5 Within the check phase of type check, we check each item one at a time
6 (bodies of function expressions are checked as part of the containing
7 function). Inference is used to supply types wherever they are unknown.
9 By far the most complex case is checking the body of a function. This
10 can be broken down into several distinct phases:
12 - gather: creates type variables to represent the type of each local
13 variable and pattern binding.
15 - main: the main pass does the lion's share of the work: it
16 determines the types of all expressions, resolves
17 methods, checks for most invalid conditions, and so forth. In
18 some cases, where a type is unknown, it may create a type or region
19 variable and use that as the type of an expression.
21 In the process of checking, various constraints will be placed on
22 these type variables through the subtyping relationships requested
23 through the `demand` module. The `infer` module is in charge
24 of resolving those constraints.
26 - regionck: after main is complete, the regionck pass goes over all
27 types looking for regions and making sure that they did not escape
28 into places they are not in scope. This may also influence the
29 final assignments of the various region variables if there is some
32 - vtable: find and records the impls to use for each trait bound that
33 appears on a type parameter.
35 - writeback: writes the final types within a function body, replacing
36 type variables with their final inferred types. These final types
37 are written into the `tcx.node_types` table, which should *never* contain
38 any reference to a type variable.
42 While type checking a function, the intermediate types for the
43 expressions, blocks, and so forth contained within the function are
44 stored in `fcx.node_types` and `fcx.node_substs`. These types
45 may contain unresolved type variables. After type checking is
46 complete, the functions in the writeback module are used to take the
47 types from this table, resolve them, and then write them into their
48 permanent home in the type context `tcx`.
50 This means that during inferencing you should use `fcx.write_ty()`
51 and `fcx.expr_ty()` / `fcx.node_ty()` to write/obtain the types of
52 nodes within the function.
54 The types of top-level items, which never contain unbound type
55 variables, are stored directly into the `tcx` tables.
57 N.B., a type variable is not the same thing as a type parameter. A
58 type variable is rather an "instance" of a type parameter: that is,
59 given a generic function `fn foo<T>(t: T)`: while checking the
60 function `foo`, the type `ty_param(0)` refers to the type `T`, which
61 is treated in abstract. When `foo()` is called, however, `T` will be
62 substituted for a fresh type variable `N`. This variable will
63 eventually be resolved to some concrete type (which might itself be
82 mod generator_interior;
86 use astconv::{AstConv, PathSeg};
87 use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
88 use rustc::hir::{self, ExprKind, GenericArg, ItemKind, Node, PatKind, QPath};
89 use rustc::hir::def::{CtorKind, Def};
90 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
91 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
92 use rustc::hir::itemlikevisit::ItemLikeVisitor;
93 use middle::lang_items;
94 use namespace::Namespace;
95 use rustc::infer::{self, InferCtxt, InferOk, InferResult, RegionVariableOrigin};
96 use rustc::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
97 use rustc_data_structures::indexed_vec::Idx;
98 use rustc_data_structures::sync::Lrc;
99 use rustc_target::spec::abi::Abi;
100 use rustc::infer::opaque_types::OpaqueTypeDecl;
101 use rustc::infer::type_variable::{TypeVariableOrigin};
102 use rustc::middle::region;
103 use rustc::mir::interpret::{ConstValue, GlobalId};
104 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
106 self, AdtKind, CanonicalUserTypeAnnotation, Ty, TyCtxt, GenericParamDefKind, Visibility,
107 ToPolyTraitRef, ToPredicate, RegionKind, UserTypeAnnotation
109 use rustc::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
110 use rustc::ty::fold::TypeFoldable;
111 use rustc::ty::query::Providers;
112 use rustc::ty::query::queries;
113 use rustc::ty::subst::{UnpackedKind, Subst, Substs, UserSelfTy, UserSubsts};
114 use rustc::ty::util::{Representability, IntTypeExt, Discr};
115 use rustc::ty::layout::VariantIdx;
116 use syntax_pos::{self, BytePos, Span, MultiSpan};
119 use syntax::feature_gate::{GateIssue, emit_feature_err};
121 use syntax::source_map::{DUMMY_SP, original_sp};
122 use syntax::symbol::{Symbol, LocalInternedString, keywords};
123 use syntax::util::lev_distance::find_best_match_for_name;
125 use std::cell::{Cell, RefCell, Ref, RefMut};
126 use std::collections::hash_map::Entry;
128 use std::fmt::Display;
130 use std::mem::replace;
131 use std::ops::{self, Deref};
134 use require_c_abi_if_variadic;
135 use session::{CompileIncomplete, config, Session};
138 use util::captures::Captures;
139 use util::common::{ErrorReported, indenter};
140 use util::nodemap::{DefIdMap, DefIdSet, FxHashMap, FxHashSet, NodeMap};
142 pub use self::Expectation::*;
143 use self::autoderef::Autoderef;
144 use self::callee::DeferredCallResolution;
145 use self::coercion::{CoerceMany, DynamicCoerceMany};
146 pub use self::compare_method::{compare_impl_method, compare_const_impl};
147 use self::method::{MethodCallee, SelfSource};
148 use self::TupleArgumentsFlag::*;
150 /// The type of a local binding, including the revealed type for anon types.
151 #[derive(Copy, Clone)]
152 pub struct LocalTy<'tcx> {
154 revealed_ty: Ty<'tcx>
157 /// A wrapper for InferCtxt's `in_progress_tables` field.
158 #[derive(Copy, Clone)]
159 struct MaybeInProgressTables<'a, 'tcx: 'a> {
160 maybe_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
163 impl<'a, 'tcx> MaybeInProgressTables<'a, 'tcx> {
164 fn borrow(self) -> Ref<'a, ty::TypeckTables<'tcx>> {
165 match self.maybe_tables {
166 Some(tables) => tables.borrow(),
168 bug!("MaybeInProgressTables: inh/fcx.tables.borrow() with no tables")
173 fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
174 match self.maybe_tables {
175 Some(tables) => tables.borrow_mut(),
177 bug!("MaybeInProgressTables: inh/fcx.tables.borrow_mut() with no tables")
183 /// closures defined within the function. For example:
186 /// bar(move|| { ... })
189 /// Here, the function `foo()` and the closure passed to
190 /// `bar()` will each have their own `FnCtxt`, but they will
191 /// share the inherited fields.
192 pub struct Inherited<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
193 infcx: InferCtxt<'a, 'gcx, 'tcx>,
195 tables: MaybeInProgressTables<'a, 'tcx>,
197 locals: RefCell<NodeMap<LocalTy<'tcx>>>,
199 fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,
201 // Some additional `Sized` obligations badly affect type inference.
202 // These obligations are added in a later stage of typeck.
203 deferred_sized_obligations: RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,
205 // When we process a call like `c()` where `c` is a closure type,
206 // we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
207 // `FnOnce` closure. In that case, we defer full resolution of the
208 // call until upvar inference can kick in and make the
209 // decision. We keep these deferred resolutions grouped by the
210 // def-id of the closure, so that once we decide, we can easily go
211 // back and process them.
212 deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolution<'gcx, 'tcx>>>>,
214 deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
216 deferred_generator_interiors: RefCell<Vec<(hir::BodyId, Ty<'tcx>)>>,
218 // Opaque types found in explicit return types and their
219 // associated fresh inference variable. Writeback resolves these
220 // variables to get the concrete type, which can be used to
221 // 'de-opaque' OpaqueTypeDecl, after typeck is done with all functions.
222 opaque_types: RefCell<DefIdMap<OpaqueTypeDecl<'tcx>>>,
224 /// Each type parameter has an implicit region bound that
225 /// indicates it must outlive at least the function body (the user
226 /// may specify stronger requirements). This field indicates the
227 /// region of the callee. If it is `None`, then the parameter
228 /// environment is for an item or something where the "callee" is
230 implicit_region_bound: Option<ty::Region<'tcx>>,
232 body_id: Option<hir::BodyId>,
235 impl<'a, 'gcx, 'tcx> Deref for Inherited<'a, 'gcx, 'tcx> {
236 type Target = InferCtxt<'a, 'gcx, 'tcx>;
237 fn deref(&self) -> &Self::Target {
242 /// When type-checking an expression, we propagate downward
243 /// whatever type hint we are able in the form of an `Expectation`.
244 #[derive(Copy, Clone, Debug)]
245 pub enum Expectation<'tcx> {
246 /// We know nothing about what type this expression should have.
249 /// This expression is an `if` condition, it must resolve to `bool`.
252 /// This expression should have the type given (or some subtype)
253 ExpectHasType(Ty<'tcx>),
255 /// This expression will be cast to the `Ty`
256 ExpectCastableToType(Ty<'tcx>),
258 /// This rvalue expression will be wrapped in `&` or `Box` and coerced
259 /// to `&Ty` or `Box<Ty>`, respectively. `Ty` is `[A]` or `Trait`.
260 ExpectRvalueLikeUnsized(Ty<'tcx>),
263 impl<'a, 'gcx, 'tcx> Expectation<'tcx> {
264 // Disregard "castable to" expectations because they
265 // can lead us astray. Consider for example `if cond
266 // {22} else {c} as u8` -- if we propagate the
267 // "castable to u8" constraint to 22, it will pick the
268 // type 22u8, which is overly constrained (c might not
269 // be a u8). In effect, the problem is that the
270 // "castable to" expectation is not the tightest thing
271 // we can say, so we want to drop it in this case.
272 // The tightest thing we can say is "must unify with
273 // else branch". Note that in the case of a "has type"
274 // constraint, this limitation does not hold.
276 // If the expected type is just a type variable, then don't use
277 // an expected type. Otherwise, we might write parts of the type
278 // when checking the 'then' block which are incompatible with the
280 fn adjust_for_branches(&self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
282 ExpectHasType(ety) => {
283 let ety = fcx.shallow_resolve(ety);
284 if !ety.is_ty_var() {
290 ExpectRvalueLikeUnsized(ety) => {
291 ExpectRvalueLikeUnsized(ety)
297 /// Provide an expectation for an rvalue expression given an *optional*
298 /// hint, which is not required for type safety (the resulting type might
299 /// be checked higher up, as is the case with `&expr` and `box expr`), but
300 /// is useful in determining the concrete type.
302 /// The primary use case is where the expected type is a fat pointer,
303 /// like `&[isize]`. For example, consider the following statement:
305 /// let x: &[isize] = &[1, 2, 3];
307 /// In this case, the expected type for the `&[1, 2, 3]` expression is
308 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
309 /// expectation `ExpectHasType([isize])`, that would be too strong --
310 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
311 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
312 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
313 /// which still is useful, because it informs integer literals and the like.
314 /// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
315 /// for examples of where this comes up,.
316 fn rvalue_hint(fcx: &FnCtxt<'a, 'gcx, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
317 match fcx.tcx.struct_tail(ty).sty {
318 ty::Slice(_) | ty::Str | ty::Dynamic(..) => {
319 ExpectRvalueLikeUnsized(ty)
321 _ => ExpectHasType(ty)
325 // Resolves `expected` by a single level if it is a variable. If
326 // there is no expected type or resolution is not possible (e.g.,
327 // no constraints yet present), just returns `None`.
328 fn resolve(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Expectation<'tcx> {
330 NoExpectation => NoExpectation,
331 ExpectIfCondition => ExpectIfCondition,
332 ExpectCastableToType(t) => {
333 ExpectCastableToType(fcx.resolve_type_vars_if_possible(&t))
335 ExpectHasType(t) => {
336 ExpectHasType(fcx.resolve_type_vars_if_possible(&t))
338 ExpectRvalueLikeUnsized(t) => {
339 ExpectRvalueLikeUnsized(fcx.resolve_type_vars_if_possible(&t))
344 fn to_option(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
345 match self.resolve(fcx) {
346 NoExpectation => None,
347 ExpectIfCondition => Some(fcx.tcx.types.bool),
348 ExpectCastableToType(ty) |
350 ExpectRvalueLikeUnsized(ty) => Some(ty),
354 /// It sometimes happens that we want to turn an expectation into
355 /// a **hard constraint** (i.e., something that must be satisfied
356 /// for the program to type-check). `only_has_type` will return
357 /// such a constraint, if it exists.
358 fn only_has_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
359 match self.resolve(fcx) {
360 ExpectHasType(ty) => Some(ty),
361 ExpectIfCondition => Some(fcx.tcx.types.bool),
362 NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
366 /// Like `only_has_type`, but instead of returning `None` if no
367 /// hard constraint exists, creates a fresh type variable.
368 fn coercion_target_type(self, fcx: &FnCtxt<'a, 'gcx, 'tcx>, span: Span) -> Ty<'tcx> {
369 self.only_has_type(fcx)
370 .unwrap_or_else(|| fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span)))
374 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
381 fn maybe_mut_place(m: hir::Mutability) -> Self {
383 hir::MutMutable => Needs::MutPlace,
384 hir::MutImmutable => Needs::None,
389 #[derive(Copy, Clone)]
390 pub struct UnsafetyState {
391 pub def: ast::NodeId,
392 pub unsafety: hir::Unsafety,
393 pub unsafe_push_count: u32,
398 pub fn function(unsafety: hir::Unsafety, def: ast::NodeId) -> UnsafetyState {
399 UnsafetyState { def: def, unsafety: unsafety, unsafe_push_count: 0, from_fn: true }
402 pub fn recurse(&mut self, blk: &hir::Block) -> UnsafetyState {
403 match self.unsafety {
404 // If this unsafe, then if the outer function was already marked as
405 // unsafe we shouldn't attribute the unsafe'ness to the block. This
406 // way the block can be warned about instead of ignoring this
407 // extraneous block (functions are never warned about).
408 hir::Unsafety::Unsafe if self.from_fn => *self,
411 let (unsafety, def, count) = match blk.rules {
412 hir::PushUnsafeBlock(..) =>
413 (unsafety, blk.id, self.unsafe_push_count.checked_add(1).unwrap()),
414 hir::PopUnsafeBlock(..) =>
415 (unsafety, blk.id, self.unsafe_push_count.checked_sub(1).unwrap()),
416 hir::UnsafeBlock(..) =>
417 (hir::Unsafety::Unsafe, blk.id, self.unsafe_push_count),
419 (unsafety, self.def, self.unsafe_push_count),
423 unsafe_push_count: count,
430 #[derive(Debug, Copy, Clone)]
436 /// Tracks whether executing a node may exit normally (versus
437 /// return/break/panic, which "diverge", leaving dead code in their
438 /// wake). Tracked semi-automatically (through type variables marked
439 /// as diverging), with some manual adjustments for control-flow
440 /// primitives (approximating a CFG).
441 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
443 /// Potentially unknown, some cases converge,
444 /// others require a CFG to determine them.
447 /// Definitely known to diverge and therefore
448 /// not reach the next sibling or its parent.
451 /// Same as `Always` but with a reachability
452 /// warning already emitted
456 // Convenience impls for combinig `Diverges`.
458 impl ops::BitAnd for Diverges {
460 fn bitand(self, other: Self) -> Self {
461 cmp::min(self, other)
465 impl ops::BitOr for Diverges {
467 fn bitor(self, other: Self) -> Self {
468 cmp::max(self, other)
472 impl ops::BitAndAssign for Diverges {
473 fn bitand_assign(&mut self, other: Self) {
474 *self = *self & other;
478 impl ops::BitOrAssign for Diverges {
479 fn bitor_assign(&mut self, other: Self) {
480 *self = *self | other;
485 fn always(self) -> bool {
486 self >= Diverges::Always
490 pub struct BreakableCtxt<'gcx: 'tcx, 'tcx> {
493 // this is `null` for loops where break with a value is illegal,
494 // such as `while`, `for`, and `while let`
495 coerce: Option<DynamicCoerceMany<'gcx, 'tcx>>,
498 pub struct EnclosingBreakables<'gcx: 'tcx, 'tcx> {
499 stack: Vec<BreakableCtxt<'gcx, 'tcx>>,
500 by_id: NodeMap<usize>,
503 impl<'gcx, 'tcx> EnclosingBreakables<'gcx, 'tcx> {
504 fn find_breakable(&mut self, target_id: ast::NodeId) -> &mut BreakableCtxt<'gcx, 'tcx> {
505 let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
506 bug!("could not find enclosing breakable with id {}", target_id);
512 pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
513 body_id: ast::NodeId,
515 /// The parameter environment used for proving trait obligations
516 /// in this function. This can change when we descend into
517 /// closures (as they bring new things into scope), hence it is
518 /// not part of `Inherited` (as of the time of this writing,
519 /// closures do not yet change the environment, but they will
521 param_env: ty::ParamEnv<'tcx>,
523 // Number of errors that had been reported when we started
524 // checking this function. On exit, if we find that *more* errors
525 // have been reported, we will skip regionck and other work that
526 // expects the types within the function to be consistent.
527 err_count_on_creation: usize,
529 ret_coercion: Option<RefCell<DynamicCoerceMany<'gcx, 'tcx>>>,
530 ret_coercion_span: RefCell<Option<Span>>,
532 yield_ty: Option<Ty<'tcx>>,
534 ps: RefCell<UnsafetyState>,
536 /// Whether the last checked node generates a divergence (e.g.,
537 /// `return` will set this to Always). In general, when entering
538 /// an expression or other node in the tree, the initial value
539 /// indicates whether prior parts of the containing expression may
540 /// have diverged. It is then typically set to `Maybe` (and the
541 /// old value remembered) for processing the subparts of the
542 /// current expression. As each subpart is processed, they may set
543 /// the flag to `Always` etc. Finally, at the end, we take the
544 /// result and "union" it with the original value, so that when we
545 /// return the flag indicates if any subpart of the parent
546 /// expression (up to and including this part) has diverged. So,
547 /// if you read it after evaluating a subexpression `X`, the value
548 /// you get indicates whether any subexpression that was
549 /// evaluating up to and including `X` diverged.
551 /// We currently use this flag only for diagnostic purposes:
553 /// - To warn about unreachable code: if, after processing a
554 /// sub-expression but before we have applied the effects of the
555 /// current node, we see that the flag is set to `Always`, we
556 /// can issue a warning. This corresponds to something like
557 /// `foo(return)`; we warn on the `foo()` expression. (We then
558 /// update the flag to `WarnedAlways` to suppress duplicate
559 /// reports.) Similarly, if we traverse to a fresh statement (or
560 /// tail expression) from a `Always` setting, we will issue a
561 /// warning. This corresponds to something like `{return;
562 /// foo();}` or `{return; 22}`, where we would warn on the
565 /// An expression represents dead-code if, after checking it,
566 /// the diverges flag is set to something other than `Maybe`.
567 diverges: Cell<Diverges>,
569 /// Whether any child nodes have any type errors.
570 has_errors: Cell<bool>,
572 enclosing_breakables: RefCell<EnclosingBreakables<'gcx, 'tcx>>,
574 inh: &'a Inherited<'a, 'gcx, 'tcx>,
577 impl<'a, 'gcx, 'tcx> Deref for FnCtxt<'a, 'gcx, 'tcx> {
578 type Target = Inherited<'a, 'gcx, 'tcx>;
579 fn deref(&self) -> &Self::Target {
584 /// Helper type of a temporary returned by Inherited::build(...).
585 /// Necessary because we can't write the following bound:
586 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(Inherited<'b, 'gcx, 'tcx>).
