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 {
1643 origin: hir::OpaqueTyOrigin::AsyncFn | hir::OpaqueTyOrigin::FnReturn,
1646 let mut visitor = ProhibitOpaqueVisitor {
1647 opaque_identity_ty: tcx
1648 .mk_opaque(def_id, InternalSubsts::identity_for_item(tcx, def_id)),
1649 generics: tcx.generics_of(def_id),
1651 debug!("check_opaque_for_inheriting_lifetimes: visitor={:?}", visitor);
1653 tcx.predicates_of(def_id)
1656 .any(|(predicate, _)| predicate.visit_with(&mut visitor))
1661 debug!("check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}", prohibit_opaque);
1662 if prohibit_opaque {
1663 let is_async = match item.kind {
1664 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => match origin {
1665 hir::OpaqueTyOrigin::AsyncFn => true,
1668 _ => unreachable!(),
1674 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
1676 if is_async { "async fn" } else { "impl Trait" },
1682 /// Checks that an opaque type does not contain cycles.
1683 fn check_opaque_for_cycles<'tcx>(
1686 substs: SubstsRef<'tcx>,
1688 origin: &hir::OpaqueTyOrigin,
1690 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1691 if let hir::OpaqueTyOrigin::AsyncFn = origin {
1692 struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing",)
1693 .span_label(span, "recursive `async fn`")
1694 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
1698 struct_span_err!(tcx.sess, span, E0720, "opaque type expands to a recursive type",);
1699 err.span_label(span, "expands to a recursive type");
1700 if let ty::Opaque(..) = partially_expanded_type.kind {
1701 err.note("type resolves to itself");
1703 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1710 // Forbid defining intrinsics in Rust code,
1711 // as they must always be defined by the compiler.
1712 fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
1713 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
1714 tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
1718 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item<'tcx>) {
1720 "check_item_type(it.hir_id={}, it.name={})",
1722 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id))
1724 let _indenter = indenter();
1726 // Consts can play a role in type-checking, so they are included here.
1727 hir::ItemKind::Static(..) => {
1728 let def_id = tcx.hir().local_def_id(it.hir_id);
1729 tcx.typeck_tables_of(def_id);
1730 maybe_check_static_with_link_section(tcx, def_id, it.span);
1732 hir::ItemKind::Const(..) => {
1733 tcx.typeck_tables_of(tcx.hir().local_def_id(it.hir_id));
1735 hir::ItemKind::Enum(ref enum_definition, _) => {
1736 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
1738 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1739 hir::ItemKind::Impl { ref items, .. } => {
1740 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
1741 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
1742 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1743 check_impl_items_against_trait(tcx, it.span, impl_def_id, impl_trait_ref, items);
1744 let trait_def_id = impl_trait_ref.def_id;
1745 check_on_unimplemented(tcx, trait_def_id, it);
1748 hir::ItemKind::Trait(_, _, _, _, ref items) => {
1749 let def_id = tcx.hir().local_def_id(it.hir_id);
1750 check_on_unimplemented(tcx, def_id, it);
1752 for item in items.iter() {
1753 let item = tcx.hir().trait_item(item.id);
1754 if let hir::TraitItemKind::Fn(sig, _) = &item.kind {
1755 let abi = sig.header.abi;
1756 fn_maybe_err(tcx, item.ident.span, abi);
1760 hir::ItemKind::Struct(..) => {
1761 check_struct(tcx, it.hir_id, it.span);
1763 hir::ItemKind::Union(..) => {
1764 check_union(tcx, it.hir_id, it.span);
1766 hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
1767 let def_id = tcx.hir().local_def_id(it.hir_id);
1769 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1770 check_opaque(tcx, def_id, substs, it.span, &origin);
1772 hir::ItemKind::TyAlias(..) => {
1773 let def_id = tcx.hir().local_def_id(it.hir_id);
1774 let pty_ty = tcx.type_of(def_id);
1775 let generics = tcx.generics_of(def_id);
1776 check_type_params_are_used(tcx, &generics, pty_ty);
1778 hir::ItemKind::ForeignMod(ref m) => {
1779 check_abi(tcx, it.span, m.abi);
1781 if m.abi == Abi::RustIntrinsic {
1782 for item in m.items {
1783 intrinsic::check_intrinsic_type(tcx, item);
1785 } else if m.abi == Abi::PlatformIntrinsic {
1786 for item in m.items {
1787 intrinsic::check_platform_intrinsic_type(tcx, item);
1790 for item in m.items {
1791 let generics = tcx.generics_of(tcx.hir().local_def_id(item.hir_id));
1792 let own_counts = generics.own_counts();
1793 if generics.params.len() - own_counts.lifetimes != 0 {
1794 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
1795 (_, 0) => ("type", "types", Some("u32")),
1796 // We don't specify an example value, because we can't generate
1797 // a valid value for any type.
1798 (0, _) => ("const", "consts", None),
1799 _ => ("type or const", "types or consts", None),
1805 "foreign items may not have {} parameters",
1808 .span_label(item.span, &format!("can't have {} parameters", kinds))
1810 // FIXME: once we start storing spans for type arguments, turn this
1811 // into a suggestion.
1813 "replace the {} parameters with concrete {}{}",
1816 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
1822 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.kind {
1823 require_c_abi_if_c_variadic(tcx, fn_decl, m.abi, item.span);
1828 _ => { /* nothing to do */ }
1832 fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span) {
1833 // Only restricted on wasm32 target for now
1834 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1838 // If `#[link_section]` is missing, then nothing to verify
1839 let attrs = tcx.codegen_fn_attrs(id);
1840 if attrs.link_section.is_none() {
1844 // For the wasm32 target statics with `#[link_section]` are placed into custom
1845 // sections of the final output file, but this isn't link custom sections of
1846 // other executable formats. Namely we can only embed a list of bytes,
1847 // nothing with pointers to anything else or relocations. If any relocation
1848 // show up, reject them here.
1849 // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is
1850 // the consumer's responsibility to ensure all bytes that have been read
1851 // have defined values.
1852 match tcx.const_eval_poly(id) {
1853 Ok(ConstValue::ByRef { alloc, .. }) => {
1854 if alloc.relocations().len() != 0 {
1855 let msg = "statics with a custom `#[link_section]` must be a \
1856 simple list of bytes on the wasm target with no \
1857 extra levels of indirection such as references";
1858 tcx.sess.span_err(span, msg);
1861 Ok(_) => bug!("Matching on non-ByRef static"),
1866 fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item<'_>) {
1867 let item_def_id = tcx.hir().local_def_id(item.hir_id);
1868 // an error would be reported if this fails.
1869 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1872 fn report_forbidden_specialization(
1874 impl_item: &hir::ImplItem<'_>,
1877 let mut err = struct_span_err!(
1881 "`{}` specializes an item from a parent `impl`, but \
1882 that item is not marked `default`",
1885 err.span_label(impl_item.span, format!("cannot specialize default item `{}`", impl_item.ident));
1887 match tcx.span_of_impl(parent_impl) {
1889 err.span_label(span, "parent `impl` is here");
1891 "to specialize, `{}` in the parent `impl` must be marked `default`",
1896 err.note(&format!("parent implementation is in crate `{}`", cname));
1903 fn check_specialization_validity<'tcx>(
1905 trait_def: &ty::TraitDef,
1906 trait_item: &ty::AssocItem,
1908 impl_item: &hir::ImplItem<'_>,
1910 let kind = match impl_item.kind {
1911 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
1912 hir::ImplItemKind::Fn(..) => ty::AssocKind::Fn,
1913 hir::ImplItemKind::OpaqueTy(..) => ty::AssocKind::OpaqueTy,
1914 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
1917 let ancestors = match trait_def.ancestors(tcx, impl_id) {
1918 Ok(ancestors) => ancestors,
1921 let mut ancestor_impls = ancestors
1923 .filter_map(|parent| {
1924 if parent.is_from_trait() {
1927 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
1932 if ancestor_impls.peek().is_none() {
1933 // No parent, nothing to specialize.
1937 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
1939 // Parent impl exists, and contains the parent item we're trying to specialize, but
1940 // doesn't mark it `default`.
1941 Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
1942 Some(Err(parent_impl.def_id()))
1945 // Parent impl contains item and makes it specializable.
1946 Some(_) => Some(Ok(())),
1948 // Parent impl doesn't mention the item. This means it's inherited from the
1949 // grandparent. In that case, if parent is a `default impl`, inherited items use the
1950 // "defaultness" from the grandparent, else they are final.
1952 if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
1955 Some(Err(parent_impl.def_id()))
1961 // If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the
1962 // item. This is allowed, the item isn't actually getting specialized here.
1963 let result = opt_result.unwrap_or(Ok(()));
1965 if let Err(parent_impl) = result {
1966 report_forbidden_specialization(tcx, impl_item, parent_impl);
1970 fn check_impl_items_against_trait<'tcx>(
1972 full_impl_span: Span,
1974 impl_trait_ref: ty::TraitRef<'tcx>,
1975 impl_item_refs: &[hir::ImplItemRef<'_>],
1977 let impl_span = tcx.sess.source_map().guess_head_span(full_impl_span);
1979 // If the trait reference itself is erroneous (so the compilation is going
1980 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1981 // isn't populated for such impls.
1982 if impl_trait_ref.references_error() {
1986 // Negative impls are not expected to have any items
1987 match tcx.impl_polarity(impl_id) {
1988 ty::ImplPolarity::Reservation | ty::ImplPolarity::Positive => {}
1989 ty::ImplPolarity::Negative => {
1990 if let [first_item_ref, ..] = impl_item_refs {
1991 let first_item_span = tcx.hir().impl_item(first_item_ref.id).span;
1996 "negative impls cannot have any items"
2004 // Locate trait definition and items
2005 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
2007 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
2009 // Check existing impl methods to see if they are both present in trait
2010 // and compatible with trait signature
2011 for impl_item in impl_items() {
2012 let namespace = impl_item.kind.namespace();
2013 let ty_impl_item = tcx.associated_item(tcx.hir().local_def_id(impl_item.hir_id));
2014 let ty_trait_item = tcx
2015 .associated_items(impl_trait_ref.def_id)
2016 .find_by_name_and_namespace(tcx, ty_impl_item.ident, namespace, impl_trait_ref.def_id)
2018 // Not compatible, but needed for the error message
2019 tcx.associated_items(impl_trait_ref.def_id)
2020 .filter_by_name(tcx, ty_impl_item.ident, impl_trait_ref.def_id)
2024 // Check that impl definition matches trait definition
2025 if let Some(ty_trait_item) = ty_trait_item {
2026 match impl_item.kind {
2027 hir::ImplItemKind::Const(..) => {
2028 // Find associated const definition.
2029 if ty_trait_item.kind == ty::AssocKind::Const {
2038 let mut err = struct_span_err!(
2042 "item `{}` is an associated const, \
2043 which doesn't match its trait `{}`",
2045 impl_trait_ref.print_only_trait_path()
2047 err.span_label(impl_item.span, "does not match trait");
2048 // We can only get the spans from local trait definition
2049 // Same for E0324 and E0325
2050 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
2051 err.span_label(trait_span, "item in trait");
2056 hir::ImplItemKind::Fn(..) => {
2057 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
2058 if ty_trait_item.kind == ty::AssocKind::Fn {
2059 compare_impl_method(
2068 let mut err = struct_span_err!(
2072 "item `{}` is an associated method, \
2073 which doesn't match its trait `{}`",
2075 impl_trait_ref.print_only_trait_path()
2077 err.span_label(impl_item.span, "does not match trait");
2078 if let Some(trait_span) = opt_trait_span {
2079 err.span_label(trait_span, "item in trait");
2084 hir::ImplItemKind::OpaqueTy(..) | hir::ImplItemKind::TyAlias(_) => {
2085 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
2086 if ty_trait_item.kind == ty::AssocKind::Type {
2096 let mut err = struct_span_err!(
2100 "item `{}` is an associated type, \
2101 which doesn't match its trait `{}`",
2103 impl_trait_ref.print_only_trait_path()
2105 err.span_label(impl_item.span, "does not match trait");
2106 if let Some(trait_span) = opt_trait_span {
2107 err.span_label(trait_span, "item in trait");
2114 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
2118 // Check for missing items from trait
2119 let mut missing_items = Vec::new();
2120 if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id) {
2121 for trait_item in tcx.associated_items(impl_trait_ref.def_id).in_definition_order() {
2122 let is_implemented = ancestors
2123 .leaf_def(tcx, trait_item.ident, trait_item.kind)
2124 .map(|node_item| !node_item.defining_node.is_from_trait())
2127 if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
2128 if !trait_item.defaultness.has_value() {
2129 missing_items.push(*trait_item);
2135 if !missing_items.is_empty() {
2136 missing_items_err(tcx, impl_span, &missing_items, full_impl_span);
2140 fn missing_items_err(
2143 missing_items: &[ty::AssocItem],
2144 full_impl_span: Span,
2146 let missing_items_msg = missing_items
2148 .map(|trait_item| trait_item.ident.to_string())
2149 .collect::<Vec<_>>()
2152 let mut err = struct_span_err!(
2156 "not all trait items implemented, missing: `{}`",
2159 err.span_label(impl_span, format!("missing `{}` in implementation", missing_items_msg));
2161 // `Span` before impl block closing brace.
2162 let hi = full_impl_span.hi() - BytePos(1);
2163 // Point at the place right before the closing brace of the relevant `impl` to suggest
2164 // adding the associated item at the end of its body.
2165 let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi);
2166 // Obtain the level of indentation ending in `sugg_sp`.
2167 let indentation = tcx.sess.source_map().span_to_margin(sugg_sp).unwrap_or(0);
2168 // Make the whitespace that will make the suggestion have the right indentation.
