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::TypeOrigin::*;
17 pub use self::ValuePairs::*;
18 pub use middle::ty::IntVarValue;
19 pub use self::freshen::TypeFreshener;
20 pub use self::region_inference::{GenericKind, VerifyBound};
22 use middle::def_id::DefId;
24 use middle::free_region::FreeRegionMap;
25 use middle::mem_categorization as mc;
26 use middle::mem_categorization::McResult;
27 use middle::region::CodeExtent;
29 use middle::subst::Substs;
30 use middle::subst::Subst;
31 use middle::traits::{self, FulfillmentContext, Normalized,
32 SelectionContext, ObligationCause};
33 use middle::ty::{TyVid, IntVid, FloatVid, RegionVid};
34 use middle::ty::{self, Ty, HasTypeFlags};
35 use middle::ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
36 use middle::ty::fold::{TypeFolder, TypeFoldable};
37 use middle::ty::relate::{Relate, RelateResult, TypeRelation};
38 use rustc_data_structures::unify::{self, UnificationTable};
39 use std::cell::{RefCell, Ref};
44 use syntax::codemap::{Span, DUMMY_SP};
45 use util::nodemap::{FnvHashMap, NodeMap};
47 use self::combine::CombineFields;
48 use self::region_inference::{RegionVarBindings, RegionSnapshot};
49 use self::error_reporting::ErrorReporting;
50 use self::unify_key::ToType;
55 pub mod error_reporting;
60 pub mod region_inference;
64 pub mod type_variable;
67 pub type Bound<T> = Option<T>;
68 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
69 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
71 pub struct InferCtxt<'a, 'tcx: 'a> {
72 pub tcx: &'a ty::ctxt<'tcx>,
74 pub tables: &'a RefCell<ty::Tables<'tcx>>,
76 // We instantiate UnificationTable with bounds<Ty> because the
77 // types that might instantiate a general type variable have an
78 // order, represented by its upper and lower bounds.
79 type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
81 // Map from integral variable to the kind of integer it represents
82 int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
84 // Map from floating variable to the kind of float it represents
85 float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
87 // For region variables.
88 region_vars: RegionVarBindings<'a, 'tcx>,
90 pub parameter_environment: ty::ParameterEnvironment<'a, 'tcx>,
92 pub fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
94 // This is a temporary field used for toggling on normalization in the inference context,
95 // as we move towards the approach described here:
96 // https://internals.rust-lang.org/t/flattening-the-contexts-for-fun-and-profit/2293
97 // At a point sometime in the future normalization will be done by the typing context
101 err_count_on_creation: usize,
104 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
105 /// region that each late-bound region was replaced with.
106 pub type SkolemizationMap = FnvHashMap<ty::BoundRegion,ty::Region>;
108 /// Why did we require that the two types be related?
110 /// See `error_reporting.rs` for more details
111 #[derive(Clone, Copy, Debug)]
112 pub enum TypeOrigin {
113 // Not yet categorized in a better way
116 // Checking that method of impl is compatible with trait
117 MethodCompatCheck(Span),
119 // Checking that this expression can be assigned where it needs to be
120 // FIXME(eddyb) #11161 is the original Expr required?
121 ExprAssignable(Span),
123 // Relating trait refs when resolving vtables
124 RelateTraitRefs(Span),
126 // Relating self types when resolving vtables
127 RelateSelfType(Span),
129 // Relating trait type parameters to those found in impl etc
130 RelateOutputImplTypes(Span),
132 // Computing common supertype in the arms of a match expression
133 MatchExpressionArm(Span, Span),
135 // Computing common supertype in an if expression
138 // Computing common supertype of an if expression with no else counter-part
139 IfExpressionWithNoElse(Span),
141 // Computing common supertype in a range expression
142 RangeExpression(Span),
145 EquatePredicate(Span),
149 fn as_str(&self) -> &'static str {
151 &TypeOrigin::Misc(_) |
152 &TypeOrigin::RelateSelfType(_) |
153 &TypeOrigin::RelateOutputImplTypes(_) |
154 &TypeOrigin::ExprAssignable(_) => "mismatched types",
155 &TypeOrigin::RelateTraitRefs(_) => "mismatched traits",
156 &TypeOrigin::MethodCompatCheck(_) => "method not compatible with trait",
157 &TypeOrigin::MatchExpressionArm(_, _) => "match arms have incompatible types",
158 &TypeOrigin::IfExpression(_) => "if and else have incompatible types",
159 &TypeOrigin::IfExpressionWithNoElse(_) => "if may be missing an else clause",
160 &TypeOrigin::RangeExpression(_) => "start and end of range have incompatible types",
161 &TypeOrigin::EquatePredicate(_) => "equality predicate not satisfied",
166 impl fmt::Display for TypeOrigin {
167 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error> {
168 fmt::Display::fmt(self.as_str(), f)
172 /// See `error_reporting.rs` for more details
173 #[derive(Clone, Debug)]
174 pub enum ValuePairs<'tcx> {
175 Types(ExpectedFound<Ty<'tcx>>),
176 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
177 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
180 /// The trace designates the path through inference that we took to
181 /// encounter an error or subtyping constraint.
183 /// See `error_reporting.rs` for more details.
