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::region::CodeExtent;
27 use mir::tcx::LvalueTy;
28 use ty::subst::{Subst, Substs};
30 use ty::{TyVid, IntVid, FloatVid};
31 use ty::{self, Ty, TyCtxt};
32 use ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
33 use ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
34 use ty::relate::{Relate, RelateResult, TypeRelation};
35 use traits::{self, PredicateObligations, Reveal};
36 use rustc_data_structures::unify::{self, UnificationTable};
37 use std::cell::{Cell, RefCell, Ref, RefMut};
40 use errors::DiagnosticBuilder;
41 use syntax_pos::{self, Span, DUMMY_SP};
42 use util::nodemap::{FnvHashMap, FnvHashSet, NodeMap};
44 use self::combine::CombineFields;
45 use self::higher_ranked::HrMatchResult;
46 use self::region_inference::{RegionVarBindings, RegionSnapshot};
47 use self::unify_key::ToType;
52 pub mod error_reporting;
57 pub mod region_inference;
61 pub mod type_variable;
65 pub struct InferOk<'tcx, T> {
67 pub obligations: PredicateObligations<'tcx>,
69 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
71 pub type Bound<T> = Option<T>;
72 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
73 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
75 /// A version of &ty::Tables which can be global or local.
76 /// Only the local version supports borrow_mut.
77 #[derive(Copy, Clone)]
78 pub enum InferTables<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
79 Global(&'a RefCell<ty::Tables<'gcx>>),
80 Local(&'a RefCell<ty::Tables<'tcx>>)
83 impl<'a, 'gcx, 'tcx> InferTables<'a, 'gcx, 'tcx> {
84 pub fn borrow(self) -> Ref<'a, ty::Tables<'tcx>> {
86 InferTables::Global(tables) => tables.borrow(),
87 InferTables::Local(tables) => tables.borrow()
91 pub fn borrow_mut(self) -> RefMut<'a, ty::Tables<'tcx>> {
93 InferTables::Global(_) => {
94 bug!("InferTables: infcx.tables.borrow_mut() outside of type-checking");
96 InferTables::Local(tables) => tables.borrow_mut()
101 pub struct InferCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
102 pub tcx: TyCtxt<'a, 'gcx, 'tcx>,
104 pub tables: InferTables<'a, 'gcx, 'tcx>,
106 // Cache for projections. This cache is snapshotted along with the
109 // Public so that `traits::project` can use it.
110 pub projection_cache: RefCell<traits::ProjectionCache<'tcx>>,
112 // We instantiate UnificationTable with bounds<Ty> because the
113 // types that might instantiate a general type variable have an
114 // order, represented by its upper and lower bounds.
115 type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
117 // Map from integral variable to the kind of integer it represents
118 int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
120 // Map from floating variable to the kind of float it represents
121 float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
123 // For region variables.
124 region_vars: RegionVarBindings<'a, 'gcx, 'tcx>,
126 pub parameter_environment: ty::ParameterEnvironment<'gcx>,
128 /// Caches the results of trait selection. This cache is used
129 /// for things that have to do with the parameters in scope.
130 pub selection_cache: traits::SelectionCache<'tcx>,
132 /// Caches the results of trait evaluation.
133 pub evaluation_cache: traits::EvaluationCache<'tcx>,
135 // the set of predicates on which errors have been reported, to
136 // avoid reporting the same error twice.
137 pub reported_trait_errors: RefCell<FnvHashSet<traits::TraitErrorKey<'tcx>>>,
139 // This is a temporary field used for toggling on normalization in the inference context,
140 // as we move towards the approach described here:
141 // https://internals.rust-lang.org/t/flattening-the-contexts-for-fun-and-profit/2293
142 // At a point sometime in the future normalization will be done by the typing context
146 // Sadly, the behavior of projection varies a bit depending on the
147 // stage of compilation. The specifics are given in the
148 // documentation for `Reveal`.
149 projection_mode: Reveal,
151 // When an error occurs, we want to avoid reporting "derived"
152 // errors that are due to this original failure. Normally, we
153 // handle this with the `err_count_on_creation` count, which
154 // basically just tracks how many errors were reported when we
155 // started type-checking a fn and checks to see if any new errors
156 // have been reported since then. Not great, but it works.
158 // However, when errors originated in other passes -- notably
159 // resolve -- this heuristic breaks down. Therefore, we have this
160 // auxiliary flag that one can set whenever one creates a
161 // type-error that is due to an error in a prior pass.
163 // Don't read this flag directly, call `is_tainted_by_errors()`
164 // and `set_tainted_by_errors()`.
165 tainted_by_errors_flag: Cell<bool>,
167 // Track how many errors were reported when this infcx is created.
168 // If the number of errors increases, that's also a sign (line
169 // `tained_by_errors`) to avoid reporting certain kinds of errors.
170 err_count_on_creation: usize,
172 // This flag is used for debugging, and is set to true if there are
173 // any obligations set during the current snapshot. In that case, the
174 // snapshot can't be rolled back.
175 pub obligations_in_snapshot: Cell<bool>,
178 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
179 /// region that each late-bound region was replaced with.
180 pub type SkolemizationMap<'tcx> = FnvHashMap<ty::BoundRegion, &'tcx ty::Region>;
182 /// Why did we require that the two types be related?
184 /// See `error_reporting.rs` for more details
185 #[derive(Clone, Copy, Debug)]
186 pub enum TypeOrigin {
187 // Not yet categorized in a better way
190 // Checking that method of impl is compatible with trait
191 MethodCompatCheck(Span),
193 // Checking that this expression can be assigned where it needs to be
194 // FIXME(eddyb) #11161 is the original Expr required?
