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;
22 use middle::free_region::FreeRegionMap;
23 use middle::mem_categorization as mc;
24 use middle::mem_categorization::McResult;
25 use middle::region::CodeExtent;
27 use middle::subst::Substs;
28 use middle::subst::Subst;
29 use middle::traits::{self, FulfillmentContext, Normalized,
30 SelectionContext, ObligationCause};
31 use middle::ty::{TyVid, IntVid, FloatVid, RegionVid, UnconstrainedNumeric};
32 use middle::ty::{self, Ty, TypeError, HasTypeFlags};
33 use middle::ty_fold::{self, TypeFolder, TypeFoldable};
34 use middle::ty_relate::{Relate, RelateResult, TypeRelation};
35 use rustc_data_structures::unify::{self, UnificationTable};
36 use std::cell::{RefCell, Ref};
40 use syntax::codemap::{Span, DUMMY_SP};
41 use util::nodemap::{FnvHashMap, NodeMap};
44 use self::combine::CombineFields;
45 use self::region_inference::{RegionVarBindings, RegionSnapshot};
46 use self::error_reporting::ErrorReporting;
47 use self::unify_key::ToType;
52 pub mod error_reporting;
57 pub mod region_inference;
61 pub mod type_variable;
64 pub type Bound<T> = Option<T>;
65 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
66 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
68 pub struct InferCtxt<'a, 'tcx: 'a> {
69 pub tcx: &'a ty::ctxt<'tcx>,
71 pub tables: &'a RefCell<ty::Tables<'tcx>>,
73 // We instantiate UnificationTable with bounds<Ty> because the
74 // types that might instantiate a general type variable have an
75 // order, represented by its upper and lower bounds.
76 pub type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
78 // Map from integral variable to the kind of integer it represents
79 int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
81 // Map from floating variable to the kind of float it represents
82 float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
84 // For region variables.
85 region_vars: RegionVarBindings<'a, 'tcx>,
87 pub parameter_environment: ty::ParameterEnvironment<'a, 'tcx>,
89 pub fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
91 // This is a temporary field used for toggling on normalization in the inference context,
92 // as we move towards the approach described here:
93 // https://internals.rust-lang.org/t/flattening-the-contexts-for-fun-and-profit/2293
94 // At a point sometime in the future normalization will be done by the typing context
98 err_count_on_creation: usize,
101 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
102 /// region that each late-bound region was replaced with.
103 pub type SkolemizationMap = FnvHashMap<ty::BoundRegion,ty::Region>;
105 /// Why did we require that the two types be related?
107 /// See `error_reporting.rs` for more details
108 #[derive(Clone, Copy, Debug)]
109 pub enum TypeOrigin {
110 // Not yet categorized in a better way
113 // Checking that method of impl is compatible with trait
114 MethodCompatCheck(Span),
116 // Checking that this expression can be assigned where it needs to be
117 // FIXME(eddyb) #11161 is the original Expr required?
118 ExprAssignable(Span),
120 // Relating trait refs when resolving vtables
121 RelateTraitRefs(Span),
123 // Relating self types when resolving vtables
124 RelateSelfType(Span),
126 // Relating trait type parameters to those found in impl etc
127 RelateOutputImplTypes(Span),
129 // Computing common supertype in the arms of a match expression
130 MatchExpressionArm(Span, Span),
132 // Computing common supertype in an if expression
135 // Computing common supertype of an if expression with no else counter-part
136 IfExpressionWithNoElse(Span),
138 // Computing common supertype in a range expression
139 RangeExpression(Span),
142 EquatePredicate(Span),
146 fn as_str(&self) -> &'static str {
148 &TypeOrigin::Misc(_) |
149 &TypeOrigin::RelateSelfType(_) |
150 &TypeOrigin::RelateOutputImplTypes(_) |
151 &TypeOrigin::ExprAssignable(_) => "mismatched types",
152 &TypeOrigin::RelateTraitRefs(_) => "mismatched traits",
153 &TypeOrigin::MethodCompatCheck(_) => "method not compatible with trait",
154 &TypeOrigin::MatchExpressionArm(_, _) => "match arms have incompatible types",
155 &TypeOrigin::IfExpression(_) => "if and else have incompatible types",
156 &TypeOrigin::IfExpressionWithNoElse(_) => "if may be missing an else clause",
157 &TypeOrigin::RangeExpression(_) => "start and end of range have incompatible types",
158 &TypeOrigin::EquatePredicate(_) => "equality predicate not satisfied",
163 impl fmt::Display for TypeOrigin {
164 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error> {
165 fmt::Display::fmt(self.as_str(), f)
169 /// See `error_reporting.rs` for more details
170 #[derive(Clone, Debug)]
171 pub enum ValuePairs<'tcx> {
172 Types(ty::ExpectedFound<Ty<'tcx>>),
173 TraitRefs(ty::ExpectedFound<ty::TraitRef<'tcx>>),
174 PolyTraitRefs(ty::ExpectedFound<ty::PolyTraitRef<'tcx>>),
177 /// The trace designates the path through inference that we took to
178 /// encounter an error or subtyping constraint.
180 /// See `error_reporting.rs` for more details.
