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, UnconstrainedNumeric};
34 use middle::ty::{self, Ty, TypeError, HasTypeFlags};
35 use middle::ty_fold::{self, TypeFolder, TypeFoldable};
36 use middle::ty_relate::{Relate, RelateResult, TypeRelation};
37 use rustc_data_structures::unify::{self, UnificationTable};
38 use std::cell::{RefCell, Ref};
43 use syntax::codemap::{Span, DUMMY_SP};
44 use util::nodemap::{FnvHashMap, NodeMap};
46 use self::combine::CombineFields;
47 use self::region_inference::{RegionVarBindings, RegionSnapshot};
48 use self::error_reporting::ErrorReporting;
49 use self::unify_key::ToType;
54 pub mod error_reporting;
59 pub mod region_inference;
63 pub mod type_variable;
66 pub type Bound<T> = Option<T>;
67 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
68 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
70 pub struct InferCtxt<'a, 'tcx: 'a> {
71 pub tcx: &'a ty::ctxt<'tcx>,
73 pub tables: &'a RefCell<ty::Tables<'tcx>>,
75 // We instantiate UnificationTable with bounds<Ty> because the
76 // types that might instantiate a general type variable have an
77 // order, represented by its upper and lower bounds.
78 type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
80 // Map from integral variable to the kind of integer it represents
81 int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
83 // Map from floating variable to the kind of float it represents
84 float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
86 // For region variables.
87 region_vars: RegionVarBindings<'a, 'tcx>,
89 pub parameter_environment: ty::ParameterEnvironment<'a, 'tcx>,
91 pub fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
93 // This is a temporary field used for toggling on normalization in the inference context,
94 // as we move towards the approach described here:
95 // https://internals.rust-lang.org/t/flattening-the-contexts-for-fun-and-profit/2293
96 // At a point sometime in the future normalization will be done by the typing context
100 err_count_on_creation: usize,
103 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
104 /// region that each late-bound region was replaced with.
105 pub type SkolemizationMap = FnvHashMap<ty::BoundRegion,ty::Region>;
107 /// Why did we require that the two types be related?
109 /// See `error_reporting.rs` for more details
110 #[derive(Clone, Copy, Debug)]
111 pub enum TypeOrigin {
112 // Not yet categorized in a better way
115 // Checking that method of impl is compatible with trait
116 MethodCompatCheck(Span),
118 // Checking that this expression can be assigned where it needs to be
119 // FIXME(eddyb) #11161 is the original Expr required?
120 ExprAssignable(Span),
122 // Relating trait refs when resolving vtables
123 RelateTraitRefs(Span),
125 // Relating self types when resolving vtables
126 RelateSelfType(Span),
128 // Relating trait type parameters to those found in impl etc
129 RelateOutputImplTypes(Span),
131 // Computing common supertype in the arms of a match expression
132 MatchExpressionArm(Span, Span),
134 // Computing common supertype in an if expression
137 // Computing common supertype of an if expression with no else counter-part
138 IfExpressionWithNoElse(Span),
140 // Computing common supertype in a range expression
141 RangeExpression(Span),
144 EquatePredicate(Span),
148 fn as_str(&self) -> &'static str {
150 &TypeOrigin::Misc(_) |
151 &TypeOrigin::RelateSelfType(_) |
152 &TypeOrigin::RelateOutputImplTypes(_) |
153 &TypeOrigin::ExprAssignable(_) => "mismatched types",
154 &TypeOrigin::RelateTraitRefs(_) => "mismatched traits",
155 &TypeOrigin::MethodCompatCheck(_) => "method not compatible with trait",
156 &TypeOrigin::MatchExpressionArm(_, _) => "match arms have incompatible types",
157 &TypeOrigin::IfExpression(_) => "if and else have incompatible types",
158 &TypeOrigin::IfExpressionWithNoElse(_) => "if may be missing an else clause",
159 &TypeOrigin::RangeExpression(_) => "start and end of range have incompatible types",
160 &TypeOrigin::EquatePredicate(_) => "equality predicate not satisfied",
165 impl fmt::Display for TypeOrigin {
166 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error> {
167 fmt::Display::fmt(self.as_str(), f)
171 /// See `error_reporting.rs` for more details
172 #[derive(Clone, Debug)]
173 pub enum ValuePairs<'tcx> {
174 Types(ty::ExpectedFound<Ty<'tcx>>),
175 TraitRefs(ty::ExpectedFound<ty::TraitRef<'tcx>>),
176 PolyTraitRefs(ty::ExpectedFound<ty::PolyTraitRef<'tcx>>),
179 /// The trace designates the path through inference that we took to
180 /// encounter an error or subtyping constraint.
182 /// See `error_reporting.rs` for more details.
184 pub struct TypeTrace<'tcx> {
186 values: ValuePairs<'tcx>,
189 /// The origin of a `r1 <= r2` constraint.