185 pub struct TypeTrace<'tcx> {
187 values: ValuePairs<'tcx>,
190 /// The origin of a `r1 <= r2` constraint.
192 /// See `error_reporting.rs` for more details
193 #[derive(Clone, Debug)]
194 pub enum SubregionOrigin<'tcx> {
195 // Marker to indicate a constraint that only arises due to new
196 // provisions from RFC 1214. This will result in a warning, not an
198 RFC1214Subregion(Rc<SubregionOrigin<'tcx>>),
200 // Arose from a subtyping relation
201 Subtype(TypeTrace<'tcx>),
203 // Stack-allocated closures cannot outlive innermost loop
204 // or function so as to ensure we only require finite stack
205 InfStackClosure(Span),
207 // Invocation of closure must be within its lifetime
210 // Dereference of reference must be within its lifetime
213 // Closure bound must not outlive captured free variables
214 FreeVariable(Span, ast::NodeId),
216 // Index into slice must be within its lifetime
219 // When casting `&'a T` to an `&'b Trait` object,
220 // relating `'a` to `'b`
221 RelateObjectBound(Span),
223 // Some type parameter was instantiated with the given type,
224 // and that type must outlive some region.
225 RelateParamBound(Span, Ty<'tcx>),
227 // The given region parameter was instantiated with a region
228 // that must outlive some other region.
229 RelateRegionParamBound(Span),
231 // A bound placed on type parameters that states that must outlive
232 // the moment of their instantiation.
233 RelateDefaultParamBound(Span, Ty<'tcx>),
235 // Creating a pointer `b` to contents of another reference
238 // Creating a pointer `b` to contents of an upvar
239 ReborrowUpvar(Span, ty::UpvarId),
241 // Data with type `Ty<'tcx>` was borrowed
242 DataBorrowed(Ty<'tcx>, Span),
244 // (&'a &'b T) where a >= b
245 ReferenceOutlivesReferent(Ty<'tcx>, Span),
247 // Type or region parameters must be in scope.
248 ParameterInScope(ParameterOrigin, Span),
250 // The type T of an expression E must outlive the lifetime for E.
251 ExprTypeIsNotInScope(Ty<'tcx>, Span),
253 // A `ref b` whose region does not enclose the decl site
254 BindingTypeIsNotValidAtDecl(Span),
256 // Regions appearing in a method receiver must outlive method call
259 // Regions appearing in a function argument must outlive func call
262 // Region in return type of invoked fn must enclose call
265 // Operands must be in scope
268 // Region resulting from a `&` expr must enclose the `&` expr
271 // An auto-borrow that does not enclose the expr where it occurs
274 // Region constraint arriving from destructor safety
275 SafeDestructor(Span),
278 /// Places that type/region parameters can appear.
279 #[derive(Clone, Copy, Debug)]
280 pub enum ParameterOrigin {
282 MethodCall, // foo.bar() <-- parameters on impl providing bar()
283 OverloadedOperator, // a + b when overloaded
284 OverloadedDeref, // *a when overloaded
287 /// Times when we replace late-bound regions with variables:
288 #[derive(Clone, Copy, Debug)]
289 pub enum LateBoundRegionConversionTime {
290 /// when a fn is called
293 /// when two higher-ranked types are compared
296 /// when projecting an associated type
297 AssocTypeProjection(ast::Name),
300 /// Reasons to create a region inference variable
302 /// See `error_reporting.rs` for more details
303 #[derive(Clone, Debug)]
304 pub enum RegionVariableOrigin {
305 // Region variables created for ill-categorized reasons,
306 // mostly indicates places in need of refactoring
309 // Regions created by a `&P` or `[...]` pattern
312 // Regions created by `&` operator
315 // Regions created as part of an autoref of a method receiver
318 // Regions created as part of an automatic coercion
321 // Region variables created as the values for early-bound regions
322 EarlyBoundRegion(Span, ast::Name),
324 // Region variables created for bound regions
325 // in a function or method that is called
326 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
328 UpvarRegion(ty::UpvarId, Span),
330 BoundRegionInCoherence(ast::Name),
333 #[derive(Copy, Clone, Debug)]
334 pub enum FixupError {
335 UnresolvedIntTy(IntVid),
336 UnresolvedFloatTy(FloatVid),
340 pub fn fixup_err_to_string(f: FixupError) -> String {
341 use self::FixupError::*;
344 UnresolvedIntTy(_) => {
345 "cannot determine the type of this integer; add a suffix to \
346 specify the type explicitly".to_string()
348 UnresolvedFloatTy(_) => {
349 "cannot determine the type of this number; add a suffix to specify \
350 the type explicitly".to_string()
352 UnresolvedTy(_) => "unconstrained type".to_string(),
356 /// errors_will_be_reported is required to proxy to the fulfillment context
357 /// FIXME -- a better option would be to hold back on modifying
358 /// the global cache until we know that all dependent obligations
359 /// are also satisfied. In that case, we could actually remove
360 /// this boolean flag, and we'd also avoid the problem of squelching
361 /// duplicate errors that occur across fns.