195 ExprAssignable(Span),
197 // Relating trait type parameters to those found in impl etc
198 RelateOutputImplTypes(Span),
200 // Computing common supertype in the arms of a match expression
201 MatchExpressionArm(Span, Span, hir::MatchSource),
203 // Computing common supertype in an if expression
206 // Computing common supertype of an if expression with no else counter-part
207 IfExpressionWithNoElse(Span),
209 // Computing common supertype in a range expression
210 RangeExpression(Span),
213 EquatePredicate(Span),
215 // `main` has wrong type
216 MainFunctionType(Span),
218 // `start` has wrong type
219 StartFunctionType(Span),
221 // intrinsic has wrong type
225 MethodReceiver(Span),
229 fn as_failure_str(&self) -> &'static str {
231 &TypeOrigin::Misc(_) |
232 &TypeOrigin::RelateOutputImplTypes(_) |
233 &TypeOrigin::ExprAssignable(_) => "mismatched types",
234 &TypeOrigin::MethodCompatCheck(_) => "method not compatible with trait",
235 &TypeOrigin::MatchExpressionArm(_, _, source) => match source {
236 hir::MatchSource::IfLetDesugar{..} => "`if let` arms have incompatible types",
237 _ => "match arms have incompatible types",
239 &TypeOrigin::IfExpression(_) => "if and else have incompatible types",
240 &TypeOrigin::IfExpressionWithNoElse(_) => "if may be missing an else clause",
241 &TypeOrigin::RangeExpression(_) => "start and end of range have incompatible types",
242 &TypeOrigin::EquatePredicate(_) => "equality predicate not satisfied",
243 &TypeOrigin::MainFunctionType(_) => "main function has wrong type",
244 &TypeOrigin::StartFunctionType(_) => "start function has wrong type",
245 &TypeOrigin::IntrinsicType(_) => "intrinsic has wrong type",
246 &TypeOrigin::MethodReceiver(_) => "mismatched method receiver",
250 fn as_requirement_str(&self) -> &'static str {
252 &TypeOrigin::Misc(_) => "types are compatible",
253 &TypeOrigin::MethodCompatCheck(_) => "method type is compatible with trait",
254 &TypeOrigin::ExprAssignable(_) => "expression is assignable",
255 &TypeOrigin::RelateOutputImplTypes(_) => {
256 "trait type parameters matches those specified on the impl"
258 &TypeOrigin::MatchExpressionArm(_, _, _) => "match arms have compatible types",
259 &TypeOrigin::IfExpression(_) => "if and else have compatible types",
260 &TypeOrigin::IfExpressionWithNoElse(_) => "if missing an else returns ()",
261 &TypeOrigin::RangeExpression(_) => "start and end of range have compatible types",
262 &TypeOrigin::EquatePredicate(_) => "equality where clause is satisfied",
263 &TypeOrigin::MainFunctionType(_) => "`main` function has the correct type",
264 &TypeOrigin::StartFunctionType(_) => "`start` function has the correct type",
265 &TypeOrigin::IntrinsicType(_) => "intrinsic has the correct type",
266 &TypeOrigin::MethodReceiver(_) => "method receiver has the correct type",
271 /// See `error_reporting.rs` for more details
272 #[derive(Clone, Debug)]
273 pub enum ValuePairs<'tcx> {
274 Types(ExpectedFound<Ty<'tcx>>),
275 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
276 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
279 /// The trace designates the path through inference that we took to
280 /// encounter an error or subtyping constraint.
282 /// See `error_reporting.rs` for more details.
284 pub struct TypeTrace<'tcx> {
286 values: ValuePairs<'tcx>,
289 /// The origin of a `r1 <= r2` constraint.
291 /// See `error_reporting.rs` for more details
292 #[derive(Clone, Debug)]
293 pub enum SubregionOrigin<'tcx> {
294 // Arose from a subtyping relation
295 Subtype(TypeTrace<'tcx>),
297 // Stack-allocated closures cannot outlive innermost loop
298 // or function so as to ensure we only require finite stack
299 InfStackClosure(Span),
301 // Invocation of closure must be within its lifetime
304 // Dereference of reference must be within its lifetime
307 // Closure bound must not outlive captured free variables
308 FreeVariable(Span, ast::NodeId),
310 // Index into slice must be within its lifetime
313 // When casting `&'a T` to an `&'b Trait` object,
314 // relating `'a` to `'b`
315 RelateObjectBound(Span),
317 // Some type parameter was instantiated with the given type,
318 // and that type must outlive some region.
319 RelateParamBound(Span, Ty<'tcx>),
321 // The given region parameter was instantiated with a region
322 // that must outlive some other region.
323 RelateRegionParamBound(Span),
325 // A bound placed on type parameters that states that must outlive
326 // the moment of their instantiation.
327 RelateDefaultParamBound(Span, Ty<'tcx>),
329 // Creating a pointer `b` to contents of another reference
332 // Creating a pointer `b` to contents of an upvar
333 ReborrowUpvar(Span, ty::UpvarId),
335 // Data with type `Ty<'tcx>` was borrowed
336 DataBorrowed(Ty<'tcx>, Span),
338 // (&'a &'b T) where a >= b
339 ReferenceOutlivesReferent(Ty<'tcx>, Span),
341 // Type or region parameters must be in scope.
342 ParameterInScope(ParameterOrigin, Span),
344 // The type T of an expression E must outlive the lifetime for E.
345 ExprTypeIsNotInScope(Ty<'tcx>, Span),
347 // A `ref b` whose region does not enclose the decl site
348 BindingTypeIsNotValidAtDecl(Span),
350 // Regions appearing in a method receiver must outlive method call
353 // Regions appearing in a function argument must outlive func call
356 // Region in return type of invoked fn must enclose call
359 // Operands must be in scope
362 // Region resulting from a `&` expr must enclose the `&` expr
365 // An auto-borrow that does not enclose the expr where it occurs
368 // Region constraint arriving from destructor safety
369 SafeDestructor(Span),
372 /// Places that type/region parameters can appear.
373 #[derive(Clone, Copy, Debug)]
374 pub enum ParameterOrigin {
376 MethodCall, // foo.bar() <-- parameters on impl providing bar()
377 OverloadedOperator, // a + b when overloaded
378 OverloadedDeref, // *a when overloaded
381 /// Times when we replace late-bound regions with variables:
382 #[derive(Clone, Copy, Debug)]
383 pub enum LateBoundRegionConversionTime {
384 /// when a fn is called
387 /// when two higher-ranked types are compared
390 /// when projecting an associated type
391 AssocTypeProjection(ast::Name),
394 /// Reasons to create a region inference variable
396 /// See `error_reporting.rs` for more details
397 #[derive(Clone, Debug)]
398 pub enum RegionVariableOrigin {
399 // Region variables created for ill-categorized reasons,
400 // mostly indicates places in need of refactoring
403 // Regions created by a `&P` or `[...]` pattern
406 // Regions created by `&` operator
409 // Regions created as part of an autoref of a method receiver
412 // Regions created as part of an automatic coercion
415 // Region variables created as the values for early-bound regions
416 EarlyBoundRegion(Span, ast::Name),
418 // Region variables created for bound regions
419 // in a function or method that is called
420 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
422 UpvarRegion(ty::UpvarId, Span),
424 BoundRegionInCoherence(ast::Name),
427 #[derive(Copy, Clone, Debug)]
428 pub enum FixupError {
429 UnresolvedIntTy(IntVid),
430 UnresolvedFloatTy(FloatVid),
434 impl fmt::Display for FixupError {
435 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
436 use self::FixupError::*;
439 UnresolvedIntTy(_) => {
440 write!(f, "cannot determine the type of this integer; \
441 add a suffix to specify the type explicitly")
443 UnresolvedFloatTy(_) => {
444 write!(f, "cannot determine the type of this number; \
445 add a suffix to specify the type explicitly")
447 UnresolvedTy(_) => write!(f, "unconstrained type")
452 /// Helper type of a temporary returned by tcx.infer_ctxt(...).
