596 autoderef.finalize(self);
3600 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3601 /// (and otherwise adjust) `base_expr`, looking for a type which either
3602 /// supports builtin indexing or overloaded indexing.
3603 /// This loop implements one step in that search; the autoderef loop
3604 /// is implemented by `lookup_indexing`.
3607 expr: &hir::Expr<'_>,
3608 base_expr: &hir::Expr<'_>,
3609 autoderef: &Autoderef<'a, 'tcx>,
3612 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3613 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3615 "try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3617 expr, base_expr, adjusted_ty, index_ty
3620 for &unsize in &[false, true] {
3621 let mut self_ty = adjusted_ty;
3623 // We only unsize arrays here.
3624 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3625 self_ty = self.tcx.mk_slice(element_ty);
3631 // If some lookup succeeds, write callee into table and extract index/element
3632 // type from the method signature.
3633 // If some lookup succeeded, install method in table
3634 let input_ty = self.next_ty_var(TypeVariableOrigin {
3635 kind: TypeVariableOriginKind::AutoDeref,
3636 span: base_expr.span,
3638 let method = self.try_overloaded_place_op(
3646 let result = method.map(|ok| {
3647 debug!("try_index_step: success, using overloaded indexing");
3648 let method = self.register_infer_ok_obligations(ok);
3650 let mut adjustments = autoderef.adjust_steps(self, needs);
3651 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3652 let mutbl = match r_mutbl {
3653 hir::Mutability::Not => AutoBorrowMutability::Not,
3654 hir::Mutability::Mut => AutoBorrowMutability::Mut {
3655 // Indexing can be desugared to a method call,
3656 // so maybe we could use two-phase here.
3657 // See the documentation of AllowTwoPhase for why that's
3658 // not the case today.
3659 allow_two_phase_borrow: AllowTwoPhase::No,
3662 adjustments.push(Adjustment {
3663 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3666 .mk_ref(region, ty::TypeAndMut { mutbl: r_mutbl, ty: adjusted_ty }),
3670 adjustments.push(Adjustment {
3671 kind: Adjust::Pointer(PointerCast::Unsize),
3672 target: method.sig.inputs()[0],
3675 self.apply_adjustments(base_expr, adjustments);
3677 self.write_method_call(expr.hir_id, method);
3678 (input_ty, self.make_overloaded_place_return_type(method).ty)
3680 if result.is_some() {
3688 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3689 let (tr, name) = match (op, is_mut) {
3690 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3691 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3692 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3693 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3695 (tr, ast::Ident::with_dummy_span(name))
3698 fn try_overloaded_place_op(
3702 arg_tys: &[Ty<'tcx>],
3705 ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
3706 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})", span, base_ty, needs, op);
3708 // Try Mut first, if needed.
3709 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3710 let method = match (needs, mut_tr) {
3711 (Needs::MutPlace, Some(trait_did)) => {
3712 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3717 // Otherwise, fall back to the immutable version.
3718 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3719 match (method, imm_tr) {
3720 (None, Some(trait_did)) => {
3721 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3723 (method, _) => method,
3727 fn check_method_argument_types(
3730 expr: &'tcx hir::Expr<'tcx>,
3731 method: Result<MethodCallee<'tcx>, ()>,
3732 args_no_rcvr: &'tcx [hir::Expr<'tcx>],
3733 tuple_arguments: TupleArgumentsFlag,
3734 expected: Expectation<'tcx>,
3736 let has_error = match method {
3737 Ok(method) => method.substs.references_error() || method.sig.references_error(),
3741 let err_inputs = self.err_args(args_no_rcvr.len());
3743 let err_inputs = match tuple_arguments {
3744 DontTupleArguments => err_inputs,
3745 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3748 self.check_argument_types(
3758 return self.tcx.types.err;
3761 let method = method.unwrap();
3762 // HACK(eddyb) ignore self in the definition (see above).
3763 let expected_arg_tys = self.expected_inputs_for_expected_output(
3766 method.sig.output(),
3767 &method.sig.inputs()[1..],
3769 self.check_argument_types(
3772 &method.sig.inputs()[1..],
3773 &expected_arg_tys[..],
3775 method.sig.c_variadic,
3777 self.tcx.hir().span_if_local(method.def_id),
3782 fn self_type_matches_expected_vid(
3784 trait_ref: ty::PolyTraitRef<'tcx>,
3785 expected_vid: ty::TyVid,
3787 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3789 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3790 trait_ref, self_ty, expected_vid
3792 match self_ty.kind {
3793 ty::Infer(ty::TyVar(found_vid)) => {
3794 // FIXME: consider using `sub_root_var` here so we
3795 // can see through subtyping.
3796 let found_vid = self.root_var(found_vid);
3797 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3798 expected_vid == found_vid
3804 fn obligations_for_self_ty<'b>(
3807 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3810 // FIXME: consider using `sub_root_var` here so we
3811 // can see through subtyping.
3812 let ty_var_root = self.root_var(self_ty);
3814 "obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3817 self.fulfillment_cx.borrow().pending_obligations()
3822 .pending_obligations()
3824 .filter_map(move |obligation| match obligation.predicate {
3825 ty::Predicate::Projection(ref data) => {
3826 Some((data.to_poly_trait_ref(self.tcx), obligation))
3828 ty::Predicate::Trait(ref data, _) => Some((data.to_poly_trait_ref(), obligation)),
3829 ty::Predicate::Subtype(..) => None,
3830 ty::Predicate::RegionOutlives(..) => None,
3831 ty::Predicate::TypeOutlives(..) => None,
3832 ty::Predicate::WellFormed(..) => None,
3833 ty::Predicate::ObjectSafe(..) => None,
3834 ty::Predicate::ConstEvaluatable(..) => None,
3835 // N.B., this predicate is created by breaking down a
3836 // `ClosureType: FnFoo()` predicate, where
3837 // `ClosureType` represents some `Closure`. It can't
3838 // possibly be referring to the current closure,
3839 // because we haven't produced the `Closure` for
3840 // this closure yet; this is exactly why the other
3841 // code is looking for a self type of a unresolved
3842 // inference variable.
3843 ty::Predicate::ClosureKind(..) => None,
3845 .filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3848 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3849 self.obligations_for_self_ty(self_ty)
3850 .any(|(tr, _)| Some(tr.def_id()) == self.tcx.lang_items().sized_trait())
3853 /// Generic function that factors out common logic from function calls,
3854 /// method calls and overloaded operators.
3855 fn check_argument_types(
3858 expr: &'tcx hir::Expr<'tcx>,
3859 fn_inputs: &[Ty<'tcx>],
3860 expected_arg_tys: &[Ty<'tcx>],
3861 args: &'tcx [hir::Expr<'tcx>],
3863 tuple_arguments: TupleArgumentsFlag,
3864 def_span: Option<Span>,
3867 // Grab the argument types, supplying fresh type variables
3868 // if the wrong number of arguments were supplied
3869 let supplied_arg_count = if tuple_arguments == DontTupleArguments { args.len() } else { 1 };
3871 // All the input types from the fn signature must outlive the call
3872 // so as to validate implied bounds.
3873 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3874 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3877 let expected_arg_count = fn_inputs.len();
3879 let param_count_error = |expected_count: usize,
3884 let (span, start_span, args) = match &expr.kind {
3885 hir::ExprKind::Call(hir::Expr { span, .. }, args) => (*span, *span, &args[..]),
3886 hir::ExprKind::MethodCall(path_segment, span, args) => (
3888 // `sp` doesn't point at the whole `foo.bar()`, only at `bar`.
