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;
23 use middle::free_region::FreeRegionMap;
24 use middle::mem_categorization as mc;
25 use middle::mem_categorization::McResult;
26 use middle::region::CodeExtent;
28 use middle::subst::Substs;
29 use middle::subst::Subst;
30 use middle::traits::{self, FulfillmentContext, Normalized,
31 SelectionContext, ObligationCause};
32 use middle::ty::{TyVid, IntVid, FloatVid, RegionVid, UnconstrainedNumeric};
33 use middle::ty::{self, Ty, TypeError, HasTypeFlags};
34 use middle::ty_fold::{self, TypeFolder, TypeFoldable};
35 use middle::ty_relate::{Relate, RelateResult, TypeRelation};
36 use rustc_data_structures::unify::{self, UnificationTable};
37 use std::cell::{RefCell, Ref};
42 use syntax::codemap::{Span, DUMMY_SP};
43 use util::nodemap::{FnvHashMap, NodeMap};
45 use self::combine::CombineFields;
46 use self::region_inference::{RegionVarBindings, RegionSnapshot};
47 use self::error_reporting::ErrorReporting;
48 use self::unify_key::ToType;
53 pub mod error_reporting;
58 pub mod region_inference;
62 pub mod type_variable;
65 pub type Bound<T> = Option<T>;
66 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
67 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
69 pub struct InferCtxt<'a, 'tcx: 'a> {
70 pub tcx: &'a ty::ctxt<'tcx>,
72 pub tables: &'a RefCell<ty::Tables<'tcx>>,
74 // We instantiate UnificationTable with bounds<Ty> because the
75 // types that might instantiate a general type variable have an
76 // order, represented by its upper and lower bounds.
77 type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
79 // Map from integral variable to the kind of integer it represents
80 int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
82 // Map from floating variable to the kind of float it represents
83 float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
85 // For region variables.
86 region_vars: RegionVarBindings<'a, 'tcx>,
88 pub parameter_environment: ty::ParameterEnvironment<'a, 'tcx>,
90 pub fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
92 // This is a temporary field used for toggling on normalization in the inference context,
93 // as we move towards the approach described here:
94 // https://internals.rust-lang.org/t/flattening-the-contexts-for-fun-and-profit/2293
95 // At a point sometime in the future normalization will be done by the typing context
99 err_count_on_creation: usize,
102 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
103 /// region that each late-bound region was replaced with.
104 pub type SkolemizationMap = FnvHashMap<ty::BoundRegion,ty::Region>;
106 /// Why did we require that the two types be related?
108 /// See `error_reporting.rs` for more details
109 #[derive(Clone, Copy, Debug)]
110 pub enum TypeOrigin {
111 // Not yet categorized in a better way
114 // Checking that method of impl is compatible with trait
115 MethodCompatCheck(Span),
117 // Checking that this expression can be assigned where it needs to be
118 // FIXME(eddyb) #11161 is the original Expr required?
119 ExprAssignable(Span),
121 // Relating trait refs when resolving vtables
122 RelateTraitRefs(Span),
124 // Relating self types when resolving vtables
125 RelateSelfType(Span),
127 // Relating trait type parameters to those found in impl etc
128 RelateOutputImplTypes(Span),
130 // Computing common supertype in the arms of a match expression
131 MatchExpressionArm(Span, Span),
133 // Computing common supertype in an if expression
136 // Computing common supertype of an if expression with no else counter-part
137 IfExpressionWithNoElse(Span),
139 // Computing common supertype in a range expression
140 RangeExpression(Span),
143 EquatePredicate(Span),
147 fn as_str(&self) -> &'static str {
149 &TypeOrigin::Misc(_) |
150 &TypeOrigin::RelateSelfType(_) |
151 &TypeOrigin::RelateOutputImplTypes(_) |
152 &TypeOrigin::ExprAssignable(_) => "mismatched types",
153 &TypeOrigin::RelateTraitRefs(_) => "mismatched traits",
154 &TypeOrigin::MethodCompatCheck(_) => "method not compatible with trait",
155 &TypeOrigin::MatchExpressionArm(_, _) => "match arms have incompatible types",
156 &TypeOrigin::IfExpression(_) => "if and else have incompatible types",
157 &TypeOrigin::IfExpressionWithNoElse(_) => "if may be missing an else clause",
158 &TypeOrigin::RangeExpression(_) => "start and end of range have incompatible types",
159 &TypeOrigin::EquatePredicate(_) => "equality predicate not satisfied",
164 impl fmt::Display for TypeOrigin {
165 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error> {
166 fmt::Display::fmt(self.as_str(), f)
170 /// See `error_reporting.rs` for more details
171 #[derive(Clone, Debug)]
172 pub enum ValuePairs<'tcx> {
173 Types(ty::ExpectedFound<Ty<'tcx>>),
174 TraitRefs(ty::ExpectedFound<ty::TraitRef<'tcx>>),
175 PolyTraitRefs(ty::ExpectedFound<ty::PolyTraitRef<'tcx>>),
178 /// The trace designates the path through inference that we took to
179 /// encounter an error or subtyping constraint.