587 pub struct InheritedBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
588 infcx: infer::InferCtxtBuilder<'a, 'gcx, 'tcx>,
592 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
593 pub fn build(tcx: TyCtxt<'a, 'gcx, 'gcx>, def_id: DefId)
594 -> InheritedBuilder<'a, 'gcx, 'tcx> {
595 let hir_id_root = if def_id.is_local() {
596 let node_id = tcx.hir().as_local_node_id(def_id).unwrap();
597 let hir_id = tcx.hir().definitions().node_to_hir_id(node_id);
598 DefId::local(hir_id.owner)
604 infcx: tcx.infer_ctxt().with_fresh_in_progress_tables(hir_id_root),
610 impl<'a, 'gcx, 'tcx> InheritedBuilder<'a, 'gcx, 'tcx> {
611 fn enter<F, R>(&'tcx mut self, f: F) -> R
612 where F: for<'b> FnOnce(Inherited<'b, 'gcx, 'tcx>) -> R
614 let def_id = self.def_id;
615 self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
619 impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
620 fn new(infcx: InferCtxt<'a, 'gcx, 'tcx>, def_id: DefId) -> Self {
622 let item_id = tcx.hir().as_local_node_id(def_id);
623 let body_id = item_id.and_then(|id| tcx.hir().maybe_body_owned_by(id));
624 let implicit_region_bound = body_id.map(|body_id| {
625 let body = tcx.hir().body(body_id);
626 tcx.mk_region(ty::ReScope(region::Scope {
627 id: body.value.hir_id.local_id,
628 data: region::ScopeData::CallSite
633 tables: MaybeInProgressTables {
634 maybe_tables: infcx.in_progress_tables,
637 fulfillment_cx: RefCell::new(TraitEngine::new(tcx)),
638 locals: RefCell::new(Default::default()),
639 deferred_sized_obligations: RefCell::new(Vec::new()),
640 deferred_call_resolutions: RefCell::new(Default::default()),
641 deferred_cast_checks: RefCell::new(Vec::new()),
642 deferred_generator_interiors: RefCell::new(Vec::new()),
643 opaque_types: RefCell::new(Default::default()),
644 implicit_region_bound,
649 fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
650 debug!("register_predicate({:?})", obligation);
651 if obligation.has_escaping_bound_vars() {
652 span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}",
657 .register_predicate_obligation(self, obligation);
660 fn register_predicates<I>(&self, obligations: I)
661 where I: IntoIterator<Item = traits::PredicateObligation<'tcx>>
663 for obligation in obligations {
664 self.register_predicate(obligation);
668 fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
669 self.register_predicates(infer_ok.obligations);
673 fn normalize_associated_types_in<T>(&self,
675 body_id: ast::NodeId,
676 param_env: ty::ParamEnv<'tcx>,
678 where T : TypeFoldable<'tcx>
680 let ok = self.partially_normalize_associated_types_in(span, body_id, param_env, value);
681 self.register_infer_ok_obligations(ok)
685 struct CheckItemTypesVisitor<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx> }
687 impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CheckItemTypesVisitor<'a, 'tcx> {
688 fn visit_item(&mut self, i: &'tcx hir::Item) {
689 check_item_type(self.tcx, i);
691 fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
692 fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
695 pub fn check_wf_new<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Result<(), ErrorReported> {
696 tcx.sess.track_errors(|| {
697 let mut visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
698 tcx.hir().krate().visit_all_item_likes(&mut visit.as_deep_visitor());
702 pub fn check_item_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Result<(), ErrorReported> {
703 tcx.sess.track_errors(|| {
704 for &module in tcx.hir().krate().modules.keys() {
705 queries::check_mod_item_types::ensure(tcx, tcx.hir().local_def_id(module));
710 fn check_mod_item_types<'tcx>(tcx: TyCtxt<'_, 'tcx, 'tcx>, module_def_id: DefId) {
711 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
714 pub fn check_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Result<(), CompileIncomplete> {
715 tcx.typeck_item_bodies(LOCAL_CRATE)
718 fn typeck_item_bodies<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum)
719 -> Result<(), CompileIncomplete>
721 debug_assert!(crate_num == LOCAL_CRATE);
722 Ok(tcx.sess.track_errors(|| {
723 tcx.par_body_owners(|body_owner_def_id| {
724 ty::query::queries::typeck_tables_of::ensure(tcx, body_owner_def_id);
729 fn check_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
730 wfcheck::check_item_well_formed(tcx, def_id);
733 fn check_trait_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
734 wfcheck::check_trait_item(tcx, def_id);
737 fn check_impl_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
738 wfcheck::check_impl_item(tcx, def_id);
741 pub fn provide(providers: &mut Providers) {
742 method::provide(providers);
743 *providers = Providers {
749 check_item_well_formed,
750 check_trait_item_well_formed,
751 check_impl_item_well_formed,
752 check_mod_item_types,
757 fn adt_destructor<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
759 -> Option<ty::Destructor> {
760 tcx.calculate_dtor(def_id, &mut dropck::check_drop_impl)
763 /// If this def-id is a "primary tables entry", returns `Some((body_id, decl))`
764 /// with information about it's body-id and fn-decl (if any). Otherwise,
767 /// If this function returns "some", then `typeck_tables(def_id)` will
768 /// succeed; if it returns `None`, then `typeck_tables(def_id)` may or
769 /// may not succeed. In some cases where this function returns `None`
770 /// (notably closures), `typeck_tables(def_id)` would wind up
771 /// redirecting to the owning function.
772 fn primary_body_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
774 -> Option<(hir::BodyId, Option<&'tcx hir::FnDecl>)>
776 match tcx.hir().get(id) {
777 Node::Item(item) => {
779 hir::ItemKind::Const(_, body) |
780 hir::ItemKind::Static(_, _, body) =>
782 hir::ItemKind::Fn(ref decl, .., body) =>
783 Some((body, Some(decl))),
788 Node::TraitItem(item) => {
790 hir::TraitItemKind::Const(_, Some(body)) =>
792 hir::TraitItemKind::Method(ref sig, hir::TraitMethod::Provided(body)) =>
793 Some((body, Some(&sig.decl))),
798 Node::ImplItem(item) => {
800 hir::ImplItemKind::Const(_, body) =>
802 hir::ImplItemKind::Method(ref sig, body) =>
803 Some((body, Some(&sig.decl))),
808 Node::AnonConst(constant) => Some((constant.body, None)),
813 fn has_typeck_tables<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
816 // Closures' tables come from their outermost function,
817 // as they are part of the same "inference environment".
818 let outer_def_id = tcx.closure_base_def_id(def_id);
819 if outer_def_id != def_id {
820 return tcx.has_typeck_tables(outer_def_id);
823 let id = tcx.hir().as_local_node_id(def_id).unwrap();
824 primary_body_of(tcx, id).is_some()
827 fn used_trait_imports<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
830 tcx.typeck_tables_of(def_id).used_trait_imports.clone()
833 fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
835 -> &'tcx ty::TypeckTables<'tcx> {
836 // Closures' tables come from their outermost function,
837 // as they are part of the same "inference environment".
838 let outer_def_id = tcx.closure_base_def_id(def_id);
839 if outer_def_id != def_id {
840 return tcx.typeck_tables_of(outer_def_id);
843 let id = tcx.hir().as_local_node_id(def_id).unwrap();
844 let span = tcx.hir().span(id);
846 // Figure out what primary body this item has.
847 let (body_id, fn_decl) = primary_body_of(tcx, id).unwrap_or_else(|| {
848 span_bug!(span, "can't type-check body of {:?}", def_id);
850 let body = tcx.hir().body(body_id);
852 let tables = Inherited::build(tcx, def_id).enter(|inh| {
853 let param_env = tcx.param_env(def_id);
854 let fcx = if let Some(decl) = fn_decl {
855 let fn_sig = tcx.fn_sig(def_id);
857 check_abi(tcx, span, fn_sig.abi());
859 // Compute the fty from point of view of inside the fn.
861 tcx.liberate_late_bound_regions(def_id, &fn_sig);
863 inh.normalize_associated_types_in(body.value.span,
868 let fcx = check_fn(&inh, param_env, fn_sig, decl, id, body, None).0;
871 let fcx = FnCtxt::new(&inh, param_env, body.value.id);
872 let expected_type = tcx.type_of(def_id);
873 let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
874 fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
876 let revealed_ty = if tcx.features().impl_trait_in_bindings {
877 fcx.instantiate_opaque_types_from_value(
885 // Gather locals in statics (because of block expressions).
886 GatherLocalsVisitor { fcx: &fcx, parent_id: id, }.visit_body(body);
888 fcx.check_expr_coercable_to_type(&body.value, revealed_ty);
893 // All type checking constraints were added, try to fallback unsolved variables.
894 fcx.select_obligations_where_possible(false);
895 let mut fallback_has_occurred = false;
896 for ty in &fcx.unsolved_variables() {
897 fallback_has_occurred |= fcx.fallback_if_possible(ty);
899 fcx.select_obligations_where_possible(fallback_has_occurred);
901 // Even though coercion casts provide type hints, we check casts after fallback for
902 // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
905 // Closure and generator analysis may run after fallback
906 // because they don't constrain other type variables.
907 fcx.closure_analyze(body);
908 assert!(fcx.deferred_call_resolutions.borrow().is_empty());
909 fcx.resolve_generator_interiors(def_id);
911 for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
912 let ty = fcx.normalize_ty(span, ty);
913 fcx.require_type_is_sized(ty, span, code);
915 fcx.select_all_obligations_or_error();
917 if fn_decl.is_some() {
918 fcx.regionck_fn(id, body);
920 fcx.regionck_expr(body);
923 fcx.resolve_type_vars_in_body(body)
926 // Consistency check our TypeckTables instance can hold all ItemLocalIds
927 // it will need to hold.
928 assert_eq!(tables.local_id_root,
929 Some(DefId::local(tcx.hir().definitions().node_to_hir_id(id).owner)));
933 fn check_abi<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, abi: Abi) {
934 if !tcx.sess.target.target.is_abi_supported(abi) {
935 struct_span_err!(tcx.sess, span, E0570,
936 "The ABI `{}` is not supported for the current target", abi).emit()
940 struct GatherLocalsVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
941 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
942 parent_id: ast::NodeId,
945 impl<'a, 'gcx, 'tcx> GatherLocalsVisitor<'a, 'gcx, 'tcx> {
946 fn assign(&mut self, span: Span, nid: ast::NodeId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
949 // infer the variable's type
950 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
951 self.fcx.locals.borrow_mut().insert(nid, LocalTy {
958 // take type that the user specified
959 self.fcx.locals.borrow_mut().insert(nid, typ);
966 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for GatherLocalsVisitor<'a, 'gcx, 'tcx> {
967 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
968 NestedVisitorMap::None
971 // Add explicitly-declared locals.
972 fn visit_local(&mut self, local: &'gcx hir::Local) {
973 let local_ty = match local.ty {
975 let o_ty = self.fcx.to_ty(&ty);
977 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
978 self.fcx.instantiate_opaque_types_from_value(
986 let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(
987 &UserTypeAnnotation::Ty(revealed_ty)
989 debug!("visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
990 ty.hir_id, o_ty, revealed_ty, c_ty);
991 self.fcx.tables.borrow_mut().user_provided_types_mut().insert(ty.hir_id, c_ty);
993 Some(LocalTy { decl_ty: o_ty, revealed_ty })
997 self.assign(local.span, local.id, local_ty);
999 debug!("Local variable {:?} is assigned type {}",
1001 self.fcx.ty_to_string(
1002 self.fcx.locals.borrow().get(&local.id).unwrap().clone().decl_ty));
1003 intravisit::walk_local(self, local);
1006 // Add pattern bindings.
1007 fn visit_pat(&mut self, p: &'gcx hir::Pat) {
1008 if let PatKind::Binding(_, _, ident, _) = p.node {
1009 let var_ty = self.assign(p.span, p.id, None);
1011 if !self.fcx.tcx.features().unsized_locals {
1012 self.fcx.require_type_is_sized(var_ty, p.span,
1013 traits::VariableType(p.id));
1016 debug!("Pattern binding {} is assigned to {} with type {:?}",
1018 self.fcx.ty_to_string(
1019 self.fcx.locals.borrow().get(&p.id).unwrap().clone().decl_ty),
1022 intravisit::walk_pat(self, p);
1025 // Don't descend into the bodies of nested closures
1026 fn visit_fn(&mut self, _: intravisit::FnKind<'gcx>, _: &'gcx hir::FnDecl,
1027 _: hir::BodyId, _: Span, _: ast::NodeId) { }
1030 /// When `check_fn` is invoked on a generator (i.e., a body that
1031 /// includes yield), it returns back some information about the yield
1033 struct GeneratorTypes<'tcx> {
1034 /// Type of value that is yielded.
1035 yield_ty: ty::Ty<'tcx>,
1037 /// Types that are captured (see `GeneratorInterior` for more).
1038 interior: ty::Ty<'tcx>,
1040 /// Indicates if the generator is movable or static (immovable)
1041 movability: hir::GeneratorMovability,
1044 /// Helper used for fns and closures. Does the grungy work of checking a function
1045 /// body and returns the function context used for that purpose, since in the case of a fn item
1046 /// there is still a bit more to do.
1049 /// * inherited: other fields inherited from the enclosing fn (if any)
1050 fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
1051 param_env: ty::ParamEnv<'tcx>,
1052 fn_sig: ty::FnSig<'tcx>,
1053 decl: &'gcx hir::FnDecl,
1055 body: &'gcx hir::Body,
1056 can_be_generator: Option<hir::GeneratorMovability>)
1057 -> (FnCtxt<'a, 'gcx, 'tcx>, Option<GeneratorTypes<'tcx>>)
1059 let mut fn_sig = fn_sig.clone();
1061 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
1063 // Create the function context. This is either derived from scratch or,
1064 // in the case of closures, based on the outer context.
1065 let mut fcx = FnCtxt::new(inherited, param_env, body.value.id);
1066 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
1068 let declared_ret_ty = fn_sig.output();
1069 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
1070 let revealed_ret_ty = fcx.instantiate_opaque_types_from_value(fn_id, &declared_ret_ty);
1071 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
1072 fn_sig = fcx.tcx.mk_fn_sig(
1073 fn_sig.inputs().iter().cloned(),
1080 let span = body.value.span;
1082 if body.is_generator && can_be_generator.is_some() {
1083 let yield_ty = fcx.next_ty_var(TypeVariableOrigin::TypeInference(span));
1084 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
1085 fcx.yield_ty = Some(yield_ty);
1088 let outer_def_id = fcx.tcx.closure_base_def_id(fcx.tcx.hir().local_def_id(fn_id));
1089 let outer_node_id = fcx.tcx.hir().as_local_node_id(outer_def_id).unwrap();
1090 GatherLocalsVisitor { fcx: &fcx, parent_id: outer_node_id, }.visit_body(body);
1092 // Add formal parameters.
1093 for (arg_ty, arg) in fn_sig.inputs().iter().zip(&body.arguments) {
1094 // Check the pattern.
1098 ty::BindingMode::BindByValue(hir::Mutability::MutImmutable),
1102 // Check that argument is Sized.
1103 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
1104 // for simple cases like `fn foo(x: Trait)`,
1105 // where we would error once on the parameter as a whole, and once on the binding `x`.
1106 if arg.pat.simple_ident().is_none() && !fcx.tcx.features().unsized_locals {
1107 fcx.require_type_is_sized(arg_ty, decl.output.span(), traits::SizedArgumentType);
1110 fcx.write_ty(arg.hir_id, arg_ty);
1113 let fn_hir_id = fcx.tcx.hir().node_to_hir_id(fn_id);
1114 inherited.tables.borrow_mut().liberated_fn_sigs_mut().insert(fn_hir_id, fn_sig);
1116 fcx.check_return_expr(&body.value);
1118 // We insert the deferred_generator_interiors entry after visiting the body.
1119 // This ensures that all nested generators appear before the entry of this generator.
1120 // resolve_generator_interiors relies on this property.
1121 let gen_ty = if can_be_generator.is_some() && body.is_generator {
1122 let interior = fcx.next_ty_var(TypeVariableOrigin::MiscVariable(span));
1123 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior));
1124 Some(GeneratorTypes {
1125 yield_ty: fcx.yield_ty.unwrap(),
1127 movability: can_be_generator.unwrap(),
1133 // Finalize the return check by taking the LUB of the return types
1134 // we saw and assigning it to the expected return type. This isn't
1135 // really expected to fail, since the coercions would have failed
1136 // earlier when trying to find a LUB.
1138 // However, the behavior around `!` is sort of complex. In the
1139 // event that the `actual_return_ty` comes back as `!`, that
1140 // indicates that the fn either does not return or "returns" only
1141 // values of type `!`. In this case, if there is an expected
1142 // return type that is *not* `!`, that should be ok. But if the
1143 // return type is being inferred, we want to "fallback" to `!`:
1145 // let x = move || panic!();
1147 // To allow for that, I am creating a type variable with diverging
1148 // fallback. This was deemed ever so slightly better than unifying
1149 // the return value with `!` because it allows for the caller to
1150 // make more assumptions about the return type (e.g., they could do
1152 // let y: Option<u32> = Some(x());
1154 // which would then cause this return type to become `u32`, not
1156 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
1157 let mut actual_return_ty = coercion.complete(&fcx);
1158 if actual_return_ty.is_never() {
1159 actual_return_ty = fcx.next_diverging_ty_var(
1160 TypeVariableOrigin::DivergingFn(span));
1162 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
1164 // Check that the main return type implements the termination trait.
1165 if let Some(term_id) = fcx.tcx.lang_items().termination() {
1166 if let Some((id, _, entry_type)) = *fcx.tcx.sess.entry_fn.borrow() {
1168 if let config::EntryFnType::Main = entry_type {
1169 let substs = fcx.tcx.mk_substs_trait(declared_ret_ty, &[]);
1170 let trait_ref = ty::TraitRef::new(term_id, substs);
1171 let return_ty_span = decl.output.span();
1172 let cause = traits::ObligationCause::new(
1173 return_ty_span, fn_id, ObligationCauseCode::MainFunctionType);
1175 inherited.register_predicate(
1176 traits::Obligation::new(
1177 cause, param_env, trait_ref.to_predicate()));
1183 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
1184 if let Some(panic_impl_did) = fcx.tcx.lang_items().panic_impl() {
1185 if panic_impl_did == fcx.tcx.hir().local_def_id(fn_id) {
1186 if let Some(panic_info_did) = fcx.tcx.lang_items().panic_info() {
1187 // at this point we don't care if there are duplicate handlers or if the handler has
1188 // the wrong signature as this value we'll be used when writing metadata and that
1189 // only happens if compilation succeeded
1190 fcx.tcx.sess.has_panic_handler.try_set_same(true);
1192 if declared_ret_ty.sty != ty::Never {
1193 fcx.tcx.sess.span_err(
1195 "return type should be `!`",
1199 let inputs = fn_sig.inputs();
1200 let span = fcx.tcx.hir().span(fn_id);
1201 if inputs.len() == 1 {
1202 let arg_is_panic_info = match inputs[0].sty {
1203 ty::Ref(region, ty, mutbl) => match ty.sty {
1204 ty::Adt(ref adt, _) => {
1205 adt.did == panic_info_did &&
1206 mutbl == hir::Mutability::MutImmutable &&
1207 *region != RegionKind::ReStatic
1214 if !arg_is_panic_info {
1215 fcx.tcx.sess.span_err(
1216 decl.inputs[0].span,
1217 "argument should be `&PanicInfo`",
1221 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1222 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1223 if !generics.params.is_empty() {
1224 fcx.tcx.sess.span_err(
1226 "should have no type parameters",
1232 let span = fcx.tcx.sess.source_map().def_span(span);
1233 fcx.tcx.sess.span_err(span, "function should have one argument");
1236 fcx.tcx.sess.err("language item required, but not found: `panic_info`");
1241 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
1242 if let Some(alloc_error_handler_did) = fcx.tcx.lang_items().oom() {
1243 if alloc_error_handler_did == fcx.tcx.hir().local_def_id(fn_id) {
1244 if let Some(alloc_layout_did) = fcx.tcx.lang_items().alloc_layout() {
1245 if declared_ret_ty.sty != ty::Never {
1246 fcx.tcx.sess.span_err(
1248 "return type should be `!`",
1252 let inputs = fn_sig.inputs();
1253 let span = fcx.tcx.hir().span(fn_id);
1254 if inputs.len() == 1 {
1255 let arg_is_alloc_layout = match inputs[0].sty {
1256 ty::Adt(ref adt, _) => {
1257 adt.did == alloc_layout_did
1262 if !arg_is_alloc_layout {
1263 fcx.tcx.sess.span_err(
1264 decl.inputs[0].span,
1265 "argument should be `Layout`",
1269 if let Node::Item(item) = fcx.tcx.hir().get(fn_id) {
1270 if let ItemKind::Fn(_, _, ref generics, _) = item.node {
1271 if !generics.params.is_empty() {
1272 fcx.tcx.sess.span_err(
1274 "`#[alloc_error_handler]` function should have no type \
1281 let span = fcx.tcx.sess.source_map().def_span(span);
1282 fcx.tcx.sess.span_err(span, "function should have one argument");
1285 fcx.tcx.sess.err("language item required, but not found: `alloc_layout`");
1293 fn check_struct<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1296 let def_id = tcx.hir().local_def_id(id);
1297 let def = tcx.adt_def(def_id);
1298 def.destructor(tcx); // force the destructor to be evaluated
1299 check_representable(tcx, span, def_id);
1301 if def.repr.simd() {
1302 check_simd(tcx, span, def_id);
1305 check_transparent(tcx, span, def_id);
1306 check_packed(tcx, span, def_id);
1309 fn check_union<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1312 let def_id = tcx.hir().local_def_id(id);
1313 let def = tcx.adt_def(def_id);
1314 def.destructor(tcx); // force the destructor to be evaluated
1315 check_representable(tcx, span, def_id);
1317 check_packed(tcx, span, def_id);
1320 fn check_opaque<'a, 'tcx>(
1321 tcx: TyCtxt<'a, 'tcx, 'tcx>,
1323 substs: &'tcx Substs<'tcx>,
1326 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
1327 let mut err = struct_span_err!(
1328 tcx.sess, span, E0720,
1329 "opaque type expands to a recursive type",
1331 err.span_label(span, "expands to self-referential type");
1332 if let ty::Opaque(..) = partially_expanded_type.sty {
1333 err.note("type resolves to itself");
1335 err.note(&format!("expanded type is `{}`", partially_expanded_type));
1341 pub fn check_item_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, it: &'tcx hir::Item) {
1343 "check_item_type(it.id={}, it.name={})",
1345 tcx.item_path_str(tcx.hir().local_def_id(it.id))
1347 let _indenter = indenter();
1349 // Consts can play a role in type-checking, so they are included here.