191 /// See `error_reporting.rs` for more details
192 #[derive(Clone, Debug)]
193 pub enum SubregionOrigin<'tcx> {
194 // Marker to indicate a constraint that only arises due to new
195 // provisions from RFC 1214. This will result in a warning, not an
197 RFC1214Subregion(Rc<SubregionOrigin<'tcx>>),
199 // Arose from a subtyping relation
200 Subtype(TypeTrace<'tcx>),
202 // Stack-allocated closures cannot outlive innermost loop
203 // or function so as to ensure we only require finite stack
204 InfStackClosure(Span),
206 // Invocation of closure must be within its lifetime
209 // Dereference of reference must be within its lifetime
212 // Closure bound must not outlive captured free variables
213 FreeVariable(Span, ast::NodeId),
215 // Index into slice must be within its lifetime
218 // When casting `&'a T` to an `&'b Trait` object,
219 // relating `'a` to `'b`
220 RelateObjectBound(Span),
222 // Some type parameter was instantiated with the given type,
223 // and that type must outlive some region.
224 RelateParamBound(Span, Ty<'tcx>),
226 // The given region parameter was instantiated with a region
227 // that must outlive some other region.
228 RelateRegionParamBound(Span),
230 // A bound placed on type parameters that states that must outlive
231 // the moment of their instantiation.
232 RelateDefaultParamBound(Span, Ty<'tcx>),
234 // Creating a pointer `b` to contents of another reference
237 // Creating a pointer `b` to contents of an upvar
238 ReborrowUpvar(Span, ty::UpvarId),
240 // Data with type `Ty<'tcx>` was borrowed
241 DataBorrowed(Ty<'tcx>, Span),
243 // (&'a &'b T) where a >= b
244 ReferenceOutlivesReferent(Ty<'tcx>, Span),
246 // Type or region parameters must be in scope.
247 ParameterInScope(ParameterOrigin, Span),
249 // The type T of an expression E must outlive the lifetime for E.
250 ExprTypeIsNotInScope(Ty<'tcx>, Span),
252 // A `ref b` whose region does not enclose the decl site
253 BindingTypeIsNotValidAtDecl(Span),
255 // Regions appearing in a method receiver must outlive method call
258 // Regions appearing in a function argument must outlive func call
261 // Region in return type of invoked fn must enclose call
264 // Operands must be in scope
267 // Region resulting from a `&` expr must enclose the `&` expr
270 // An auto-borrow that does not enclose the expr where it occurs
273 // Region constraint arriving from destructor safety
274 SafeDestructor(Span),
277 /// Places that type/region parameters can appear.
278 #[derive(Clone, Copy, Debug)]
279 pub enum ParameterOrigin {
281 MethodCall, // foo.bar() <-- parameters on impl providing bar()
282 OverloadedOperator, // a + b when overloaded
283 OverloadedDeref, // *a when overloaded
286 /// Times when we replace late-bound regions with variables:
287 #[derive(Clone, Copy, Debug)]
288 pub enum LateBoundRegionConversionTime {
289 /// when a fn is called
292 /// when two higher-ranked types are compared
295 /// when projecting an associated type
296 AssocTypeProjection(ast::Name),
299 /// Reasons to create a region inference variable
301 /// See `error_reporting.rs` for more details
302 #[derive(Clone, Debug)]
303 pub enum RegionVariableOrigin {
304 // Region variables created for ill-categorized reasons,
305 // mostly indicates places in need of refactoring
308 // Regions created by a `&P` or `[...]` pattern
311 // Regions created by `&` operator
314 // Regions created as part of an autoref of a method receiver
317 // Regions created as part of an automatic coercion
320 // Region variables created as the values for early-bound regions
321 EarlyBoundRegion(Span, ast::Name),
323 // Region variables created for bound regions
324 // in a function or method that is called
325 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
327 UpvarRegion(ty::UpvarId, Span),
329 BoundRegionInCoherence(ast::Name),
332 #[derive(Copy, Clone, Debug)]
333 pub enum FixupError {
334 UnresolvedIntTy(IntVid),
335 UnresolvedFloatTy(FloatVid),
339 pub fn fixup_err_to_string(f: FixupError) -> String {
340 use self::FixupError::*;
343 UnresolvedIntTy(_) => {
344 "cannot determine the type of this integer; add a suffix to \
345 specify the type explicitly".to_string()
347 UnresolvedFloatTy(_) => {
348 "cannot determine the type of this number; add a suffix to specify \
349 the type explicitly".to_string()
351 UnresolvedTy(_) => "unconstrained type".to_string(),
355 /// errors_will_be_reported is required to proxy to the fulfillment context
356 /// FIXME -- a better option would be to hold back on modifying
357 /// the global cache until we know that all dependent obligations
358 /// are also satisfied. In that case, we could actually remove
359 /// this boolean flag, and we'd also avoid the problem of squelching
360 /// duplicate errors that occur across fns.
