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,
100 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
101 /// region that each late-bound region was replaced with.
102 pub type SkolemizationMap = FnvHashMap<ty::BoundRegion,ty::Region>;
104 /// Why did we require that the two types be related?
106 /// See `error_reporting.rs` for more details
107 #[derive(Clone, Copy, Debug)]
108 pub enum TypeOrigin {
109 // Not yet categorized in a better way
112 // Checking that method of impl is compatible with trait
113 MethodCompatCheck(Span),
115 // Checking that this expression can be assigned where it needs to be
116 // FIXME(eddyb) #11161 is the original Expr required?
117 ExprAssignable(Span),
119 // Relating trait refs when resolving vtables
120 RelateTraitRefs(Span),
122 // Relating self types when resolving vtables
123 RelateSelfType(Span),
125 // Relating trait type parameters to those found in impl etc
126 RelateOutputImplTypes(Span),
128 // Computing common supertype in the arms of a match expression
129 MatchExpressionArm(Span, Span),
131 // Computing common supertype in an if expression
134 // Computing common supertype of an if expression with no else counter-part
135 IfExpressionWithNoElse(Span),
137 // Computing common supertype in a range expression
138 RangeExpression(Span),
141 EquatePredicate(Span),
145 fn as_str(&self) -> &'static str {
147 &TypeOrigin::Misc(_) |
148 &TypeOrigin::RelateSelfType(_) |
149 &TypeOrigin::RelateOutputImplTypes(_) |
150 &TypeOrigin::ExprAssignable(_) => "mismatched types",
151 &TypeOrigin::RelateTraitRefs(_) => "mismatched traits",
152 &TypeOrigin::MethodCompatCheck(_) => "method not compatible with trait",
153 &TypeOrigin::MatchExpressionArm(_, _) => "match arms have incompatible types",
154 &TypeOrigin::IfExpression(_) => "if and else have incompatible types",
155 &TypeOrigin::IfExpressionWithNoElse(_) => "if may be missing an else clause",
156 &TypeOrigin::RangeExpression(_) => "start and end of range have incompatible types",
157 &TypeOrigin::EquatePredicate(_) => "equality predicate not satisfied",
162 impl fmt::Display for TypeOrigin {
163 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error> {
164 fmt::Display::fmt(self.as_str(), f)
168 /// See `error_reporting.rs` for more details
169 #[derive(Clone, Debug)]
170 pub enum ValuePairs<'tcx> {
171 Types(ty::ExpectedFound<Ty<'tcx>>),
172 TraitRefs(ty::ExpectedFound<ty::TraitRef<'tcx>>),
173 PolyTraitRefs(ty::ExpectedFound<ty::PolyTraitRef<'tcx>>),
176 /// The trace designates the path through inference that we took to
177 /// encounter an error or subtyping constraint.
179 /// See `error_reporting.rs` for more details.
181 pub struct TypeTrace<'tcx> {
183 values: ValuePairs<'tcx>,
186 /// The origin of a `r1 <= r2` constraint.
188 /// See `error_reporting.rs` for more details
189 #[derive(Clone, Debug)]
190 pub enum SubregionOrigin<'tcx> {
191 // Arose from a subtyping relation
192 Subtype(TypeTrace<'tcx>),
194 // Stack-allocated closures cannot outlive innermost loop
195 // or function so as to ensure we only require finite stack
196 InfStackClosure(Span),
198 // Invocation of closure must be within its lifetime
201 // Dereference of reference must be within its lifetime
204 // Closure bound must not outlive captured free variables
205 FreeVariable(Span, ast::NodeId),
207 // Index into slice must be within its lifetime
210 // When casting `&'a T` to an `&'b Trait` object,
211 // relating `'a` to `'b`
212 RelateObjectBound(Span),
214 // Some type parameter was instantiated with the given type,
215 // and that type must outlive some region.
216 RelateParamBound(Span, Ty<'tcx>),
218 // The given region parameter was instantiated with a region
219 // that must outlive some other region.
220 RelateRegionParamBound(Span),
222 // A bound placed on type parameters that states that must outlive
223 // the moment of their instantiation.
224 RelateDefaultParamBound(Span, Ty<'tcx>),
226 // Creating a pointer `b` to contents of another reference
229 // Creating a pointer `b` to contents of an upvar
230 ReborrowUpvar(Span, ty::UpvarId),
232 // (&'a &'b T) where a >= b
233 ReferenceOutlivesReferent(Ty<'tcx>, Span),
235 // The type T of an expression E must outlive the lifetime for E.