182 pub struct TypeTrace<'tcx> {
184 values: ValuePairs<'tcx>,
187 /// The origin of a `r1 <= r2` constraint.
189 /// See `error_reporting.rs` for more details
190 #[derive(Clone, Debug)]
191 pub enum SubregionOrigin<'tcx> {
192 // Arose from a subtyping relation
193 Subtype(TypeTrace<'tcx>),
195 // Stack-allocated closures cannot outlive innermost loop
196 // or function so as to ensure we only require finite stack
197 InfStackClosure(Span),
199 // Invocation of closure must be within its lifetime
202 // Dereference of reference must be within its lifetime
205 // Closure bound must not outlive captured free variables
206 FreeVariable(Span, ast::NodeId),
208 // Index into slice must be within its lifetime
211 // When casting `&'a T` to an `&'b Trait` object,
212 // relating `'a` to `'b`
213 RelateObjectBound(Span),
215 // Some type parameter was instantiated with the given type,
216 // and that type must outlive some region.
217 RelateParamBound(Span, Ty<'tcx>),
219 // The given region parameter was instantiated with a region
220 // that must outlive some other region.
221 RelateRegionParamBound(Span),
223 // A bound placed on type parameters that states that must outlive
224 // the moment of their instantiation.
225 RelateDefaultParamBound(Span, Ty<'tcx>),
227 // Creating a pointer `b` to contents of another reference
230 // Creating a pointer `b` to contents of an upvar
231 ReborrowUpvar(Span, ty::UpvarId),
233 // (&'a &'b T) where a >= b
234 ReferenceOutlivesReferent(Ty<'tcx>, Span),
236 // The type T of an expression E must outlive the lifetime for E.
237 ExprTypeIsNotInScope(Ty<'tcx>, Span),
239 // A `ref b` whose region does not enclose the decl site
240 BindingTypeIsNotValidAtDecl(Span),
242 // Regions appearing in a method receiver must outlive method call
245 // Regions appearing in a function argument must outlive func call
248 // Region in return type of invoked fn must enclose call
251 // Operands must be in scope
254 // Region resulting from a `&` expr must enclose the `&` expr
257 // An auto-borrow that does not enclose the expr where it occurs
260 // Region constraint arriving from destructor safety
261 SafeDestructor(Span),
264 /// Times when we replace late-bound regions with variables:
265 #[derive(Clone, Copy, Debug)]
266 pub enum LateBoundRegionConversionTime {
267 /// when a fn is called
270 /// when two higher-ranked types are compared
273 /// when projecting an associated type
274 AssocTypeProjection(ast::Name),
277 /// Reasons to create a region inference variable
279 /// See `error_reporting.rs` for more details
280 #[derive(Clone, Debug)]
281 pub enum RegionVariableOrigin {
282 // Region variables created for ill-categorized reasons,
283 // mostly indicates places in need of refactoring
286 // Regions created by a `&P` or `[...]` pattern
289 // Regions created by `&` operator
292 // Regions created as part of an autoref of a method receiver
295 // Regions created as part of an automatic coercion
298 // Region variables created as the values for early-bound regions
299 EarlyBoundRegion(Span, ast::Name),
301 // Region variables created for bound regions
302 // in a function or method that is called
303 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
305 UpvarRegion(ty::UpvarId, Span),
307 BoundRegionInCoherence(ast::Name),
310 #[derive(Copy, Clone, Debug)]
311 pub enum FixupError {
312 UnresolvedIntTy(IntVid),
313 UnresolvedFloatTy(FloatVid),
317 pub fn fixup_err_to_string(f: FixupError) -> String {
318 use self::FixupError::*;
321 UnresolvedIntTy(_) => {
322 "cannot determine the type of this integer; add a suffix to \
323 specify the type explicitly".to_string()
325 UnresolvedFloatTy(_) => {
326 "cannot determine the type of this number; add a suffix to specify \
327 the type explicitly".to_string()
329 UnresolvedTy(_) => "unconstrained type".to_string(),
333 /// errors_will_be_reported is required to proxy to the fulfillment context
334 /// FIXME -- a better option would be to hold back on modifying
335 /// the global cache until we know that all dependent obligations
336 /// are also satisfied. In that case, we could actually remove
337 /// this boolean flag, and we'd also avoid the problem of squelching
338 /// duplicate errors that occur across fns.