3891 .and_then(|args| args.args.iter().last())
3892 // Account for `foo.bar::<T>()`.
3894 // Skip the closing `>`.
3897 .next_point(tcx.sess.source_map().next_point(arg.span()))
3900 &args[1..], // Skip the receiver.
3902 k => span_bug!(sp, "checking argument types on a non-call: `{:?}`", k),
3904 let arg_spans = if args.is_empty() {
3906 // ^^^-- supplied 0 arguments
3908 // expected 2 arguments
3909 vec![tcx.sess.source_map().next_point(start_span).with_hi(sp.hi())]
3912 // ^^^ - - - supplied 3 arguments
3914 // expected 2 arguments
3915 args.iter().map(|arg| arg.span).collect::<Vec<Span>>()
3918 let mut err = tcx.sess.struct_span_err_with_code(
3921 "this function takes {}{} but {} {} supplied",
3922 if c_variadic { "at least " } else { "" },
3923 potentially_plural_count(expected_count, "argument"),
3924 potentially_plural_count(arg_count, "argument"),
3925 if arg_count == 1 { "was" } else { "were" }
3927 DiagnosticId::Error(error_code.to_owned()),
3929 let label = format!("supplied {}", potentially_plural_count(arg_count, "argument"));
3930 for (i, span) in arg_spans.into_iter().enumerate() {
3933 if arg_count == 0 || i + 1 == arg_count { &label } else { "" },
3937 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().guess_head_span(sp)) {
3938 err.span_label(def_s, "defined here");
3941 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3942 // remove closing `)` from the span
3943 let sugg_span = sugg_span.shrink_to_lo();
3944 err.span_suggestion(
3946 "expected the unit value `()`; create it with empty parentheses",
3948 Applicability::MachineApplicable,
3955 if c_variadic { "at least " } else { "" },
3956 potentially_plural_count(expected_count, "argument")
3963 let mut expected_arg_tys = expected_arg_tys.to_vec();
3965 let formal_tys = if tuple_arguments == TupleArguments {
3966 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3967 match tuple_type.kind {
3968 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3969 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3970 expected_arg_tys = vec![];
3971 self.err_args(args.len())
3973 ty::Tuple(arg_types) => {
3974 expected_arg_tys = match expected_arg_tys.get(0) {
3975 Some(&ty) => match ty.kind {
3976 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3981 arg_types.iter().map(|k| k.expect_ty()).collect()
3988 "cannot use call notation; the first type parameter \
3989 for the function trait is neither a tuple nor unit"
3992 expected_arg_tys = vec![];
3993 self.err_args(args.len())
3996 } else if expected_arg_count == supplied_arg_count {
3998 } else if c_variadic {
3999 if supplied_arg_count >= expected_arg_count {
4002 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
4003 expected_arg_tys = vec![];
4004 self.err_args(supplied_arg_count)
4007 // is the missing argument of type `()`?
4008 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
4009 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
4010 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
4011 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
4015 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
4017 expected_arg_tys = vec![];
4018 self.err_args(supplied_arg_count)
4022 "check_argument_types: formal_tys={:?}",
4023 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>()
4026 // If there is no expectation, expect formal_tys.
4027 let expected_arg_tys =
4028 if !expected_arg_tys.is_empty() { expected_arg_tys } else { formal_tys.clone() };
4030 let mut final_arg_types: Vec<(usize, Ty<'_>, Ty<'_>)> = vec![];
4032 // Check the arguments.
4033 // We do this in a pretty awful way: first we type-check any arguments
4034 // that are not closures, then we type-check the closures. This is so
4035 // that we have more information about the types of arguments when we
4036 // type-check the functions. This isn't really the right way to do this.
4037 for &check_closures in &[false, true] {
4038 debug!("check_closures={}", check_closures);
4040 // More awful hacks: before we check argument types, try to do
4041 // an "opportunistic" vtable resolution of any trait bounds on
4042 // the call. This helps coercions.
4044 self.select_obligations_where_possible(false, |errors| {
4045 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
4046 self.point_at_arg_instead_of_call_if_possible(
4048 &final_arg_types[..],
4055 // For C-variadic functions, we don't have a declared type for all of
4056 // the arguments hence we only do our usual type checking with
4057 // the arguments who's types we do know.
4058 let t = if c_variadic {
4060 } else if tuple_arguments == TupleArguments {
4065 for (i, arg) in args.iter().take(t).enumerate() {
4066 // Warn only for the first loop (the "no closures" one).
4067 // Closure arguments themselves can't be diverging, but
4068 // a previous argument can, e.g., `foo(panic!(), || {})`.
4069 if !check_closures {
4070 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
4073 let is_closure = match arg.kind {
4074 ExprKind::Closure(..) => true,
4078 if is_closure != check_closures {
4082 debug!("checking the argument");
4083 let formal_ty = formal_tys[i];
4085 // The special-cased logic below has three functions:
4086 // 1. Provide as good of an expected type as possible.
4087 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
4089 let checked_ty = self.check_expr_with_expectation(&arg, expected);
4091 // 2. Coerce to the most detailed type that could be coerced
4092 // to, which is `expected_ty` if `rvalue_hint` returns an
4093 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
4094 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
4095 // We're processing function arguments so we definitely want to use
4096 // two-phase borrows.
4097 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
4098 final_arg_types.push((i, checked_ty, coerce_ty));
4100 // 3. Relate the expected type and the formal one,
4101 // if the expected type was used for the coercion.
4102 self.demand_suptype(arg.span, formal_ty, coerce_ty);
4106 // We also need to make sure we at least write the ty of the other
4107 // arguments which we skipped above.
4109 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
4110 use crate::structured_errors::{StructuredDiagnostic, VariadicError};
4111 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
4114 for arg in args.iter().skip(expected_arg_count) {
4115 let arg_ty = self.check_expr(&arg);
4117 // There are a few types which get autopromoted when passed via varargs
4118 // in C but we just error out instead and require explicit casts.
4119 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
4121 ty::Float(ast::FloatTy::F32) => {
4122 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
4124 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
4125 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
4127 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
4128 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
4131 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
4132 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
4133 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
4141 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
4142 vec![self.tcx.types.err; len]
4145 /// Given a vec of evaluated `FulfillmentError`s and an `fn` call argument expressions, we walk
4146 /// the checked and coerced types for each argument to see if any of the `FulfillmentError`s
4147 /// reference a type argument. The reason to walk also the checked type is that the coerced type
4148 /// can be not easily comparable with predicate type (because of coercion). If the types match
4149 /// for either checked or coerced type, and there's only *one* argument that does, we point at
4150 /// the corresponding argument's expression span instead of the `fn` call path span.
4151 fn point_at_arg_instead_of_call_if_possible(
4153 errors: &mut Vec<traits::FulfillmentError<'_>>,
4154 final_arg_types: &[(usize, Ty<'tcx>, Ty<'tcx>)],
4156 args: &'tcx [hir::Expr<'tcx>],
4158 // We *do not* do this for desugared call spans to keep good diagnostics when involving
4159 // the `?` operator.
4160 if call_sp.desugaring_kind().is_some() {
4164 for error in errors {
4165 // Only if the cause is somewhere inside the expression we want try to point at arg.