361 pub fn new_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
362 tables: &'a RefCell<ty::Tables<'tcx>>,
363 param_env: Option<ty::ParameterEnvironment<'a, 'tcx>>,
364 errors_will_be_reported: bool)
365 -> InferCtxt<'a, 'tcx> {
369 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
370 int_unification_table: RefCell::new(UnificationTable::new()),
371 float_unification_table: RefCell::new(UnificationTable::new()),
372 region_vars: RegionVarBindings::new(tcx),
373 parameter_environment: param_env.unwrap_or(tcx.empty_parameter_environment()),
374 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new(errors_will_be_reported)),
376 err_count_on_creation: tcx.sess.err_count()
380 pub fn normalizing_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
381 tables: &'a RefCell<ty::Tables<'tcx>>)
382 -> InferCtxt<'a, 'tcx> {
383 let mut infcx = new_infer_ctxt(tcx, tables, None, false);
384 infcx.normalize = true;
388 /// Computes the least upper-bound of `a` and `b`. If this is not possible, reports an error and
390 pub fn common_supertype<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
397 debug!("common_supertype({:?}, {:?})",
400 let trace = TypeTrace {
402 values: Types(expected_found(a_is_expected, a, b))
405 let result = cx.commit_if_ok(|_| cx.lub(a_is_expected, trace.clone()).relate(&a, &b));
409 cx.report_and_explain_type_error(trace, err);
415 pub fn mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
422 debug!("mk_subty({:?} <: {:?})", a, b);
423 cx.sub_types(a_is_expected, origin, a, b)
426 pub fn can_mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
429 -> UnitResult<'tcx> {
430 debug!("can_mk_subty({:?} <: {:?})", a, b);
432 let trace = TypeTrace {
433 origin: Misc(codemap::DUMMY_SP),
434 values: Types(expected_found(true, a, b))
436 cx.sub(true, trace).relate(&a, &b).map(|_| ())
440 pub fn can_mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>, a: Ty<'tcx>, b: Ty<'tcx>)
443 cx.can_equate(&a, &b)
446 pub fn mk_subr<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
447 origin: SubregionOrigin<'tcx>,
450 debug!("mk_subr({:?} <: {:?})", a, b);
451 let snapshot = cx.region_vars.start_snapshot();
452 cx.region_vars.make_subregion(origin, a, b);
453 cx.region_vars.commit(snapshot);
456 pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
463 debug!("mk_eqty({:?} <: {:?})", a, b);
464 cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
467 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
470 a: ty::PolyTraitRef<'tcx>,
471 b: ty::PolyTraitRef<'tcx>)
474 debug!("mk_sub_trait_refs({:?} <: {:?})",
476 cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
479 fn expected_found<T>(a_is_expected: bool,
482 -> ty::ExpectedFound<T>
485 ty::ExpectedFound {expected: a, found: b}
487 ty::ExpectedFound {expected: b, found: a}
491 #[must_use = "once you start a snapshot, you should always consume it"]
492 pub struct CombinedSnapshot {
493 type_snapshot: type_variable::Snapshot,
494 int_snapshot: unify::Snapshot<ty::IntVid>,
495 float_snapshot: unify::Snapshot<ty::FloatVid>,
496 region_vars_snapshot: RegionSnapshot,
499 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
500 where T : TypeFoldable<'tcx> + HasTypeFlags
502 debug!("normalize_associated_type(t={:?})", value);
504 let value = erase_regions(tcx, value);
506 if !value.has_projection_types() {
510 let infcx = new_infer_ctxt(tcx, &tcx.tables, None, true);
511 let mut selcx = traits::SelectionContext::new(&infcx);
512 let cause = traits::ObligationCause::dummy();
513 let traits::Normalized { value: result, obligations } =
514 traits::normalize(&mut selcx, cause, &value);
516 debug!("normalize_associated_type: result={:?} obligations={:?}",
520 let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
522 for obligation in obligations {
523 fulfill_cx.register_predicate_obligation(&infcx, obligation);
526 let result = drain_fulfillment_cx_or_panic(DUMMY_SP, &infcx, &mut fulfill_cx, &result);
531 pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
532 infcx: &InferCtxt<'a,'tcx>,
533 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
536 where T : TypeFoldable<'tcx>
538 match drain_fulfillment_cx(infcx, fulfill_cx, result) {
541 infcx.tcx.sess.span_bug(
543 &format!("Encountered errors `{:?}` fulfilling during trans",
549 /// Finishes processes any obligations that remain in the fulfillment
550 /// context, and then "freshens" and returns `result`. This is
551 /// primarily used during normalization and other cases where
552 /// processing the obligations in `fulfill_cx` may cause type
553 /// inference variables that appear in `result` to be unified, and
554 /// hence we need to process those obligations to get the complete
555 /// picture of the type.
556 pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
557 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
559 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
560 where T : TypeFoldable<'tcx>
562 debug!("drain_fulfillment_cx(result={:?})",
565 // In principle, we only need to do this so long as `result`
566 // contains unbound type parameters. It could be a slight
567 // optimization to stop iterating early.
568 match fulfill_cx.select_all_or_error(infcx) {
575 // Use freshen to simultaneously replace all type variables with
576 // their bindings and replace all regions with 'static. This is
577 // sort of overkill because we do not expect there to be any
578 // unbound type variables, hence no `TyFresh` types should ever be
580 Ok(result.fold_with(&mut infcx.freshener()))
583 /// Returns an equivalent value with all free regions removed (note
584 /// that late-bound regions remain, because they are important for
585 /// subtyping, but they are anonymized and normalized as well). This
586 /// is a stronger, caching version of `ty_fold::erase_regions`.