236 ExprTypeIsNotInScope(Ty<'tcx>, Span),
238 // A `ref b` whose region does not enclose the decl site
239 BindingTypeIsNotValidAtDecl(Span),
241 // Regions appearing in a method receiver must outlive method call
244 // Regions appearing in a function argument must outlive func call
247 // Region in return type of invoked fn must enclose call
250 // Operands must be in scope
253 // Region resulting from a `&` expr must enclose the `&` expr
256 // An auto-borrow that does not enclose the expr where it occurs
259 // Region constraint arriving from destructor safety
260 SafeDestructor(Span),
263 /// Times when we replace late-bound regions with variables:
264 #[derive(Clone, Copy, Debug)]
265 pub enum LateBoundRegionConversionTime {
266 /// when a fn is called
269 /// when two higher-ranked types are compared
272 /// when projecting an associated type
273 AssocTypeProjection(ast::Name),
276 /// Reasons to create a region inference variable
278 /// See `error_reporting.rs` for more details
279 #[derive(Clone, Debug)]
280 pub enum RegionVariableOrigin {
281 // Region variables created for ill-categorized reasons,
282 // mostly indicates places in need of refactoring
285 // Regions created by a `&P` or `[...]` pattern
288 // Regions created by `&` operator
291 // Regions created as part of an autoref of a method receiver
294 // Regions created as part of an automatic coercion
297 // Region variables created as the values for early-bound regions
298 EarlyBoundRegion(Span, ast::Name),
300 // Region variables created for bound regions
301 // in a function or method that is called
302 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
304 UpvarRegion(ty::UpvarId, Span),
306 BoundRegionInCoherence(ast::Name),
309 #[derive(Copy, Clone, Debug)]
310 pub enum FixupError {
311 UnresolvedIntTy(IntVid),
312 UnresolvedFloatTy(FloatVid),
316 pub fn fixup_err_to_string(f: FixupError) -> String {
317 use self::FixupError::*;
320 UnresolvedIntTy(_) => {
321 "cannot determine the type of this integer; add a suffix to \
322 specify the type explicitly".to_string()
324 UnresolvedFloatTy(_) => {
325 "cannot determine the type of this number; add a suffix to specify \
326 the type explicitly".to_string()
328 UnresolvedTy(_) => "unconstrained type".to_string(),
332 /// errors_will_be_reported is required to proxy to the fulfillment context
333 /// FIXME -- a better option would be to hold back on modifying
334 /// the global cache until we know that all dependent obligations
335 /// are also satisfied. In that case, we could actually remove
336 /// this boolean flag, and we'd also avoid the problem of squelching
337 /// duplicate errors that occur across fns.
338 pub fn new_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
339 tables: &'a RefCell<ty::Tables<'tcx>>,
340 param_env: Option<ty::ParameterEnvironment<'a, 'tcx>>,
341 errors_will_be_reported: bool)
342 -> InferCtxt<'a, 'tcx> {
346 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
347 int_unification_table: RefCell::new(UnificationTable::new()),
348 float_unification_table: RefCell::new(UnificationTable::new()),
349 region_vars: RegionVarBindings::new(tcx),
350 parameter_environment: param_env.unwrap_or(tcx.empty_parameter_environment()),
351 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new(errors_will_be_reported)),
353 err_count_on_creation: tcx.sess.err_count()
357 pub fn normalizing_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
358 tables: &'a RefCell<ty::Tables<'tcx>>)
359 -> InferCtxt<'a, 'tcx> {
360 let mut infcx = new_infer_ctxt(tcx, tables, None, false);
361 infcx.normalize = true;
365 /// Computes the least upper-bound of `a` and `b`. If this is not possible, reports an error and
367 pub fn common_supertype<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
374 debug!("common_supertype({:?}, {:?})",
377 let trace = TypeTrace {
379 values: Types(expected_found(a_is_expected, a, b))
382 let result = cx.commit_if_ok(|_| cx.lub(a_is_expected, trace.clone()).relate(&a, &b));
386 cx.report_and_explain_type_error(trace, err);
392 pub fn mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
399 debug!("mk_subty({:?} <: {:?})", a, b);
400 cx.sub_types(a_is_expected, origin, a, b)
403 pub fn can_mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
406 -> UnitResult<'tcx> {
407 debug!("can_mk_subty({:?} <: {:?})", a, b);
409 let trace = TypeTrace {
410 origin: Misc(codemap::DUMMY_SP),
411 values: Types(expected_found(true, a, b))
413 cx.sub(true, trace).relate(&a, &b).map(|_| ())
417 pub fn can_mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>, a: Ty<'tcx>, b: Ty<'tcx>)
420 cx.can_equate(&a, &b)
423 pub fn mk_subr<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
424 origin: SubregionOrigin<'tcx>,
427 debug!("mk_subr({:?} <: {:?})", a, b);
428 let snapshot = cx.region_vars.start_snapshot();
429 cx.region_vars.make_subregion(origin, a, b);
430 cx.region_vars.commit(snapshot);
433 pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
440 debug!("mk_eqty({:?} <: {:?})", a, b);
441 cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
444 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
447 a: ty::PolyTraitRef<'tcx>,
448 b: ty::PolyTraitRef<'tcx>)
451 debug!("mk_sub_trait_refs({:?} <: {:?})",
453 cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
456 fn expected_found<T>(a_is_expected: bool,
459 -> ty::ExpectedFound<T>
462 ty::ExpectedFound {expected: a, found: b}