4166 // Otherwise, it means that the cause is somewhere else and we should not change
4167 // anything because we can break the correct span.
4168 if !call_sp.contains(error.obligation.cause.span) {
4172 if let ty::Predicate::Trait(predicate, _) = error.obligation.predicate {
4173 // Collect the argument position for all arguments that could have caused this
4174 // `FulfillmentError`.
4175 let mut referenced_in = final_arg_types
4177 .map(|&(i, checked_ty, _)| (i, checked_ty))
4178 .chain(final_arg_types.iter().map(|&(i, _, coerced_ty)| (i, coerced_ty)))
4179 .flat_map(|(i, ty)| {
4180 let ty = self.resolve_vars_if_possible(&ty);
4181 // We walk the argument type because the argument's type could have
4182 // been `Option<T>`, but the `FulfillmentError` references `T`.
4183 if ty.walk().any(|arg| arg == predicate.skip_binder().self_ty().into()) {
4189 .collect::<Vec<_>>();
4191 // Both checked and coerced types could have matched, thus we need to remove
4193 referenced_in.sort();
4194 referenced_in.dedup();
4196 if let (Some(ref_in), None) = (referenced_in.pop(), referenced_in.pop()) {
4197 // We make sure that only *one* argument matches the obligation failure
4198 // and we assign the obligation's span to its expression's.
4199 error.obligation.cause.span = args[ref_in].span;
4200 error.points_at_arg_span = true;
4206 /// Given a vec of evaluated `FulfillmentError`s and an `fn` call expression, we walk the
4207 /// `PathSegment`s and resolve their type parameters to see if any of the `FulfillmentError`s
4208 /// were caused by them. If they were, we point at the corresponding type argument's span
4209 /// instead of the `fn` call path span.
4210 fn point_at_type_arg_instead_of_call_if_possible(
4212 errors: &mut Vec<traits::FulfillmentError<'_>>,
4213 call_expr: &'tcx hir::Expr<'tcx>,
4215 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
4216 if let hir::ExprKind::Path(qpath) = &path.kind {
4217 if let hir::QPath::Resolved(_, path) = &qpath {
4218 for error in errors {
4219 if let ty::Predicate::Trait(predicate, _) = error.obligation.predicate {
4220 // If any of the type arguments in this path segment caused the
4221 // `FullfillmentError`, point at its span (#61860).
4225 .filter_map(|seg| seg.args.as_ref())
4226 .flat_map(|a| a.args.iter())
4228 if let hir::GenericArg::Type(hir_ty) = &arg {
4229 if let hir::TyKind::Path(hir::QPath::TypeRelative(..)) =
4232 // Avoid ICE with associated types. As this is best
4233 // effort only, it's ok to ignore the case. It
4234 // would trigger in `is_send::<T::AssocType>();`
4235 // from `typeck-default-trait-impl-assoc-type.rs`.
4237 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
4238 let ty = self.resolve_vars_if_possible(&ty);
4239 if ty == predicate.skip_binder().self_ty() {
4240 error.obligation.cause.span = hir_ty.span;
4252 // AST fragment checking
4253 fn check_lit(&self, lit: &hir::Lit, expected: Expectation<'tcx>) -> Ty<'tcx> {
4257 ast::LitKind::Str(..) => tcx.mk_static_str(),
4258 ast::LitKind::ByteStr(ref v) => {
4259 tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.u8, v.len() as u64))
4261 ast::LitKind::Byte(_) => tcx.types.u8,
4262 ast::LitKind::Char(_) => tcx.types.char,
4263 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
4264 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
4265 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
4266 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind {
4267 ty::Int(_) | ty::Uint(_) => Some(ty),
4268 ty::Char => Some(tcx.types.u8),
4269 ty::RawPtr(..) => Some(tcx.types.usize),
4270 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
4273 opt_ty.unwrap_or_else(|| self.next_int_var())
4275 ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => tcx.mk_mach_float(t),
4276 ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => {
4277 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind {
4278 ty::Float(_) => Some(ty),
4281 opt_ty.unwrap_or_else(|| self.next_float_var())
4283 ast::LitKind::Bool(_) => tcx.types.bool,
4284 ast::LitKind::Err(_) => tcx.types.err,
4288 /// Unifies the output type with the expected type early, for more coercions
4289 /// and forward type information on the input expressions.
4290 fn expected_inputs_for_expected_output(
4293 expected_ret: Expectation<'tcx>,
4294 formal_ret: Ty<'tcx>,
4295 formal_args: &[Ty<'tcx>],
4296 ) -> Vec<Ty<'tcx>> {
4297 let formal_ret = self.resolve_vars_with_obligations(formal_ret);
4298 let ret_ty = match expected_ret.only_has_type(self) {
4300 None => return Vec::new(),
4302 let expect_args = self
4303 .fudge_inference_if_ok(|| {
4304 // Attempt to apply a subtyping relationship between the formal
4305 // return type (likely containing type variables if the function
4306 // is polymorphic) and the expected return type.
4307 // No argument expectations are produced if unification fails.
4308 let origin = self.misc(call_span);
4309 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
4311 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
4312 // to identity so the resulting type is not constrained.
4315 // Process any obligations locally as much as
4316 // we can. We don't care if some things turn
4317 // out unconstrained or ambiguous, as we're
4318 // just trying to get hints here.
4319 self.save_and_restore_in_snapshot_flag(|_| {
4320 let mut fulfill = TraitEngine::new(self.tcx);
4321 for obligation in ok.obligations {
4322 fulfill.register_predicate_obligation(self, obligation);
4324 fulfill.select_where_possible(self)
4328 Err(_) => return Err(()),
4331 // Record all the argument types, with the substitutions
4332 // produced from the above subtyping unification.
4333 Ok(formal_args.iter().map(|ty| self.resolve_vars_if_possible(ty)).collect())
4335 .unwrap_or_default();
4337 "expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
4338 formal_args, formal_ret, expect_args, expected_ret
4343 pub fn check_struct_path(
4347 ) -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
4348 let path_span = match *qpath {
4349 QPath::Resolved(_, ref path) => path.span,
4350 QPath::TypeRelative(ref qself, _) => qself.span,
4352 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
4353 let variant = match def {
4355 self.set_tainted_by_errors();
4358 Res::Def(DefKind::Variant, _) => match ty.kind {
4359 ty::Adt(adt, substs) => Some((adt.variant_of_res(def), adt.did, substs)),
4360 _ => bug!("unexpected type: {:?}", ty),
4362 Res::Def(DefKind::Struct, _)
4363 | Res::Def(DefKind::Union, _)
4364 | Res::Def(DefKind::TyAlias, _)
4365 | Res::Def(DefKind::AssocTy, _)
4366 | Res::SelfTy(..) => match ty.kind {
4367 ty::Adt(adt, substs) if !adt.is_enum() => {
4368 Some((adt.non_enum_variant(), adt.did, substs))
4372 _ => bug!("unexpected definition: {:?}", def),
4375 if let Some((variant, did, substs)) = variant {
4376 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
4377 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
4379 // Check bounds on type arguments used in the path.