2169 let padding: String = (0..indentation).map(|_| " ").collect();
2171 for trait_item in missing_items {
2172 let snippet = suggestion_signature(&trait_item, tcx);
2173 let code = format!("{}{}\n{}", padding, snippet, padding);
2174 let msg = format!("implement the missing item: `{}`", snippet);
2175 let appl = Applicability::HasPlaceholders;
2176 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
2177 err.span_label(span, format!("`{}` from trait", trait_item.ident));
2178 err.tool_only_span_suggestion(sugg_sp, &msg, code, appl);
2180 err.span_suggestion_hidden(sugg_sp, &msg, code, appl);
2186 /// Resugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions.
2187 fn bounds_from_generic_predicates(
2189 predicates: ty::GenericPredicates<'_>,
2190 ) -> (String, String) {
2191 let mut types: FxHashMap<Ty<'_>, Vec<DefId>> = FxHashMap::default();
2192 let mut projections = vec![];
2193 for (predicate, _) in predicates.predicates {
2194 debug!("predicate {:?}", predicate);
2196 ty::Predicate::Trait(trait_predicate, _) => {
2197 let entry = types.entry(trait_predicate.skip_binder().self_ty()).or_default();
2198 let def_id = trait_predicate.skip_binder().def_id();
2199 if Some(def_id) != tcx.lang_items().sized_trait() {
2200 // Type params are `Sized` by default, do not add that restriction to the list
2201 // if it is a positive requirement.
2202 entry.push(trait_predicate.skip_binder().def_id());
2205 ty::Predicate::Projection(projection_pred) => {
2206 projections.push(projection_pred);
2211 let generics = if types.is_empty() {
2218 .filter_map(|t| match t.kind {
2219 ty::Param(_) => Some(t.to_string()),
2220 // Avoid suggesting the following:
2221 // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {}
2224 .collect::<Vec<_>>()
2228 let mut where_clauses = vec![];
2229 for (ty, bounds) in types {
2230 for bound in &bounds {
2231 where_clauses.push(format!("{}: {}", ty, tcx.def_path_str(*bound)));
2234 for projection in &projections {
2235 let p = projection.skip_binder();
2236 // FIXME: this is not currently supported syntax, we should be looking at the `types` and
2237 // insert the associated types where they correspond, but for now let's be "lazy" and
2238 // propose this instead of the following valid resugaring:
2239 // `T: Trait, Trait::Assoc = K` → `T: Trait<Assoc = K>`
2240 where_clauses.push(format!("{} = {}", tcx.def_path_str(p.projection_ty.item_def_id), p.ty));
2242 let where_clauses = if where_clauses.is_empty() {
2245 format!(" where {}", where_clauses.join(", "))
2247 (generics, where_clauses)
2250 /// Return placeholder code for the given function.
2251 fn fn_sig_suggestion(
2253 sig: &ty::FnSig<'_>,
2255 predicates: ty::GenericPredicates<'_>,
2256 assoc: &ty::AssocItem,
2263 Some(match ty.kind {
2264 ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
2265 ty::Ref(reg, ref_ty, mutability) if i == 0 => {
2266 let reg = match &format!("{}", reg)[..] {
2267 "'_" | "" => String::new(),
2268 reg => format!("{} ", reg),
2270 if assoc.fn_has_self_parameter {
2272 ty::Param(param) if param.name == kw::SelfUpper => {
2273 format!("&{}{}self", reg, mutability.prefix_str())
2276 _ => format!("self: {}", ty),
2279 format!("_: {:?}", ty)
2283 if assoc.fn_has_self_parameter && i == 0 {
2284 format!("self: {:?}", ty)
2286 format!("_: {:?}", ty)
2291 .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None }))
2292 .filter_map(|arg| arg)
2293 .collect::<Vec<String>>()
2295 let output = sig.output();
2296 let output = if !output.is_unit() { format!(" -> {:?}", output) } else { String::new() };
2298 let unsafety = sig.unsafety.prefix_str();
2299 let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
2301 // FIXME: this is not entirely correct, as the lifetimes from borrowed params will
2302 // not be present in the `fn` definition, not will we account for renamed
2303 // lifetimes between the `impl` and the `trait`, but this should be good enough to
2304 // fill in a significant portion of the missing code, and other subsequent
2305 // suggestions can help the user fix the code.
2307 "{}fn {}{}({}){}{} {{ todo!() }}",
2308 unsafety, ident, generics, args, output, where_clauses
2312 /// Return placeholder code for the given associated item.
2313 /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a
2314 /// structured suggestion.
2315 fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
2317 ty::AssocKind::Fn => {
2318 // We skip the binder here because the binder would deanonymize all
2319 // late-bound regions, and we don't want method signatures to show up
2320 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
2321 // regions just fine, showing `fn(&MyType)`.
2324 tcx.fn_sig(assoc.def_id).skip_binder(),
2326 tcx.predicates_of(assoc.def_id),
2330 ty::AssocKind::Type => format!("type {} = Type;", assoc.ident),
2331 // FIXME(type_alias_impl_trait): we should print bounds here too.
2332 ty::AssocKind::OpaqueTy => format!("type {} = Type;", assoc.ident),
2333 ty::AssocKind::Const => {
2334 let ty = tcx.type_of(assoc.def_id);
2335 let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
2336 format!("const {}: {:?} = {};", assoc.ident, ty, val)
2341 /// Checks whether a type can be represented in memory. In particular, it
2342 /// identifies types that contain themselves without indirection through a
2343 /// pointer, which would mean their size is unbounded.
2344 fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: DefId) -> bool {
2345 let rty = tcx.type_of(item_def_id);
2347 // Check that it is possible to represent this type. This call identifies
2348 // (1) types that contain themselves and (2) types that contain a different
2349 // recursive type. It is only necessary to throw an error on those that
2350 // contain themselves. For case 2, there must be an inner type that will be
2351 // caught by case 1.
2352 match rty.is_representable(tcx, sp) {
2353 Representability::SelfRecursive(spans) => {
2354 let mut err = recursive_type_with_infinite_size_error(tcx, item_def_id);
2356 err.span_label(span, "recursive without indirection");
2361 Representability::Representable | Representability::ContainsRecursive => (),
2366 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2367 let t = tcx.type_of(def_id);
2368 if let ty::Adt(def, substs) = t.kind {
2369 if def.is_struct() {
2370 let fields = &def.non_enum_variant().fields;
2371 if fields.is_empty() {
2372 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
2375 let e = fields[0].ty(tcx, substs);
2376 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
2377 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
2378 .span_label(sp, "SIMD elements must have the same type")
2383 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
2384 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
2390 "SIMD vector element type should be machine type"
2400 fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2401 let repr = tcx.adt_def(def_id).repr;
2403 for attr in tcx.get_attrs(def_id).iter() {
2404 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
2405 if let attr::ReprPacked(pack) = r {
2406 if let Some(repr_pack) = repr.pack {
2407 if pack as u64 != repr_pack.bytes() {
2412 "type has conflicting packed representation hints"
2420 if repr.align.is_some() {
2425 "type has conflicting packed and align representation hints"
2429 if let Some(def_spans) = check_packed_inner(tcx, def_id, &mut vec![]) {
2430 let mut err = struct_span_err!(
2434 "packed type cannot transitively contain a `#[repr(align)]` type"
2437 let hir = tcx.hir();
2438 if let Some(hir_id) = hir.as_local_hir_id(def_spans[0].0) {
2439 if let Node::Item(Item { ident, .. }) = hir.get(hir_id) {
2441 tcx.def_span(def_spans[0].0),
2442 &format!("`{}` has a `#[repr(align)]` attribute", ident),
2447 if def_spans.len() > 2 {
2448 let mut first = true;
2449 for (adt_def, span) in def_spans.iter().skip(1).rev() {
2450 if let Some(hir_id) = hir.as_local_hir_id(*adt_def) {
2451 if let Node::Item(Item { ident, .. }) = hir.get(hir_id) {
2456 "`{}` contains a field of type `{}`",
2457 tcx.type_of(def_id),
2461 format!("...which contains a field of type `{}`", ident)
2476 fn check_packed_inner(
2479 stack: &mut Vec<DefId>,
2480 ) -> Option<Vec<(DefId, Span)>> {
2481 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind {
2482 if def.is_struct() || def.is_union() {
2483 if def.repr.align.is_some() {
2484 return Some(vec![(def.did, DUMMY_SP)]);
2488 for field in &def.non_enum_variant().fields {
2489 if let ty::Adt(def, _) = field.ty(tcx, substs).kind {
2490 if !stack.contains(&def.did) {
2491 if let Some(mut defs) = check_packed_inner(tcx, def.did, stack) {
2492 defs.push((def.did, field.ident.span));
2505 /// Emit an error when encountering more or less than one variant in a transparent enum.
2506 fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: &'tcx ty::AdtDef, sp: Span, did: DefId) {
2507 let variant_spans: Vec<_> = adt
2510 .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap())
2512 let msg = format!("needs exactly one variant, but has {}", adt.variants.len(),);
2513 let mut err = struct_span_err!(tcx.sess, sp, E0731, "transparent enum {}", msg);
2514 err.span_label(sp, &msg);
2515 if let [start @ .., end] = &*variant_spans {
2516 for variant_span in start {
2517 err.span_label(*variant_span, "");
2519 err.span_label(*end, &format!("too many variants in `{}`", tcx.def_path_str(did)));
2524 /// Emit an error when encountering more or less than one non-zero-sized field in a transparent
2526 fn bad_non_zero_sized_fields<'tcx>(
2528 adt: &'tcx ty::AdtDef,
2530 field_spans: impl Iterator<Item = Span>,
2533 let msg = format!("needs exactly one non-zero-sized field, but has {}", field_count);
2534 let mut err = struct_span_err!(
2538 "{}transparent {} {}",
2539 if adt.is_enum() { "the variant of a " } else { "" },
2543 err.span_label(sp, &msg);
2544 for sp in field_spans {
2545 err.span_label(sp, "this field is non-zero-sized");
2550 fn check_transparent(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
2551 let adt = tcx.adt_def(def_id);
2552 if !adt.repr.transparent() {
2555 let sp = tcx.sess.source_map().guess_head_span(sp);
2557 if adt.is_union() && !tcx.features().transparent_unions {
2559 &tcx.sess.parse_sess,
2560 sym::transparent_unions,
2562 "transparent unions are unstable",
2567 if adt.variants.len() != 1 {
2568 bad_variant_count(tcx, adt, sp, def_id);
2569 if adt.variants.is_empty() {
2570 // Don't bother checking the fields. No variants (and thus no fields) exist.
2575 // For each field, figure out if it's known to be a ZST and align(1)
2576 let field_infos = adt.all_fields().map(|field| {
2577 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
2578 let param_env = tcx.param_env(field.did);
2579 let layout = tcx.layout_of(param_env.and(ty));
2580 // We are currently checking the type this field came from, so it must be local
2581 let span = tcx.hir().span_if_local(field.did).unwrap();
2582 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
2583 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
2587 let non_zst_fields =
2588 field_infos.clone().filter_map(|(span, zst, _align1)| if !zst { Some(span) } else { None });
2589 let non_zst_count = non_zst_fields.clone().count();
2590 if non_zst_count != 1 {
2591 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
2593 for (span, zst, align1) in field_infos {
2599 "zero-sized field in transparent {} has alignment larger than 1",
2602 .span_label(span, "has alignment larger than 1")
2608 #[allow(trivial_numeric_casts)]
2609 pub fn check_enum<'tcx>(
2612 vs: &'tcx [hir::Variant<'tcx>],
2615 let def_id = tcx.hir().local_def_id(id);
2616 let def = tcx.adt_def(def_id);
2617 def.destructor(tcx); // force the destructor to be evaluated
2620 let attributes = tcx.get_attrs(def_id);
2621 if let Some(attr) = attr::find_by_name(&attributes, sym::repr) {
2626 "unsupported representation for zero-variant enum"
2628 .span_label(sp, "zero-variant enum")
2633 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
2634 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
2635 if !tcx.features().repr128 {
2637 &tcx.sess.parse_sess,
2640 "repr with 128-bit type is unstable",
2647 if let Some(ref e) = v.disr_expr {
2648 tcx.typeck_tables_of(tcx.hir().local_def_id(e.hir_id));
2652 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
2653 let is_unit = |var: &hir::Variant<'_>| match var.data {
2654 hir::VariantData::Unit(..) => true,
2658 let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();
2659 let has_non_units = vs.iter().any(|var| !is_unit(var));
2660 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
2661 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
2663 if disr_non_unit || (disr_units && has_non_units) {
2665 struct_span_err!(tcx.sess, sp, E0732, "`#[repr(inttype)]` must be specified");
2670 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
2671 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
2672 // Check for duplicate discriminant values
2673 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
2674 let variant_did = def.variants[VariantIdx::new(i)].def_id;
2675 let variant_i_hir_id = tcx.hir().as_local_hir_id(variant_did).unwrap();
2676 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
2677 let i_span = match variant_i.disr_expr {
2678 Some(ref expr) => tcx.hir().span(expr.hir_id),
2679 None => tcx.hir().span(variant_i_hir_id),
2681 let span = match v.disr_expr {
2682 Some(ref expr) => tcx.hir().span(expr.hir_id),
2689 "discriminant value `{}` already exists",
2692 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
2693 .span_label(span, format!("enum already has `{}`", disr_vals[i]))
2696 disr_vals.push(discr);
2699 check_representable(tcx, sp, def_id);
2700 check_transparent(tcx, sp, def_id);
2703 fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, span: Span) {
2708 "expected unit struct, unit variant or constant, found {}{}",
2710 tcx.sess.source_map().span_to_snippet(span).map_or(String::new(), |s| format!(" `{}`", s)),
2715 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
2716 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
2720 fn item_def_id(&self) -> Option<DefId> {
2724 fn default_constness_for_trait_bounds(&self) -> hir::Constness {
2725 // FIXME: refactor this into a method
2726 let node = self.tcx.hir().get(self.body_id);
2727 if let Some(fn_like) = FnLikeNode::from_node(node) {
2730 hir::Constness::NotConst
2734 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2736 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2737 let item_id = tcx.hir().ty_param_owner(hir_id);
2738 let item_def_id = tcx.hir().local_def_id(item_id);
2739 let generics = tcx.generics_of(item_def_id);
2740 let index = generics.param_def_id_to_index[&def_id];
2741 ty::GenericPredicates {
2743 predicates: tcx.arena.alloc_from_iter(self.param_env.caller_bounds.iter().filter_map(
2744 |&predicate| match predicate {
2745 ty::Predicate::Trait(ref data, _)
2746 if data.skip_binder().self_ty().is_param(index) =>
2748 // HACK(eddyb) should get the original `Span`.
