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};
43 use self::combine::CombineFields;
44 use self::region_inference::{RegionVarBindings, RegionSnapshot};
45 use self::error_reporting::ErrorReporting;
46 use self::unify_key::ToType;
51 pub mod error_reporting;
56 pub mod region_inference;
60 pub mod type_variable;
63 pub type Bound<T> = Option<T>;
64 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
65 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
67 pub struct InferCtxt<'a, 'tcx: 'a> {
68 pub tcx: &'a ty::ctxt<'tcx>,
70 pub tables: &'a RefCell<ty::Tables<'tcx>>,
72 // We instantiate UnificationTable with bounds<Ty> because the
73 // types that might instantiate a general type variable have an
74 // order, represented by its upper and lower bounds.
75 type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
77 // Map from integral variable to the kind of integer it represents
78 int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
80 // Map from floating variable to the kind of float it represents
81 float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
83 // For region variables.
84 region_vars: RegionVarBindings<'a, 'tcx>,
86 pub parameter_environment: ty::ParameterEnvironment<'a, 'tcx>,
88 pub fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
90 // This is a temporary field used for toggling on normalization in the inference context,
91 // as we move towards the approach described here:
92 // https://internals.rust-lang.org/t/flattening-the-contexts-for-fun-and-profit/2293
93 // At a point sometime in the future normalization will be done by the typing context
97 err_count_on_creation: usize,
99 // Default Type Parameter fallbacks
100 pub defaults: RefCell<FnvHashMap<Ty<'tcx>, Ty<'tcx>>>,
103 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
104 /// region that each late-bound region was replaced with.
105 pub type SkolemizationMap = FnvHashMap<ty::BoundRegion,ty::Region>;
107 /// Why did we require that the two types be related?
109 /// See `error_reporting.rs` for more details
110 #[derive(Clone, Copy, Debug)]
111 pub enum TypeOrigin {
112 // Not yet categorized in a better way
115 // Checking that method of impl is compatible with trait
116 MethodCompatCheck(Span),
118 // Checking that this expression can be assigned where it needs to be
119 // FIXME(eddyb) #11161 is the original Expr required?
120 ExprAssignable(Span),
122 // Relating trait refs when resolving vtables
123 RelateTraitRefs(Span),
125 // Relating self types when resolving vtables
126 RelateSelfType(Span),
128 // Relating trait type parameters to those found in impl etc
129 RelateOutputImplTypes(Span),
131 // Computing common supertype in the arms of a match expression
132 MatchExpressionArm(Span, Span),
134 // Computing common supertype in an if expression
137 // Computing common supertype of an if expression with no else counter-part
138 IfExpressionWithNoElse(Span),
140 // Computing common supertype in a range expression
141 RangeExpression(Span),
144 EquatePredicate(Span),
148 fn as_str(&self) -> &'static str {
150 &TypeOrigin::Misc(_) |
151 &TypeOrigin::RelateSelfType(_) |
152 &TypeOrigin::RelateOutputImplTypes(_) |
153 &TypeOrigin::ExprAssignable(_) => "mismatched types",
154 &TypeOrigin::RelateTraitRefs(_) => "mismatched traits",
155 &TypeOrigin::MethodCompatCheck(_) => "method not compatible with trait",
156 &TypeOrigin::MatchExpressionArm(_, _) => "match arms have incompatible types",
157 &TypeOrigin::IfExpression(_) => "if and else have incompatible types",
158 &TypeOrigin::IfExpressionWithNoElse(_) => "if may be missing an else clause",
159 &TypeOrigin::RangeExpression(_) => "start and end of range have incompatible types",
160 &TypeOrigin::EquatePredicate(_) => "equality predicate not satisfied",
165 impl fmt::Display for TypeOrigin {
166 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error> {
167 fmt::Display::fmt(self.as_str(), f)
171 /// See `error_reporting.rs` for more details
172 #[derive(Clone, Debug)]
173 pub enum ValuePairs<'tcx> {
174 Types(ty::ExpectedFound<Ty<'tcx>>),
175 TraitRefs(ty::ExpectedFound<ty::TraitRef<'tcx>>),
176 PolyTraitRefs(ty::ExpectedFound<ty::PolyTraitRef<'tcx>>),
179 /// The trace designates the path through inference that we took to
180 /// encounter an error or subtyping constraint.
182 /// See `error_reporting.rs` for more details.
184 pub struct TypeTrace<'tcx> {
186 values: ValuePairs<'tcx>,
189 /// The origin of a `r1 <= r2` constraint.
191 /// See `error_reporting.rs` for more details
192 #[derive(Clone, Debug)]
193 pub enum SubregionOrigin<'tcx> {
194 // 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 // (&'a &'b T) where a >= b
236 ReferenceOutlivesReferent(Ty<'tcx>, Span),
238 // The type T of an expression E must outlive the lifetime for E.