4380 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
4382 traits::ObligationCause::new(path_span, self.body_id, traits::ItemObligation(did));
4383 self.add_obligations_for_parameters(cause, &bounds);
4391 "expected struct, variant or union type, found {}",
4392 ty.sort_string(self.tcx)
4394 .span_label(path_span, "not a struct")
4400 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4401 // The newly resolved definition is written into `type_dependent_defs`.
4402 fn finish_resolving_struct_path(
4407 ) -> (Res, Ty<'tcx>) {
4409 QPath::Resolved(ref maybe_qself, ref path) => {
4410 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4411 let ty = AstConv::res_to_ty(self, self_ty, path, true);
4414 QPath::TypeRelative(ref qself, ref segment) => {
4415 let ty = self.to_ty(qself);
4417 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
4423 AstConv::associated_path_to_ty(self, hir_id, path_span, ty, res, segment, true);
4424 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
4425 let result = result.map(|(_, kind, def_id)| (kind, def_id));
4427 // Write back the new resolution.
4428 self.write_resolution(hir_id, result);
4430 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
4435 /// Resolves an associated value path into a base type and associated constant, or method
4436 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
4437 pub fn resolve_ty_and_res_ufcs<'b>(
4439 qpath: &'b QPath<'b>,
4442 ) -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment<'b>]) {
4443 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
4444 let (ty, qself, item_segment) = match *qpath {
4445 QPath::Resolved(ref opt_qself, ref path) => {
4448 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4452 QPath::TypeRelative(ref qself, ref segment) => (self.to_ty(qself), qself, segment),
4454 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
4455 // Return directly on cache hit. This is useful to avoid doubly reporting
4456 // errors with default match binding modes. See #44614.
4458 cached_result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err);
4459 return (def, Some(ty), slice::from_ref(&**item_segment));
4461 let item_name = item_segment.ident;
4462 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
4463 let result = match error {
4464 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
4465 _ => Err(ErrorReported),
4467 if item_name.name != kw::Invalid {
4468 self.report_method_error(
4472 SelfSource::QPath(qself),
4476 .map(|mut e| e.emit());
4481 // Write back the new resolution.
4482 self.write_resolution(hir_id, result);
4484 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
4486 slice::from_ref(&**item_segment),
4490 pub fn check_decl_initializer(
4492 local: &'tcx hir::Local<'tcx>,
4493 init: &'tcx hir::Expr<'tcx>,
4495 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
4496 // for #42640 (default match binding modes).
4499 let ref_bindings = local.pat.contains_explicit_ref_binding();
4501 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
4502 if let Some(m) = ref_bindings {
4503 // Somewhat subtle: if we have a `ref` binding in the pattern,
4504 // we want to avoid introducing coercions for the RHS. This is
4505 // both because it helps preserve sanity and, in the case of
4506 // ref mut, for soundness (issue #23116). In particular, in
4507 // the latter case, we need to be clear that the type of the
4508 // referent for the reference that results is *equal to* the
4509 // type of the place it is referencing, and not some
4510 // supertype thereof.
4511 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4512 self.demand_eqtype(init.span, local_ty, init_ty);
4515 self.check_expr_coercable_to_type(init, local_ty)
4519 /// Type check a `let` statement.
4520 pub fn check_decl_local(&self, local: &'tcx hir::Local<'tcx>) {
4521 // Determine and write the type which we'll check the pattern against.
4522 let ty = self.local_ty(local.span, local.hir_id).decl_ty;
4523 self.write_ty(local.hir_id, ty);
4525 // Type check the initializer.
4526 if let Some(ref init) = local.init {
4527 let init_ty = self.check_decl_initializer(local, &init);
4528 self.overwrite_local_ty_if_err(local, ty, init_ty);
4531 // Does the expected pattern type originate from an expression and what is the span?
4532 let (origin_expr, ty_span) = match (local.ty, local.init) {
4533 (Some(ty), _) => (false, Some(ty.span)), // Bias towards the explicit user type.
4534 (_, Some(init)) => (true, Some(init.span)), // No explicit type; so use the scrutinee.
4535 _ => (false, None), // We have `let $pat;`, so the expected type is unconstrained.
4538 // Type check the pattern. Override if necessary to avoid knock-on errors.
4539 self.check_pat_top(&local.pat, ty, ty_span, origin_expr);
4540 let pat_ty = self.node_ty(local.pat.hir_id);
4541 self.overwrite_local_ty_if_err(local, ty, pat_ty);
4544 fn overwrite_local_ty_if_err(
4546 local: &'tcx hir::Local<'tcx>,
4550 if ty.references_error() {
4551 // Override the types everywhere with `types.err` to avoid knock on errors.
4552 self.write_ty(local.hir_id, ty);
4553 self.write_ty(local.pat.hir_id, ty);
4554 let local_ty = LocalTy { decl_ty, revealed_ty: ty };
4555 self.locals.borrow_mut().insert(local.hir_id, local_ty);
4556 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
4560 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
4561 err.span_suggestion_short(
4562 span.shrink_to_hi(),
4563 "consider using a semicolon here",
4565 Applicability::MachineApplicable,
4569 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>) {
4570 // Don't do all the complex logic below for `DeclItem`.
4572 hir::StmtKind::Item(..) => return,
4573 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
4576 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
4578 // Hide the outer diverging and `has_errors` flags.
4579 let old_diverges = self.diverges.replace(Diverges::Maybe);
4580 let old_has_errors = self.has_errors.replace(false);
4583 hir::StmtKind::Local(ref l) => {
4584 self.check_decl_local(&l);
4587 hir::StmtKind::Item(_) => {}
4588 hir::StmtKind::Expr(ref expr) => {
4589 // Check with expected type of `()`.
4590 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
4591 self.suggest_semicolon_at_end(expr.span, err);
4594 hir::StmtKind::Semi(ref expr) => {
4595 self.check_expr(&expr);
4599 // Combine the diverging and `has_error` flags.
4600 self.diverges.set(self.diverges.get() | old_diverges);
4601 self.has_errors.set(self.has_errors.get() | old_has_errors);
4604 pub fn check_block_no_value(&self, blk: &'tcx hir::Block<'tcx>) {
4605 let unit = self.tcx.mk_unit();
4606 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4608 // if the block produces a `!` value, that can always be
4609 // (effectively) coerced to unit.
4611 self.demand_suptype(blk.span, unit, ty);
4615 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
4616 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
4617 /// when given code like the following:
4619 /// if false { return 0i32; } else { 1u32 }
4620 /// // ^^^^ point at this instead of the whole `if` expression
4622 fn get_expr_coercion_span(&self, expr: &hir::Expr<'_>) -> rustc_span::Span {
4623 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
4624 let arm_spans: Vec<Span> = arms
4627 self.in_progress_tables
4628 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
4629 .and_then(|arm_ty| {
4630 if arm_ty.is_never() {
4633 Some(match &arm.body.kind {
4634 // Point at the tail expression when possible.
4635 hir::ExprKind::Block(block, _) => {
4636 block.expr.as_ref().map(|e| e.span).unwrap_or(block.span)
4644 if arm_spans.len() == 1 {
4645 return arm_spans[0];
4651 fn check_block_with_expected(
4653 blk: &'tcx hir::Block<'tcx>,
4654 expected: Expectation<'tcx>,
4657 let mut fcx_ps = self.ps.borrow_mut();
4658 let unsafety_state = fcx_ps.recurse(blk);
4659 replace(&mut *fcx_ps, unsafety_state)
4662 // In some cases, blocks have just one exit, but other blocks
4663 // can be targeted by multiple breaks. This can happen both
4664 // with labeled blocks as well as when we desugar
4665 // a `try { ... }` expression.