453 /// Necessary because we can't write the following bound:
454 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(InferCtxt<'b, 'gcx, 'tcx>).
455 pub struct InferCtxtBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
456 global_tcx: TyCtxt<'a, 'gcx, 'gcx>,
457 arenas: ty::CtxtArenas<'tcx>,
458 tables: Option<RefCell<ty::Tables<'tcx>>>,
459 param_env: Option<ty::ParameterEnvironment<'gcx>>,
460 projection_mode: Reveal,
464 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'gcx> {
465 pub fn infer_ctxt(self,
466 tables: Option<ty::Tables<'tcx>>,
467 param_env: Option<ty::ParameterEnvironment<'gcx>>,
468 projection_mode: Reveal)
469 -> InferCtxtBuilder<'a, 'gcx, 'tcx> {
472 arenas: ty::CtxtArenas::new(),
473 tables: tables.map(RefCell::new),
474 param_env: param_env,
475 projection_mode: projection_mode,
480 pub fn normalizing_infer_ctxt(self, projection_mode: Reveal)
481 -> InferCtxtBuilder<'a, 'gcx, 'tcx> {
484 arenas: ty::CtxtArenas::new(),
487 projection_mode: projection_mode,
492 /// Fake InferCtxt with the global tcx. Used by pre-MIR borrowck
493 /// for MemCategorizationContext/ExprUseVisitor.
494 /// If any inference functionality is used, ICEs will occur.
495 pub fn borrowck_fake_infer_ctxt(self, param_env: ty::ParameterEnvironment<'gcx>)
496 -> InferCtxt<'a, 'gcx, 'gcx> {
499 tables: InferTables::Global(&self.tables),
500 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
501 int_unification_table: RefCell::new(UnificationTable::new()),
502 float_unification_table: RefCell::new(UnificationTable::new()),
503 region_vars: RegionVarBindings::new(self),
504 parameter_environment: param_env,
505 selection_cache: traits::SelectionCache::new(),
506 evaluation_cache: traits::EvaluationCache::new(),
507 projection_cache: RefCell::new(traits::ProjectionCache::new()),
508 reported_trait_errors: RefCell::new(FnvHashSet()),
510 projection_mode: Reveal::NotSpecializable,
511 tainted_by_errors_flag: Cell::new(false),
512 err_count_on_creation: self.sess.err_count(),
513 obligations_in_snapshot: Cell::new(false),
518 impl<'a, 'gcx, 'tcx> InferCtxtBuilder<'a, 'gcx, 'tcx> {
519 pub fn enter<F, R>(&'tcx mut self, f: F) -> R
520 where F: for<'b> FnOnce(InferCtxt<'b, 'gcx, 'tcx>) -> R
522 let InferCtxtBuilder {
530 let tables = if let Some(ref tables) = *tables {
531 InferTables::Local(tables)
533 InferTables::Global(&global_tcx.tables)
535 let param_env = param_env.take().unwrap_or_else(|| {
536 global_tcx.empty_parameter_environment()
538 global_tcx.enter_local(arenas, |tcx| f(InferCtxt {
541 projection_cache: RefCell::new(traits::ProjectionCache::new()),
542 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
543 int_unification_table: RefCell::new(UnificationTable::new()),
544 float_unification_table: RefCell::new(UnificationTable::new()),
545 region_vars: RegionVarBindings::new(tcx),
546 parameter_environment: param_env,
547 selection_cache: traits::SelectionCache::new(),
548 evaluation_cache: traits::EvaluationCache::new(),
549 reported_trait_errors: RefCell::new(FnvHashSet()),
550 normalize: normalize,
551 projection_mode: projection_mode,
552 tainted_by_errors_flag: Cell::new(false),
553 err_count_on_creation: tcx.sess.err_count(),
554 obligations_in_snapshot: Cell::new(false),
559 impl<T> ExpectedFound<T> {
560 fn new(a_is_expected: bool, a: T, b: T) -> Self {
562 ExpectedFound {expected: a, found: b}
564 ExpectedFound {expected: b, found: a}
569 impl<'tcx, T> InferOk<'tcx, T> {
570 pub fn unit(self) -> InferOk<'tcx, ()> {
571 InferOk { value: (), obligations: self.obligations }
575 #[must_use = "once you start a snapshot, you should always consume it"]
576 pub struct CombinedSnapshot {
577 projection_cache_snapshot: traits::ProjectionCacheSnapshot,
578 type_snapshot: type_variable::Snapshot,
579 int_snapshot: unify::Snapshot<ty::IntVid>,
580 float_snapshot: unify::Snapshot<ty::FloatVid>,
581 region_vars_snapshot: RegionSnapshot,
582 obligations_in_snapshot: bool,
585 /// Helper trait for shortening the lifetimes inside a
586 /// value for post-type-checking normalization.
587 pub trait TransNormalize<'gcx>: TypeFoldable<'gcx> {
588 fn trans_normalize<'a, 'tcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>) -> Self;
591 macro_rules! items { ($($item:item)+) => ($($item)+) }
592 macro_rules! impl_trans_normalize {
593 ($lt_gcx:tt, $($ty:ty),+) => {
594 items!($(impl<$lt_gcx> TransNormalize<$lt_gcx> for $ty {
595 fn trans_normalize<'a, 'tcx>(&self,
596 infcx: &InferCtxt<'a, $lt_gcx, 'tcx>)
598 infcx.normalize_projections_in(self)
604 impl_trans_normalize!('gcx,
608 &'gcx ty::BareFnTy<'gcx>,
609 ty::ClosureSubsts<'gcx>,
610 ty::PolyTraitRef<'gcx>
613 impl<'gcx> TransNormalize<'gcx> for LvalueTy<'gcx> {
614 fn trans_normalize<'a, 'tcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>) -> Self {
616 LvalueTy::Ty { ty } => LvalueTy::Ty { ty: ty.trans_normalize(infcx) },
617 LvalueTy::Downcast { adt_def, substs, variant_index } => {
620 substs: substs.trans_normalize(infcx),
621 variant_index: variant_index
628 // NOTE: Callable from trans only!