239 ExprTypeIsNotInScope(Ty<'tcx>, Span),
241 // A `ref b` whose region does not enclose the decl site
242 BindingTypeIsNotValidAtDecl(Span),
244 // Regions appearing in a method receiver must outlive method call
247 // Regions appearing in a function argument must outlive func call
250 // Region in return type of invoked fn must enclose call
253 // Operands must be in scope
256 // Region resulting from a `&` expr must enclose the `&` expr
259 // An auto-borrow that does not enclose the expr where it occurs
262 // Region constraint arriving from destructor safety
263 SafeDestructor(Span),
266 /// Times when we replace late-bound regions with variables:
267 #[derive(Clone, Copy, Debug)]
268 pub enum LateBoundRegionConversionTime {
269 /// when a fn is called
272 /// when two higher-ranked types are compared
275 /// when projecting an associated type
276 AssocTypeProjection(ast::Name),
279 /// Reasons to create a region inference variable
281 /// See `error_reporting.rs` for more details
282 #[derive(Clone, Debug)]
283 pub enum RegionVariableOrigin {
284 // Region variables created for ill-categorized reasons,
285 // mostly indicates places in need of refactoring
288 // Regions created by a `&P` or `[...]` pattern
291 // Regions created by `&` operator
294 // Regions created as part of an autoref of a method receiver
297 // Regions created as part of an automatic coercion
300 // Region variables created as the values for early-bound regions
301 EarlyBoundRegion(Span, ast::Name),
303 // Region variables created for bound regions
304 // in a function or method that is called
305 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
307 UpvarRegion(ty::UpvarId, Span),
309 BoundRegionInCoherence(ast::Name),
312 #[derive(Copy, Clone, Debug)]
313 pub enum FixupError {
314 UnresolvedIntTy(IntVid),
315 UnresolvedFloatTy(FloatVid),
319 pub fn fixup_err_to_string(f: FixupError) -> String {
320 use self::FixupError::*;
323 UnresolvedIntTy(_) => {
324 "cannot determine the type of this integer; add a suffix to \
325 specify the type explicitly".to_string()
327 UnresolvedFloatTy(_) => {
328 "cannot determine the type of this number; add a suffix to specify \
329 the type explicitly".to_string()
331 UnresolvedTy(_) => "unconstrained type".to_string(),
335 /// errors_will_be_reported is required to proxy to the fulfillment context
336 /// FIXME -- a better option would be to hold back on modifying
337 /// the global cache until we know that all dependent obligations
338 /// are also satisfied. In that case, we could actually remove
339 /// this boolean flag, and we'd also avoid the problem of squelching
340 /// duplicate errors that occur across fns.
341 pub fn new_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
342 tables: &'a RefCell<ty::Tables<'tcx>>,
343 param_env: Option<ty::ParameterEnvironment<'a, 'tcx>>,
344 errors_will_be_reported: bool)
345 -> InferCtxt<'a, 'tcx> {
349 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
350 int_unification_table: RefCell::new(UnificationTable::new()),
351 float_unification_table: RefCell::new(UnificationTable::new()),
352 region_vars: RegionVarBindings::new(tcx),
353 parameter_environment: param_env.unwrap_or(tcx.empty_parameter_environment()),
354 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new(errors_will_be_reported)),
356 err_count_on_creation: tcx.sess.err_count(),
357 defaults: RefCell::new(FnvHashMap()),
361 pub fn normalizing_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
362 tables: &'a RefCell<ty::Tables<'tcx>>)
363 -> InferCtxt<'a, 'tcx> {
364 let mut infcx = new_infer_ctxt(tcx, tables, None, false);
365 infcx.normalize = true;
369 /// Computes the least upper-bound of `a` and `b`. If this is not possible, reports an error and
371 pub fn common_supertype<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
378 debug!("common_supertype({:?}, {:?})",
381 let trace = TypeTrace {
383 values: Types(expected_found(a_is_expected, a, b))
386 let result = cx.commit_if_ok(|_| cx.lub(a_is_expected, trace.clone()).relate(&a, &b));
390 cx.report_and_explain_type_error(trace, err);
396 pub fn mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
403 debug!("mk_subty({:?} <: {:?})", a, b);
404 cx.sub_types(a_is_expected, origin, a, b)
407 pub fn can_mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
410 -> UnitResult<'tcx> {
411 debug!("can_mk_subty({:?} <: {:?})", a, b);
413 let trace = TypeTrace {
414 origin: Misc(codemap::DUMMY_SP),
415 values: Types(expected_found(true, a, b))
417 cx.sub(true, trace).relate(&a, &b).map(|_| ())
421 pub fn can_mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>, a: Ty<'tcx>, b: Ty<'tcx>)
424 cx.can_equate(&a, &b)
427 pub fn mk_subr<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
428 origin: SubregionOrigin<'tcx>,
431 debug!("mk_subr({:?} <: {:?})", a, b);
432 let snapshot = cx.region_vars.start_snapshot();
