1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! See the Book for more information.
13 pub use self::LateBoundRegionConversionTime::*;
14 pub use self::RegionVariableOrigin::*;
15 pub use self::SubregionOrigin::*;
16 pub use self::ValuePairs::*;
17 pub use ty::IntVarValue;
18 pub use self::freshen::TypeFreshener;
19 pub use self::region_inference::{GenericKind, VerifyBound};
21 use hir::def_id::DefId;
23 use middle::free_region::FreeRegionMap;
24 use middle::mem_categorization as mc;
25 use middle::mem_categorization::McResult;
26 use middle::lang_items;
27 use mir::tcx::LvalueTy;
28 use ty::subst::{Kind, Subst, Substs};
29 use ty::{TyVid, IntVid, FloatVid};
30 use ty::{self, Ty, TyCtxt};
31 use ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
32 use ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
33 use ty::relate::{Relate, RelateResult, TypeRelation};
34 use traits::{self, ObligationCause, PredicateObligations, Reveal};
35 use rustc_data_structures::unify::{self, UnificationTable};
36 use std::cell::{Cell, RefCell, Ref, RefMut};
40 use errors::DiagnosticBuilder;
41 use syntax_pos::{self, Span, DUMMY_SP};
42 use util::nodemap::{FxHashMap, FxHashSet};
43 use arena::DroplessArena;
45 use self::combine::CombineFields;
46 use self::higher_ranked::HrMatchResult;
47 use self::region_inference::{RegionVarBindings, RegionSnapshot};
48 use self::type_variable::TypeVariableOrigin;
49 use self::unify_key::ToType;
54 pub mod error_reporting;
60 pub mod region_inference;
64 pub mod type_variable;
68 pub struct InferOk<'tcx, T> {
70 pub obligations: PredicateObligations<'tcx>,
72 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
74 pub type Bound<T> = Option<T>;
75 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
76 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
78 /// A version of &ty::TypeckTables which can be `Missing` (not needed),
79 /// `InProgress` (during typeck) or `Interned` (result of typeck).
80 /// Only the `InProgress` version supports `borrow_mut`.
81 #[derive(Copy, Clone)]
82 pub enum InferTables<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
83 Interned(&'a ty::TypeckTables<'gcx>),
84 InProgress(&'a RefCell<ty::TypeckTables<'tcx>>),
88 pub enum InferTablesRef<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
89 Interned(&'a ty::TypeckTables<'gcx>),
90 InProgress(Ref<'a, ty::TypeckTables<'tcx>>)
93 impl<'a, 'gcx, 'tcx> Deref for InferTablesRef<'a, 'gcx, 'tcx> {
94 type Target = ty::TypeckTables<'tcx>;
95 fn deref(&self) -> &Self::Target {
97 InferTablesRef::Interned(tables) => tables,
98 InferTablesRef::InProgress(ref tables) => tables
103 impl<'a, 'gcx, 'tcx> InferTables<'a, 'gcx, 'tcx> {
104 pub fn borrow(self) -> InferTablesRef<'a, 'gcx, 'tcx> {
106 InferTables::Interned(tables) => InferTablesRef::Interned(tables),
107 InferTables::InProgress(tables) => InferTablesRef::InProgress(tables.borrow()),
108 InferTables::Missing => {
109 bug!("InferTables: infcx.tables.borrow() with no tables")
114 pub fn expect_interned(self) -> &'a ty::TypeckTables<'gcx> {
116 InferTables::Interned(tables) => tables,
117 InferTables::InProgress(_) => {
118 bug!("InferTables: infcx.tables.expect_interned() during type-checking");
120 InferTables::Missing => {
121 bug!("InferTables: infcx.tables.expect_interned() with no tables")
126 pub fn borrow_mut(self) -> RefMut<'a, ty::TypeckTables<'tcx>> {
128 InferTables::Interned(_) => {
129 bug!("InferTables: infcx.tables.borrow_mut() outside of type-checking");
131 InferTables::InProgress(tables) => tables.borrow_mut(),
132 InferTables::Missing => {
133 bug!("InferTables: infcx.tables.borrow_mut() with no tables")
139 pub struct InferCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
140 pub tcx: TyCtxt<'a, 'gcx, 'tcx>,
142 pub tables: InferTables<'a, 'gcx, 'tcx>,
144 // Cache for projections. This cache is snapshotted along with the
147 // Public so that `traits::project` can use it.
148 pub projection_cache: RefCell<traits::ProjectionCache<'tcx>>,
150 // We instantiate UnificationTable with bounds<Ty> because the
151 // types that might instantiate a general type variable have an
152 // order, represented by its upper and lower bounds.
153 pub type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
155 // Map from integral variable to the kind of integer it represents
156 int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
158 // Map from floating variable to the kind of float it represents
159 float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
161 // For region variables.
162 region_vars: RegionVarBindings<'a, 'gcx, 'tcx>,
164 pub parameter_environment: ty::ParameterEnvironment<'gcx>,
166 /// Caches the results of trait selection. This cache is used
167 /// for things that have to do with the parameters in scope.
168 pub selection_cache: traits::SelectionCache<'tcx>,
170 /// Caches the results of trait evaluation.
171 pub evaluation_cache: traits::EvaluationCache<'tcx>,
173 // the set of predicates on which errors have been reported, to
174 // avoid reporting the same error twice.
175 pub reported_trait_errors: RefCell<FxHashSet<traits::TraitErrorKey<'tcx>>>,
177 // Sadly, the behavior of projection varies a bit depending on the
178 // stage of compilation. The specifics are given in the
179 // documentation for `Reveal`.
180 projection_mode: Reveal,
182 // When an error occurs, we want to avoid reporting "derived"
183 // errors that are due to this original failure. Normally, we
184 // handle this with the `err_count_on_creation` count, which
185 // basically just tracks how many errors were reported when we
186 // started type-checking a fn and checks to see if any new errors
187 // have been reported since then. Not great, but it works.
189 // However, when errors originated in other passes -- notably
190 // resolve -- this heuristic breaks down. Therefore, we have this
191 // auxiliary flag that one can set whenever one creates a
192 // type-error that is due to an error in a prior pass.
194 // Don't read this flag directly, call `is_tainted_by_errors()`
195 // and `set_tainted_by_errors()`.
196 tainted_by_errors_flag: Cell<bool>,
198 // Track how many errors were reported when this infcx is created.
199 // If the number of errors increases, that's also a sign (line
200 // `tained_by_errors`) to avoid reporting certain kinds of errors.
201 err_count_on_creation: usize,
203 // This flag is used for debugging, and is set to true if there are
204 // any obligations set during the current snapshot. In that case, the
205 // snapshot can't be rolled back.
206 pub obligations_in_snapshot: Cell<bool>,
209 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
210 /// region that each late-bound region was replaced with.