1350 hir::ItemKind::Static(..) => {
1351 let def_id = tcx.hir().local_def_id(it.id);
1352 tcx.typeck_tables_of(def_id);
1353 maybe_check_static_with_link_section(tcx, def_id, it.span);
1355 hir::ItemKind::Const(..) => {
1356 tcx.typeck_tables_of(tcx.hir().local_def_id(it.id));
1358 hir::ItemKind::Enum(ref enum_definition, _) => {
1359 check_enum(tcx, it.span, &enum_definition.variants, it.id);
1361 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
1362 hir::ItemKind::Impl(.., ref impl_item_refs) => {
1363 debug!("ItemKind::Impl {} with id {}", it.ident, it.id);
1364 let impl_def_id = tcx.hir().local_def_id(it.id);
1365 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1366 check_impl_items_against_trait(
1373 let trait_def_id = impl_trait_ref.def_id;
1374 check_on_unimplemented(tcx, trait_def_id, it);
1377 hir::ItemKind::Trait(..) => {
1378 let def_id = tcx.hir().local_def_id(it.id);
1379 check_on_unimplemented(tcx, def_id, it);
1381 hir::ItemKind::Struct(..) => {
1382 check_struct(tcx, it.id, it.span);
1384 hir::ItemKind::Union(..) => {
1385 check_union(tcx, it.id, it.span);
1387 hir::ItemKind::Existential(..) => {
1388 let def_id = tcx.hir().local_def_id(it.id);
1389 let pty_ty = tcx.type_of(def_id);
1390 let generics = tcx.generics_of(def_id);
1392 check_bounds_are_used(tcx, &generics, pty_ty);
1393 let substs = Substs::identity_for_item(tcx, def_id);
1394 check_opaque(tcx, def_id, substs, it.span);
1396 hir::ItemKind::Ty(..) => {
1397 let def_id = tcx.hir().local_def_id(it.id);
1398 let pty_ty = tcx.type_of(def_id);
1399 let generics = tcx.generics_of(def_id);
1400 check_bounds_are_used(tcx, &generics, pty_ty);
1402 hir::ItemKind::ForeignMod(ref m) => {
1403 check_abi(tcx, it.span, m.abi);
1405 if m.abi == Abi::RustIntrinsic {
1406 for item in &m.items {
1407 intrinsic::check_intrinsic_type(tcx, item);
1409 } else if m.abi == Abi::PlatformIntrinsic {
1410 for item in &m.items {
1411 intrinsic::check_platform_intrinsic_type(tcx, item);
1414 for item in &m.items {
1415 let generics = tcx.generics_of(tcx.hir().local_def_id(item.id));
1416 if generics.params.len() - generics.own_counts().lifetimes != 0 {
1417 let mut err = struct_span_err!(
1421 "foreign items may not have type parameters"
1423 err.span_label(item.span, "can't have type parameters");
1424 // FIXME: once we start storing spans for type arguments, turn this into a
1427 "use specialization instead of type parameters by replacing them \
1428 with concrete types like `u32`",
1433 if let hir::ForeignItemKind::Fn(ref fn_decl, _, _) = item.node {
1434 require_c_abi_if_variadic(tcx, fn_decl, m.abi, item.span);
1439 _ => { /* nothing to do */ }
1443 fn maybe_check_static_with_link_section(tcx: TyCtxt, id: DefId, span: Span) {
1444 // Only restricted on wasm32 target for now
1445 if !tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
1449 // If `#[link_section]` is missing, then nothing to verify
1450 let attrs = tcx.codegen_fn_attrs(id);
1451 if attrs.link_section.is_none() {
1455 // For the wasm32 target statics with #[link_section] are placed into custom
1456 // sections of the final output file, but this isn't link custom sections of
1457 // other executable formats. Namely we can only embed a list of bytes,
1458 // nothing with pointers to anything else or relocations. If any relocation
1459 // show up, reject them here.
1460 let instance = ty::Instance::mono(tcx, id);
1461 let cid = GlobalId {
1465 let param_env = ty::ParamEnv::reveal_all();
1466 if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
1467 let alloc = if let ConstValue::ByRef(_, allocation, _) = static_.val {
1470 bug!("Matching on non-ByRef static")
1472 if alloc.relocations.len() != 0 {
1473 let msg = "statics with a custom `#[link_section]` must be a \
1474 simple list of bytes on the wasm target with no \
1475 extra levels of indirection such as references";
1476 tcx.sess.span_err(span, msg);
1481 fn check_on_unimplemented<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1482 trait_def_id: DefId,
1484 let item_def_id = tcx.hir().local_def_id(item.id);
1485 // an error would be reported if this fails.
1486 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id);
1489 fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1490 impl_item: &hir::ImplItem,
1493 let mut err = struct_span_err!(
1494 tcx.sess, impl_item.span, E0520,
1495 "`{}` specializes an item from a parent `impl`, but \
1496 that item is not marked `default`",
1498 err.span_label(impl_item.span, format!("cannot specialize default item `{}`",
1501 match tcx.span_of_impl(parent_impl) {
1503 err.span_label(span, "parent `impl` is here");
1504 err.note(&format!("to specialize, `{}` in the parent `impl` must be marked `default`",
1508 err.note(&format!("parent implementation is in crate `{}`", cname));
1515 fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1516 trait_def: &ty::TraitDef,
1517 trait_item: &ty::AssociatedItem,
1519 impl_item: &hir::ImplItem)
1521 let ancestors = trait_def.ancestors(tcx, impl_id);
1523 let kind = match impl_item.node {
1524 hir::ImplItemKind::Const(..) => ty::AssociatedKind::Const,
1525 hir::ImplItemKind::Method(..) => ty::AssociatedKind::Method,
1526 hir::ImplItemKind::Existential(..) => ty::AssociatedKind::Existential,
1527 hir::ImplItemKind::Type(_) => ty::AssociatedKind::Type
1530 let parent = ancestors.defs(tcx, trait_item.ident, kind, trait_def.def_id).nth(1)
1531 .map(|node_item| node_item.map(|parent| parent.defaultness));
1533 if let Some(parent) = parent {
1534 if tcx.impl_item_is_final(&parent) {
1535 report_forbidden_specialization(tcx, impl_item, parent.node.def_id());
1541 fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1544 impl_trait_ref: ty::TraitRef<'tcx>,
1545 impl_item_refs: &[hir::ImplItemRef]) {
1546 let impl_span = tcx.sess.source_map().def_span(impl_span);
1548 // If the trait reference itself is erroneous (so the compilation is going
1549 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1550 // isn't populated for such impls.
1551 if impl_trait_ref.references_error() { return; }
1553 // Locate trait definition and items
1554 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1555 let mut overridden_associated_type = None;
1557 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
1559 // Check existing impl methods to see if they are both present in trait
1560 // and compatible with trait signature
1561 for impl_item in impl_items() {
1562 let ty_impl_item = tcx.associated_item(tcx.hir().local_def_id(impl_item.id));
1563 let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
1564 .find(|ac| Namespace::from(&impl_item.node) == Namespace::from(ac.kind) &&
1565 tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1567 // Not compatible, but needed for the error message
1568 tcx.associated_items(impl_trait_ref.def_id)
1569 .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
1572 // Check that impl definition matches trait definition
1573 if let Some(ty_trait_item) = ty_trait_item {
1574 match impl_item.node {
1575 hir::ImplItemKind::Const(..) => {
1576 // Find associated const definition.
1577 if ty_trait_item.kind == ty::AssociatedKind::Const {
1578 compare_const_impl(tcx,
1584 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0323,
1585 "item `{}` is an associated const, \
1586 which doesn't match its trait `{}`",
1589 err.span_label(impl_item.span, "does not match trait");
1590 // We can only get the spans from local trait definition
1591 // Same for E0324 and E0325
1592 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1593 err.span_label(trait_span, "item in trait");
1598 hir::ImplItemKind::Method(..) => {
1599 let trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1600 if ty_trait_item.kind == ty::AssociatedKind::Method {
1601 compare_impl_method(tcx,
1608 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0324,
1609 "item `{}` is an associated method, \
1610 which doesn't match its trait `{}`",
1613 err.span_label(impl_item.span, "does not match trait");
1614 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1615 err.span_label(trait_span, "item in trait");
1620 hir::ImplItemKind::Existential(..) |
1621 hir::ImplItemKind::Type(_) => {
1622 if ty_trait_item.kind == ty::AssociatedKind::Type {
1623 if ty_trait_item.defaultness.has_value() {
1624 overridden_associated_type = Some(impl_item);
1627 let mut err = struct_span_err!(tcx.sess, impl_item.span, E0325,
1628 "item `{}` is an associated type, \
1629 which doesn't match its trait `{}`",
1632 err.span_label(impl_item.span, "does not match trait");
1633 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
1634 err.span_label(trait_span, "item in trait");
1641 check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
1645 // Check for missing items from trait
1646 let mut missing_items = Vec::new();
1647 let mut invalidated_items = Vec::new();
1648 let associated_type_overridden = overridden_associated_type.is_some();
1649 for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
1650 let is_implemented = trait_def.ancestors(tcx, impl_id)
1651 .defs(tcx, trait_item.ident, trait_item.kind, impl_trait_ref.def_id)
1653 .map(|node_item| !node_item.node.is_from_trait())
1656 if !is_implemented && !tcx.impl_is_default(impl_id) {
1657 if !trait_item.defaultness.has_value() {
1658 missing_items.push(trait_item);
1659 } else if associated_type_overridden {
1660 invalidated_items.push(trait_item.ident);
1665 if !missing_items.is_empty() {
1666 let mut err = struct_span_err!(tcx.sess, impl_span, E0046,
1667 "not all trait items implemented, missing: `{}`",
1668 missing_items.iter()
1669 .map(|trait_item| trait_item.ident.to_string())
1670 .collect::<Vec<_>>().join("`, `"));
1671 err.span_label(impl_span, format!("missing `{}` in implementation",
1672 missing_items.iter()
1673 .map(|trait_item| trait_item.ident.to_string())
1674 .collect::<Vec<_>>().join("`, `")));
1675 for trait_item in missing_items {
1676 if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
1677 err.span_label(span, format!("`{}` from trait", trait_item.ident));
1679 err.note_trait_signature(trait_item.ident.to_string(),
1680 trait_item.signature(&tcx));
1686 if !invalidated_items.is_empty() {
1687 let invalidator = overridden_associated_type.unwrap();
1688 span_err!(tcx.sess, invalidator.span, E0399,
1689 "the following trait items need to be reimplemented \
1690 as `{}` was overridden: `{}`",
1692 invalidated_items.iter()
1693 .map(|name| name.to_string())
1694 .collect::<Vec<_>>().join("`, `"))
1698 /// Checks whether a type can be represented in memory. In particular, it
1699 /// identifies types that contain themselves without indirection through a
1700 /// pointer, which would mean their size is unbounded.
1701 fn check_representable<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1705 let rty = tcx.type_of(item_def_id);
1707 // Check that it is possible to represent this type. This call identifies
1708 // (1) types that contain themselves and (2) types that contain a different
1709 // recursive type. It is only necessary to throw an error on those that
1710 // contain themselves. For case 2, there must be an inner type that will be
1711 // caught by case 1.
1712 match rty.is_representable(tcx, sp) {
1713 Representability::SelfRecursive(spans) => {
1714 let mut err = tcx.recursive_type_with_infinite_size_error(item_def_id);
1716 err.span_label(span, "recursive without indirection");
1721 Representability::Representable | Representability::ContainsRecursive => (),
1726 pub fn check_simd<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1727 let t = tcx.type_of(def_id);
1728 if let ty::Adt(def, substs) = t.sty {
1729 if def.is_struct() {
1730 let fields = &def.non_enum_variant().fields;
1731 if fields.is_empty() {
1732 span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty");
1735 let e = fields[0].ty(tcx, substs);
1736 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1737 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1738 .span_label(sp, "SIMD elements must have the same type")
1743 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1744 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1746 span_err!(tcx.sess, sp, E0077,
1747 "SIMD vector element type should be machine type");
1755 fn check_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1756 let repr = tcx.adt_def(def_id).repr;
1758 for attr in tcx.get_attrs(def_id).iter() {
1759 for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
1760 if let attr::ReprPacked(pack) = r {
1761 if pack != repr.pack {
1762 struct_span_err!(tcx.sess, sp, E0634,
1763 "type has conflicting packed representation hints").emit();
1769 struct_span_err!(tcx.sess, sp, E0587,
1770 "type has conflicting packed and align representation hints").emit();
1772 else if check_packed_inner(tcx, def_id, &mut Vec::new()) {
1773 struct_span_err!(tcx.sess, sp, E0588,
1774 "packed type cannot transitively contain a `[repr(align)]` type").emit();
1779 fn check_packed_inner<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1781 stack: &mut Vec<DefId>) -> bool {
1782 let t = tcx.type_of(def_id);
1783 if stack.contains(&def_id) {
1784 debug!("check_packed_inner: {:?} is recursive", t);
1787 if let ty::Adt(def, substs) = t.sty {
1788 if def.is_struct() || def.is_union() {
1789 if tcx.adt_def(def.did).repr.align > 0 {
1792 // push struct def_id before checking fields
1794 for field in &def.non_enum_variant().fields {
1795 let f = field.ty(tcx, substs);
1796 if let ty::Adt(def, _) = f.sty {
1797 if check_packed_inner(tcx, def.did, stack) {
1802 // only need to pop if not early out
1809 fn check_transparent<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, sp: Span, def_id: DefId) {
1810 let adt = tcx.adt_def(def_id);
1811 if !adt.repr.transparent() {
1815 // For each field, figure out if it's known to be a ZST and align(1)
1816 let field_infos = adt.non_enum_variant().fields.iter().map(|field| {
1817 let ty = field.ty(tcx, Substs::identity_for_item(tcx, field.did));
1818 let param_env = tcx.param_env(field.did);
1819 let layout = tcx.layout_of(param_env.and(ty));
1820 // We are currently checking the type this field came from, so it must be local
1821 let span = tcx.hir().span_if_local(field.did).unwrap();
1822 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
1823 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
1827 let non_zst_fields = field_infos.clone().filter(|(_span, zst, _align1)| !*zst);
1828 let non_zst_count = non_zst_fields.clone().count();
1829 if non_zst_count != 1 {
1830 let field_spans: Vec<_> = non_zst_fields.map(|(span, _zst, _align1)| span).collect();
1831 struct_span_err!(tcx.sess, sp, E0690,
1832 "transparent struct needs exactly one non-zero-sized field, but has {}",
1834 .span_note(field_spans, "non-zero-sized field")
1837 for (span, zst, align1) in field_infos {
1839 span_err!(tcx.sess, span, E0691,
1840 "zero-sized field in transparent struct has alignment larger than 1");
1845 #[allow(trivial_numeric_casts)]
1846 pub fn check_enum<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1848 vs: &'tcx [hir::Variant],
1850 let def_id = tcx.hir().local_def_id(id);
1851 let def = tcx.adt_def(def_id);
1852 def.destructor(tcx); // force the destructor to be evaluated
1855 let attributes = tcx.get_attrs(def_id);
1856 if let Some(attr) = attr::find_by_name(&attributes, "repr") {
1858 tcx.sess, attr.span, E0084,
1859 "unsupported representation for zero-variant enum")
1860 .span_label(sp, "zero-variant enum")
1865 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1866 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1867 if !tcx.features().repr128 {
1868 emit_feature_err(&tcx.sess.parse_sess,
1871 GateIssue::Language,
1872 "repr with 128-bit type is unstable");
1877 if let Some(ref e) = v.node.disr_expr {
1878 tcx.typeck_tables_of(tcx.hir().local_def_id(e.id));
1882 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
1883 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
1884 // Check for duplicate discriminant values
1885 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
1886 let variant_did = def.variants[VariantIdx::new(i)].did;
1887 let variant_i_node_id = tcx.hir().as_local_node_id(variant_did).unwrap();
1888 let variant_i = tcx.hir().expect_variant(variant_i_node_id);
1889 let i_span = match variant_i.node.disr_expr {
1890 Some(ref expr) => tcx.hir().span(expr.id),
1891 None => tcx.hir().span(variant_i_node_id)
1893 let span = match v.node.disr_expr {
1894 Some(ref expr) => tcx.hir().span(expr.id),
1897 struct_span_err!(tcx.sess, span, E0081,
1898 "discriminant value `{}` already exists", disr_vals[i])
1899 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1900 .span_label(span , format!("enum already has `{}`", disr_vals[i]))
1903 disr_vals.push(discr);
1906 check_representable(tcx, sp, def_id);
1909 fn report_unexpected_variant_def<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1913 span_err!(tcx.sess, span, E0533,
1914 "expected unit struct/variant or constant, found {} `{}`",
1916 hir::print::to_string(tcx.hir(), |s| s.print_qpath(qpath, false)));
1919 impl<'a, 'gcx, 'tcx> AstConv<'gcx, 'tcx> for FnCtxt<'a, 'gcx, 'tcx> {
1920 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.tcx }
1922 fn get_type_parameter_bounds(&self, _: Span, def_id: DefId)
1923 -> Lrc<ty::GenericPredicates<'tcx>>
1926 let node_id = tcx.hir().as_local_node_id(def_id).unwrap();
1927 let item_id = tcx.hir().ty_param_owner(node_id);
1928 let item_def_id = tcx.hir().local_def_id(item_id);
1929 let generics = tcx.generics_of(item_def_id);
1930 let index = generics.param_def_id_to_index[&def_id];
1931 Lrc::new(ty::GenericPredicates {
1933 predicates: self.param_env.caller_bounds.iter().filter_map(|&predicate| {
1935 ty::Predicate::Trait(ref data)
1936 if data.skip_binder().self_ty().is_param(index) => {
1937 // HACK(eddyb) should get the original `Span`.
1938 let span = tcx.def_span(def_id);
1939 Some((predicate, span))
1947 fn re_infer(&self, span: Span, def: Option<&ty::GenericParamDef>)
1948 -> Option<ty::Region<'tcx>> {
1950 Some(def) => infer::EarlyBoundRegion(span, def.name),
1951 None => infer::MiscVariable(span)
1953 Some(self.next_region_var(v))
1956 fn ty_infer(&self, span: Span) -> Ty<'tcx> {
1957 self.next_ty_var(TypeVariableOrigin::TypeInference(span))
1960 fn ty_infer_for_def(&self,
1961 ty_param_def: &ty::GenericParamDef,
1962 span: Span) -> Ty<'tcx> {
1963 if let UnpackedKind::Type(ty) = self.var_for_def(span, ty_param_def).unpack() {
1969 fn projected_ty_from_poly_trait_ref(&self,
1972 poly_trait_ref: ty::PolyTraitRef<'tcx>)
1975 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
1977 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
1981 self.tcx().mk_projection(item_def_id, trait_ref.substs)
1984 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
1985 if ty.has_escaping_bound_vars() {
1986 ty // FIXME: normalization and escaping regions
1988 self.normalize_associated_types_in(span, &ty)
1992 fn set_tainted_by_errors(&self) {
1993 self.infcx.set_tainted_by_errors()
1996 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
1997 self.write_ty(hir_id, ty)
2001 /// Controls whether the arguments are tupled. This is used for the call
2004 /// Tupling means that all call-side arguments are packed into a tuple and
2005 /// passed as a single parameter. For example, if tupling is enabled, this
2008 /// fn f(x: (isize, isize))
2010 /// Can be called as:
2017 #[derive(Clone, Eq, PartialEq)]
2018 enum TupleArgumentsFlag {
2023 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
2024 pub fn new(inh: &'a Inherited<'a, 'gcx, 'tcx>,
2025 param_env: ty::ParamEnv<'tcx>,
2026 body_id: ast::NodeId)
2027 -> FnCtxt<'a, 'gcx, 'tcx> {
2031 err_count_on_creation: inh.tcx.sess.err_count(),
2033 ret_coercion_span: RefCell::new(None),
2035 ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
2036 ast::CRATE_NODE_ID)),
2037 diverges: Cell::new(Diverges::Maybe),
2038 has_errors: Cell::new(false),
2039 enclosing_breakables: RefCell::new(EnclosingBreakables {
2041 by_id: Default::default(),
2047 pub fn sess(&self) -> &Session {
2051 pub fn err_count_since_creation(&self) -> usize {
2052 self.tcx.sess.err_count() - self.err_count_on_creation
2055 /// Produce warning on the given node, if the current point in the
2056 /// function is unreachable, and there hasn't been another warning.
2057 fn warn_if_unreachable(&self, id: ast::NodeId, span: Span, kind: &str) {
2058 if self.diverges.get() == Diverges::Always {
2059 self.diverges.set(Diverges::WarnedAlways);
2061 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
2063 self.tcx().lint_node(
2064 lint::builtin::UNREACHABLE_CODE,
2066 &format!("unreachable {}", kind));
2072 code: ObligationCauseCode<'tcx>)
2073 -> ObligationCause<'tcx> {
2074 ObligationCause::new(span, self.body_id, code)
2077 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
2078 self.cause(span, ObligationCauseCode::MiscObligation)
2081 /// Resolves type variables in `ty` if possible. Unlike the infcx
2082 /// version (resolve_type_vars_if_possible), this version will
2083 /// also select obligations if it seems useful, in an effort
2084 /// to get more type information.
2085 fn resolve_type_vars_with_obligations(&self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
2086 debug!("resolve_type_vars_with_obligations(ty={:?})", ty);
2088 // No Infer()? Nothing needs doing.
2089 if !ty.has_infer_types() {
2090 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2094 // If `ty` is a type variable, see whether we already know what it is.
2095 ty = self.resolve_type_vars_if_possible(&ty);
2096 if !ty.has_infer_types() {
2097 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2101 // If not, try resolving pending obligations as much as
2102 // possible. This can help substantially when there are
2103 // indirect dependencies that don't seem worth tracking
2105 self.select_obligations_where_possible(false);
2106 ty = self.resolve_type_vars_if_possible(&ty);
2108 debug!("resolve_type_vars_with_obligations: ty={:?}", ty);
2112 fn record_deferred_call_resolution(&self,
2113 closure_def_id: DefId,
2114 r: DeferredCallResolution<'gcx, 'tcx>) {
2115 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2116 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
2119 fn remove_deferred_call_resolutions(&self,
2120 closure_def_id: DefId)
2121 -> Vec<DeferredCallResolution<'gcx, 'tcx>>
2123 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
2124 deferred_call_resolutions.remove(&closure_def_id).unwrap_or(vec![])
2127 pub fn tag(&self) -> String {
2128 let self_ptr: *const FnCtxt = self;
2129 format!("{:?}", self_ptr)
2132 pub fn local_ty(&self, span: Span, nid: ast::NodeId) -> LocalTy<'tcx> {
2133 self.locals.borrow().get(&nid).cloned().unwrap_or_else(||
2134 span_bug!(span, "no type for local variable {}",
2135 self.tcx.hir().node_to_string(nid))
2140 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
2141 debug!("write_ty({:?}, {:?}) in fcx {}",
2142 id, self.resolve_type_vars_if_possible(&ty), self.tag());
2143 self.tables.borrow_mut().node_types_mut().insert(id, ty);
2145 if ty.references_error() {
2146 self.has_errors.set(true);
2147 self.set_tainted_by_errors();
2151 pub fn write_field_index(&self, node_id: ast::NodeId, index: usize) {
2152 let hir_id = self.tcx.hir().node_to_hir_id(node_id);
2153 self.tables.borrow_mut().field_indices_mut().insert(hir_id, index);
2156 pub fn write_method_call(&self,
2158 method: MethodCallee<'tcx>) {
2159 debug!("write_method_call(hir_id={:?}, method={:?})", hir_id, method);
2162 .type_dependent_defs_mut()
2163 .insert(hir_id, Def::Method(method.def_id));
2165 self.write_substs(hir_id, method.substs);
2167 // When the method is confirmed, the `method.substs` includes
2168 // parameters from not just the method, but also the impl of
2169 // the method -- in particular, the `Self` type will be fully
2170 // resolved. However, those are not something that the "user
2171 // specified" -- i.e., those types come from the inferred type
2172 // of the receiver, not something the user wrote. So when we
2173 // create the user-substs, we want to replace those earlier
2174 // types with just the types that the user actually wrote --
2175 // that is, those that appear on the *method itself*.