2749 let span = tcx.def_span(def_id);
2750 Some((predicate, span))
2758 fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
2760 Some(def) => infer::EarlyBoundRegion(span, def.name),
2761 None => infer::MiscVariable(span),
2763 Some(self.next_region_var(v))
2766 fn allow_ty_infer(&self) -> bool {
2770 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
2771 if let Some(param) = param {
2772 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
2777 self.next_ty_var(TypeVariableOrigin {
2778 kind: TypeVariableOriginKind::TypeInference,
2787 param: Option<&ty::GenericParamDef>,
2789 ) -> &'tcx Const<'tcx> {
2790 if let Some(param) = param {
2791 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
2796 self.next_const_var(
2798 ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
2803 fn projected_ty_from_poly_trait_ref(
2807 item_segment: &hir::PathSegment<'_>,
2808 poly_trait_ref: ty::PolyTraitRef<'tcx>,
2810 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
2812 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
2816 let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
2825 self.tcx().mk_projection(item_def_id, item_substs)
2828 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
2829 if ty.has_escaping_bound_vars() {
2830 ty // FIXME: normalization and escaping regions
2832 self.normalize_associated_types_in(span, &ty)
2836 fn set_tainted_by_errors(&self) {
2837 self.infcx.set_tainted_by_errors()
2840 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
2841 self.write_ty(hir_id, ty)
2845 /// Controls whether the arguments are tupled. This is used for the call
2848 /// Tupling means that all call-side arguments are packed into a tuple and
2849 /// passed as a single parameter. For example, if tupling is enabled, this
2852 /// fn f(x: (isize, isize))
2854 /// Can be called as:
2861 #[derive(Clone, Eq, PartialEq)]
2862 enum TupleArgumentsFlag {
2867 /// Controls how we perform fallback for unconstrained
2870 /// Do not fallback type variables to opaque types.
2872 /// Perform all possible kinds of fallback, including
2873 /// turning type variables to opaque types.
2877 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
2879 inh: &'a Inherited<'a, 'tcx>,
2880 param_env: ty::ParamEnv<'tcx>,
2881 body_id: hir::HirId,
2882 ) -> FnCtxt<'a, 'tcx> {
2886 err_count_on_creation: inh.tcx.sess.err_count(),
2888 ret_coercion_span: RefCell::new(None),
2889 resume_yield_tys: None,
2890 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
2891 diverges: Cell::new(Diverges::Maybe),
2892 has_errors: Cell::new(false),
2893 enclosing_breakables: RefCell::new(EnclosingBreakables {
2895 by_id: Default::default(),
2901 pub fn sess(&self) -> &Session {
2905 pub fn errors_reported_since_creation(&self) -> bool {
2906 self.tcx.sess.err_count() > self.err_count_on_creation
2909 /// Produces warning on the given node, if the current point in the
2910 /// function is unreachable, and there hasn't been another warning.
2911 fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
2912 // FIXME: Combine these two 'if' expressions into one once
2913 // let chains are implemented
2914 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
2915 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
2916 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
2917 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
2918 if !span.is_desugaring(DesugaringKind::CondTemporary)
2919 && !span.is_desugaring(DesugaringKind::Async)
2920 && !orig_span.is_desugaring(DesugaringKind::Await)
2922 self.diverges.set(Diverges::WarnedAlways);
2924 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2926 self.tcx().struct_span_lint_hir(lint::builtin::UNREACHABLE_CODE, id, span, |lint| {
2927 let msg = format!("unreachable {}", kind);
2929 .span_label(span, &msg)
2933 .unwrap_or("any code following this expression is unreachable"),
2941 pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
2942 ObligationCause::new(span, self.body_id, code)
2945 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2946 self.cause(span, ObligationCauseCode::MiscObligation)
2949 /// Resolves type and const variables in `ty` if possible. Unlike the infcx
2950 /// version (resolve_vars_if_possible), this version will
2951 /// also select obligations if it seems useful, in an effort
2952 /// to get more type information.
2953 fn resolve_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2954 debug!("resolve_vars_with_obligations(ty={:?})", ty);
2956 // No Infer()? Nothing needs doing.
2957 if !ty.has_infer_types_or_consts() {
2958 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2962 // If `ty` is a type variable, see whether we already know what it is.
2963 ty = self.resolve_vars_if_possible(&ty);
2964 if !ty.has_infer_types_or_consts() {
2965 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2969 // If not, try resolving pending obligations as much as
2970 // possible. This can help substantially when there are
2971 // indirect dependencies that don't seem worth tracking
2973 self.select_obligations_where_possible(false, |_| {});
2974 ty = self.resolve_vars_if_possible(&ty);
2976 debug!("resolve_vars_with_obligations: ty={:?}", ty);
2980 fn record_deferred_call_resolution(
2982 closure_def_id: DefId,
2983 r: DeferredCallResolution<'tcx>,
2985 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2986 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2989 fn remove_deferred_call_resolutions(
2991 closure_def_id: DefId,
2992 ) -> Vec<DeferredCallResolution<'tcx>> {
2993 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2994 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2997 pub fn tag(&self) -> String {
2998 format!("{:p}", self)
3001 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
3002 self.locals.borrow().get(&nid).cloned().unwrap_or_else(|| {
3003 span_bug!(span, "no type for local variable {}", self.tcx.hir().node_to_string(nid))
3008 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
3010 "write_ty({:?}, {:?}) in fcx {}",
3012 self.resolve_vars_if_possible(&ty),
3015 self.tables.borrow_mut().node_types_mut().insert(id, ty);
3017 if ty.references_error() {
3018 self.has_errors.set(true);
3019 self.set_tainted_by_errors();
3023 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
3024 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
3027 fn write_resolution(&self, hir_id: hir::HirId, r: Result<(DefKind, DefId), ErrorReported>) {
3028 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
3031 pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
3032 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
3033 self.write_resolution(hir_id, Ok((DefKind::AssocFn, method.def_id)));
3034 self.write_substs(hir_id, method.substs);
3036 // When the method is confirmed, the `method.substs` includes
3037 // parameters from not just the method, but also the impl of
3038 // the method -- in particular, the `Self` type will be fully
3039 // resolved. However, those are not something that the "user
3040 // specified" -- i.e., those types come from the inferred type
3041 // of the receiver, not something the user wrote. So when we
3042 // create the user-substs, we want to replace those earlier
3043 // types with just the types that the user actually wrote --
3044 // that is, those that appear on the *method itself*.
3046 // As an example, if the user wrote something like
3047 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
3048 // type of `foo` (possibly adjusted), but we don't want to
3049 // include that. We want just the `[_, u32]` part.
3050 if !method.substs.is_noop() {
3051 let method_generics = self.tcx.generics_of(method.def_id);
3052 if !method_generics.params.is_empty() {
3053 let user_type_annotation = self.infcx.probe(|_| {
3054 let user_substs = UserSubsts {
3055 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
3056 let i = param.index as usize;
3057 if i < method_generics.parent_count {
3058 self.infcx.var_for_def(DUMMY_SP, param)
3063 user_self_ty: None, // not relevant here
3066 self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
3072 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
3073 self.write_user_type_annotation(hir_id, user_type_annotation);
3078 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
3079 if !substs.is_noop() {
3080 debug!("write_substs({:?}, {:?}) in fcx {}", node_id, substs, self.tag());
3082 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
3086 /// Given the substs that we just converted from the HIR, try to
3087 /// canonicalize them and store them as user-given substitutions
3088 /// (i.e., substitutions that must be respected by the NLL check).
3090 /// This should be invoked **before any unifications have
3091 /// occurred**, so that annotations like `Vec<_>` are preserved
3093 pub fn write_user_type_annotation_from_substs(
3097 substs: SubstsRef<'tcx>,
3098 user_self_ty: Option<UserSelfTy<'tcx>>,
3101 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
3102 user_self_ty={:?} in fcx {}",
3110 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
3111 let canonicalized = self.infcx.canonicalize_user_type_annotation(&UserType::TypeOf(
3113 UserSubsts { substs, user_self_ty },
3115 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
3116 self.write_user_type_annotation(hir_id, canonicalized);
3120 pub fn write_user_type_annotation(
3123 canonical_user_type_annotation: CanonicalUserType<'tcx>,
3126 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
3128 canonical_user_type_annotation,
3132 if !canonical_user_type_annotation.is_identity() {
3135 .user_provided_types_mut()
3136 .insert(hir_id, canonical_user_type_annotation);
3138 debug!("write_user_type_annotation: skipping identity substs");
3142 pub fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment<'tcx>>) {
3143 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
3149 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
3150 Entry::Vacant(entry) => {
3153 Entry::Occupied(mut entry) => {
3154 debug!(" - composing on top of {:?}", entry.get());
3155 match (&entry.get()[..], &adj[..]) {
3156 // Applying any adjustment on top of a NeverToAny
3157 // is a valid NeverToAny adjustment, because it can't
3159 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
3161 Adjustment { kind: Adjust::Deref(_), .. },
3162 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
3164 Adjustment { kind: Adjust::Deref(_), .. },
3165 .. // Any following adjustments are allowed.
3167 // A reborrow has no effect before a dereference.
3169 // FIXME: currently we never try to compose autoderefs
3170 // and ReifyFnPointer/UnsafeFnPointer, but we could.
3172 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
3173 expr, entry.get(), adj)
3175 *entry.get_mut() = adj;
3180 /// Basically whenever we are converting from a type scheme into
3181 /// the fn body space, we always want to normalize associated
3182 /// types as well. This function combines the two.
3183 fn instantiate_type_scheme<T>(&self, span: Span, substs: SubstsRef<'tcx>, value: &T) -> T
3185 T: TypeFoldable<'tcx>,
3187 let value = value.subst(self.tcx, substs);
3188 let result = self.normalize_associated_types_in(span, &value);
3189 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}", value, substs, result);
3193 /// As `instantiate_type_scheme`, but for the bounds found in a
3194 /// generic type scheme.
3195 fn instantiate_bounds(
3199 substs: SubstsRef<'tcx>,
3200 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
3201 let bounds = self.tcx.predicates_of(def_id);
3202 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
3203 let result = bounds.instantiate(self.tcx, substs);
3204 let result = self.normalize_associated_types_in(span, &result);
3206 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
3207 bounds, substs, result, spans,
3212 /// Replaces the opaque types from the given value with type variables,
3213 /// and records the `OpaqueTypeMap` for later use during writeback. See
3214 /// `InferCtxt::instantiate_opaque_types` for more details.
3215 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
3217 parent_id: hir::HirId,
3221 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
3223 "instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
3224 parent_def_id, value
3227 let (value, opaque_type_map) =
3228 self.register_infer_ok_obligations(self.instantiate_opaque_types(
3236 let mut opaque_types = self.opaque_types.borrow_mut();
3237 let mut opaque_types_vars = self.opaque_types_vars.borrow_mut();
3238 for (ty, decl) in opaque_type_map {
3239 let _ = opaque_types.insert(ty, decl);
3240 let _ = opaque_types_vars.insert(decl.concrete_ty, decl.opaque_type);
3246 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
3248 T: TypeFoldable<'tcx>,
3250 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
3253 fn normalize_associated_types_in_as_infer_ok<T>(
3257 ) -> InferOk<'tcx, T>
3259 T: TypeFoldable<'tcx>,
3261 self.inh.partially_normalize_associated_types_in(span, self.body_id, self.param_env, value)
3264 pub fn require_type_meets(
3268 code: traits::ObligationCauseCode<'tcx>,
3271 self.register_bound(ty, def_id, traits::ObligationCause::new(span, self.body_id, code));
3274 pub fn require_type_is_sized(
3278 code: traits::ObligationCauseCode<'tcx>,
3280 if !ty.references_error() {
3281 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
3282 self.require_type_meets(ty, span, code, lang_item);
3286 pub fn require_type_is_sized_deferred(
3290 code: traits::ObligationCauseCode<'tcx>,
3292 if !ty.references_error() {
3293 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
3297 pub fn register_bound(
3301 cause: traits::ObligationCause<'tcx>,
3303 if !ty.references_error() {
3304 self.fulfillment_cx.borrow_mut().register_bound(
3314 pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> {
3315 let t = AstConv::ast_ty_to_ty(self, ast_t);
3316 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
3320 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
3321 let ty = self.to_ty(ast_ty);
3322 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
3324 if Self::can_contain_user_lifetime_bounds(ty) {
3325 let c_ty = self.infcx.canonicalize_response(&UserType::Ty(ty));
3326 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
3327 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
3333 pub fn to_const(&self, ast_c: &hir::AnonConst) -> &'tcx ty::Const<'tcx> {
3334 let const_def_id = self.tcx.hir().local_def_id(ast_c.hir_id).expect_local();
3335 let c = ty::Const::from_anon_const(self.tcx, const_def_id);
3337 // HACK(eddyb) emulate what a `WellFormedConst` obligation would do.
3338 // This code should be replaced with the proper WF handling ASAP.
3339 if let ty::ConstKind::Unevaluated(def_id, substs, promoted) = c.val {
3340 assert!(promoted.is_none());
3342 // HACK(eddyb) let's hope these are always empty.