4669 // 'a: { if true { break 'a Err(()); } Ok(()) }
4671 // Here we would wind up with two coercions, one from
4672 // `Err(())` and the other from the tail expression
4673 // `Ok(())`. If the tail expression is omitted, that's a
4674 // "forced unit" -- unless the block diverges, in which
4675 // case we can ignore the tail expression (e.g., `'a: {
4676 // break 'a 22; }` would not force the type of the block
4678 let tail_expr = blk.expr.as_ref();
4679 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4680 let coerce = if blk.targeted_by_break {
4681 CoerceMany::new(coerce_to_ty)
4683 let tail_expr: &[&hir::Expr<'_>] = match tail_expr {
4684 Some(e) => slice::from_ref(e),
4687 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4690 let prev_diverges = self.diverges.get();
4691 let ctxt = BreakableCtxt { coerce: Some(coerce), may_break: false };
4693 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4694 for s in blk.stmts {
4698 // check the tail expression **without** holding the
4699 // `enclosing_breakables` lock below.
4700 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4702 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4703 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4704 let coerce = ctxt.coerce.as_mut().unwrap();
4705 if let Some(tail_expr_ty) = tail_expr_ty {
4706 let tail_expr = tail_expr.unwrap();
4707 let span = self.get_expr_coercion_span(tail_expr);
4708 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4709 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4711 // Subtle: if there is no explicit tail expression,
4712 // that is typically equivalent to a tail expression
4713 // of `()` -- except if the block diverges. In that
4714 // case, there is no value supplied from the tail
4715 // expression (assuming there are no other breaks,
4716 // this implies that the type of the block will be
4719 // #41425 -- label the implicit `()` as being the
4720 // "found type" here, rather than the "expected type".
4721 if !self.diverges.get().is_always() {
4722 // #50009 -- Do not point at the entire fn block span, point at the return type
4723 // span, as it is the cause of the requirement, and
4724 // `consider_hint_about_removing_semicolon` will point at the last expression
4725 // if it were a relevant part of the error. This improves usability in editors
4726 // that highlight errors inline.
4727 let mut sp = blk.span;
4728 let mut fn_span = None;
4729 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4730 let ret_sp = decl.output.span();
4731 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4732 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4733 // output would otherwise be incorrect and even misleading. Make sure
4734 // the span we're aiming at correspond to a `fn` body.
4735 if block_sp == blk.span {
4737 fn_span = Some(ident.span);
4741 coerce.coerce_forced_unit(
4745 if let Some(expected_ty) = expected.only_has_type(self) {
4746 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4748 if let Some(fn_span) = fn_span {
4751 "implicitly returns `()` as its body has no tail or `return` \
4763 // If we can break from the block, then the block's exit is always reachable
4764 // (... as long as the entry is reachable) - regardless of the tail of the block.
4765 self.diverges.set(prev_diverges);
4768 let mut ty = ctxt.coerce.unwrap().complete(self);
4770 if self.has_errors.get() || ty.references_error() {
4771 ty = self.tcx.types.err
4774 self.write_ty(blk.hir_id, ty);
4776 *self.ps.borrow_mut() = prev;
4780 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4781 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4783 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })
4784 | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(_, body_id), .. }) => {
4785 let body = self.tcx.hir().body(body_id);
4786 if let ExprKind::Block(block, _) = &body.value.kind {
4787 return Some(block.span);
4795 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4796 fn get_parent_fn_decl(
4799 ) -> Option<(&'tcx hir::FnDecl<'tcx>, ast::Ident)> {
4800 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4801 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4804 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4805 fn get_node_fn_decl(
4808 ) -> Option<(&'tcx hir::FnDecl<'tcx>, ast::Ident, bool)> {
4810 Node::Item(&hir::Item { ident, kind: hir::ItemKind::Fn(ref sig, ..), .. }) => {
4811 // This is less than ideal, it will not suggest a return type span on any
4812 // method called `main`, regardless of whether it is actually the entry point,
4813 // but it will still present it as the reason for the expected type.
4814 Some((&sig.decl, ident, ident.name != sym::main))
4816 Node::TraitItem(&hir::TraitItem {
4818 kind: hir::TraitItemKind::Fn(ref sig, ..),
4820 }) => Some((&sig.decl, ident, true)),
4821 Node::ImplItem(&hir::ImplItem {
4823 kind: hir::ImplItemKind::Fn(ref sig, ..),
4825 }) => Some((&sig.decl, ident, false)),
4830 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4831 /// suggestion can be made, `None` otherwise.
4832 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, bool)> {
4833 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4834 // `while` before reaching it, as block tail returns are not available in them.
4835 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4836 let parent = self.tcx.hir().get(blk_id);
4837 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4841 /// On implicit return expressions with mismatched types, provides the following suggestions:
4843 /// - Points out the method's return type as the reason for the expected type.
4844 /// - Possible missing semicolon.
4845 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4846 pub fn suggest_mismatched_types_on_tail(
4848 err: &mut DiagnosticBuilder<'_>,
4849 expr: &'tcx hir::Expr<'tcx>,
4855 let expr = expr.peel_drop_temps();
4856 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4857 let mut pointing_at_return_type = false;
4858 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4859 pointing_at_return_type =
4860 self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest);
4862 pointing_at_return_type
4865 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4866 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4868 /// fn foo(x: usize) -> usize { x }
4869 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4873 err: &mut DiagnosticBuilder<'_>,
4874 expr: &hir::Expr<'_>,
4878 let hir = self.tcx.hir();
4879 let (def_id, sig) = match found.kind {
4880 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4881 ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig()),
4885 let sig = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig).0;
4886 let sig = self.normalize_associated_types_in(expr.span, &sig);
4887 if self.can_coerce(sig.output(), expected) {
4888 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4889 (String::new(), Applicability::MachineApplicable)
4891 ("...".to_string(), Applicability::HasPlaceholders)
4893 let mut msg = "call this function";
4894 match hir.get_if_local(def_id) {
4895 Some(Node::Item(hir::Item { kind: ItemKind::Fn(.., body_id), .. }))
4896 | Some(Node::ImplItem(hir::ImplItem {
4897 kind: hir::ImplItemKind::Fn(_, body_id),
4900 | Some(Node::TraitItem(hir::TraitItem {
4901 kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Provided(body_id)),
4904 let body = hir.body(*body_id);
4908 .map(|param| match ¶m.pat.kind {
4909 hir::PatKind::Binding(_, _, ident, None)