2177 // As an example, if the user wrote something like
2178 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
2179 // type of `foo` (possibly adjusted), but we don't want to
2180 // include that. We want just the `[_, u32]` part.
2181 if !method.substs.is_noop() {
2182 let method_generics = self.tcx.generics_of(method.def_id);
2183 if !method_generics.params.is_empty() {
2184 let user_type_annotation = self.infcx.probe(|_| {
2185 let user_substs = UserSubsts {
2186 substs: Substs::for_item(self.tcx, method.def_id, |param, _| {
2187 let i = param.index as usize;
2188 if i < method_generics.parent_count {
2189 self.infcx.var_for_def(DUMMY_SP, param)
2194 user_self_ty: None, // not relevant here
2197 self.infcx.canonicalize_user_type_annotation(&UserTypeAnnotation::TypeOf(
2203 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
2204 self.write_user_type_annotation(hir_id, user_type_annotation);
2209 pub fn write_substs(&self, node_id: hir::HirId, substs: &'tcx Substs<'tcx>) {
2210 if !substs.is_noop() {
2211 debug!("write_substs({:?}, {:?}) in fcx {}",
2216 self.tables.borrow_mut().node_substs_mut().insert(node_id, substs);
2220 /// Given the substs that we just converted from the HIR, try to
2221 /// canonicalize them and store them as user-given substitutions
2222 /// (i.e., substitutions that must be respected by the NLL check).
2224 /// This should be invoked **before any unifications have
2225 /// occurred**, so that annotations like `Vec<_>` are preserved
2227 pub fn write_user_type_annotation_from_substs(
2231 substs: &'tcx Substs<'tcx>,
2232 user_self_ty: Option<UserSelfTy<'tcx>>,
2235 "write_user_type_annotation_from_substs: hir_id={:?} def_id={:?} substs={:?} \
2236 user_self_ty={:?} in fcx {}",
2237 hir_id, def_id, substs, user_self_ty, self.tag(),
2240 if !substs.is_noop() {
2241 let canonicalized = self.infcx.canonicalize_user_type_annotation(
2242 &UserTypeAnnotation::TypeOf(def_id, UserSubsts {
2247 debug!("write_user_type_annotation_from_substs: canonicalized={:?}", canonicalized);
2248 self.write_user_type_annotation(hir_id, canonicalized);
2252 pub fn write_user_type_annotation(
2255 canonical_user_type_annotation: CanonicalUserTypeAnnotation<'tcx>,
2258 "write_user_type_annotation: hir_id={:?} canonical_user_type_annotation={:?} tag={}",
2259 hir_id, canonical_user_type_annotation, self.tag(),
2262 if !canonical_user_type_annotation.is_identity() {
2263 self.tables.borrow_mut().user_provided_types_mut().insert(
2264 hir_id, canonical_user_type_annotation
2267 debug!("write_user_type_annotation: skipping identity substs");
2271 pub fn apply_adjustments(&self, expr: &hir::Expr, adj: Vec<Adjustment<'tcx>>) {
2272 debug!("apply_adjustments(expr={:?}, adj={:?})", expr, adj);
2278 match self.tables.borrow_mut().adjustments_mut().entry(expr.hir_id) {
2279 Entry::Vacant(entry) => { entry.insert(adj); },
2280 Entry::Occupied(mut entry) => {
2281 debug!(" - composing on top of {:?}", entry.get());
2282 match (&entry.get()[..], &adj[..]) {
2283 // Applying any adjustment on top of a NeverToAny
2284 // is a valid NeverToAny adjustment, because it can't
2286 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
2288 Adjustment { kind: Adjust::Deref(_), .. },
2289 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
2291 Adjustment { kind: Adjust::Deref(_), .. },
2292 .. // Any following adjustments are allowed.
2294 // A reborrow has no effect before a dereference.
2296 // FIXME: currently we never try to compose autoderefs
2297 // and ReifyFnPointer/UnsafeFnPointer, but we could.
2299 bug!("while adjusting {:?}, can't compose {:?} and {:?}",
2300 expr, entry.get(), adj)
2302 *entry.get_mut() = adj;
2307 /// Basically whenever we are converting from a type scheme into
2308 /// the fn body space, we always want to normalize associated
2309 /// types as well. This function combines the two.
2310 fn instantiate_type_scheme<T>(&self,
2312 substs: &Substs<'tcx>,
2315 where T : TypeFoldable<'tcx>
2317 let value = value.subst(self.tcx, substs);
2318 let result = self.normalize_associated_types_in(span, &value);
2319 debug!("instantiate_type_scheme(value={:?}, substs={:?}) = {:?}",
2326 /// As `instantiate_type_scheme`, but for the bounds found in a
2327 /// generic type scheme.
2328 fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: &Substs<'tcx>)
2329 -> ty::InstantiatedPredicates<'tcx> {
2330 let bounds = self.tcx.predicates_of(def_id);
2331 let result = bounds.instantiate(self.tcx, substs);
2332 let result = self.normalize_associated_types_in(span, &result);
2333 debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
2340 /// Replace the opaque types from the given value with type variables,
2341 /// and records the `OpaqueTypeMap` for later use during writeback. See
2342 /// `InferCtxt::instantiate_opaque_types` for more details.
2343 fn instantiate_opaque_types_from_value<T: TypeFoldable<'tcx>>(
2345 parent_id: ast::NodeId,
2348 let parent_def_id = self.tcx.hir().local_def_id(parent_id);
2349 debug!("instantiate_opaque_types_from_value(parent_def_id={:?}, value={:?})",
2353 let (value, opaque_type_map) = self.register_infer_ok_obligations(
2354 self.instantiate_opaque_types(
2362 let mut opaque_types = self.opaque_types.borrow_mut();
2363 for (ty, decl) in opaque_type_map {
2364 let old_value = opaque_types.insert(ty, decl);
2365 assert!(old_value.is_none(), "instantiated twice: {:?}/{:?}", ty, decl);
2371 fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
2372 where T : TypeFoldable<'tcx>
2374 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
2377 fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
2379 where T : TypeFoldable<'tcx>
2381 self.inh.partially_normalize_associated_types_in(span,
2387 pub fn require_type_meets(&self,
2390 code: traits::ObligationCauseCode<'tcx>,
2393 self.register_bound(
2396 traits::ObligationCause::new(span, self.body_id, code));
2399 pub fn require_type_is_sized(&self,
2402 code: traits::ObligationCauseCode<'tcx>)
2404 let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
2405 self.require_type_meets(ty, span, code, lang_item);
2408 pub fn require_type_is_sized_deferred(&self,
2411 code: traits::ObligationCauseCode<'tcx>)
2413 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
2416 pub fn register_bound(&self,
2419 cause: traits::ObligationCause<'tcx>)
2421 self.fulfillment_cx.borrow_mut()
2422 .register_bound(self, self.param_env, ty, def_id, cause);
2425 pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
2426 let t = AstConv::ast_ty_to_ty(self, ast_t);
2427 self.register_wf_obligation(t, ast_t.span, traits::MiscObligation);
2431 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
2432 let ty = self.to_ty(ast_ty);
2433 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
2435 // If the type given by the user has free regions, save it for
2436 // later, since NLL would like to enforce those. Also pass in
2437 // types that involve projections, since those can resolve to
2438 // `'static` bounds (modulo #54940, which hopefully will be
2439 // fixed by the time you see this comment, dear reader,
2440 // although I have my doubts). Other sorts of things are
2441 // already sufficiently enforced with erased regions. =)
2442 if ty.has_free_regions() || ty.has_projections() {
2443 let c_ty = self.infcx.canonicalize_response(&UserTypeAnnotation::Ty(ty));
2444 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
2445 self.tables.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
2451 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
2452 match self.tables.borrow().node_types().get(id) {
2454 None if self.is_tainted_by_errors() => self.tcx.types.err,
2456 let node_id = self.tcx.hir().hir_to_node_id(id);
2457 bug!("no type for node {}: {} in fcx {}",
2458 node_id, self.tcx.hir().node_to_string(node_id),
2464 /// Registers an obligation for checking later, during regionck, that the type `ty` must
2465 /// outlive the region `r`.
2466 pub fn register_wf_obligation(&self,
2469 code: traits::ObligationCauseCode<'tcx>)
2471 // WF obligations never themselves fail, so no real need to give a detailed cause:
2472 let cause = traits::ObligationCause::new(span, self.body_id, code);
2473 self.register_predicate(traits::Obligation::new(cause,
2475 ty::Predicate::WellFormed(ty)));
2478 /// Registers obligations that all types appearing in `substs` are well-formed.
2479 pub fn add_wf_bounds(&self, substs: &Substs<'tcx>, expr: &hir::Expr) {
2480 for ty in substs.types() {
2481 self.register_wf_obligation(ty, expr.span, traits::MiscObligation);
2485 /// Given a fully substituted set of bounds (`generic_bounds`), and the values with which each
2486 /// type/region parameter was instantiated (`substs`), creates and registers suitable
2487 /// trait/region obligations.
2489 /// For example, if there is a function:
2492 /// fn foo<'a,T:'a>(...)
2495 /// and a reference:
2501 /// Then we will create a fresh region variable `'$0` and a fresh type variable `$1` for `'a`
2502 /// and `T`. This routine will add a region obligation `$1:'$0` and register it locally.
2503 pub fn add_obligations_for_parameters(&self,
2504 cause: traits::ObligationCause<'tcx>,
2505 predicates: &ty::InstantiatedPredicates<'tcx>)
2507 assert!(!predicates.has_escaping_bound_vars());
2509 debug!("add_obligations_for_parameters(predicates={:?})",
2512 for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
2513 self.register_predicate(obligation);
2517 // FIXME(arielb1): use this instead of field.ty everywhere
2518 // Only for fields! Returns <none> for methods>
2519 // Indifferent to privacy flags
2520 pub fn field_ty(&self,
2522 field: &'tcx ty::FieldDef,
2523 substs: &Substs<'tcx>)
2526 self.normalize_associated_types_in(span, &field.ty(self.tcx, substs))
2529 fn check_casts(&self) {
2530 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
2531 for cast in deferred_cast_checks.drain(..) {
2536 fn resolve_generator_interiors(&self, def_id: DefId) {
2537 let mut generators = self.deferred_generator_interiors.borrow_mut();
2538 for (body_id, interior) in generators.drain(..) {
2539 self.select_obligations_where_possible(false);
2540 generator_interior::resolve_interior(self, def_id, body_id, interior);
2544 // Tries to apply a fallback to `ty` if it is an unsolved variable.
2545 // Non-numerics get replaced with ! or () (depending on whether
2546 // feature(never_type) is enabled, unconstrained ints with i32,
2547 // unconstrained floats with f64.
2548 // Fallback becomes very dubious if we have encountered type-checking errors.
2549 // In that case, fallback to Error.
2550 // The return value indicates whether fallback has occurred.
2551 fn fallback_if_possible(&self, ty: Ty<'tcx>) -> bool {
2552 use rustc::ty::error::UnconstrainedNumeric::Neither;
2553 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
2555 assert!(ty.is_ty_infer());
2556 let fallback = match self.type_is_unconstrained_numeric(ty) {
2557 _ if self.is_tainted_by_errors() => self.tcx().types.err,
2558 UnconstrainedInt => self.tcx.types.i32,
2559 UnconstrainedFloat => self.tcx.types.f64,
2560 Neither if self.type_var_diverges(ty) => self.tcx.mk_diverging_default(),
2561 Neither => return false,
2563 debug!("default_type_parameters: defaulting `{:?}` to `{:?}`", ty, fallback);
2564 self.demand_eqtype(syntax_pos::DUMMY_SP, ty, fallback);
2568 fn select_all_obligations_or_error(&self) {
2569 debug!("select_all_obligations_or_error");
2570 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_all_or_error(&self) {
2571 self.report_fulfillment_errors(&errors, self.inh.body_id, false);
2575 /// Select as many obligations as we can at present.
2576 fn select_obligations_where_possible(&self, fallback_has_occurred: bool) {
2577 if let Err(errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
2578 self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
2582 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
2583 /// returns a type of `&T`, but the actual type we assign to the
2584 /// *expression* is `T`. So this function just peels off the return
2585 /// type by one layer to yield `T`.
2586 fn make_overloaded_place_return_type(&self,
2587 method: MethodCallee<'tcx>)
2588 -> ty::TypeAndMut<'tcx>
2590 // extract method return type, which will be &T;
2591 let ret_ty = method.sig.output();
2593 // method returns &T, but the type as visible to user is T, so deref
2594 ret_ty.builtin_deref(true).unwrap()
2597 fn lookup_indexing(&self,
2599 base_expr: &'gcx hir::Expr,
2603 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2605 // FIXME(#18741) -- this is almost but not quite the same as the
2606 // autoderef that normal method probing does. They could likely be
2609 let mut autoderef = self.autoderef(base_expr.span, base_ty);
2610 let mut result = None;
2611 while result.is_none() && autoderef.next().is_some() {
2612 result = self.try_index_step(expr, base_expr, &autoderef, needs, idx_ty);
2614 autoderef.finalize(self);
2618 /// To type-check `base_expr[index_expr]`, we progressively autoderef
2619 /// (and otherwise adjust) `base_expr`, looking for a type which either
2620 /// supports builtin indexing or overloaded indexing.
2621 /// This loop implements one step in that search; the autoderef loop
2622 /// is implemented by `lookup_indexing`.
2623 fn try_index_step(&self,
2625 base_expr: &hir::Expr,
2626 autoderef: &Autoderef<'a, 'gcx, 'tcx>,
2629 -> Option<(/*index type*/ Ty<'tcx>, /*element type*/ Ty<'tcx>)>
2631 let adjusted_ty = autoderef.unambiguous_final_ty(self);
2632 debug!("try_index_step(expr={:?}, base_expr={:?}, adjusted_ty={:?}, \
2639 for &unsize in &[false, true] {
2640 let mut self_ty = adjusted_ty;
2642 // We only unsize arrays here.
2643 if let ty::Array(element_ty, _) = adjusted_ty.sty {
2644 self_ty = self.tcx.mk_slice(element_ty);
2650 // If some lookup succeeds, write callee into table and extract index/element
2651 // type from the method signature.
2652 // If some lookup succeeded, install method in table
2653 let input_ty = self.next_ty_var(TypeVariableOrigin::AutoDeref(base_expr.span));
2654 let method = self.try_overloaded_place_op(
2655 expr.span, self_ty, &[input_ty], needs, PlaceOp::Index);
2657 let result = method.map(|ok| {
2658 debug!("try_index_step: success, using overloaded indexing");
2659 let method = self.register_infer_ok_obligations(ok);
2661 let mut adjustments = autoderef.adjust_steps(self, needs);
2662 if let ty::Ref(region, _, r_mutbl) = method.sig.inputs()[0].sty {
2663 let mutbl = match r_mutbl {
2664 hir::MutImmutable => AutoBorrowMutability::Immutable,
2665 hir::MutMutable => AutoBorrowMutability::Mutable {
2666 // Indexing can be desugared to a method call,
2667 // so maybe we could use two-phase here.
2668 // See the documentation of AllowTwoPhase for why that's
2669 // not the case today.
2670 allow_two_phase_borrow: AllowTwoPhase::No,
2673 adjustments.push(Adjustment {
2674 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
2675 target: self.tcx.mk_ref(region, ty::TypeAndMut {
2682 adjustments.push(Adjustment {
2683 kind: Adjust::Unsize,
2684 target: method.sig.inputs()[0]
2687 self.apply_adjustments(base_expr, adjustments);
2689 self.write_method_call(expr.hir_id, method);
2690 (input_ty, self.make_overloaded_place_return_type(method).ty)
2692 if result.is_some() {
2700 fn resolve_place_op(&self, op: PlaceOp, is_mut: bool) -> (Option<DefId>, ast::Ident) {
2701 let (tr, name) = match (op, is_mut) {
2702 (PlaceOp::Deref, false) =>
2703 (self.tcx.lang_items().deref_trait(), "deref"),
2704 (PlaceOp::Deref, true) =>
2705 (self.tcx.lang_items().deref_mut_trait(), "deref_mut"),
2706 (PlaceOp::Index, false) =>
2707 (self.tcx.lang_items().index_trait(), "index"),
2708 (PlaceOp::Index, true) =>
2709 (self.tcx.lang_items().index_mut_trait(), "index_mut"),
2711 (tr, ast::Ident::from_str(name))
2714 fn try_overloaded_place_op(&self,
2717 arg_tys: &[Ty<'tcx>],
2720 -> Option<InferOk<'tcx, MethodCallee<'tcx>>>
2722 debug!("try_overloaded_place_op({:?},{:?},{:?},{:?})",
2728 // Try Mut first, if needed.
2729 let (mut_tr, mut_op) = self.resolve_place_op(op, true);
2730 let method = match (needs, mut_tr) {
2731 (Needs::MutPlace, Some(trait_did)) => {
2732 self.lookup_method_in_trait(span, mut_op, trait_did, base_ty, Some(arg_tys))
2737 // Otherwise, fall back to the immutable version.
2738 let (imm_tr, imm_op) = self.resolve_place_op(op, false);
2739 let method = match (method, imm_tr) {
2740 (None, Some(trait_did)) => {
2741 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
2743 (method, _) => method,
2749 fn check_method_argument_types(&self,
2752 method: Result<MethodCallee<'tcx>, ()>,
2753 args_no_rcvr: &'gcx [hir::Expr],
2754 tuple_arguments: TupleArgumentsFlag,
2755 expected: Expectation<'tcx>)
2757 let has_error = match method {
2759 method.substs.references_error() || method.sig.references_error()
2764 let err_inputs = self.err_args(args_no_rcvr.len());
2766 let err_inputs = match tuple_arguments {
2767 DontTupleArguments => err_inputs,
2768 TupleArguments => vec![self.tcx.intern_tup(&err_inputs[..])],
2771 self.check_argument_types(sp, expr_sp, &err_inputs[..], &[], args_no_rcvr,
2772 false, tuple_arguments, None);
2773 return self.tcx.types.err;
2776 let method = method.unwrap();
2777 // HACK(eddyb) ignore self in the definition (see above).
2778 let expected_arg_tys = self.expected_inputs_for_expected_output(
2781 method.sig.output(),
2782 &method.sig.inputs()[1..]
2784 self.check_argument_types(sp, expr_sp, &method.sig.inputs()[1..], &expected_arg_tys[..],
2785 args_no_rcvr, method.sig.variadic, tuple_arguments,
2786 self.tcx.hir().span_if_local(method.def_id));
2790 fn self_type_matches_expected_vid(
2792 trait_ref: ty::PolyTraitRef<'tcx>,
2793 expected_vid: ty::TyVid,
2795 let self_ty = self.shallow_resolve(trait_ref.self_ty());
2797 "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})",
2798 trait_ref, self_ty, expected_vid
2801 ty::Infer(ty::TyVar(found_vid)) => {
2802 // FIXME: consider using `sub_root_var` here so we
2803 // can see through subtyping.
2804 let found_vid = self.root_var(found_vid);
2805 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
2806 expected_vid == found_vid
2812 fn obligations_for_self_ty<'b>(&'b self, self_ty: ty::TyVid)
2813 -> impl Iterator<Item=(ty::PolyTraitRef<'tcx>, traits::PredicateObligation<'tcx>)>
2814 + Captures<'gcx> + 'b
2816 // FIXME: consider using `sub_root_var` here so we
2817 // can see through subtyping.
2818 let ty_var_root = self.root_var(self_ty);
2819 debug!("obligations_for_self_ty: self_ty={:?} ty_var_root={:?} pending_obligations={:?}",
2820 self_ty, ty_var_root,
2821 self.fulfillment_cx.borrow().pending_obligations());
2825 .pending_obligations()
2827 .filter_map(move |obligation| match obligation.predicate {
2828 ty::Predicate::Projection(ref data) =>
2829 Some((data.to_poly_trait_ref(self.tcx), obligation)),
2830 ty::Predicate::Trait(ref data) =>
2831 Some((data.to_poly_trait_ref(), obligation)),
2832 ty::Predicate::Subtype(..) => None,
2833 ty::Predicate::RegionOutlives(..) => None,
2834 ty::Predicate::TypeOutlives(..) => None,
2835 ty::Predicate::WellFormed(..) => None,
2836 ty::Predicate::ObjectSafe(..) => None,
2837 ty::Predicate::ConstEvaluatable(..) => None,
2838 // N.B., this predicate is created by breaking down a
2839 // `ClosureType: FnFoo()` predicate, where
2840 // `ClosureType` represents some `Closure`. It can't
2841 // possibly be referring to the current closure,
2842 // because we haven't produced the `Closure` for
2843 // this closure yet; this is exactly why the other
2844 // code is looking for a self type of a unresolved
2845 // inference variable.