211 pub type SkolemizationMap<'tcx> = FxHashMap<ty::BoundRegion, &'tcx ty::Region>;
213 /// See `error_reporting.rs` for more details
214 #[derive(Clone, Debug)]
215 pub enum ValuePairs<'tcx> {
216 Types(ExpectedFound<Ty<'tcx>>),
217 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
218 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
221 /// The trace designates the path through inference that we took to
222 /// encounter an error or subtyping constraint.
224 /// See `error_reporting.rs` for more details.
226 pub struct TypeTrace<'tcx> {
227 cause: ObligationCause<'tcx>,
228 values: ValuePairs<'tcx>,
231 /// The origin of a `r1 <= r2` constraint.
233 /// See `error_reporting.rs` for more details
234 #[derive(Clone, Debug)]
235 pub enum SubregionOrigin<'tcx> {
236 // Arose from a subtyping relation
237 Subtype(TypeTrace<'tcx>),
239 // Stack-allocated closures cannot outlive innermost loop
240 // or function so as to ensure we only require finite stack
241 InfStackClosure(Span),
243 // Invocation of closure must be within its lifetime
246 // Dereference of reference must be within its lifetime
249 // Closure bound must not outlive captured free variables
250 FreeVariable(Span, ast::NodeId),
252 // Index into slice must be within its lifetime
255 // When casting `&'a T` to an `&'b Trait` object,
256 // relating `'a` to `'b`
257 RelateObjectBound(Span),
259 // Some type parameter was instantiated with the given type,
260 // and that type must outlive some region.
261 RelateParamBound(Span, Ty<'tcx>),
263 // The given region parameter was instantiated with a region
264 // that must outlive some other region.
265 RelateRegionParamBound(Span),
267 // A bound placed on type parameters that states that must outlive
268 // the moment of their instantiation.
269 RelateDefaultParamBound(Span, Ty<'tcx>),
271 // Creating a pointer `b` to contents of another reference
274 // Creating a pointer `b` to contents of an upvar
275 ReborrowUpvar(Span, ty::UpvarId),
277 // Data with type `Ty<'tcx>` was borrowed
278 DataBorrowed(Ty<'tcx>, Span),
280 // (&'a &'b T) where a >= b
281 ReferenceOutlivesReferent(Ty<'tcx>, Span),
283 // Type or region parameters must be in scope.
284 ParameterInScope(ParameterOrigin, Span),
286 // The type T of an expression E must outlive the lifetime for E.
287 ExprTypeIsNotInScope(Ty<'tcx>, Span),
289 // A `ref b` whose region does not enclose the decl site
290 BindingTypeIsNotValidAtDecl(Span),
292 // Regions appearing in a method receiver must outlive method call
295 // Regions appearing in a function argument must outlive func call
298 // Region in return type of invoked fn must enclose call
301 // Operands must be in scope
304 // Region resulting from a `&` expr must enclose the `&` expr
307 // An auto-borrow that does not enclose the expr where it occurs
310 // Region constraint arriving from destructor safety
311 SafeDestructor(Span),
313 // Comparing the signature and requirements of an impl method against
314 // the containing trait.
315 CompareImplMethodObligation {
317 item_name: ast::Name,
318 impl_item_def_id: DefId,
319 trait_item_def_id: DefId,
321 // this is `Some(_)` if this error arises from the bug fix for
322 // #18937. This is a temporary measure.
323 lint_id: Option<ast::NodeId>,
327 /// Places that type/region parameters can appear.
328 #[derive(Clone, Copy, Debug)]
329 pub enum ParameterOrigin {
331 MethodCall, // foo.bar() <-- parameters on impl providing bar()
332 OverloadedOperator, // a + b when overloaded
333 OverloadedDeref, // *a when overloaded
336 /// Times when we replace late-bound regions with variables:
337 #[derive(Clone, Copy, Debug)]
338 pub enum LateBoundRegionConversionTime {
339 /// when a fn is called
342 /// when two higher-ranked types are compared
345 /// when projecting an associated type
346 AssocTypeProjection(ast::Name),
349 /// Reasons to create a region inference variable
351 /// See `error_reporting.rs` for more details
352 #[derive(Clone, Debug)]
353 pub enum RegionVariableOrigin {
354 // Region variables created for ill-categorized reasons,
355 // mostly indicates places in need of refactoring
358 // Regions created by a `&P` or `[...]` pattern
361 // Regions created by `&` operator
364 // Regions created as part of an autoref of a method receiver
367 // Regions created as part of an automatic coercion
370 // Region variables created as the values for early-bound regions
371 EarlyBoundRegion(Span, ast::Name, Option<ty::Issue32330>),
373 // Region variables created for bound regions
374 // in a function or method that is called
375 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
377 UpvarRegion(ty::UpvarId, Span),
379 BoundRegionInCoherence(ast::Name),
382 #[derive(Copy, Clone, Debug)]
383 pub enum FixupError {
384 UnresolvedIntTy(IntVid),
385 UnresolvedFloatTy(FloatVid),
389 impl fmt::Display for FixupError {
390 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
391 use self::FixupError::*;
394 UnresolvedIntTy(_) => {
395 write!(f, "cannot determine the type of this integer; \
396 add a suffix to specify the type explicitly")
398 UnresolvedFloatTy(_) => {
399 write!(f, "cannot determine the type of this number; \
400 add a suffix to specify the type explicitly")
402 UnresolvedTy(_) => write!(f, "unconstrained type")
407 pub trait InferEnv<'a, 'tcx> {
408 fn to_parts(self, tcx: TyCtxt<'a, 'tcx, 'tcx>)
409 -> (Option<&'a ty::TypeckTables<'tcx>>,
410 Option<ty::TypeckTables<'tcx>>,
411 Option<ty::ParameterEnvironment<'tcx>>);
414 impl<'a, 'tcx> InferEnv<'a, 'tcx> for () {
415 fn to_parts(self, _: TyCtxt<'a, 'tcx, 'tcx>)
416 -> (Option<&'a ty::TypeckTables<'tcx>>,
417 Option<ty::TypeckTables<'tcx>>,
418 Option<ty::ParameterEnvironment<'tcx>>) {
423 impl<'a, 'tcx> InferEnv<'a, 'tcx> for ty::ParameterEnvironment<'tcx> {
424 fn to_parts(self, _: TyCtxt<'a, 'tcx, 'tcx>)
425 -> (Option<&'a ty::TypeckTables<'tcx>>,
426 Option<ty::TypeckTables<'tcx>>,
427 Option<ty::ParameterEnvironment<'tcx>>) {
428 (None, None, Some(self))
432 impl<'a, 'tcx> InferEnv<'a, 'tcx> for (&'a ty::TypeckTables<'tcx>, ty::ParameterEnvironment<'tcx>) {
433 fn to_parts(self, _: TyCtxt<'a, 'tcx, 'tcx>)
434 -> (Option<&'a ty::TypeckTables<'tcx>>,
435 Option<ty::TypeckTables<'tcx>>,
436 Option<ty::ParameterEnvironment<'tcx>>) {
437 (Some(self.0), None, Some(self.1))
441 impl<'a, 'tcx> InferEnv<'a, 'tcx> for (ty::TypeckTables<'tcx>, ty::ParameterEnvironment<'tcx>) {
442 fn to_parts(self, _: TyCtxt<'a, 'tcx, 'tcx>)
443 -> (Option<&'a ty::TypeckTables<'tcx>>,
444 Option<ty::TypeckTables<'tcx>>,
445 Option<ty::ParameterEnvironment<'tcx>>) {
446 (None, Some(self.0), Some(self.1))
450 impl<'a, 'tcx> InferEnv<'a, 'tcx> for hir::BodyId {
451 fn to_parts(self, tcx: TyCtxt<'a, 'tcx, 'tcx>)
452 -> (Option<&'a ty::TypeckTables<'tcx>>,
453 Option<ty::TypeckTables<'tcx>>,
454 Option<ty::ParameterEnvironment<'tcx>>) {
455 let item_id = tcx.hir.body_owner(self);
456 (Some(tcx.item_tables(tcx.hir.local_def_id(item_id))),
458 Some(ty::ParameterEnvironment::for_item(tcx, item_id)))
462 /// Helper type of a temporary returned by tcx.infer_ctxt(...).