464 ty::ExpectedFound {expected: b, found: a}
468 #[must_use = "once you start a snapshot, you should always consume it"]
469 pub struct CombinedSnapshot {
470 type_snapshot: type_variable::Snapshot,
471 int_snapshot: unify::Snapshot<ty::IntVid>,
472 float_snapshot: unify::Snapshot<ty::FloatVid>,
473 region_vars_snapshot: RegionSnapshot,
476 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
477 where T : TypeFoldable<'tcx> + HasTypeFlags
479 debug!("normalize_associated_type(t={:?})", value);
481 let value = erase_regions(tcx, value);
483 if !value.has_projection_types() {
487 let infcx = new_infer_ctxt(tcx, &tcx.tables, None, true);
488 let mut selcx = traits::SelectionContext::new(&infcx);
489 let cause = traits::ObligationCause::dummy();
490 let traits::Normalized { value: result, obligations } =
491 traits::normalize(&mut selcx, cause, &value);
493 debug!("normalize_associated_type: result={:?} obligations={:?}",
497 let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
499 for obligation in obligations {
500 fulfill_cx.register_predicate_obligation(&infcx, obligation);
503 let result = drain_fulfillment_cx_or_panic(DUMMY_SP, &infcx, &mut fulfill_cx, &result);
508 pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
509 infcx: &InferCtxt<'a,'tcx>,
510 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
513 where T : TypeFoldable<'tcx>
515 match drain_fulfillment_cx(infcx, fulfill_cx, result) {
518 infcx.tcx.sess.span_bug(
520 &format!("Encountered errors `{:?}` fulfilling during trans",
526 /// Finishes processes any obligations that remain in the fulfillment
527 /// context, and then "freshens" and returns `result`. This is
528 /// primarily used during normalization and other cases where
529 /// processing the obligations in `fulfill_cx` may cause type
530 /// inference variables that appear in `result` to be unified, and
531 /// hence we need to process those obligations to get the complete
532 /// picture of the type.
533 pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
534 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
536 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
537 where T : TypeFoldable<'tcx>
539 debug!("drain_fulfillment_cx(result={:?})",
542 // In principle, we only need to do this so long as `result`
543 // contains unbound type parameters. It could be a slight
544 // optimization to stop iterating early.
545 match fulfill_cx.select_all_or_error(infcx) {
552 // Use freshen to simultaneously replace all type variables with
553 // their bindings and replace all regions with 'static. This is
554 // sort of overkill because we do not expect there to be any
555 // unbound type variables, hence no `TyFresh` types should ever be
557 Ok(result.fold_with(&mut infcx.freshener()))
560 /// Returns an equivalent value with all free regions removed (note
561 /// that late-bound regions remain, because they are important for
562 /// subtyping, but they are anonymized and normalized as well). This
563 /// is a stronger, caching version of `ty_fold::erase_regions`.
564 pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
565 where T : TypeFoldable<'tcx>
567 let value1 = value.fold_with(&mut RegionEraser(cx));
568 debug!("erase_regions({:?}) = {:?}",
572 struct RegionEraser<'a, 'tcx: 'a>(&'a ty::ctxt<'tcx>);
574 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
575 fn tcx(&self) -> &ty::ctxt<'tcx> { self.0 }
577 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
578 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
583 let t_norm = ty_fold::super_fold_ty(self, ty);
584 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
588 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
589 where T : TypeFoldable<'tcx>
591 let u = self.tcx().anonymize_late_bound_regions(t);
592 ty_fold::super_fold_binder(self, &u)
595 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
596 // because late-bound regions affect subtyping, we can't
597 // erase the bound/free distinction, but we can replace
598 // all free regions with 'static.
600 // Note that we *CAN* replace early-bound regions -- the
601 // type system never "sees" those, they get substituted
602 // away. In trans, they will always be erased to 'static
603 // whenever a substitution occurs.
605 ty::ReLateBound(..) => r,
610 fn fold_substs(&mut self,
611 substs: &subst::Substs<'tcx>)
612 -> subst::Substs<'tcx> {
613 subst::Substs { regions: subst::ErasedRegions,
614 types: substs.types.fold_with(self) }
619 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
620 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
621 t.fold_with(&mut self.freshener())
624 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
626 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
631 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
632 freshen::TypeFreshener::new(self)
635 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
636 use middle::ty::UnconstrainedNumeric::{Neither, UnconstrainedInt, UnconstrainedFloat};
638 ty::TyInfer(ty::IntVar(vid)) => {
639 if self.int_unification_table.borrow_mut().has_value(vid) {
645 ty::TyInfer(ty::FloatVar(vid)) => {
646 if self.float_unification_table.borrow_mut().has_value(vid) {
656 /// Returns a type variable's default fallback if any exists. A default
657 /// must be attached to the variable when created, if it is created
658 /// without a default, this will return None.
