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};
41 use syntax::codemap::{Span, DUMMY_SP};
42 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 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 RFC1214Subregion(Rc<SubregionOrigin<'tcx>>),
194 // Arose from a subtyping relation
195 Subtype(TypeTrace<'tcx>),
197 // Stack-allocated closures cannot outlive innermost loop
198 // or function so as to ensure we only require finite stack
199 InfStackClosure(Span),
201 // Invocation of closure must be within its lifetime
204 // Dereference of reference must be within its lifetime
207 // Closure bound must not outlive captured free variables
208 FreeVariable(Span, ast::NodeId),
210 // Index into slice must be within its lifetime
213 // When casting `&'a T` to an `&'b Trait` object,
214 // relating `'a` to `'b`
215 RelateObjectBound(Span),
217 // Some type parameter was instantiated with the given type,
218 // and that type must outlive some region.
219 RelateParamBound(Span, Ty<'tcx>),
221 // The given region parameter was instantiated with a region
222 // that must outlive some other region.
223 RelateRegionParamBound(Span),
225 // A bound placed on type parameters that states that must outlive
226 // the moment of their instantiation.
227 RelateDefaultParamBound(Span, Ty<'tcx>),
229 // Creating a pointer `b` to contents of another reference
232 // Creating a pointer `b` to contents of an upvar
233 ReborrowUpvar(Span, ty::UpvarId),
235 // Data with type `Ty<'tcx>` was borrowed
236 DataBorrowed(Ty<'tcx>, Span),
238 // (&'a &'b T) where a >= b
239 ReferenceOutlivesReferent(Ty<'tcx>, Span),
241 // Type or region parameters must be in scope.
242 ParameterInScope(ParameterOrigin, Span),
244 // The type T of an expression E must outlive the lifetime for E.
245 ExprTypeIsNotInScope(Ty<'tcx>, Span),
247 // A `ref b` whose region does not enclose the decl site
248 BindingTypeIsNotValidAtDecl(Span),
250 // Regions appearing in a method receiver must outlive method call
253 // Regions appearing in a function argument must outlive func call
256 // Region in return type of invoked fn must enclose call
259 // Operands must be in scope
262 // Region resulting from a `&` expr must enclose the `&` expr
265 // An auto-borrow that does not enclose the expr where it occurs
268 // Region constraint arriving from destructor safety
269 SafeDestructor(Span),
272 /// Places that type/region parameters can appear.
273 #[derive(Clone, Copy, Debug)]
274 pub enum ParameterOrigin {
276 MethodCall, // foo.bar() <-- parameters on impl providing bar()
277 OverloadedOperator, // a + b when overloaded
278 OverloadedDeref, // *a when overloaded
281 /// Times when we replace late-bound regions with variables:
282 #[derive(Clone, Copy, Debug)]
283 pub enum LateBoundRegionConversionTime {
284 /// when a fn is called
287 /// when two higher-ranked types are compared
290 /// when projecting an associated type
291 AssocTypeProjection(ast::Name),
294 /// Reasons to create a region inference variable
296 /// See `error_reporting.rs` for more details
297 #[derive(Clone, Debug)]
298 pub enum RegionVariableOrigin {
299 // Region variables created for ill-categorized reasons,
300 // mostly indicates places in need of refactoring
303 // Regions created by a `&P` or `[...]` pattern
306 // Regions created by `&` operator
309 // Regions created as part of an autoref of a method receiver
312 // Regions created as part of an automatic coercion
315 // Region variables created as the values for early-bound regions
316 EarlyBoundRegion(Span, ast::Name),
318 // Region variables created for bound regions
319 // in a function or method that is called
320 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
322 UpvarRegion(ty::UpvarId, Span),
324 BoundRegionInCoherence(ast::Name),
327 #[derive(Copy, Clone, Debug)]
328 pub enum FixupError {
329 UnresolvedIntTy(IntVid),
330 UnresolvedFloatTy(FloatVid),
334 pub fn fixup_err_to_string(f: FixupError) -> String {
335 use self::FixupError::*;
338 UnresolvedIntTy(_) => {
339 "cannot determine the type of this integer; add a suffix to \
340 specify the type explicitly".to_string()
342 UnresolvedFloatTy(_) => {
343 "cannot determine the type of this number; add a suffix to specify \
344 the type explicitly".to_string()
346 UnresolvedTy(_) => "unconstrained type".to_string(),
350 /// errors_will_be_reported is required to proxy to the fulfillment context
351 /// FIXME -- a better option would be to hold back on modifying
352 /// the global cache until we know that all dependent obligations
353 /// are also satisfied. In that case, we could actually remove
354 /// this boolean flag, and we'd also avoid the problem of squelching
355 /// duplicate errors that occur across fns.