463 /// Necessary because we can't write the following bound:
464 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(InferCtxt<'b, 'gcx, 'tcx>).
465 pub struct InferCtxtBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
466 global_tcx: TyCtxt<'a, 'gcx, 'gcx>,
467 arena: DroplessArena,
468 fresh_tables: Option<RefCell<ty::TypeckTables<'tcx>>>,
469 tables: Option<&'a ty::TypeckTables<'gcx>>,
470 param_env: Option<ty::ParameterEnvironment<'gcx>>,
471 projection_mode: Reveal,
474 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'gcx> {
475 pub fn infer_ctxt<E: InferEnv<'a, 'gcx>>(self,
477 projection_mode: Reveal)
478 -> InferCtxtBuilder<'a, 'gcx, 'tcx> {
479 let (tables, fresh_tables, param_env) = env.to_parts(self);
482 arena: DroplessArena::new(),
483 fresh_tables: fresh_tables.map(RefCell::new),
485 param_env: param_env,
486 projection_mode: projection_mode,
490 /// Fake InferCtxt with the global tcx. Used by pre-MIR borrowck
491 /// for MemCategorizationContext/ExprUseVisitor.
492 /// If any inference functionality is used, ICEs will occur.
493 pub fn borrowck_fake_infer_ctxt(self, body: hir::BodyId)
494 -> InferCtxt<'a, 'gcx, 'gcx> {
495 let (tables, _, param_env) = body.to_parts(self);
498 tables: InferTables::Interned(tables.unwrap()),
499 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
500 int_unification_table: RefCell::new(UnificationTable::new()),
501 float_unification_table: RefCell::new(UnificationTable::new()),
502 region_vars: RegionVarBindings::new(self),
503 parameter_environment: param_env.unwrap(),
504 selection_cache: traits::SelectionCache::new(),
505 evaluation_cache: traits::EvaluationCache::new(),
506 projection_cache: RefCell::new(traits::ProjectionCache::new()),
507 reported_trait_errors: RefCell::new(FxHashSet()),
508 projection_mode: Reveal::NotSpecializable,
509 tainted_by_errors_flag: Cell::new(false),
510 err_count_on_creation: self.sess.err_count(),
511 obligations_in_snapshot: Cell::new(false),
516 impl<'a, 'gcx, 'tcx> InferCtxtBuilder<'a, 'gcx, 'tcx> {
517 pub fn enter<F, R>(&'tcx mut self, f: F) -> R
518 where F: for<'b> FnOnce(InferCtxt<'b, 'gcx, 'tcx>) -> R
520 let InferCtxtBuilder {
528 let tables = tables.map(InferTables::Interned).unwrap_or_else(|| {
529 fresh_tables.as_ref().map_or(InferTables::Missing, InferTables::InProgress)
531 let param_env = param_env.take().unwrap_or_else(|| {
532 global_tcx.empty_parameter_environment()
534 global_tcx.enter_local(arena, |tcx| f(InferCtxt {
537 projection_cache: RefCell::new(traits::ProjectionCache::new()),
538 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
539 int_unification_table: RefCell::new(UnificationTable::new()),
540 float_unification_table: RefCell::new(UnificationTable::new()),
541 region_vars: RegionVarBindings::new(tcx),
542 parameter_environment: param_env,
543 selection_cache: traits::SelectionCache::new(),
544 evaluation_cache: traits::EvaluationCache::new(),
545 reported_trait_errors: RefCell::new(FxHashSet()),
546 projection_mode: projection_mode,
547 tainted_by_errors_flag: Cell::new(false),
548 err_count_on_creation: tcx.sess.err_count(),
549 obligations_in_snapshot: Cell::new(false),
554 impl<T> ExpectedFound<T> {
555 fn new(a_is_expected: bool, a: T, b: T) -> Self {
557 ExpectedFound {expected: a, found: b}
559 ExpectedFound {expected: b, found: a}
564 impl<'tcx, T> InferOk<'tcx, T> {
565 pub fn unit(self) -> InferOk<'tcx, ()> {
566 InferOk { value: (), obligations: self.obligations }
570 #[must_use = "once you start a snapshot, you should always consume it"]
571 pub struct CombinedSnapshot {
572 projection_cache_snapshot: traits::ProjectionCacheSnapshot,
573 type_snapshot: type_variable::Snapshot,
574 int_snapshot: unify::Snapshot<ty::IntVid>,
575 float_snapshot: unify::Snapshot<ty::FloatVid>,
576 region_vars_snapshot: RegionSnapshot,
577 obligations_in_snapshot: bool,
580 /// Helper trait for shortening the lifetimes inside a
581 /// value for post-type-checking normalization.
582 pub trait TransNormalize<'gcx>: TypeFoldable<'gcx> {
583 fn trans_normalize<'a, 'tcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>) -> Self;
586 macro_rules! items { ($($item:item)+) => ($($item)+) }
587 macro_rules! impl_trans_normalize {
588 ($lt_gcx:tt, $($ty:ty),+) => {
589 items!($(impl<$lt_gcx> TransNormalize<$lt_gcx> for $ty {
590 fn trans_normalize<'a, 'tcx>(&self,
591 infcx: &InferCtxt<'a, $lt_gcx, 'tcx>)
593 infcx.normalize_projections_in(self)
599 impl_trans_normalize!('gcx,
603 &'gcx ty::BareFnTy<'gcx>,
604 ty::ClosureSubsts<'gcx>,
605 ty::PolyTraitRef<'gcx>,
606 ty::ExistentialTraitRef<'gcx>
609 impl<'gcx> TransNormalize<'gcx> for LvalueTy<'gcx> {
610 fn trans_normalize<'a, 'tcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>) -> Self {
612 LvalueTy::Ty { ty } => LvalueTy::Ty { ty: ty.trans_normalize(infcx) },
613 LvalueTy::Downcast { adt_def, substs, variant_index } => {
616 substs: substs.trans_normalize(infcx),
617 variant_index: variant_index
624 // NOTE: Callable from trans only!