362 pub fn new_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
363 tables: &'a RefCell<ty::Tables<'tcx>>,
364 param_env: Option<ty::ParameterEnvironment<'a, 'tcx>>,
365 errors_will_be_reported: bool)
366 -> InferCtxt<'a, 'tcx> {
370 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
371 int_unification_table: RefCell::new(UnificationTable::new()),
372 float_unification_table: RefCell::new(UnificationTable::new()),
373 region_vars: RegionVarBindings::new(tcx),
374 parameter_environment: param_env.unwrap_or(tcx.empty_parameter_environment()),
375 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new(errors_will_be_reported)),
377 err_count_on_creation: tcx.sess.err_count()
381 pub fn normalizing_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
382 tables: &'a RefCell<ty::Tables<'tcx>>)
383 -> InferCtxt<'a, 'tcx> {
384 let mut infcx = new_infer_ctxt(tcx, tables, None, false);
385 infcx.normalize = true;
389 /// Computes the least upper-bound of `a` and `b`. If this is not possible, reports an error and
391 pub fn common_supertype<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
398 debug!("common_supertype({:?}, {:?})",
401 let trace = TypeTrace {
403 values: Types(expected_found(a_is_expected, a, b))
406 let result = cx.commit_if_ok(|_| cx.lub(a_is_expected, trace.clone()).relate(&a, &b));
410 cx.report_and_explain_type_error(trace, err);
416 pub fn mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
423 debug!("mk_subty({:?} <: {:?})", a, b);
424 cx.sub_types(a_is_expected, origin, a, b)
427 pub fn can_mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
430 -> UnitResult<'tcx> {
431 debug!("can_mk_subty({:?} <: {:?})", a, b);
433 let trace = TypeTrace {
434 origin: Misc(codemap::DUMMY_SP),
435 values: Types(expected_found(true, a, b))
437 cx.sub(true, trace).relate(&a, &b).map(|_| ())
441 pub fn can_mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>, a: Ty<'tcx>, b: Ty<'tcx>)
444 cx.can_equate(&a, &b)
447 pub fn mk_subr<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
448 origin: SubregionOrigin<'tcx>,
451 debug!("mk_subr({:?} <: {:?})", a, b);
452 let snapshot = cx.region_vars.start_snapshot();
453 cx.region_vars.make_subregion(origin, a, b);
454 cx.region_vars.commit(snapshot);
457 pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
464 debug!("mk_eqty({:?} <: {:?})", a, b);
465 cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
468 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
471 a: ty::PolyTraitRef<'tcx>,
472 b: ty::PolyTraitRef<'tcx>)
475 debug!("mk_sub_trait_refs({:?} <: {:?})",
477 cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
480 fn expected_found<T>(a_is_expected: bool,
486 ExpectedFound {expected: a, found: b}
488 ExpectedFound {expected: b, found: a}
492 #[must_use = "once you start a snapshot, you should always consume it"]
493 pub struct CombinedSnapshot {
494 type_snapshot: type_variable::Snapshot,
495 int_snapshot: unify::Snapshot<ty::IntVid>,
496 float_snapshot: unify::Snapshot<ty::FloatVid>,
497 region_vars_snapshot: RegionSnapshot,
500 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
501 where T : TypeFoldable<'tcx> + HasTypeFlags
503 debug!("normalize_associated_type(t={:?})", value);
505 let value = erase_regions(tcx, value);
507 if !value.has_projection_types() {
511 let infcx = new_infer_ctxt(tcx, &tcx.tables, None, true);
512 let mut selcx = traits::SelectionContext::new(&infcx);
513 let cause = traits::ObligationCause::dummy();
514 let traits::Normalized { value: result, obligations } =
515 traits::normalize(&mut selcx, cause, &value);
517 debug!("normalize_associated_type: result={:?} obligations={:?}",
521 let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
523 for obligation in obligations {
524 fulfill_cx.register_predicate_obligation(&infcx, obligation);
527 let result = drain_fulfillment_cx_or_panic(DUMMY_SP, &infcx, &mut fulfill_cx, &result);
532 pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
533 infcx: &InferCtxt<'a,'tcx>,
534 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
537 where T : TypeFoldable<'tcx>
539 match drain_fulfillment_cx(infcx, fulfill_cx, result) {
542 infcx.tcx.sess.span_bug(
544 &format!("Encountered errors `{:?}` fulfilling during trans",
550 /// Finishes processes any obligations that remain in the fulfillment
551 /// context, and then "freshens" and returns `result`. This is
552 /// primarily used during normalization and other cases where
553 /// processing the obligations in `fulfill_cx` may cause type
554 /// inference variables that appear in `result` to be unified, and
555 /// hence we need to process those obligations to get the complete
556 /// picture of the type.
557 pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
558 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
560 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
561 where T : TypeFoldable<'tcx>
563 debug!("drain_fulfillment_cx(result={:?})",
566 // In principle, we only need to do this so long as `result`
567 // contains unbound type parameters. It could be a slight
568 // optimization to stop iterating early.
569 match fulfill_cx.select_all_or_error(infcx) {
576 // Use freshen to simultaneously replace all type variables with
577 // their bindings and replace all regions with 'static. This is
578 // sort of overkill because we do not expect there to be any
579 // unbound type variables, hence no `TyFresh` types should ever be
581 Ok(result.fold_with(&mut infcx.freshener()))
584 /// Returns an equivalent value with all free regions removed (note
585 /// that late-bound regions remain, because they are important for
586 /// subtyping, but they are anonymized and normalized as well). This
587 /// is a stronger, caching version of `ty::fold::erase_regions`.