629 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
630 pub fn normalize_associated_type<T>(self, value: &T) -> T
631 where T: TransNormalize<'tcx>
633 debug!("normalize_associated_type(t={:?})", value);
635 let value = self.erase_regions(value);
637 if !value.has_projection_types() {
641 self.infer_ctxt(None, None, Reveal::All).enter(|infcx| {
642 value.trans_normalize(&infcx)
646 pub fn normalize_associated_type_in_env<T>(
647 self, value: &T, env: &'a ty::ParameterEnvironment<'tcx>
649 where T: TransNormalize<'tcx>
651 debug!("normalize_associated_type_in_env(t={:?})", value);
653 let value = self.erase_regions(value);
655 if !value.has_projection_types() {
659 self.infer_ctxt(None, Some(env.clone()), Reveal::All).enter(|infcx| {
660 value.trans_normalize(&infcx)
665 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
666 fn normalize_projections_in<T>(&self, value: &T) -> T::Lifted
667 where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
669 let mut selcx = traits::SelectionContext::new(self);
670 let cause = traits::ObligationCause::dummy();
671 let traits::Normalized { value: result, obligations } =
672 traits::normalize(&mut selcx, cause, value);
674 debug!("normalize_projections_in: result={:?} obligations={:?}",
675 result, obligations);
677 let mut fulfill_cx = traits::FulfillmentContext::new();
679 for obligation in obligations {
680 fulfill_cx.register_predicate_obligation(self, obligation);
683 self.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &result)
686 pub fn drain_fulfillment_cx_or_panic<T>(&self,
688 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
691 where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
693 debug!("drain_fulfillment_cx_or_panic()");
695 let when = "resolving bounds after type-checking";
696 let v = match self.drain_fulfillment_cx(fulfill_cx, result) {
699 span_bug!(span, "Encountered errors `{:?}` {}", errors, when);
703 match self.tcx.lift_to_global(&v) {
706 span_bug!(span, "Uninferred types/regions in `{:?}` {}", v, when);
711 /// Finishes processes any obligations that remain in the fulfillment
712 /// context, and then "freshens" and returns `result`. This is
713 /// primarily used during normalization and other cases where
714 /// processing the obligations in `fulfill_cx` may cause type
715 /// inference variables that appear in `result` to be unified, and
716 /// hence we need to process those obligations to get the complete
717 /// picture of the type.
718 pub fn drain_fulfillment_cx<T>(&self,
719 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
721 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
722 where T : TypeFoldable<'tcx>
724 debug!("drain_fulfillment_cx(result={:?})",
727 // In principle, we only need to do this so long as `result`
728 // contains unbound type parameters. It could be a slight
729 // optimization to stop iterating early.
730 fulfill_cx.select_all_or_error(self)?;
732 let result = self.resolve_type_vars_if_possible(result);
733 Ok(self.tcx.erase_regions(&result))
736 pub fn projection_mode(&self) -> Reveal {
740 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
741 t.fold_with(&mut self.freshener())
744 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
746 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
751 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'gcx, 'tcx> {
752 freshen::TypeFreshener::new(self)
755 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
756 use ty::error::UnconstrainedNumeric::Neither;
757 use ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
759 ty::TyInfer(ty::IntVar(vid)) => {
760 if self.int_unification_table.borrow_mut().has_value(vid) {
766 ty::TyInfer(ty::FloatVar(vid)) => {
767 if self.float_unification_table.borrow_mut().has_value(vid) {
777 /// Returns a type variable's default fallback if any exists. A default
778 /// must be attached to the variable when created, if it is created
779 /// without a default, this will return None.
781 /// This code does not apply to integral or floating point variables,
782 /// only to use declared defaults.
784 /// See `new_ty_var_with_default` to create a type variable with a default.
785 /// See `type_variable::Default` for details about what a default entails.
786 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
788 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
793 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
794 let mut variables = Vec::new();
796 let unbound_ty_vars = self.type_variables
798 .unsolved_variables()
800 .map(|t| self.tcx.mk_var(t));
802 let unbound_int_vars = self.int_unification_table
804 .unsolved_variables()
806 .map(|v| self.tcx.mk_int_var(v));
808 let unbound_float_vars = self.float_unification_table
810 .unsolved_variables()
812 .map(|v| self.tcx.mk_float_var(v));
814 variables.extend(unbound_ty_vars);
815 variables.extend(unbound_int_vars);
816 variables.extend(unbound_float_vars);
821 fn combine_fields(&'a self, trace: TypeTrace<'tcx>)
822 -> CombineFields<'a, 'gcx, 'tcx> {
827 obligations: PredicateObligations::new(),
831 pub fn equate<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
832 -> InferResult<'tcx, T>
833 where T: Relate<'tcx>
835 let mut fields = self.combine_fields(trace);
836 let result = fields.equate(a_is_expected).relate(a, b);
837 result.map(move |t| InferOk { value: t, obligations: fields.obligations })
840 pub fn sub<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
841 -> InferResult<'tcx, T>
842 where T: Relate<'tcx>
844 let mut fields = self.combine_fields(trace);
845 let result = fields.sub(a_is_expected).relate(a, b);
846 result.map(move |t| InferOk { value: t, obligations: fields.obligations })
849 pub fn lub<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
850 -> InferResult<'tcx, T>
851 where T: Relate<'tcx>
853 let mut fields = self.combine_fields(trace);
854 let result = fields.lub(a_is_expected).relate(a, b);
855 result.map(move |t| InferOk { value: t, obligations: fields.obligations })
858 pub fn glb<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
859 -> InferResult<'tcx, T>
860 where T: Relate<'tcx>
862 let mut fields = self.combine_fields(trace);
863 let result = fields.glb(a_is_expected).relate(a, b);
864 result.map(move |t| InferOk { value: t, obligations: fields.obligations })
867 fn start_snapshot(&self) -> CombinedSnapshot {
868 debug!("start_snapshot()");
870 let obligations_in_snapshot = self.obligations_in_snapshot.get();
871 self.obligations_in_snapshot.set(false);
874 projection_cache_snapshot: self.projection_cache.borrow_mut().snapshot(),
875 type_snapshot: self.type_variables.borrow_mut().snapshot(),
876 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
877 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
878 region_vars_snapshot: self.region_vars.start_snapshot(),
879 obligations_in_snapshot: obligations_in_snapshot,
883 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
884 debug!("rollback_to(cause={})", cause);
885 let CombinedSnapshot { projection_cache_snapshot,
889 region_vars_snapshot,
890 obligations_in_snapshot } = snapshot;
892 assert!(!self.obligations_in_snapshot.get());
893 self.obligations_in_snapshot.set(obligations_in_snapshot);
895 self.projection_cache
897 .rollback_to(projection_cache_snapshot);
900 .rollback_to(type_snapshot);
901 self.int_unification_table
903 .rollback_to(int_snapshot);
904 self.float_unification_table
906 .rollback_to(float_snapshot);
908 .rollback_to(region_vars_snapshot);
911 fn commit_from(&self, snapshot: CombinedSnapshot) {
912 debug!("commit_from()");
913 let CombinedSnapshot { projection_cache_snapshot,
917 region_vars_snapshot,
918 obligations_in_snapshot } = snapshot;
920 self.obligations_in_snapshot.set(obligations_in_snapshot);
922 self.projection_cache
924 .commit(projection_cache_snapshot);
927 .commit(type_snapshot);
928 self.int_unification_table
930 .commit(int_snapshot);
931 self.float_unification_table
933 .commit(float_snapshot);
935 .commit(region_vars_snapshot);
938 /// Execute `f` and commit the bindings
939 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
943 let snapshot = self.start_snapshot();
945 self.commit_from(snapshot);
949 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
950 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
951 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
953 debug!("commit_if_ok()");
954 let snapshot = self.start_snapshot();
955 let r = f(&snapshot);
956 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
958 Ok(_) => { self.commit_from(snapshot); }
959 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
964 // Execute `f` in a snapshot, and commit the bindings it creates
965 pub fn in_snapshot<T, F>(&self, f: F) -> T where
966 F: FnOnce(&CombinedSnapshot) -> T
968 debug!("in_snapshot()");
969 let snapshot = self.start_snapshot();
970 let r = f(&snapshot);
971 self.commit_from(snapshot);
975 /// Execute `f` and commit only the region bindings if successful.