339 pub fn new_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
340 tables: &'a RefCell<ty::Tables<'tcx>>,
341 param_env: Option<ty::ParameterEnvironment<'a, 'tcx>>,
342 errors_will_be_reported: bool)
343 -> InferCtxt<'a, 'tcx> {
347 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
348 int_unification_table: RefCell::new(UnificationTable::new()),
349 float_unification_table: RefCell::new(UnificationTable::new()),
350 region_vars: RegionVarBindings::new(tcx),
351 parameter_environment: param_env.unwrap_or(tcx.empty_parameter_environment()),
352 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new(errors_will_be_reported)),
354 err_count_on_creation: tcx.sess.err_count()
358 pub fn normalizing_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
359 tables: &'a RefCell<ty::Tables<'tcx>>)
360 -> InferCtxt<'a, 'tcx> {
361 let mut infcx = new_infer_ctxt(tcx, tables, None, false);
362 infcx.normalize = true;
366 /// Computes the least upper-bound of `a` and `b`. If this is not possible, reports an error and
368 pub fn common_supertype<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
375 debug!("common_supertype({:?}, {:?})",
378 let trace = TypeTrace {
380 values: Types(expected_found(a_is_expected, a, b))
383 let result = cx.commit_if_ok(|_| cx.lub(a_is_expected, trace.clone()).relate(&a, &b));
387 cx.report_and_explain_type_error(trace, err);
393 pub fn mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
400 debug!("mk_subty({:?} <: {:?})", a, b);
401 cx.sub_types(a_is_expected, origin, a, b)
404 pub fn can_mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
407 -> UnitResult<'tcx> {
408 debug!("can_mk_subty({:?} <: {:?})", a, b);
410 let trace = TypeTrace {
411 origin: Misc(codemap::DUMMY_SP),
412 values: Types(expected_found(true, a, b))
414 cx.sub(true, trace).relate(&a, &b).map(|_| ())
418 pub fn can_mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>, a: Ty<'tcx>, b: Ty<'tcx>)
421 cx.can_equate(&a, &b)
424 pub fn mk_subr<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
425 origin: SubregionOrigin<'tcx>,
428 debug!("mk_subr({:?} <: {:?})", a, b);
429 let snapshot = cx.region_vars.start_snapshot();
430 cx.region_vars.make_subregion(origin, a, b);
431 cx.region_vars.commit(snapshot);
434 pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
441 debug!("mk_eqty({:?} <: {:?})", a, b);
442 cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
445 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
448 a: ty::PolyTraitRef<'tcx>,
449 b: ty::PolyTraitRef<'tcx>)
452 debug!("mk_sub_trait_refs({:?} <: {:?})",
454 cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
457 fn expected_found<T>(a_is_expected: bool,
460 -> ty::ExpectedFound<T>
463 ty::ExpectedFound {expected: a, found: b}
465 ty::ExpectedFound {expected: b, found: a}
469 #[must_use = "once you start a snapshot, you should always consume it"]
470 pub struct CombinedSnapshot {
471 type_snapshot: type_variable::Snapshot,
472 int_snapshot: unify::Snapshot<ty::IntVid>,
473 float_snapshot: unify::Snapshot<ty::FloatVid>,
474 region_vars_snapshot: RegionSnapshot,
477 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
478 where T : TypeFoldable<'tcx> + HasTypeFlags
480 debug!("normalize_associated_type(t={:?})", value);
482 let value = erase_regions(tcx, value);
484 if !value.has_projection_types() {
488 let infcx = new_infer_ctxt(tcx, &tcx.tables, None, true);
489 let mut selcx = traits::SelectionContext::new(&infcx);
490 let cause = traits::ObligationCause::dummy();
491 let traits::Normalized { value: result, obligations } =
492 traits::normalize(&mut selcx, cause, &value);
494 debug!("normalize_associated_type: result={:?} obligations={:?}",
498 let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
500 for obligation in obligations {
501 fulfill_cx.register_predicate_obligation(&infcx, obligation);
504 let result = drain_fulfillment_cx_or_panic(DUMMY_SP, &infcx, &mut fulfill_cx, &result);
509 pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
510 infcx: &InferCtxt<'a,'tcx>,
511 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
514 where T : TypeFoldable<'tcx>
516 match drain_fulfillment_cx(infcx, fulfill_cx, result) {
519 infcx.tcx.sess.span_bug(
521 &format!("Encountered errors `{:?}` fulfilling during trans",
527 /// Finishes processes any obligations that remain in the fulfillment
528 /// context, and then "freshens" and returns `result`. This is
529 /// primarily used during normalization and other cases where
530 /// processing the obligations in `fulfill_cx` may cause type
531 /// inference variables that appear in `result` to be unified, and
532 /// hence we need to process those obligations to get the complete
533 /// picture of the type.
534 pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
535 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
537 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
538 where T : TypeFoldable<'tcx>
540 debug!("drain_fulfillment_cx(result={:?})",
543 // In principle, we only need to do this so long as `result`
544 // contains unbound type parameters. It could be a slight
545 // optimization to stop iterating early.
546 match fulfill_cx.select_all_or_error(infcx) {
553 // Use freshen to simultaneously replace all type variables with
554 // their bindings and replace all regions with 'static. This is
555 // sort of overkill because we do not expect there to be any
556 // unbound type variables, hence no `TyFresh` types should ever be
558 Ok(result.fold_with(&mut infcx.freshener()))
561 /// Returns an equivalent value with all free regions removed (note
562 /// that late-bound regions remain, because they are important for
563 /// subtyping, but they are anonymized and normalized as well). This
564 /// is a stronger, caching version of `ty_fold::erase_regions`.
565 pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
566 where T : TypeFoldable<'tcx>
568 let value1 = value.fold_with(&mut RegionEraser(cx));
569 debug!("erase_regions({:?}) = {:?}",
573 struct RegionEraser<'a, 'tcx: 'a>(&'a ty::ctxt<'tcx>);
575 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
576 fn tcx(&self) -> &ty::ctxt<'tcx> { self.0 }
578 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
579 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
584 let t_norm = ty_fold::super_fold_ty(self, ty);
585 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
589 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
590 where T : TypeFoldable<'tcx>
592 let u = self.tcx().anonymize_late_bound_regions(t);
593 ty_fold::super_fold_binder(self, &u)
596 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
597 // because late-bound regions affect subtyping, we can't
598 // erase the bound/free distinction, but we can replace
599 // all free regions with 'static.