588 pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
589 where T : TypeFoldable<'tcx>
591 let value1 = value.fold_with(&mut RegionEraser(cx));
592 debug!("erase_regions({:?}) = {:?}",
596 struct RegionEraser<'a, 'tcx: 'a>(&'a ty::ctxt<'tcx>);
598 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
599 fn tcx(&self) -> &ty::ctxt<'tcx> { self.0 }
601 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
602 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
607 let t_norm = ty::fold::super_fold_ty(self, ty);
608 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
612 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
613 where T : TypeFoldable<'tcx>
615 let u = self.tcx().anonymize_late_bound_regions(t);
616 ty::fold::super_fold_binder(self, &u)
619 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
620 // because late-bound regions affect subtyping, we can't
621 // erase the bound/free distinction, but we can replace
622 // all free regions with 'static.
624 // Note that we *CAN* replace early-bound regions -- the
625 // type system never "sees" those, they get substituted
626 // away. In trans, they will always be erased to 'static
627 // whenever a substitution occurs.
629 ty::ReLateBound(..) => r,
634 fn fold_substs(&mut self,
635 substs: &subst::Substs<'tcx>)
636 -> subst::Substs<'tcx> {
637 subst::Substs { regions: subst::ErasedRegions,
638 types: substs.types.fold_with(self) }
643 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
644 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
645 t.fold_with(&mut self.freshener())
648 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
650 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
655 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
656 freshen::TypeFreshener::new(self)
659 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
660 use middle::ty::error::UnconstrainedNumeric::Neither;
661 use middle::ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
663 ty::TyInfer(ty::IntVar(vid)) => {
664 if self.int_unification_table.borrow_mut().has_value(vid) {
670 ty::TyInfer(ty::FloatVar(vid)) => {
671 if self.float_unification_table.borrow_mut().has_value(vid) {
681 /// Returns a type variable's default fallback if any exists. A default
682 /// must be attached to the variable when created, if it is created
683 /// without a default, this will return None.
685 /// This code does not apply to integral or floating point variables,
686 /// only to use declared defaults.
688 /// See `new_ty_var_with_default` to create a type variable with a default.
689 /// See `type_variable::Default` for details about what a default entails.
690 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
692 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
697 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
698 let mut variables = Vec::new();
700 let unbound_ty_vars = self.type_variables
702 .unsolved_variables()
704 .map(|t| self.tcx.mk_var(t));
706 let unbound_int_vars = self.int_unification_table
708 .unsolved_variables()
710 .map(|v| self.tcx.mk_int_var(v));
712 let unbound_float_vars = self.float_unification_table
714 .unsolved_variables()
716 .map(|v| self.tcx.mk_float_var(v));
718 variables.extend(unbound_ty_vars);
719 variables.extend(unbound_int_vars);
720 variables.extend(unbound_float_vars);
725 fn combine_fields(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
726 -> CombineFields<'a, 'tcx> {
727 CombineFields {infcx: self,
728 a_is_expected: a_is_expected,
733 // public so that it can be used from the rustc_driver unit tests
734 pub fn equate(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
735 -> equate::Equate<'a, 'tcx>
737 self.combine_fields(a_is_expected, trace).equate()
740 // public so that it can be used from the rustc_driver unit tests
741 pub fn sub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
742 -> sub::Sub<'a, 'tcx>
744 self.combine_fields(a_is_expected, trace).sub()
747 // public so that it can be used from the rustc_driver unit tests
748 pub fn lub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
749 -> lub::Lub<'a, 'tcx>
751 self.combine_fields(a_is_expected, trace).lub()
754 // public so that it can be used from the rustc_driver unit tests
755 pub fn glb(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
756 -> glb::Glb<'a, 'tcx>
758 self.combine_fields(a_is_expected, trace).glb()
761 fn start_snapshot(&self) -> CombinedSnapshot {
763 type_snapshot: self.type_variables.borrow_mut().snapshot(),
764 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
765 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
766 region_vars_snapshot: self.region_vars.start_snapshot(),
770 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
771 debug!("rollback_to(cause={})", cause);
772 let CombinedSnapshot { type_snapshot,
775 region_vars_snapshot } = snapshot;
779 .rollback_to(type_snapshot);
780 self.int_unification_table
782 .rollback_to(int_snapshot);
783 self.float_unification_table
785 .rollback_to(float_snapshot);
787 .rollback_to(region_vars_snapshot);
790 fn commit_from(&self, snapshot: CombinedSnapshot) {
791 debug!("commit_from!");
792 let CombinedSnapshot { type_snapshot,
795 region_vars_snapshot } = snapshot;
799 .commit(type_snapshot);
800 self.int_unification_table
802 .commit(int_snapshot);
803 self.float_unification_table
805 .commit(float_snapshot);
807 .commit(region_vars_snapshot);
810 /// Execute `f` and commit the bindings
811 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
815 let snapshot = self.start_snapshot();
817 self.commit_from(snapshot);
821 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
822 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
823 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
825 debug!("commit_if_ok()");
826 let snapshot = self.start_snapshot();
827 let r = f(&snapshot);
828 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
830 Ok(_) => { self.commit_from(snapshot); }
831 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
836 /// Execute `f` and commit only the region bindings if successful.