3343 // let obligations = self.nominal_obligations(def_id, substs);
3344 // self.out.extend(obligations);
3346 let cause = traits::ObligationCause::new(
3347 self.tcx.def_span(const_def_id.to_def_id()),
3349 traits::MiscObligation,
3351 self.register_predicate(traits::Obligation::new(
3354 ty::Predicate::ConstEvaluatable(def_id, substs),
3361 // If the type given by the user has free regions, save it for later, since
3362 // NLL would like to enforce those. Also pass in types that involve
3363 // projections, since those can resolve to `'static` bounds (modulo #54940,
3364 // which hopefully will be fixed by the time you see this comment, dear
3365 // reader, although I have my doubts). Also pass in types with inference
3366 // types, because they may be repeated. Other sorts of things are already
3367 // sufficiently enforced with erased regions. =)
3368 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
3370 T: TypeFoldable<'tcx>,
3372 t.has_free_regions() || t.has_projections() || t.has_infer_types()
3375 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
3376 match self.tables.borrow().node_types().get(id) {
3378 None if self.is_tainted_by_errors() => self.tcx.types.err,
3381 "no type for node {}: {} in fcx {}",
3383 self.tcx.hir().node_to_string(id),
3390 /// Registers an obligation for checking later, during regionck, that the type `ty` must
3391 /// outlive the region `r`.
3392 pub fn register_wf_obligation(
3396 code: traits::ObligationCauseCode<'tcx>,
3398 // WF obligations never themselves fail, so no real need to give a detailed cause:
3399 let cause = traits::ObligationCause::new(span, self.body_id, code);
3400 self.register_predicate(traits::Obligation::new(
3403 ty::Predicate::WellFormed(ty),
3407 /// Registers obligations that all types appearing in `substs` are well-formed.
3408 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr<'_>) {
3409 for ty in substs.types() {
3410 if !ty.references_error() {
3411 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
3416 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
3417 /// type/region parameter was instantiated (`substs`), creates and registers suitable
3418 /// trait/region obligations.
3420 /// For example, if there is a function:
3423 /// fn foo<'a,T:'a>(...)
3426 /// and a reference:
3432 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
3433 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
3434 pub fn add_obligations_for_parameters(
3436 cause: traits::ObligationCause<'tcx>,
3437 predicates: &ty::InstantiatedPredicates<'tcx>,
3439 assert!(!predicates.has_escaping_bound_vars());
3441 debug!("add_obligations_for_parameters(predicates={:?})", predicates);
3443 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
3444 self.register_predicate(obligation);
3448 // FIXME(arielb1): use this instead of field.ty everywhere
3449 // Only for fields! Returns <none> for methods>
3450 // Indifferent to privacy flags
3454 field: &'tcx ty::FieldDef,
3455 substs: SubstsRef<'tcx>,
3457 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
3460 fn check_casts(&self) {
3461 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
3462 for cast in deferred_cast_checks.drain(..) {
3467 fn resolve_generator_interiors(&self, def_id: DefId) {
3468 let mut generators = self.deferred_generator_interiors.borrow_mut();
3469 for (body_id, interior, kind) in generators.drain(..) {
3470 self.select_obligations_where_possible(false, |_| {});
3471 generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
3475 // Tries to apply a fallback to `ty` if it is an unsolved variable.
3477 // - Unconstrained ints are replaced with `i32`.
3479 // - Unconstrained floats are replaced with with `f64`.
3481 // - Non-numerics get replaced with `!` when `#![feature(never_type_fallback)]`
3482 // is enabled. Otherwise, they are replaced with `()`.
3484 // Fallback becomes very dubious if we have encountered type-checking errors.
3485 // In that case, fallback to Error.
3486 // The return value indicates whether fallback has occurred.
3487 fn fallback_if_possible(&self, ty: Ty<'tcx>, mode: FallbackMode) -> bool {
3488 use rustc_middle::ty::error::UnconstrainedNumeric::Neither;
3489 use rustc_middle::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt};
3491 assert!(ty.is_ty_infer());
3492 let fallback = match self.type_is_unconstrained_numeric(ty) {
3493 _ if self.is_tainted_by_errors() => self.tcx().types.err,
3494 UnconstrainedInt => self.tcx.types.i32,
3495 UnconstrainedFloat => self.tcx.types.f64,
3496 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
3498 // This type variable was created from the instantiation of an opaque
3499 // type. The fact that we're attempting to perform fallback for it
3500 // means that the function neither constrained it to a concrete
3501 // type, nor to the opaque type itself.
3503 // For example, in this code:
3506 // type MyType = impl Copy;
3507 // fn defining_use() -> MyType { true }
3508 // fn other_use() -> MyType { defining_use() }
3511 // `defining_use` will constrain the instantiated inference
3512 // variable to `bool`, while `other_use` will constrain
3513 // the instantiated inference variable to `MyType`.
3515 // When we process opaque types during writeback, we
3516 // will handle cases like `other_use`, and not count
3517 // them as defining usages
3519 // However, we also need to handle cases like this:
3522 // pub type Foo = impl Copy;
3523 // fn produce() -> Option<Foo> {
3528 // In the above snippet, the inference variable created by
3529 // instantiating `Option<Foo>` will be completely unconstrained.
3530 // We treat this as a non-defining use by making the inference
3531 // variable fall back to the opaque type itself.
3532 if let FallbackMode::All = mode {
3533 if let Some(opaque_ty) = self.opaque_types_vars.borrow().get(ty) {
3535 "fallback_if_possible: falling back opaque type var {:?} to {:?}",
3547 debug!("fallback_if_possible: defaulting `{:?}` to `{:?}`", ty, fallback);
3548 self.demand_eqtype(rustc_span::DUMMY_SP, ty, fallback);
3552 fn select_all_obligations_or_error(&self) {
3553 debug!("select_all_obligations_or_error");
3554 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
3555 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
3559 /// Select as many obligations as we can at present.
3560 fn select_obligations_where_possible(
3562 fallback_has_occurred: bool,
3563 mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
3565 let result = self.fulfillment_cx.borrow_mut().select_where_possible(self);
3566 if let Err(mut errors) = result {
3567 mutate_fullfillment_errors(&mut errors);
3568 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
3572 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
3573 /// returns a type of `&T`, but the actual type we assign to the
3574 /// *expression* is `T`. So this function just peels off the return
3575 /// type by one layer to yield `T`.
3576 fn make_overloaded_place_return_type(
3578 method: MethodCallee<'tcx>,
3579 ) -> ty::TypeAndMut<'tcx> {
3580 // extract method return type, which will be &T;
3581 let ret_ty = method.sig.output();
3583 // method returns &T, but the type as visible to user is T, so deref
3584 ret_ty.builtin_deref(true).unwrap()
3589 expr: &hir::Expr<'_>,
3590 base_expr: &'tcx hir::Expr<'tcx>,
3594 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3595 // FIXME(#18741) -- this is almost but not quite the same as the
3596 // autoderef that normal method probing does. They could likely be
3599 let mut autoderef = self.autoderef(base_expr.span, base_ty);
3600 let mut result = None;
3601 while result.is_none() && autoderef.next().is_some() {
3602 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
3604 autoderef.finalize(self);
3608 /// To type-check `base_expr[index_expr]`, we progressively autoderef
3609 /// (and otherwise adjust) `base_expr`, looking for a type which either
3610 /// supports builtin indexing or overloaded indexing.
3611 /// This loop implements one step in that search; the autoderef loop
3612 /// is implemented by `lookup_indexing`.
3615 expr: &hir::Expr<'_>,
3616 base_expr: &hir::Expr<'_>,
3617 autoderef: &Autoderef<'a, 'tcx>,
3620 ) -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)> {
3621 let adjusted_ty = autoderef.unambiguous_final_ty(self);
3623 "try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
3625 expr, base_expr, adjusted_ty, index_ty
3628 for &unsize in &[false, true] {
3629 let mut self_ty = adjusted_ty;
3631 // We only unsize arrays here.
3632 if let ty::Array(element_ty, _) = adjusted_ty.kind {
3633 self_ty = self.tcx.mk_slice(element_ty);
3639 // If some lookup succeeds, write callee into table and extract index/element
3640 // type from the method signature.
3641 // If some lookup succeeded, install method in table
3642 let input_ty = self.next_ty_var(TypeVariableOrigin {
3643 kind: TypeVariableOriginKind::AutoDeref,
3644 span: base_expr.span,
3646 let method = self.try_overloaded_place_op(
3654 let result = method.map(|ok| {
3655 debug!("try_index_step: success, using overloaded indexing");
3656 let method = self.register_infer_ok_obligations(ok);
3658 let mut adjustments = autoderef.adjust_steps(self, needs);
3659 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].kind {
3660 let mutbl = match r_mutbl {
3661 hir::Mutability::Not => AutoBorrowMutability::Not,
3662 hir::Mutability::Mut => AutoBorrowMutability::Mut {
3663 // Indexing can be desugared to a method call,
3664 // so maybe we could use two-phase here.
3665 // See the documentation of AllowTwoPhase for why that's
3666 // not the case today.
3667 allow_two_phase_borrow: AllowTwoPhase::No,
3670 adjustments.push(Adjustment {
3671 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
3674 .mk_ref(region, ty::TypeAndMut { mutbl: r_mutbl, ty: adjusted_ty }),
3678 adjustments.push(Adjustment {
3679 kind: Adjust::Pointer(PointerCast::Unsize),
3680 target: method.sig.inputs()[0],
3683 self.apply_adjustments(base_expr, adjustments);
3685 self.write_method_call(expr.hir_id, method);
3686 (input_ty, self.make_overloaded_place_return_type(method).ty)
3688 if result.is_some() {
3696 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
3697 let (tr, name) = match (op, is_mut) {
3698 (PlaceOp::Deref, false) => (self.tcx.lang_items().deref_trait(), sym::deref),
3699 (PlaceOp::Deref, true) => (self.tcx.lang_items().deref_mut_trait(), sym::deref_mut),
3700 (PlaceOp::Index, false) => (self.tcx.lang_items().index_trait(), sym::index),
3701 (PlaceOp::Index, true) => (self.tcx.lang_items().index_mut_trait(), sym::index_mut),
3703 (tr, ast::Ident::with_dummy_span(name))
3706 fn try_overloaded_place_op(
3710 arg_tys: &[Ty<'tcx>],
3713 ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
3714 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})", span, base_ty, needs, op);
3716 // Try Mut first, if needed.
3717 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
3718 let method = match (needs, mut_tr) {
3719 (Needs::MutPlace, Some(trait_did)) => {
3720 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
3725 // Otherwise, fall back to the immutable version.
3726 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
3727 match (method, imm_tr) {
3728 (None, Some(trait_did)) => {
3729 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
3731 (method, _) => method,
3735 fn check_method_argument_types(
3738 expr: &'tcx hir::Expr<'tcx>,
3739 method: Result<MethodCallee<'tcx>, ()>,
3740 args_no_rcvr: &'tcx [hir::Expr<'tcx>],
3741 tuple_arguments: TupleArgumentsFlag,
3742 expected: Expectation<'tcx>,
3744 let has_error = match method {
3745 Ok(method) => method.substs.references_error() || method.sig.references_error(),
3749 let err_inputs = self.err_args(args_no_rcvr.len());
3751 let err_inputs = match tuple_arguments {
3752 DontTupleArguments => err_inputs,
3753 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
3756 self.check_argument_types(
3766 return self.tcx.types.err;
3769 let method = method.unwrap();
3770 // HACK(eddyb) ignore self in the definition (see above).
3771 let expected_arg_tys = self.expected_inputs_for_expected_output(
3774 method.sig.output(),
3775 &method.sig.inputs()[1..],
3777 self.check_argument_types(
3780 &method.sig.inputs()[1..],
3781 &expected_arg_tys[..],
3783 method.sig.c_variadic,
3785 self.tcx.hir().span_if_local(method.def_id),
3790 fn self_type_matches_expected_vid(
3792 trait_ref: ty::PolyTraitRef<'tcx>,
3793 expected_vid: ty::TyVid,
3795 let self_ty = self.shallow_resolve(trait_ref.self_ty());
3797 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
3798 trait_ref, self_ty, expected_vid
3800 match self_ty.kind {
3801 ty::Infer(ty::TyVar(found_vid)) => {
3802 // FIXME: consider using `sub_root_var` here so we
3803 // can see through subtyping.
3804 let found_vid = self.root_var(found_vid);
3805 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
3806 expected_vid == found_vid
3812 fn obligations_for_self_ty<'b>(
3815 ) -> impl Iterator<Item = (ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
3818 // FIXME: consider using `sub_root_var` here so we
3819 // can see through subtyping.
3820 let ty_var_root = self.root_var(self_ty);
3822 "obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
3825 self.fulfillment_cx.borrow().pending_obligations()
3830 .pending_obligations()
3832 .filter_map(move |obligation| match obligation.predicate {
3833 ty::Predicate::Projection(ref data) => {
3834 Some((data.to_poly_trait_ref(self.tcx), obligation))
3836 ty::Predicate::Trait(ref data, _) => Some((data.to_poly_trait_ref(), obligation)),
3837 ty::Predicate::Subtype(..) => None,
3838 ty::Predicate::RegionOutlives(..) => None,
3839 ty::Predicate::TypeOutlives(..) => None,
3840 ty::Predicate::WellFormed(..) => None,
3841 ty::Predicate::ObjectSafe(..) => None,
3842 ty::Predicate::ConstEvaluatable(..) => None,
3843 // N.B., this predicate is created by breaking down a
3844 // `ClosureType: FnFoo()` predicate, where
3845 // `ClosureType` represents some `Closure`. It can't
3846 // possibly be referring to the current closure,
3847 // because we haven't produced the `Closure` for
3848 // this closure yet; this is exactly why the other
3849 // code is looking for a self type of a unresolved
3850 // inference variable.
3851 ty::Predicate::ClosureKind(..) => None,
3853 .filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
3856 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
3857 self.obligations_for_self_ty(self_ty)
3858 .any(|(tr, _)| Some(tr.def_id()) == self.tcx.lang_items().sized_trait())
3861 /// Generic function that factors out common logic from function calls,
3862 /// method calls and overloaded operators.