625 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
626 /// Currently, higher-ranked type bounds inhibit normalization. Therefore,
627 /// each time we erase them in translation, we need to normalize
629 pub fn erase_late_bound_regions_and_normalize<T>(self, value: &ty::Binder<T>)
631 where T: TransNormalize<'tcx>
633 assert!(!value.needs_subst());
634 let value = self.erase_late_bound_regions(value);
635 self.normalize_associated_type(&value)
638 pub fn normalize_associated_type<T>(self, value: &T) -> T
639 where T: TransNormalize<'tcx>
641 debug!("normalize_associated_type(t={:?})", value);
643 let value = self.erase_regions(value);
645 if !value.has_projection_types() {
649 self.infer_ctxt((), Reveal::All).enter(|infcx| {
650 value.trans_normalize(&infcx)
654 pub fn normalize_associated_type_in_env<T>(
655 self, value: &T, env: &'a ty::ParameterEnvironment<'tcx>
657 where T: TransNormalize<'tcx>
659 debug!("normalize_associated_type_in_env(t={:?})", value);
661 let value = self.erase_regions(value);
663 if !value.has_projection_types() {
667 self.infer_ctxt(env.clone(), Reveal::All).enter(|infcx| {
668 value.trans_normalize(&infcx)
673 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
674 fn normalize_projections_in<T>(&self, value: &T) -> T::Lifted
675 where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
677 let mut selcx = traits::SelectionContext::new(self);
678 let cause = traits::ObligationCause::dummy();
679 let traits::Normalized { value: result, obligations } =
680 traits::normalize(&mut selcx, cause, value);
682 debug!("normalize_projections_in: result={:?} obligations={:?}",
683 result, obligations);
685 let mut fulfill_cx = traits::FulfillmentContext::new();
687 for obligation in obligations {
688 fulfill_cx.register_predicate_obligation(self, obligation);
691 self.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &result)
694 /// Finishes processes any obligations that remain in the
695 /// fulfillment context, and then returns the result with all type
696 /// variables removed and regions erased. Because this is intended
697 /// for use after type-check has completed, if any errors occur,
698 /// it will panic. It is used during normalization and other cases
699 /// where processing the obligations in `fulfill_cx` may cause
700 /// type inference variables that appear in `result` to be
701 /// unified, and hence we need to process those obligations to get
702 /// the complete picture of the type.
703 pub fn drain_fulfillment_cx_or_panic<T>(&self,
705 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
708 where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
710 debug!("drain_fulfillment_cx_or_panic()");
712 // In principle, we only need to do this so long as `result`
713 // contains unbound type parameters. It could be a slight
714 // optimization to stop iterating early.
715 match fulfill_cx.select_all_or_error(self) {
718 span_bug!(span, "Encountered errors `{:?}` resolving bounds after type-checking",
723 let result = self.resolve_type_vars_if_possible(result);
724 let result = self.tcx.erase_regions(&result);
726 match self.tcx.lift_to_global(&result) {
727 Some(result) => result,
729 span_bug!(span, "Uninferred types/regions in `{:?}`", result);
734 pub fn projection_mode(&self) -> Reveal {
738 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
739 t.fold_with(&mut self.freshener())
742 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
744 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
749 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'gcx, 'tcx> {
750 freshen::TypeFreshener::new(self)
753 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
754 use ty::error::UnconstrainedNumeric::Neither;
755 use ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
757 ty::TyInfer(ty::IntVar(vid)) => {
758 if self.int_unification_table.borrow_mut().has_value(vid) {
764 ty::TyInfer(ty::FloatVar(vid)) => {
765 if self.float_unification_table.borrow_mut().has_value(vid) {
775 /// Returns a type variable's default fallback if any exists. A default
776 /// must be attached to the variable when created, if it is created
777 /// without a default, this will return None.
779 /// This code does not apply to integral or floating point variables,
780 /// only to use declared defaults.
782 /// See `new_ty_var_with_default` to create a type variable with a default.
783 /// See `type_variable::Default` for details about what a default entails.
784 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
786 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
791 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
792 let mut variables = Vec::new();
794 let unbound_ty_vars = self.type_variables
796 .unsolved_variables()
798 .map(|t| self.tcx.mk_var(t));
800 let unbound_int_vars = self.int_unification_table
802 .unsolved_variables()
804 .map(|v| self.tcx.mk_int_var(v));
806 let unbound_float_vars = self.float_unification_table
808 .unsolved_variables()
810 .map(|v| self.tcx.mk_float_var(v));
812 variables.extend(unbound_ty_vars);
813 variables.extend(unbound_int_vars);
814 variables.extend(unbound_float_vars);
819 fn combine_fields(&'a self, trace: TypeTrace<'tcx>)
820 -> CombineFields<'a, 'gcx, 'tcx> {
825 obligations: PredicateObligations::new(),
829 pub fn equate<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
830 -> InferResult<'tcx, T>
831 where T: Relate<'tcx>
833 let mut fields = self.combine_fields(trace);
834 let result = fields.equate(a_is_expected).relate(a, b);
835 result.map(move |t| InferOk { value: t, obligations: fields.obligations })
838 pub fn sub<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
839 -> InferResult<'tcx, T>
840 where T: Relate<'tcx>
842 let mut fields = self.combine_fields(trace);
843 let result = fields.sub(a_is_expected).relate(a, b);
844 result.map(move |t| InferOk { value: t, obligations: fields.obligations })
847 pub fn lub<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
848 -> InferResult<'tcx, T>
849 where T: Relate<'tcx>
851 let mut fields = self.combine_fields(trace);
852 let result = fields.lub(a_is_expected).relate(a, b);
853 result.map(move |t| InferOk { value: t, obligations: fields.obligations })
856 pub fn glb<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
857 -> InferResult<'tcx, T>
858 where T: Relate<'tcx>
860 let mut fields = self.combine_fields(trace);
861 let result = fields.glb(a_is_expected).relate(a, b);
862 result.map(move |t| InferOk { value: t, obligations: fields.obligations })
865 // Clear the "obligations in snapshot" flag, invoke the closure,
866 // then restore the flag to its original value. This flag is a
867 // debugging measure designed to detect cases where we start a
868 // snapshot, create type variables, register obligations involving
869 // those type variables in the fulfillment cx, and then have to
870 // unroll the snapshot, leaving "dangling type variables" behind.