837 /// The function f must be very careful not to leak any non-region
838 /// variables that get created.
839 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
840 F: FnOnce() -> Result<T, E>
842 debug!("commit_regions_if_ok()");
843 let CombinedSnapshot { type_snapshot,
846 region_vars_snapshot } = self.start_snapshot();
848 let r = self.commit_if_ok(|_| f());
850 debug!("commit_regions_if_ok: rolling back everything but regions");
852 // Roll back any non-region bindings - they should be resolved
853 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
856 .rollback_to(type_snapshot);
857 self.int_unification_table
859 .rollback_to(int_snapshot);
860 self.float_unification_table
862 .rollback_to(float_snapshot);
864 // Commit region vars that may escape through resolved types.
866 .commit(region_vars_snapshot);
871 /// Execute `f` then unroll any bindings it creates
872 pub fn probe<R, F>(&self, f: F) -> R where
873 F: FnOnce(&CombinedSnapshot) -> R,
876 let snapshot = self.start_snapshot();
877 let r = f(&snapshot);
878 self.rollback_to("probe", snapshot);
882 pub fn add_given(&self,
886 self.region_vars.add_given(sub, sup);
889 pub fn sub_types(&self,
896 debug!("sub_types({:?} <: {:?})", a, b);
897 self.commit_if_ok(|_| {
898 let trace = TypeTrace::types(origin, a_is_expected, a, b);
899 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
903 pub fn eq_types(&self,
910 self.commit_if_ok(|_| {
911 let trace = TypeTrace::types(origin, a_is_expected, a, b);
912 self.equate(a_is_expected, trace).relate(&a, &b).map(|_| ())
916 pub fn sub_trait_refs(&self,
919 a: ty::TraitRef<'tcx>,
920 b: ty::TraitRef<'tcx>)
923 debug!("sub_trait_refs({:?} <: {:?})",
926 self.commit_if_ok(|_| {
927 let trace = TypeTrace {
929 values: TraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
931 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
935 pub fn sub_poly_trait_refs(&self,
938 a: ty::PolyTraitRef<'tcx>,
939 b: ty::PolyTraitRef<'tcx>)
942 debug!("sub_poly_trait_refs({:?} <: {:?})",
945 self.commit_if_ok(|_| {
946 let trace = TypeTrace {
948 values: PolyTraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
950 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
954 pub fn skolemize_late_bound_regions<T>(&self,
955 value: &ty::Binder<T>,
956 snapshot: &CombinedSnapshot)
957 -> (T, SkolemizationMap)
958 where T : TypeFoldable<'tcx>
960 /*! See `higher_ranked::skolemize_late_bound_regions` */
962 higher_ranked::skolemize_late_bound_regions(self, value, snapshot)
965 pub fn leak_check(&self,
966 skol_map: &SkolemizationMap,
967 snapshot: &CombinedSnapshot)
970 /*! See `higher_ranked::leak_check` */
972 match higher_ranked::leak_check(self, skol_map, snapshot) {
974 Err((br, r)) => Err(TypeError::RegionsInsufficientlyPolymorphic(br, r))
978 pub fn plug_leaks<T>(&self,
979 skol_map: SkolemizationMap,
980 snapshot: &CombinedSnapshot,
983 where T : TypeFoldable<'tcx> + HasTypeFlags
985 /*! See `higher_ranked::plug_leaks` */
987 higher_ranked::plug_leaks(self, skol_map, snapshot, value)
990 pub fn equality_predicate(&self,
992 predicate: &ty::PolyEquatePredicate<'tcx>)
993 -> UnitResult<'tcx> {
994 self.commit_if_ok(|snapshot| {
995 let (ty::EquatePredicate(a, b), skol_map) =
996 self.skolemize_late_bound_regions(predicate, snapshot);
997 let origin = EquatePredicate(span);
998 let () = try!(mk_eqty(self, false, origin, a, b));
999 self.leak_check(&skol_map, snapshot)
1003 pub fn region_outlives_predicate(&self,
1005 predicate: &ty::PolyRegionOutlivesPredicate)
1006 -> UnitResult<'tcx> {
1007 self.commit_if_ok(|snapshot| {
1008 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
1009 self.skolemize_late_bound_regions(predicate, snapshot);
1010 let origin = RelateRegionParamBound(span);
1011 let () = mk_subr(self, origin, r_b, r_a); // `b : a` ==> `a <= b`
1012 self.leak_check(&skol_map, snapshot)
1016 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
1019 .new_var(diverging, None)
1022 pub fn next_ty_var(&self) -> Ty<'tcx> {
1023 self.tcx.mk_var(self.next_ty_var_id(false))
1026 pub fn next_ty_var_with_default(&self,
1027 default: Option<type_variable::Default<'tcx>>) -> Ty<'tcx> {
1028 let ty_var_id = self.type_variables
1030 .new_var(false, default);
1032 self.tcx.mk_var(ty_var_id)
1035 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
1036 self.tcx.mk_var(self.next_ty_var_id(true))
1039 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
1040 (0..n).map(|_i| self.next_ty_var()).collect()
1043 pub fn next_int_var_id(&self) -> IntVid {
1044 self.int_unification_table
1049 pub fn next_float_var_id(&self) -> FloatVid {
1050 self.float_unification_table
1055 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region {
1056 ty::ReVar(self.region_vars.new_region_var(origin))
1059 pub fn region_vars_for_defs(&self,
1061 defs: &[ty::RegionParameterDef])
1062 -> Vec<ty::Region> {
1064 .map(|d| self.next_region_var(EarlyBoundRegion(span, d.name)))
1068 // We have to take `&mut Substs` in order to provide the correct substitutions for defaults
1069 // along the way, for this reason we don't return them.