976 /// The function f must be very careful not to leak any non-region
977 /// variables that get created.
978 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
979 F: FnOnce() -> Result<T, E>
981 debug!("commit_regions_if_ok()");
982 let CombinedSnapshot { projection_cache_snapshot,
986 region_vars_snapshot,
987 obligations_in_snapshot } = self.start_snapshot();
989 let r = self.commit_if_ok(|_| f());
991 debug!("commit_regions_if_ok: rolling back everything but regions");
993 assert!(!self.obligations_in_snapshot.get());
994 self.obligations_in_snapshot.set(obligations_in_snapshot);
996 // Roll back any non-region bindings - they should be resolved
997 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
998 self.projection_cache
1000 .rollback_to(projection_cache_snapshot);
1003 .rollback_to(type_snapshot);
1004 self.int_unification_table
1006 .rollback_to(int_snapshot);
1007 self.float_unification_table
1009 .rollback_to(float_snapshot);
1011 // Commit region vars that may escape through resolved types.
1013 .commit(region_vars_snapshot);
1018 /// Execute `f` then unroll any bindings it creates
1019 pub fn probe<R, F>(&self, f: F) -> R where
1020 F: FnOnce(&CombinedSnapshot) -> R,
1023 let snapshot = self.start_snapshot();
1024 let r = f(&snapshot);
1025 self.rollback_to("probe", snapshot);
1029 pub fn add_given(&self,
1030 sub: ty::FreeRegion,
1033 self.region_vars.add_given(sub, sup);
1036 pub fn sub_types(&self,
1037 a_is_expected: bool,
1041 -> InferResult<'tcx, ()>
1043 debug!("sub_types({:?} <: {:?})", a, b);
1044 self.commit_if_ok(|_| {
1045 let trace = TypeTrace::types(origin, a_is_expected, a, b);
1046 self.sub(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
1050 pub fn can_sub_types(&self,
1056 let origin = TypeOrigin::Misc(syntax_pos::DUMMY_SP);
1057 let trace = TypeTrace::types(origin, true, a, b);
1058 self.sub(true, trace, &a, &b).map(|_| ())
1062 pub fn eq_types(&self,
1063 a_is_expected: bool,
1067 -> InferResult<'tcx, ()>
1069 self.commit_if_ok(|_| {
1070 let trace = TypeTrace::types(origin, a_is_expected, a, b);
1071 self.equate(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
1075 pub fn eq_trait_refs(&self,
1076 a_is_expected: bool,
1078 a: ty::TraitRef<'tcx>,
1079 b: ty::TraitRef<'tcx>)
1080 -> InferResult<'tcx, ()>
1082 debug!("eq_trait_refs({:?} = {:?})", a, b);
1083 self.commit_if_ok(|_| {
1084 let trace = TypeTrace {
1086 values: TraitRefs(ExpectedFound::new(a_is_expected, a, b))
1088 self.equate(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
1092 pub fn eq_impl_headers(&self,
1093 a_is_expected: bool,
1095 a: &ty::ImplHeader<'tcx>,
1096 b: &ty::ImplHeader<'tcx>)
1097 -> InferResult<'tcx, ()>
1099 debug!("eq_impl_header({:?} = {:?})", a, b);
1100 match (a.trait_ref, b.trait_ref) {
1101 (Some(a_ref), Some(b_ref)) => self.eq_trait_refs(a_is_expected, origin, a_ref, b_ref),
1102 (None, None) => self.eq_types(a_is_expected, origin, a.self_ty, b.self_ty),
1103 _ => bug!("mk_eq_impl_headers given mismatched impl kinds"),
1107 pub fn sub_poly_trait_refs(&self,
1108 a_is_expected: bool,
1110 a: ty::PolyTraitRef<'tcx>,
1111 b: ty::PolyTraitRef<'tcx>)
1112 -> InferResult<'tcx, ()>
1114 debug!("sub_poly_trait_refs({:?} <: {:?})", a, b);
1115 self.commit_if_ok(|_| {
1116 let trace = TypeTrace {
1118 values: PolyTraitRefs(ExpectedFound::new(a_is_expected, a, b))
1120 self.sub(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
1124 pub fn sub_regions(&self,
1125 origin: SubregionOrigin<'tcx>,
1126 a: &'tcx ty::Region,
1127 b: &'tcx ty::Region) {
1128 debug!("sub_regions({:?} <: {:?})", a, b);
1129 self.region_vars.make_subregion(origin, a, b);
1132 pub fn equality_predicate(&self,
1134 predicate: &ty::PolyEquatePredicate<'tcx>)
1135 -> InferResult<'tcx, ()>
1137 self.commit_if_ok(|snapshot| {
1138 let (ty::EquatePredicate(a, b), skol_map) =
1139 self.skolemize_late_bound_regions(predicate, snapshot);
1140 let origin = TypeOrigin::EquatePredicate(span);
1141 let eqty_ok = self.eq_types(false, origin, a, b)?;
1142 self.leak_check(false, span, &skol_map, snapshot)?;
1143 self.pop_skolemized(skol_map, snapshot);
1148 pub fn region_outlives_predicate(&self,
1150 predicate: &ty::PolyRegionOutlivesPredicate<'tcx>)
1153 self.commit_if_ok(|snapshot| {
1154 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
1155 self.skolemize_late_bound_regions(predicate, snapshot);
1156 let origin = RelateRegionParamBound(span);
1157 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
1158 self.leak_check(false, span, &skol_map, snapshot)?;
1159 Ok(self.pop_skolemized(skol_map, snapshot))
1163 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
1166 .new_var(diverging, None)
1169 pub fn next_ty_var(&self) -> Ty<'tcx> {
1170 self.tcx.mk_var(self.next_ty_var_id(false))
1173 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
1174 self.tcx.mk_var(self.next_ty_var_id(true))
1177 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
1178 (0..n).map(|_i| self.next_ty_var()).collect()
1181 pub fn next_int_var_id(&self) -> IntVid {
1182 self.int_unification_table
1187 pub fn next_float_var_id(&self) -> FloatVid {
1188 self.float_unification_table
1193 pub fn next_region_var(&self, origin: RegionVariableOrigin)
1194 -> &'tcx ty::Region {
1195 self.tcx.mk_region(ty::ReVar(self.region_vars.new_region_var(origin)))
1198 /// Create a region inference variable for the given
1199 /// region parameter definition.