601 // Note that we *CAN* replace early-bound regions -- the
602 // type system never "sees" those, they get substituted
603 // away. In trans, they will always be erased to 'static
604 // whenever a substitution occurs.
606 ty::ReLateBound(..) => r,
611 fn fold_substs(&mut self,
612 substs: &subst::Substs<'tcx>)
613 -> subst::Substs<'tcx> {
614 subst::Substs { regions: subst::ErasedRegions,
615 types: substs.types.fold_with(self) }
620 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
621 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
622 t.fold_with(&mut self.freshener())
625 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
627 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
632 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
633 freshen::TypeFreshener::new(self)
636 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
637 use middle::ty::UnconstrainedNumeric::{Neither, UnconstrainedInt, UnconstrainedFloat};
639 ty::TyInfer(ty::IntVar(vid)) => {
640 if self.int_unification_table.borrow_mut().has_value(vid) {
646 ty::TyInfer(ty::FloatVar(vid)) => {
647 if self.float_unification_table.borrow_mut().has_value(vid) {
657 /// Returns a type variable's default fallback if any exists. A default
658 /// must be attached to the variable when created, if it is created
659 /// without a default, this will return None.
661 /// See `new_ty_var_with_default` to create a type variable with a default.
662 /// See `type_variable::Default` for details about what a default entails.
663 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
665 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
670 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
671 let mut variables = Vec::new();
673 let unbound_ty_vars = self.type_variables
675 .unsolved_variables()
677 .map(|t| self.tcx.mk_var(t));
679 let unbound_int_vars = self.int_unification_table
681 .unsolved_variables()
683 .map(|v| self.tcx.mk_int_var(v));
685 let unbound_float_vars = self.float_unification_table
687 .unsolved_variables()
689 .map(|v| self.tcx.mk_float_var(v));
691 variables.extend(unbound_ty_vars);
692 variables.extend(unbound_int_vars);
693 variables.extend(unbound_float_vars);
698 fn combine_fields(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
699 -> CombineFields<'a, 'tcx> {
700 CombineFields {infcx: self,
701 a_is_expected: a_is_expected,
706 // public so that it can be used from the rustc_driver unit tests
707 pub fn equate(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
708 -> equate::Equate<'a, 'tcx>
710 self.combine_fields(a_is_expected, trace).equate()
713 // public so that it can be used from the rustc_driver unit tests
714 pub fn sub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
715 -> sub::Sub<'a, 'tcx>
717 self.combine_fields(a_is_expected, trace).sub()
720 // public so that it can be used from the rustc_driver unit tests
721 pub fn lub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
722 -> lub::Lub<'a, 'tcx>
724 self.combine_fields(a_is_expected, trace).lub()
727 // public so that it can be used from the rustc_driver unit tests
728 pub fn glb(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
729 -> glb::Glb<'a, 'tcx>
731 self.combine_fields(a_is_expected, trace).glb()
734 fn start_snapshot(&self) -> CombinedSnapshot {
736 type_snapshot: self.type_variables.borrow_mut().snapshot(),
737 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
738 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
739 region_vars_snapshot: self.region_vars.start_snapshot(),
743 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
744 debug!("rollback_to(cause={})", cause);
745 let CombinedSnapshot { type_snapshot,
748 region_vars_snapshot } = snapshot;
752 .rollback_to(type_snapshot);
753 self.int_unification_table
755 .rollback_to(int_snapshot);
756 self.float_unification_table
758 .rollback_to(float_snapshot);
760 .rollback_to(region_vars_snapshot);
763 fn commit_from(&self, snapshot: CombinedSnapshot) {
764 debug!("commit_from!");
765 let CombinedSnapshot { type_snapshot,
768 region_vars_snapshot } = snapshot;
772 .commit(type_snapshot);
773 self.int_unification_table
775 .commit(int_snapshot);
776 self.float_unification_table
778 .commit(float_snapshot);
780 .commit(region_vars_snapshot);
783 /// Execute `f` and commit the bindings
784 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
788 let snapshot = self.start_snapshot();
790 self.commit_from(snapshot);
794 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
795 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
796 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
798 debug!("commit_if_ok()");
799 let snapshot = self.start_snapshot();
800 let r = f(&snapshot);
801 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
803 Ok(_) => { self.commit_from(snapshot); }
804 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
809 /// Execute `f` and commit only the region bindings if successful.
810 /// The function f must be very careful not to leak any non-region
811 /// variables that get created.
812 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
813 F: FnOnce() -> Result<T, E>
815 debug!("commit_regions_if_ok()");
816 let CombinedSnapshot { type_snapshot,
819 region_vars_snapshot } = self.start_snapshot();
821 let r = self.commit_if_ok(|_| f());
823 debug!("commit_regions_if_ok: rolling back everything but regions");
825 // Roll back any non-region bindings - they should be resolved
826 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
829 .rollback_to(type_snapshot);
830 self.int_unification_table
832 .rollback_to(int_snapshot);
833 self.float_unification_table
835 .rollback_to(float_snapshot);
837 // Commit region vars that may escape through resolved types.