660 /// See `new_ty_var_with_default` to create a type variable with a default.
661 /// See `type_variable::Default` for details about what a default entails.
662 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
664 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
669 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
670 let mut variables = Vec::new();
672 let unbound_ty_vars = self.type_variables
674 .unsolved_variables()
676 .map(|t| self.tcx.mk_var(t));
678 let unbound_int_vars = self.int_unification_table
680 .unsolved_variables()
682 .map(|v| self.tcx.mk_int_var(v));
684 let unbound_float_vars = self.float_unification_table
686 .unsolved_variables()
688 .map(|v| self.tcx.mk_float_var(v));
690 variables.extend(unbound_ty_vars);
691 variables.extend(unbound_int_vars);
692 variables.extend(unbound_float_vars);
697 fn combine_fields(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
698 -> CombineFields<'a, 'tcx> {
699 CombineFields {infcx: self,
700 a_is_expected: a_is_expected,
705 // public so that it can be used from the rustc_driver unit tests
706 pub fn equate(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
707 -> equate::Equate<'a, 'tcx>
709 self.combine_fields(a_is_expected, trace).equate()
712 // public so that it can be used from the rustc_driver unit tests
713 pub fn sub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
714 -> sub::Sub<'a, 'tcx>
716 self.combine_fields(a_is_expected, trace).sub()
719 // public so that it can be used from the rustc_driver unit tests
720 pub fn lub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
721 -> lub::Lub<'a, 'tcx>
723 self.combine_fields(a_is_expected, trace).lub()
726 // public so that it can be used from the rustc_driver unit tests
727 pub fn glb(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
728 -> glb::Glb<'a, 'tcx>
730 self.combine_fields(a_is_expected, trace).glb()
733 fn start_snapshot(&self) -> CombinedSnapshot {
735 type_snapshot: self.type_variables.borrow_mut().snapshot(),
736 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
737 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
738 region_vars_snapshot: self.region_vars.start_snapshot(),
742 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
743 debug!("rollback_to(cause={})", cause);
744 let CombinedSnapshot { type_snapshot,
747 region_vars_snapshot } = snapshot;
751 .rollback_to(type_snapshot);
752 self.int_unification_table
754 .rollback_to(int_snapshot);
755 self.float_unification_table
757 .rollback_to(float_snapshot);
759 .rollback_to(region_vars_snapshot);
762 fn commit_from(&self, snapshot: CombinedSnapshot) {
763 debug!("commit_from!");
764 let CombinedSnapshot { type_snapshot,
767 region_vars_snapshot } = snapshot;
771 .commit(type_snapshot);
772 self.int_unification_table
774 .commit(int_snapshot);
775 self.float_unification_table
777 .commit(float_snapshot);
779 .commit(region_vars_snapshot);
782 /// Execute `f` and commit the bindings
783 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
787 let snapshot = self.start_snapshot();
789 self.commit_from(snapshot);
793 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
794 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
795 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
797 debug!("commit_if_ok()");
798 let snapshot = self.start_snapshot();
799 let r = f(&snapshot);
800 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
802 Ok(_) => { self.commit_from(snapshot); }
803 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
808 /// Execute `f` and commit only the region bindings if successful.
809 /// The function f must be very careful not to leak any non-region
810 /// variables that get created.
811 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
812 F: FnOnce() -> Result<T, E>
814 debug!("commit_regions_if_ok()");
815 let CombinedSnapshot { type_snapshot,
818 region_vars_snapshot } = self.start_snapshot();
820 let r = self.commit_if_ok(|_| f());
822 debug!("commit_regions_if_ok: rolling back everything but regions");
824 // Roll back any non-region bindings - they should be resolved
825 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
828 .rollback_to(type_snapshot);
829 self.int_unification_table
831 .rollback_to(int_snapshot);
832 self.float_unification_table
834 .rollback_to(float_snapshot);
836 // Commit region vars that may escape through resolved types.