356 pub fn new_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
357 tables: &'a RefCell<ty::Tables<'tcx>>,
358 param_env: Option<ty::ParameterEnvironment<'a, 'tcx>>,
359 errors_will_be_reported: bool)
360 -> InferCtxt<'a, 'tcx> {
364 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
365 int_unification_table: RefCell::new(UnificationTable::new()),
366 float_unification_table: RefCell::new(UnificationTable::new()),
367 region_vars: RegionVarBindings::new(tcx),
368 parameter_environment: param_env.unwrap_or(tcx.empty_parameter_environment()),
369 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new(errors_will_be_reported)),
371 err_count_on_creation: tcx.sess.err_count()
375 pub fn normalizing_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
376 tables: &'a RefCell<ty::Tables<'tcx>>)
377 -> InferCtxt<'a, 'tcx> {
378 let mut infcx = new_infer_ctxt(tcx, tables, None, false);
379 infcx.normalize = true;
383 /// Computes the least upper-bound of `a` and `b`. If this is not possible, reports an error and
385 pub fn common_supertype<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
392 debug!("common_supertype({:?}, {:?})",
395 let trace = TypeTrace {
397 values: Types(expected_found(a_is_expected, a, b))
400 let result = cx.commit_if_ok(|_| cx.lub(a_is_expected, trace.clone()).relate(&a, &b));
404 cx.report_and_explain_type_error(trace, err);
410 pub fn mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
417 debug!("mk_subty({:?} <: {:?})", a, b);
418 cx.sub_types(a_is_expected, origin, a, b)
421 pub fn can_mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
424 -> UnitResult<'tcx> {
425 debug!("can_mk_subty({:?} <: {:?})", a, b);
427 let trace = TypeTrace {
428 origin: Misc(codemap::DUMMY_SP),
429 values: Types(expected_found(true, a, b))
431 cx.sub(true, trace).relate(&a, &b).map(|_| ())
435 pub fn can_mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>, a: Ty<'tcx>, b: Ty<'tcx>)
438 cx.can_equate(&a, &b)
441 pub fn mk_subr<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
442 origin: SubregionOrigin<'tcx>,
445 debug!("mk_subr({:?} <: {:?})", a, b);
446 let snapshot = cx.region_vars.start_snapshot();
447 cx.region_vars.make_subregion(origin, a, b);
448 cx.region_vars.commit(snapshot);
451 pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
458 debug!("mk_eqty({:?} <: {:?})", a, b);
459 cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
462 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
465 a: ty::PolyTraitRef<'tcx>,
466 b: ty::PolyTraitRef<'tcx>)
469 debug!("mk_sub_trait_refs({:?} <: {:?})",
471 cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
474 fn expected_found<T>(a_is_expected: bool,
477 -> ty::ExpectedFound<T>
480 ty::ExpectedFound {expected: a, found: b}
482 ty::ExpectedFound {expected: b, found: a}
486 #[must_use = "once you start a snapshot, you should always consume it"]
487 pub struct CombinedSnapshot {
488 type_snapshot: type_variable::Snapshot,
489 int_snapshot: unify::Snapshot<ty::IntVid>,
490 float_snapshot: unify::Snapshot<ty::FloatVid>,
491 region_vars_snapshot: RegionSnapshot,
494 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
495 where T : TypeFoldable<'tcx> + HasTypeFlags
497 debug!("normalize_associated_type(t={:?})", value);
499 let value = erase_regions(tcx, value);
501 if !value.has_projection_types() {
505 let infcx = new_infer_ctxt(tcx, &tcx.tables, None, true);
506 let mut selcx = traits::SelectionContext::new(&infcx);
507 let cause = traits::ObligationCause::dummy();
508 let traits::Normalized { value: result, obligations } =
509 traits::normalize(&mut selcx, cause, &value);
511 debug!("normalize_associated_type: result={:?} obligations={:?}",
515 let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
517 for obligation in obligations {
518 fulfill_cx.register_predicate_obligation(&infcx, obligation);
521 let result = drain_fulfillment_cx_or_panic(DUMMY_SP, &infcx, &mut fulfill_cx, &result);
526 pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
527 infcx: &InferCtxt<'a,'tcx>,
528 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
531 where T : TypeFoldable<'tcx>
533 match drain_fulfillment_cx(infcx, fulfill_cx, result) {
536 infcx.tcx.sess.span_bug(
538 &format!("Encountered errors `{:?}` fulfilling during trans",
544 /// Finishes processes any obligations that remain in the fulfillment
545 /// context, and then "freshens" and returns `result`. This is
546 /// primarily used during normalization and other cases where
547 /// processing the obligations in `fulfill_cx` may cause type
548 /// inference variables that appear in `result` to be unified, and
549 /// hence we need to process those obligations to get the complete
550 /// picture of the type.