2846 ty::Predicate::ClosureKind(..) => None,
2847 }).filter(move |(tr, _)| self.self_type_matches_expected_vid(*tr, ty_var_root))
2850 fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
2851 self.obligations_for_self_ty(self_ty).any(|(tr, _)| {
2852 Some(tr.def_id()) == self.tcx.lang_items().sized_trait()
2856 /// Generic function that factors out common logic from function calls,
2857 /// method calls and overloaded operators.
2858 fn check_argument_types(&self,
2861 fn_inputs: &[Ty<'tcx>],
2862 mut expected_arg_tys: &[Ty<'tcx>],
2863 args: &'gcx [hir::Expr],
2865 tuple_arguments: TupleArgumentsFlag,
2866 def_span: Option<Span>) {
2869 // Grab the argument types, supplying fresh type variables
2870 // if the wrong number of arguments were supplied
2871 let supplied_arg_count = if tuple_arguments == DontTupleArguments {
2877 // All the input types from the fn signature must outlive the call
2878 // so as to validate implied bounds.
2879 for &fn_input_ty in fn_inputs {
2880 self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
2883 let expected_arg_count = fn_inputs.len();
2885 let param_count_error = |expected_count: usize,
2890 let mut err = tcx.sess.struct_span_err_with_code(sp,
2891 &format!("this function takes {}{} but {} {} supplied",
2892 if variadic {"at least "} else {""},
2893 potentially_plural_count(expected_count, "parameter"),
2894 potentially_plural_count(arg_count, "parameter"),
2895 if arg_count == 1 {"was"} else {"were"}),
2896 DiagnosticId::Error(error_code.to_owned()));
2898 if let Some(def_s) = def_span.map(|sp| tcx.sess.source_map().def_span(sp)) {
2899 err.span_label(def_s, "defined here");
2902 let sugg_span = tcx.sess.source_map().end_point(expr_sp);
2903 // remove closing `)` from the span
2904 let sugg_span = sugg_span.shrink_to_lo();
2905 err.span_suggestion_with_applicability(
2907 "expected the unit value `()`; create it with empty parentheses",
2909 Applicability::MachineApplicable);
2911 err.span_label(sp, format!("expected {}{}",
2912 if variadic {"at least "} else {""},
2913 potentially_plural_count(expected_count, "parameter")));
2918 let formal_tys = if tuple_arguments == TupleArguments {
2919 let tuple_type = self.structurally_resolved_type(sp, fn_inputs[0]);
2920 match tuple_type.sty {
2921 ty::Tuple(arg_types) if arg_types.len() != args.len() => {
2922 param_count_error(arg_types.len(), args.len(), "E0057", false, false);
2923 expected_arg_tys = &[];
2924 self.err_args(args.len())
2926 ty::Tuple(arg_types) => {
2927 expected_arg_tys = match expected_arg_tys.get(0) {
2928 Some(&ty) => match ty.sty {
2929 ty::Tuple(ref tys) => &tys,
2937 span_err!(tcx.sess, sp, E0059,
2938 "cannot use call notation; the first type parameter \
2939 for the function trait is neither a tuple nor unit");
2940 expected_arg_tys = &[];
2941 self.err_args(args.len())
2944 } else if expected_arg_count == supplied_arg_count {
2946 } else if variadic {
2947 if supplied_arg_count >= expected_arg_count {
2950 param_count_error(expected_arg_count, supplied_arg_count, "E0060", true, false);
2951 expected_arg_tys = &[];
2952 self.err_args(supplied_arg_count)
2955 // is the missing argument of type `()`?
2956 let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
2957 self.resolve_type_vars_if_possible(&expected_arg_tys[0]).is_unit()
2958 } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
2959 self.resolve_type_vars_if_possible(&fn_inputs[0]).is_unit()
2963 param_count_error(expected_arg_count, supplied_arg_count, "E0061", false, sugg_unit);
2965 expected_arg_tys = &[];
2966 self.err_args(supplied_arg_count)
2968 // If there is no expectation, expect formal_tys.
2969 let expected_arg_tys = if !expected_arg_tys.is_empty() {
2975 debug!("check_argument_types: formal_tys={:?}",
2976 formal_tys.iter().map(|t| self.ty_to_string(*t)).collect::<Vec<String>>());
2978 // Check the arguments.
2979 // We do this in a pretty awful way: first we type-check any arguments
2980 // that are not closures, then we type-check the closures. This is so
2981 // that we have more information about the types of arguments when we
2982 // type-check the functions. This isn't really the right way to do this.
2983 for &check_closures in &[false, true] {
2984 debug!("check_closures={}", check_closures);
2986 // More awful hacks: before we check argument types, try to do
2987 // an "opportunistic" vtable resolution of any trait bounds on
2988 // the call. This helps coercions.
2990 self.select_obligations_where_possible(false);
2993 // For variadic functions, we don't have a declared type for all of
2994 // the arguments hence we only do our usual type checking with
2995 // the arguments who's types we do know.
2996 let t = if variadic {
2998 } else if tuple_arguments == TupleArguments {
3003 for (i, arg) in args.iter().take(t).enumerate() {
3004 // Warn only for the first loop (the "no closures" one).
3005 // Closure arguments themselves can't be diverging, but
3006 // a previous argument can, e.g., `foo(panic!(), || {})`.
3007 if !check_closures {
3008 self.warn_if_unreachable(arg.id, arg.span, "expression");
3011 let is_closure = match arg.node {
3012 ExprKind::Closure(..) => true,
3016 if is_closure != check_closures {
3020 debug!("checking the argument");
3021 let formal_ty = formal_tys[i];
3023 // The special-cased logic below has three functions:
3024 // 1. Provide as good of an expected type as possible.
3025 let expected = Expectation::rvalue_hint(self, expected_arg_tys[i]);
3027 let checked_ty = self.check_expr_with_expectation(&arg, expected);
3029 // 2. Coerce to the most detailed type that could be coerced
3030 // to, which is `expected_ty` if `rvalue_hint` returns an
3031 // `ExpectHasType(expected_ty)`, or the `formal_ty` otherwise.
3032 let coerce_ty = expected.only_has_type(self).unwrap_or(formal_ty);
3033 // We're processing function arguments so we definitely want to use
3034 // two-phase borrows.
3035 self.demand_coerce(&arg, checked_ty, coerce_ty, AllowTwoPhase::Yes);
3037 // 3. Relate the expected type and the formal one,
3038 // if the expected type was used for the coercion.
3039 self.demand_suptype(arg.span, formal_ty, coerce_ty);
3043 // We also need to make sure we at least write the ty of the other
3044 // arguments which we skipped above.
3046 fn variadic_error<'tcx>(s: &Session, span: Span, t: Ty<'tcx>, cast_ty: &str) {
3047 use structured_errors::{VariadicError, StructuredDiagnostic};
3048 VariadicError::new(s, span, t, cast_ty).diagnostic().emit();
3051 for arg in args.iter().skip(expected_arg_count) {
3052 let arg_ty = self.check_expr(&arg);
3054 // There are a few types which get autopromoted when passed via varargs
3055 // in C but we just error out instead and require explicit casts.
3056 let arg_ty = self.structurally_resolved_type(arg.span, arg_ty);
3058 ty::Float(ast::FloatTy::F32) => {
3059 variadic_error(tcx.sess, arg.span, arg_ty, "c_double");
3061 ty::Int(ast::IntTy::I8) | ty::Int(ast::IntTy::I16) | ty::Bool => {
3062 variadic_error(tcx.sess, arg.span, arg_ty, "c_int");
3064 ty::Uint(ast::UintTy::U8) | ty::Uint(ast::UintTy::U16) => {
3065 variadic_error(tcx.sess, arg.span, arg_ty, "c_uint");
3068 let ptr_ty = self.tcx.mk_fn_ptr(arg_ty.fn_sig(self.tcx));
3069 let ptr_ty = self.resolve_type_vars_if_possible(&ptr_ty);
3070 variadic_error(tcx.sess, arg.span, arg_ty, &ptr_ty.to_string());
3078 fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
3079 vec![self.tcx.types.err; len]
3082 // AST fragment checking
3085 expected: Expectation<'tcx>)
3091 ast::LitKind::Str(..) => tcx.mk_static_str(),
3092 ast::LitKind::ByteStr(ref v) => {
3093 tcx.mk_imm_ref(tcx.types.re_static,
3094 tcx.mk_array(tcx.types.u8, v.len() as u64))
3096 ast::LitKind::Byte(_) => tcx.types.u8,
3097 ast::LitKind::Char(_) => tcx.types.char,
3098 ast::LitKind::Int(_, ast::LitIntType::Signed(t)) => tcx.mk_mach_int(t),
3099 ast::LitKind::Int(_, ast::LitIntType::Unsigned(t)) => tcx.mk_mach_uint(t),
3100 ast::LitKind::Int(_, ast::LitIntType::Unsuffixed) => {
3101 let opt_ty = expected.to_option(self).and_then(|ty| {
3103 ty::Int(_) | ty::Uint(_) => Some(ty),
3104 ty::Char => Some(tcx.types.u8),
3105 ty::RawPtr(..) => Some(tcx.types.usize),
3106 ty::FnDef(..) | ty::FnPtr(_) => Some(tcx.types.usize),
3110 opt_ty.unwrap_or_else(
3111 || tcx.mk_int_var(self.next_int_var_id()))
3113 ast::LitKind::Float(_, t) => tcx.mk_mach_float(t),
3114 ast::LitKind::FloatUnsuffixed(_) => {
3115 let opt_ty = expected.to_option(self).and_then(|ty| {
3117 ty::Float(_) => Some(ty),
3121 opt_ty.unwrap_or_else(
3122 || tcx.mk_float_var(self.next_float_var_id()))
3124 ast::LitKind::Bool(_) => tcx.types.bool
3128 fn check_expr_eq_type(&self,
3129 expr: &'gcx hir::Expr,
3130 expected: Ty<'tcx>) {
3131 let ty = self.check_expr_with_hint(expr, expected);
3132 self.demand_eqtype(expr.span, expected, ty);
3135 pub fn check_expr_has_type_or_error(&self,
3136 expr: &'gcx hir::Expr,
3137 expected: Ty<'tcx>) -> Ty<'tcx> {
3138 self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected))
3141 fn check_expr_meets_expectation_or_error(&self,
3142 expr: &'gcx hir::Expr,
3143 expected: Expectation<'tcx>) -> Ty<'tcx> {
3144 let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool);
3145 let mut ty = self.check_expr_with_expectation(expr, expected);
3147 // While we don't allow *arbitrary* coercions here, we *do* allow
3148 // coercions from ! to `expected`.
3150 assert!(!self.tables.borrow().adjustments().contains_key(expr.hir_id),
3151 "expression with never type wound up being adjusted");
3152 let adj_ty = self.next_diverging_ty_var(
3153 TypeVariableOrigin::AdjustmentType(expr.span));
3154 self.apply_adjustments(expr, vec![Adjustment {
3155 kind: Adjust::NeverToAny,
3161 if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
3162 // Add help to type error if this is an `if` condition with an assignment.
3163 if let (ExpectIfCondition, &ExprKind::Assign(ref lhs, ref rhs))
3164 = (expected, &expr.node)
3166 let msg = "try comparing for equality";
3167 if let (Ok(left), Ok(right)) = (
3168 self.tcx.sess.source_map().span_to_snippet(lhs.span),
3169 self.tcx.sess.source_map().span_to_snippet(rhs.span))
3171 err.span_suggestion_with_applicability(
3174 format!("{} == {}", left, right),
3175 Applicability::MaybeIncorrect);
3185 fn check_expr_coercable_to_type(&self,
3186 expr: &'gcx hir::Expr,
3187 expected: Ty<'tcx>) -> Ty<'tcx> {
3188 let ty = self.check_expr_with_hint(expr, expected);
3189 // checks don't need two phase
3190 self.demand_coerce(expr, ty, expected, AllowTwoPhase::No)
3193 fn check_expr_with_hint(&self,
3194 expr: &'gcx hir::Expr,
3195 expected: Ty<'tcx>) -> Ty<'tcx> {
3196 self.check_expr_with_expectation(expr, ExpectHasType(expected))
3199 fn check_expr_with_expectation(&self,
3200 expr: &'gcx hir::Expr,
3201 expected: Expectation<'tcx>) -> Ty<'tcx> {
3202 self.check_expr_with_expectation_and_needs(expr, expected, Needs::None)
3205 fn check_expr(&self, expr: &'gcx hir::Expr) -> Ty<'tcx> {
3206 self.check_expr_with_expectation(expr, NoExpectation)
3209 fn check_expr_with_needs(&self, expr: &'gcx hir::Expr, needs: Needs) -> Ty<'tcx> {
3210 self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs)
3213 // Determine the `Self` type, using fresh variables for all variables
3214 // declared on the impl declaration e.g., `impl<A,B> for Vec<(A,B)>`
3215 // would return `($0, $1)` where `$0` and `$1` are freshly instantiated type
3217 pub fn impl_self_ty(&self,
3218 span: Span, // (potential) receiver for this impl
3220 -> TypeAndSubsts<'tcx> {
3221 let ity = self.tcx.type_of(did);
3222 debug!("impl_self_ty: ity={:?}", ity);
3224 let substs = self.fresh_substs_for_item(span, did);
3225 let substd_ty = self.instantiate_type_scheme(span, &substs, &ity);
3227 TypeAndSubsts { substs: substs, ty: substd_ty }
3230 /// Unifies the output type with the expected type early, for more coercions
3231 /// and forward type information on the input expressions.
3232 fn expected_inputs_for_expected_output(&self,
3234 expected_ret: Expectation<'tcx>,
3235 formal_ret: Ty<'tcx>,
3236 formal_args: &[Ty<'tcx>])
3238 let formal_ret = self.resolve_type_vars_with_obligations(formal_ret);
3239 let ret_ty = match expected_ret.only_has_type(self) {
3241 None => return Vec::new()
3243 let expect_args = self.fudge_regions_if_ok(&RegionVariableOrigin::Coercion(call_span), || {
3244 // Attempt to apply a subtyping relationship between the formal
3245 // return type (likely containing type variables if the function
3246 // is polymorphic) and the expected return type.
3247 // No argument expectations are produced if unification fails.
3248 let origin = self.misc(call_span);
3249 let ures = self.at(&origin, self.param_env).sup(ret_ty, &formal_ret);
3251 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
3252 // to identity so the resulting type is not constrained.
3255 // Process any obligations locally as much as
3256 // we can. We don't care if some things turn
3257 // out unconstrained or ambiguous, as we're
3258 // just trying to get hints here.
3259 self.save_and_restore_in_snapshot_flag(|_| {
3260 let mut fulfill = TraitEngine::new(self.tcx);
3261 for obligation in ok.obligations {
3262 fulfill.register_predicate_obligation(self, obligation);
3264 fulfill.select_where_possible(self)
3265 }).map_err(|_| ())?;
3267 Err(_) => return Err(()),
3270 // Record all the argument types, with the substitutions
3271 // produced from the above subtyping unification.
3272 Ok(formal_args.iter().map(|ty| {
3273 self.resolve_type_vars_if_possible(ty)
3275 }).unwrap_or_default();
3276 debug!("expected_inputs_for_expected_output(formal={:?} -> {:?}, expected={:?} -> {:?})",
3277 formal_args, formal_ret,
3278 expect_args, expected_ret);
3282 // Checks a method call.
3283 fn check_method_call(&self,
3284 expr: &'gcx hir::Expr,
3285 segment: &hir::PathSegment,
3287 args: &'gcx [hir::Expr],
3288 expected: Expectation<'tcx>,
3289 needs: Needs) -> Ty<'tcx> {
3290 let rcvr = &args[0];
3291 let rcvr_t = self.check_expr_with_needs(&rcvr, needs);
3292 // no need to check for bot/err -- callee does that
3293 let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
3295 let method = match self.lookup_method(rcvr_t,
3301 self.write_method_call(expr.hir_id, method);
3305 if segment.ident.name != keywords::Invalid.name() {
3306 self.report_method_error(span,
3309 SelfSource::MethodCall(rcvr),
3317 // Call the generic checker.
3318 self.check_method_argument_types(span,
3326 fn check_return_expr(&self, return_expr: &'gcx hir::Expr) {
3330 .unwrap_or_else(|| span_bug!(return_expr.span,
3331 "check_return_expr called outside fn body"));
3333 let ret_ty = ret_coercion.borrow().expected_ty();
3334 let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty.clone());
3335 ret_coercion.borrow_mut()
3337 &self.cause(return_expr.span,
3338 ObligationCauseCode::ReturnType(return_expr.id)),
3343 // A generic function for checking the 'then' and 'else' clauses in an 'if'
3344 // or 'if-else' expression.
3345 fn check_then_else(&self,
3346 cond_expr: &'gcx hir::Expr,
3347 then_expr: &'gcx hir::Expr,
3348 opt_else_expr: Option<&'gcx hir::Expr>,
3350 expected: Expectation<'tcx>) -> Ty<'tcx> {
3351 let cond_ty = self.check_expr_meets_expectation_or_error(cond_expr, ExpectIfCondition);
3352 let cond_diverges = self.diverges.get();
3353 self.diverges.set(Diverges::Maybe);
3355 let expected = expected.adjust_for_branches(self);
3356 let then_ty = self.check_expr_with_expectation(then_expr, expected);
3357 let then_diverges = self.diverges.get();
3358 self.diverges.set(Diverges::Maybe);
3360 // We've already taken the expected type's preferences
3361 // into account when typing the `then` branch. To figure
3362 // out the initial shot at a LUB, we thus only consider
3363 // `expected` if it represents a *hard* constraint
3364 // (`only_has_type`); otherwise, we just go with a
3365 // fresh type variable.
3366 let coerce_to_ty = expected.coercion_target_type(self, sp);
3367 let mut coerce: DynamicCoerceMany = CoerceMany::new(coerce_to_ty);
3369 coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
3371 if let Some(else_expr) = opt_else_expr {
3372 let else_ty = self.check_expr_with_expectation(else_expr, expected);
3373 let else_diverges = self.diverges.get();
3375 let mut outer_sp = if self.tcx.sess.source_map().is_multiline(sp) {
3376 // The `if`/`else` isn't in one line in the output, include some context to make it
3377 // clear it is an if/else expression:
3379 // LL | let x = if true {
3382 // || ----- expected because of this
3385 // || ^^^^^ expected i32, found u32
3387 // ||_____- if and else have incompatible types
3391 // The entire expression is in one line, only point at the arms
3393 // LL | let x = if true { 10i32 } else { 10u32 };
3394 // | ----- ^^^^^ expected i32, found u32
3396 // | expected because of this
3400 let mut remove_semicolon = None;
3401 let error_sp = if let ExprKind::Block(block, _) = &else_expr.node {
3402 if let Some(expr) = &block.expr {
3404 } else if let Some(stmt) = block.stmts.last() {
3405 // possibly incorrect trailing `;` in the else arm
3406 remove_semicolon = self.could_remove_semicolon(block, then_ty);
3408 } else { // empty block, point at its entirety
3409 // Avoid overlapping spans that aren't as readable:
3411 // 2 | let x = if true {
3414 // | | - expected because of this
3421 // | |______if and else have incompatible types
3422 // | expected integer, found ()
3424 // by not pointing at the entire expression:
3426 // 2 | let x = if true {
3427 // | ------- if and else have incompatible types
3429 // | - expected because of this
3434 // | |_____^ expected integer, found ()
3436 if outer_sp.is_some() {
3437 outer_sp = Some(self.tcx.sess.source_map().def_span(sp));
3441 } else { // shouldn't happen unless the parser has done something weird
3444 let then_sp = if let ExprKind::Block(block, _) = &then_expr.node {
3445 if let Some(expr) = &block.expr {
3447 } else if let Some(stmt) = block.stmts.last() {
3448 // possibly incorrect trailing `;` in the else arm
3449 remove_semicolon = remove_semicolon.or(
3450 self.could_remove_semicolon(block, else_ty));
3452 } else { // empty block, point at its entirety
3453 outer_sp = None; // same as in `error_sp`, cleanup output
3456 } else { // shouldn't happen unless the parser has done something weird
3460 let if_cause = self.cause(error_sp, ObligationCauseCode::IfExpression {
3463 semicolon: remove_semicolon,
3466 coerce.coerce(self, &if_cause, else_expr, else_ty);
3468 // We won't diverge unless both branches do (or the condition does).
3469 self.diverges.set(cond_diverges | then_diverges & else_diverges);
3471 let else_cause = self.cause(sp, ObligationCauseCode::IfExpressionWithNoElse);
3472 coerce.coerce_forced_unit(self, &else_cause, &mut |_| (), true);
3474 // If the condition is false we can't diverge.
3475 self.diverges.set(cond_diverges);
3478 let result_ty = coerce.complete(self);
3479 if cond_ty.references_error() {
3486 // Check field access expressions
3487 fn check_field(&self,
3488 expr: &'gcx hir::Expr,
3490 base: &'gcx hir::Expr,
3491 field: ast::Ident) -> Ty<'tcx> {
3492 let expr_t = self.check_expr_with_needs(base, needs);
3493 let expr_t = self.structurally_resolved_type(base.span,
3495 let mut private_candidate = None;
3496 let mut autoderef = self.autoderef(expr.span, expr_t);
3497 while let Some((base_t, _)) = autoderef.next() {
3499 ty::Adt(base_def, substs) if !base_def.is_enum() => {
3500 debug!("struct named {:?}", base_t);
3501 let (ident, def_scope) =
3502 self.tcx.adjust_ident(field, base_def.did, self.body_id);
3503 let fields = &base_def.non_enum_variant().fields;
3504 if let Some(index) = fields.iter().position(|f| f.ident.modern() == ident) {
3505 let field = &fields[index];
3506 let field_ty = self.field_ty(expr.span, field, substs);
3507 // Save the index of all fields regardless of their visibility in case
3508 // of error recovery.