587 pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
588 where T : TypeFoldable<'tcx>
590 let value1 = value.fold_with(&mut RegionEraser(cx));
591 debug!("erase_regions({:?}) = {:?}",
595 struct RegionEraser<'a, 'tcx: 'a>(&'a ty::ctxt<'tcx>);
597 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
598 fn tcx(&self) -> &ty::ctxt<'tcx> { self.0 }
600 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
601 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
606 let t_norm = ty_fold::super_fold_ty(self, ty);
607 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
611 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
612 where T : TypeFoldable<'tcx>
614 let u = self.tcx().anonymize_late_bound_regions(t);
615 ty_fold::super_fold_binder(self, &u)
618 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
619 // because late-bound regions affect subtyping, we can't
620 // erase the bound/free distinction, but we can replace
621 // all free regions with 'static.
623 // Note that we *CAN* replace early-bound regions -- the
624 // type system never "sees" those, they get substituted
625 // away. In trans, they will always be erased to 'static
626 // whenever a substitution occurs.
628 ty::ReLateBound(..) => r,
633 fn fold_substs(&mut self,
634 substs: &subst::Substs<'tcx>)
635 -> subst::Substs<'tcx> {
636 subst::Substs { regions: subst::ErasedRegions,
637 types: substs.types.fold_with(self) }
642 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
643 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
644 t.fold_with(&mut self.freshener())
647 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
649 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
654 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
655 freshen::TypeFreshener::new(self)
658 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
659 use middle::ty::UnconstrainedNumeric::{Neither, UnconstrainedInt, UnconstrainedFloat};
661 ty::TyInfer(ty::IntVar(vid)) => {
662 if self.int_unification_table.borrow_mut().has_value(vid) {
668 ty::TyInfer(ty::FloatVar(vid)) => {
669 if self.float_unification_table.borrow_mut().has_value(vid) {
679 /// Returns a type variable's default fallback if any exists. A default
680 /// must be attached to the variable when created, if it is created
681 /// without a default, this will return None.
683 /// This code does not apply to integral or floating point variables,
684 /// only to use declared defaults.
686 /// See `new_ty_var_with_default` to create a type variable with a default.
687 /// See `type_variable::Default` for details about what a default entails.
688 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
690 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
695 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
696 let mut variables = Vec::new();
698 let unbound_ty_vars = self.type_variables
700 .unsolved_variables()
702 .map(|t| self.tcx.mk_var(t));
704 let unbound_int_vars = self.int_unification_table
706 .unsolved_variables()
708 .map(|v| self.tcx.mk_int_var(v));
710 let unbound_float_vars = self.float_unification_table
712 .unsolved_variables()
714 .map(|v| self.tcx.mk_float_var(v));
716 variables.extend(unbound_ty_vars);
717 variables.extend(unbound_int_vars);
718 variables.extend(unbound_float_vars);
723 fn combine_fields(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
724 -> CombineFields<'a, 'tcx> {
725 CombineFields {infcx: self,
726 a_is_expected: a_is_expected,
731 // public so that it can be used from the rustc_driver unit tests
732 pub fn equate(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
733 -> equate::Equate<'a, 'tcx>
735 self.combine_fields(a_is_expected, trace).equate()
738 // public so that it can be used from the rustc_driver unit tests
739 pub fn sub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
740 -> sub::Sub<'a, 'tcx>
742 self.combine_fields(a_is_expected, trace).sub()
745 // public so that it can be used from the rustc_driver unit tests
746 pub fn lub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
747 -> lub::Lub<'a, 'tcx>
749 self.combine_fields(a_is_expected, trace).lub()
752 // public so that it can be used from the rustc_driver unit tests
753 pub fn glb(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
754 -> glb::Glb<'a, 'tcx>
756 self.combine_fields(a_is_expected, trace).glb()
759 fn start_snapshot(&self) -> CombinedSnapshot {
761 type_snapshot: self.type_variables.borrow_mut().snapshot(),
762 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
763 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
764 region_vars_snapshot: self.region_vars.start_snapshot(),
768 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
769 debug!("rollback_to(cause={})", cause);
770 let CombinedSnapshot { type_snapshot,
773 region_vars_snapshot } = snapshot;
777 .rollback_to(type_snapshot);
778 self.int_unification_table
780 .rollback_to(int_snapshot);
781 self.float_unification_table
783 .rollback_to(float_snapshot);
785 .rollback_to(region_vars_snapshot);
788 fn commit_from(&self, snapshot: CombinedSnapshot) {
789 debug!("commit_from!");
790 let CombinedSnapshot { type_snapshot,
793 region_vars_snapshot } = snapshot;
797 .commit(type_snapshot);
798 self.int_unification_table
800 .commit(int_snapshot);
801 self.float_unification_table
803 .commit(float_snapshot);
805 .commit(region_vars_snapshot);
808 /// Execute `f` and commit the bindings
809 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
813 let snapshot = self.start_snapshot();
815 self.commit_from(snapshot);
819 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
820 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
821 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
823 debug!("commit_if_ok()");
824 let snapshot = self.start_snapshot();
825 let r = f(&snapshot);
826 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
828 Ok(_) => { self.commit_from(snapshot); }
829 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
834 /// Execute `f` and commit only the region bindings if successful.