871 // In such cases, the flag will be set by the fulfillment cx, and
872 // an assertion will fail when rolling the snapshot back. Very
873 // useful, much better than grovelling through megabytes of
876 // HOWEVER, in some cases the flag is wrong. In particular, we
877 // sometimes create a "mini-fulfilment-cx" in which we enroll
878 // obligations. As long as this fulfillment cx is fully drained
879 // before we return, this is not a problem, as there won't be any
880 // escaping obligations in the main cx. In those cases, you can
881 // use this function.
882 pub fn save_and_restore_obligations_in_snapshot_flag<F, R>(&self, func: F) -> R
883 where F: FnOnce(&Self) -> R
885 let flag = self.obligations_in_snapshot.get();
886 self.obligations_in_snapshot.set(false);
887 let result = func(self);
888 self.obligations_in_snapshot.set(flag);
892 fn start_snapshot(&self) -> CombinedSnapshot {
893 debug!("start_snapshot()");
895 let obligations_in_snapshot = self.obligations_in_snapshot.get();
896 self.obligations_in_snapshot.set(false);
899 projection_cache_snapshot: self.projection_cache.borrow_mut().snapshot(),
900 type_snapshot: self.type_variables.borrow_mut().snapshot(),
901 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
902 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
903 region_vars_snapshot: self.region_vars.start_snapshot(),
904 obligations_in_snapshot: obligations_in_snapshot,
908 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
909 debug!("rollback_to(cause={})", cause);
910 let CombinedSnapshot { projection_cache_snapshot,
914 region_vars_snapshot,
915 obligations_in_snapshot } = snapshot;
917 assert!(!self.obligations_in_snapshot.get());
918 self.obligations_in_snapshot.set(obligations_in_snapshot);
920 self.projection_cache
922 .rollback_to(projection_cache_snapshot);
925 .rollback_to(type_snapshot);
926 self.int_unification_table
928 .rollback_to(int_snapshot);
929 self.float_unification_table
931 .rollback_to(float_snapshot);
933 .rollback_to(region_vars_snapshot);
936 fn commit_from(&self, snapshot: CombinedSnapshot) {
937 debug!("commit_from()");
938 let CombinedSnapshot { projection_cache_snapshot,
942 region_vars_snapshot,
943 obligations_in_snapshot } = snapshot;
945 self.obligations_in_snapshot.set(obligations_in_snapshot);
947 self.projection_cache
949 .commit(projection_cache_snapshot);
952 .commit(type_snapshot);
953 self.int_unification_table
955 .commit(int_snapshot);
956 self.float_unification_table
958 .commit(float_snapshot);
960 .commit(region_vars_snapshot);
963 /// Execute `f` and commit the bindings
964 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
968 let snapshot = self.start_snapshot();
970 self.commit_from(snapshot);
974 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
975 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
976 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
978 debug!("commit_if_ok()");
979 let snapshot = self.start_snapshot();
980 let r = f(&snapshot);
981 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
983 Ok(_) => { self.commit_from(snapshot); }
984 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
989 // Execute `f` in a snapshot, and commit the bindings it creates
990 pub fn in_snapshot<T, F>(&self, f: F) -> T where
991 F: FnOnce(&CombinedSnapshot) -> T
993 debug!("in_snapshot()");
994 let snapshot = self.start_snapshot();
995 let r = f(&snapshot);
996 self.commit_from(snapshot);
1000 /// Execute `f` then unroll any bindings it creates
1001 pub fn probe<R, F>(&self, f: F) -> R where
1002 F: FnOnce(&CombinedSnapshot) -> R,
1005 let snapshot = self.start_snapshot();
1006 let r = f(&snapshot);
1007 self.rollback_to("probe", snapshot);
1011 pub fn add_given(&self,
1012 sub: ty::FreeRegion,
1015 self.region_vars.add_given(sub, sup);
1018 pub fn sub_types(&self,
1019 a_is_expected: bool,
1020 cause: &ObligationCause<'tcx>,
1023 -> InferResult<'tcx, ()>
1025 debug!("sub_types({:?} <: {:?})", a, b);
1026 self.commit_if_ok(|_| {
1027 let trace = TypeTrace::types(cause, a_is_expected, a, b);
1028 self.sub(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
1032 pub fn can_sub_types(&self,
1038 let origin = &ObligationCause::dummy();
1039 let trace = TypeTrace::types(origin, true, a, b);
1040 self.sub(true, trace, &a, &b).map(|InferOk { obligations, .. }| {
1041 // FIXME(#32730) propagate obligations
1042 assert!(obligations.is_empty());
1047 pub fn eq_types(&self,
1048 a_is_expected: bool,
1049 cause: &ObligationCause<'tcx>,
1052 -> InferResult<'tcx, ()>
1054 self.commit_if_ok(|_| {
1055 let trace = TypeTrace::types(cause, a_is_expected, a, b);
1056 self.equate(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
1060 pub fn eq_trait_refs(&self,
1061 a_is_expected: bool,
1062 cause: &ObligationCause<'tcx>,
1063 a: ty::TraitRef<'tcx>,
1064 b: ty::TraitRef<'tcx>)
1065 -> InferResult<'tcx, ()>
1067 debug!("eq_trait_refs({:?} = {:?})", a, b);
1068 self.commit_if_ok(|_| {
1069 let trace = TypeTrace {
1070 cause: cause.clone(),
1071 values: TraitRefs(ExpectedFound::new(a_is_expected, a, b))
1073 self.equate(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
1077 pub fn eq_impl_headers(&self,
1078 a_is_expected: bool,
1079 cause: &ObligationCause<'tcx>,
1080 a: &ty::ImplHeader<'tcx>,
1081 b: &ty::ImplHeader<'tcx>)
1082 -> InferResult<'tcx, ()>
1084 debug!("eq_impl_header({:?} = {:?})", a, b);
1085 match (a.trait_ref, b.trait_ref) {
1086 (Some(a_ref), Some(b_ref)) => self.eq_trait_refs(a_is_expected, cause, a_ref, b_ref),
1087 (None, None) => self.eq_types(a_is_expected, cause, a.self_ty, b.self_ty),
1088 _ => bug!("mk_eq_impl_headers given mismatched impl kinds"),
1092 pub fn sub_poly_trait_refs(&self,
1093 a_is_expected: bool,
1094 cause: ObligationCause<'tcx>,