433 cx.region_vars.make_subregion(origin, a, b);
434 cx.region_vars.commit(snapshot);
437 pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
444 debug!("mk_eqty({:?} <: {:?})", a, b);
445 cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
448 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
451 a: ty::PolyTraitRef<'tcx>,
452 b: ty::PolyTraitRef<'tcx>)
455 debug!("mk_sub_trait_refs({:?} <: {:?})",
457 cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
460 fn expected_found<T>(a_is_expected: bool,
463 -> ty::ExpectedFound<T>
466 ty::ExpectedFound {expected: a, found: b}
468 ty::ExpectedFound {expected: b, found: a}
472 #[must_use = "once you start a snapshot, you should always consume it"]
473 pub struct CombinedSnapshot {
474 type_snapshot: type_variable::Snapshot,
475 int_snapshot: unify::Snapshot<ty::IntVid>,
476 float_snapshot: unify::Snapshot<ty::FloatVid>,
477 region_vars_snapshot: RegionSnapshot,
480 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
481 where T : TypeFoldable<'tcx> + HasTypeFlags
483 debug!("normalize_associated_type(t={:?})", value);
485 let value = erase_regions(tcx, value);
487 if !value.has_projection_types() {
491 let infcx = new_infer_ctxt(tcx, &tcx.tables, None, true);
492 let mut selcx = traits::SelectionContext::new(&infcx);
493 let cause = traits::ObligationCause::dummy();
494 let traits::Normalized { value: result, obligations } =
495 traits::normalize(&mut selcx, cause, &value);
497 debug!("normalize_associated_type: result={:?} obligations={:?}",
501 let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
503 for obligation in obligations {
504 fulfill_cx.register_predicate_obligation(&infcx, obligation);
507 let result = drain_fulfillment_cx_or_panic(DUMMY_SP, &infcx, &mut fulfill_cx, &result);
512 pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
513 infcx: &InferCtxt<'a,'tcx>,
514 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
517 where T : TypeFoldable<'tcx>
519 match drain_fulfillment_cx(infcx, fulfill_cx, result) {
522 infcx.tcx.sess.span_bug(
524 &format!("Encountered errors `{:?}` fulfilling during trans",
530 /// Finishes processes any obligations that remain in the fulfillment
531 /// context, and then "freshens" and returns `result`. This is
532 /// primarily used during normalization and other cases where
533 /// processing the obligations in `fulfill_cx` may cause type
534 /// inference variables that appear in `result` to be unified, and
535 /// hence we need to process those obligations to get the complete
536 /// picture of the type.
537 pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
538 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
540 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
541 where T : TypeFoldable<'tcx>
543 debug!("drain_fulfillment_cx(result={:?})",
546 // In principle, we only need to do this so long as `result`
547 // contains unbound type parameters. It could be a slight
548 // optimization to stop iterating early.
549 match fulfill_cx.select_all_or_error(infcx) {
556 // Use freshen to simultaneously replace all type variables with
557 // their bindings and replace all regions with 'static. This is
558 // sort of overkill because we do not expect there to be any
559 // unbound type variables, hence no `TyFresh` types should ever be
561 Ok(result.fold_with(&mut infcx.freshener()))
564 /// Returns an equivalent value with all free regions removed (note
565 /// that late-bound regions remain, because they are important for
566 /// subtyping, but they are anonymized and normalized as well). This
567 /// is a stronger, caching version of `ty_fold::erase_regions`.
568 pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
569 where T : TypeFoldable<'tcx>
571 let value1 = value.fold_with(&mut RegionEraser(cx));
572 debug!("erase_regions({:?}) = {:?}",
576 struct RegionEraser<'a, 'tcx: 'a>(&'a ty::ctxt<'tcx>);
578 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
579 fn tcx(&self) -> &ty::ctxt<'tcx> { self.0 }
581 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
582 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
587 let t_norm = ty_fold::super_fold_ty(self, ty);
588 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
592 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
593 where T : TypeFoldable<'tcx>
595 let u = self.tcx().anonymize_late_bound_regions(t);
596 ty_fold::super_fold_binder(self, &u)
599 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
600 // because late-bound regions affect subtyping, we can't
601 // erase the bound/free distinction, but we can replace
602 // all free regions with 'static.
604 // Note that we *CAN* replace early-bound regions -- the
605 // type system never "sees" those, they get substituted
606 // away. In trans, they will always be erased to 'static
607 // whenever a substitution occurs.