835 /// The function f must be very careful not to leak any non-region
836 /// variables that get created.
837 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
838 F: FnOnce() -> Result<T, E>
840 debug!("commit_regions_if_ok()");
841 let CombinedSnapshot { type_snapshot,
844 region_vars_snapshot } = self.start_snapshot();
846 let r = self.commit_if_ok(|_| f());
848 debug!("commit_regions_if_ok: rolling back everything but regions");
850 // Roll back any non-region bindings - they should be resolved
851 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
854 .rollback_to(type_snapshot);
855 self.int_unification_table
857 .rollback_to(int_snapshot);
858 self.float_unification_table
860 .rollback_to(float_snapshot);
862 // Commit region vars that may escape through resolved types.
864 .commit(region_vars_snapshot);
869 /// Execute `f` then unroll any bindings it creates
870 pub fn probe<R, F>(&self, f: F) -> R where
871 F: FnOnce(&CombinedSnapshot) -> R,
874 let snapshot = self.start_snapshot();
875 let r = f(&snapshot);
876 self.rollback_to("probe", snapshot);
880 pub fn add_given(&self,
884 self.region_vars.add_given(sub, sup);
887 pub fn sub_types(&self,
894 debug!("sub_types({:?} <: {:?})", a, b);
895 self.commit_if_ok(|_| {
896 let trace = TypeTrace::types(origin, a_is_expected, a, b);
897 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
901 pub fn eq_types(&self,
908 self.commit_if_ok(|_| {
909 let trace = TypeTrace::types(origin, a_is_expected, a, b);
910 self.equate(a_is_expected, trace).relate(&a, &b).map(|_| ())
914 pub fn sub_trait_refs(&self,
917 a: ty::TraitRef<'tcx>,
918 b: ty::TraitRef<'tcx>)
921 debug!("sub_trait_refs({:?} <: {:?})",
924 self.commit_if_ok(|_| {
925 let trace = TypeTrace {
927 values: TraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
929 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
933 pub fn sub_poly_trait_refs(&self,
936 a: ty::PolyTraitRef<'tcx>,
937 b: ty::PolyTraitRef<'tcx>)
940 debug!("sub_poly_trait_refs({:?} <: {:?})",
943 self.commit_if_ok(|_| {
944 let trace = TypeTrace {
946 values: PolyTraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
948 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
952 pub fn skolemize_late_bound_regions<T>(&self,
953 value: &ty::Binder<T>,
954 snapshot: &CombinedSnapshot)
955 -> (T, SkolemizationMap)
956 where T : TypeFoldable<'tcx>
958 /*! See `higher_ranked::skolemize_late_bound_regions` */
960 higher_ranked::skolemize_late_bound_regions(self, value, snapshot)
963 pub fn leak_check(&self,
964 skol_map: &SkolemizationMap,
965 snapshot: &CombinedSnapshot)
968 /*! See `higher_ranked::leak_check` */
970 match higher_ranked::leak_check(self, skol_map, snapshot) {
972 Err((br, r)) => Err(TypeError::RegionsInsufficientlyPolymorphic(br, r))
976 pub fn plug_leaks<T>(&self,
977 skol_map: SkolemizationMap,
978 snapshot: &CombinedSnapshot,
981 where T : TypeFoldable<'tcx> + HasTypeFlags
983 /*! See `higher_ranked::plug_leaks` */
985 higher_ranked::plug_leaks(self, skol_map, snapshot, value)
988 pub fn equality_predicate(&self,
990 predicate: &ty::PolyEquatePredicate<'tcx>)
991 -> UnitResult<'tcx> {
992 self.commit_if_ok(|snapshot| {
993 let (ty::EquatePredicate(a, b), skol_map) =
994 self.skolemize_late_bound_regions(predicate, snapshot);
995 let origin = EquatePredicate(span);
996 let () = try!(mk_eqty(self, false, origin, a, b));
997 self.leak_check(&skol_map, snapshot)
1001 pub fn region_outlives_predicate(&self,
1003 predicate: &ty::PolyRegionOutlivesPredicate)
1004 -> UnitResult<'tcx> {
1005 self.commit_if_ok(|snapshot| {
1006 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
1007 self.skolemize_late_bound_regions(predicate, snapshot);
1008 let origin = RelateRegionParamBound(span);
1009 let () = mk_subr(self, origin, r_b, r_a); // `b : a` ==> `a <= b`
1010 self.leak_check(&skol_map, snapshot)
1014 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
1017 .new_var(diverging, None)
1020 pub fn next_ty_var(&self) -> Ty<'tcx> {
1021 self.tcx.mk_var(self.next_ty_var_id(false))
1024 pub fn next_ty_var_with_default(&self,
1025 default: Option<type_variable::Default<'tcx>>) -> Ty<'tcx> {
1026 let ty_var_id = self.type_variables
1028 .new_var(false, default);
1030 self.tcx.mk_var(ty_var_id)
1033 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
1034 self.tcx.mk_var(self.next_ty_var_id(true))
1037 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
1038 (0..n).map(|_i| self.next_ty_var()).collect()
1041 pub fn next_int_var_id(&self) -> IntVid {
1042 self.int_unification_table
1047 pub fn next_float_var_id(&self) -> FloatVid {
1048 self.float_unification_table
1053 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region {
1054 ty::ReVar(self.region_vars.new_region_var(origin))
1057 pub fn region_vars_for_defs(&self,
1059 defs: &[ty::RegionParameterDef])
1060 -> Vec<ty::Region> {
1062 .map(|d| self.next_region_var(EarlyBoundRegion(span, d.name)))
1066 // We have to take `&mut Substs` in order to provide the correct substitutions for defaults
1067 // along the way, for this reason we don't return them.