181 /// See `error_reporting.rs` for more details.
183 pub struct TypeTrace<'tcx> {
185 values: ValuePairs<'tcx>,
188 /// The origin of a `r1 <= r2` constraint.
190 /// See `error_reporting.rs` for more details
191 #[derive(Clone, Debug)]
192 pub enum SubregionOrigin<'tcx> {
193 // Marker to indicate a constraint that only arises due to new
194 // provisions from RFC 1214. This will result in a warning, not an
196 RFC1214Subregion(Rc<SubregionOrigin<'tcx>>),
198 // Arose from a subtyping relation
199 Subtype(TypeTrace<'tcx>),
201 // Stack-allocated closures cannot outlive innermost loop
202 // or function so as to ensure we only require finite stack
203 InfStackClosure(Span),
205 // Invocation of closure must be within its lifetime
208 // Dereference of reference must be within its lifetime
211 // Closure bound must not outlive captured free variables
212 FreeVariable(Span, ast::NodeId),
214 // Index into slice must be within its lifetime
217 // When casting `&'a T` to an `&'b Trait` object,
218 // relating `'a` to `'b`
219 RelateObjectBound(Span),
221 // Some type parameter was instantiated with the given type,
222 // and that type must outlive some region.
223 RelateParamBound(Span, Ty<'tcx>),
225 // The given region parameter was instantiated with a region
226 // that must outlive some other region.
227 RelateRegionParamBound(Span),
229 // A bound placed on type parameters that states that must outlive
230 // the moment of their instantiation.
231 RelateDefaultParamBound(Span, Ty<'tcx>),
233 // Creating a pointer `b` to contents of another reference
236 // Creating a pointer `b` to contents of an upvar
237 ReborrowUpvar(Span, ty::UpvarId),
239 // Data with type `Ty<'tcx>` was borrowed
240 DataBorrowed(Ty<'tcx>, Span),
242 // (&'a &'b T) where a >= b
243 ReferenceOutlivesReferent(Ty<'tcx>, Span),
245 // Type or region parameters must be in scope.
246 ParameterInScope(ParameterOrigin, Span),
248 // The type T of an expression E must outlive the lifetime for E.
249 ExprTypeIsNotInScope(Ty<'tcx>, Span),
251 // A `ref b` whose region does not enclose the decl site
252 BindingTypeIsNotValidAtDecl(Span),
254 // Regions appearing in a method receiver must outlive method call
257 // Regions appearing in a function argument must outlive func call
260 // Region in return type of invoked fn must enclose call
263 // Operands must be in scope
266 // Region resulting from a `&` expr must enclose the `&` expr
269 // An auto-borrow that does not enclose the expr where it occurs
272 // Region constraint arriving from destructor safety
273 SafeDestructor(Span),
276 /// Places that type/region parameters can appear.