3863 fn check_argument_types(
3866 expr: &'tcx hir::Expr<'tcx>,
3867 fn_inputs: &[Ty<'tcx>],
3868 expected_arg_tys: &[Ty<'tcx>],
3869 args: &'tcx [hir::Expr<'tcx>],
3871 tuple_arguments: TupleArgumentsFlag,
3872 def_span: Option<Span>,
3875 // Grab the argument types, supplying fresh type variables
3876 // if the wrong number of arguments were supplied
3877 let supplied_arg_count = if tuple_arguments == DontTupleArguments { args.len() } else { 1 };
3879 // All the input types from the fn signature must outlive the call
3880 // so as to validate implied bounds.
3881 for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
3882 self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
3885 let expected_arg_count = fn_inputs.len();
3887 let param_count_error = |expected_count: usize,
3892 let (span, start_span, args) = match &expr.kind {
3893 hir::ExprKind::Call(hir::Expr { span, .. }, args) => (*span, *span, &args[..]),
3894 hir::ExprKind::MethodCall(path_segment, span, args) => (
3896 // `sp` doesn't point at the whole `foo.bar()`, only at `bar`.
3899 .and_then(|args| args.args.iter().last())
3900 // Account for `foo.bar::<T>()`.
3902 // Skip the closing `>`.
3905 .next_point(tcx.sess.source_map().next_point(arg.span()))
3908 &args[1..], // Skip the receiver.
3910 k => span_bug!(sp, "checking argument types on a non-call: `{:?}`", k),
3912 let arg_spans = if args.is_empty() {
3914 // ^^^-- supplied 0 arguments
3916 // expected 2 arguments
3917 vec![tcx.sess.source_map().next_point(start_span).with_hi(sp.hi())]
3920 // ^^^ - - - supplied 3 arguments
3922 // expected 2 arguments
3923 args.iter().map(|arg| arg.span).collect::<Vec<Span>>()
3926 let mut err = tcx.sess.struct_span_err_with_code(
3929 "this function takes {}{} but {} {} supplied",
3930 if c_variadic { "at least " } else { "" },
3931 potentially_plural_count(expected_count, "argument"),
3932 potentially_plural_count(arg_count, "argument"),
3933 if arg_count == 1 { "was" } else { "were" }
3935 DiagnosticId::Error(error_code.to_owned()),
3937 let label = format!("supplied {}", potentially_plural_count(arg_count, "argument"));
3938 for (i, span) in arg_spans.into_iter().enumerate() {
3941 if arg_count == 0 || i + 1 == arg_count { &label } else { "" },
3945 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().guess_head_span(sp)) {
3946 err.span_label(def_s, "defined here");
3949 let sugg_span = tcx.sess.source_map().end_point(expr.span);
3950 // remove closing `)` from the span
3951 let sugg_span = sugg_span.shrink_to_lo();
3952 err.span_suggestion(
3954 "expected the unit value `()`; create it with empty parentheses",
3956 Applicability::MachineApplicable,
3963 if c_variadic { "at least " } else { "" },
3964 potentially_plural_count(expected_count, "argument")
3971 let mut expected_arg_tys = expected_arg_tys.to_vec();
3973 let formal_tys = if tuple_arguments == TupleArguments {
3974 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
3975 match tuple_type.kind {
3976 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
3977 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
3978 expected_arg_tys = vec![];
3979 self.err_args(args.len())
3981 ty::Tuple(arg_types) => {
3982 expected_arg_tys = match expected_arg_tys.get(0) {
3983 Some(&ty) => match ty.kind {
3984 ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).collect(),
3989 arg_types.iter().map(|k| k.expect_ty()).collect()
3996 "cannot use call notation; the first type parameter \
3997 for the function trait is neither a tuple nor unit"
4000 expected_arg_tys = vec![];
4001 self.err_args(args.len())
4004 } else if expected_arg_count == supplied_arg_count {
4006 } else if c_variadic {
4007 if supplied_arg_count >= expected_arg_count {
4010 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
4011 expected_arg_tys = vec![];
4012 self.err_args(supplied_arg_count)
4015 // is the missing argument of type `()`?
4016 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
4017 self.resolve_vars_if_possible(&expected_arg_tys[0]).is_unit()
4018 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
4019 self.resolve_vars_if_possible(&fn_inputs[0]).is_unit()
4023 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
4025 expected_arg_tys = vec![];
4026 self.err_args(supplied_arg_count)
4030 "check_argument_types: formal_tys={:?}",
4031 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>()
4034 // If there is no expectation, expect formal_tys.
4035 let expected_arg_tys =
4036 if !expected_arg_tys.is_empty() { expected_arg_tys } else { formal_tys.clone() };
4038 let mut final_arg_types: Vec<(usize, Ty<'_>, Ty<'_>)> = vec![];
4040 // Check the arguments.
4041 // We do this in a pretty awful way: first we type-check any arguments
4042 // that are not closures, then we type-check the closures. This is so
4043 // that we have more information about the types of arguments when we
4044 // type-check the functions. This isn't really the right way to do this.
4045 for &check_closures in &[false, true] {
4046 debug!("check_closures={}", check_closures);
4048 // More awful hacks: before we check argument types, try to do
4049 // an "opportunistic" vtable resolution of any trait bounds on
4050 // the call. This helps coercions.
4052 self.select_obligations_where_possible(false, |errors| {
4053 self.point_at_type_arg_instead_of_call_if_possible(errors, expr);
4054 self.point_at_arg_instead_of_call_if_possible(
4056 &final_arg_types[..],
4063 // For C-variadic functions, we don't have a declared type for all of
4064 // the arguments hence we only do our usual type checking with
4065 // the arguments who's types we do know.
4066 let t = if c_variadic {
4068 } else if tuple_arguments == TupleArguments {
4073 for (i, arg) in args.iter().take(t).enumerate() {
4074 // Warn only for the first loop (the "no closures" one).
4075 // Closure arguments themselves can't be diverging, but
4076 // a previous argument can, e.g., `foo(panic!(), || {})`.
4077 if !check_closures {
4078 self.warn_if_unreachable(arg.hir_id, arg.span, "expression");
4081 let is_closure = match arg.kind {
4082 ExprKind::Closure(..) => true,
4086 if is_closure != check_closures {
4090 debug!("checking the argument");
4091 let formal_ty = formal_tys[i];
4093 // The special-cased logic below has three functions:
4094 // 1. Provide as good of an expected type as possible.
4095 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
4097 let checked_ty = self.check_expr_with_expectation(&arg, expected);
4099 // 2. Coerce to the most detailed type that could be coerced
4100 // to, which is `expected_ty` if `rvalue_hint` returns an
4101 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
4102 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
4103 // We're processing function arguments so we definitely want to use
4104 // two-phase borrows.
4105 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
4106 final_arg_types.push((i, checked_ty, coerce_ty));
4108 // 3. Relate the expected type and the formal one,
4109 // if the expected type was used for the coercion.
4110 self.demand_suptype(arg.span, formal_ty, coerce_ty);
4114 // We also need to make sure we at least write the ty of the other
4115 // arguments which we skipped above.
4117 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
4118 use crate::structured_errors::{StructuredDiagnostic, VariadicError};
4119 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
4122 for arg in args.iter().skip(expected_arg_count) {
4123 let arg_ty = self.check_expr(&arg);
4125 // There are a few types which get autopromoted when passed via varargs
4126 // in C but we just error out instead and require explicit casts.
4127 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
4129 ty::Float(ast::FloatTy::F32) => {
4130 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
4132 ty::Int(ast::IntTy::I8 | ast::IntTy::I16) | ty::Bool => {
4133 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
4135 ty::Uint(ast::UintTy::U8 | ast::UintTy::U16) => {
4136 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
4139 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
4140 let ptr_ty = self.resolve_vars_if_possible(&ptr_ty);
4141 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
4149 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
4150 vec![self.tcx.types.err; len]
4153 /// Given a vec of evaluated `FulfillmentError`s and an `fn` call argument expressions, we walk
4154 /// the checked and coerced types for each argument to see if any of the `FulfillmentError`s
4155 /// reference a type argument. The reason to walk also the checked type is that the coerced type
4156 /// can be not easily comparable with predicate type (because of coercion). If the types match
4157 /// for either checked or coerced type, and there's only *one* argument that does, we point at
4158 /// the corresponding argument's expression span instead of the `fn` call path span.
4159 fn point_at_arg_instead_of_call_if_possible(
4161 errors: &mut Vec<traits::FulfillmentError<'_>>,
4162 final_arg_types: &[(usize, Ty<'tcx>, Ty<'tcx>)],
4164 args: &'tcx [hir::Expr<'tcx>],
4166 // We *do not* do this for desugared call spans to keep good diagnostics when involving
4167 // the `?` operator.
4168 if call_sp.desugaring_kind().is_some() {
4172 for error in errors {
4173 // Only if the cause is somewhere inside the expression we want try to point at arg.
4174 // Otherwise, it means that the cause is somewhere else and we should not change
4175 // anything because we can break the correct span.
4176 if !call_sp.contains(error.obligation.cause.span) {
4180 if let ty::Predicate::Trait(predicate, _) = error.obligation.predicate {
4181 // Collect the argument position for all arguments that could have caused this
4182 // `FulfillmentError`.
4183 let mut referenced_in = final_arg_types
4185 .map(|&(i, checked_ty, _)| (i, checked_ty))
4186 .chain(final_arg_types.iter().map(|&(i, _, coerced_ty)| (i, coerced_ty)))
4187 .flat_map(|(i, ty)| {
4188 let ty = self.resolve_vars_if_possible(&ty);
4189 // We walk the argument type because the argument's type could have
4190 // been `Option<T>`, but the `FulfillmentError` references `T`.
4191 if ty.walk().any(|arg| arg == predicate.skip_binder().self_ty().into()) {
4197 .collect::<Vec<_>>();
4199 // Both checked and coerced types could have matched, thus we need to remove
4201 referenced_in.sort();
4202 referenced_in.dedup();
4204 if let (Some(ref_in), None) = (referenced_in.pop(), referenced_in.pop()) {
4205 // We make sure that only *one* argument matches the obligation failure
4206 // and we assign the obligation's span to its expression's.
4207 error.obligation.cause.span = args[ref_in].span;
4208 error.points_at_arg_span = true;
4214 /// Given a vec of evaluated `FulfillmentError`s and an `fn` call expression, we walk the
4215 /// `PathSegment`s and resolve their type parameters to see if any of the `FulfillmentError`s
4216 /// were caused by them. If they were, we point at the corresponding type argument's span
4217 /// instead of the `fn` call path span.
4218 fn point_at_type_arg_instead_of_call_if_possible(
4220 errors: &mut Vec<traits::FulfillmentError<'_>>,
4221 call_expr: &'tcx hir::Expr<'tcx>,
4223 if let hir::ExprKind::Call(path, _) = &call_expr.kind {
4224 if let hir::ExprKind::Path(qpath) = &path.kind {
4225 if let hir::QPath::Resolved(_, path) = &qpath {
4226 for error in errors {
4227 if let ty::Predicate::Trait(predicate, _) = error.obligation.predicate {
4228 // If any of the type arguments in this path segment caused the
4229 // `FullfillmentError`, point at its span (#61860).
4233 .filter_map(|seg| seg.args.as_ref())
4234 .flat_map(|a| a.args.iter())
4236 if let hir::GenericArg::Type(hir_ty) = &arg {
4237 if let hir::TyKind::Path(hir::QPath::TypeRelative(..)) =
4240 // Avoid ICE with associated types. As this is best
4241 // effort only, it's ok to ignore the case. It
4242 // would trigger in `is_send::<T::AssocType>();`
4243 // from `typeck-default-trait-impl-assoc-type.rs`.
4245 let ty = AstConv::ast_ty_to_ty(self, hir_ty);
4246 let ty = self.resolve_vars_if_possible(&ty);
4247 if ty == predicate.skip_binder().self_ty() {
4248 error.obligation.cause.span = hir_ty.span;
4260 // AST fragment checking
4261 fn check_lit(&self, lit: &hir::Lit, expected: Expectation<'tcx>) -> Ty<'tcx> {
4265 ast::LitKind::Str(..) => tcx.mk_static_str(),
4266 ast::LitKind::ByteStr(ref v) => {
4267 tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.u8, v.len() as u64))
4269 ast::LitKind::Byte(_) => tcx.types.u8,
4270 ast::LitKind::Char(_) => tcx.types.char,
4271 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
4272 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
4273 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
4274 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind {
4275 ty::Int(_) | ty::Uint(_) => Some(ty),
4276 ty::Char => Some(tcx.types.u8),
4277 ty::RawPtr(..) => Some(tcx.types.usize),
4278 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
4281 opt_ty.unwrap_or_else(|| self.next_int_var())
4283 ast::LitKind::Float(_, ast::LitFloatType::Suffixed(t)) => tcx.mk_mach_float(t),
4284 ast::LitKind::Float(_, ast::LitFloatType::Unsuffixed) => {
4285 let opt_ty = expected.to_option(self).and_then(|ty| match ty.kind {
4286 ty::Float(_) => Some(ty),
4289 opt_ty.unwrap_or_else(|| self.next_float_var())
4291 ast::LitKind::Bool(_) => tcx.types.bool,
4292 ast::LitKind::Err(_) => tcx.types.err,
4296 /// Unifies the output type with the expected type early, for more coercions
4297 /// and forward type information on the input expressions.
4298 fn expected_inputs_for_expected_output(
4301 expected_ret: Expectation<'tcx>,
4302 formal_ret: Ty<'tcx>,
4303 formal_args: &[Ty<'tcx>],
4304 ) -> Vec<Ty<'tcx>> {
4305 let formal_ret = self.resolve_vars_with_obligations(formal_ret);
4306 let ret_ty = match expected_ret.only_has_type(self) {
4308 None => return Vec::new(),
4310 let expect_args = self
4311 .fudge_inference_if_ok(|| {
4312 // Attempt to apply a subtyping relationship between the formal
4313 // return type (likely containing type variables if the function
4314 // is polymorphic) and the expected return type.