839 .commit(region_vars_snapshot);
844 /// Execute `f` then unroll any bindings it creates
845 pub fn probe<R, F>(&self, f: F) -> R where
846 F: FnOnce(&CombinedSnapshot) -> R,
849 let snapshot = self.start_snapshot();
850 let r = f(&snapshot);
851 self.rollback_to("probe", snapshot);
855 pub fn add_given(&self,
859 self.region_vars.add_given(sub, sup);
862 pub fn sub_types(&self,
869 debug!("sub_types({:?} <: {:?})", a, b);
870 self.commit_if_ok(|_| {
871 let trace = TypeTrace::types(origin, a_is_expected, a, b);
872 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
876 pub fn eq_types(&self,
883 self.commit_if_ok(|_| {
884 let trace = TypeTrace::types(origin, a_is_expected, a, b);
885 self.equate(a_is_expected, trace).relate(&a, &b).map(|_| ())
889 pub fn sub_trait_refs(&self,
892 a: ty::TraitRef<'tcx>,
893 b: ty::TraitRef<'tcx>)
896 debug!("sub_trait_refs({:?} <: {:?})",
899 self.commit_if_ok(|_| {
900 let trace = TypeTrace {
902 values: TraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
904 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
908 pub fn sub_poly_trait_refs(&self,
911 a: ty::PolyTraitRef<'tcx>,
912 b: ty::PolyTraitRef<'tcx>)
915 debug!("sub_poly_trait_refs({:?} <: {:?})",
918 self.commit_if_ok(|_| {
919 let trace = TypeTrace {
921 values: PolyTraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
923 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
927 pub fn construct_skolemized_subst(&self,
928 generics: &ty::Generics<'tcx>,
929 snapshot: &CombinedSnapshot)
930 -> (subst::Substs<'tcx>, SkolemizationMap) {
931 /*! See `higher_ranked::construct_skolemized_subst` */
933 higher_ranked::construct_skolemized_substs(self, generics, snapshot)
936 pub fn skolemize_late_bound_regions<T>(&self,
937 value: &ty::Binder<T>,
938 snapshot: &CombinedSnapshot)
939 -> (T, SkolemizationMap)
940 where T : TypeFoldable<'tcx>
942 /*! See `higher_ranked::skolemize_late_bound_regions` */
944 higher_ranked::skolemize_late_bound_regions(self, value, snapshot)
947 pub fn leak_check(&self,
948 skol_map: &SkolemizationMap,
949 snapshot: &CombinedSnapshot)
952 /*! See `higher_ranked::leak_check` */
954 match higher_ranked::leak_check(self, skol_map, snapshot) {
956 Err((br, r)) => Err(TypeError::RegionsInsufficientlyPolymorphic(br, r))
960 pub fn plug_leaks<T>(&self,
961 skol_map: SkolemizationMap,
962 snapshot: &CombinedSnapshot,
965 where T : TypeFoldable<'tcx>
967 /*! See `higher_ranked::plug_leaks` */
969 higher_ranked::plug_leaks(self, skol_map, snapshot, value)
972 pub fn equality_predicate(&self,
974 predicate: &ty::PolyEquatePredicate<'tcx>)
975 -> UnitResult<'tcx> {
976 self.commit_if_ok(|snapshot| {
977 let (ty::EquatePredicate(a, b), skol_map) =
978 self.skolemize_late_bound_regions(predicate, snapshot);
979 let origin = EquatePredicate(span);
980 let () = try!(mk_eqty(self, false, origin, a, b));
981 self.leak_check(&skol_map, snapshot)
985 pub fn region_outlives_predicate(&self,
987 predicate: &ty::PolyRegionOutlivesPredicate)
988 -> UnitResult<'tcx> {
989 self.commit_if_ok(|snapshot| {
990 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
991 self.skolemize_late_bound_regions(predicate, snapshot);
992 let origin = RelateRegionParamBound(span);
993 let () = mk_subr(self, origin, r_b, r_a); // `b : a` ==> `a <= b`
994 self.leak_check(&skol_map, snapshot)
998 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
1001 .new_var(diverging, None)
1004 pub fn next_ty_var(&self) -> Ty<'tcx> {
1005 self.tcx.mk_var(self.next_ty_var_id(false))
1008 pub fn next_ty_var_with_default(&self,
1009 default: Option<type_variable::Default<'tcx>>) -> Ty<'tcx> {
1010 let ty_var_id = self.type_variables
1012 .new_var(false, default);
1014 self.tcx.mk_var(ty_var_id)
1017 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
1018 self.tcx.mk_var(self.next_ty_var_id(true))
1021 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
1022 (0..n).map(|_i| self.next_ty_var()).collect()
1025 pub fn next_int_var_id(&self) -> IntVid {
1026 self.int_unification_table
1031 pub fn next_float_var_id(&self) -> FloatVid {
1032 self.float_unification_table
1037 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region {
1038 ty::ReInfer(ty::ReVar(self.region_vars.new_region_var(origin)))
1041 pub fn region_vars_for_defs(&self,
1043 defs: &[ty::RegionParameterDef])
1044 -> Vec<ty::Region> {
1046 .map(|d| self.next_region_var(EarlyBoundRegion(span, d.name)))
1050 pub fn type_vars_for_defs(&self,
1053 defs: &[ty::TypeParameterDef<'tcx>])
1054 -> Vec<ty::Ty<'tcx>> {
1056 fn definition_span<'tcx>(tcx: &ty::ctxt<'tcx>, def_id: ast::DefId) -> Span {
1057 let parent = tcx.map.get_parent(def_id.node);
1058 debug!("definition_span def_id={:?} parent={:?} node={:?} parent_node={:?}",
1059 def_id, parent, tcx.map.find(def_id.node), tcx.map.find(parent));
1060 match tcx.map.find(parent) {
1062 Some(ref node) => match *node {
1063 ast_map::NodeItem(ref item) => item.span,
1064 ast_map::NodeForeignItem(ref item) => item.span,
1065 ast_map::NodeTraitItem(ref item) => item.span,
1066 ast_map::NodeImplItem(ref item) => item.span,