277 #[derive(Clone, Copy, Debug)]
278 pub enum ParameterOrigin {
280 MethodCall, // foo.bar() <-- parameters on impl providing bar()
281 OverloadedOperator, // a + b when overloaded
282 OverloadedDeref, // *a when overloaded
285 /// Times when we replace late-bound regions with variables:
286 #[derive(Clone, Copy, Debug)]
287 pub enum LateBoundRegionConversionTime {
288 /// when a fn is called
291 /// when two higher-ranked types are compared
294 /// when projecting an associated type
295 AssocTypeProjection(ast::Name),
298 /// Reasons to create a region inference variable
300 /// See `error_reporting.rs` for more details
301 #[derive(Clone, Debug)]
302 pub enum RegionVariableOrigin {
303 // Region variables created for ill-categorized reasons,
304 // mostly indicates places in need of refactoring
307 // Regions created by a `&P` or `[...]` pattern
310 // Regions created by `&` operator
313 // Regions created as part of an autoref of a method receiver
316 // Regions created as part of an automatic coercion
319 // Region variables created as the values for early-bound regions
320 EarlyBoundRegion(Span, ast::Name),
322 // Region variables created for bound regions
323 // in a function or method that is called
324 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
326 UpvarRegion(ty::UpvarId, Span),
328 BoundRegionInCoherence(ast::Name),
331 #[derive(Copy, Clone, Debug)]
332 pub enum FixupError {
333 UnresolvedIntTy(IntVid),
334 UnresolvedFloatTy(FloatVid),
338 pub fn fixup_err_to_string(f: FixupError) -> String {
339 use self::FixupError::*;
342 UnresolvedIntTy(_) => {
343 "cannot determine the type of this integer; add a suffix to \
344 specify the type explicitly".to_string()
346 UnresolvedFloatTy(_) => {
347 "cannot determine the type of this number; add a suffix to specify \
348 the type explicitly".to_string()
350 UnresolvedTy(_) => "unconstrained type".to_string(),
354 /// errors_will_be_reported is required to proxy to the fulfillment context
355 /// FIXME -- a better option would be to hold back on modifying
356 /// the global cache until we know that all dependent obligations
357 /// are also satisfied. In that case, we could actually remove
358 /// this boolean flag, and we'd also avoid the problem of squelching
359 /// duplicate errors that occur across fns.
360 pub fn new_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
361 tables: &'a RefCell<ty::Tables<'tcx>>,
362 param_env: Option<ty::ParameterEnvironment<'a, 'tcx>>,
363 errors_will_be_reported: bool)
364 -> InferCtxt<'a, 'tcx> {
368 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
369 int_unification_table: RefCell::new(UnificationTable::new()),
370 float_unification_table: RefCell::new(UnificationTable::new()),
371 region_vars: RegionVarBindings::new(tcx),
372 parameter_environment: param_env.unwrap_or(tcx.empty_parameter_environment()),
373 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new(errors_will_be_reported)),
375 err_count_on_creation: tcx.sess.err_count()
379 pub fn normalizing_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
380 tables: &'a RefCell<ty::Tables<'tcx>>)
381 -> InferCtxt<'a, 'tcx> {
382 let mut infcx = new_infer_ctxt(tcx, tables, None, false);
383 infcx.normalize = true;
387 /// Computes the least upper-bound of `a` and `b`. If this is not possible, reports an error and
389 pub fn common_supertype<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
396 debug!("common_supertype({:?}, {:?})",
399 let trace = TypeTrace {
401 values: Types(expected_found(a_is_expected, a, b))
404 let result = cx.commit_if_ok(|_| cx.lub(a_is_expected, trace.clone()).relate(&a, &b));
408 cx.report_and_explain_type_error(trace, err);
414 pub fn mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
421 debug!("mk_subty({:?} <: {:?})", a, b);
422 cx.sub_types(a_is_expected, origin, a, b)
425 pub fn can_mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
428 -> UnitResult<'tcx> {
429 debug!("can_mk_subty({:?} <: {:?})", a, b);
431 let trace = TypeTrace {
432 origin: Misc(codemap::DUMMY_SP),
433 values: Types(expected_found(true, a, b))
435 cx.sub(true, trace).relate(&a, &b).map(|_| ())
439 pub fn can_mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>, a: Ty<'tcx>, b: Ty<'tcx>)
442 cx.can_equate(&a, &b)
445 pub fn mk_subr<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
446 origin: SubregionOrigin<'tcx>,
449 debug!("mk_subr({:?} <: {:?})", a, b);
450 let snapshot = cx.region_vars.start_snapshot();
451 cx.region_vars.make_subregion(origin, a, b);
452 cx.region_vars.commit(snapshot);
455 pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
462 debug!("mk_eqty({:?} <: {:?})", a, b);
463 cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
466 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
469 a: ty::PolyTraitRef<'tcx>,
470 b: ty::PolyTraitRef<'tcx>)
473 debug!("mk_sub_trait_refs({:?} <: {:?})",
475 cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
478 fn expected_found<T>(a_is_expected: bool,
481 -> ty::ExpectedFound<T>
484 ty::ExpectedFound {expected: a, found: b}
486 ty::ExpectedFound {expected: b, found: a}
490 #[must_use = "once you start a snapshot, you should always consume it"]
491 pub struct CombinedSnapshot {
492 type_snapshot: type_variable::Snapshot,
493 int_snapshot: unify::Snapshot<ty::IntVid>,