4315 // No argument expectations are produced if unification fails.
4316 let origin = self.misc(call_span);
4317 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
4319 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
4320 // to identity so the resulting type is not constrained.
4323 // Process any obligations locally as much as
4324 // we can. We don't care if some things turn
4325 // out unconstrained or ambiguous, as we're
4326 // just trying to get hints here.
4327 self.save_and_restore_in_snapshot_flag(|_| {
4328 let mut fulfill = TraitEngine::new(self.tcx);
4329 for obligation in ok.obligations {
4330 fulfill.register_predicate_obligation(self, obligation);
4332 fulfill.select_where_possible(self)
4336 Err(_) => return Err(()),
4339 // Record all the argument types, with the substitutions
4340 // produced from the above subtyping unification.
4341 Ok(formal_args.iter().map(|ty| self.resolve_vars_if_possible(ty)).collect())
4343 .unwrap_or_default();
4345 "expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
4346 formal_args, formal_ret, expect_args, expected_ret
4351 pub fn check_struct_path(
4355 ) -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
4356 let path_span = match *qpath {
4357 QPath::Resolved(_, ref path) => path.span,
4358 QPath::TypeRelative(ref qself, _) => qself.span,
4360 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
4361 let variant = match def {
4363 self.set_tainted_by_errors();
4366 Res::Def(DefKind::Variant, _) => match ty.kind {
4367 ty::Adt(adt, substs) => Some((adt.variant_of_res(def), adt.did, substs)),
4368 _ => bug!("unexpected type: {:?}", ty),
4370 Res::Def(DefKind::Struct | DefKind::Union | DefKind::TyAlias | DefKind::AssocTy, _)
4371 | Res::SelfTy(..) => match ty.kind {
4372 ty::Adt(adt, substs) if !adt.is_enum() => {
4373 Some((adt.non_enum_variant(), adt.did, substs))
4377 _ => bug!("unexpected definition: {:?}", def),
4380 if let Some((variant, did, substs)) = variant {
4381 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
4382 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
4384 // Check bounds on type arguments used in the path.
4385 let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
4387 traits::ObligationCause::new(path_span, self.body_id, traits::ItemObligation(did));
4388 self.add_obligations_for_parameters(cause, &bounds);
4396 "expected struct, variant or union type, found {}",
4397 ty.sort_string(self.tcx)
4399 .span_label(path_span, "not a struct")
4405 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4406 // The newly resolved definition is written into `type_dependent_defs`.
4407 fn finish_resolving_struct_path(
4412 ) -> (Res, Ty<'tcx>) {
4414 QPath::Resolved(ref maybe_qself, ref path) => {
4415 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4416 let ty = AstConv::res_to_ty(self, self_ty, path, true);
4419 QPath::TypeRelative(ref qself, ref segment) => {
4420 let ty = self.to_ty(qself);
4422 let res = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.kind {
4428 AstConv::associated_path_to_ty(self, hir_id, path_span, ty, res, segment, true);
4429 let ty = result.map(|(ty, _, _)| ty).unwrap_or(self.tcx().types.err);
4430 let result = result.map(|(_, kind, def_id)| (kind, def_id));
4432 // Write back the new resolution.
4433 self.write_resolution(hir_id, result);
4435 (result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err), ty)
4440 /// Resolves an associated value path into a base type and associated constant, or method
4441 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
4442 pub fn resolve_ty_and_res_ufcs<'b>(
4444 qpath: &'b QPath<'b>,
4447 ) -> (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment<'b>]) {
4448 debug!("resolve_ty_and_res_ufcs: qpath={:?} hir_id={:?} span={:?}", qpath, hir_id, span);
4449 let (ty, qself, item_segment) = match *qpath {
4450 QPath::Resolved(ref opt_qself, ref path) => {
4453 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4457 QPath::TypeRelative(ref qself, ref segment) => (self.to_ty(qself), qself, segment),
4459 if let Some(&cached_result) = self.tables.borrow().type_dependent_defs().get(hir_id) {
4460 // Return directly on cache hit. This is useful to avoid doubly reporting
4461 // errors with default match binding modes. See #44614.
4463 cached_result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err);
4464 return (def, Some(ty), slice::from_ref(&**item_segment));
4466 let item_name = item_segment.ident;
4467 let result = self.resolve_ufcs(span, item_name, ty, hir_id).or_else(|error| {
4468 let result = match error {
4469 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
4470 _ => Err(ErrorReported),
4472 if item_name.name != kw::Invalid {
4473 self.report_method_error(
4477 SelfSource::QPath(qself),
4481 .map(|mut e| e.emit());
4486 // Write back the new resolution.
4487 self.write_resolution(hir_id, result);
4489 result.map(|(kind, def_id)| Res::Def(kind, def_id)).unwrap_or(Res::Err),
4491 slice::from_ref(&**item_segment),
4495 pub fn check_decl_initializer(
4497 local: &'tcx hir::Local<'tcx>,
4498 init: &'tcx hir::Expr<'tcx>,
4500 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
4501 // for #42640 (default match binding modes).
4504 let ref_bindings = local.pat.contains_explicit_ref_binding();
4506 let local_ty = self.local_ty(init.span, local.hir_id).revealed_ty;
4507 if let Some(m) = ref_bindings {
4508 // Somewhat subtle: if we have a `ref` binding in the pattern,
4509 // we want to avoid introducing coercions for the RHS. This is
4510 // both because it helps preserve sanity and, in the case of
4511 // ref mut, for soundness (issue #23116). In particular, in
4512 // the latter case, we need to be clear that the type of the
4513 // referent for the reference that results is *equal to* the
4514 // type of the place it is referencing, and not some
4515 // supertype thereof.
4516 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4517 self.demand_eqtype(init.span, local_ty, init_ty);
4520 self.check_expr_coercable_to_type(init, local_ty)
4524 /// Type check a `let` statement.
4525 pub fn check_decl_local(&self, local: &'tcx hir::Local<'tcx>) {
4526 // Determine and write the type which we'll check the pattern against.
4527 let ty = self.local_ty(local.span, local.hir_id).decl_ty;
4528 self.write_ty(local.hir_id, ty);
4530 // Type check the initializer.
4531 if let Some(ref init) = local.init {
4532 let init_ty = self.check_decl_initializer(local, &init);
4533 self.overwrite_local_ty_if_err(local, ty, init_ty);
4536 // Does the expected pattern type originate from an expression and what is the span?
4537 let (origin_expr, ty_span) = match (local.ty, local.init) {
4538 (Some(ty), _) => (false, Some(ty.span)), // Bias towards the explicit user type.
4539 (_, Some(init)) => (true, Some(init.span)), // No explicit type; so use the scrutinee.
4540 _ => (false, None), // We have `let $pat;`, so the expected type is unconstrained.
4543 // Type check the pattern. Override if necessary to avoid knock-on errors.
4544 self.check_pat_top(&local.pat, ty, ty_span, origin_expr);
4545 let pat_ty = self.node_ty(local.pat.hir_id);
4546 self.overwrite_local_ty_if_err(local, ty, pat_ty);
4549 fn overwrite_local_ty_if_err(
4551 local: &'tcx hir::Local<'tcx>,
4555 if ty.references_error() {
4556 // Override the types everywhere with `types.err` to avoid knock on errors.
4557 self.write_ty(local.hir_id, ty);
4558 self.write_ty(local.pat.hir_id, ty);
4559 let local_ty = LocalTy { decl_ty, revealed_ty: ty };
4560 self.locals.borrow_mut().insert(local.hir_id, local_ty);
4561 self.locals.borrow_mut().insert(local.pat.hir_id, local_ty);
4565 fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) {
4566 err.span_suggestion_short(
4567 span.shrink_to_hi(),
4568 "consider using a semicolon here",
4570 Applicability::MachineApplicable,
4574 pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>) {
4575 // Don't do all the complex logic below for `DeclItem`.
4577 hir::StmtKind::Item(..) => return,
4578 hir::StmtKind::Local(..) | hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
4581 self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
4583 // Hide the outer diverging and `has_errors` flags.
4584 let old_diverges = self.diverges.replace(Diverges::Maybe);
4585 let old_has_errors = self.has_errors.replace(false);
4588 hir::StmtKind::Local(ref l) => {
4589 self.check_decl_local(&l);
4592 hir::StmtKind::Item(_) => {}
4593 hir::StmtKind::Expr(ref expr) => {
4594 // Check with expected type of `()`.
4595 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
4596 self.suggest_semicolon_at_end(expr.span, err);
4599 hir::StmtKind::Semi(ref expr) => {
4600 self.check_expr(&expr);
4604 // Combine the diverging and `has_error` flags.
4605 self.diverges.set(self.diverges.get() | old_diverges);
4606 self.has_errors.set(self.has_errors.get() | old_has_errors);
4609 pub fn check_block_no_value(&self, blk: &'tcx hir::Block<'tcx>) {
4610 let unit = self.tcx.mk_unit();
4611 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4613 // if the block produces a `!` value, that can always be
4614 // (effectively) coerced to unit.
4616 self.demand_suptype(blk.span, unit, ty);
4620 /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
4621 /// expression's `Span`, otherwise return `expr.span`. This is done to give better errors
4622 /// when given code like the following:
4624 /// if false { return 0i32; } else { 1u32 }
4625 /// // ^^^^ point at this instead of the whole `if` expression
4627 fn get_expr_coercion_span(&self, expr: &hir::Expr<'_>) -> rustc_span::Span {
4628 if let hir::ExprKind::Match(_, arms, _) = &expr.kind {
4629 let arm_spans: Vec<Span> = arms
4632 self.in_progress_tables
4633 .and_then(|tables| tables.borrow().node_type_opt(arm.body.hir_id))
4634 .and_then(|arm_ty| {
4635 if arm_ty.is_never() {
4638 Some(match &arm.body.kind {
4639 // Point at the tail expression when possible.
4640 hir::ExprKind::Block(block, _) => {
4641 block.expr.as_ref().map(|e| e.span).unwrap_or(block.span)
4649 if arm_spans.len() == 1 {
4650 return arm_spans[0];
4656 fn check_block_with_expected(
4658 blk: &'tcx hir::Block<'tcx>,
4659 expected: Expectation<'tcx>,
4662 let mut fcx_ps = self.ps.borrow_mut();
4663 let unsafety_state = fcx_ps.recurse(blk);
4664 replace(&mut *fcx_ps, unsafety_state)
4667 // In some cases, blocks have just one exit, but other blocks
4668 // can be targeted by multiple breaks. This can happen both
4669 // with labeled blocks as well as when we desugar
4670 // a `try { ... }` expression.
4674 // 'a: { if true { break 'a Err(()); } Ok(()) }
4676 // Here we would wind up with two coercions, one from
4677 // `Err(())` and the other from the tail expression
4678 // `Ok(())`. If the tail expression is omitted, that's a
4679 // "forced unit" -- unless the block diverges, in which
4680 // case we can ignore the tail expression (e.g., `'a: {
4681 // break 'a 22; }` would not force the type of the block
4683 let tail_expr = blk.expr.as_ref();
4684 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4685 let coerce = if blk.targeted_by_break {
4686 CoerceMany::new(coerce_to_ty)
4688 let tail_expr: &[&hir::Expr<'_>] = match tail_expr {
4689 Some(e) => slice::from_ref(e),
4692 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4695 let prev_diverges = self.diverges.get();
4696 let ctxt = BreakableCtxt { coerce: Some(coerce), may_break: false };
4698 let (ctxt, ()) = self.with_breakable_ctxt(blk.hir_id, ctxt, || {
4699 for s in blk.stmts {
4703 // check the tail expression **without** holding the
4704 // `enclosing_breakables` lock below.
4705 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4707 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4708 let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
4709 let coerce = ctxt.coerce.as_mut().unwrap();
4710 if let Some(tail_expr_ty) = tail_expr_ty {
4711 let tail_expr = tail_expr.unwrap();
4712 let span = self.get_expr_coercion_span(tail_expr);
4713 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
4714 coerce.coerce(self, &cause, tail_expr, tail_expr_ty);
4716 // Subtle: if there is no explicit tail expression,
4717 // that is typically equivalent to a tail expression
4718 // of `()` -- except if the block diverges. In that
4719 // case, there is no value supplied from the tail
4720 // expression (assuming there are no other breaks,
4721 // this implies that the type of the block will be
4724 // #41425 -- label the implicit `()` as being the
4725 // "found type" here, rather than the "expected type".
4726 if !self.diverges.get().is_always() {
4727 // #50009 -- Do not point at the entire fn block span, point at the return type
4728 // span, as it is the cause of the requirement, and
4729 // `consider_hint_about_removing_semicolon` will point at the last expression
4730 // if it were a relevant part of the error. This improves usability in editors
4731 // that highlight errors inline.
4732 let mut sp = blk.span;
4733 let mut fn_span = None;
4734 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.hir_id) {
4735 let ret_sp = decl.output.span();
4736 if let Some(block_sp) = self.parent_item_span(blk.hir_id) {
4737 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4738 // output would otherwise be incorrect and even misleading. Make sure
4739 // the span we're aiming at correspond to a `fn` body.
4740 if block_sp == blk.span {
4742 fn_span = Some(ident.span);
4746 coerce.coerce_forced_unit(
4750 if let Some(expected_ty) = expected.only_has_type(self) {
4751 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4753 if let Some(fn_span) = fn_span {
4756 "implicitly returns `()` as its body has no tail or `return` \
4768 // If we can break from the block, then the block's exit is always reachable
4769 // (... as long as the entry is reachable) - regardless of the tail of the block.