1095 a: ty::PolyTraitRef<'tcx>,
1096 b: ty::PolyTraitRef<'tcx>)
1097 -> InferResult<'tcx, ()>
1099 debug!("sub_poly_trait_refs({:?} <: {:?})", a, b);
1100 self.commit_if_ok(|_| {
1101 let trace = TypeTrace {
1103 values: PolyTraitRefs(ExpectedFound::new(a_is_expected, a, b))
1105 self.sub(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
1109 pub fn sub_regions(&self,
1110 origin: SubregionOrigin<'tcx>,
1111 a: &'tcx ty::Region,
1112 b: &'tcx ty::Region) {
1113 debug!("sub_regions({:?} <: {:?})", a, b);
1114 self.region_vars.make_subregion(origin, a, b);
1117 pub fn equality_predicate(&self,
1118 cause: &ObligationCause<'tcx>,
1119 predicate: &ty::PolyEquatePredicate<'tcx>)
1120 -> InferResult<'tcx, ()>
1122 self.commit_if_ok(|snapshot| {
1123 let (ty::EquatePredicate(a, b), skol_map) =
1124 self.skolemize_late_bound_regions(predicate, snapshot);
1125 let cause_span = cause.span;
1126 let eqty_ok = self.eq_types(false, cause, a, b)?;
1127 self.leak_check(false, cause_span, &skol_map, snapshot)?;
1128 self.pop_skolemized(skol_map, snapshot);
1133 pub fn region_outlives_predicate(&self,
1134 cause: &traits::ObligationCause<'tcx>,
1135 predicate: &ty::PolyRegionOutlivesPredicate<'tcx>)
1138 self.commit_if_ok(|snapshot| {
1139 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
1140 self.skolemize_late_bound_regions(predicate, snapshot);
1142 SubregionOrigin::from_obligation_cause(cause,
1143 || RelateRegionParamBound(cause.span));
1144 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
1145 self.leak_check(false, cause.span, &skol_map, snapshot)?;
1146 Ok(self.pop_skolemized(skol_map, snapshot))
1150 pub fn next_ty_var_id(&self, diverging: bool, origin: TypeVariableOrigin) -> TyVid {
1153 .new_var(diverging, origin, None)
1156 pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1157 self.tcx.mk_var(self.next_ty_var_id(false, origin))
1160 pub fn next_diverging_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1161 self.tcx.mk_var(self.next_ty_var_id(true, origin))
1164 pub fn next_int_var_id(&self) -> IntVid {
1165 self.int_unification_table
1170 pub fn next_float_var_id(&self) -> FloatVid {
1171 self.float_unification_table
1176 pub fn next_region_var(&self, origin: RegionVariableOrigin)
1177 -> &'tcx ty::Region {
1178 self.tcx.mk_region(ty::ReVar(self.region_vars.new_region_var(origin)))
1181 /// Create a region inference variable for the given
1182 /// region parameter definition.
1183 pub fn region_var_for_def(&self,
1185 def: &ty::RegionParameterDef)
1186 -> &'tcx ty::Region {
1187 self.next_region_var(EarlyBoundRegion(span, def.name, def.issue_32330))
1190 /// Create a type inference variable for the given
1191 /// type parameter definition. The substitutions are
1192 /// for actual parameters that may be referred to by
1193 /// the default of this type parameter, if it exists.
1194 /// E.g. `struct Foo<A, B, C = (A, B)>(...);` when
1195 /// used in a path such as `Foo::<T, U>::new()` will
1196 /// use an inference variable for `C` with `[T, U]`
1197 /// as the substitutions for the default, `(T, U)`.
1198 pub fn type_var_for_def(&self,
1200 def: &ty::TypeParameterDef<'tcx>,
1201 substs: &[Kind<'tcx>])
1203 let default = def.default.map(|default| {
1204 type_variable::Default {
1205 ty: default.subst_spanned(self.tcx, substs, Some(span)),
1207 def_id: def.default_def_id
1212 let ty_var_id = self.type_variables
1215 TypeVariableOrigin::TypeParameterDefinition(span, def.name),
1218 self.tcx.mk_var(ty_var_id)
1221 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1222 /// type/region parameter to a fresh inference variable.
1223 pub fn fresh_substs_for_item(&self,
1226 -> &'tcx Substs<'tcx> {
1227 Substs::for_item(self.tcx, def_id, |def, _| {
1228 self.region_var_for_def(span, def)
1230 self.type_var_for_def(span, def, substs)
1234 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> &'tcx ty::Region {
1235 self.region_vars.new_bound(debruijn)
1238 /// True if errors have been reported since this infcx was
1239 /// created. This is sometimes used as a heuristic to skip
1240 /// reporting errors that often occur as a result of earlier
1241 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1242 /// inference variables, regionck errors).
1243 pub fn is_tainted_by_errors(&self) -> bool {
1244 debug!("is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1245 tainted_by_errors_flag={})",
1246 self.tcx.sess.err_count(),
1247 self.err_count_on_creation,
1248 self.tainted_by_errors_flag.get());
1250 if self.tcx.sess.err_count() > self.err_count_on_creation {
1251 return true; // errors reported since this infcx was made
1253 self.tainted_by_errors_flag.get()
1256 /// Set the "tainted by errors" flag to true. We call this when we
1257 /// observe an error from a prior pass.
1258 pub fn set_tainted_by_errors(&self) {
1259 debug!("set_tainted_by_errors()");
1260 self.tainted_by_errors_flag.set(true)
1263 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1264 match self.tables.borrow().node_types.get(&id) {
1267 None if self.is_tainted_by_errors() =>
1270 bug!("no type for node {}: {} in fcx",
1271 id, self.tcx.hir.node_to_string(id));
1276 pub fn expr_ty(&self, ex: &hir::Expr) -> Ty<'tcx> {
1277 match self.tables.borrow().node_types.get(&ex.id) {
1280 bug!("no type for expr in fcx");
1285 pub fn resolve_regions_and_report_errors(&self,
1286 free_regions: &FreeRegionMap,
1287 subject_node_id: ast::NodeId) {
1288 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1289 if !self.is_tainted_by_errors() {
1290 // As a heuristic, just skip reporting region errors
1291 // altogether if other errors have been reported while
1292 // this infcx was in use. This is totally hokey but
1293 // otherwise we have a hard time separating legit region
1294 // errors from silly ones.