494 float_snapshot: unify::Snapshot<ty::FloatVid>,
495 region_vars_snapshot: RegionSnapshot,
498 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
499 where T : TypeFoldable<'tcx> + HasTypeFlags
501 debug!("normalize_associated_type(t={:?})", value);
503 let value = erase_regions(tcx, value);
505 if !value.has_projection_types() {
509 let infcx = new_infer_ctxt(tcx, &tcx.tables, None, true);
510 let mut selcx = traits::SelectionContext::new(&infcx);
511 let cause = traits::ObligationCause::dummy();
512 let traits::Normalized { value: result, obligations } =
513 traits::normalize(&mut selcx, cause, &value);
515 debug!("normalize_associated_type: result={:?} obligations={:?}",
519 let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
521 for obligation in obligations {
522 fulfill_cx.register_predicate_obligation(&infcx, obligation);
525 let result = drain_fulfillment_cx_or_panic(DUMMY_SP, &infcx, &mut fulfill_cx, &result);
530 pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
531 infcx: &InferCtxt<'a,'tcx>,
532 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
535 where T : TypeFoldable<'tcx>
537 match drain_fulfillment_cx(infcx, fulfill_cx, result) {
540 infcx.tcx.sess.span_bug(
542 &format!("Encountered errors `{:?}` fulfilling during trans",
548 /// Finishes processes any obligations that remain in the fulfillment
549 /// context, and then "freshens" and returns `result`. This is
550 /// primarily used during normalization and other cases where
551 /// processing the obligations in `fulfill_cx` may cause type
552 /// inference variables that appear in `result` to be unified, and
553 /// hence we need to process those obligations to get the complete
554 /// picture of the type.
555 pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
556 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
558 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
559 where T : TypeFoldable<'tcx>
561 debug!("drain_fulfillment_cx(result={:?})",
564 // In principle, we only need to do this so long as `result`
565 // contains unbound type parameters. It could be a slight
566 // optimization to stop iterating early.
567 match fulfill_cx.select_all_or_error(infcx) {
574 // Use freshen to simultaneously replace all type variables with
575 // their bindings and replace all regions with 'static. This is
576 // sort of overkill because we do not expect there to be any
577 // unbound type variables, hence no `TyFresh` types should ever be
579 Ok(result.fold_with(&mut infcx.freshener()))
582 /// Returns an equivalent value with all free regions removed (note
583 /// that late-bound regions remain, because they are important for
584 /// subtyping, but they are anonymized and normalized as well). This
585 /// is a stronger, caching version of `ty_fold::erase_regions`.
586 pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
587 where T : TypeFoldable<'tcx>
589 let value1 = value.fold_with(&mut RegionEraser(cx));
590 debug!("erase_regions({:?}) = {:?}",
594 struct RegionEraser<'a, 'tcx: 'a>(&'a ty::ctxt<'tcx>);
596 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
597 fn tcx(&self) -> &ty::ctxt<'tcx> { self.0 }
599 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
600 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
605 let t_norm = ty_fold::super_fold_ty(self, ty);
606 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
610 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
611 where T : TypeFoldable<'tcx>
613 let u = self.tcx().anonymize_late_bound_regions(t);
614 ty_fold::super_fold_binder(self, &u)
617 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
618 // because late-bound regions affect subtyping, we can't
619 // erase the bound/free distinction, but we can replace
620 // all free regions with 'static.
622 // Note that we *CAN* replace early-bound regions -- the
623 // type system never "sees" those, they get substituted
624 // away. In trans, they will always be erased to 'static
625 // whenever a substitution occurs.
627 ty::ReLateBound(..) => r,
632 fn fold_substs(&mut self,
633 substs: &subst::Substs<'tcx>)
634 -> subst::Substs<'tcx> {
635 subst::Substs { regions: subst::ErasedRegions,
636 types: substs.types.fold_with(self) }
641 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
642 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
643 t.fold_with(&mut self.freshener())
646 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
648 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
653 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
654 freshen::TypeFreshener::new(self)
657 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
658 use middle::ty::UnconstrainedNumeric::{Neither, UnconstrainedInt, UnconstrainedFloat};
660 ty::TyInfer(ty::IntVar(vid)) => {
661 if self.int_unification_table.borrow_mut().has_value(vid) {
667 ty::TyInfer(ty::FloatVar(vid)) => {
668 if self.float_unification_table.borrow_mut().has_value(vid) {
678 /// Returns a type variable's default fallback if any exists. A default
679 /// must be attached to the variable when created, if it is created
680 /// without a default, this will return None.
682 /// This code does not apply to integral or floating point variables,
683 /// only to use declared defaults.
685 /// See `new_ty_var_with_default` to create a type variable with a default.