838 .commit(region_vars_snapshot);
843 /// Execute `f` then unroll any bindings it creates
844 pub fn probe<R, F>(&self, f: F) -> R where
845 F: FnOnce(&CombinedSnapshot) -> R,
848 let snapshot = self.start_snapshot();
849 let r = f(&snapshot);
850 self.rollback_to("probe", snapshot);
854 pub fn add_given(&self,
858 self.region_vars.add_given(sub, sup);
861 pub fn sub_types(&self,
868 debug!("sub_types({:?} <: {:?})", a, b);
869 self.commit_if_ok(|_| {
870 let trace = TypeTrace::types(origin, a_is_expected, a, b);
871 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
875 pub fn eq_types(&self,
882 self.commit_if_ok(|_| {
883 let trace = TypeTrace::types(origin, a_is_expected, a, b);
884 self.equate(a_is_expected, trace).relate(&a, &b).map(|_| ())
888 pub fn sub_trait_refs(&self,
891 a: ty::TraitRef<'tcx>,
892 b: ty::TraitRef<'tcx>)
895 debug!("sub_trait_refs({:?} <: {:?})",
898 self.commit_if_ok(|_| {
899 let trace = TypeTrace {
901 values: TraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
903 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
907 pub fn sub_poly_trait_refs(&self,
910 a: ty::PolyTraitRef<'tcx>,
911 b: ty::PolyTraitRef<'tcx>)
914 debug!("sub_poly_trait_refs({:?} <: {:?})",
917 self.commit_if_ok(|_| {
918 let trace = TypeTrace {
920 values: PolyTraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
922 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
926 pub fn construct_skolemized_subst(&self,
927 generics: &ty::Generics<'tcx>,
928 snapshot: &CombinedSnapshot)
929 -> (subst::Substs<'tcx>, SkolemizationMap) {
930 /*! See `higher_ranked::construct_skolemized_subst` */
932 higher_ranked::construct_skolemized_substs(self, generics, snapshot)
935 pub fn skolemize_late_bound_regions<T>(&self,
936 value: &ty::Binder<T>,
937 snapshot: &CombinedSnapshot)
938 -> (T, SkolemizationMap)
939 where T : TypeFoldable<'tcx>
941 /*! See `higher_ranked::skolemize_late_bound_regions` */
943 higher_ranked::skolemize_late_bound_regions(self, value, snapshot)
946 pub fn leak_check(&self,
947 skol_map: &SkolemizationMap,
948 snapshot: &CombinedSnapshot)
951 /*! See `higher_ranked::leak_check` */
953 match higher_ranked::leak_check(self, skol_map, snapshot) {
955 Err((br, r)) => Err(TypeError::RegionsInsufficientlyPolymorphic(br, r))
959 pub fn plug_leaks<T>(&self,
960 skol_map: SkolemizationMap,
961 snapshot: &CombinedSnapshot,
964 where T : TypeFoldable<'tcx>
966 /*! See `higher_ranked::plug_leaks` */
968 higher_ranked::plug_leaks(self, skol_map, snapshot, value)
971 pub fn equality_predicate(&self,
973 predicate: &ty::PolyEquatePredicate<'tcx>)
974 -> UnitResult<'tcx> {
975 self.commit_if_ok(|snapshot| {
976 let (ty::EquatePredicate(a, b), skol_map) =
977 self.skolemize_late_bound_regions(predicate, snapshot);
978 let origin = EquatePredicate(span);
979 let () = try!(mk_eqty(self, false, origin, a, b));
980 self.leak_check(&skol_map, snapshot)
984 pub fn region_outlives_predicate(&self,
986 predicate: &ty::PolyRegionOutlivesPredicate)
987 -> UnitResult<'tcx> {
988 self.commit_if_ok(|snapshot| {
989 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
990 self.skolemize_late_bound_regions(predicate, snapshot);
991 let origin = RelateRegionParamBound(span);
992 let () = mk_subr(self, origin, r_b, r_a); // `b : a` ==> `a <= b`
993 self.leak_check(&skol_map, snapshot)
997 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
1000 .new_var(diverging, None)
1003 pub fn next_ty_var(&self) -> Ty<'tcx> {
1004 self.tcx.mk_var(self.next_ty_var_id(false))
1007 pub fn next_ty_var_with_default(&self,
1008 default: Option<type_variable::Default<'tcx>>) -> Ty<'tcx> {
1009 let ty_var_id = self.type_variables
1011 .new_var(false, default);
1013 self.tcx.mk_var(ty_var_id)
1016 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
1017 self.tcx.mk_var(self.next_ty_var_id(true))
1020 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
1021 (0..n).map(|_i| self.next_ty_var()).collect()
1024 pub fn next_int_var_id(&self) -> IntVid {
1025 self.int_unification_table
1030 pub fn next_float_var_id(&self) -> FloatVid {
1031 self.float_unification_table
1036 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region {
1037 ty::ReInfer(ty::ReVar(self.region_vars.new_region_var(origin)))
1040 pub fn region_vars_for_defs(&self,
1042 defs: &[ty::RegionParameterDef])
1043 -> Vec<ty::Region> {
1045 .map(|d| self.next_region_var(EarlyBoundRegion(span, d.name)))
1049 pub fn type_vars_for_defs(&self,
1050 defs: &[ty::TypeParameterDef<'tcx>])
1051 -> Vec<ty::Ty<'tcx>> {
1052 let mut substs = Substs::empty();
1053 let mut vars = Vec::with_capacity(defs.len());
1055 for def in defs.iter() {
1056 let default = def.default.map(|default| {
1057 type_variable::Default {
1061 //.subst(self.tcx, &substs)
1062 let ty_var = self.next_ty_var_with_default(default);
1063 substs.types.push(subst::ParamSpace::SelfSpace, ty_var);
1070 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1071 /// type/region parameter to a fresh inference variable.