609 ty::ReLateBound(..) => r,
614 fn fold_substs(&mut self,
615 substs: &subst::Substs<'tcx>)
616 -> subst::Substs<'tcx> {
617 subst::Substs { regions: subst::ErasedRegions,
618 types: substs.types.fold_with(self) }
623 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
624 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
625 t.fold_with(&mut self.freshener())
628 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
630 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
635 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
636 freshen::TypeFreshener::new(self)
639 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
640 use middle::ty::UnconstrainedNumeric::{Neither, UnconstrainedInt, UnconstrainedFloat};
642 ty::TyInfer(ty::IntVar(vid)) => {
643 if self.int_unification_table.borrow_mut().has_value(vid) {
649 ty::TyInfer(ty::FloatVar(vid)) => {
650 if self.float_unification_table.borrow_mut().has_value(vid) {
660 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
661 let mut variables = Vec::new();
663 let unbound_ty_vars = self.type_variables
665 .unsolved_variables()
666 .into_iter().map(|t| self.tcx.mk_var(t));
668 let unbound_int_vars = self.int_unification_table
670 .unsolved_variables()
671 .into_iter().map(|v| self.tcx.mk_int_var(v));
673 let unbound_float_vars = self.float_unification_table
675 .unsolved_variables()
676 .into_iter().map(|v| self.tcx.mk_float_var(v));
678 variables.extend(unbound_ty_vars);
679 variables.extend(unbound_int_vars);
680 variables.extend(unbound_float_vars);
684 fn combine_fields(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
685 -> CombineFields<'a, 'tcx> {
686 CombineFields {infcx: self,
687 a_is_expected: a_is_expected,
692 // public so that it can be used from the rustc_driver unit tests
693 pub fn equate(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
694 -> equate::Equate<'a, 'tcx>
696 self.combine_fields(a_is_expected, trace).equate()
699 // public so that it can be used from the rustc_driver unit tests
700 pub fn sub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
701 -> sub::Sub<'a, 'tcx>
703 self.combine_fields(a_is_expected, trace).sub()
706 // public so that it can be used from the rustc_driver unit tests
707 pub fn lub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
708 -> lub::Lub<'a, 'tcx>
710 self.combine_fields(a_is_expected, trace).lub()
713 // public so that it can be used from the rustc_driver unit tests
714 pub fn glb(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
715 -> glb::Glb<'a, 'tcx>
717 self.combine_fields(a_is_expected, trace).glb()
720 fn start_snapshot(&self) -> CombinedSnapshot {
722 type_snapshot: self.type_variables.borrow_mut().snapshot(),
723 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
724 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
725 region_vars_snapshot: self.region_vars.start_snapshot(),
729 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
730 debug!("rollback_to(cause={})", cause);
731 let CombinedSnapshot { type_snapshot,
734 region_vars_snapshot } = snapshot;
738 .rollback_to(type_snapshot);
739 self.int_unification_table
741 .rollback_to(int_snapshot);
742 self.float_unification_table
744 .rollback_to(float_snapshot);
746 .rollback_to(region_vars_snapshot);
749 fn commit_from(&self, snapshot: CombinedSnapshot) {
750 debug!("commit_from!");
751 let CombinedSnapshot { type_snapshot,
754 region_vars_snapshot } = snapshot;
758 .commit(type_snapshot);
759 self.int_unification_table
761 .commit(int_snapshot);
762 self.float_unification_table
764 .commit(float_snapshot);
766 .commit(region_vars_snapshot);
769 /// Execute `f` and commit the bindings
770 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
774 let snapshot = self.start_snapshot();
776 self.commit_from(snapshot);
780 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
781 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
782 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
784 debug!("commit_if_ok()");
785 let snapshot = self.start_snapshot();
786 let r = f(&snapshot);
787 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
789 Ok(_) => { self.commit_from(snapshot); }
790 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
795 /// Execute `f` and commit only the region bindings if successful.
796 /// The function f must be very careful not to leak any non-region
797 /// variables that get created.
798 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
799 F: FnOnce() -> Result<T, E>
801 debug!("commit_regions_if_ok()");
802 let CombinedSnapshot { type_snapshot,
805 region_vars_snapshot } = self.start_snapshot();
807 let r = self.commit_if_ok(|_| f());
809 debug!("commit_regions_if_ok: rolling back everything but regions");
811 // Roll back any non-region bindings - they should be resolved
812 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
815 .rollback_to(type_snapshot);
816 self.int_unification_table
818 .rollback_to(int_snapshot);
819 self.float_unification_table
821 .rollback_to(float_snapshot);
823 // Commit region vars that may escape through resolved types.