1200 pub fn region_var_for_def(&self,
1202 def: &ty::RegionParameterDef)
1203 -> &'tcx ty::Region {
1204 self.next_region_var(EarlyBoundRegion(span, def.name))
1207 /// Create a type inference variable for the given
1208 /// type parameter definition. The substitutions are
1209 /// for actual parameters that may be referred to by
1210 /// the default of this type parameter, if it exists.
1211 /// E.g. `struct Foo<A, B, C = (A, B)>(...);` when
1212 /// used in a path such as `Foo::<T, U>::new()` will
1213 /// use an inference variable for `C` with `[T, U]`
1214 /// as the substitutions for the default, `(T, U)`.
1215 pub fn type_var_for_def(&self,
1217 def: &ty::TypeParameterDef<'tcx>,
1218 substs: &Substs<'tcx>)
1220 let default = def.default.map(|default| {
1221 type_variable::Default {
1222 ty: default.subst_spanned(self.tcx, substs, Some(span)),
1224 def_id: def.default_def_id
1229 let ty_var_id = self.type_variables
1231 .new_var(false, default);
1233 self.tcx.mk_var(ty_var_id)
1236 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1237 /// type/region parameter to a fresh inference variable.
1238 pub fn fresh_substs_for_item(&self,
1241 -> &'tcx Substs<'tcx> {
1242 Substs::for_item(self.tcx, def_id, |def, _| {
1243 self.region_var_for_def(span, def)
1245 self.type_var_for_def(span, def, substs)
1249 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> &'tcx ty::Region {
1250 self.region_vars.new_bound(debruijn)
1253 /// Apply `adjustment` to the type of `expr`
1254 pub fn adjust_expr_ty(&self,
1256 adjustment: Option<&adjustment::AutoAdjustment<'tcx>>)
1259 let raw_ty = self.expr_ty(expr);
1260 let raw_ty = self.shallow_resolve(raw_ty);
1261 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1262 raw_ty.adjust(self.tcx,
1266 |method_call| self.tables
1270 .map(|method| resolve_ty(method.ty)))
1273 /// True if errors have been reported since this infcx was
1274 /// created. This is sometimes used as a heuristic to skip
1275 /// reporting errors that often occur as a result of earlier
1276 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1277 /// inference variables, regionck errors).
1278 pub fn is_tainted_by_errors(&self) -> bool {
1279 debug!("is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1280 tainted_by_errors_flag={})",
1281 self.tcx.sess.err_count(),
1282 self.err_count_on_creation,
1283 self.tainted_by_errors_flag.get());
1285 if self.tcx.sess.err_count() > self.err_count_on_creation {
1286 return true; // errors reported since this infcx was made
1288 self.tainted_by_errors_flag.get()
1291 /// Set the "tainted by errors" flag to true. We call this when we
1292 /// observe an error from a prior pass.
1293 pub fn set_tainted_by_errors(&self) {
1294 debug!("set_tainted_by_errors()");
1295 self.tainted_by_errors_flag.set(true)
1298 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1299 match self.tables.borrow().node_types.get(&id) {
1302 None if self.is_tainted_by_errors() =>
1305 bug!("no type for node {}: {} in fcx",
1306 id, self.tcx.map.node_to_string(id));
1311 pub fn expr_ty(&self, ex: &hir::Expr) -> Ty<'tcx> {
1312 match self.tables.borrow().node_types.get(&ex.id) {
1315 bug!("no type for expr in fcx");
1320 pub fn resolve_regions_and_report_errors(&self,
1321 free_regions: &FreeRegionMap,
1322 subject_node_id: ast::NodeId) {
1323 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1324 if !self.is_tainted_by_errors() {
1325 // As a heuristic, just skip reporting region errors
1326 // altogether if other errors have been reported while
1327 // this infcx was in use. This is totally hokey but
1328 // otherwise we have a hard time separating legit region
1329 // errors from silly ones.
1330 self.report_region_errors(&errors); // see error_reporting.rs
1334 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1335 self.resolve_type_vars_if_possible(&t).to_string()
1338 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1339 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1340 format!("({})", tstrs.join(", "))
1343 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1344 self.resolve_type_vars_if_possible(t).to_string()
1347 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1349 ty::TyInfer(ty::TyVar(v)) => {
1350 // Not entirely obvious: if `typ` is a type variable,
1351 // it can be resolved to an int/float variable, which
1352 // can then be recursively resolved, hence the
1353 // recursion. Note though that we prevent type
1354 // variables from unifying to other type variables
1355 // directly (though they may be embedded
1356 // structurally), and we prevent cycles in any case,
1357 // so this recursion should always be of very limited
1359 self.type_variables.borrow_mut()
1361 .map(|t| self.shallow_resolve(t))
1365 ty::TyInfer(ty::IntVar(v)) => {
1366 self.int_unification_table
1369 .map(|v| v.to_type(self.tcx))
1373 ty::TyInfer(ty::FloatVar(v)) => {
1374 self.float_unification_table
1377 .map(|v| v.to_type(self.tcx))
1387 pub fn resolve_type_vars_if_possible<T>(&self, value: &T) -> T
1388 where T: TypeFoldable<'tcx>
1391 * Where possible, replaces type/int/float variables in
1392 * `value` with their final value. Note that region variables
1393 * are unaffected. If a type variable has not been unified, it
1394 * is left as is. This is an idempotent operation that does
1395 * not affect inference state in any way and so you can do it
1399 if !value.needs_infer() {
1400 return value.clone(); // avoid duplicated subst-folding
1402 let mut r = resolve::OpportunisticTypeResolver::new(self);
1403 value.fold_with(&mut r)
1406 pub fn resolve_type_and_region_vars_if_possible<T>(&self, value: &T) -> T
1407 where T: TypeFoldable<'tcx>
1409 let mut r = resolve::OpportunisticTypeAndRegionResolver::new(self);
1410 value.fold_with(&mut r)
1413 /// Resolves all type variables in `t` and then, if any were left
1414 /// unresolved, substitutes an error type. This is used after the
1415 /// main checking when doing a second pass before writeback. The
1416 /// justification is that writeback will produce an error for
1417 /// these unconstrained type variables.