4770 self.diverges.set(prev_diverges);
4773 let mut ty = ctxt.coerce.unwrap().complete(self);
4775 if self.has_errors.get() || ty.references_error() {
4776 ty = self.tcx.types.err
4779 self.write_ty(blk.hir_id, ty);
4781 *self.ps.borrow_mut() = prev;
4785 fn parent_item_span(&self, id: hir::HirId) -> Option<Span> {
4786 let node = self.tcx.hir().get(self.tcx.hir().get_parent_item(id));
4788 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })
4789 | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(_, body_id), .. }) => {
4790 let body = self.tcx.hir().body(body_id);
4791 if let ExprKind::Block(block, _) = &body.value.kind {
4792 return Some(block.span);
4800 /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
4801 fn get_parent_fn_decl(
4804 ) -> Option<(&'tcx hir::FnDecl<'tcx>, ast::Ident)> {
4805 let parent = self.tcx.hir().get(self.tcx.hir().get_parent_item(blk_id));
4806 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
4809 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
4810 fn get_node_fn_decl(
4813 ) -> Option<(&'tcx hir::FnDecl<'tcx>, ast::Ident, bool)> {
4815 Node::Item(&hir::Item { ident, kind: hir::ItemKind::Fn(ref sig, ..), .. }) => {
4816 // This is less than ideal, it will not suggest a return type span on any
4817 // method called `main`, regardless of whether it is actually the entry point,
4818 // but it will still present it as the reason for the expected type.
4819 Some((&sig.decl, ident, ident.name != sym::main))
4821 Node::TraitItem(&hir::TraitItem {
4823 kind: hir::TraitItemKind::Fn(ref sig, ..),
4825 }) => Some((&sig.decl, ident, true)),
4826 Node::ImplItem(&hir::ImplItem {
4828 kind: hir::ImplItemKind::Fn(ref sig, ..),
4830 }) => Some((&sig.decl, ident, false)),
4835 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
4836 /// suggestion can be made, `None` otherwise.
4837 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, bool)> {
4838 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
4839 // `while` before reaching it, as block tail returns are not available in them.
4840 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
4841 let parent = self.tcx.hir().get(blk_id);
4842 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
4846 /// On implicit return expressions with mismatched types, provides the following suggestions:
4848 /// - Points out the method's return type as the reason for the expected type.
4849 /// - Possible missing semicolon.
4850 /// - Possible missing return type if the return type is the default, and not `fn main()`.
4851 pub fn suggest_mismatched_types_on_tail(
4853 err: &mut DiagnosticBuilder<'_>,
4854 expr: &'tcx hir::Expr<'tcx>,
4860 let expr = expr.peel_drop_temps();
4861 self.suggest_missing_semicolon(err, expr, expected, cause_span);
4862 let mut pointing_at_return_type = false;
4863 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
4864 pointing_at_return_type =
4865 self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest);
4867 pointing_at_return_type
4870 /// When encountering an fn-like ctor that needs to unify with a value, check whether calling
4871 /// the ctor would successfully solve the type mismatch and if so, suggest it:
4873 /// fn foo(x: usize) -> usize { x }
4874 /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)`
4878 err: &mut DiagnosticBuilder<'_>,
4879 expr: &hir::Expr<'_>,
4883 let hir = self.tcx.hir();
4884 let (def_id, sig) = match found.kind {
4885 ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)),
4886 ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig()),
4890 let sig = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig).0;
4891 let sig = self.normalize_associated_types_in(expr.span, &sig);
4892 if self.can_coerce(sig.output(), expected) {
4893 let (mut sugg_call, applicability) = if sig.inputs().is_empty() {
4894 (String::new(), Applicability::MachineApplicable)
4896 ("...".to_string(), Applicability::HasPlaceholders)
4898 let mut msg = "call this function";
4899 match hir.get_if_local(def_id) {
4901 Node::Item(hir::Item { kind: ItemKind::Fn(.., body_id), .. })
4902 | Node::ImplItem(hir::ImplItem {
4903 kind: hir::ImplItemKind::Fn(_, body_id), ..
4905 | Node::TraitItem(hir::TraitItem {
4906 kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Provided(body_id)),
4910 let body = hir.body(*body_id);
4914 .map(|param| match ¶m.pat.kind {
4915 hir::PatKind::Binding(_, _, ident, None)
4916 if ident.name != kw::SelfLower =>
4920 _ => "_".to_string(),
4922 .collect::<Vec<_>>()
4925 Some(Node::Expr(hir::Expr {
4926 kind: ExprKind::Closure(_, _, body_id, _, _),
4927 span: full_closure_span,
4930 if *full_closure_span == expr.span {
4933 msg = "call this closure";
4934 let body = hir.body(*body_id);
4938 .map(|param| match ¶m.pat.kind {
4939 hir::PatKind::Binding(_, _, ident, None)
4940 if ident.name != kw::SelfLower =>
4944 _ => "_".to_string(),
4946 .collect::<Vec<_>>()
4949 Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => {
4950 sugg_call = fields.iter().map(|_| "_").collect::<Vec<_>>().join(", ");
4951 match hir.as_local_hir_id(def_id).and_then(|hir_id| hir.def_kind(hir_id)) {
4952 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Variant, _)) => {
4953 msg = "instantiate this tuple variant";
4955 Some(hir::def::DefKind::Ctor(hir::def::CtorOf::Struct, _)) => {
4956 msg = "instantiate this tuple struct";
4961 Some(Node::ForeignItem(hir::ForeignItem {
4962 kind: hir::ForeignItemKind::Fn(_, idents, _),
4968 if ident.name != kw::SelfLower {
4974 .collect::<Vec<_>>()
4977 Some(Node::TraitItem(hir::TraitItem {
4978 kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Required(idents)),
4984 if ident.name != kw::SelfLower {
4990 .collect::<Vec<_>>()
4995 err.span_suggestion_verbose(
4996 expr.span.shrink_to_hi(),
4997 &format!("use parentheses to {}", msg),
4998 format!("({})", sugg_call),
5006 pub fn suggest_ref_or_into(
5008 err: &mut DiagnosticBuilder<'_>,
5009 expr: &hir::Expr<'_>,
5013 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
5014 err.span_suggestion(sp, msg, suggestion, Applicability::MachineApplicable);
5015 } else if let (ty::FnDef(def_id, ..), true) =
5016 (&found.kind, self.suggest_fn_call(err, expr, expected, found))
5018 if let Some(sp) = self.tcx.hir().span_if_local(*def_id) {
5019 let sp = self.sess().source_map().guess_head_span(sp);
5020 err.span_label(sp, &format!("{} defined here", found));
5022 } else if !self.check_for_cast(err, expr, found, expected) {
5023 let is_struct_pat_shorthand_field =
5024 self.is_hir_id_from_struct_pattern_shorthand_field(expr.hir_id, expr.span);
5025 let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id);
5026 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
5027 let mut suggestions = iter::repeat(&expr_text)
5028 .zip(methods.iter())
5029 .filter_map(|(receiver, method)| {
5030 let method_call = format!(".{}()", method.ident);
5031 if receiver.ends_with(&method_call) {
5032 None // do not suggest code that is already there (#53348)
5034 let method_call_list = [".to_vec()", ".to_string()"];
5035 let sugg = if receiver.ends_with(".clone()")
5036 && method_call_list.contains(&method_call.as_str())
5038 let max_len = receiver.rfind('.').unwrap();
5039 format!("{}{}", &receiver[..max_len], method_call)
5041 if expr.precedence().order() < ExprPrecedence::MethodCall.order() {
5042 format!("({}){}", receiver, method_call)
5044 format!("{}{}", receiver, method_call)
5047 Some(if is_struct_pat_shorthand_field {
5048 format!("{}: {}", receiver, sugg)
5055 if suggestions.peek().is_some() {
5056 err.span_suggestions(
5058 "try using a conversion method",
5060 Applicability::MaybeIncorrect,
5067 /// When encountering the expected boxed value allocated in the stack, suggest allocating it
5068 /// in the heap by calling `Box::new()`.
5069 fn suggest_boxing_when_appropriate(
5071 err: &mut DiagnosticBuilder<'_>,
5072 expr: &hir::Expr<'_>,
5076 if self.tcx.hir().is_const_context(expr.hir_id) {
5077 // Do not suggest `Box::new` in const context.
5080 if !expected.is_box() || found.is_box() {
5083 let boxed_found = self.tcx.mk_box(found);
5084 if let (true, Ok(snippet)) = (
5085 self.can_coerce(boxed_found, expected),
5086 self.sess().source_map().span_to_snippet(expr.span),
5088 err.span_suggestion(
5090 "store this in the heap by calling `Box::new`",
5091 format!("Box::new({})", snippet),
5092 Applicability::MachineApplicable,
5095 "for more on the distinction between the stack and the heap, read \
5096 https://doc.rust-lang.org/book/ch15-01-box.html, \
5097 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
5098 https://doc.rust-lang.org/std/boxed/index.html",
5103 /// When encountering an `impl Future` where `BoxFuture` is expected, suggest `Box::pin`.
5104 fn suggest_calling_boxed_future_when_appropriate(
5106 err: &mut DiagnosticBuilder<'_>,
5107 expr: &hir::Expr<'_>,
5113 if self.tcx.hir().is_const_context(expr.hir_id) {
5114 // Do not suggest `Box::new` in const context.
5117 let pin_did = self.tcx.lang_items().pin_type();
5118 match expected.kind {
5119 ty::Adt(def, _) if Some(def.did) != pin_did => return false,
5120 // This guards the `unwrap` and `mk_box` below.
5121 _ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return false,
5124 let boxed_found = self.tcx.mk_box(found);
5125 let new_found = self.tcx.mk_lang_item(boxed_found, lang_items::PinTypeLangItem).unwrap();
5126 if let (true, Ok(snippet)) = (
5127 self.can_coerce(new_found, expected),
5128 self.sess().source_map().span_to_snippet(expr.span),
5131 ty::Adt(def, _) if def.is_box() => {
5132 err.help("use `Box::pin`");
5135 err.span_suggestion(
5137 "you need to pin and box this expression",
5138 format!("Box::pin({})", snippet),
5139 Applicability::MachineApplicable,
5149 /// A common error is to forget to add a semicolon at the end of a block, e.g.,
5153 /// bar_that_returns_u32()
5157 /// This routine checks if the return expression in a block would make sense on its own as a
5158 /// statement and the return type has been left as default or has been specified as `()`. If so,
5159 /// it suggests adding a semicolon.
5160 fn suggest_missing_semicolon(
5162 err: &mut DiagnosticBuilder<'_>,
5163 expression: &'tcx hir::Expr<'tcx>,
5167 if expected.is_unit() {
5168 // `BlockTailExpression` only relevant if the tail expr would be
5169 // useful on its own.
5170 match expression.kind {
5172 | ExprKind::MethodCall(..)
5173 | ExprKind::Loop(..)
5174 | ExprKind::Match(..)
5175 | ExprKind::Block(..) => {
5176 err.span_suggestion(
5177 cause_span.shrink_to_hi(),
5178 "try adding a semicolon",
5180 Applicability::MachineApplicable,
5188 /// A possible error is to forget to add a return type that is needed:
5192 /// bar_that_returns_u32()
5196 /// This routine checks if the return type is left as default, the method is not part of an
5197 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
5199 fn suggest_missing_return_type(
5201 err: &mut DiagnosticBuilder<'_>,
5202 fn_decl: &hir::FnDecl<'_>,
5207 // Only suggest changing the return type for methods that
5208 // haven't set a return type at all (and aren't `fn main()` or an impl).
5209 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
5210 (&hir::FnRetTy::DefaultReturn(span), true, true, true) => {
5211 err.span_suggestion(
5213 "try adding a return type",
5214 format!("-> {} ", self.resolve_vars_with_obligations(found)),
5215 Applicability::MachineApplicable,
5219 (&hir::FnRetTy::DefaultReturn(span), false, true, true) => {
5220 err.span_label(span, "possibly return type missing here?");
5223 (&hir::FnRetTy::DefaultReturn(span), _, false, true) => {
5224 // `fn main()` must return `()`, do not suggest changing return type
5225 err.span_label(span, "expected `()` because of default return type");
5228 // expectation was caused by something else, not the default return
5229 (&hir::FnRetTy::DefaultReturn(_), _, _, false) => false,
5230 (&hir::FnRetTy::Return(ref ty), _, _, _) => {
5231 // Only point to return type if the expected type is the return type, as if they
5232 // are not, the expectation must have been caused by something else.
5233 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
5235 let ty = AstConv::ast_ty_to_ty(self, ty);
5236 debug!("suggest_missing_return_type: return type {:?}", ty);
5237 debug!("suggest_missing_return_type: expected type {:?}", ty);
5238 if ty.kind == expected.kind {
5239 err.span_label(sp, format!("expected `{}` because of return type", expected));
5247 /// A possible error is to forget to add `.await` when using futures:
5250 /// async fn make_u32() -> u32 {
5254 /// fn take_u32(x: u32) {}
5256 /// async fn foo() {
5257 /// let x = make_u32();
5262 /// This routine checks if the found type `T` implements `Future<Output=U>` where `U` is the
5263 /// expected type. If this is the case, and we are inside of an async body, it suggests adding
5264 /// `.await` to the tail of the expression.
5265 fn suggest_missing_await(
5267 err: &mut DiagnosticBuilder<'_>,
5268 expr: &hir::Expr<'_>,
5272 // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the
5273 // body isn't `async`.