1072 let mut substs = Substs::empty();
1073 let mut vars = Vec::with_capacity(defs.len());
1075 for def in defs.iter() {
1076 let default = def.default.map(|default| {
1077 type_variable::Default {
1080 definition_span: definition_span(self.tcx, def.def_id)
1083 //.subst(self.tcx, &substs)
1084 let ty_var = self.next_ty_var_with_default(default);
1085 substs.types.push(subst::ParamSpace::SelfSpace, ty_var);
1092 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1093 /// type/region parameter to a fresh inference variable.
1094 pub fn fresh_substs_for_generics(&self,
1096 generics: &ty::Generics<'tcx>)
1097 -> subst::Substs<'tcx>
1099 let mut type_params = subst::VecPerParamSpace::empty();
1101 for space in subst::ParamSpace::all().iter() {
1102 type_params.replace(*space,
1103 self.type_vars_for_defs(span, generics.types.get_slice(*space)))
1107 generics.regions.map(
1108 |d| self.next_region_var(EarlyBoundRegion(span, d.name)));
1109 subst::Substs::new(type_params, region_params)
1112 /// Given a set of generics defined on a trait, returns a substitution mapping each output
1113 /// type/region parameter to a fresh inference variable, and mapping the self type to
1115 pub fn fresh_substs_for_trait(&self,
1117 generics: &ty::Generics<'tcx>,
1119 -> subst::Substs<'tcx>
1122 assert!(generics.types.len(subst::SelfSpace) == 1);
1123 assert!(generics.types.len(subst::FnSpace) == 0);
1124 assert!(generics.regions.len(subst::SelfSpace) == 0);
1125 assert!(generics.regions.len(subst::FnSpace) == 0);
1127 let type_parameter_defs = generics.types.get_slice(subst::TypeSpace);
1128 let type_parameters = self.type_vars_for_defs(span, type_parameter_defs);
1130 let region_param_defs = generics.regions.get_slice(subst::TypeSpace);
1131 let regions = self.region_vars_for_defs(span, region_param_defs);
1133 subst::Substs::new_trait(type_parameters, regions, self_ty)
1136 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {
1137 self.region_vars.new_bound(debruijn)
1140 /// Apply `adjustment` to the type of `expr`
1141 pub fn adjust_expr_ty(&self,
1143 adjustment: Option<&ty::AutoAdjustment<'tcx>>)
1146 let raw_ty = self.expr_ty(expr);
1147 let raw_ty = self.shallow_resolve(raw_ty);
1148 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1149 raw_ty.adjust(self.tcx,
1153 |method_call| self.tables
1157 .map(|method| resolve_ty(method.ty)))
1160 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1161 match self.tables.borrow().node_types.get(&id) {
1164 None if self.tcx.sess.err_count() - self.err_count_on_creation != 0 =>
1168 &format!("no type for node {}: {} in fcx",
1169 id, self.tcx.map.node_to_string(id)));
1174 pub fn expr_ty(&self, ex: &ast::Expr) -> Ty<'tcx> {
1175 match self.tables.borrow().node_types.get(&ex.id) {
1178 self.tcx.sess.bug(&format!("no type for expr in fcx"));
1183 pub fn resolve_regions_and_report_errors(&self,
1184 free_regions: &FreeRegionMap,
1185 subject_node_id: ast::NodeId) {
1186 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1187 self.report_region_errors(&errors); // see error_reporting.rs
1190 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1191 self.resolve_type_vars_if_possible(&t).to_string()
1194 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1195 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1196 format!("({})", tstrs.join(", "))
1199 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1200 self.resolve_type_vars_if_possible(t).to_string()
1203 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1205 ty::TyInfer(ty::TyVar(v)) => {
1206 // Not entirely obvious: if `typ` is a type variable,
1207 // it can be resolved to an int/float variable, which
1208 // can then be recursively resolved, hence the
1209 // recursion. Note though that we prevent type
1210 // variables from unifying to other type variables
1211 // directly (though they may be embedded
1212 // structurally), and we prevent cycles in any case,
1213 // so this recursion should always be of very limited
1215 self.type_variables.borrow()
1217 .map(|t| self.shallow_resolve(t))
1221 ty::TyInfer(ty::IntVar(v)) => {
1222 self.int_unification_table
1225 .map(|v| v.to_type(self.tcx))
1229 ty::TyInfer(ty::FloatVar(v)) => {
1230 self.float_unification_table
1233 .map(|v| v.to_type(self.tcx))
1243 pub fn resolve_type_vars_if_possible<T:TypeFoldable<'tcx>>(&self, value: &T) -> T {
1245 * Where possible, replaces type/int/float variables in
1246 * `value` with their final value. Note that region variables
1247 * are unaffected. If a type variable has not been unified, it
1248 * is left as is. This is an idempotent operation that does
1249 * not affect inference state in any way and so you can do it
1253 let mut r = resolve::OpportunisticTypeResolver::new(self);
1254 value.fold_with(&mut r)
1257 /// Resolves all type variables in `t` and then, if any were left
1258 /// unresolved, substitutes an error type. This is used after the
1259 /// main checking when doing a second pass before writeback. The
1260 /// justification is that writeback will produce an error for
1261 /// these unconstrained type variables.