551 pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
552 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
554 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
555 where T : TypeFoldable<'tcx>
557 debug!("drain_fulfillment_cx(result={:?})",
560 // In principle, we only need to do this so long as `result`
561 // contains unbound type parameters. It could be a slight
562 // optimization to stop iterating early.
563 match fulfill_cx.select_all_or_error(infcx) {
570 // Use freshen to simultaneously replace all type variables with
571 // their bindings and replace all regions with 'static. This is
572 // sort of overkill because we do not expect there to be any
573 // unbound type variables, hence no `TyFresh` types should ever be
575 Ok(result.fold_with(&mut infcx.freshener()))
578 /// Returns an equivalent value with all free regions removed (note
579 /// that late-bound regions remain, because they are important for
580 /// subtyping, but they are anonymized and normalized as well). This
581 /// is a stronger, caching version of `ty_fold::erase_regions`.
582 pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
583 where T : TypeFoldable<'tcx>
585 let value1 = value.fold_with(&mut RegionEraser(cx));
586 debug!("erase_regions({:?}) = {:?}",
590 struct RegionEraser<'a, 'tcx: 'a>(&'a ty::ctxt<'tcx>);
592 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
593 fn tcx(&self) -> &ty::ctxt<'tcx> { self.0 }
595 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
596 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
601 let t_norm = ty_fold::super_fold_ty(self, ty);
602 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
606 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
607 where T : TypeFoldable<'tcx>
609 let u = self.tcx().anonymize_late_bound_regions(t);
610 ty_fold::super_fold_binder(self, &u)
613 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
614 // because late-bound regions affect subtyping, we can't
615 // erase the bound/free distinction, but we can replace
616 // all free regions with 'static.
618 // Note that we *CAN* replace early-bound regions -- the
619 // type system never "sees" those, they get substituted
620 // away. In trans, they will always be erased to 'static
621 // whenever a substitution occurs.
623 ty::ReLateBound(..) => r,
628 fn fold_substs(&mut self,
629 substs: &subst::Substs<'tcx>)
630 -> subst::Substs<'tcx> {
631 subst::Substs { regions: subst::ErasedRegions,
632 types: substs.types.fold_with(self) }
637 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
638 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
639 t.fold_with(&mut self.freshener())
642 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
644 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
649 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
650 freshen::TypeFreshener::new(self)
653 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
654 use middle::ty::UnconstrainedNumeric::{Neither, UnconstrainedInt, UnconstrainedFloat};
656 ty::TyInfer(ty::IntVar(vid)) => {
657 if self.int_unification_table.borrow_mut().has_value(vid) {
663 ty::TyInfer(ty::FloatVar(vid)) => {
664 if self.float_unification_table.borrow_mut().has_value(vid) {
674 /// Returns a type variable's default fallback if any exists. A default
675 /// must be attached to the variable when created, if it is created
676 /// without a default, this will return None.
678 /// This code does not apply to integral or floating point variables,
679 /// only to use declared defaults.
681 /// See `new_ty_var_with_default` to create a type variable with a default.
682 /// See `type_variable::Default` for details about what a default entails.