825 .commit(region_vars_snapshot);
830 /// Execute `f` then unroll any bindings it creates
831 pub fn probe<R, F>(&self, f: F) -> R where
832 F: FnOnce(&CombinedSnapshot) -> R,
835 let snapshot = self.start_snapshot();
836 let r = f(&snapshot);
837 self.rollback_to("probe", snapshot);
841 pub fn add_given(&self,
845 self.region_vars.add_given(sub, sup);
848 pub fn sub_types(&self,
855 debug!("sub_types({:?} <: {:?})", a, b);
856 self.commit_if_ok(|_| {
857 let trace = TypeTrace::types(origin, a_is_expected, a, b);
858 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
862 pub fn eq_types(&self,
869 self.commit_if_ok(|_| {
870 let trace = TypeTrace::types(origin, a_is_expected, a, b);
871 self.equate(a_is_expected, trace).relate(&a, &b).map(|_| ())
875 pub fn sub_trait_refs(&self,
878 a: ty::TraitRef<'tcx>,
879 b: ty::TraitRef<'tcx>)
882 debug!("sub_trait_refs({:?} <: {:?})",
885 self.commit_if_ok(|_| {
886 let trace = TypeTrace {
888 values: TraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
890 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
894 pub fn sub_poly_trait_refs(&self,
897 a: ty::PolyTraitRef<'tcx>,
898 b: ty::PolyTraitRef<'tcx>)
901 debug!("sub_poly_trait_refs({:?} <: {:?})",
904 self.commit_if_ok(|_| {
905 let trace = TypeTrace {
907 values: PolyTraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
909 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
913 pub fn construct_skolemized_subst(&self,
914 generics: &ty::Generics<'tcx>,
915 snapshot: &CombinedSnapshot)
916 -> (subst::Substs<'tcx>, SkolemizationMap) {
917 /*! See `higher_ranked::construct_skolemized_subst` */
919 higher_ranked::construct_skolemized_substs(self, generics, snapshot)
922 pub fn skolemize_late_bound_regions<T>(&self,
923 value: &ty::Binder<T>,
924 snapshot: &CombinedSnapshot)
925 -> (T, SkolemizationMap)
926 where T : TypeFoldable<'tcx>
928 /*! See `higher_ranked::skolemize_late_bound_regions` */
930 higher_ranked::skolemize_late_bound_regions(self, value, snapshot)
933 pub fn leak_check(&self,
934 skol_map: &SkolemizationMap,
935 snapshot: &CombinedSnapshot)
938 /*! See `higher_ranked::leak_check` */
940 match higher_ranked::leak_check(self, skol_map, snapshot) {
942 Err((br, r)) => Err(TypeError::RegionsInsufficientlyPolymorphic(br, r))
946 pub fn plug_leaks<T>(&self,
947 skol_map: SkolemizationMap,
948 snapshot: &CombinedSnapshot,
951 where T : TypeFoldable<'tcx>
953 /*! See `higher_ranked::plug_leaks` */
955 higher_ranked::plug_leaks(self, skol_map, snapshot, value)
958 pub fn equality_predicate(&self,
960 predicate: &ty::PolyEquatePredicate<'tcx>)
961 -> UnitResult<'tcx> {
962 self.commit_if_ok(|snapshot| {
963 let (ty::EquatePredicate(a, b), skol_map) =
964 self.skolemize_late_bound_regions(predicate, snapshot);
965 let origin = EquatePredicate(span);
966 let () = try!(mk_eqty(self, false, origin, a, b));
967 self.leak_check(&skol_map, snapshot)
971 pub fn region_outlives_predicate(&self,
973 predicate: &ty::PolyRegionOutlivesPredicate)
974 -> UnitResult<'tcx> {
975 self.commit_if_ok(|snapshot| {
976 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
977 self.skolemize_late_bound_regions(predicate, snapshot);
978 let origin = RelateRegionParamBound(span);
979 let () = mk_subr(self, origin, r_b, r_a); // `b : a` ==> `a <= b`
980 self.leak_check(&skol_map, snapshot)
984 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
990 pub fn next_ty_var(&self) -> Ty<'tcx> {
991 self.tcx.mk_var(self.next_ty_var_id(false))
994 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
995 self.tcx.mk_var(self.next_ty_var_id(true))
998 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
999 (0..n).map(|_i| self.next_ty_var()).collect()
1002 pub fn next_int_var_id(&self) -> IntVid {
1003 self.int_unification_table
1008 pub fn next_float_var_id(&self) -> FloatVid {
1009 self.float_unification_table
1014 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region {
1015 ty::ReInfer(ty::ReVar(self.region_vars.new_region_var(origin)))
1018 pub fn region_vars_for_defs(&self,
1020 defs: &[ty::RegionParameterDef])
1021 -> Vec<ty::Region> {
1023 .map(|d| self.next_region_var(EarlyBoundRegion(span, d.name)))
1027 pub fn type_vars_for_defs(&self,
1028 defs: &[ty::TypeParameterDef<'tcx>])
1029 -> Vec<ty::Ty<'tcx>> {
1030 let mut vars = Vec::with_capacity(defs.len());
1032 for def in defs.iter() {
1033 let ty_var = self.next_ty_var();
1036 Some(default) => { self.defaults.borrow_mut().insert(ty_var, default); }
1044 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1045 /// type/region parameter to a fresh inference variable.