5274 let item_id = self.tcx().hir().get_parent_node(self.body_id);
5275 if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) {
5276 let body = self.tcx().hir().body(body_id);
5277 if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind {
5279 // Check for `Future` implementations by constructing a predicate to
5280 // prove: `<T as Future>::Output == U`
5281 let future_trait = self.tcx.lang_items().future_trait().unwrap();
5282 let item_def_id = self
5284 .associated_items(future_trait)
5285 .in_definition_order()
5290 ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
5291 // `<T as Future>::Output`
5292 projection_ty: ty::ProjectionTy {
5294 substs: self.tcx.mk_substs_trait(
5296 self.fresh_substs_for_item(sp, item_def_id),
5303 let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
5304 debug!("suggest_missing_await: trying obligation {:?}", obligation);
5305 if self.infcx.predicate_may_hold(&obligation) {
5306 debug!("suggest_missing_await: obligation held: {:?}", obligation);
5307 if let Ok(code) = self.sess().source_map().span_to_snippet(sp) {
5308 err.span_suggestion(
5310 "consider using `.await` here",
5311 format!("{}.await", code),
5312 Applicability::MaybeIncorrect,
5315 debug!("suggest_missing_await: no snippet for {:?}", sp);
5318 debug!("suggest_missing_await: obligation did not hold: {:?}", obligation)
5324 /// A common error is to add an extra semicolon:
5327 /// fn foo() -> usize {
5332 /// This routine checks if the final statement in a block is an
5333 /// expression with an explicit semicolon whose type is compatible
5334 /// with `expected_ty`. If so, it suggests removing the semicolon.
5335 fn consider_hint_about_removing_semicolon(
5337 blk: &'tcx hir::Block<'tcx>,
5338 expected_ty: Ty<'tcx>,
5339 err: &mut DiagnosticBuilder<'_>,
5341 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
5342 err.span_suggestion(
5344 "consider removing this semicolon",
5346 Applicability::MachineApplicable,
5351 fn could_remove_semicolon(
5353 blk: &'tcx hir::Block<'tcx>,
5354 expected_ty: Ty<'tcx>,
5356 // Be helpful when the user wrote `{... expr;}` and
5357 // taking the `;` off is enough to fix the error.
5358 let last_stmt = blk.stmts.last()?;
5359 let last_expr = match last_stmt.kind {
5360 hir::StmtKind::Semi(ref e) => e,
5363 let last_expr_ty = self.node_ty(last_expr.hir_id);
5364 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
5367 let original_span = original_sp(last_stmt.span, blk.span);
5368 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
5371 // Instantiates the given path, which must refer to an item with the given
5372 // number of type parameters and type.
5373 pub fn instantiate_value_path(
5375 segments: &[hir::PathSegment<'_>],
5376 self_ty: Option<Ty<'tcx>>,
5380 ) -> (Ty<'tcx>, Res) {
5382 "instantiate_value_path(segments={:?}, self_ty={:?}, res={:?}, hir_id={})",
5383 segments, self_ty, res, hir_id,
5388 let path_segs = match res {
5389 Res::Local(_) | Res::SelfCtor(_) => vec![],
5390 Res::Def(kind, def_id) => {
5391 AstConv::def_ids_for_value_path_segments(self, segments, self_ty, kind, def_id)
5393 _ => bug!("instantiate_value_path on {:?}", res),
5396 let mut user_self_ty = None;
5397 let mut is_alias_variant_ctor = false;
5399 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _) => {
5400 if let Some(self_ty) = self_ty {
5401 let adt_def = self_ty.ty_adt_def().unwrap();
5402 user_self_ty = Some(UserSelfTy { impl_def_id: adt_def.did, self_ty });
5403 is_alias_variant_ctor = true;
5406 Res::Def(DefKind::AssocFn | DefKind::AssocConst, def_id) => {
5407 let container = tcx.associated_item(def_id).container;
5408 debug!("instantiate_value_path: def_id={:?} container={:?}", def_id, container);
5410 ty::TraitContainer(trait_did) => {
5411 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
5413 ty::ImplContainer(impl_def_id) => {
5414 if segments.len() == 1 {
5415 // `<T>::assoc` will end up here, and so
5416 // can `T::assoc`. It this came from an
5417 // inherent impl, we need to record the
5418 // `T` for posterity (see `UserSelfTy` for
5420 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
5421 user_self_ty = Some(UserSelfTy { impl_def_id, self_ty });
5429 // Now that we have categorized what space the parameters for each
5430 // segment belong to, let's sort out the parameters that the user
5431 // provided (if any) into their appropriate spaces. We'll also report
5432 // errors if type parameters are provided in an inappropriate place.
5434 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
5435 let generics_has_err = AstConv::prohibit_generics(
5437 segments.iter().enumerate().filter_map(|(index, seg)| {
5438 if !generic_segs.contains(&index) || is_alias_variant_ctor {
5446 if let Res::Local(hid) = res {
5447 let ty = self.local_ty(span, hid).decl_ty;
5448 let ty = self.normalize_associated_types_in(span, &ty);
5449 self.write_ty(hir_id, ty);
5453 if generics_has_err {
5454 // Don't try to infer type parameters when prohibited generic arguments were given.
5455 user_self_ty = None;
5458 // Now we have to compare the types that the user *actually*
5459 // provided against the types that were *expected*. If the user
5460 // did not provide any types, then we want to substitute inference
5461 // variables. If the user provided some types, we may still need
5462 // to add defaults. If the user provided *too many* types, that's
5465 let mut infer_args_for_err = FxHashSet::default();
5466 for &PathSeg(def_id, index) in &path_segs {
5467 let seg = &segments[index];
5468 let generics = tcx.generics_of(def_id);
5469 // Argument-position `impl Trait` is treated as a normal generic
5470 // parameter internally, but we don't allow users to specify the
5471 // parameter's value explicitly, so we have to do some error-
5473 if let Err(GenericArgCountMismatch { reported: Some(ErrorReported), .. }) =
5474 AstConv::check_generic_arg_count_for_call(
5475 tcx, span, &generics, &seg, false, // `is_method_call`
5478 infer_args_for_err.insert(index);
5479 self.set_tainted_by_errors(); // See issue #53251.
5483 let has_self = path_segs
5485 .map(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self)
5488 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
5489 let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id));
5491 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
5492 let variant = adt_def.non_enum_variant();
5493 let ctor_def_id = variant.ctor_def_id.unwrap();
5495 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
5500 let mut err = tcx.sess.struct_span_err(
5502 "the `Self` constructor can only be used with tuple or unit structs",
5504 if let Some(adt_def) = ty.ty_adt_def() {
5505 match adt_def.adt_kind() {
5507 err.help("did you mean to use one of the enum's variants?");
5509 AdtKind::Struct | AdtKind::Union => {
5510 err.span_suggestion(
5512 "use curly brackets",
5513 String::from("Self { /* fields */ }"),
5514 Applicability::HasPlaceholders,
5521 return (tcx.types.err, res);
5527 let def_id = res.def_id();
5529 // The things we are substituting into the type should not contain
5530 // escaping late-bound regions, and nor should the base type scheme.
5531 let ty = tcx.type_of(def_id);
5533 let substs = self_ctor_substs.unwrap_or_else(|| {
5534 AstConv::create_substs_for_generic_args(
5540 infer_args_for_err.is_empty(),
5541 // Provide the generic args, and whether types should be inferred.
5543 if let Some(&PathSeg(_, index)) =
5544 path_segs.iter().find(|&PathSeg(did, _)| *did == def_id)
5546 // If we've encountered an `impl Trait`-related error, we're just
5547 // going to infer the arguments for better error messages.
5548 if !infer_args_for_err.contains(&index) {
5549 // Check whether the user has provided generic arguments.
5550 if let Some(ref data) = segments[index].args {
5551 return (Some(data), segments[index].infer_args);
5554 return (None, segments[index].infer_args);
5559 // Provide substitutions for parameters for which (valid) arguments have been provided.
5560 |param, arg| match (¶m.kind, arg) {
5561 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
5562 AstConv::ast_region_to_region(self, lt, Some(param)).into()
5564 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
5565 self.to_ty(ty).into()
5567 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
5568 self.to_const(&ct.value).into()
5570 _ => unreachable!(),
5572 // Provide substitutions for parameters for which arguments are inferred.
5573 |substs, param, infer_args| {
5575 GenericParamDefKind::Lifetime => {
5576 self.re_infer(Some(param), span).unwrap().into()
5578 GenericParamDefKind::Type { has_default, .. } => {
5579 if !infer_args && has_default {
5580 // If we have a default, then we it doesn't matter that we're not
5581 // inferring the type arguments: we provide the default where any
5583 let default = tcx.type_of(param.def_id);
5586 default.subst_spanned(tcx, substs.unwrap(), Some(span)),
5590 // If no type arguments were provided, we have to infer them.
5591 // This case also occurs as a result of some malformed input, e.g.
5592 // a lifetime argument being given instead of a type parameter.
5593 // Using inference instead of `Error` gives better error messages.
5594 self.var_for_def(span, param)
5597 GenericParamDefKind::Const => {
5598 // FIXME(const_generics:defaults)
5599 // No const parameters were provided, we have to infer them.
5600 self.var_for_def(span, param)
5606 assert!(!substs.has_escaping_bound_vars());
5607 assert!(!ty.has_escaping_bound_vars());
5609 // First, store the "user substs" for later.
5610 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
5612 self.add_required_obligations(span, def_id, &substs);
5614 // Substitute the values for the type parameters into the type of
5615 // the referenced item.
5616 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
5618 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
5619 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
5620 // is inherent, there is no `Self` parameter; instead, the impl needs
5621 // type parameters, which we can infer by unifying the provided `Self`
5622 // with the substituted impl type.
5623 // This also occurs for an enum variant on a type alias.
5624 let ty = tcx.type_of(impl_def_id);
5626 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
5627 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
5628 Ok(ok) => self.register_infer_ok_obligations(ok),
5630 self.tcx.sess.delay_span_bug(
5633 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
5642 self.check_rustc_args_require_const(def_id, hir_id, span);
5644 debug!("instantiate_value_path: type of {:?} is {:?}", hir_id, ty_substituted);
5645 self.write_substs(hir_id, substs);
5647 (ty_substituted, res)
5650 /// Add all the obligations that are required, substituting and normalized appropriately.
5651 fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
5652 let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);
5654 for (i, mut obligation) in traits::predicates_for_generics(
5655 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
5662 // This makes the error point at the bound, but we want to point at the argument
5663 if let Some(span) = spans.get(i) {
5664 obligation.cause.code = traits::BindingObligation(def_id, *span);
5666 self.register_predicate(obligation);
5670 fn check_rustc_args_require_const(&self, def_id: DefId, hir_id: hir::HirId, span: Span) {
5671 // We're only interested in functions tagged with
5672 // #[rustc_args_required_const], so ignore anything that's not.
5673 if !self.tcx.has_attr(def_id, sym::rustc_args_required_const) {
5677 // If our calling expression is indeed the function itself, we're good!
5678 // If not, generate an error that this can only be called directly.
5679 if let Node::Expr(expr) = self.tcx.hir().get(self.tcx.hir().get_parent_node(hir_id)) {
5680 if let ExprKind::Call(ref callee, ..) = expr.kind {
5681 if callee.hir_id == hir_id {
5687 self.tcx.sess.span_err(
5689 "this function can only be invoked directly, not through a function pointer",
5693 /// Resolves `typ` by a single level if `typ` is a type variable.
5694 /// If no resolution is possible, then an error is reported.
5695 /// Numeric inference variables may be left unresolved.
5696 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5697 let ty = self.resolve_vars_with_obligations(ty);
5698 if !ty.is_ty_var() {
5701 if !self.is_tainted_by_errors() {
5702 self.need_type_info_err((**self).body_id, sp, ty, E0282)
5703 .note("type must be known at this point")
5706 self.demand_suptype(sp, self.tcx.types.err, ty);
5711 fn with_breakable_ctxt<F: FnOnce() -> R, R>(
5714 ctxt: BreakableCtxt<'tcx>,
5716 ) -> (BreakableCtxt<'tcx>, R) {
5719 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5720 index = enclosing_breakables.stack.len();
5721 enclosing_breakables.by_id.insert(id, index);
5722 enclosing_breakables.stack.push(ctxt);
5726 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5727 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5728 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5729 enclosing_breakables.stack.pop().expect("missing breakable context")
5734 /// Instantiate a QueryResponse in a probe context, without a
5735 /// good ObligationCause.
5736 fn probe_instantiate_query_response(
5739 original_values: &OriginalQueryValues<'tcx>,
5740 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5741 ) -> InferResult<'tcx, Ty<'tcx>> {
5742 self.instantiate_query_response_and_region_obligations(
5743 &traits::ObligationCause::misc(span, self.body_id),
5750 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
5751 fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
5752 let mut contained_in_place = false;
5754 while let hir::Node::Expr(parent_expr) =
5755 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5757 match &parent_expr.kind {
5758 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5759 if lhs.hir_id == expr_id {
5760 contained_in_place = true;
5766 expr_id = parent_expr.hir_id;
5773 fn check_type_params_are_used<'tcx>(tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>) {
5774 debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty);
5776 assert_eq!(generics.parent, None);
5778 if generics.own_counts().types == 0 {
5782 let mut params_used = BitSet::new_empty(generics.params.len());
5784 if ty.references_error() {
5785 // If there is already another error, do not emit
5786 // an error for not using a type parameter.
5787 assert!(tcx.sess.has_errors());
5791 for leaf in ty.walk() {
5792 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
5793 if let ty::Param(param) = leaf_ty.kind {
5794 debug!("found use of ty param {:?}", param);
5795 params_used.insert(param.index);
5800 for param in &generics.params {
5801 if !params_used.contains(param.index) {
5802 if let ty::GenericParamDefKind::Type { .. } = param.kind {
5803 let span = tcx.def_span(param.def_id);
5808 "type parameter `{}` is unused",
5811 .span_label(span, "unused type parameter")
5818 fn fatally_break_rust(sess: &Session) {
5819 let handler = sess.diagnostic();
5820 handler.span_bug_no_panic(
5822 "It looks like you're trying to break rust; would you like some ICE?",
5824 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5825 handler.note_without_error(
5826 "we would appreciate a joke overview: \
5827 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675",
5829 handler.note_without_error(&format!(
5830 "rustc {} running on {}",
5831 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5832 config::host_triple(),
5836 fn potentially_plural_count(count: usize, word: &str) -> String {
5837 format!("{} {}{}", count, word, pluralize!(count))