1068 pub fn type_vars_for_defs(&self,
1070 space: subst::ParamSpace,
1071 substs: &mut Substs<'tcx>,
1072 defs: &[ty::TypeParameterDef<'tcx>]) {
1074 let mut vars = Vec::with_capacity(defs.len());
1076 for def in defs.iter() {
1077 let default = def.default.map(|default| {
1078 type_variable::Default {
1079 ty: default.subst_spanned(self.tcx, substs, Some(span)),
1081 def_id: def.default_def_id
1085 let ty_var = self.next_ty_var_with_default(default);
1086 substs.types.push(space, ty_var);
1091 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1092 /// type/region parameter to a fresh inference variable.
1093 pub fn fresh_substs_for_generics(&self,
1095 generics: &ty::Generics<'tcx>)
1096 -> subst::Substs<'tcx>
1098 let type_params = subst::VecPerParamSpace::empty();
1101 generics.regions.map(
1102 |d| self.next_region_var(EarlyBoundRegion(span, d.name)));
1104 let mut substs = subst::Substs::new(type_params, region_params);
1106 for space in subst::ParamSpace::all().iter() {
1107 self.type_vars_for_defs(
1111 generics.types.get_slice(*space));
1117 /// Given a set of generics defined on a trait, returns a substitution mapping each output
1118 /// type/region parameter to a fresh inference variable, and mapping the self type to
1120 pub fn fresh_substs_for_trait(&self,
1122 generics: &ty::Generics<'tcx>,
1124 -> subst::Substs<'tcx>
1127 assert!(generics.types.len(subst::SelfSpace) == 1);
1128 assert!(generics.types.len(subst::FnSpace) == 0);
1129 assert!(generics.regions.len(subst::SelfSpace) == 0);
1130 assert!(generics.regions.len(subst::FnSpace) == 0);
1132 let type_params = Vec::new();
1134 let region_param_defs = generics.regions.get_slice(subst::TypeSpace);
1135 let regions = self.region_vars_for_defs(span, region_param_defs);
1137 let mut substs = subst::Substs::new_trait(type_params, regions, self_ty);
1139 let type_parameter_defs = generics.types.get_slice(subst::TypeSpace);
1140 self.type_vars_for_defs(span, subst::TypeSpace, &mut substs, type_parameter_defs);
1145 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {
1146 self.region_vars.new_bound(debruijn)
1149 /// Apply `adjustment` to the type of `expr`
1150 pub fn adjust_expr_ty(&self,
1152 adjustment: Option<&ty::AutoAdjustment<'tcx>>)
1155 let raw_ty = self.expr_ty(expr);
1156 let raw_ty = self.shallow_resolve(raw_ty);
1157 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1158 raw_ty.adjust(self.tcx,
1162 |method_call| self.tables
1166 .map(|method| resolve_ty(method.ty)))
1169 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1170 match self.tables.borrow().node_types.get(&id) {
1173 None if self.tcx.sess.err_count() - self.err_count_on_creation != 0 =>
1177 &format!("no type for node {}: {} in fcx",
1178 id, self.tcx.map.node_to_string(id)));
1183 pub fn expr_ty(&self, ex: &hir::Expr) -> Ty<'tcx> {
1184 match self.tables.borrow().node_types.get(&ex.id) {
1187 self.tcx.sess.bug(&format!("no type for expr in fcx"));
1192 pub fn resolve_regions_and_report_errors(&self,
1193 free_regions: &FreeRegionMap,
1194 subject_node_id: ast::NodeId) {
1195 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1196 self.report_region_errors(&errors); // see error_reporting.rs
1199 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1200 self.resolve_type_vars_if_possible(&t).to_string()
1203 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1204 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1205 format!("({})", tstrs.join(", "))
1208 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1209 self.resolve_type_vars_if_possible(t).to_string()
1212 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1214 ty::TyInfer(ty::TyVar(v)) => {
1215 // Not entirely obvious: if `typ` is a type variable,
1216 // it can be resolved to an int/float variable, which
1217 // can then be recursively resolved, hence the
1218 // recursion. Note though that we prevent type
1219 // variables from unifying to other type variables
1220 // directly (though they may be embedded
1221 // structurally), and we prevent cycles in any case,
1222 // so this recursion should always be of very limited
1224 self.type_variables.borrow()
1226 .map(|t| self.shallow_resolve(t))
1230 ty::TyInfer(ty::IntVar(v)) => {
1231 self.int_unification_table
1234 .map(|v| v.to_type(self.tcx))
1238 ty::TyInfer(ty::FloatVar(v)) => {
1239 self.float_unification_table
1242 .map(|v| v.to_type(self.tcx))
1252 pub fn resolve_type_vars_if_possible<T>(&self, value: &T) -> T
1253 where T: TypeFoldable<'tcx> + HasTypeFlags
1256 * Where possible, replaces type/int/float variables in
1257 * `value` with their final value. Note that region variables
1258 * are unaffected. If a type variable has not been unified, it
1259 * is left as is. This is an idempotent operation that does
1260 * not affect inference state in any way and so you can do it
1264 if !value.needs_infer() {
1265 return value.clone(); // avoid duplicated subst-folding
1267 let mut r = resolve::OpportunisticTypeResolver::new(self);
1268 value.fold_with(&mut r)
1271 /// Resolves all type variables in `t` and then, if any were left
1272 /// unresolved, substitutes an error type. This is used after the
1273 /// main checking when doing a second pass before writeback. The
1274 /// justification is that writeback will produce an error for
1275 /// these unconstrained type variables.