3509 self.write_field_index(expr.id, index);
3510 if field.vis.is_accessible_from(def_scope, self.tcx) {
3511 let adjustments = autoderef.adjust_steps(self, needs);
3512 self.apply_adjustments(base, adjustments);
3513 autoderef.finalize(self);
3515 self.tcx.check_stability(field.did, Some(expr.id), expr.span);
3518 private_candidate = Some((base_def.did, field_ty));
3521 ty::Tuple(ref tys) => {
3522 let fstr = field.as_str();
3523 if let Ok(index) = fstr.parse::<usize>() {
3524 if fstr == index.to_string() {
3525 if let Some(field_ty) = tys.get(index) {
3526 let adjustments = autoderef.adjust_steps(self, needs);
3527 self.apply_adjustments(base, adjustments);
3528 autoderef.finalize(self);
3530 self.write_field_index(expr.id, index);
3539 autoderef.unambiguous_final_ty(self);
3541 if let Some((did, field_ty)) = private_candidate {
3542 let struct_path = self.tcx().item_path_str(did);
3543 let mut err = struct_span_err!(self.tcx().sess, expr.span, E0616,
3544 "field `{}` of struct `{}` is private",
3545 field, struct_path);
3546 // Also check if an accessible method exists, which is often what is meant.
3547 if self.method_exists(field, expr_t, expr.id, false) && !self.expr_in_place(expr.id) {
3548 self.suggest_method_call(
3550 &format!("a method `{}` also exists, call it with parentheses", field),
3558 } else if field.name == keywords::Invalid.name() {
3559 self.tcx().types.err
3560 } else if self.method_exists(field, expr_t, expr.id, true) {
3561 let mut err = type_error_struct!(self.tcx().sess, field.span, expr_t, E0615,
3562 "attempted to take value of method `{}` on type `{}`",
3565 if !self.expr_in_place(expr.id) {
3566 self.suggest_method_call(
3568 "use parentheses to call the method",
3574 err.help("methods are immutable and cannot be assigned to");
3578 self.tcx().types.err
3580 if !expr_t.is_primitive_ty() {
3581 let mut err = self.no_such_field_err(field.span, field, expr_t);
3584 ty::Adt(def, _) if !def.is_enum() => {
3585 if let Some(suggested_field_name) =
3586 Self::suggest_field_name(def.non_enum_variant(),
3587 &field.as_str(), vec![]) {
3588 err.span_suggestion_with_applicability(
3590 "a field with a similar name exists",
3591 suggested_field_name.to_string(),
3592 Applicability::MaybeIncorrect,
3595 err.span_label(field.span, "unknown field");
3596 let struct_variant_def = def.non_enum_variant();
3597 let field_names = self.available_field_names(struct_variant_def);
3598 if !field_names.is_empty() {
3599 err.note(&format!("available fields are: {}",
3600 self.name_series_display(field_names)));
3604 ty::Array(_, len) => {
3605 if let (Some(len), Ok(user_index)) = (
3606 len.assert_usize(self.tcx),
3607 field.as_str().parse::<u64>()
3609 let base = self.tcx.sess.source_map()
3610 .span_to_snippet(base.span)
3611 .unwrap_or_else(|_| self.tcx.hir().node_to_pretty_string(base.id));
3612 let help = "instead of using tuple indexing, use array indexing";
3613 let suggestion = format!("{}[{}]", base, field);
3614 let applicability = if len < user_index {
3615 Applicability::MachineApplicable
3617 Applicability::MaybeIncorrect
3619 err.span_suggestion_with_applicability(
3620 expr.span, help, suggestion, applicability
3625 let base = self.tcx.sess.source_map()
3626 .span_to_snippet(base.span)
3627 .unwrap_or_else(|_| self.tcx.hir().node_to_pretty_string(base.id));
3628 let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
3629 let suggestion = format!("(*{}).{}", base, field);
3630 err.span_suggestion_with_applicability(
3634 Applicability::MaybeIncorrect,
3641 type_error_struct!(self.tcx().sess, field.span, expr_t, E0610,
3642 "`{}` is a primitive type and therefore doesn't have fields",
3645 self.tcx().types.err
3649 // Return an hint about the closest match in field names
3650 fn suggest_field_name(variant: &'tcx ty::VariantDef,
3652 skip: Vec<LocalInternedString>)
3654 let names = variant.fields.iter().filter_map(|field| {
3655 // ignore already set fields and private fields from non-local crates
3656 if skip.iter().any(|x| *x == field.ident.as_str()) ||
3657 (variant.did.krate != LOCAL_CRATE && field.vis != Visibility::Public) {
3660 Some(&field.ident.name)
3664 find_best_match_for_name(names, field, None)
3667 fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<ast::Name> {
3668 variant.fields.iter().filter(|field| {
3669 let def_scope = self.tcx.adjust_ident(field.ident, variant.did, self.body_id).1;
3670 field.vis.is_accessible_from(def_scope, self.tcx)
3672 .map(|field| field.ident.name)
3676 fn name_series_display(&self, names: Vec<ast::Name>) -> String {
3677 // dynamic limit, to never omit just one field
3678 let limit = if names.len() == 6 { 6 } else { 5 };
3679 let mut display = names.iter().take(limit)
3680 .map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
3681 if names.len() > limit {
3682 display = format!("{} ... and {} others", display, names.len() - limit);
3687 fn no_such_field_err<T: Display>(&self, span: Span, field: T, expr_t: &ty::TyS)
3688 -> DiagnosticBuilder {
3689 type_error_struct!(self.tcx().sess, span, expr_t, E0609,
3690 "no field `{}` on type `{}`",
3694 fn report_unknown_field(&self,
3696 variant: &'tcx ty::VariantDef,
3698 skip_fields: &[hir::Field],
3700 let mut err = self.type_error_struct_with_diag(
3702 |actual| match ty.sty {
3703 ty::Adt(adt, ..) if adt.is_enum() => {
3704 struct_span_err!(self.tcx.sess, field.ident.span, E0559,
3705 "{} `{}::{}` has no field named `{}`",
3706 kind_name, actual, variant.ident, field.ident)
3709 struct_span_err!(self.tcx.sess, field.ident.span, E0560,
3710 "{} `{}` has no field named `{}`",
3711 kind_name, actual, field.ident)
3715 // prevent all specified fields from being suggested
3716 let skip_fields = skip_fields.iter().map(|ref x| x.ident.as_str());
3717 if let Some(field_name) = Self::suggest_field_name(variant,
3718 &field.ident.as_str(),
3719 skip_fields.collect()) {
3720 err.span_suggestion_with_applicability(
3722 "a field with a similar name exists",
3723 field_name.to_string(),
3724 Applicability::MaybeIncorrect,
3728 ty::Adt(adt, ..) => {
3730 err.span_label(field.ident.span,
3731 format!("`{}::{}` does not have this field",
3732 ty, variant.ident));
3734 err.span_label(field.ident.span,
3735 format!("`{}` does not have this field", ty));
3737 let available_field_names = self.available_field_names(variant);
3738 if !available_field_names.is_empty() {
3739 err.note(&format!("available fields are: {}",
3740 self.name_series_display(available_field_names)));
3743 _ => bug!("non-ADT passed to report_unknown_field")
3749 fn check_expr_struct_fields(&self,
3751 expected: Expectation<'tcx>,
3752 expr_id: ast::NodeId,
3754 variant: &'tcx ty::VariantDef,
3755 ast_fields: &'gcx [hir::Field],
3756 check_completeness: bool) -> bool {
3760 self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
3761 .get(0).cloned().unwrap_or(adt_ty);
3762 // re-link the regions that EIfEO can erase.
3763 self.demand_eqtype(span, adt_ty_hint, adt_ty);
3765 let (substs, adt_kind, kind_name) = match &adt_ty.sty {
3766 &ty::Adt(adt, substs) => {
3767 (substs, adt.adt_kind(), adt.variant_descr())
3769 _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
3772 let mut remaining_fields = variant.fields.iter().enumerate().map(|(i, field)|
3773 (field.ident.modern(), (i, field))
3774 ).collect::<FxHashMap<_, _>>();
3776 let mut seen_fields = FxHashMap::default();
3778 let mut error_happened = false;
3780 // Type-check each field.
3781 for field in ast_fields {
3782 let ident = tcx.adjust_ident(field.ident, variant.did, self.body_id).0;
3783 let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
3784 seen_fields.insert(ident, field.span);
3785 self.write_field_index(field.id, i);
3787 // We don't look at stability attributes on
3788 // struct-like enums (yet...), but it's definitely not
3789 // a bug to have constructed one.
3790 if adt_kind != AdtKind::Enum {
3791 tcx.check_stability(v_field.did, Some(expr_id), field.span);
3794 self.field_ty(field.span, v_field, substs)
3796 error_happened = true;
3797 if let Some(prev_span) = seen_fields.get(&ident) {
3798 let mut err = struct_span_err!(self.tcx.sess,
3801 "field `{}` specified more than once",
3804 err.span_label(field.ident.span, "used more than once");
3805 err.span_label(*prev_span, format!("first use of `{}`", ident));
3809 self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name);
3815 // Make sure to give a type to the field even if there's
3816 // an error, so we can continue type-checking.
3817 self.check_expr_coercable_to_type(&field.expr, field_type);
3820 // Make sure the programmer specified correct number of fields.
3821 if kind_name == "union" {
3822 if ast_fields.len() != 1 {
3823 tcx.sess.span_err(span, "union expressions should have exactly one field");
3825 } else if check_completeness && !error_happened && !remaining_fields.is_empty() {
3826 let len = remaining_fields.len();
3828 let mut displayable_field_names = remaining_fields
3830 .map(|ident| ident.as_str())
3831 .collect::<Vec<_>>();
3833 displayable_field_names.sort();
3835 let truncated_fields_error = if len <= 3 {
3838 format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
3841 let remaining_fields_names = displayable_field_names.iter().take(3)
3842 .map(|n| format!("`{}`", n))
3843 .collect::<Vec<_>>()
3846 struct_span_err!(tcx.sess, span, E0063,
3847 "missing field{} {}{} in initializer of `{}`",
3848 if remaining_fields.len() == 1 { "" } else { "s" },
3849 remaining_fields_names,
3850 truncated_fields_error,
3852 .span_label(span, format!("missing {}{}",
3853 remaining_fields_names,
3854 truncated_fields_error))
3860 fn check_struct_fields_on_error(&self,
3861 fields: &'gcx [hir::Field],
3862 base_expr: &'gcx Option<P<hir::Expr>>) {
3863 for field in fields {
3864 self.check_expr(&field.expr);
3866 if let Some(ref base) = *base_expr {
3867 self.check_expr(&base);
3871 pub fn check_struct_path(&self,
3873 node_id: ast::NodeId)
3874 -> Option<(&'tcx ty::VariantDef, Ty<'tcx>)> {
3875 let path_span = match *qpath {
3876 QPath::Resolved(_, ref path) => path.span,
3877 QPath::TypeRelative(ref qself, _) => qself.span
3879 let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, node_id);
3880 let variant = match def {
3882 self.set_tainted_by_errors();
3885 Def::Variant(..) => {
3887 ty::Adt(adt, substs) => {
3888 Some((adt.variant_of_def(def), adt.did, substs))
3890 _ => bug!("unexpected type: {:?}", ty.sty)
3893 Def::Struct(..) | Def::Union(..) | Def::TyAlias(..) |
3894 Def::AssociatedTy(..) | Def::SelfTy(..) => {
3896 ty::Adt(adt, substs) if !adt.is_enum() => {
3897 Some((adt.non_enum_variant(), adt.did, substs))
3902 _ => bug!("unexpected definition: {:?}", def)
3905 if let Some((variant, did, substs)) = variant {
3906 debug!("check_struct_path: did={:?} substs={:?}", did, substs);
3907 let hir_id = self.tcx.hir().node_to_hir_id(node_id);
3908 self.write_user_type_annotation_from_substs(hir_id, did, substs, None);
3910 // Check bounds on type arguments used in the path.
3911 let bounds = self.instantiate_bounds(path_span, did, substs);
3912 let cause = traits::ObligationCause::new(path_span, self.body_id,
3913 traits::ItemObligation(did));
3914 self.add_obligations_for_parameters(cause, &bounds);
3918 struct_span_err!(self.tcx.sess, path_span, E0071,
3919 "expected struct, variant or union type, found {}",
3920 ty.sort_string(self.tcx))
3921 .span_label(path_span, "not a struct")
3927 fn check_expr_struct(&self,
3929 expected: Expectation<'tcx>,
3931 fields: &'gcx [hir::Field],
3932 base_expr: &'gcx Option<P<hir::Expr>>) -> Ty<'tcx>
3934 // Find the relevant variant
3935 let (variant, adt_ty) =
3936 if let Some(variant_ty) = self.check_struct_path(qpath, expr.id) {
3939 self.check_struct_fields_on_error(fields, base_expr);
3940 return self.tcx.types.err;
3943 let path_span = match *qpath {
3944 QPath::Resolved(_, ref path) => path.span,
3945 QPath::TypeRelative(ref qself, _) => qself.span
3948 // Prohibit struct expressions when non-exhaustive flag is set.
3949 let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
3950 if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
3951 span_err!(self.tcx.sess, expr.span, E0639,
3952 "cannot create non-exhaustive {} using struct expression",
3953 adt.variant_descr());
3956 let error_happened = self.check_expr_struct_fields(adt_ty, expected, expr.id, path_span,
3957 variant, fields, base_expr.is_none());
3958 if let &Some(ref base_expr) = base_expr {
3959 // If check_expr_struct_fields hit an error, do not attempt to populate
3960 // the fields with the base_expr. This could cause us to hit errors later
3961 // when certain fields are assumed to exist that in fact do not.
3962 if !error_happened {
3963 self.check_expr_has_type_or_error(base_expr, adt_ty);
3965 ty::Adt(adt, substs) if adt.is_struct() => {
3966 let fru_field_types = adt.non_enum_variant().fields.iter().map(|f| {
3967 self.normalize_associated_types_in(expr.span, &f.ty(self.tcx, substs))
3972 .fru_field_types_mut()
3973 .insert(expr.hir_id, fru_field_types);
3976 span_err!(self.tcx.sess, base_expr.span, E0436,
3977 "functional record update syntax requires a struct");
3982 self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
3988 /// If an expression has any sub-expressions that result in a type error,
3989 /// inspecting that expression's type with `ty.references_error()` will return
3990 /// true. Likewise, if an expression is known to diverge, inspecting its
3991 /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
3992 /// strict, _|_ can appear in the type of an expression that does not,
3993 /// itself, diverge: for example, fn() -> _|_.)
3994 /// Note that inspecting a type's structure *directly* may expose the fact
3995 /// that there are actually multiple representations for `Error`, so avoid
3996 /// that when err needs to be handled differently.
3997 fn check_expr_with_expectation_and_needs(&self,
3998 expr: &'gcx hir::Expr,
3999 expected: Expectation<'tcx>,
4000 needs: Needs) -> Ty<'tcx> {
4001 debug!(">> type-checking: expr={:?} expected={:?}",
4004 // Warn for expressions after diverging siblings.
4005 self.warn_if_unreachable(expr.id, expr.span, "expression");
4007 // Hide the outer diverging and has_errors flags.
4008 let old_diverges = self.diverges.get();
4009 let old_has_errors = self.has_errors.get();
4010 self.diverges.set(Diverges::Maybe);
4011 self.has_errors.set(false);
4013 let ty = self.check_expr_kind(expr, expected, needs);
4015 // Warn for non-block expressions with diverging children.
4017 ExprKind::Block(..) |
4018 ExprKind::Loop(..) | ExprKind::While(..) |
4019 ExprKind::If(..) | ExprKind::Match(..) => {}
4021 _ => self.warn_if_unreachable(expr.id, expr.span, "expression")
4024 // Any expression that produces a value of type `!` must have diverged
4026 self.diverges.set(self.diverges.get() | Diverges::Always);
4029 // Record the type, which applies it effects.
4030 // We need to do this after the warning above, so that
4031 // we don't warn for the diverging expression itself.
4032 self.write_ty(expr.hir_id, ty);
4034 // Combine the diverging and has_error flags.
4035 self.diverges.set(self.diverges.get() | old_diverges);
4036 self.has_errors.set(self.has_errors.get() | old_has_errors);
4038 debug!("type of {} is...", self.tcx.hir().node_to_string(expr.id));
4039 debug!("... {:?}, expected is {:?}", ty, expected);
4046 expr: &'gcx hir::Expr,
4047 expected: Expectation<'tcx>,
4051 "check_expr_kind(expr={:?}, expected={:?}, needs={:?})",
4060 ExprKind::Box(ref subexpr) => {
4061 let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
4063 ty::Adt(def, _) if def.is_box()
4064 => Expectation::rvalue_hint(self, ty.boxed_ty()),
4068 let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
4069 tcx.mk_box(referent_ty)
4072 ExprKind::Lit(ref lit) => {
4073 self.check_lit(&lit, expected)
4075 ExprKind::Binary(op, ref lhs, ref rhs) => {
4076 self.check_binop(expr, op, lhs, rhs)
4078 ExprKind::AssignOp(op, ref lhs, ref rhs) => {
4079 self.check_binop_assign(expr, op, lhs, rhs)
4081 ExprKind::Unary(unop, ref oprnd) => {
4082 let expected_inner = match unop {
4083 hir::UnNot | hir::UnNeg => {
4090 let needs = match unop {
4091 hir::UnDeref => needs,
4094 let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd,
4098 if !oprnd_t.references_error() {
4099 oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
4102 if let Some(mt) = oprnd_t.builtin_deref(true) {
4104 } else if let Some(ok) = self.try_overloaded_deref(
4105 expr.span, oprnd_t, needs) {
4106 let method = self.register_infer_ok_obligations(ok);
4107 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].sty {
4108 let mutbl = match mutbl {
4109 hir::MutImmutable => AutoBorrowMutability::Immutable,
4110 hir::MutMutable => AutoBorrowMutability::Mutable {
4111 // (It shouldn't actually matter for unary ops whether
4112 // we enable two-phase borrows or not, since a unary
4113 // op has no additional operands.)
4114 allow_two_phase_borrow: AllowTwoPhase::No,
4117 self.apply_adjustments(oprnd, vec![Adjustment {
4118 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
4119 target: method.sig.inputs()[0]
4122 oprnd_t = self.make_overloaded_place_return_type(method).ty;
4123 self.write_method_call(expr.hir_id, method);
4125 type_error_struct!(tcx.sess, expr.span, oprnd_t, E0614,
4126 "type `{}` cannot be dereferenced",
4128 oprnd_t = tcx.types.err;
4132 let result = self.check_user_unop(expr, oprnd_t, unop);
4133 // If it's builtin, we can reuse the type, this helps inference.
4134 if !(oprnd_t.is_integral() || oprnd_t.sty == ty::Bool) {
4139 let result = self.check_user_unop(expr, oprnd_t, unop);
4140 // If it's builtin, we can reuse the type, this helps inference.
4141 if !(oprnd_t.is_integral() || oprnd_t.is_fp()) {
4149 ExprKind::AddrOf(mutbl, ref oprnd) => {
4150 let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
4152 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
4153 if oprnd.is_place_expr() {
4154 // Places may legitimately have unsized types.
4155 // For example, dereferences of a fat pointer and
4156 // the last field of a struct can be unsized.
4159 Expectation::rvalue_hint(self, ty)
4165 let needs = Needs::maybe_mut_place(mutbl);
4166 let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs);
4168 let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
4169 if tm.ty.references_error() {
4172 // Note: at this point, we cannot say what the best lifetime
4173 // is to use for resulting pointer. We want to use the
4174 // shortest lifetime possible so as to avoid spurious borrowck
4175 // errors. Moreover, the longest lifetime will depend on the
4176 // precise details of the value whose address is being taken
4177 // (and how long it is valid), which we don't know yet until type
4178 // inference is complete.
4180 // Therefore, here we simply generate a region variable. The
4181 // region inferencer will then select the ultimate value.
4182 // Finally, borrowck is charged with guaranteeing that the
4183 // value whose address was taken can actually be made to live
4184 // as long as it needs to live.
4185 let region = self.next_region_var(infer::AddrOfRegion(expr.span));
4186 tcx.mk_ref(region, tm)
4189 ExprKind::Path(ref qpath) => {
4190 let (def, opt_ty, segs) = self.resolve_ty_and_def_ufcs(qpath, expr.id, expr.span);
4191 let ty = match def {
4193 self.set_tainted_by_errors();
4196 Def::VariantCtor(_, CtorKind::Fictive) => {
4197 report_unexpected_variant_def(tcx, &def, expr.span, qpath);
4200 _ => self.instantiate_value_path(segs, opt_ty, def, expr.span, id).0,
4203 if let ty::FnDef(..) = ty.sty {
4204 let fn_sig = ty.fn_sig(tcx);
4205 if !tcx.features().unsized_locals {
4206 // We want to remove some Sized bounds from std functions,
4207 // but don't want to expose the removal to stable Rust.
4208 // i.e., we don't want to allow
4214 // to work in stable even if the Sized bound on `drop` is relaxed.
4215 for i in 0..fn_sig.inputs().skip_binder().len() {
4216 // We just want to check sizedness, so instead of introducing
4217 // placeholder lifetimes with probing, we just replace higher lifetimes
4219 let input = self.replace_bound_vars_with_fresh_vars(
4221 infer::LateBoundRegionConversionTime::FnCall,
4222 &fn_sig.input(i)).0;
4223 self.require_type_is_sized_deferred(input, expr.span,
4224 traits::SizedArgumentType);
4227 // Here we want to prevent struct constructors from returning unsized types.
4228 // There were two cases this happened: fn pointer coercion in stable
4229 // and usual function call in presense of unsized_locals.