4910 if ident.name != kw::SelfLower =>
4914 _ => "_".to_string(),
4916 .collect::<Vec<_>>()
4919 Some(Node::Expr(hir::Expr {
4920 kind: ExprKind::Closure(_, _, body_id, _, _),
4921 span: full_closure_span,
4924 if *full_closure_span == expr.span {
4927 msg = "call this closure";
4928 let body = hir.body(*body_id);
4932 .map(|param| match ¶m.pat.kind {
4933 hir::PatKind::Binding(_, _, ident, None)
4934 if ident.name != kw::SelfLower =>
4938 _ => "_".to_string(),
4940 .collect::<Vec<_>>()
4943 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4944 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4945 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4946 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4947 msg = "instantiate this tuple variant";
4949 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4950 msg = "instantiate this tuple struct";
4955 Some(Node::ForeignItem(hir::ForeignItem {
4956 kind: hir::ForeignItemKind::Fn(_, idents, _),
4962 if ident.name != kw::SelfLower {
4968 .collect::<Vec<_>>()
4971 Some(Node::TraitItem(hir::TraitItem {
4972 kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Required(idents)),
4978 if ident.name != kw::SelfLower {
4984 .collect::<Vec<_>>()
4989 err.span_suggestion_verbose(
4990 expr.span.shrink_to_hi(),
4991 &format!("use parentheses to {}", msg),
4992 format!("({})", sugg_call),
5000 pub fn suggest_ref_or_into(
5002 err: &mut DiagnosticBuilder<'_>,
5003 expr: &hir::Expr<'_>,
5007 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
5008 err.span_suggestion(sp, msg, suggestion, Applicability::MachineApplicable);
5009 } else if let (ty::FnDef(def_id, ..), true) =
5010 (&found.kind, self.suggest_fn_call(err, expr, expected, found))
5012 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
5013 let sp = self.sess().source_map().guess_head_span(sp);
5014 err.span_label(sp, &format!("{} defined here", found));
5016 } else if !self.check_for_cast(err, expr, found, expected) {
5017 let is_struct_pat_shorthand_field =
5018 self.is_hir_id_from_struct_pattern_shorthand_field(expr.hir_id, expr.span);
5019 let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id);
5020 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
5021 let mut suggestions = iter::repeat(&expr_text)
5022 .zip(methods.iter())
5023 .filter_map(|(receiver, method)| {
5024 let method_call = format!(".{}()", method.ident);
5025 if receiver.ends_with(&method_call) {
5026 None // do not suggest code that is already there (#53348)
5028 let method_call_list = [".to_vec()", ".to_string()"];
5029 let sugg = if receiver.ends_with(".clone()")
5030 && method_call_list.contains(&method_call.as_str())
5032 let max_len = receiver.rfind('.').unwrap();
5033 format!("{}{}", &receiver[..max_len], method_call)
5035 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
5036 format!("({}){}", receiver, method_call)
5038 format!("{}{}", receiver, method_call)
5041 Some(if is_struct_pat_shorthand_field {
5042 format!("{}: {}", receiver, sugg)
5049 if suggestions.peek().is_some() {
5050 err.span_suggestions(
5052 "try using a conversion method",
5054 Applicability::MaybeIncorrect,
5061 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
5062 /// in the heap by calling `Box::new()`.
5063 fn suggest_boxing_when_appropriate(
5065 err: &mut DiagnosticBuilder<'_>,
5066 expr: &hir::Expr<'_>,
5070 if self.tcx.hir().is_const_context(expr.hir_id) {
5071 // Do not suggest `Box::new` in const context.
5074 if !expected.is_box() || found.is_box() {
5077 let boxed_found = self.tcx.mk_box(found);
5078 if let (true, Ok(snippet)) = (
5079 self.can_coerce(boxed_found, expected),
5080 self.sess().source_map().span_to_snippet(expr.span),
5082 err.span_suggestion(
5084 "store this in the heap by calling `Box::new`",
5085 format!("Box::new({})", snippet),
5086 Applicability::MachineApplicable,
5089 "for more on the distinction between the stack and the heap, read \
5090 https://doc.rust-lang.org/book/ch15-01-box.html, \
5091 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
5092 https://doc.rust-lang.org/std/boxed/index.html",
5097 /// When encountering an `impl Future` where `BoxFuture` is expected, suggest `Box::pin`.
5098 fn suggest_calling_boxed_future_when_appropriate(
5100 err: &mut DiagnosticBuilder<'_>,
5101 expr: &hir::Expr<'_>,
5107 if self.tcx.hir().is_const_context(expr.hir_id) {
5108 // Do not suggest `Box::new` in const context.
5111 let pin_did = self.tcx.lang_items().pin_type();
5112 match expected.kind {
5113 ty::Adt(def, _) if Some(def.did) != pin_did => return false,
5114 // This guards the `unwrap` and `mk_box` below.
5115 _ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return false,
5118 let boxed_found = self.tcx.mk_box(found);
5119 let new_found = self.tcx.mk_lang_item(boxed_found, lang_items::PinTypeLangItem).unwrap();
5120 if let (true, Ok(snippet)) = (
5121 self.can_coerce(new_found, expected),
5122 self.sess().source_map().span_to_snippet(expr.span),
5125 ty::Adt(def, _) if def.is_box() => {
5126 err.help("use `Box::pin`");
5129 err.span_suggestion(
5131 "you need to pin and box this expression",
5132 format!("Box::pin({})", snippet),
5133 Applicability::MachineApplicable,
5143 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
5147 /// bar_that_returns_u32()
5151 /// This routine checks if the return expression in a block would make sense on its own as a
5152 /// statement and the return type has been left as default or has been specified as `()`. If so,
5153 /// it suggests adding a semicolon.
5154 fn suggest_missing_semicolon(
5156 err: &mut DiagnosticBuilder<'_>,
5157 expression: &'tcx hir::Expr<'tcx>,
5161 if expected.is_unit() {
5162 // `BlockTailExpression` only relevant if the tail expr would be
5163 // useful on its own.
5164 match expression.kind {
5166 | ExprKind::MethodCall(..)
5167 | ExprKind::Loop(..)
5168 | ExprKind::Match(..)
5169 | ExprKind::Block(..) => {
5170 err.span_suggestion(
5171 cause_span.shrink_to_hi(),
5172 "try adding a semicolon",
5174 Applicability::MachineApplicable,
5182 /// A possible error is to forget to add a return type that is needed:
5186 /// bar_that_returns_u32()
5190 /// This routine checks if the return type is left as default, the method is not part of an
5191 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
5193 fn suggest_missing_return_type(
5195 err: &mut DiagnosticBuilder<'_>,
5196 fn_decl: &hir::FnDecl<'_>,
5201 // Only suggest changing the return type for methods that
5202 // haven't set a return type at all (and aren't `fn main()` or an impl).
5203 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
5204 (&hir::FnRetTy::DefaultReturn(span), true, true, true) => {
5205 err.span_suggestion(
5207 "try adding a return type",
5208 format!("-> {} ", self.resolve_vars_with_obligations(found)),
5209 Applicability::MachineApplicable,
5213 (&hir::FnRetTy::DefaultReturn(span), false, true, true) => {
5214 err.span_label(span, "possibly return type missing here?");
5217 (&hir::FnRetTy::DefaultReturn(span), _, false, true) => {
5218 // `fn main()` must return `()`, do not suggest changing return type
5219 err.span_label(span, "expected `()` because of default return type");
5222 // expectation was caused by something else, not the default return
5223 (&hir::FnRetTy::DefaultReturn(_), _, _, false) => false,
5224 (&hir::FnRetTy::Return(ref ty), _, _, _) => {
5225 // Only point to return type if the expected type is the return type, as if they
5226 // are not, the expectation must have been caused by something else.