1072 pub fn fresh_substs_for_generics(&self,
1074 generics: &ty::Generics<'tcx>)
1075 -> subst::Substs<'tcx>
1077 let mut type_params = subst::VecPerParamSpace::empty();
1079 for space in subst::ParamSpace::all().iter() {
1080 type_params.replace(*space, self.type_vars_for_defs(generics.types.get_slice(*space)))
1084 generics.regions.map(
1085 |d| self.next_region_var(EarlyBoundRegion(span, d.name)));
1086 subst::Substs::new(type_params, region_params)
1089 /// Given a set of generics defined on a trait, returns a substitution mapping each output
1090 /// type/region parameter to a fresh inference variable, and mapping the self type to
1092 pub fn fresh_substs_for_trait(&self,
1094 generics: &ty::Generics<'tcx>,
1096 -> subst::Substs<'tcx>
1099 assert!(generics.types.len(subst::SelfSpace) == 1);
1100 assert!(generics.types.len(subst::FnSpace) == 0);
1101 assert!(generics.regions.len(subst::SelfSpace) == 0);
1102 assert!(generics.regions.len(subst::FnSpace) == 0);
1104 let type_parameter_defs = generics.types.get_slice(subst::TypeSpace);
1105 let type_parameters = self.type_vars_for_defs(type_parameter_defs);
1107 let region_param_defs = generics.regions.get_slice(subst::TypeSpace);
1108 let regions = self.region_vars_for_defs(span, region_param_defs);
1110 subst::Substs::new_trait(type_parameters, regions, self_ty)
1113 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {
1114 self.region_vars.new_bound(debruijn)
1117 /// Apply `adjustment` to the type of `expr`
1118 pub fn adjust_expr_ty(&self,
1120 adjustment: Option<&ty::AutoAdjustment<'tcx>>)
1123 let raw_ty = self.expr_ty(expr);
1124 let raw_ty = self.shallow_resolve(raw_ty);
1125 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1126 raw_ty.adjust(self.tcx,
1130 |method_call| self.tables
1134 .map(|method| resolve_ty(method.ty)))
1137 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1138 match self.tables.borrow().node_types.get(&id) {
1141 None if self.tcx.sess.err_count() - self.err_count_on_creation != 0 =>
1145 &format!("no type for node {}: {} in fcx",
1146 id, self.tcx.map.node_to_string(id)));
1151 pub fn expr_ty(&self, ex: &ast::Expr) -> Ty<'tcx> {
1152 match self.tables.borrow().node_types.get(&ex.id) {
1155 self.tcx.sess.bug(&format!("no type for expr in fcx"));
1160 pub fn resolve_regions_and_report_errors(&self,
1161 free_regions: &FreeRegionMap,
1162 subject_node_id: ast::NodeId) {
1163 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1164 self.report_region_errors(&errors); // see error_reporting.rs
1167 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1168 self.resolve_type_vars_if_possible(&t).to_string()
1171 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1172 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1173 format!("({})", tstrs.join(", "))
1176 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1177 self.resolve_type_vars_if_possible(t).to_string()
1180 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1182 ty::TyInfer(ty::TyVar(v)) => {
1183 // Not entirely obvious: if `typ` is a type variable,
1184 // it can be resolved to an int/float variable, which
1185 // can then be recursively resolved, hence the
1186 // recursion. Note though that we prevent type
1187 // variables from unifying to other type variables
1188 // directly (though they may be embedded
1189 // structurally), and we prevent cycles in any case,
1190 // so this recursion should always be of very limited
1192 self.type_variables.borrow()
1194 .map(|t| self.shallow_resolve(t))
1198 ty::TyInfer(ty::IntVar(v)) => {
1199 self.int_unification_table
1202 .map(|v| v.to_type(self.tcx))
1206 ty::TyInfer(ty::FloatVar(v)) => {
1207 self.float_unification_table
1210 .map(|v| v.to_type(self.tcx))
1220 pub fn resolve_type_vars_if_possible<T:TypeFoldable<'tcx>>(&self, value: &T) -> T {
1222 * Where possible, replaces type/int/float variables in
1223 * `value` with their final value. Note that region variables
1224 * are unaffected. If a type variable has not been unified, it
1225 * is left as is. This is an idempotent operation that does
1226 * not affect inference state in any way and so you can do it
1230 let mut r = resolve::OpportunisticTypeResolver::new(self);
1231 value.fold_with(&mut r)
1234 /// Resolves all type variables in `t` and then, if any were left
1235 /// unresolved, substitutes an error type. This is used after the
1236 /// main checking when doing a second pass before writeback. The
1237 /// justification is that writeback will produce an error for
1238 /// these unconstrained type variables.