1295 self.report_region_errors(&errors); // see error_reporting.rs
1299 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1300 self.resolve_type_vars_if_possible(&t).to_string()
1303 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1304 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1305 format!("({})", tstrs.join(", "))
1308 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1309 self.resolve_type_vars_if_possible(t).to_string()
1312 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1314 ty::TyInfer(ty::TyVar(v)) => {
1315 // Not entirely obvious: if `typ` is a type variable,
1316 // it can be resolved to an int/float variable, which
1317 // can then be recursively resolved, hence the
1318 // recursion. Note though that we prevent type
1319 // variables from unifying to other type variables
1320 // directly (though they may be embedded
1321 // structurally), and we prevent cycles in any case,
1322 // so this recursion should always be of very limited
1324 self.type_variables.borrow_mut()
1326 .map(|t| self.shallow_resolve(t))
1330 ty::TyInfer(ty::IntVar(v)) => {
1331 self.int_unification_table
1334 .map(|v| v.to_type(self.tcx))
1338 ty::TyInfer(ty::FloatVar(v)) => {
1339 self.float_unification_table
1342 .map(|v| v.to_type(self.tcx))
1352 pub fn resolve_type_vars_if_possible<T>(&self, value: &T) -> T
1353 where T: TypeFoldable<'tcx>
1356 * Where possible, replaces type/int/float variables in
1357 * `value` with their final value. Note that region variables
1358 * are unaffected. If a type variable has not been unified, it
1359 * is left as is. This is an idempotent operation that does
1360 * not affect inference state in any way and so you can do it
1364 if !value.needs_infer() {
1365 return value.clone(); // avoid duplicated subst-folding
1367 let mut r = resolve::OpportunisticTypeResolver::new(self);
1368 value.fold_with(&mut r)
1371 pub fn resolve_type_and_region_vars_if_possible<T>(&self, value: &T) -> T
1372 where T: TypeFoldable<'tcx>
1374 let mut r = resolve::OpportunisticTypeAndRegionResolver::new(self);
1375 value.fold_with(&mut r)
1378 /// Resolves all type variables in `t` and then, if any were left
1379 /// unresolved, substitutes an error type. This is used after the
1380 /// main checking when doing a second pass before writeback. The
1381 /// justification is that writeback will produce an error for
1382 /// these unconstrained type variables.
1383 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1384 let ty = self.resolve_type_vars_if_possible(t);
1385 if ty.references_error() || ty.is_ty_var() {
1386 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1393 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1395 * Attempts to resolve all type/region variables in
1396 * `value`. Region inference must have been run already (e.g.,
1397 * by calling `resolve_regions_and_report_errors`). If some
1398 * variable was never unified, an `Err` results.
1400 * This method is idempotent, but it not typically not invoked
1401 * except during the writeback phase.
1404 resolve::fully_resolve(self, value)
1407 // [Note-Type-error-reporting]
1408 // An invariant is that anytime the expected or actual type is TyError (the special
1409 // error type, meaning that an error occurred when typechecking this expression),
1410 // this is a derived error. The error cascaded from another error (that was already
1411 // reported), so it's not useful to display it to the user.
1412 // The following methods implement this logic.
1413 // They check if either the actual or expected type is TyError, and don't print the error
1414 // in this case. The typechecker should only ever report type errors involving mismatched
1415 // types using one of these methods, and should not call span_err directly for such
1418 pub fn type_error_message<M>(&self,
1421 actual_ty: Ty<'tcx>)
1422 where M: FnOnce(String) -> String,
1424 self.type_error_struct(sp, mk_msg, actual_ty).emit();
1427 // FIXME: this results in errors without an error code. Deprecate?
1428 pub fn type_error_struct<M>(&self,
1431 actual_ty: Ty<'tcx>)
1432 -> DiagnosticBuilder<'tcx>
1433 where M: FnOnce(String) -> String,
1435 self.type_error_struct_with_diag(sp, |actual_ty| {
1436 self.tcx.sess.struct_span_err(sp, &mk_msg(actual_ty))
1440 pub fn type_error_struct_with_diag<M>(&self,
1443 actual_ty: Ty<'tcx>)
1444 -> DiagnosticBuilder<'tcx>
1445 where M: FnOnce(String) -> DiagnosticBuilder<'tcx>,
1447 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1448 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1450 // Don't report an error if actual type is TyError.
1451 if actual_ty.references_error() {
1452 return self.tcx.sess.diagnostic().struct_dummy();
1455 mk_diag(self.ty_to_string(actual_ty))
1458 pub fn report_mismatched_types(&self,
1459 cause: &ObligationCause<'tcx>,
1462 err: TypeError<'tcx>)
1463 -> DiagnosticBuilder<'tcx> {
1464 let trace = TypeTrace::types(cause, true, expected, actual);
1465 self.report_and_explain_type_error(trace, &err)
1468 pub fn report_conflicting_default_types(&self,
1470 body_id: ast::NodeId,
1471 expected: type_variable::Default<'tcx>,
1472 actual: type_variable::Default<'tcx>) {
1473 let trace = TypeTrace {
1474 cause: ObligationCause::misc(span, body_id),
1475 values: Types(ExpectedFound {
1476 expected: expected.ty,
1481 self.report_and_explain_type_error(
1483 &TypeError::TyParamDefaultMismatch(ExpectedFound {
1490 pub fn replace_late_bound_regions_with_fresh_var<T>(
1493 lbrct: LateBoundRegionConversionTime,
1494 value: &ty::Binder<T>)
1495 -> (T, FxHashMap<ty::BoundRegion, &'tcx ty::Region>)
1496 where T : TypeFoldable<'tcx>
1498 self.tcx.replace_late_bound_regions(
1500 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1503 /// Given a higher-ranked projection predicate like:
1505 /// for<'a> <T as Fn<&'a u32>>::Output = &'a u32
1507 /// and a target trait-ref like:
1509 /// <T as Fn<&'x u32>>
1511 /// find a substitution `S` for the higher-ranked regions (here,
1512 /// `['a => 'x]`) such that the predicate matches the trait-ref,
1513 /// and then return the value (here, `&'a u32`) but with the
1514 /// substitution applied (hence, `&'x u32`).
1516 /// See `higher_ranked_match` in `higher_ranked/mod.rs` for more
1518 pub fn match_poly_projection_predicate(&self,
1519 cause: ObligationCause<'tcx>,
1520 match_a: ty::PolyProjectionPredicate<'tcx>,
1521 match_b: ty::TraitRef<'tcx>)
1522 -> InferResult<'tcx, HrMatchResult<Ty<'tcx>>>
1524 let span = cause.span;
1525 let match_trait_ref = match_a.skip_binder().projection_ty.trait_ref;
1526 let trace = TypeTrace {
1528 values: TraitRefs(ExpectedFound::new(true, match_trait_ref, match_b))
1531 let match_pair = match_a.map_bound(|p| (p.projection_ty.trait_ref, p.ty));
1532 let mut combine = self.combine_fields(trace);
1533 let result = combine.higher_ranked_match(span, &match_pair, &match_b, true)?;
1534 Ok(InferOk { value: result, obligations: combine.obligations })
1537 /// See `verify_generic_bound` method in `region_inference`
1538 pub fn verify_generic_bound(&self,
1539 origin: SubregionOrigin<'tcx>,
1540 kind: GenericKind<'tcx>,
1541 a: &'tcx ty::Region,
1542 bound: VerifyBound<'tcx>) {
1543 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1548 self.region_vars.verify_generic_bound(origin, kind, a, bound);
1551 pub fn can_equate<T>(&self, a: &T, b: &T) -> UnitResult<'tcx>
1552 where T: Relate<'tcx> + fmt::Debug
1554 debug!("can_equate({:?}, {:?})", a, b);
1556 // Gin up a dummy trace, since this won't be committed
1557 // anyhow. We should make this typetrace stuff more
1558 // generic so we don't have to do anything quite this
1560 let trace = TypeTrace::dummy(self.tcx);
1561 self.equate(true, trace, a, b).map(|InferOk { obligations, .. }| {
1562 // FIXME(#32730) propagate obligations
1563 assert!(obligations.is_empty());
1568 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1569 let ty = self.node_type(id);
1570 self.resolve_type_vars_or_error(&ty)
1573 pub fn expr_ty_adjusted(&self, expr: &hir::Expr) -> McResult<Ty<'tcx>> {
1574 let ty = self.tables.borrow().expr_ty_adjusted(expr);
1575 self.resolve_type_vars_or_error(&ty)
1578 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1579 let ty = self.resolve_type_vars_if_possible(&ty);
1580 if let Some(ty) = self.tcx.lift_to_global(&ty) {
1581 // Even if the type may have no inference variables, during
1582 // type-checking closure types are in local tables only.