686 /// See `type_variable::Default` for details about what a default entails.
687 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
689 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
694 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
695 let mut variables = Vec::new();
697 let unbound_ty_vars = self.type_variables
699 .unsolved_variables()
701 .map(|t| self.tcx.mk_var(t));
703 let unbound_int_vars = self.int_unification_table
705 .unsolved_variables()
707 .map(|v| self.tcx.mk_int_var(v));
709 let unbound_float_vars = self.float_unification_table
711 .unsolved_variables()
713 .map(|v| self.tcx.mk_float_var(v));
715 variables.extend(unbound_ty_vars);
716 variables.extend(unbound_int_vars);
717 variables.extend(unbound_float_vars);
722 fn combine_fields(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
723 -> CombineFields<'a, 'tcx> {
724 CombineFields {infcx: self,
725 a_is_expected: a_is_expected,
730 // public so that it can be used from the rustc_driver unit tests
731 pub fn equate(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
732 -> equate::Equate<'a, 'tcx>
734 self.combine_fields(a_is_expected, trace).equate()
737 // public so that it can be used from the rustc_driver unit tests
738 pub fn sub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
739 -> sub::Sub<'a, 'tcx>
741 self.combine_fields(a_is_expected, trace).sub()
744 // public so that it can be used from the rustc_driver unit tests
745 pub fn lub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
746 -> lub::Lub<'a, 'tcx>
748 self.combine_fields(a_is_expected, trace).lub()
751 // public so that it can be used from the rustc_driver unit tests
752 pub fn glb(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
753 -> glb::Glb<'a, 'tcx>
755 self.combine_fields(a_is_expected, trace).glb()
758 fn start_snapshot(&self) -> CombinedSnapshot {
760 type_snapshot: self.type_variables.borrow_mut().snapshot(),
761 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
762 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
763 region_vars_snapshot: self.region_vars.start_snapshot(),
767 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
768 debug!("rollback_to(cause={})", cause);
769 let CombinedSnapshot { type_snapshot,
772 region_vars_snapshot } = snapshot;
776 .rollback_to(type_snapshot);
777 self.int_unification_table
779 .rollback_to(int_snapshot);
780 self.float_unification_table
782 .rollback_to(float_snapshot);
784 .rollback_to(region_vars_snapshot);
787 fn commit_from(&self, snapshot: CombinedSnapshot) {
788 debug!("commit_from!");
789 let CombinedSnapshot { type_snapshot,
792 region_vars_snapshot } = snapshot;
796 .commit(type_snapshot);
797 self.int_unification_table
799 .commit(int_snapshot);
800 self.float_unification_table
802 .commit(float_snapshot);
804 .commit(region_vars_snapshot);
807 /// Execute `f` and commit the bindings
808 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
812 let snapshot = self.start_snapshot();
814 self.commit_from(snapshot);
818 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
819 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
820 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
822 debug!("commit_if_ok()");
823 let snapshot = self.start_snapshot();
824 let r = f(&snapshot);
825 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
827 Ok(_) => { self.commit_from(snapshot); }
828 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
833 /// Execute `f` and commit only the region bindings if successful.
834 /// The function f must be very careful not to leak any non-region
835 /// variables that get created.
836 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
837 F: FnOnce() -> Result<T, E>
839 debug!("commit_regions_if_ok()");
840 let CombinedSnapshot { type_snapshot,
843 region_vars_snapshot } = self.start_snapshot();
845 let r = self.commit_if_ok(|_| f());
847 debug!("commit_regions_if_ok: rolling back everything but regions");
849 // Roll back any non-region bindings - they should be resolved
850 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
853 .rollback_to(type_snapshot);
854 self.int_unification_table
856 .rollback_to(int_snapshot);
857 self.float_unification_table
859 .rollback_to(float_snapshot);
861 // Commit region vars that may escape through resolved types.