5227 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
5229 let ty = AstConv::ast_ty_to_ty(self, ty);
5230 debug!("suggest_missing_return_type: return type {:?}", ty);
5231 debug!("suggest_missing_return_type: expected type {:?}", ty);
5232 if ty.kind == expected.kind {
5233 err.span_label(sp, format!("expected `{}` because of return type", expected));
5241 /// A possible error is to forget to add `.await` when using futures:
5244 /// async fn make_u32() -> u32 {
5248 /// fn take_u32(x: u32) {}
5250 /// async fn foo() {
5251 /// let x = make_u32();
5256 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
5257 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
5258 /// `.await` to the tail of the expression.
5259 fn suggest_missing_await(
5261 err: &mut DiagnosticBuilder<'_>,
5262 expr: &hir::Expr<'_>,
5266 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
5267 // body isn't `async`.
5268 let item_id = self.tcx().hir().get_parent_node(self.body_id);
5269 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
5270 let body = self.tcx().hir().body(body_id);
5271 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
5273 // Check for `Future` implementations by constructing a predicate to
5274 // prove: `<T as Future>::Output == U`
5275 let future_trait = self.tcx.lang_items().future_trait().unwrap();
5276 let item_def_id = self
5278 .associated_items(future_trait)
5279 .in_definition_order()
5284 ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
5285 // `<T as Future>::Output`
5286 projection_ty: ty::ProjectionTy {
5288 substs: self.tcx.mk_substs_trait(
5290 self.fresh_substs_for_item(sp, item_def_id),
5297 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
5298 debug!("suggest_missing_await: trying obligation {:?}", obligation);
5299 if self.infcx.predicate_may_hold(&obligation) {
5300 debug!("suggest_missing_await: obligation held: {:?}", obligation);
5301 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
5302 err.span_suggestion(
5304 "consider using `.await` here",
5305 format!("{}.await", code),
5306 Applicability::MaybeIncorrect,
5309 debug!("suggest_missing_await: no snippet for {:?}", sp);
5312 debug!("suggest_missing_await: obligation did not hold: {:?}", obligation)
5318 /// A common error is to add an extra semicolon:
5321 /// fn foo() -> usize {
5326 /// This routine checks if the final statement in a block is an
5327 /// expression with an explicit semicolon whose type is compatible
5328 /// with `expected_ty`. If so, it suggests removing the semicolon.
5329 fn consider_hint_about_removing_semicolon(
5331 blk: &'tcx hir::Block<'tcx>,
5332 expected_ty: Ty<'tcx>,
5333 err: &mut DiagnosticBuilder<'_>,
5335 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
5336 err.span_suggestion(
5338 "consider removing this semicolon",
5340 Applicability::MachineApplicable,
5345 fn could_remove_semicolon(
5347 blk: &'tcx hir::Block<'tcx>,
5348 expected_ty: Ty<'tcx>,
5350 // Be helpful when the user wrote `{... expr;}` and
5351 // taking the `;` off is enough to fix the error.
5352 let last_stmt = blk.stmts.last()?;
5353 let last_expr = match last_stmt.kind {
5354 hir::StmtKind::Semi(ref e) => e,
5357 let last_expr_ty = self.node_ty(last_expr.hir_id);
5358 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
5361 let original_span = original_sp(last_stmt.span, blk.span);
5362 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
5365 // Instantiates the given path, which must refer to an item with the given
5366 // number of type parameters and type.
5367 pub fn instantiate_value_path(
5369 segments: &[hir::PathSegment<'_>],
5370 self_ty: Option<Ty<'tcx>>,
5374 ) -> (Ty<'tcx>, Res) {
5376 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
5377 segments, self_ty, res, hir_id,
5382 let path_segs = match res {
5383 Res::Local(_) | Res::SelfCtor(_) => vec![],
5384 Res::Def(kind, def_id) => {
5385 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id)
5387 _ => bug!("instantiate_value_path on {:?}", res),
5390 let mut user_self_ty = None;
5391 let mut is_alias_variant_ctor = false;
5393 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
5394 if let Some(self_ty) = self_ty {
5395 let adt_def = self_ty.ty_adt_def().unwrap();
5396 user_self_ty = Some(UserSelfTy { impl_def_id: adt_def.did, self_ty });
5397 is_alias_variant_ctor = true;
5400 Res::Def(DefKind::AssocFn, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
5401 let container = tcx.associated_item(def_id).container;
5402 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
5404 ty::TraitContainer(trait_did) => {
5405 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
5407 ty::ImplContainer(impl_def_id) => {
5408 if segments.len() == 1 {
5409 // `<T>::assoc` will end up here, and so
5410 // can `T::assoc`. It this came from an
5411 // inherent impl, we need to record the
5412 // `T` for posterity (see `UserSelfTy` for
5414 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
5415 user_self_ty = Some(UserSelfTy { impl_def_id, self_ty });
5423 // Now that we have categorized what space the parameters for each
5424 // segment belong to, let's sort out the parameters that the user
5425 // provided (if any) into their appropriate spaces. We'll also report
5426 // errors if type parameters are provided in an inappropriate place.
5428 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
5429 let generics_has_err = AstConv::prohibit_generics(
5431 segments.iter().enumerate().filter_map(|(index, seg)| {
5432 if !generic_segs.contains(&index) || is_alias_variant_ctor {
5440 if let Res::Local(hid) = res {
5441 let ty = self.local_ty(span, hid).decl_ty;
5442 let ty = self.normalize_associated_types_in(span, &ty);
5443 self.write_ty(hir_id, ty);
5447 if generics_has_err {
5448 // Don't try to infer type parameters when prohibited generic arguments were given.
5449 user_self_ty = None;
5452 // Now we have to compare the types that the user *actually*
5453 // provided against the types that were *expected*. If the user
5454 // did not provide any types, then we want to substitute inference
5455 // variables. If the user provided some types, we may still need
5456 // to add defaults. If the user provided *too many* types, that's
5459 let mut infer_args_for_err = FxHashSet::default();
5460 for &PathSeg(def_id, index) in &path_segs {
5461 let seg = &segments[index];
5462 let generics = tcx.generics_of(def_id);
5463 // Argument-position `impl Trait` is treated as a normal generic
5464 // parameter internally, but we don't allow users to specify the
5465 // parameter's value explicitly, so we have to do some error-
5467 if let Err(GenericArgCountMismatch { reported: Some(ErrorReported), .. }) =
5468 AstConv::check_generic_arg_count_for_call(
5469 tcx, span, &generics, &seg, false, // `is_method_call`
5472 infer_args_for_err.insert(index);
5473 self.set_tainted_by_errors(); // See issue #53251.
5477 let has_self = path_segs
5479 .map(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self)
5482 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
5483 let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id));
5485 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
5486 let variant = adt_def.non_enum_variant();
5487 let ctor_def_id = variant.ctor_def_id.unwrap();
5489 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
5494 let mut err = tcx.sess.struct_span_err(
5496 "the `Self` constructor can only be used with tuple or unit structs",
5498 if let Some(adt_def) = ty.ty_adt_def() {
5499 match adt_def.adt_kind() {
5501 err.help("did you mean to use one of the enum's variants?");
5503 AdtKind::Struct | AdtKind::Union => {
5504 err.span_suggestion(
5506 "use curly brackets",
5507 String::from("Self { /* fields */ }"),
5508 Applicability::HasPlaceholders,
5515 return (tcx.types.err, res);
5521 let def_id = res.def_id();
5523 // The things we are substituting into the type should not contain
5524 // escaping late-bound regions, and nor should the base type scheme.