683 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
685 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
690 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
691 let mut variables = Vec::new();
693 let unbound_ty_vars = self.type_variables
695 .unsolved_variables()
697 .map(|t| self.tcx.mk_var(t));
699 let unbound_int_vars = self.int_unification_table
701 .unsolved_variables()
703 .map(|v| self.tcx.mk_int_var(v));
705 let unbound_float_vars = self.float_unification_table
707 .unsolved_variables()
709 .map(|v| self.tcx.mk_float_var(v));
711 variables.extend(unbound_ty_vars);
712 variables.extend(unbound_int_vars);
713 variables.extend(unbound_float_vars);
718 fn combine_fields(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
719 -> CombineFields<'a, 'tcx> {
720 CombineFields {infcx: self,
721 a_is_expected: a_is_expected,
726 // public so that it can be used from the rustc_driver unit tests
727 pub fn equate(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
728 -> equate::Equate<'a, 'tcx>
730 self.combine_fields(a_is_expected, trace).equate()
733 // public so that it can be used from the rustc_driver unit tests
734 pub fn sub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
735 -> sub::Sub<'a, 'tcx>
737 self.combine_fields(a_is_expected, trace).sub()
740 // public so that it can be used from the rustc_driver unit tests
741 pub fn lub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
742 -> lub::Lub<'a, 'tcx>
744 self.combine_fields(a_is_expected, trace).lub()
747 // public so that it can be used from the rustc_driver unit tests
748 pub fn glb(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
749 -> glb::Glb<'a, 'tcx>
751 self.combine_fields(a_is_expected, trace).glb()
754 fn start_snapshot(&self) -> CombinedSnapshot {
756 type_snapshot: self.type_variables.borrow_mut().snapshot(),
757 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
758 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
759 region_vars_snapshot: self.region_vars.start_snapshot(),
763 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
764 debug!("rollback_to(cause={})", cause);
765 let CombinedSnapshot { type_snapshot,
768 region_vars_snapshot } = snapshot;
772 .rollback_to(type_snapshot);
773 self.int_unification_table
775 .rollback_to(int_snapshot);
776 self.float_unification_table
778 .rollback_to(float_snapshot);
780 .rollback_to(region_vars_snapshot);
783 fn commit_from(&self, snapshot: CombinedSnapshot) {
784 debug!("commit_from!");
785 let CombinedSnapshot { type_snapshot,
788 region_vars_snapshot } = snapshot;
792 .commit(type_snapshot);
793 self.int_unification_table
795 .commit(int_snapshot);
796 self.float_unification_table
798 .commit(float_snapshot);
800 .commit(region_vars_snapshot);
803 /// Execute `f` and commit the bindings
804 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
808 let snapshot = self.start_snapshot();
810 self.commit_from(snapshot);
814 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
815 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
816 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
818 debug!("commit_if_ok()");
819 let snapshot = self.start_snapshot();
820 let r = f(&snapshot);
821 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
823 Ok(_) => { self.commit_from(snapshot); }
824 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
829 /// Execute `f` and commit only the region bindings if successful.
830 /// The function f must be very careful not to leak any non-region
831 /// variables that get created.
832 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
833 F: FnOnce() -> Result<T, E>
835 debug!("commit_regions_if_ok()");
836 let CombinedSnapshot { type_snapshot,
839 region_vars_snapshot } = self.start_snapshot();
841 let r = self.commit_if_ok(|_| f());
843 debug!("commit_regions_if_ok: rolling back everything but regions");
845 // Roll back any non-region bindings - they should be resolved
846 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
849 .rollback_to(type_snapshot);
850 self.int_unification_table
852 .rollback_to(int_snapshot);
853 self.float_unification_table
855 .rollback_to(float_snapshot);
857 // Commit region vars that may escape through resolved types.
859 .commit(region_vars_snapshot);
864 /// Execute `f` then unroll any bindings it creates
865 pub fn probe<R, F>(&self, f: F) -> R where
866 F: FnOnce(&CombinedSnapshot) -> R,
869 let snapshot = self.start_snapshot();
870 let r = f(&snapshot);
871 self.rollback_to("probe", snapshot);
875 pub fn add_given(&self,
879 self.region_vars.add_given(sub, sup);
882 pub fn sub_types(&self,
889 debug!("sub_types({:?} <: {:?})", a, b);
890 self.commit_if_ok(|_| {