863 .commit(region_vars_snapshot);
868 /// Execute `f` then unroll any bindings it creates
869 pub fn probe<R, F>(&self, f: F) -> R where
870 F: FnOnce(&CombinedSnapshot) -> R,
873 let snapshot = self.start_snapshot();
874 let r = f(&snapshot);
875 self.rollback_to("probe", snapshot);
879 pub fn add_given(&self,
883 self.region_vars.add_given(sub, sup);
886 pub fn sub_types(&self,
893 debug!("sub_types({:?} <: {:?})", a, b);
894 self.commit_if_ok(|_| {
895 let trace = TypeTrace::types(origin, a_is_expected, a, b);
896 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
900 pub fn eq_types(&self,
907 self.commit_if_ok(|_| {
908 let trace = TypeTrace::types(origin, a_is_expected, a, b);
909 self.equate(a_is_expected, trace).relate(&a, &b).map(|_| ())
913 pub fn sub_trait_refs(&self,
916 a: ty::TraitRef<'tcx>,
917 b: ty::TraitRef<'tcx>)
920 debug!("sub_trait_refs({:?} <: {:?})",
923 self.commit_if_ok(|_| {
924 let trace = TypeTrace {
926 values: TraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
928 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
932 pub fn sub_poly_trait_refs(&self,
935 a: ty::PolyTraitRef<'tcx>,
936 b: ty::PolyTraitRef<'tcx>)
939 debug!("sub_poly_trait_refs({:?} <: {:?})",
942 self.commit_if_ok(|_| {
943 let trace = TypeTrace {
945 values: PolyTraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
947 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
951 pub fn skolemize_late_bound_regions<T>(&self,
952 value: &ty::Binder<T>,
953 snapshot: &CombinedSnapshot)
954 -> (T, SkolemizationMap)
955 where T : TypeFoldable<'tcx>
957 /*! See `higher_ranked::skolemize_late_bound_regions` */
959 higher_ranked::skolemize_late_bound_regions(self, value, snapshot)
962 pub fn leak_check(&self,
963 skol_map: &SkolemizationMap,
964 snapshot: &CombinedSnapshot)
967 /*! See `higher_ranked::leak_check` */
969 match higher_ranked::leak_check(self, skol_map, snapshot) {
971 Err((br, r)) => Err(TypeError::RegionsInsufficientlyPolymorphic(br, r))
975 pub fn plug_leaks<T>(&self,
976 skol_map: SkolemizationMap,
977 snapshot: &CombinedSnapshot,
980 where T : TypeFoldable<'tcx> + HasTypeFlags
982 /*! See `higher_ranked::plug_leaks` */
984 higher_ranked::plug_leaks(self, skol_map, snapshot, value)
987 pub fn equality_predicate(&self,
989 predicate: &ty::PolyEquatePredicate<'tcx>)
990 -> UnitResult<'tcx> {
991 self.commit_if_ok(|snapshot| {
992 let (ty::EquatePredicate(a, b), skol_map) =
993 self.skolemize_late_bound_regions(predicate, snapshot);
994 let origin = EquatePredicate(span);
995 let () = try!(mk_eqty(self, false, origin, a, b));
996 self.leak_check(&skol_map, snapshot)
1000 pub fn region_outlives_predicate(&self,
1002 predicate: &ty::PolyRegionOutlivesPredicate)
1003 -> UnitResult<'tcx> {
1004 self.commit_if_ok(|snapshot| {
1005 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
1006 self.skolemize_late_bound_regions(predicate, snapshot);
1007 let origin = RelateRegionParamBound(span);
1008 let () = mk_subr(self, origin, r_b, r_a); // `b : a` ==> `a <= b`
1009 self.leak_check(&skol_map, snapshot)
1013 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
1016 .new_var(diverging, None)
1019 pub fn next_ty_var(&self) -> Ty<'tcx> {
1020 self.tcx.mk_var(self.next_ty_var_id(false))
1023 pub fn next_ty_var_with_default(&self,
1024 default: Option<type_variable::Default<'tcx>>) -> Ty<'tcx> {
1025 let ty_var_id = self.type_variables
1027 .new_var(false, default);
1029 self.tcx.mk_var(ty_var_id)
1032 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
1033 self.tcx.mk_var(self.next_ty_var_id(true))
1036 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
1037 (0..n).map(|_i| self.next_ty_var()).collect()
1040 pub fn next_int_var_id(&self) -> IntVid {
1041 self.int_unification_table
1046 pub fn next_float_var_id(&self) -> FloatVid {
1047 self.float_unification_table
1052 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region {
1053 ty::ReVar(self.region_vars.new_region_var(origin))
1056 pub fn region_vars_for_defs(&self,
1058 defs: &[ty::RegionParameterDef])
1059 -> Vec<ty::Region> {
1061 .map(|d| self.next_region_var(EarlyBoundRegion(span, d.name)))
1065 // We have to take `&mut Substs` in order to provide the correct substitutions for defaults
1066 // along the way, for this reason we don't return them.