4230 // Also, as we just want to check sizedness, instead of introducing
4231 // placeholder lifetimes with probing, we just replace higher lifetimes
4233 let output = self.replace_bound_vars_with_fresh_vars(
4235 infer::LateBoundRegionConversionTime::FnCall,
4236 &fn_sig.output()).0;
4237 self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
4240 // We always require that the type provided as the value for
4241 // a type parameter outlives the moment of instantiation.
4242 let substs = self.tables.borrow().node_substs(expr.hir_id);
4243 self.add_wf_bounds(substs, expr);
4247 ExprKind::InlineAsm(_, ref outputs, ref inputs) => {
4248 for expr in outputs.iter().chain(inputs.iter()) {
4249 self.check_expr(expr);
4253 ExprKind::Break(destination, ref expr_opt) => {
4254 if let Ok(target_id) = destination.target_id {
4256 if let Some(ref e) = *expr_opt {
4257 // If this is a break with a value, we need to type-check
4258 // the expression. Get an expected type from the loop context.
4259 let opt_coerce_to = {
4260 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4261 enclosing_breakables.find_breakable(target_id)
4264 .map(|coerce| coerce.expected_ty())
4267 // If the loop context is not a `loop { }`, then break with
4268 // a value is illegal, and `opt_coerce_to` will be `None`.
4269 // Just set expectation to error in that case.
4270 let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
4272 // Recurse without `enclosing_breakables` borrowed.
4273 e_ty = self.check_expr_with_hint(e, coerce_to);
4274 cause = self.misc(e.span);
4276 // Otherwise, this is a break *without* a value. That's
4277 // always legal, and is equivalent to `break ()`.
4278 e_ty = tcx.mk_unit();
4279 cause = self.misc(expr.span);
4282 // Now that we have type-checked `expr_opt`, borrow
4283 // the `enclosing_loops` field and let's coerce the
4284 // type of `expr_opt` into what is expected.
4285 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4286 let ctxt = enclosing_breakables.find_breakable(target_id);
4287 if let Some(ref mut coerce) = ctxt.coerce {
4288 if let Some(ref e) = *expr_opt {
4289 coerce.coerce(self, &cause, e, e_ty);
4291 assert!(e_ty.is_unit());
4292 coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
4295 // If `ctxt.coerce` is `None`, we can just ignore
4296 // the type of the expresison. This is because
4297 // either this was a break *without* a value, in
4298 // which case it is always a legal type (`()`), or
4299 // else an error would have been flagged by the
4300 // `loops` pass for using break with an expression
4301 // where you are not supposed to.
4302 assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
4305 ctxt.may_break = true;
4307 // the type of a `break` is always `!`, since it diverges
4310 // Otherwise, we failed to find the enclosing loop;
4311 // this can only happen if the `break` was not
4312 // inside a loop at all, which is caught by the
4313 // loop-checking pass.
4314 if self.tcx.sess.err_count() == 0 {
4315 self.tcx.sess.delay_span_bug(expr.span,
4316 "break was outside loop, but no error was emitted");
4319 // We still need to assign a type to the inner expression to
4320 // prevent the ICE in #43162.
4321 if let Some(ref e) = *expr_opt {
4322 self.check_expr_with_hint(e, tcx.types.err);
4324 // ... except when we try to 'break rust;'.
4325 // ICE this expression in particular (see #43162).
4326 if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.node {
4327 if path.segments.len() == 1 && path.segments[0].ident.name == "rust" {
4328 fatally_break_rust(self.tcx.sess);
4332 // There was an error; make type-check fail.
4337 ExprKind::Continue(destination) => {
4338 if destination.target_id.is_ok() {
4341 // There was an error; make type-check fail.
4345 ExprKind::Ret(ref expr_opt) => {
4346 if self.ret_coercion.is_none() {
4347 struct_span_err!(self.tcx.sess, expr.span, E0572,
4348 "return statement outside of function body").emit();
4349 } else if let Some(ref e) = *expr_opt {
4350 *self.ret_coercion_span.borrow_mut() = Some(e.span);
4351 self.check_return_expr(e);
4353 let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
4354 *self.ret_coercion_span.borrow_mut() = Some(expr.span);
4355 let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
4356 if let Some((fn_decl, _)) = self.get_fn_decl(expr.id) {
4357 coercion.coerce_forced_unit(
4362 fn_decl.output.span(),
4364 "expected `{}` because of this return type",
4372 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
4377 ExprKind::Assign(ref lhs, ref rhs) => {
4378 let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
4380 let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
4383 ExpectIfCondition => {
4384 self.tcx.sess.delay_span_bug(lhs.span, "invalid lhs expression in if;\
4385 expected error elsehwere");
4388 // Only check this if not in an `if` condition, as the
4389 // mistyped comparison help is more appropriate.
4390 if !lhs.is_place_expr() {
4391 struct_span_err!(self.tcx.sess, expr.span, E0070,
4392 "invalid left-hand side expression")
4393 .span_label(expr.span, "left-hand of expression not valid")
4399 self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
4401 if lhs_ty.references_error() || rhs_ty.references_error() {
4407 ExprKind::If(ref cond, ref then_expr, ref opt_else_expr) => {
4408 self.check_then_else(&cond, then_expr, opt_else_expr.as_ref().map(|e| &**e),
4409 expr.span, expected)
4411 ExprKind::While(ref cond, ref body, _) => {
4412 let ctxt = BreakableCtxt {
4413 // cannot use break with a value from a while loop
4415 may_break: false, // Will get updated if/when we find a `break`.
4418 let (ctxt, ()) = self.with_breakable_ctxt(expr.id, ctxt, || {
4419 self.check_expr_has_type_or_error(&cond, tcx.types.bool);
4420 let cond_diverging = self.diverges.get();
4421 self.check_block_no_value(&body);
4423 // We may never reach the body so it diverging means nothing.
4424 self.diverges.set(cond_diverging);
4428 // No way to know whether it's diverging because
4429 // of a `break` or an outer `break` or `return`.
4430 self.diverges.set(Diverges::Maybe);
4435 ExprKind::Loop(ref body, _, source) => {
4436 let coerce = match source {
4437 // you can only use break with a value from a normal `loop { }`
4438 hir::LoopSource::Loop => {
4439 let coerce_to = expected.coercion_target_type(self, body.span);
4440 Some(CoerceMany::new(coerce_to))
4443 hir::LoopSource::WhileLet |
4444 hir::LoopSource::ForLoop => {
4449 let ctxt = BreakableCtxt {
4451 may_break: false, // Will get updated if/when we find a `break`.
4454 let (ctxt, ()) = self.with_breakable_ctxt(expr.id, ctxt, || {
4455 self.check_block_no_value(&body);
4459 // No way to know whether it's diverging because
4460 // of a `break` or an outer `break` or `return`.
4461 self.diverges.set(Diverges::Maybe);
4464 // If we permit break with a value, then result type is
4465 // the LUB of the breaks (possibly ! if none); else, it
4466 // is nil. This makes sense because infinite loops
4467 // (which would have type !) are only possible iff we
4468 // permit break with a value [1].
4469 if ctxt.coerce.is_none() && !ctxt.may_break {
4471 self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
4473 ctxt.coerce.map(|c| c.complete(self)).unwrap_or_else(|| self.tcx.mk_unit())
4475 ExprKind::Match(ref discrim, ref arms, match_src) => {
4476 self.check_match(expr, &discrim, arms, expected, match_src)
4478 ExprKind::Closure(capture, ref decl, body_id, _, gen) => {
4479 self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
4481 ExprKind::Block(ref body, _) => {
4482 self.check_block_with_expected(&body, expected)
4484 ExprKind::Call(ref callee, ref args) => {
4485 self.check_call(expr, &callee, args, expected)
4487 ExprKind::MethodCall(ref segment, span, ref args) => {
4488 self.check_method_call(expr, segment, span, args, expected, needs)
4490 ExprKind::Cast(ref e, ref t) => {
4491 // Find the type of `e`. Supply hints based on the type we are casting to,
4493 let t_cast = self.to_ty_saving_user_provided_ty(t);
4494 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
4495 let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
4496 let t_cast = self.resolve_type_vars_if_possible(&t_cast);
4498 // Eagerly check for some obvious errors.
4499 if t_expr.references_error() || t_cast.references_error() {
4502 // Defer other checks until we're done type checking.
4503 let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
4504 match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
4506 deferred_cast_checks.push(cast_check);
4509 Err(ErrorReported) => {
4515 ExprKind::Type(ref e, ref t) => {
4516 let ty = self.to_ty_saving_user_provided_ty(&t);
4517 self.check_expr_eq_type(&e, ty);
4520 ExprKind::Array(ref args) => {
4521 let uty = expected.to_option(self).and_then(|uty| {
4523 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
4528 let element_ty = if !args.is_empty() {
4529 let coerce_to = uty.unwrap_or_else(
4530 || self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span)));
4531 let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
4532 assert_eq!(self.diverges.get(), Diverges::Maybe);
4534 let e_ty = self.check_expr_with_hint(e, coerce_to);
4535 let cause = self.misc(e.span);
4536 coerce.coerce(self, &cause, e, e_ty);
4538 coerce.complete(self)
4540 self.next_ty_var(TypeVariableOrigin::TypeInference(expr.span))
4542 tcx.mk_array(element_ty, args.len() as u64)
4544 ExprKind::Repeat(ref element, ref count) => {
4545 let count_def_id = tcx.hir().local_def_id(count.id);
4546 let param_env = ty::ParamEnv::empty();
4547 let substs = Substs::identity_for_item(tcx.global_tcx(), count_def_id);
4548 let instance = ty::Instance::resolve(
4554 let global_id = GlobalId {
4558 let count = tcx.const_eval(param_env.and(global_id));
4560 let uty = match expected {
4561 ExpectHasType(uty) => {
4563 ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
4570 let (element_ty, t) = match uty {
4572 self.check_expr_coercable_to_type(&element, uty);
4576 let ty = self.next_ty_var(TypeVariableOrigin::MiscVariable(element.span));
4577 let element_ty = self.check_expr_has_type_or_error(&element, ty);
4582 if let Ok(count) = count {
4583 let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1);
4585 // For [foo, ..n] where n > 1, `foo` must have
4587 let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
4588 self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
4592 if element_ty.references_error() {
4594 } else if let Ok(count) = count {
4595 tcx.mk_ty(ty::Array(t, tcx.intern_lazy_const(ty::LazyConst::Evaluated(count))))
4600 ExprKind::Tup(ref elts) => {
4601 let flds = expected.only_has_type(self).and_then(|ty| {
4602 let ty = self.resolve_type_vars_with_obligations(ty);
4604 ty::Tuple(ref flds) => Some(&flds[..]),
4609 let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
4610 let t = match flds {
4611 Some(ref fs) if i < fs.len() => {
4613 self.check_expr_coercable_to_type(&e, ety);
4617 self.check_expr_with_expectation(&e, NoExpectation)
4622 let tuple = tcx.mk_tup(elt_ts_iter);
4623 if tuple.references_error() {
4626 self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
4630 ExprKind::Struct(ref qpath, ref fields, ref base_expr) => {
4631 self.check_expr_struct(expr, expected, qpath, fields, base_expr)
4633 ExprKind::Field(ref base, field) => {
4634 self.check_field(expr, needs, &base, field)
4636 ExprKind::Index(ref base, ref idx) => {
4637 let base_t = self.check_expr_with_needs(&base, needs);
4638 let idx_t = self.check_expr(&idx);
4640 if base_t.references_error() {
4642 } else if idx_t.references_error() {
4645 let base_t = self.structurally_resolved_type(base.span, base_t);
4646 match self.lookup_indexing(expr, base, base_t, idx_t, needs) {
4647 Some((index_ty, element_ty)) => {
4648 // two-phase not needed because index_ty is never mutable
4649 self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No);
4654 type_error_struct!(tcx.sess, expr.span, base_t, E0608,
4655 "cannot index into a value of type `{}`",
4657 // Try to give some advice about indexing tuples.
4658 if let ty::Tuple(..) = base_t.sty {
4659 let mut needs_note = true;
4660 // If the index is an integer, we can show the actual
4661 // fixed expression:
4662 if let ExprKind::Lit(ref lit) = idx.node {
4663 if let ast::LitKind::Int(i,
4664 ast::LitIntType::Unsuffixed) = lit.node {
4665 let snip = tcx.sess.source_map().span_to_snippet(base.span);
4666 if let Ok(snip) = snip {
4667 err.span_suggestion_with_applicability(
4669 "to access tuple elements, use",
4670 format!("{}.{}", snip, i),
4671 Applicability::MachineApplicable);
4677 err.help("to access tuple elements, use tuple indexing \
4678 syntax (e.g., `tuple.0`)");
4687 ExprKind::Yield(ref value) => {
4688 match self.yield_ty {
4690 self.check_expr_coercable_to_type(&value, ty);
4693 struct_span_err!(self.tcx.sess, expr.span, E0627,
4694 "yield statement outside of generator literal").emit();
4699 hir::ExprKind::Err => {
4705 // Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
4706 // The newly resolved definition is written into `type_dependent_defs`.
4707 fn finish_resolving_struct_path(&self,
4710 node_id: ast::NodeId)
4714 QPath::Resolved(ref maybe_qself, ref path) => {
4715 let self_ty = maybe_qself.as_ref().map(|qself| self.to_ty(qself));
4716 let ty = AstConv::def_to_ty(self, self_ty, path, true);
4719 QPath::TypeRelative(ref qself, ref segment) => {
4720 let ty = self.to_ty(qself);
4722 let def = if let hir::TyKind::Path(QPath::Resolved(_, ref path)) = qself.node {
4727 let (ty, def) = AstConv::associated_path_def_to_ty(self, node_id, path_span,
4730 // Write back the new resolution.
4731 let hir_id = self.tcx.hir().node_to_hir_id(node_id);
4732 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, def);
4739 // Resolve associated value path into a base type and associated constant or method definition.
4740 // The newly resolved definition is written into `type_dependent_defs`.
4741 pub fn resolve_ty_and_def_ufcs<'b>(&self,
4743 node_id: ast::NodeId,
4745 -> (Def, Option<Ty<'tcx>>, &'b [hir::PathSegment])
4747 debug!("resolve_ty_and_def_ufcs: qpath={:?} node_id={:?} span={:?}", qpath, node_id, span);
4748 let (ty, qself, item_segment) = match *qpath {
4749 QPath::Resolved(ref opt_qself, ref path) => {
4751 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
4752 &path.segments[..]);
4754 QPath::TypeRelative(ref qself, ref segment) => {
4755 (self.to_ty(qself), qself, segment)
4758 let hir_id = self.tcx.hir().node_to_hir_id(node_id);
4759 if let Some(cached_def) = self.tables.borrow().type_dependent_defs().get(hir_id) {
4760 // Return directly on cache hit. This is useful to avoid doubly reporting
4761 // errors with default match binding modes. See #44614.
4762 return (*cached_def, Some(ty), slice::from_ref(&**item_segment))
4764 let item_name = item_segment.ident;
4765 let def = match self.resolve_ufcs(span, item_name, ty, node_id) {
4768 let def = match error {
4769 method::MethodError::PrivateMatch(def, _) => def,
4772 if item_name.name != keywords::Invalid.name() {
4773 self.report_method_error(span,
4776 SelfSource::QPath(qself),
4784 // Write back the new resolution.
4785 self.tables.borrow_mut().type_dependent_defs_mut().insert(hir_id, def);
4786 (def, Some(ty), slice::from_ref(&**item_segment))
4789 pub fn check_decl_initializer(&self,
4790 local: &'gcx hir::Local,
4791 init: &'gcx hir::Expr) -> Ty<'tcx>
4793 // FIXME(tschottdorf): `contains_explicit_ref_binding()` must be removed
4794 // for #42640 (default match binding modes).
4797 let ref_bindings = local.pat.contains_explicit_ref_binding();
4799 let local_ty = self.local_ty(init.span, local.id).revealed_ty;
4800 if let Some(m) = ref_bindings {
4801 // Somewhat subtle: if we have a `ref` binding in the pattern,
4802 // we want to avoid introducing coercions for the RHS. This is
4803 // both because it helps preserve sanity and, in the case of
4804 // ref mut, for soundness (issue #23116). In particular, in
4805 // the latter case, we need to be clear that the type of the
4806 // referent for the reference that results is *equal to* the
4807 // type of the place it is referencing, and not some
4808 // supertype thereof.
4809 let init_ty = self.check_expr_with_needs(init, Needs::maybe_mut_place(m));
4810 self.demand_eqtype(init.span, local_ty, init_ty);
4813 self.check_expr_coercable_to_type(init, local_ty)
4817 pub fn check_decl_local(&self, local: &'gcx hir::Local) {
4818 let t = self.local_ty(local.span, local.id).decl_ty;
4819 self.write_ty(local.hir_id, t);
4821 if let Some(ref init) = local.init {
4822 let init_ty = self.check_decl_initializer(local, &init);
4823 if init_ty.references_error() {
4824 self.write_ty(local.hir_id, init_ty);
4828 self.check_pat_walk(
4831 ty::BindingMode::BindByValue(hir::Mutability::MutImmutable),
4834 let pat_ty = self.node_ty(local.pat.hir_id);
4835 if pat_ty.references_error() {
4836 self.write_ty(local.hir_id, pat_ty);
4840 pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
4841 // Don't do all the complex logic below for `DeclItem`.
4843 hir::StmtKind::Decl(ref decl, _) => {
4844 if let hir::DeclKind::Item(_) = decl.node {
4848 hir::StmtKind::Expr(..) | hir::StmtKind::Semi(..) => {}
4851 self.warn_if_unreachable(stmt.node.id(), stmt.span, "statement");
4853 // Hide the outer diverging and `has_errors` flags.
4854 let old_diverges = self.diverges.get();
4855 let old_has_errors = self.has_errors.get();
4856 self.diverges.set(Diverges::Maybe);
4857 self.has_errors.set(false);
4860 hir::StmtKind::Decl(ref decl, _) => {
4862 hir::DeclKind::Local(ref l) => {
4863 self.check_decl_local(&l);
4866 hir::DeclKind::Item(_) => ()
4869 hir::StmtKind::Expr(ref expr, _) => {
4870 // Check with expected type of `()`.
4871 self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit());
4873 hir::StmtKind::Semi(ref expr, _) => {
4874 self.check_expr(&expr);
4878 // Combine the diverging and `has_error` flags.
4879 self.diverges.set(self.diverges.get() | old_diverges);
4880 self.has_errors.set(self.has_errors.get() | old_has_errors);
4883 pub fn check_block_no_value(&self, blk: &'gcx hir::Block) {
4884 let unit = self.tcx.mk_unit();
4885 let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
4887 // if the block produces a `!` value, that can always be
4888 // (effectively) coerced to unit.
4890 self.demand_suptype(blk.span, unit, ty);
4894 fn check_block_with_expected(&self,
4895 blk: &'gcx hir::Block,
4896 expected: Expectation<'tcx>) -> Ty<'tcx> {
4898 let mut fcx_ps = self.ps.borrow_mut();
4899 let unsafety_state = fcx_ps.recurse(blk);
4900 replace(&mut *fcx_ps, unsafety_state)
4903 // In some cases, blocks have just one exit, but other blocks
4904 // can be targeted by multiple breaks. This can happen both
4905 // with labeled blocks as well as when we desugar
4906 // a `try { ... }` expression.
4910 // 'a: { if true { break 'a Err(()); } Ok(()) }
4912 // Here we would wind up with two coercions, one from
4913 // `Err(())` and the other from the tail expression
4914 // `Ok(())`. If the tail expression is omitted, that's a
4915 // "forced unit" -- unless the block diverges, in which
4916 // case we can ignore the tail expression (e.g., `'a: {
4917 // break 'a 22; }` would not force the type of the block
4919 let tail_expr = blk.expr.as_ref();
4920 let coerce_to_ty = expected.coercion_target_type(self, blk.span);
4921 let coerce = if blk.targeted_by_break {
4922 CoerceMany::new(coerce_to_ty)
4924 let tail_expr: &[P<hir::Expr>] = match tail_expr {
4925 Some(e) => slice::from_ref(e),
4928 CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
4931 let prev_diverges = self.diverges.get();
4932 let ctxt = BreakableCtxt {
4933 coerce: Some(coerce),
4937 let (ctxt, ()) = self.with_breakable_ctxt(blk.id, ctxt, || {
4938 for s in &blk.stmts {
4942 // check the tail expression **without** holding the
4943 // `enclosing_breakables` lock below.
4944 let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
4946 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
4947 let ctxt = enclosing_breakables.find_breakable(blk.id);
4948 let coerce = ctxt.coerce.as_mut().unwrap();
4949 if let Some(tail_expr_ty) = tail_expr_ty {
4950 let tail_expr = tail_expr.unwrap();
4951 let cause = self.cause(tail_expr.span,
4952 ObligationCauseCode::BlockTailExpression(blk.id));
4958 // Subtle: if there is no explicit tail expression,
4959 // that is typically equivalent to a tail expression
4960 // of `()` -- except if the block diverges. In that
4961 // case, there is no value supplied from the tail
4962 // expression (assuming there are no other breaks,
4963 // this implies that the type of the block will be
4966 // #41425 -- label the implicit `()` as being the
4967 // "found type" here, rather than the "expected type".
4968 if !self.diverges.get().always() {
4969 // #50009 -- Do not point at the entire fn block span, point at the return type
4970 // span, as it is the cause of the requirement, and
4971 // `consider_hint_about_removing_semicolon` will point at the last expression
4972 // if it were a relevant part of the error. This improves usability in editors
4973 // that highlight errors inline.
4974 let mut sp = blk.span;
4975 let mut fn_span = None;
4976 if let Some((decl, ident)) = self.get_parent_fn_decl(blk.id) {
4977 let ret_sp = decl.output.span();
4978 if let Some(block_sp) = self.parent_item_span(blk.id) {
4979 // HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
4980 // output would otherwise be incorrect and even misleading. Make sure
4981 // the span we're aiming at correspond to a `fn` body.