1418 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1419 let ty = self.resolve_type_vars_if_possible(t);
1420 if ty.references_error() || ty.is_ty_var() {
1421 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1428 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1430 * Attempts to resolve all type/region variables in
1431 * `value`. Region inference must have been run already (e.g.,
1432 * by calling `resolve_regions_and_report_errors`). If some
1433 * variable was never unified, an `Err` results.
1435 * This method is idempotent, but it not typically not invoked
1436 * except during the writeback phase.
1439 resolve::fully_resolve(self, value)
1442 // [Note-Type-error-reporting]
1443 // An invariant is that anytime the expected or actual type is TyError (the special
1444 // error type, meaning that an error occurred when typechecking this expression),
1445 // this is a derived error. The error cascaded from another error (that was already
1446 // reported), so it's not useful to display it to the user.
1447 // The following methods implement this logic.
1448 // They check if either the actual or expected type is TyError, and don't print the error
1449 // in this case. The typechecker should only ever report type errors involving mismatched
1450 // types using one of these methods, and should not call span_err directly for such
1453 pub fn type_error_message<M>(&self,
1456 actual_ty: Ty<'tcx>)
1457 where M: FnOnce(String) -> String,
1459 self.type_error_struct(sp, mk_msg, actual_ty).emit();
1462 // FIXME: this results in errors without an error code. Deprecate?
1463 pub fn type_error_struct<M>(&self,
1466 actual_ty: Ty<'tcx>)
1467 -> DiagnosticBuilder<'tcx>
1468 where M: FnOnce(String) -> String,
1470 self.type_error_struct_with_diag(sp, |actual_ty| {
1471 self.tcx.sess.struct_span_err(sp, &mk_msg(actual_ty))
1475 pub fn type_error_struct_with_diag<M>(&self,
1478 actual_ty: Ty<'tcx>)
1479 -> DiagnosticBuilder<'tcx>
1480 where M: FnOnce(String) -> DiagnosticBuilder<'tcx>,
1482 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1483 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1485 // Don't report an error if actual type is TyError.
1486 if actual_ty.references_error() {
1487 return self.tcx.sess.diagnostic().struct_dummy();
1490 mk_diag(self.ty_to_string(actual_ty))
1493 pub fn report_mismatched_types(&self,
1497 err: TypeError<'tcx>) {
1498 let trace = TypeTrace {
1500 values: Types(ExpectedFound {
1505 self.report_and_explain_type_error(trace, &err).emit();
1508 pub fn report_conflicting_default_types(&self,
1510 expected: type_variable::Default<'tcx>,
1511 actual: type_variable::Default<'tcx>) {
1512 let trace = TypeTrace {
1513 origin: TypeOrigin::Misc(span),
1514 values: Types(ExpectedFound {
1515 expected: expected.ty,
1520 self.report_and_explain_type_error(
1522 &TypeError::TyParamDefaultMismatch(ExpectedFound {
1529 pub fn replace_late_bound_regions_with_fresh_var<T>(
1532 lbrct: LateBoundRegionConversionTime,
1533 value: &ty::Binder<T>)
1534 -> (T, FnvHashMap<ty::BoundRegion, &'tcx ty::Region>)
1535 where T : TypeFoldable<'tcx>
1537 self.tcx.replace_late_bound_regions(
1539 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1542 /// Given a higher-ranked projection predicate like:
1544 /// for<'a> <T as Fn<&'a u32>>::Output = &'a u32
1546 /// and a target trait-ref like:
1548 /// <T as Fn<&'x u32>>
1550 /// find a substitution `S` for the higher-ranked regions (here,
1551 /// `['a => 'x]`) such that the predicate matches the trait-ref,
1552 /// and then return the value (here, `&'a u32`) but with the
1553 /// substitution applied (hence, `&'x u32`).
1555 /// See `higher_ranked_match` in `higher_ranked/mod.rs` for more
1557 pub fn match_poly_projection_predicate(&self,
1559 match_a: ty::PolyProjectionPredicate<'tcx>,
1560 match_b: ty::TraitRef<'tcx>)
1561 -> InferResult<'tcx, HrMatchResult<Ty<'tcx>>>
1563 let span = origin.span();
1564 let match_trait_ref = match_a.skip_binder().projection_ty.trait_ref;
1565 let trace = TypeTrace {
1567 values: TraitRefs(ExpectedFound::new(true, match_trait_ref, match_b))
1570 let match_pair = match_a.map_bound(|p| (p.projection_ty.trait_ref, p.ty));
1571 let mut combine = self.combine_fields(trace);
1572 let result = combine.higher_ranked_match(span, &match_pair, &match_b, true)?;
1573 Ok(InferOk { value: result, obligations: combine.obligations })
1576 /// See `verify_generic_bound` method in `region_inference`
1577 pub fn verify_generic_bound(&self,
1578 origin: SubregionOrigin<'tcx>,
1579 kind: GenericKind<'tcx>,
1580 a: &'tcx ty::Region,
1581 bound: VerifyBound<'tcx>) {
1582 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1587 self.region_vars.verify_generic_bound(origin, kind, a, bound);
1590 pub fn can_equate<T>(&self, a: &T, b: &T) -> UnitResult<'tcx>
1591 where T: Relate<'tcx> + fmt::Debug
1593 debug!("can_equate({:?}, {:?})", a, b);
1595 // Gin up a dummy trace, since this won't be committed
1596 // anyhow. We should make this typetrace stuff more
1597 // generic so we don't have to do anything quite this
1599 self.equate(true, TypeTrace::dummy(self.tcx), a, b)
1603 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1604 let ty = self.node_type(id);
1605 self.resolve_type_vars_or_error(&ty)
1608 pub fn expr_ty_adjusted(&self, expr: &hir::Expr) -> McResult<Ty<'tcx>> {
1609 let ty = self.adjust_expr_ty(expr, self.tables.borrow().adjustments.get(&expr.id));
1610 self.resolve_type_vars_or_error(&ty)
1613 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1614 let ty = self.resolve_type_vars_if_possible(&ty);
1615 if let Some(ty) = self.tcx.lift_to_global(&ty) {
1616 // Even if the type may have no inference variables, during
1617 // type-checking closure types are in local tables only.