1276 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1277 let ty = self.resolve_type_vars_if_possible(t);
1278 if ty.references_error() || ty.is_ty_var() {
1279 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1286 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1288 * Attempts to resolve all type/region variables in
1289 * `value`. Region inference must have been run already (e.g.,
1290 * by calling `resolve_regions_and_report_errors`). If some
1291 * variable was never unified, an `Err` results.
1293 * This method is idempotent, but it not typically not invoked
1294 * except during the writeback phase.
1297 resolve::fully_resolve(self, value)
1300 // [Note-Type-error-reporting]
1301 // An invariant is that anytime the expected or actual type is TyError (the special
1302 // error type, meaning that an error occurred when typechecking this expression),
1303 // this is a derived error. The error cascaded from another error (that was already
1304 // reported), so it's not useful to display it to the user.
1305 // The following four methods -- type_error_message_str, type_error_message_str_with_expected,
1306 // type_error_message, and report_mismatched_types -- implement this logic.
1307 // They check if either the actual or expected type is TyError, and don't print the error
1308 // in this case. The typechecker should only ever report type errors involving mismatched
1309 // types using one of these four methods, and should not call span_err directly for such
1311 pub fn type_error_message_str<M>(&self,
1315 err: Option<&ty::TypeError<'tcx>>) where
1316 M: FnOnce(Option<String>, String) -> String,
1318 self.type_error_message_str_with_expected(sp, mk_msg, None, actual_ty, err)
1321 pub fn type_error_message_str_with_expected<M>(&self,
1324 expected_ty: Option<Ty<'tcx>>,
1326 err: Option<&ty::TypeError<'tcx>>) where
1327 M: FnOnce(Option<String>, String) -> String,
1329 debug!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
1331 let resolved_expected = expected_ty.map(|e_ty| self.resolve_type_vars_if_possible(&e_ty));
1333 if !resolved_expected.references_error() {
1334 let error_str = err.map_or("".to_string(), |t_err| {
1335 format!(" ({})", t_err)
1338 self.tcx.sess.span_err(sp, &format!("{}{}",
1339 mk_msg(resolved_expected.map(|t| self.ty_to_string(t)), actual_ty),
1342 if let Some(err) = err {
1343 self.tcx.note_and_explain_type_err(err, sp)
1348 pub fn type_error_message<M>(&self,
1351 actual_ty: Ty<'tcx>,
1352 err: Option<&ty::TypeError<'tcx>>) where
1353 M: FnOnce(String) -> String,
1355 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1357 // Don't report an error if actual type is TyError.
1358 if actual_ty.references_error() {
1362 self.type_error_message_str(sp,
1363 move |_e, a| { mk_msg(a) },
1364 self.ty_to_string(actual_ty), err);
1367 pub fn report_mismatched_types(&self,
1371 err: &ty::TypeError<'tcx>) {
1372 let trace = TypeTrace {
1374 values: Types(ty::ExpectedFound {
1379 self.report_and_explain_type_error(trace, err);
1382 pub fn report_conflicting_default_types(&self,
1384 expected: type_variable::Default<'tcx>,
1385 actual: type_variable::Default<'tcx>) {
1386 let trace = TypeTrace {
1388 values: Types(ty::ExpectedFound {
1389 expected: expected.ty,
1394 self.report_and_explain_type_error(trace,
1395 &TypeError::TyParamDefaultMismatch(ty::ExpectedFound {
1401 pub fn replace_late_bound_regions_with_fresh_var<T>(
1404 lbrct: LateBoundRegionConversionTime,
1405 value: &ty::Binder<T>)
1406 -> (T, FnvHashMap<ty::BoundRegion,ty::Region>)
1407 where T : TypeFoldable<'tcx>
1409 ty_fold::replace_late_bound_regions(
1412 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1415 /// See `verify_generic_bound` method in `region_inference`
1416 pub fn verify_generic_bound(&self,
1417 origin: SubregionOrigin<'tcx>,
1418 kind: GenericKind<'tcx>,
1420 bound: VerifyBound) {
1421 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1426 self.region_vars.verify_generic_bound(origin, kind, a, bound);
1429 pub fn can_equate<'b,T>(&'b self, a: &T, b: &T) -> UnitResult<'tcx>
1430 where T: Relate<'b,'tcx> + fmt::Debug
1432 debug!("can_equate({:?}, {:?})", a, b);
1434 // Gin up a dummy trace, since this won't be committed
1435 // anyhow. We should make this typetrace stuff more