891 let trace = TypeTrace::types(origin, a_is_expected, a, b);
892 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
896 pub fn eq_types(&self,
903 self.commit_if_ok(|_| {
904 let trace = TypeTrace::types(origin, a_is_expected, a, b);
905 self.equate(a_is_expected, trace).relate(&a, &b).map(|_| ())
909 pub fn sub_trait_refs(&self,
912 a: ty::TraitRef<'tcx>,
913 b: ty::TraitRef<'tcx>)
916 debug!("sub_trait_refs({:?} <: {:?})",
919 self.commit_if_ok(|_| {
920 let trace = TypeTrace {
922 values: TraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
924 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
928 pub fn sub_poly_trait_refs(&self,
931 a: ty::PolyTraitRef<'tcx>,
932 b: ty::PolyTraitRef<'tcx>)
935 debug!("sub_poly_trait_refs({:?} <: {:?})",
938 self.commit_if_ok(|_| {
939 let trace = TypeTrace {
941 values: PolyTraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
943 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
947 pub fn construct_skolemized_subst(&self,
948 generics: &ty::Generics<'tcx>,
949 snapshot: &CombinedSnapshot)
950 -> (subst::Substs<'tcx>, SkolemizationMap) {
951 /*! See `higher_ranked::construct_skolemized_subst` */
953 higher_ranked::construct_skolemized_substs(self, generics, snapshot)
956 pub fn skolemize_late_bound_regions<T>(&self,
957 value: &ty::Binder<T>,
958 snapshot: &CombinedSnapshot)
959 -> (T, SkolemizationMap)
960 where T : TypeFoldable<'tcx>
962 /*! See `higher_ranked::skolemize_late_bound_regions` */
964 higher_ranked::skolemize_late_bound_regions(self, value, snapshot)
967 pub fn leak_check(&self,
968 skol_map: &SkolemizationMap,
969 snapshot: &CombinedSnapshot)
972 /*! See `higher_ranked::leak_check` */
974 match higher_ranked::leak_check(self, skol_map, snapshot) {
976 Err((br, r)) => Err(TypeError::RegionsInsufficientlyPolymorphic(br, r))
980 pub fn plug_leaks<T>(&self,
981 skol_map: SkolemizationMap,
982 snapshot: &CombinedSnapshot,
985 where T : TypeFoldable<'tcx>
987 /*! See `higher_ranked::plug_leaks` */
989 higher_ranked::plug_leaks(self, skol_map, snapshot, value)
992 pub fn equality_predicate(&self,
994 predicate: &ty::PolyEquatePredicate<'tcx>)
995 -> UnitResult<'tcx> {
996 self.commit_if_ok(|snapshot| {
997 let (ty::EquatePredicate(a, b), skol_map) =
998 self.skolemize_late_bound_regions(predicate, snapshot);
999 let origin = EquatePredicate(span);
1000 let () = try!(mk_eqty(self, false, origin, a, b));
1001 self.leak_check(&skol_map, snapshot)
1005 pub fn region_outlives_predicate(&self,
1007 predicate: &ty::PolyRegionOutlivesPredicate)
1008 -> UnitResult<'tcx> {
1009 self.commit_if_ok(|snapshot| {
1010 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
1011 self.skolemize_late_bound_regions(predicate, snapshot);
1012 let origin = RelateRegionParamBound(span);
1013 let () = mk_subr(self, origin, r_b, r_a); // `b : a` ==> `a <= b`
1014 self.leak_check(&skol_map, snapshot)
1018 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
1021 .new_var(diverging, None)
1024 pub fn next_ty_var(&self) -> Ty<'tcx> {
1025 self.tcx.mk_var(self.next_ty_var_id(false))
1028 pub fn next_ty_var_with_default(&self,
1029 default: Option<type_variable::Default<'tcx>>) -> Ty<'tcx> {
1030 let ty_var_id = self.type_variables
1032 .new_var(false, default);
1034 self.tcx.mk_var(ty_var_id)
1037 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
1038 self.tcx.mk_var(self.next_ty_var_id(true))
1041 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
1042 (0..n).map(|_i| self.next_ty_var()).collect()
1045 pub fn next_int_var_id(&self) -> IntVid {
1046 self.int_unification_table
1051 pub fn next_float_var_id(&self) -> FloatVid {
1052 self.float_unification_table
1057 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region {
1058 ty::ReInfer(ty::ReVar(self.region_vars.new_region_var(origin)))
1061 pub fn region_vars_for_defs(&self,
1063 defs: &[ty::RegionParameterDef])
1064 -> Vec<ty::Region> {
1066 .map(|d| self.next_region_var(EarlyBoundRegion(span, d.name)))
1070 // We have to take `&mut Substs` in order to provide the correct substitutions for defaults
1071 // along the way, for this reason we don't return them.
1072 pub fn type_vars_for_defs(&self,
1074 space: subst::ParamSpace,
1075 substs: &mut Substs<'tcx>,
1076 defs: &[ty::TypeParameterDef<'tcx>]) {
1078 let mut vars = Vec::with_capacity(defs.len());
1080 for def in defs.iter() {
1081 let default = def.default.map(|default| {
1082 type_variable::Default {
1083 ty: default.subst_spanned(self.tcx, substs, Some(span)),
1085 def_id: def.default_def_id
1089 let ty_var = self.next_ty_var_with_default(default);
1090 substs.types.push(space, ty_var);
1095 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1096 /// type/region parameter to a fresh inference variable.