1618 let local_closures = match self.tables {
1619 InferTables::Local(_) => ty.has_closure_types(),
1620 InferTables::Global(_) => false
1622 if !local_closures {
1623 return ty.moves_by_default(self.tcx.global_tcx(), self.param_env(), span);
1627 // this can get called from typeck (by euv), and moves_by_default
1628 // rightly refuses to work with inference variables, but
1629 // moves_by_default has a cache, which we want to use in other
1631 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1634 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1635 -> Option<Ty<'tcx>> {
1640 .map(|method| method.ty)
1641 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1644 pub fn node_method_id(&self, method_call: ty::MethodCall)
1650 .map(|method| method.def_id)
1653 pub fn adjustments(&self) -> Ref<NodeMap<adjustment::AutoAdjustment<'tcx>>> {
1654 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1655 -> &'a NodeMap<adjustment::AutoAdjustment<'tcx>> {
1659 Ref::map(self.tables.borrow(), project_adjustments)
1662 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1663 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1666 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1667 self.tcx.region_maps.temporary_scope(rvalue_id)
1670 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture<'tcx>> {
1671 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1674 pub fn param_env(&self) -> &ty::ParameterEnvironment<'gcx> {
1675 &self.parameter_environment
1678 pub fn closure_kind(&self,
1680 -> Option<ty::ClosureKind>
1682 if def_id.is_local() {
1683 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1685 // During typeck, ALL closures are local. But afterwards,
1686 // during trans, we see closure ids from other traits.
1687 // That may require loading the closure data out of the
1689 Some(self.tcx.closure_kind(def_id))
1693 pub fn closure_type(&self,
1695 substs: ty::ClosureSubsts<'tcx>)
1696 -> ty::ClosureTy<'tcx>
1698 if let InferTables::Local(tables) = self.tables {
1699 if let Some(ty) = tables.borrow().closure_tys.get(&def_id) {
1700 return ty.subst(self.tcx, substs.func_substs);
1704 let closure_ty = self.tcx.closure_type(def_id, substs);
1706 let closure_ty = self.tcx.erase_regions(&closure_ty);
1708 if !closure_ty.has_projection_types() {
1712 self.normalize_projections_in(&closure_ty)
1719 impl<'a, 'gcx, 'tcx> TypeTrace<'tcx> {
1720 pub fn span(&self) -> Span {
1724 pub fn types(origin: TypeOrigin,
1725 a_is_expected: bool,
1728 -> TypeTrace<'tcx> {
1731 values: Types(ExpectedFound::new(a_is_expected, a, b))
1735 pub fn dummy(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> TypeTrace<'tcx> {
1737 origin: TypeOrigin::Misc(syntax_pos::DUMMY_SP),
1738 values: Types(ExpectedFound {
1739 expected: tcx.types.err,
1740 found: tcx.types.err,
1746 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1747 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1748 write!(f, "TypeTrace({:?})", self.origin)
1753 pub fn span(&self) -> Span {
1755 TypeOrigin::MethodCompatCheck(span) => span,
1756 TypeOrigin::ExprAssignable(span) => span,
1757 TypeOrigin::Misc(span) => span,
1758 TypeOrigin::RelateOutputImplTypes(span) => span,
1759 TypeOrigin::MatchExpressionArm(match_span, _, _) => match_span,
1760 TypeOrigin::IfExpression(span) => span,
1761 TypeOrigin::IfExpressionWithNoElse(span) => span,
1762 TypeOrigin::RangeExpression(span) => span,
1763 TypeOrigin::EquatePredicate(span) => span,
1764 TypeOrigin::MainFunctionType(span) => span,
1765 TypeOrigin::StartFunctionType(span) => span,
1766 TypeOrigin::IntrinsicType(span) => span,
1767 TypeOrigin::MethodReceiver(span) => span,
1772 impl<'tcx> SubregionOrigin<'tcx> {
1773 pub fn span(&self) -> Span {
1775 Subtype(ref a) => a.span(),
1776 InfStackClosure(a) => a,
1777 InvokeClosure(a) => a,
1778 DerefPointer(a) => a,
1779 FreeVariable(a, _) => a,
1781 RelateObjectBound(a) => a,
1782 RelateParamBound(a, _) => a,
1783 RelateRegionParamBound(a) => a,
1784 RelateDefaultParamBound(a, _) => a,
1786 ReborrowUpvar(a, _) => a,
1787 DataBorrowed(_, a) => a,
1788 ReferenceOutlivesReferent(_, a) => a,
1789 ParameterInScope(_, a) => a,
1790 ExprTypeIsNotInScope(_, a) => a,
1791 BindingTypeIsNotValidAtDecl(a) => a,
1798 SafeDestructor(a) => a,
1803 impl RegionVariableOrigin {
1804 pub fn span(&self) -> Span {
1806 MiscVariable(a) => a,
1807 PatternRegion(a) => a,
1808 AddrOfRegion(a) => a,
1811 EarlyBoundRegion(a, _) => a,
1812 LateBoundRegion(a, _, _) => a,
1813 BoundRegionInCoherence(_) => syntax_pos::DUMMY_SP,
1814 UpvarRegion(_, a) => a
1819 impl<'tcx> TypeFoldable<'tcx> for TypeOrigin {
1820 fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, _folder: &mut F) -> Self {
1824 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
1829 impl<'tcx> TypeFoldable<'tcx> for ValuePairs<'tcx> {
1830 fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
1832 ValuePairs::Types(ref ef) => {
1833 ValuePairs::Types(ef.fold_with(folder))
1835 ValuePairs::TraitRefs(ref ef) => {
1836 ValuePairs::TraitRefs(ef.fold_with(folder))
1838 ValuePairs::PolyTraitRefs(ref ef) => {
1839 ValuePairs::PolyTraitRefs(ef.fold_with(folder))
1844 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1846 ValuePairs::Types(ref ef) => ef.visit_with(visitor),
1847 ValuePairs::TraitRefs(ref ef) => ef.visit_with(visitor),
1848 ValuePairs::PolyTraitRefs(ref ef) => ef.visit_with(visitor),
1853 impl<'tcx> TypeFoldable<'tcx> for TypeTrace<'tcx> {
1854 fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
1856 origin: self.origin.fold_with(folder),
1857 values: self.values.fold_with(folder)
1861 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1862 self.origin.visit_with(visitor) || self.values.visit_with(visitor)