1070 pub fn type_vars_for_defs(&self,
1072 space: subst::ParamSpace,
1073 substs: &mut Substs<'tcx>,
1074 defs: &[ty::TypeParameterDef<'tcx>]) {
1076 let mut vars = Vec::with_capacity(defs.len());
1078 for def in defs.iter() {
1079 let default = def.default.map(|default| {
1080 type_variable::Default {
1081 ty: default.subst_spanned(self.tcx, substs, Some(span)),
1083 def_id: def.default_def_id
1087 let ty_var = self.next_ty_var_with_default(default);
1088 substs.types.push(space, ty_var);
1093 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1094 /// type/region parameter to a fresh inference variable.
1095 pub fn fresh_substs_for_generics(&self,
1097 generics: &ty::Generics<'tcx>)
1098 -> subst::Substs<'tcx>
1100 let type_params = subst::VecPerParamSpace::empty();
1103 generics.regions.map(
1104 |d| self.next_region_var(EarlyBoundRegion(span, d.name)));
1106 let mut substs = subst::Substs::new(type_params, region_params);
1108 for space in subst::ParamSpace::all().iter() {
1109 self.type_vars_for_defs(
1113 generics.types.get_slice(*space));
1119 /// Given a set of generics defined on a trait, returns a substitution mapping each output
1120 /// type/region parameter to a fresh inference variable, and mapping the self type to
1122 pub fn fresh_substs_for_trait(&self,
1124 generics: &ty::Generics<'tcx>,
1126 -> subst::Substs<'tcx>
1129 assert!(generics.types.len(subst::SelfSpace) == 1);
1130 assert!(generics.types.len(subst::FnSpace) == 0);
1131 assert!(generics.regions.len(subst::SelfSpace) == 0);
1132 assert!(generics.regions.len(subst::FnSpace) == 0);
1134 let type_params = Vec::new();
1136 let region_param_defs = generics.regions.get_slice(subst::TypeSpace);
1137 let regions = self.region_vars_for_defs(span, region_param_defs);
1139 let mut substs = subst::Substs::new_trait(type_params, regions, self_ty);
1141 let type_parameter_defs = generics.types.get_slice(subst::TypeSpace);
1142 self.type_vars_for_defs(span, subst::TypeSpace, &mut substs, type_parameter_defs);
1147 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {
1148 self.region_vars.new_bound(debruijn)
1151 /// Apply `adjustment` to the type of `expr`
1152 pub fn adjust_expr_ty(&self,
1154 adjustment: Option<&ty::AutoAdjustment<'tcx>>)
1157 let raw_ty = self.expr_ty(expr);
1158 let raw_ty = self.shallow_resolve(raw_ty);
1159 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1160 raw_ty.adjust(self.tcx,
1164 |method_call| self.tables
1168 .map(|method| resolve_ty(method.ty)))
1171 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1172 match self.tables.borrow().node_types.get(&id) {
1175 None if self.tcx.sess.err_count() - self.err_count_on_creation != 0 =>
1179 &format!("no type for node {}: {} in fcx",
1180 id, self.tcx.map.node_to_string(id)));
1185 pub fn expr_ty(&self, ex: &hir::Expr) -> Ty<'tcx> {
1186 match self.tables.borrow().node_types.get(&ex.id) {
1189 self.tcx.sess.bug(&format!("no type for expr in fcx"));
1194 pub fn resolve_regions_and_report_errors(&self,
1195 free_regions: &FreeRegionMap,
1196 subject_node_id: ast::NodeId) {
1197 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1198 self.report_region_errors(&errors); // see error_reporting.rs
1201 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1202 self.resolve_type_vars_if_possible(&t).to_string()
1205 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1206 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1207 format!("({})", tstrs.join(", "))
1210 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1211 self.resolve_type_vars_if_possible(t).to_string()
1214 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1216 ty::TyInfer(ty::TyVar(v)) => {
1217 // Not entirely obvious: if `typ` is a type variable,
1218 // it can be resolved to an int/float variable, which
1219 // can then be recursively resolved, hence the
1220 // recursion. Note though that we prevent type
1221 // variables from unifying to other type variables
1222 // directly (though they may be embedded
1223 // structurally), and we prevent cycles in any case,
1224 // so this recursion should always be of very limited
1226 self.type_variables.borrow()
1228 .map(|t| self.shallow_resolve(t))
1232 ty::TyInfer(ty::IntVar(v)) => {
1233 self.int_unification_table
1236 .map(|v| v.to_type(self.tcx))
1240 ty::TyInfer(ty::FloatVar(v)) => {
1241 self.float_unification_table
1244 .map(|v| v.to_type(self.tcx))
1254 pub fn resolve_type_vars_if_possible<T>(&self, value: &T) -> T
1255 where T: TypeFoldable<'tcx> + HasTypeFlags
1258 * Where possible, replaces type/int/float variables in
1259 * `value` with their final value. Note that region variables
1260 * are unaffected. If a type variable has not been unified, it
1261 * is left as is. This is an idempotent operation that does
1262 * not affect inference state in any way and so you can do it
1266 if !value.needs_infer() {
1267 return value.clone(); // avoid duplicated subst-folding
1269 let mut r = resolve::OpportunisticTypeResolver::new(self);
1270 value.fold_with(&mut r)
1273 /// Resolves all type variables in `t` and then, if any were left
1274 /// unresolved, substitutes an error type. This is used after the
1275 /// main checking when doing a second pass before writeback. The
1276 /// justification is that writeback will produce an error for
1277 /// these unconstrained type variables.