1239 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1240 let ty = self.resolve_type_vars_if_possible(t);
1241 if ty.references_error() || ty.is_ty_var() {
1242 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1249 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1251 * Attempts to resolve all type/region variables in
1252 * `value`. Region inference must have been run already (e.g.,
1253 * by calling `resolve_regions_and_report_errors`). If some
1254 * variable was never unified, an `Err` results.
1256 * This method is idempotent, but it not typically not invoked
1257 * except during the writeback phase.
1260 resolve::fully_resolve(self, value)
1263 // [Note-Type-error-reporting]
1264 // An invariant is that anytime the expected or actual type is TyError (the special
1265 // error type, meaning that an error occurred when typechecking this expression),
1266 // this is a derived error. The error cascaded from another error (that was already
1267 // reported), so it's not useful to display it to the user.
1268 // The following four methods -- type_error_message_str, type_error_message_str_with_expected,
1269 // type_error_message, and report_mismatched_types -- implement this logic.
1270 // They check if either the actual or expected type is TyError, and don't print the error
1271 // in this case. The typechecker should only ever report type errors involving mismatched
1272 // types using one of these four methods, and should not call span_err directly for such
1274 pub fn type_error_message_str<M>(&self,
1278 err: Option<&ty::TypeError<'tcx>>) where
1279 M: FnOnce(Option<String>, String) -> String,
1281 self.type_error_message_str_with_expected(sp, mk_msg, None, actual_ty, err)
1284 pub fn type_error_message_str_with_expected<M>(&self,
1287 expected_ty: Option<Ty<'tcx>>,
1289 err: Option<&ty::TypeError<'tcx>>) where
1290 M: FnOnce(Option<String>, String) -> String,
1292 debug!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
1294 let resolved_expected = expected_ty.map(|e_ty| self.resolve_type_vars_if_possible(&e_ty));
1296 if !resolved_expected.references_error() {
1297 let error_str = err.map_or("".to_string(), |t_err| {
1298 format!(" ({})", t_err)
1301 self.tcx.sess.span_err(sp, &format!("{}{}",
1302 mk_msg(resolved_expected.map(|t| self.ty_to_string(t)), actual_ty),
1305 if let Some(err) = err {
1306 self.tcx.note_and_explain_type_err(err, sp)
1311 pub fn type_error_message<M>(&self,
1314 actual_ty: Ty<'tcx>,
1315 err: Option<&ty::TypeError<'tcx>>) where
1316 M: FnOnce(String) -> String,
1318 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1320 // Don't report an error if actual type is TyError.
1321 if actual_ty.references_error() {
1325 self.type_error_message_str(sp,
1326 move |_e, a| { mk_msg(a) },
1327 self.ty_to_string(actual_ty), err);
1330 pub fn report_mismatched_types(&self,
1334 err: &ty::TypeError<'tcx>) {
1335 let trace = TypeTrace {
1337 values: Types(ty::ExpectedFound {
1342 self.report_and_explain_type_error(trace, err);
1345 pub fn report_conflicting_default_types(&self,
1349 let trace = TypeTrace {
1351 values: Types(ty::expected_found {
1357 self.report_and_explain_type_error(trace,
1358 &ty::type_err::terr_ty_param_default_mismatch(ty::expected_found {
1364 pub fn replace_late_bound_regions_with_fresh_var<T>(
1367 lbrct: LateBoundRegionConversionTime,
1368 value: &ty::Binder<T>)
1369 -> (T, FnvHashMap<ty::BoundRegion,ty::Region>)
1370 where T : TypeFoldable<'tcx>
1372 ty_fold::replace_late_bound_regions(
1375 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1378 /// See `verify_generic_bound` method in `region_inference`
1379 pub fn verify_generic_bound(&self,
1380 origin: SubregionOrigin<'tcx>,
1381 kind: GenericKind<'tcx>,
1383 bs: Vec<ty::Region>) {
1384 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1389 self.region_vars.verify_generic_bound(origin, kind, a, bs);
1392 pub fn can_equate<'b,T>(&'b self, a: &T, b: &T) -> UnitResult<'tcx>
1393 where T: Relate<'b,'tcx> + fmt::Debug
1395 debug!("can_equate({:?}, {:?})", a, b);
1397 // Gin up a dummy trace, since this won't be committed