1583 let local_closures = match self.tables {
1584 InferTables::InProgress(_) => ty.has_closure_types(),
1587 if !local_closures {
1588 return ty.moves_by_default(self.tcx.global_tcx(), self.param_env(), span);
1592 let copy_def_id = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
1594 // this can get called from typeck (by euv), and moves_by_default
1595 // rightly refuses to work with inference variables, but
1596 // moves_by_default has a cache, which we want to use in other
1598 !traits::type_known_to_meet_bound(self, ty, copy_def_id, span)
1601 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1602 -> Option<Ty<'tcx>> {
1607 .map(|method| method.ty)
1608 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1611 pub fn node_method_id(&self, method_call: ty::MethodCall)
1617 .map(|method| method.def_id)
1620 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1621 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1624 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture<'tcx>> {
1625 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1628 pub fn param_env(&self) -> &ty::ParameterEnvironment<'gcx> {
1629 &self.parameter_environment
1632 pub fn closure_kind(&self,
1634 -> Option<ty::ClosureKind>
1636 if let InferTables::InProgress(tables) = self.tables {
1637 if let Some(id) = self.tcx.hir.as_local_node_id(def_id) {
1638 return tables.borrow().closure_kinds.get(&id).cloned();
1642 // During typeck, ALL closures are local. But afterwards,
1643 // during trans, we see closure ids from other traits.
1644 // That may require loading the closure data out of the
1646 Some(self.tcx.closure_kind(def_id))
1649 pub fn closure_type(&self,
1651 substs: ty::ClosureSubsts<'tcx>)
1652 -> ty::ClosureTy<'tcx>
1654 if let InferTables::InProgress(tables) = self.tables {
1655 if let Some(id) = self.tcx.hir.as_local_node_id(def_id) {
1656 if let Some(ty) = tables.borrow().closure_tys.get(&id) {
1657 return ty.subst(self.tcx, substs.substs);
1662 self.tcx.closure_type(def_id, substs)
1666 impl<'a, 'gcx, 'tcx> TypeTrace<'tcx> {
1667 pub fn span(&self) -> Span {
1671 pub fn types(cause: &ObligationCause<'tcx>,
1672 a_is_expected: bool,
1675 -> TypeTrace<'tcx> {
1677 cause: cause.clone(),
1678 values: Types(ExpectedFound::new(a_is_expected, a, b))
1682 pub fn dummy(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> TypeTrace<'tcx> {
1684 cause: ObligationCause::dummy(),
1685 values: Types(ExpectedFound {
1686 expected: tcx.types.err,
1687 found: tcx.types.err,
1693 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1694 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1695 write!(f, "TypeTrace({:?})", self.cause)
1699 impl<'tcx> SubregionOrigin<'tcx> {
1700 pub fn span(&self) -> Span {
1702 Subtype(ref a) => a.span(),
1703 InfStackClosure(a) => a,
1704 InvokeClosure(a) => a,
1705 DerefPointer(a) => a,
1706 FreeVariable(a, _) => a,
1708 RelateObjectBound(a) => a,
1709 RelateParamBound(a, _) => a,
1710 RelateRegionParamBound(a) => a,
1711 RelateDefaultParamBound(a, _) => a,
1713 ReborrowUpvar(a, _) => a,
1714 DataBorrowed(_, a) => a,
1715 ReferenceOutlivesReferent(_, a) => a,
1716 ParameterInScope(_, a) => a,
1717 ExprTypeIsNotInScope(_, a) => a,
1718 BindingTypeIsNotValidAtDecl(a) => a,
1725 SafeDestructor(a) => a,
1726 CompareImplMethodObligation { span, .. } => span,
1730 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>,
1733 where F: FnOnce() -> Self
1736 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) =>
1737 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span),
1739 traits::ObligationCauseCode::CompareImplMethodObligation { item_name,
1743 SubregionOrigin::CompareImplMethodObligation {
1745 item_name: item_name,
1746 impl_item_def_id: impl_item_def_id,
1747 trait_item_def_id: trait_item_def_id,
1756 impl RegionVariableOrigin {
1757 pub fn span(&self) -> Span {
1759 MiscVariable(a) => a,
1760 PatternRegion(a) => a,
1761 AddrOfRegion(a) => a,
1764 EarlyBoundRegion(a, ..) => a,
1765 LateBoundRegion(a, ..) => a,
1766 BoundRegionInCoherence(_) => syntax_pos::DUMMY_SP,
1767 UpvarRegion(_, a) => a
1772 impl<'tcx> TypeFoldable<'tcx> for ValuePairs<'tcx> {
1773 fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
1775 ValuePairs::Types(ref ef) => {
1776 ValuePairs::Types(ef.fold_with(folder))
1778 ValuePairs::TraitRefs(ref ef) => {
1779 ValuePairs::TraitRefs(ef.fold_with(folder))
1781 ValuePairs::PolyTraitRefs(ref ef) => {
1782 ValuePairs::PolyTraitRefs(ef.fold_with(folder))
1787 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1789 ValuePairs::Types(ref ef) => ef.visit_with(visitor),
1790 ValuePairs::TraitRefs(ref ef) => ef.visit_with(visitor),
1791 ValuePairs::PolyTraitRefs(ref ef) => ef.visit_with(visitor),
1796 impl<'tcx> TypeFoldable<'tcx> for TypeTrace<'tcx> {
1797 fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
1799 cause: self.cause.fold_with(folder),
1800 values: self.values.fold_with(folder)
1804 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1805 self.cause.visit_with(visitor) || self.values.visit_with(visitor)