1097 pub fn fresh_substs_for_generics(&self,
1099 generics: &ty::Generics<'tcx>)
1100 -> subst::Substs<'tcx>
1102 let type_params = subst::VecPerParamSpace::empty();
1105 generics.regions.map(
1106 |d| self.next_region_var(EarlyBoundRegion(span, d.name)));
1108 let mut substs = subst::Substs::new(type_params, region_params);
1110 for space in subst::ParamSpace::all().iter() {
1111 self.type_vars_for_defs(
1115 generics.types.get_slice(*space));
1121 /// Given a set of generics defined on a trait, returns a substitution mapping each output
1122 /// type/region parameter to a fresh inference variable, and mapping the self type to
1124 pub fn fresh_substs_for_trait(&self,
1126 generics: &ty::Generics<'tcx>,
1128 -> subst::Substs<'tcx>
1131 assert!(generics.types.len(subst::SelfSpace) == 1);
1132 assert!(generics.types.len(subst::FnSpace) == 0);
1133 assert!(generics.regions.len(subst::SelfSpace) == 0);
1134 assert!(generics.regions.len(subst::FnSpace) == 0);
1136 let type_params = Vec::new();
1138 let region_param_defs = generics.regions.get_slice(subst::TypeSpace);
1139 let regions = self.region_vars_for_defs(span, region_param_defs);
1141 let mut substs = subst::Substs::new_trait(type_params, regions, self_ty);
1143 let type_parameter_defs = generics.types.get_slice(subst::TypeSpace);
1144 self.type_vars_for_defs(span, subst::TypeSpace, &mut substs, type_parameter_defs);
1149 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {
1150 self.region_vars.new_bound(debruijn)
1153 /// Apply `adjustment` to the type of `expr`
1154 pub fn adjust_expr_ty(&self,
1156 adjustment: Option<&ty::AutoAdjustment<'tcx>>)
1159 let raw_ty = self.expr_ty(expr);
1160 let raw_ty = self.shallow_resolve(raw_ty);
1161 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1162 raw_ty.adjust(self.tcx,
1166 |method_call| self.tables
1170 .map(|method| resolve_ty(method.ty)))
1173 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1174 match self.tables.borrow().node_types.get(&id) {
1177 None if self.tcx.sess.err_count() - self.err_count_on_creation != 0 =>
1181 &format!("no type for node {}: {} in fcx",
1182 id, self.tcx.map.node_to_string(id)));
1187 pub fn expr_ty(&self, ex: &ast::Expr) -> Ty<'tcx> {
1188 match self.tables.borrow().node_types.get(&ex.id) {
1191 self.tcx.sess.bug(&format!("no type for expr in fcx"));
1196 pub fn resolve_regions_and_report_errors(&self,
1197 free_regions: &FreeRegionMap,
1198 subject_node_id: ast::NodeId) {
1199 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1200 self.report_region_errors(&errors); // see error_reporting.rs
1203 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1204 self.resolve_type_vars_if_possible(&t).to_string()
1207 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1208 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1209 format!("({})", tstrs.join(", "))
1212 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1213 self.resolve_type_vars_if_possible(t).to_string()
1216 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1218 ty::TyInfer(ty::TyVar(v)) => {
1219 // Not entirely obvious: if `typ` is a type variable,
1220 // it can be resolved to an int/float variable, which
1221 // can then be recursively resolved, hence the
1222 // recursion. Note though that we prevent type
1223 // variables from unifying to other type variables
1224 // directly (though they may be embedded
1225 // structurally), and we prevent cycles in any case,
1226 // so this recursion should always be of very limited
1228 self.type_variables.borrow()
1230 .map(|t| self.shallow_resolve(t))
1234 ty::TyInfer(ty::IntVar(v)) => {
1235 self.int_unification_table
1238 .map(|v| v.to_type(self.tcx))
1242 ty::TyInfer(ty::FloatVar(v)) => {
1243 self.float_unification_table
1246 .map(|v| v.to_type(self.tcx))
1256 pub fn resolve_type_vars_if_possible<T:TypeFoldable<'tcx>>(&self, value: &T) -> T {
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 let mut r = resolve::OpportunisticTypeResolver::new(self);
1267 value.fold_with(&mut r)
1270 /// Resolves all type variables in `t` and then, if any were left
1271 /// unresolved, substitutes an error type. This is used after the
1272 /// main checking when doing a second pass before writeback. The
1273 /// justification is that writeback will produce an error for
1274 /// these unconstrained type variables.
1275 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1276 let ty = self.resolve_type_vars_if_possible(t);
1277 if ty.references_error() || ty.is_ty_var() {
1278 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1285 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1287 * Attempts to resolve all type/region variables in
1288 * `value`. Region inference must have been run already (e.g.,
1289 * by calling `resolve_regions_and_report_errors`). If some
1290 * variable was never unified, an `Err` results.