1046 pub fn fresh_substs_for_generics(&self,
1048 generics: &ty::Generics<'tcx>)
1049 -> subst::Substs<'tcx>
1051 let mut type_params = subst::VecPerParamSpace::empty();
1053 for space in subst::ParamSpace::all().iter() {
1054 type_params.replace(*space, self.type_vars_for_defs(generics.types.get_slice(*space)))
1058 generics.regions.map(
1059 |d| self.next_region_var(EarlyBoundRegion(span, d.name)));
1060 subst::Substs::new(type_params, region_params)
1063 /// Given a set of generics defined on a trait, returns a substitution mapping each output
1064 /// type/region parameter to a fresh inference variable, and mapping the self type to
1066 pub fn fresh_substs_for_trait(&self,
1068 generics: &ty::Generics<'tcx>,
1070 -> subst::Substs<'tcx>
1073 assert!(generics.types.len(subst::SelfSpace) == 1);
1074 assert!(generics.types.len(subst::FnSpace) == 0);
1075 assert!(generics.regions.len(subst::SelfSpace) == 0);
1076 assert!(generics.regions.len(subst::FnSpace) == 0);
1078 let type_parameter_defs = generics.types.get_slice(subst::TypeSpace);
1079 let type_parameters = self.type_vars_for_defs(type_parameter_defs);
1081 let region_param_defs = generics.regions.get_slice(subst::TypeSpace);
1082 let regions = self.region_vars_for_defs(span, region_param_defs);
1084 subst::Substs::new_trait(type_parameters, regions, self_ty)
1087 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {
1088 self.region_vars.new_bound(debruijn)
1091 /// Apply `adjustment` to the type of `expr`
1092 pub fn adjust_expr_ty(&self,
1094 adjustment: Option<&ty::AutoAdjustment<'tcx>>)
1097 let raw_ty = self.expr_ty(expr);
1098 let raw_ty = self.shallow_resolve(raw_ty);
1099 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1100 raw_ty.adjust(self.tcx,
1104 |method_call| self.tables
1108 .map(|method| resolve_ty(method.ty)))
1111 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1112 match self.tables.borrow().node_types.get(&id) {
1115 None if self.tcx.sess.err_count() - self.err_count_on_creation != 0 =>
1119 &format!("no type for node {}: {} in fcx",
1120 id, self.tcx.map.node_to_string(id)));
1125 pub fn expr_ty(&self, ex: &ast::Expr) -> Ty<'tcx> {
1126 match self.tables.borrow().node_types.get(&ex.id) {
1129 self.tcx.sess.bug(&format!("no type for expr in fcx"));
1134 pub fn resolve_regions_and_report_errors(&self,
1135 free_regions: &FreeRegionMap,
1136 subject_node_id: ast::NodeId) {
1137 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1138 self.report_region_errors(&errors); // see error_reporting.rs
1141 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1142 self.resolve_type_vars_if_possible(&t).to_string()
1145 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1146 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1147 format!("({})", tstrs.join(", "))
1150 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1151 self.resolve_type_vars_if_possible(t).to_string()
1154 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1156 ty::TyInfer(ty::TyVar(v)) => {
1157 // Not entirely obvious: if `typ` is a type variable,
1158 // it can be resolved to an int/float variable, which
1159 // can then be recursively resolved, hence the
1160 // recursion. Note though that we prevent type
1161 // variables from unifying to other type variables
1162 // directly (though they may be embedded
1163 // structurally), and we prevent cycles in any case,
1164 // so this recursion should always be of very limited
1166 self.type_variables.borrow()
1168 .map(|t| self.shallow_resolve(t))
1172 ty::TyInfer(ty::IntVar(v)) => {
1173 self.int_unification_table
1176 .map(|v| v.to_type(self.tcx))
1180 ty::TyInfer(ty::FloatVar(v)) => {
1181 self.float_unification_table
1184 .map(|v| v.to_type(self.tcx))
1194 pub fn resolve_type_vars_if_possible<T:TypeFoldable<'tcx>>(&self, value: &T) -> T {
1196 * Where possible, replaces type/int/float variables in
1197 * `value` with their final value. Note that region variables
1198 * are unaffected. If a type variable has not been unified, it
1199 * is left as is. This is an idempotent operation that does
1200 * not affect inference state in any way and so you can do it
1204 let mut r = resolve::OpportunisticTypeResolver::new(self);
1205 value.fold_with(&mut r)
1208 /// Resolves all type variables in `t` and then, if any were left
1209 /// unresolved, substitutes an error type. This is used after the
1210 /// main checking when doing a second pass before writeback. The
1211 /// justification is that writeback will produce an error for
1212 /// these unconstrained type variables.