1436 // generic so we don't have to do anything quite this
1438 let e = self.tcx.types.err;
1439 let trace = TypeTrace { origin: Misc(codemap::DUMMY_SP),
1440 values: Types(expected_found(true, e, e)) };
1441 self.equate(true, trace).relate(a, b)
1445 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1446 let ty = self.node_type(id);
1447 self.resolve_type_vars_or_error(&ty)
1450 pub fn expr_ty_adjusted(&self, expr: &hir::Expr) -> McResult<Ty<'tcx>> {
1451 let ty = self.adjust_expr_ty(expr, self.tables.borrow().adjustments.get(&expr.id));
1452 self.resolve_type_vars_or_error(&ty)
1455 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1456 let ty = self.resolve_type_vars_if_possible(&ty);
1457 if ty.needs_infer() {
1458 // this can get called from typeck (by euv), and moves_by_default
1459 // rightly refuses to work with inference variables, but
1460 // moves_by_default has a cache, which we want to use in other
1462 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1464 ty.moves_by_default(&self.parameter_environment, span)
1468 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1469 -> Option<Ty<'tcx>> {
1474 .map(|method| method.ty)
1475 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1478 pub fn node_method_id(&self, method_call: ty::MethodCall)
1484 .map(|method| method.def_id)
1487 pub fn adjustments(&self) -> Ref<NodeMap<ty::AutoAdjustment<'tcx>>> {
1488 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1489 -> &'a NodeMap<ty::AutoAdjustment<'tcx>> {
1493 Ref::map(self.tables.borrow(), project_adjustments)
1496 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1497 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1500 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1501 self.tcx.region_maps.temporary_scope(rvalue_id)
1504 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture> {
1505 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1508 pub fn param_env<'b>(&'b self) -> &'b ty::ParameterEnvironment<'b,'tcx> {
1509 &self.parameter_environment
1512 pub fn closure_kind(&self,
1514 -> Option<ty::ClosureKind>
1516 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1519 pub fn closure_type(&self,
1521 substs: &ty::ClosureSubsts<'tcx>)
1522 -> ty::ClosureTy<'tcx>
1524 let closure_ty = self.tables
1529 .subst(self.tcx, &substs.func_substs);
1532 normalize_associated_type(&self.tcx, &closure_ty)
1539 impl<'tcx> TypeTrace<'tcx> {
1540 pub fn span(&self) -> Span {
1544 pub fn types(origin: TypeOrigin,
1545 a_is_expected: bool,
1548 -> TypeTrace<'tcx> {
1551 values: Types(expected_found(a_is_expected, a, b))
1555 pub fn dummy(tcx: &ty::ctxt<'tcx>) -> TypeTrace<'tcx> {
1557 origin: Misc(codemap::DUMMY_SP),
1558 values: Types(ty::ExpectedFound {
1559 expected: tcx.types.err,
1560 found: tcx.types.err,
1566 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1567 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1568 write!(f, "TypeTrace({:?})", self.origin)
1573 pub fn span(&self) -> Span {
1575 MethodCompatCheck(span) => span,
1576 ExprAssignable(span) => span,
1578 RelateTraitRefs(span) => span,
1579 RelateSelfType(span) => span,
1580 RelateOutputImplTypes(span) => span,
1581 MatchExpressionArm(match_span, _) => match_span,
1582 IfExpression(span) => span,
1583 IfExpressionWithNoElse(span) => span,
1584 RangeExpression(span) => span,
1585 EquatePredicate(span) => span,
1590 impl<'tcx> SubregionOrigin<'tcx> {
1591 pub fn span(&self) -> Span {
1593 RFC1214Subregion(ref a) => a.span(),
1594 Subtype(ref a) => a.span(),
1595 InfStackClosure(a) => a,
1596 InvokeClosure(a) => a,
1597 DerefPointer(a) => a,
1598 FreeVariable(a, _) => a,
1600 RelateObjectBound(a) => a,
1601 RelateParamBound(a, _) => a,
1602 RelateRegionParamBound(a) => a,
1603 RelateDefaultParamBound(a, _) => a,
1605 ReborrowUpvar(a, _) => a,
1606 DataBorrowed(_, a) => a,
1607 ReferenceOutlivesReferent(_, a) => a,
1608 ParameterInScope(_, a) => a,
1609 ExprTypeIsNotInScope(_, a) => a,
1610 BindingTypeIsNotValidAtDecl(a) => a,
1617 SafeDestructor(a) => a,
1622 impl RegionVariableOrigin {
1623 pub fn span(&self) -> Span {
1625 MiscVariable(a) => a,
1626 PatternRegion(a) => a,
1627 AddrOfRegion(a) => a,
1630 EarlyBoundRegion(a, _) => a,
1631 LateBoundRegion(a, _, _) => a,
1632 BoundRegionInCoherence(_) => codemap::DUMMY_SP,
1633 UpvarRegion(_, a) => a