1067 pub fn type_vars_for_defs(&self,
1069 space: subst::ParamSpace,
1070 substs: &mut Substs<'tcx>,
1071 defs: &[ty::TypeParameterDef<'tcx>]) {
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 {
1078 ty: default.subst_spanned(self.tcx, substs, Some(span)),
1080 def_id: def.default_def_id
1084 let ty_var = self.next_ty_var_with_default(default);
1085 substs.types.push(space, ty_var);
1090 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1091 /// type/region parameter to a fresh inference variable.
1092 pub fn fresh_substs_for_generics(&self,
1094 generics: &ty::Generics<'tcx>)
1095 -> subst::Substs<'tcx>
1097 let type_params = subst::VecPerParamSpace::empty();
1100 generics.regions.map(
1101 |d| self.next_region_var(EarlyBoundRegion(span, d.name)));
1103 let mut substs = subst::Substs::new(type_params, region_params);
1105 for space in subst::ParamSpace::all().iter() {
1106 self.type_vars_for_defs(
1110 generics.types.get_slice(*space));
1116 /// Given a set of generics defined on a trait, returns a substitution mapping each output
1117 /// type/region parameter to a fresh inference variable, and mapping the self type to
1119 pub fn fresh_substs_for_trait(&self,
1121 generics: &ty::Generics<'tcx>,
1123 -> subst::Substs<'tcx>
1126 assert!(generics.types.len(subst::SelfSpace) == 1);
1127 assert!(generics.types.len(subst::FnSpace) == 0);
1128 assert!(generics.regions.len(subst::SelfSpace) == 0);
1129 assert!(generics.regions.len(subst::FnSpace) == 0);
1131 let type_params = Vec::new();
1133 let region_param_defs = generics.regions.get_slice(subst::TypeSpace);
1134 let regions = self.region_vars_for_defs(span, region_param_defs);
1136 let mut substs = subst::Substs::new_trait(type_params, regions, self_ty);
1138 let type_parameter_defs = generics.types.get_slice(subst::TypeSpace);
1139 self.type_vars_for_defs(span, subst::TypeSpace, &mut substs, type_parameter_defs);
1144 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {
1145 self.region_vars.new_bound(debruijn)
1148 /// Apply `adjustment` to the type of `expr`
1149 pub fn adjust_expr_ty(&self,
1151 adjustment: Option<&ty::AutoAdjustment<'tcx>>)
1154 let raw_ty = self.expr_ty(expr);
1155 let raw_ty = self.shallow_resolve(raw_ty);
1156 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1157 raw_ty.adjust(self.tcx,
1161 |method_call| self.tables
1165 .map(|method| resolve_ty(method.ty)))
1168 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1169 match self.tables.borrow().node_types.get(&id) {
1172 None if self.tcx.sess.err_count() - self.err_count_on_creation != 0 =>
1176 &format!("no type for node {}: {} in fcx",
1177 id, self.tcx.map.node_to_string(id)));
1182 pub fn expr_ty(&self, ex: &ast::Expr) -> Ty<'tcx> {
1183 match self.tables.borrow().node_types.get(&ex.id) {
1186 self.tcx.sess.bug(&format!("no type for expr in fcx"));
1191 pub fn resolve_regions_and_report_errors(&self,
1192 free_regions: &FreeRegionMap,
1193 subject_node_id: ast::NodeId) {
1194 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1195 self.report_region_errors(&errors); // see error_reporting.rs
1198 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1199 self.resolve_type_vars_if_possible(&t).to_string()
1202 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1203 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1204 format!("({})", tstrs.join(", "))
1207 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1208 self.resolve_type_vars_if_possible(t).to_string()
1211 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1213 ty::TyInfer(ty::TyVar(v)) => {
1214 // Not entirely obvious: if `typ` is a type variable,
1215 // it can be resolved to an int/float variable, which
1216 // can then be recursively resolved, hence the
1217 // recursion. Note though that we prevent type
1218 // variables from unifying to other type variables
1219 // directly (though they may be embedded
1220 // structurally), and we prevent cycles in any case,
1221 // so this recursion should always be of very limited
1223 self.type_variables.borrow()
1225 .map(|t| self.shallow_resolve(t))
1229 ty::TyInfer(ty::IntVar(v)) => {
1230 self.int_unification_table
1233 .map(|v| v.to_type(self.tcx))
1237 ty::TyInfer(ty::FloatVar(v)) => {
1238 self.float_unification_table
1241 .map(|v| v.to_type(self.tcx))
1251 pub fn resolve_type_vars_if_possible<T>(&self, value: &T) -> T