1292 * This method is idempotent, but it not typically not invoked
1293 * except during the writeback phase.
1296 resolve::fully_resolve(self, value)
1299 // [Note-Type-error-reporting]
1300 // An invariant is that anytime the expected or actual type is TyError (the special
1301 // error type, meaning that an error occurred when typechecking this expression),
1302 // this is a derived error. The error cascaded from another error (that was already
1303 // reported), so it's not useful to display it to the user.
1304 // The following four methods -- type_error_message_str, type_error_message_str_with_expected,
1305 // type_error_message, and report_mismatched_types -- implement this logic.
1306 // They check if either the actual or expected type is TyError, and don't print the error
1307 // in this case. The typechecker should only ever report type errors involving mismatched
1308 // types using one of these four methods, and should not call span_err directly for such
1310 pub fn type_error_message_str<M>(&self,
1314 err: Option<&ty::TypeError<'tcx>>) where
1315 M: FnOnce(Option<String>, String) -> String,
1317 self.type_error_message_str_with_expected(sp, mk_msg, None, actual_ty, err)
1320 pub fn type_error_message_str_with_expected<M>(&self,
1323 expected_ty: Option<Ty<'tcx>>,
1325 err: Option<&ty::TypeError<'tcx>>) where
1326 M: FnOnce(Option<String>, String) -> String,
1328 debug!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
1330 let resolved_expected = expected_ty.map(|e_ty| self.resolve_type_vars_if_possible(&e_ty));
1332 if !resolved_expected.references_error() {
1333 let error_str = err.map_or("".to_string(), |t_err| {
1334 format!(" ({})", t_err)
1337 self.tcx.sess.span_err(sp, &format!("{}{}",
1338 mk_msg(resolved_expected.map(|t| self.ty_to_string(t)), actual_ty),
1341 if let Some(err) = err {
1342 self.tcx.note_and_explain_type_err(err, sp)
1347 pub fn type_error_message<M>(&self,
1350 actual_ty: Ty<'tcx>,
1351 err: Option<&ty::TypeError<'tcx>>) where
1352 M: FnOnce(String) -> String,
1354 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1356 // Don't report an error if actual type is TyError.
1357 if actual_ty.references_error() {
1361 self.type_error_message_str(sp,
1362 move |_e, a| { mk_msg(a) },
1363 self.ty_to_string(actual_ty), err);
1366 pub fn report_mismatched_types(&self,
1370 err: &ty::TypeError<'tcx>) {
1371 let trace = TypeTrace {
1373 values: Types(ty::ExpectedFound {
1378 self.report_and_explain_type_error(trace, err);
1381 pub fn report_conflicting_default_types(&self,
1383 expected: type_variable::Default<'tcx>,
1384 actual: type_variable::Default<'tcx>) {
1385 let trace = TypeTrace {
1387 values: Types(ty::ExpectedFound {
1388 expected: expected.ty,
1393 self.report_and_explain_type_error(trace,
1394 &TypeError::TyParamDefaultMismatch(ty::ExpectedFound {
1400 pub fn replace_late_bound_regions_with_fresh_var<T>(
1403 lbrct: LateBoundRegionConversionTime,
1404 value: &ty::Binder<T>)
1405 -> (T, FnvHashMap<ty::BoundRegion,ty::Region>)
1406 where T : TypeFoldable<'tcx>
1408 ty_fold::replace_late_bound_regions(
1411 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1414 /// See `verify_generic_bound` method in `region_inference`
1415 pub fn verify_generic_bound(&self,
1416 origin: SubregionOrigin<'tcx>,
1417 kind: GenericKind<'tcx>,
1419 bs: Vec<ty::Region>) {
1420 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1425 self.region_vars.verify_generic_bound(origin, kind, a, bs);
1428 pub fn can_equate<'b,T>(&'b self, a: &T, b: &T) -> UnitResult<'tcx>
1429 where T: Relate<'b,'tcx> + fmt::Debug
1431 debug!("can_equate({:?}, {:?})", a, b);
1433 // Gin up a dummy trace, since this won't be committed
1434 // anyhow. We should make this typetrace stuff more
1435 // generic so we don't have to do anything quite this
1437 let e = self.tcx.types.err;
1438 let trace = TypeTrace { origin: Misc(codemap::DUMMY_SP),
1439 values: Types(expected_found(true, e, e)) };