1278 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1279 let ty = self.resolve_type_vars_if_possible(t);
1280 if ty.references_error() || ty.is_ty_var() {
1281 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1288 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1290 * Attempts to resolve all type/region variables in
1291 * `value`. Region inference must have been run already (e.g.,
1292 * by calling `resolve_regions_and_report_errors`). If some
1293 * variable was never unified, an `Err` results.
1295 * This method is idempotent, but it not typically not invoked
1296 * except during the writeback phase.
1299 resolve::fully_resolve(self, value)
1302 // [Note-Type-error-reporting]
1303 // An invariant is that anytime the expected or actual type is TyError (the special
1304 // error type, meaning that an error occurred when typechecking this expression),
1305 // this is a derived error. The error cascaded from another error (that was already
1306 // reported), so it's not useful to display it to the user.
1307 // The following four methods -- type_error_message_str, type_error_message_str_with_expected,
1308 // type_error_message, and report_mismatched_types -- implement this logic.
1309 // They check if either the actual or expected type is TyError, and don't print the error
1310 // in this case. The typechecker should only ever report type errors involving mismatched
1311 // types using one of these four methods, and should not call span_err directly for such
1313 pub fn type_error_message_str<M>(&self,
1317 err: Option<&TypeError<'tcx>>) where
1318 M: FnOnce(Option<String>, String) -> String,
1320 self.type_error_message_str_with_expected(sp, mk_msg, None, actual_ty, err)
1323 pub fn type_error_message_str_with_expected<M>(&self,
1326 expected_ty: Option<Ty<'tcx>>,
1328 err: Option<&TypeError<'tcx>>) where
1329 M: FnOnce(Option<String>, String) -> String,
1331 debug!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
1333 let resolved_expected = expected_ty.map(|e_ty| self.resolve_type_vars_if_possible(&e_ty));
1335 if !resolved_expected.references_error() {
1336 let error_str = err.map_or("".to_string(), |t_err| {
1337 format!(" ({})", t_err)
1340 self.tcx.sess.span_err(sp, &format!("{}{}",
1341 mk_msg(resolved_expected.map(|t| self.ty_to_string(t)), actual_ty),
1344 if let Some(err) = err {
1345 self.tcx.note_and_explain_type_err(err, sp)
1350 pub fn type_error_message<M>(&self,
1353 actual_ty: Ty<'tcx>,
1354 err: Option<&TypeError<'tcx>>) where
1355 M: FnOnce(String) -> String,
1357 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1359 // Don't report an error if actual type is TyError.
1360 if actual_ty.references_error() {
1364 self.type_error_message_str(sp,
1365 move |_e, a| { mk_msg(a) },
1366 self.ty_to_string(actual_ty), err);
1369 pub fn report_mismatched_types(&self,
1373 err: &TypeError<'tcx>) {
1374 let trace = TypeTrace {
1376 values: Types(ExpectedFound {
1381 self.report_and_explain_type_error(trace, err);
1384 pub fn report_conflicting_default_types(&self,
1386 expected: type_variable::Default<'tcx>,
1387 actual: type_variable::Default<'tcx>) {
1388 let trace = TypeTrace {
1390 values: Types(ExpectedFound {
1391 expected: expected.ty,
1396 self.report_and_explain_type_error(trace,
1397 &TypeError::TyParamDefaultMismatch(ExpectedFound {
1403 pub fn replace_late_bound_regions_with_fresh_var<T>(
1406 lbrct: LateBoundRegionConversionTime,
1407 value: &ty::Binder<T>)
1408 -> (T, FnvHashMap<ty::BoundRegion,ty::Region>)
1409 where T : TypeFoldable<'tcx>
1411 self.tcx.replace_late_bound_regions(
1413 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1416 /// See `verify_generic_bound` method in `region_inference`
1417 pub fn verify_generic_bound(&self,
1418 origin: SubregionOrigin<'tcx>,
1419 kind: GenericKind<'tcx>,
1421 bound: VerifyBound) {
1422 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1427 self.region_vars.verify_generic_bound(origin, kind, a, bound);
1430 pub fn can_equate<'b,T>(&'b self, a: &T, b: &T) -> UnitResult<'tcx>
1431 where T: Relate<'b,'tcx> + fmt::Debug
1433 debug!("can_equate({:?}, {:?})", a, b);
1435 // Gin up a dummy trace, since this won't be committed
1436 // anyhow. We should make this typetrace stuff more
1437 // generic so we don't have to do anything quite this