1213 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1214 let ty = self.resolve_type_vars_if_possible(t);
1215 if ty.references_error() || ty.is_ty_var() {
1216 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1223 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1225 * Attempts to resolve all type/region variables in
1226 * `value`. Region inference must have been run already (e.g.,
1227 * by calling `resolve_regions_and_report_errors`). If some
1228 * variable was never unified, an `Err` results.
1230 * This method is idempotent, but it not typically not invoked
1231 * except during the writeback phase.
1234 resolve::fully_resolve(self, value)
1237 // [Note-Type-error-reporting]
1238 // An invariant is that anytime the expected or actual type is TyError (the special
1239 // error type, meaning that an error occurred when typechecking this expression),
1240 // this is a derived error. The error cascaded from another error (that was already
1241 // reported), so it's not useful to display it to the user.
1242 // The following four methods -- type_error_message_str, type_error_message_str_with_expected,
1243 // type_error_message, and report_mismatched_types -- implement this logic.
1244 // They check if either the actual or expected type is TyError, and don't print the error
1245 // in this case. The typechecker should only ever report type errors involving mismatched
1246 // types using one of these four methods, and should not call span_err directly for such
1248 pub fn type_error_message_str<M>(&self,
1252 err: Option<&ty::TypeError<'tcx>>) where
1253 M: FnOnce(Option<String>, String) -> String,
1255 self.type_error_message_str_with_expected(sp, mk_msg, None, actual_ty, err)
1258 pub fn type_error_message_str_with_expected<M>(&self,
1261 expected_ty: Option<Ty<'tcx>>,
1263 err: Option<&ty::TypeError<'tcx>>) where
1264 M: FnOnce(Option<String>, String) -> String,
1266 debug!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
1268 let resolved_expected = expected_ty.map(|e_ty| self.resolve_type_vars_if_possible(&e_ty));
1270 if !resolved_expected.references_error() {
1271 let error_str = err.map_or("".to_string(), |t_err| {
1272 format!(" ({})", t_err)
1275 self.tcx.sess.span_err(sp, &format!("{}{}",
1276 mk_msg(resolved_expected.map(|t| self.ty_to_string(t)), actual_ty),
1279 if let Some(err) = err {
1280 self.tcx.note_and_explain_type_err(err, sp)
1285 pub fn type_error_message<M>(&self,
1288 actual_ty: Ty<'tcx>,
1289 err: Option<&ty::TypeError<'tcx>>) where
1290 M: FnOnce(String) -> String,
1292 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1294 // Don't report an error if actual type is TyError.
1295 if actual_ty.references_error() {
1299 self.type_error_message_str(sp,
1300 move |_e, a| { mk_msg(a) },
1301 self.ty_to_string(actual_ty), err);
1304 pub fn report_mismatched_types(&self,
1308 err: &ty::TypeError<'tcx>) {
1309 let trace = TypeTrace {
1311 values: Types(ty::ExpectedFound {
1316 self.report_and_explain_type_error(trace, err);
1319 pub fn report_conflicting_default_types(&self,
1323 let trace = TypeTrace {
1325 values: Types(ty::expected_found {
1331 self.report_and_explain_type_error(trace,
1332 &ty::type_err::terr_ty_param_default_mismatch(ty::expected_found {
1338 pub fn replace_late_bound_regions_with_fresh_var<T>(
1341 lbrct: LateBoundRegionConversionTime,
1342 value: &ty::Binder<T>)
1343 -> (T, FnvHashMap<ty::BoundRegion,ty::Region>)
1344 where T : TypeFoldable<'tcx>
1346 ty_fold::replace_late_bound_regions(
1349 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1352 /// See `verify_generic_bound` method in `region_inference`
1353 pub fn verify_generic_bound(&self,
1354 origin: SubregionOrigin<'tcx>,
1355 kind: GenericKind<'tcx>,
1357 bs: Vec<ty::Region>) {
1358 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1363 self.region_vars.verify_generic_bound(origin, kind, a, bs);
1366 pub fn can_equate<'b,T>(&'b self, a: &T, b: &T) -> UnitResult<'tcx>
1367 where T: Relate<'b,'tcx> + fmt::Debug
1369 debug!("can_equate({:?}, {:?})", a, b);
1371 // Gin up a dummy trace, since this won't be committed