1440 self.equate(true, trace).relate(a, b)
1444 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1445 let ty = self.node_type(id);
1446 self.resolve_type_vars_or_error(&ty)
1449 pub fn expr_ty_adjusted(&self, expr: &ast::Expr) -> McResult<Ty<'tcx>> {
1450 let ty = self.adjust_expr_ty(expr, self.tables.borrow().adjustments.get(&expr.id));
1451 self.resolve_type_vars_or_error(&ty)
1454 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1455 let ty = self.resolve_type_vars_if_possible(&ty);
1456 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1457 // FIXME(@jroesch): should be able to use:
1458 // ty.moves_by_default(&self.parameter_environment, span)
1461 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1462 -> Option<Ty<'tcx>> {
1467 .map(|method| method.ty)
1468 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1471 pub fn node_method_id(&self, method_call: ty::MethodCall)
1472 -> Option<ast::DefId> {
1477 .map(|method| method.def_id)
1480 pub fn adjustments(&self) -> Ref<NodeMap<ty::AutoAdjustment<'tcx>>> {
1481 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1482 -> &'a NodeMap<ty::AutoAdjustment<'tcx>> {
1486 Ref::map(self.tables.borrow(), project_adjustments)
1489 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1490 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1493 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1494 self.tcx.region_maps.temporary_scope(rvalue_id)
1497 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture> {
1498 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1501 pub fn param_env<'b>(&'b self) -> &'b ty::ParameterEnvironment<'b,'tcx> {
1502 &self.parameter_environment
1505 pub fn closure_kind(&self,
1507 -> Option<ty::ClosureKind>
1509 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1512 pub fn closure_type(&self,
1514 substs: &ty::ClosureSubsts<'tcx>)
1515 -> ty::ClosureTy<'tcx>
1517 let closure_ty = self.tables
1522 .subst(self.tcx, &substs.func_substs);
1525 normalize_associated_type(&self.tcx, &closure_ty)
1532 impl<'tcx> TypeTrace<'tcx> {
1533 pub fn span(&self) -> Span {
1537 pub fn types(origin: TypeOrigin,
1538 a_is_expected: bool,
1541 -> TypeTrace<'tcx> {
1544 values: Types(expected_found(a_is_expected, a, b))
1548 pub fn dummy(tcx: &ty::ctxt<'tcx>) -> TypeTrace<'tcx> {
1550 origin: Misc(codemap::DUMMY_SP),
1551 values: Types(ty::ExpectedFound {
1552 expected: tcx.types.err,
1553 found: tcx.types.err,
1559 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1560 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1561 write!(f, "TypeTrace({:?})", self.origin)
1566 pub fn span(&self) -> Span {
1568 MethodCompatCheck(span) => span,
1569 ExprAssignable(span) => span,
1571 RelateTraitRefs(span) => span,
1572 RelateSelfType(span) => span,
1573 RelateOutputImplTypes(span) => span,
1574 MatchExpressionArm(match_span, _) => match_span,
1575 IfExpression(span) => span,
1576 IfExpressionWithNoElse(span) => span,
1577 RangeExpression(span) => span,
1578 EquatePredicate(span) => span,
1583 impl<'tcx> SubregionOrigin<'tcx> {
1584 pub fn span(&self) -> Span {
1586 RFC1214Subregion(ref a) => a.span(),
1587 Subtype(ref a) => a.span(),
1588 InfStackClosure(a) => a,
1589 InvokeClosure(a) => a,
1590 DerefPointer(a) => a,
1591 FreeVariable(a, _) => a,
1593 RelateObjectBound(a) => a,
1594 RelateParamBound(a, _) => a,
1595 RelateRegionParamBound(a) => a,
1596 RelateDefaultParamBound(a, _) => a,
1598 ReborrowUpvar(a, _) => a,
1599 DataBorrowed(_, a) => a,
1600 ReferenceOutlivesReferent(_, a) => a,
1601 ParameterInScope(_, a) => a,
1602 ExprTypeIsNotInScope(_, a) => a,
1603 BindingTypeIsNotValidAtDecl(a) => a,
1610 SafeDestructor(a) => a,
1615 impl RegionVariableOrigin {
1616 pub fn span(&self) -> Span {
1618 MiscVariable(a) => a,
1619 PatternRegion(a) => a,
1620 AddrOfRegion(a) => a,
1623 EarlyBoundRegion(a, _) => a,
1624 LateBoundRegion(a, _, _) => a,
1625 BoundRegionInCoherence(_) => codemap::DUMMY_SP,
1626 UpvarRegion(_, a) => a