1439 let e = self.tcx.types.err;
1440 let trace = TypeTrace { origin: Misc(codemap::DUMMY_SP),
1441 values: Types(expected_found(true, e, e)) };
1442 self.equate(true, trace).relate(a, b)
1446 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1447 let ty = self.node_type(id);
1448 self.resolve_type_vars_or_error(&ty)
1451 pub fn expr_ty_adjusted(&self, expr: &hir::Expr) -> McResult<Ty<'tcx>> {
1452 let ty = self.adjust_expr_ty(expr, self.tables.borrow().adjustments.get(&expr.id));
1453 self.resolve_type_vars_or_error(&ty)
1456 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1457 let ty = self.resolve_type_vars_if_possible(&ty);
1458 if ty.needs_infer() {
1459 // this can get called from typeck (by euv), and moves_by_default
1460 // rightly refuses to work with inference variables, but
1461 // moves_by_default has a cache, which we want to use in other
1463 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1465 ty.moves_by_default(&self.parameter_environment, span)
1469 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1470 -> Option<Ty<'tcx>> {
1475 .map(|method| method.ty)
1476 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1479 pub fn node_method_id(&self, method_call: ty::MethodCall)
1485 .map(|method| method.def_id)
1488 pub fn adjustments(&self) -> Ref<NodeMap<ty::AutoAdjustment<'tcx>>> {
1489 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1490 -> &'a NodeMap<ty::AutoAdjustment<'tcx>> {
1494 Ref::map(self.tables.borrow(), project_adjustments)
1497 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1498 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1501 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1502 self.tcx.region_maps.temporary_scope(rvalue_id)
1505 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture> {
1506 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1509 pub fn param_env<'b>(&'b self) -> &'b ty::ParameterEnvironment<'b,'tcx> {
1510 &self.parameter_environment
1513 pub fn closure_kind(&self,
1515 -> Option<ty::ClosureKind>
1517 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1520 pub fn closure_type(&self,
1522 substs: &ty::ClosureSubsts<'tcx>)
1523 -> ty::ClosureTy<'tcx>
1525 let closure_ty = self.tables
1530 .subst(self.tcx, &substs.func_substs);
1533 normalize_associated_type(&self.tcx, &closure_ty)
1540 impl<'tcx> TypeTrace<'tcx> {
1541 pub fn span(&self) -> Span {
1545 pub fn types(origin: TypeOrigin,
1546 a_is_expected: bool,
1549 -> TypeTrace<'tcx> {
1552 values: Types(expected_found(a_is_expected, a, b))
1556 pub fn dummy(tcx: &ty::ctxt<'tcx>) -> TypeTrace<'tcx> {
1558 origin: Misc(codemap::DUMMY_SP),
1559 values: Types(ExpectedFound {
1560 expected: tcx.types.err,
1561 found: tcx.types.err,
1567 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1568 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1569 write!(f, "TypeTrace({:?})", self.origin)
1574 pub fn span(&self) -> Span {
1576 MethodCompatCheck(span) => span,
1577 ExprAssignable(span) => span,
1579 RelateTraitRefs(span) => span,
1580 RelateSelfType(span) => span,
1581 RelateOutputImplTypes(span) => span,
1582 MatchExpressionArm(match_span, _) => match_span,
1583 IfExpression(span) => span,
1584 IfExpressionWithNoElse(span) => span,
1585 RangeExpression(span) => span,
1586 EquatePredicate(span) => span,
1591 impl<'tcx> SubregionOrigin<'tcx> {
1592 pub fn span(&self) -> Span {
1594 RFC1214Subregion(ref a) => a.span(),
1595 Subtype(ref a) => a.span(),
1596 InfStackClosure(a) => a,
1597 InvokeClosure(a) => a,
1598 DerefPointer(a) => a,
1599 FreeVariable(a, _) => a,
1601 RelateObjectBound(a) => a,
1602 RelateParamBound(a, _) => a,
1603 RelateRegionParamBound(a) => a,
1604 RelateDefaultParamBound(a, _) => a,
1606 ReborrowUpvar(a, _) => a,
1607 DataBorrowed(_, a) => a,
1608 ReferenceOutlivesReferent(_, a) => a,
1609 ParameterInScope(_, a) => a,
1610 ExprTypeIsNotInScope(_, a) => a,
1611 BindingTypeIsNotValidAtDecl(a) => a,
1618 SafeDestructor(a) => a,
1623 impl RegionVariableOrigin {
1624 pub fn span(&self) -> Span {
1626 MiscVariable(a) => a,
1627 PatternRegion(a) => a,
1628 AddrOfRegion(a) => a,
1631 EarlyBoundRegion(a, _) => a,
1632 LateBoundRegion(a, _, _) => a,
1633 BoundRegionInCoherence(_) => codemap::DUMMY_SP,
1634 UpvarRegion(_, a) => a