1252 where T: TypeFoldable<'tcx> + HasTypeFlags
1255 * Where possible, replaces type/int/float variables in
1256 * `value` with their final value. Note that region variables
1257 * are unaffected. If a type variable has not been unified, it
1258 * is left as is. This is an idempotent operation that does
1259 * not affect inference state in any way and so you can do it
1263 if !value.needs_infer() {
1264 return value.clone(); // avoid duplicated subst-folding
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 bound: VerifyBound) {
1420 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1425 self.region_vars.verify_generic_bound(origin, kind, a, bound);
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 if ty.needs_infer() {
1457 // this can get called from typeck (by euv), and moves_by_default
1458 // rightly refuses to work with inference variables, but
1459 // moves_by_default has a cache, which we want to use in other
1461 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1463 ty.moves_by_default(&self.parameter_environment, span)
1467 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1468 -> Option<Ty<'tcx>> {
1473 .map(|method| method.ty)
1474 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1477 pub fn node_method_id(&self, method_call: ty::MethodCall)
1483 .map(|method| method.def_id)
1486 pub fn adjustments(&self) -> Ref<NodeMap<ty::AutoAdjustment<'tcx>>> {
1487 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1488 -> &'a NodeMap<ty::AutoAdjustment<'tcx>> {
1492 Ref::map(self.tables.borrow(), project_adjustments)
1495 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1496 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1499 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1500 self.tcx.region_maps.temporary_scope(rvalue_id)
1503 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture> {
1504 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1507 pub fn param_env<'b>(&'b self) -> &'b ty::ParameterEnvironment<'b,'tcx> {
1508 &self.parameter_environment
1511 pub fn closure_kind(&self,
1513 -> Option<ty::ClosureKind>
1515 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1518 pub fn closure_type(&self,
1520 substs: &ty::ClosureSubsts<'tcx>)
1521 -> ty::ClosureTy<'tcx>
1523 let closure_ty = self.tables
1528 .subst(self.tcx, &substs.func_substs);
1531 normalize_associated_type(&self.tcx, &closure_ty)
1538 impl<'tcx> TypeTrace<'tcx> {
1539 pub fn span(&self) -> Span {
1543 pub fn types(origin: TypeOrigin,
1544 a_is_expected: bool,
1547 -> TypeTrace<'tcx> {
1550 values: Types(expected_found(a_is_expected, a, b))
1554 pub fn dummy(tcx: &ty::ctxt<'tcx>) -> TypeTrace<'tcx> {
1556 origin: Misc(codemap::DUMMY_SP),
1557 values: Types(ty::ExpectedFound {
1558 expected: tcx.types.err,
1559 found: tcx.types.err,
1565 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1566 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1567 write!(f, "TypeTrace({:?})", self.origin)
1572 pub fn span(&self) -> Span {
1574 MethodCompatCheck(span) => span,
1575 ExprAssignable(span) => span,
1577 RelateTraitRefs(span) => span,
1578 RelateSelfType(span) => span,
1579 RelateOutputImplTypes(span) => span,
1580 MatchExpressionArm(match_span, _) => match_span,
1581 IfExpression(span) => span,
1582 IfExpressionWithNoElse(span) => span,
1583 RangeExpression(span) => span,
1584 EquatePredicate(span) => span,
1589 impl<'tcx> SubregionOrigin<'tcx> {
1590 pub fn span(&self) -> Span {
1592 RFC1214Subregion(ref a) => a.span(),
1593 Subtype(ref a) => a.span(),
1594 InfStackClosure(a) => a,
1595 InvokeClosure(a) => a,
1596 DerefPointer(a) => a,
1597 FreeVariable(a, _) => a,
1599 RelateObjectBound(a) => a,
1600 RelateParamBound(a, _) => a,
1601 RelateRegionParamBound(a) => a,
1602 RelateDefaultParamBound(a, _) => a,
1604 ReborrowUpvar(a, _) => a,
1605 DataBorrowed(_, a) => a,
1606 ReferenceOutlivesReferent(_, a) => a,
1607 ParameterInScope(_, a) => a,
1608 ExprTypeIsNotInScope(_, a) => a,
1609 BindingTypeIsNotValidAtDecl(a) => a,
1616 SafeDestructor(a) => a,
1621 impl RegionVariableOrigin {
1622 pub fn span(&self) -> Span {
1624 MiscVariable(a) => a,
1625 PatternRegion(a) => a,
1626 AddrOfRegion(a) => a,
1629 EarlyBoundRegion(a, _) => a,
1630 LateBoundRegion(a, _, _) => a,
1631 BoundRegionInCoherence(_) => codemap::DUMMY_SP,
1632 UpvarRegion(_, a) => a