1262 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1263 let ty = self.resolve_type_vars_if_possible(t);
1264 if ty.references_error() || ty.is_ty_var() {
1265 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1272 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1274 * Attempts to resolve all type/region variables in
1275 * `value`. Region inference must have been run already (e.g.,
1276 * by calling `resolve_regions_and_report_errors`). If some
1277 * variable was never unified, an `Err` results.
1279 * This method is idempotent, but it not typically not invoked
1280 * except during the writeback phase.
1283 resolve::fully_resolve(self, value)
1286 // [Note-Type-error-reporting]
1287 // An invariant is that anytime the expected or actual type is TyError (the special
1288 // error type, meaning that an error occurred when typechecking this expression),
1289 // this is a derived error. The error cascaded from another error (that was already
1290 // reported), so it's not useful to display it to the user.
1291 // The following four methods -- type_error_message_str, type_error_message_str_with_expected,
1292 // type_error_message, and report_mismatched_types -- implement this logic.
1293 // They check if either the actual or expected type is TyError, and don't print the error
1294 // in this case. The typechecker should only ever report type errors involving mismatched
1295 // types using one of these four methods, and should not call span_err directly for such
1297 pub fn type_error_message_str<M>(&self,
1301 err: Option<&ty::TypeError<'tcx>>) where
1302 M: FnOnce(Option<String>, String) -> String,
1304 self.type_error_message_str_with_expected(sp, mk_msg, None, actual_ty, err)
1307 pub fn type_error_message_str_with_expected<M>(&self,
1310 expected_ty: Option<Ty<'tcx>>,
1312 err: Option<&ty::TypeError<'tcx>>) where
1313 M: FnOnce(Option<String>, String) -> String,
1315 debug!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
1317 let resolved_expected = expected_ty.map(|e_ty| self.resolve_type_vars_if_possible(&e_ty));
1319 if !resolved_expected.references_error() {
1320 let error_str = err.map_or("".to_string(), |t_err| {
1321 format!(" ({})", t_err)
1324 self.tcx.sess.span_err(sp, &format!("{}{}",
1325 mk_msg(resolved_expected.map(|t| self.ty_to_string(t)), actual_ty),
1328 if let Some(err) = err {
1329 self.tcx.note_and_explain_type_err(err, sp)
1334 pub fn type_error_message<M>(&self,
1337 actual_ty: Ty<'tcx>,
1338 err: Option<&ty::TypeError<'tcx>>) where
1339 M: FnOnce(String) -> String,
1341 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1343 // Don't report an error if actual type is TyError.