5525 let ty = tcx.type_of(def_id);
5527 let substs = self_ctor_substs.unwrap_or_else(|| {
5528 AstConv::create_substs_for_generic_args(
5534 infer_args_for_err.is_empty(),
5535 // Provide the generic args, and whether types should be inferred.
5537 if let Some(&PathSeg(_, index)) =
5538 path_segs.iter().find(|&PathSeg(did, _)| *did == def_id)
5540 // If we've encountered an `impl Trait`-related error, we're just
5541 // going to infer the arguments for better error messages.
5542 if !infer_args_for_err.contains(&index) {
5543 // Check whether the user has provided generic arguments.
5544 if let Some(ref data) = segments[index].args {
5545 return (Some(data), segments[index].infer_args);
5548 return (None, segments[index].infer_args);
5553 // Provide substitutions for parameters for which (valid) arguments have been provided.
5554 |param, arg| match (¶m.kind, arg) {
5555 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
5556 AstConv::ast_region_to_region(self, lt, Some(param)).into()
5558 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
5559 self.to_ty(ty).into()
5561 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
5562 self.to_const(&ct.value).into()
5564 _ => unreachable!(),
5566 // Provide substitutions for parameters for which arguments are inferred.
5567 |substs, param, infer_args| {
5569 GenericParamDefKind::Lifetime => {
5570 self.re_infer(Some(param), span).unwrap().into()
5572 GenericParamDefKind::Type { has_default, .. } => {
5573 if !infer_args && has_default {
5574 // If we have a default, then we it doesn't matter that we're not
5575 // inferring the type arguments: we provide the default where any
5577 let default = tcx.type_of(param.def_id);
5580 default.subst_spanned(tcx, substs.unwrap(), Some(span)),
5584 // If no type arguments were provided, we have to infer them.
5585 // This case also occurs as a result of some malformed input, e.g.
5586 // a lifetime argument being given instead of a type parameter.
5587 // Using inference instead of `Error` gives better error messages.
5588 self.var_for_def(span, param)
5591 GenericParamDefKind::Const => {
5592 // FIXME(const_generics:defaults)
5593 // No const parameters were provided, we have to infer them.
5594 self.var_for_def(span, param)
5600 assert!(!substs.has_escaping_bound_vars());
5601 assert!(!ty.has_escaping_bound_vars());
5603 // First, store the "user substs" for later.
5604 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
5606 self.add_required_obligations(span, def_id, &substs);
5608 // Substitute the values for the type parameters into the type of
5609 // the referenced item.
5610 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
5612 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
5613 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
5614 // is inherent, there is no `Self` parameter; instead, the impl needs
5615 // type parameters, which we can infer by unifying the provided `Self`
5616 // with the substituted impl type.
5617 // This also occurs for an enum variant on a type alias.
5618 let ty = tcx.type_of(impl_def_id);
5620 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
5621 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
5622 Ok(ok) => self.register_infer_ok_obligations(ok),
5624 self.tcx.sess.delay_span_bug(
5627 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
5636 self.check_rustc_args_require_const(def_id, hir_id, span);
5638 debug!("instantiate_value_path: type of {:?} is {:?}", hir_id, ty_substituted);
5639 self.write_substs(hir_id, substs);
5641 (ty_substituted, res)
5644 /// Add all the obligations that are required, substituting and normalized appropriately.
5645 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
5646 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
5648 for (i, mut obligation) in traits::predicates_for_generics(
5649 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
5656 // This makes the error point at the bound, but we want to point at the argument
5657 if let Some(span) = spans.get(i) {
5658 obligation.cause.code = traits::BindingObligation(def_id, *span);
5660 self.register_predicate(obligation);
5664 fn check_rustc_args_require_const(&self, def_id: DefId, hir_id: hir::HirId, span: Span) {
5665 // We're only interested in functions tagged with
5666 // #[rustc_args_required_const], so ignore anything that's not.
5667 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5671 // If our calling expression is indeed the function itself, we're good!
5672 // If not, generate an error that this can only be called directly.
5673 if let Node::Expr(expr) = self.tcx.hir().get(self.tcx.hir().get_parent_node(hir_id)) {
5674 if let ExprKind::Call(ref callee, ..) = expr.kind {
5675 if callee.hir_id == hir_id {
5681 self.tcx.sess.span_err(
5683 "this function can only be invoked directly, not through a function pointer",
5687 /// Resolves `typ` by a single level if `typ` is a type variable.
5688 /// If no resolution is possible, then an error is reported.
5689 /// Numeric inference variables may be left unresolved.
5690 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5691 let ty = self.resolve_vars_with_obligations(ty);
5692 if !ty.is_ty_var() {
5695 if !self.is_tainted_by_errors() {
5696 self.need_type_info_err((**self).body_id, sp, ty, E0282)
5697 .note("type must be known at this point")
5700 self.demand_suptype(sp, self.tcx.types.err, ty);
5705 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5708 ctxt: BreakableCtxt<'tcx>,
5710 ) -> (BreakableCtxt<'tcx>, R) {
5713 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5714 index = enclosing_breakables.stack.len();
5715 enclosing_breakables.by_id.insert(id, index);
5716 enclosing_breakables.stack.push(ctxt);
5720 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5721 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5722 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5723 enclosing_breakables.stack.pop().expect("missing breakable context")
5728 /// Instantiate a QueryResponse in a probe context, without a
5729 /// good ObligationCause.
5730 fn probe_instantiate_query_response(
5733 original_values: &OriginalQueryValues<'tcx>,
5734 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5735 ) -> InferResult<'tcx, Ty<'tcx>> {
5736 self.instantiate_query_response_and_region_obligations(
5737 &traits::ObligationCause::misc(span, self.body_id),
5744 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5745 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5746 let mut contained_in_place = false;
5748 while let hir::Node::Expr(parent_expr) =
5749 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5751 match &parent_expr.kind {
5752 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5753 if lhs.hir_id == expr_id {
5754 contained_in_place = true;
5760 expr_id = parent_expr.hir_id;
5767 fn check_type_params_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5768 debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty);
5770 assert_eq!(generics.parent, None);
5772 if generics.own_counts().types == 0 {
5776 let mut params_used = BitSet::new_empty(generics.params.len());
5778 if ty.references_error() {
5779 // If there is already another error, do not emit
5780 // an error for not using a type parameter.
5781 assert!(tcx.sess.has_errors());
5785 for leaf in ty.walk() {
5786 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
5787 if let ty::Param(param) = leaf_ty.kind {
5788 debug!("found use of ty param {:?}", param);
5789 params_used.insert(param.index);
5794 for param in &generics.params {
5795 if !params_used.contains(param.index) {
5796 if let ty::GenericParamDefKind::Type { .. } = param.kind {
5797 let span = tcx.def_span(param.def_id);
5802 "type parameter `{}` is unused",
5805 .span_label(span, "unused type parameter")
5812 fn fatally_break_rust(sess: &Session) {
5813 let handler = sess.diagnostic();
5814 handler.span_bug_no_panic(
5816 "It looks like you're trying to break rust; would you like some ICE?",
5818 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5819 handler.note_without_error(
5820 "we would appreciate a joke overview: \
5821 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
5823 handler.note_without_error(&format!(
5824 "rustc {} running on {}",
5825 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5826 config::host_triple(),
5830 fn potentially_plural_count(count: usize, word: &str) -> String {
5831 format!("{} {}{}", count, word, pluralize!(count))