1372 // anyhow. We should make this typetrace stuff more
1373 // generic so we don't have to do anything quite this
1375 let e = self.tcx.types.err;
1376 let trace = TypeTrace { origin: Misc(codemap::DUMMY_SP),
1377 values: Types(expected_found(true, e, e)) };
1378 self.equate(true, trace).relate(a, b)
1382 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1383 let ty = self.node_type(id);
1384 self.resolve_type_vars_or_error(&ty)
1387 pub fn expr_ty_adjusted(&self, expr: &ast::Expr) -> McResult<Ty<'tcx>> {
1388 let ty = self.adjust_expr_ty(expr, self.tables.borrow().adjustments.get(&expr.id));
1389 self.resolve_type_vars_or_error(&ty)
1392 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1393 let ty = self.resolve_type_vars_if_possible(&ty);
1394 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1395 // FIXME(@jroesch): should be able to use:
1396 // ty.moves_by_default(&self.parameter_environment, span)
1399 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1400 -> Option<Ty<'tcx>> {
1405 .map(|method| method.ty)
1406 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1409 pub fn node_method_id(&self, method_call: ty::MethodCall)
1410 -> Option<ast::DefId> {
1415 .map(|method| method.def_id)
1418 pub fn adjustments(&self) -> Ref<NodeMap<ty::AutoAdjustment<'tcx>>> {
1419 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1420 -> &'a NodeMap<ty::AutoAdjustment<'tcx>> {
1424 Ref::map(self.tables.borrow(), project_adjustments)
1427 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1428 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1431 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1432 self.tcx.region_maps.temporary_scope(rvalue_id)
1435 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture> {
1436 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1439 pub fn param_env<'b>(&'b self) -> &'b ty::ParameterEnvironment<'b,'tcx> {
1440 &self.parameter_environment
1443 pub fn closure_kind(&self,
1445 -> Option<ty::ClosureKind>
1447 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1450 pub fn closure_type(&self,
1452 substs: &ty::ClosureSubsts<'tcx>)
1453 -> ty::ClosureTy<'tcx>
1455 let closure_ty = self.tables
1460 .subst(self.tcx, &substs.func_substs);
1463 normalize_associated_type(&self.tcx, &closure_ty)
1470 impl<'tcx> TypeTrace<'tcx> {
1471 pub fn span(&self) -> Span {
1475 pub fn types(origin: TypeOrigin,
1476 a_is_expected: bool,
1479 -> TypeTrace<'tcx> {
1482 values: Types(expected_found(a_is_expected, a, b))
1486 pub fn dummy(tcx: &ty::ctxt<'tcx>) -> TypeTrace<'tcx> {
1488 origin: Misc(codemap::DUMMY_SP),
1489 values: Types(ty::ExpectedFound {
1490 expected: tcx.types.err,
1491 found: tcx.types.err,
1497 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1498 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1499 write!(f, "TypeTrace({:?})", self.origin)
1504 pub fn span(&self) -> Span {
1506 MethodCompatCheck(span) => span,
1507 ExprAssignable(span) => span,
1509 RelateTraitRefs(span) => span,
1510 RelateSelfType(span) => span,
1511 RelateOutputImplTypes(span) => span,
1512 MatchExpressionArm(match_span, _) => match_span,
1513 IfExpression(span) => span,
1514 IfExpressionWithNoElse(span) => span,
1515 RangeExpression(span) => span,
1516 EquatePredicate(span) => span,
1521 impl<'tcx> SubregionOrigin<'tcx> {
1522 pub fn span(&self) -> Span {
1524 Subtype(ref a) => a.span(),
1525 InfStackClosure(a) => a,
1526 InvokeClosure(a) => a,
1527 DerefPointer(a) => a,
1528 FreeVariable(a, _) => a,
1530 RelateObjectBound(a) => a,
1531 RelateParamBound(a, _) => a,
1532 RelateRegionParamBound(a) => a,
1533 RelateDefaultParamBound(a, _) => a,
1535 ReborrowUpvar(a, _) => a,
1536 ReferenceOutlivesReferent(_, a) => a,
1537 ExprTypeIsNotInScope(_, a) => a,
1538 BindingTypeIsNotValidAtDecl(a) => a,
1545 SafeDestructor(a) => a,
1550 impl RegionVariableOrigin {
1551 pub fn span(&self) -> Span {
1553 MiscVariable(a) => a,
1554 PatternRegion(a) => a,
1555 AddrOfRegion(a) => a,
1558 EarlyBoundRegion(a, _) => a,
1559 LateBoundRegion(a, _, _) => a,
1560 BoundRegionInCoherence(_) => codemap::DUMMY_SP,
1561 UpvarRegion(_, a) => a