1344 if actual_ty.references_error() {
1348 self.type_error_message_str(sp,
1349 move |_e, a| { mk_msg(a) },
1350 self.ty_to_string(actual_ty), err);
1353 pub fn report_mismatched_types(&self,
1357 err: &ty::TypeError<'tcx>) {
1358 let trace = TypeTrace {
1360 values: Types(ty::ExpectedFound {
1365 self.report_and_explain_type_error(trace, err);
1368 pub fn report_conflicting_default_types(&self,
1370 expected: type_variable::Default<'tcx>,
1371 actual: type_variable::Default<'tcx>) {
1372 let trace = TypeTrace {
1374 values: Types(ty::expected_found {
1375 expected: expected.ty,
1380 self.report_and_explain_type_error(trace,
1381 &ty::type_err::terr_ty_param_default_mismatch(ty::expected_found {
1387 pub fn replace_late_bound_regions_with_fresh_var<T>(
1390 lbrct: LateBoundRegionConversionTime,
1391 value: &ty::Binder<T>)
1392 -> (T, FnvHashMap<ty::BoundRegion,ty::Region>)
1393 where T : TypeFoldable<'tcx>
1395 ty_fold::replace_late_bound_regions(
1398 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1401 /// See `verify_generic_bound` method in `region_inference`
1402 pub fn verify_generic_bound(&self,
1403 origin: SubregionOrigin<'tcx>,
1404 kind: GenericKind<'tcx>,
1406 bs: Vec<ty::Region>) {
1407 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1412 self.region_vars.verify_generic_bound(origin, kind, a, bs);
1415 pub fn can_equate<'b,T>(&'b self, a: &T, b: &T) -> UnitResult<'tcx>
1416 where T: Relate<'b,'tcx> + fmt::Debug
1418 debug!("can_equate({:?}, {:?})", a, b);
1420 // Gin up a dummy trace, since this won't be committed
1421 // anyhow. We should make this typetrace stuff more
1422 // generic so we don't have to do anything quite this
1424 let e = self.tcx.types.err;
1425 let trace = TypeTrace { origin: Misc(codemap::DUMMY_SP),
1426 values: Types(expected_found(true, e, e)) };
1427 self.equate(true, trace).relate(a, b)
1431 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1432 let ty = self.node_type(id);
1433 self.resolve_type_vars_or_error(&ty)
1436 pub fn expr_ty_adjusted(&self, expr: &ast::Expr) -> McResult<Ty<'tcx>> {
1437 let ty = self.adjust_expr_ty(expr, self.tables.borrow().adjustments.get(&expr.id));
1438 self.resolve_type_vars_or_error(&ty)
1441 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1442 let ty = self.resolve_type_vars_if_possible(&ty);
1443 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1444 // FIXME(@jroesch): should be able to use:
1445 // ty.moves_by_default(&self.parameter_environment, span)
1448 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1449 -> Option<Ty<'tcx>> {
1454 .map(|method| method.ty)
1455 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1458 pub fn node_method_id(&self, method_call: ty::MethodCall)
1459 -> Option<ast::DefId> {
1464 .map(|method| method.def_id)
1467 pub fn adjustments(&self) -> Ref<NodeMap<ty::AutoAdjustment<'tcx>>> {
1468 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1469 -> &'a NodeMap<ty::AutoAdjustment<'tcx>> {
1473 Ref::map(self.tables.borrow(), project_adjustments)
1476 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1477 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1480 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1481 self.tcx.region_maps.temporary_scope(rvalue_id)
1484 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture> {
1485 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1488 pub fn param_env<'b>(&'b self) -> &'b ty::ParameterEnvironment<'b,'tcx> {
1489 &self.parameter_environment
1492 pub fn closure_kind(&self,
1494 -> Option<ty::ClosureKind>
1496 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1499 pub fn closure_type(&self,
1501 substs: &ty::ClosureSubsts<'tcx>)
1502 -> ty::ClosureTy<'tcx>
1504 let closure_ty = self.tables
1509 .subst(self.tcx, &substs.func_substs);
1512 normalize_associated_type(&self.tcx, &closure_ty)
1519 impl<'tcx> TypeTrace<'tcx> {
1520 pub fn span(&self) -> Span {
1524 pub fn types(origin: TypeOrigin,
1525 a_is_expected: bool,
1528 -> TypeTrace<'tcx> {
1531 values: Types(expected_found(a_is_expected, a, b))
1535 pub fn dummy(tcx: &ty::ctxt<'tcx>) -> TypeTrace<'tcx> {
1537 origin: Misc(codemap::DUMMY_SP),
1538 values: Types(ty::ExpectedFound {
1539 expected: tcx.types.err,
1540 found: tcx.types.err,
1546 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1547 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1548 write!(f, "TypeTrace({:?})", self.origin)
1553 pub fn span(&self) -> Span {
1555 MethodCompatCheck(span) => span,
1556 ExprAssignable(span) => span,
1558 RelateTraitRefs(span) => span,
1559 RelateSelfType(span) => span,
1560 RelateOutputImplTypes(span) => span,
1561 MatchExpressionArm(match_span, _) => match_span,
1562 IfExpression(span) => span,
1563 IfExpressionWithNoElse(span) => span,
1564 RangeExpression(span) => span,
1565 EquatePredicate(span) => span,
1570 impl<'tcx> SubregionOrigin<'tcx> {
1571 pub fn span(&self) -> Span {
1573 Subtype(ref a) => a.span(),
1574 InfStackClosure(a) => a,
1575 InvokeClosure(a) => a,
1576 DerefPointer(a) => a,
1577 FreeVariable(a, _) => a,
1579 RelateObjectBound(a) => a,
1580 RelateParamBound(a, _) => a,
1581 RelateRegionParamBound(a) => a,
1582 RelateDefaultParamBound(a, _) => a,
1584 ReborrowUpvar(a, _) => a,
1585 ReferenceOutlivesReferent(_, a) => a,
1586 ExprTypeIsNotInScope(_, a) => a,
1587 BindingTypeIsNotValidAtDecl(a) => a,
1594 SafeDestructor(a) => a,
1599 impl RegionVariableOrigin {
1600 pub fn span(&self) -> Span {
1602 MiscVariable(a) => a,
1603 PatternRegion(a) => a,
1604 AddrOfRegion(a) => a,
1607 EarlyBoundRegion(a, _) => a,
1608 LateBoundRegion(a, _, _) => a,
1609 BoundRegionInCoherence(_) => codemap::DUMMY_SP,
1610 UpvarRegion(_, a) => a