1398 // anyhow. We should make this typetrace stuff more
1399 // generic so we don't have to do anything quite this
1401 let e = self.tcx.types.err;
1402 let trace = TypeTrace { origin: Misc(codemap::DUMMY_SP),
1403 values: Types(expected_found(true, e, e)) };
1404 self.equate(true, trace).relate(a, b)
1408 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1409 let ty = self.node_type(id);
1410 self.resolve_type_vars_or_error(&ty)
1413 pub fn expr_ty_adjusted(&self, expr: &ast::Expr) -> McResult<Ty<'tcx>> {
1414 let ty = self.adjust_expr_ty(expr, self.tables.borrow().adjustments.get(&expr.id));
1415 self.resolve_type_vars_or_error(&ty)
1418 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1419 let ty = self.resolve_type_vars_if_possible(&ty);
1420 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1421 // FIXME(@jroesch): should be able to use:
1422 // ty.moves_by_default(&self.parameter_environment, span)
1425 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1426 -> Option<Ty<'tcx>> {
1431 .map(|method| method.ty)
1432 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1435 pub fn node_method_id(&self, method_call: ty::MethodCall)
1436 -> Option<ast::DefId> {
1441 .map(|method| method.def_id)
1444 pub fn adjustments(&self) -> Ref<NodeMap<ty::AutoAdjustment<'tcx>>> {
1445 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1446 -> &'a NodeMap<ty::AutoAdjustment<'tcx>> {
1450 Ref::map(self.tables.borrow(), project_adjustments)
1453 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1454 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1457 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1458 self.tcx.region_maps.temporary_scope(rvalue_id)
1461 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture> {
1462 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1465 pub fn param_env<'b>(&'b self) -> &'b ty::ParameterEnvironment<'b,'tcx> {
1466 &self.parameter_environment
1469 pub fn closure_kind(&self,
1471 -> Option<ty::ClosureKind>
1473 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1476 pub fn closure_type(&self,
1478 substs: &ty::ClosureSubsts<'tcx>)
1479 -> ty::ClosureTy<'tcx>
1481 let closure_ty = self.tables
1486 .subst(self.tcx, &substs.func_substs);
1489 normalize_associated_type(&self.tcx, &closure_ty)
1496 impl<'tcx> TypeTrace<'tcx> {
1497 pub fn span(&self) -> Span {
1501 pub fn types(origin: TypeOrigin,
1502 a_is_expected: bool,
1505 -> TypeTrace<'tcx> {
1508 values: Types(expected_found(a_is_expected, a, b))
1512 pub fn dummy(tcx: &ty::ctxt<'tcx>) -> TypeTrace<'tcx> {
1514 origin: Misc(codemap::DUMMY_SP),
1515 values: Types(ty::ExpectedFound {
1516 expected: tcx.types.err,
1517 found: tcx.types.err,
1523 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1524 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1525 write!(f, "TypeTrace({:?})", self.origin)
1530 pub fn span(&self) -> Span {
1532 MethodCompatCheck(span) => span,
1533 ExprAssignable(span) => span,
1535 RelateTraitRefs(span) => span,
1536 RelateSelfType(span) => span,
1537 RelateOutputImplTypes(span) => span,
1538 MatchExpressionArm(match_span, _) => match_span,
1539 IfExpression(span) => span,
1540 IfExpressionWithNoElse(span) => span,
1541 RangeExpression(span) => span,
1542 EquatePredicate(span) => span,
1547 impl<'tcx> SubregionOrigin<'tcx> {
1548 pub fn span(&self) -> Span {
1550 Subtype(ref a) => a.span(),
1551 InfStackClosure(a) => a,
1552 InvokeClosure(a) => a,
1553 DerefPointer(a) => a,
1554 FreeVariable(a, _) => a,
1556 RelateObjectBound(a) => a,
1557 RelateParamBound(a, _) => a,
1558 RelateRegionParamBound(a) => a,
1559 RelateDefaultParamBound(a, _) => a,
1561 ReborrowUpvar(a, _) => a,
1562 ReferenceOutlivesReferent(_, a) => a,
1563 ExprTypeIsNotInScope(_, a) => a,
1564 BindingTypeIsNotValidAtDecl(a) => a,
1571 SafeDestructor(a) => a,
1576 impl RegionVariableOrigin {
1577 pub fn span(&self) -> Span {
1579 MiscVariable(a) => a,
1580 PatternRegion(a) => a,
1581 AddrOfRegion(a) => a,
1584 EarlyBoundRegion(a, _) => a,
1585 LateBoundRegion(a, _, _) => a,
1586 BoundRegionInCoherence(_) => codemap::DUMMY_SP,
1587 UpvarRegion(_, a) => a