4982 if block_sp == blk.span {
4984 fn_span = Some(ident.span);
4988 coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
4989 if let Some(expected_ty) = expected.only_has_type(self) {
4990 self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
4992 if let Some(fn_span) = fn_span {
4993 err.span_label(fn_span, "this function's body doesn't return");
5001 // If we can break from the block, then the block's exit is always reachable
5002 // (... as long as the entry is reachable) - regardless of the tail of the block.
5003 self.diverges.set(prev_diverges);
5006 let mut ty = ctxt.coerce.unwrap().complete(self);
5008 if self.has_errors.get() || ty.references_error() {
5009 ty = self.tcx.types.err
5012 self.write_ty(blk.hir_id, ty);
5014 *self.ps.borrow_mut() = prev;
5018 fn parent_item_span(&self, id: ast::NodeId) -> Option<Span> {
5019 let node = self.tcx.hir().get(self.tcx.hir().get_parent(id));
5021 Node::Item(&hir::Item {
5022 node: hir::ItemKind::Fn(_, _, _, body_id), ..
5024 Node::ImplItem(&hir::ImplItem {
5025 node: hir::ImplItemKind::Method(_, body_id), ..
5027 let body = self.tcx.hir().body(body_id);
5028 if let ExprKind::Block(block, _) = &body.value.node {
5029 return Some(block.span);
5037 /// Given a function block's `NodeId`, return its `FnDecl` if it exists, or `None` otherwise.
5038 fn get_parent_fn_decl(&self, blk_id: ast::NodeId) -> Option<(hir::FnDecl, ast::Ident)> {
5039 let parent = self.tcx.hir().get(self.tcx.hir().get_parent(blk_id));
5040 self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
5043 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
5044 fn get_node_fn_decl(&self, node: Node) -> Option<(hir::FnDecl, ast::Ident, bool)> {
5046 Node::Item(&hir::Item {
5047 ident, node: hir::ItemKind::Fn(ref decl, ..), ..
5048 }) => decl.clone().and_then(|decl| {
5049 // This is less than ideal, it will not suggest a return type span on any
5050 // method called `main`, regardless of whether it is actually the entry point,
5051 // but it will still present it as the reason for the expected type.
5052 Some((decl, ident, ident.name != Symbol::intern("main")))
5054 Node::TraitItem(&hir::TraitItem {
5055 ident, node: hir::TraitItemKind::Method(hir::MethodSig {
5058 }) => decl.clone().and_then(|decl| Some((decl, ident, true))),
5059 Node::ImplItem(&hir::ImplItem {
5060 ident, node: hir::ImplItemKind::Method(hir::MethodSig {
5063 }) => decl.clone().and_then(|decl| Some((decl, ident, false))),
5068 /// Given a `NodeId`, return the `FnDecl` of the method it is enclosed by and whether a
5069 /// suggestion can be made, `None` otherwise.
5070 pub fn get_fn_decl(&self, blk_id: ast::NodeId) -> Option<(hir::FnDecl, bool)> {
5071 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
5072 // `while` before reaching it, as block tail returns are not available in them.
5073 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
5074 let parent = self.tcx.hir().get(blk_id);
5075 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
5079 /// On implicit return expressions with mismatched types, provide the following suggestions:
5081 /// - Point out the method's return type as the reason for the expected type
5082 /// - Possible missing semicolon
5083 /// - Possible missing return type if the return type is the default, and not `fn main()`
5084 pub fn suggest_mismatched_types_on_tail(
5086 err: &mut DiagnosticBuilder<'tcx>,
5087 expression: &'gcx hir::Expr,
5091 blk_id: ast::NodeId,
5093 self.suggest_missing_semicolon(err, expression, expected, cause_span);
5094 if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
5095 self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest);
5097 self.suggest_ref_or_into(err, expression, expected, found);
5100 pub fn suggest_ref_or_into(
5102 err: &mut DiagnosticBuilder<'tcx>,
5107 if let Some((sp, msg, suggestion)) = self.check_ref(expr, found, expected) {
5108 err.span_suggestion_with_applicability(
5112 Applicability::MachineApplicable,
5114 } else if !self.check_for_cast(err, expr, found, expected) {
5115 let methods = self.get_conversion_methods(expr.span, expected, found);
5116 if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) {
5117 let mut suggestions = iter::repeat(&expr_text).zip(methods.iter())
5118 .filter_map(|(receiver, method)| {
5119 let method_call = format!(".{}()", method.ident);
5120 if receiver.ends_with(&method_call) {
5121 None // do not suggest code that is already there (#53348)
5123 let method_call_list = [".to_vec()", ".to_string()"];
5124 if receiver.ends_with(".clone()")
5125 && method_call_list.contains(&method_call.as_str()) {
5126 let max_len = receiver.rfind(".").unwrap();
5127 Some(format!("{}{}", &receiver[..max_len], method_call))
5130 Some(format!("{}{}", receiver, method_call))
5134 if suggestions.peek().is_some() {
5135 err.span_suggestions_with_applicability(
5137 "try using a conversion method",
5139 Applicability::MaybeIncorrect,
5146 /// A common error is to forget to add a semicolon at the end of a block:
5150 /// bar_that_returns_u32()
5154 /// This routine checks if the return expression in a block would make sense on its own as a
5155 /// statement and the return type has been left as default or has been specified as `()`. If so,
5156 /// it suggests adding a semicolon.
5157 fn suggest_missing_semicolon(&self,
5158 err: &mut DiagnosticBuilder<'tcx>,
5159 expression: &'gcx hir::Expr,
5162 if expected.is_unit() {
5163 // `BlockTailExpression` only relevant if the tail expr would be
5164 // useful on its own.
5165 match expression.node {
5166 ExprKind::Call(..) |
5167 ExprKind::MethodCall(..) |
5169 ExprKind::While(..) |
5170 ExprKind::Loop(..) |
5171 ExprKind::Match(..) |
5172 ExprKind::Block(..) => {
5173 let sp = self.tcx.sess.source_map().next_point(cause_span);
5174 err.span_suggestion_with_applicability(
5176 "try adding a semicolon",
5178 Applicability::MachineApplicable);
5185 /// A possible error is to forget to add a return type that is needed:
5189 /// bar_that_returns_u32()
5193 /// This routine checks if the return type is left as default, the method is not part of an
5194 /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
5196 fn suggest_missing_return_type(&self,
5197 err: &mut DiagnosticBuilder<'tcx>,
5198 fn_decl: &hir::FnDecl,
5201 can_suggest: bool) {
5202 // Only suggest changing the return type for methods that
5203 // haven't set a return type at all (and aren't `fn main()` or an impl).
5204 match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
5205 (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
5206 err.span_suggestion_with_applicability(
5208 "try adding a return type",
5209 format!("-> {} ", self.resolve_type_vars_with_obligations(found)),
5210 Applicability::MachineApplicable);
5212 (&hir::FunctionRetTy::DefaultReturn(span), false, true, true) => {
5213 err.span_label(span, "possibly return type missing here?");
5215 (&hir::FunctionRetTy::DefaultReturn(span), _, false, true) => {
5216 // `fn main()` must return `()`, do not suggest changing return type
5217 err.span_label(span, "expected `()` because of default return type");
5219 // expectation was caused by something else, not the default return
5220 (&hir::FunctionRetTy::DefaultReturn(_), _, _, false) => {}
5221 (&hir::FunctionRetTy::Return(ref ty), _, _, _) => {
5222 // Only point to return type if the expected type is the return type, as if they
5223 // are not, the expectation must have been caused by something else.
5224 debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.node);
5226 let ty = AstConv::ast_ty_to_ty(self, ty);
5227 debug!("suggest_missing_return_type: return type sty {:?}", ty.sty);
5228 debug!("suggest_missing_return_type: expected type sty {:?}", ty.sty);
5229 if ty.sty == expected.sty {
5230 err.span_label(sp, format!("expected `{}` because of return type",
5237 /// A common error is to add an extra semicolon:
5240 /// fn foo() -> usize {
5245 /// This routine checks if the final statement in a block is an
5246 /// expression with an explicit semicolon whose type is compatible
5247 /// with `expected_ty`. If so, it suggests removing the semicolon.
5248 fn consider_hint_about_removing_semicolon(
5250 blk: &'gcx hir::Block,
5251 expected_ty: Ty<'tcx>,
5252 err: &mut DiagnosticBuilder,
5254 if let Some(span_semi) = self.could_remove_semicolon(blk, expected_ty) {
5255 err.span_suggestion_with_applicability(
5257 "consider removing this semicolon",
5259 Applicability::MachineApplicable,
5264 fn could_remove_semicolon(
5266 blk: &'gcx hir::Block,
5267 expected_ty: Ty<'tcx>,
5269 // Be helpful when the user wrote `{... expr;}` and
5270 // taking the `;` off is enough to fix the error.
5271 let last_stmt = match blk.stmts.last() {
5273 None => return None,
5275 let last_expr = match last_stmt.node {
5276 hir::StmtKind::Semi(ref e, _) => e,
5279 let last_expr_ty = self.node_ty(last_expr.hir_id);
5280 if self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err() {
5283 let original_span = original_sp(last_stmt.span, blk.span);
5284 Some(original_span.with_lo(original_span.hi() - BytePos(1)))
5287 // Instantiates the given path, which must refer to an item with the given
5288 // number of type parameters and type.
5289 pub fn instantiate_value_path(&self,
5290 segments: &[hir::PathSegment],
5291 self_ty: Option<Ty<'tcx>>,
5294 node_id: ast::NodeId)
5295 -> (Ty<'tcx>, Def) {
5297 "instantiate_value_path(segments={:?}, self_ty={:?}, def={:?}, node_id={})",
5306 let path_segs = AstConv::def_ids_for_path_segments(self, segments, self_ty, def);
5308 let mut user_self_ty = None;
5309 let mut is_alias_variant_ctor = false;
5311 Def::VariantCtor(_, _) => {
5312 if let Some(self_ty) = self_ty {
5313 let adt_def = self_ty.ty_adt_def().unwrap();
5314 user_self_ty = Some(UserSelfTy {
5315 impl_def_id: adt_def.did,
5318 is_alias_variant_ctor = true;
5321 Def::Method(def_id) |
5322 Def::AssociatedConst(def_id) => {
5323 let container = tcx.associated_item(def_id).container;
5324 debug!("instantiate_value_path: def={:?} container={:?}", def, container);
5326 ty::TraitContainer(trait_did) => {
5327 callee::check_legal_trait_for_method_call(tcx, span, trait_did)
5329 ty::ImplContainer(impl_def_id) => {
5330 if segments.len() == 1 {
5331 // `<T>::assoc` will end up here, and so
5332 // can `T::assoc`. It this came from an
5333 // inherent impl, we need to record the
5334 // `T` for posterity (see `UserSelfTy` for
5336 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
5337 user_self_ty = Some(UserSelfTy {
5348 // Now that we have categorized what space the parameters for each
5349 // segment belong to, let's sort out the parameters that the user
5350 // provided (if any) into their appropriate spaces. We'll also report
5351 // errors if type parameters are provided in an inappropriate place.
5353 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
5354 let generics_has_err = AstConv::prohibit_generics(
5355 self, segments.iter().enumerate().filter_map(|(index, seg)| {
5356 if !generic_segs.contains(&index) || is_alias_variant_ctor {
5362 if generics_has_err {
5363 // Don't try to infer type parameters when prohibited generic arguments were given.
5364 user_self_ty = None;
5368 Def::Local(nid) | Def::Upvar(nid, ..) => {
5369 let ty = self.local_ty(span, nid).decl_ty;
5370 let ty = self.normalize_associated_types_in(span, &ty);
5371 self.write_ty(tcx.hir().node_to_hir_id(node_id), ty);
5377 // Now we have to compare the types that the user *actually*
5378 // provided against the types that were *expected*. If the user
5379 // did not provide any types, then we want to substitute inference
5380 // variables. If the user provided some types, we may still need
5381 // to add defaults. If the user provided *too many* types, that's
5384 let mut infer_args_for_err = FxHashSet::default();
5385 for &PathSeg(def_id, index) in &path_segs {
5386 let seg = &segments[index];
5387 let generics = tcx.generics_of(def_id);
5388 // Argument-position `impl Trait` is treated as a normal generic
5389 // parameter internally, but we don't allow users to specify the
5390 // parameter's value explicitly, so we have to do some error-
5392 let suppress_errors = AstConv::check_generic_arg_count_for_call(
5397 false, // `is_method_call`
5399 if suppress_errors {
5400 infer_args_for_err.insert(index);
5401 self.set_tainted_by_errors(); // See issue #53251.
5405 let has_self = path_segs.last().map(|PathSeg(def_id, _)| {
5406 tcx.generics_of(*def_id).has_self
5407 }).unwrap_or(false);
5409 let mut new_def = def;
5410 let (def_id, ty) = match def {
5411 Def::SelfCtor(impl_def_id) => {
5412 let ty = self.impl_self_ty(span, impl_def_id).ty;
5413 let adt_def = ty.ty_adt_def();
5416 Some(adt_def) if adt_def.has_ctor() => {
5417 let variant = adt_def.non_enum_variant();
5418 new_def = Def::StructCtor(variant.did, variant.ctor_kind);
5419 (variant.did, tcx.type_of(variant.did))
5422 let mut err = tcx.sess.struct_span_err(span,
5423 "the `Self` constructor can only be used with tuple or unit structs");
5424 if let Some(adt_def) = adt_def {
5425 match adt_def.adt_kind() {
5427 err.help("did you mean to use one of the enum's variants?");
5431 err.span_suggestion_with_applicability(
5433 "use curly brackets",
5434 String::from("Self { /* fields */ }"),
5435 Applicability::HasPlaceholders,
5442 (impl_def_id, tcx.types.err)
5447 let def_id = def.def_id();
5449 // The things we are substituting into the type should not contain
5450 // escaping late-bound regions, and nor should the base type scheme.
5451 let ty = tcx.type_of(def_id);
5456 let substs = AstConv::create_substs_for_generic_args(
5462 // Provide the generic args, and whether types should be inferred.
5464 if let Some(&PathSeg(_, index)) = path_segs.iter().find(|&PathSeg(did, _)| {
5467 // If we've encountered an `impl Trait`-related error, we're just
5468 // going to infer the arguments for better error messages.
5469 if !infer_args_for_err.contains(&index) {
5470 // Check whether the user has provided generic arguments.
5471 if let Some(ref data) = segments[index].args {
5472 return (Some(data), segments[index].infer_types);
5475 return (None, segments[index].infer_types);
5480 // Provide substitutions for parameters for which (valid) arguments have been provided.
5482 match (¶m.kind, arg) {
5483 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
5484 AstConv::ast_region_to_region(self, lt, Some(param)).into()
5486 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
5487 self.to_ty(ty).into()
5489 _ => unreachable!(),
5492 // Provide substitutions for parameters for which arguments are inferred.
5493 |substs, param, infer_types| {
5495 GenericParamDefKind::Lifetime => {
5496 self.re_infer(span, Some(param)).unwrap().into()
5498 GenericParamDefKind::Type { has_default, .. } => {
5499 if !infer_types && has_default {
5500 // If we have a default, then we it doesn't matter that we're not
5501 // inferring the type arguments: we provide the default where any
5503 let default = tcx.type_of(param.def_id);
5506 default.subst_spanned(tcx, substs.unwrap(), Some(span))
5509 // If no type arguments were provided, we have to infer them.
5510 // This case also occurs as a result of some malformed input, e.g.
5511 // a lifetime argument being given instead of a type parameter.
5512 // Using inference instead of `Error` gives better error messages.
5513 self.var_for_def(span, param)
5519 assert!(!substs.has_escaping_bound_vars());
5520 assert!(!ty.has_escaping_bound_vars());
5522 // First, store the "user substs" for later.
5523 let hir_id = tcx.hir().node_to_hir_id(node_id);
5524 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
5526 // Add all the obligations that are required, substituting and
5527 // normalized appropriately.
5528 let bounds = self.instantiate_bounds(span, def_id, &substs);
5529 self.add_obligations_for_parameters(
5530 traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
5533 // Substitute the values for the type parameters into the type of
5534 // the referenced item.
5535 let ty_substituted = self.instantiate_type_scheme(span, &substs, &ty);
5537 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
5538 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
5539 // is inherent, there is no `Self` parameter; instead, the impl needs
5540 // type parameters, which we can infer by unifying the provided `Self`
5541 // with the substituted impl type.
5542 // This also occurs for an enum variant on a type alias.
5543 let ty = tcx.type_of(impl_def_id);
5545 let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
5546 match self.at(&self.misc(span), self.param_env).sup(impl_ty, self_ty) {
5547 Ok(ok) => self.register_infer_ok_obligations(ok),
5550 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
5557 self.check_rustc_args_require_const(def_id, node_id, span);
5559 debug!("instantiate_value_path: type of {:?} is {:?}",
5562 self.write_substs(hir_id, substs);
5564 (ty_substituted, new_def)
5567 fn check_rustc_args_require_const(&self,
5569 node_id: ast::NodeId,
5571 // We're only interested in functions tagged with
5572 // #[rustc_args_required_const], so ignore anything that's not.
5573 if !self.tcx.has_attr(def_id, "rustc_args_required_const") {
5577 // If our calling expression is indeed the function itself, we're good!
5578 // If not, generate an error that this can only be called directly.
5579 if let Node::Expr(expr) = self.tcx.hir().get(self.tcx.hir().get_parent_node(node_id)) {
5580 if let ExprKind::Call(ref callee, ..) = expr.node {
5581 if callee.id == node_id {
5587 self.tcx.sess.span_err(span, "this function can only be invoked \
5588 directly, not through a function pointer");
5591 // Resolves `typ` by a single level if `typ` is a type variable.
5592 // If no resolution is possible, then an error is reported.
5593 // Numeric inference variables may be left unresolved.
5594 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
5595 let ty = self.resolve_type_vars_with_obligations(ty);
5596 if !ty.is_ty_var() {
5599 if !self.is_tainted_by_errors() {
5600 self.need_type_info_err((**self).body_id, sp, ty)
5601 .note("type must be known at this point")
5604 self.demand_suptype(sp, self.tcx.types.err, ty);
5609 fn with_breakable_ctxt<F: FnOnce() -> R, R>(&self, id: ast::NodeId,
5610 ctxt: BreakableCtxt<'gcx, 'tcx>, f: F)
5611 -> (BreakableCtxt<'gcx, 'tcx>, R) {
5614 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5615 index = enclosing_breakables.stack.len();
5616 enclosing_breakables.by_id.insert(id, index);
5617 enclosing_breakables.stack.push(ctxt);
5621 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
5622 debug_assert!(enclosing_breakables.stack.len() == index + 1);
5623 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
5624 enclosing_breakables.stack.pop().expect("missing breakable context")
5629 /// Instantiate a QueryResponse in a probe context, without a
5630 /// good ObligationCause.
5631 fn probe_instantiate_query_response(
5634 original_values: &OriginalQueryValues<'tcx>,
5635 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
5636 ) -> InferResult<'tcx, Ty<'tcx>>
5638 self.instantiate_query_response_and_region_obligations(
5639 &traits::ObligationCause::misc(span, self.body_id),
5645 /// Returns whether an expression is contained inside the LHS of an assignment expression.
5646 fn expr_in_place(&self, mut expr_id: ast::NodeId) -> bool {
5647 let mut contained_in_place = false;
5649 while let hir::Node::Expr(parent_expr) =
5650 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
5652 match &parent_expr.node {
5653 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
5654 if lhs.id == expr_id {
5655 contained_in_place = true;
5661 expr_id = parent_expr.id;
5668 pub fn check_bounds_are_used<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
5669 generics: &ty::Generics,
5671 let own_counts = generics.own_counts();
5672 debug!("check_bounds_are_used(n_tps={}, ty={:?})", own_counts.types, ty);
5674 if own_counts.types == 0 {
5677 // Make a vector of booleans initially false, set to true when used.
5678 let mut types_used = vec![false; own_counts.types];
5680 for leaf_ty in ty.walk() {
5681 if let ty::Param(ty::ParamTy { idx, .. }) = leaf_ty.sty {
5682 debug!("Found use of ty param num {}", idx);
5683 types_used[idx as usize - own_counts.lifetimes] = true;
5684 } else if let ty::Error = leaf_ty.sty {
5685 // If there is already another error, do not emit
5686 // an error for not using a type Parameter.
5687 assert!(tcx.sess.err_count() > 0);
5692 let types = generics.params.iter().filter(|param| match param.kind {
5693 ty::GenericParamDefKind::Type { .. } => true,
5696 for (&used, param) in types_used.iter().zip(types) {
5698 let id = tcx.hir().as_local_node_id(param.def_id).unwrap();
5699 let span = tcx.hir().span(id);
5700 struct_span_err!(tcx.sess, span, E0091, "type parameter `{}` is unused", param.name)
5701 .span_label(span, "unused type parameter")
5707 fn fatally_break_rust(sess: &Session) {
5708 let handler = sess.diagnostic();
5709 handler.span_bug_no_panic(
5711 "It looks like you're trying to break rust; would you like some ICE?",
5713 handler.note_without_error("the compiler expectedly panicked. this is a feature.");
5714 handler.note_without_error(
5715 "we would appreciate a joke overview: \
5716 https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675"
5718 handler.note_without_error(&format!("rustc {} running on {}",
5719 option_env!("CFG_VERSION").unwrap_or("unknown_version"),
5720 ::session::config::host_triple(),
5724 fn potentially_plural_count(count: usize, word: &str) -> String {
5725 format!("{} {}{}", count, word, if count == 1 { "" } else { "s" })