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::free_region::FreeRegionMap;
23 use middle::mem_categorization as mc;
24 use middle::mem_categorization::McResult;
25 use middle::region::CodeExtent;
27 use middle::subst::Substs;
28 use middle::subst::Subst;
29 use middle::traits::{self, FulfillmentContext, Normalized,
30 SelectionContext, ObligationCause};
31 use middle::ty::{TyVid, IntVid, FloatVid, RegionVid, UnconstrainedNumeric};
32 use middle::ty::{self, Ty, TypeError, HasTypeFlags};
33 use middle::ty_fold::{self, TypeFolder, TypeFoldable};
34 use middle::ty_relate::{Relate, RelateResult, TypeRelation};
35 use rustc_data_structures::unify::{self, UnificationTable};
36 use std::cell::{RefCell, Ref};
41 use syntax::codemap::{Span, DUMMY_SP};
42 use util::nodemap::{FnvHashMap, NodeMap};
44 use self::combine::CombineFields;
45 use self::region_inference::{RegionVarBindings, RegionSnapshot};
46 use self::error_reporting::ErrorReporting;
47 use self::unify_key::ToType;
52 pub mod error_reporting;
57 pub mod region_inference;
61 pub mod type_variable;
64 pub type Bound<T> = Option<T>;
65 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
66 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
68 pub struct InferCtxt<'a, 'tcx: 'a> {
69 pub tcx: &'a ty::ctxt<'tcx>,
71 pub tables: &'a RefCell<ty::Tables<'tcx>>,
73 // We instantiate UnificationTable with bounds<Ty> because the
74 // types that might instantiate a general type variable have an
75 // order, represented by its upper and lower bounds.
76 type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
78 // Map from integral variable to the kind of integer it represents
79 int_unification_table: RefCell<UnificationTable<ty::IntVid>>,
81 // Map from floating variable to the kind of float it represents
82 float_unification_table: RefCell<UnificationTable<ty::FloatVid>>,
84 // For region variables.
85 region_vars: RegionVarBindings<'a, 'tcx>,
87 pub parameter_environment: ty::ParameterEnvironment<'a, 'tcx>,
89 pub fulfillment_cx: RefCell<traits::FulfillmentContext<'tcx>>,
91 // This is a temporary field used for toggling on normalization in the inference context,
92 // as we move towards the approach described here:
93 // https://internals.rust-lang.org/t/flattening-the-contexts-for-fun-and-profit/2293
94 // At a point sometime in the future normalization will be done by the typing context
98 err_count_on_creation: usize,
101 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
102 /// region that each late-bound region was replaced with.
103 pub type SkolemizationMap = FnvHashMap<ty::BoundRegion,ty::Region>;
105 /// Why did we require that the two types be related?
107 /// See `error_reporting.rs` for more details
108 #[derive(Clone, Copy, Debug)]
109 pub enum TypeOrigin {
110 // Not yet categorized in a better way
113 // Checking that method of impl is compatible with trait
114 MethodCompatCheck(Span),
116 // Checking that this expression can be assigned where it needs to be
117 // FIXME(eddyb) #11161 is the original Expr required?
118 ExprAssignable(Span),
120 // Relating trait refs when resolving vtables
121 RelateTraitRefs(Span),
123 // Relating self types when resolving vtables
124 RelateSelfType(Span),
126 // Relating trait type parameters to those found in impl etc
127 RelateOutputImplTypes(Span),
129 // Computing common supertype in the arms of a match expression
130 MatchExpressionArm(Span, Span),
132 // Computing common supertype in an if expression
135 // Computing common supertype of an if expression with no else counter-part
136 IfExpressionWithNoElse(Span),
138 // Computing common supertype in a range expression
139 RangeExpression(Span),
142 EquatePredicate(Span),
146 fn as_str(&self) -> &'static str {
148 &TypeOrigin::Misc(_) |
149 &TypeOrigin::RelateSelfType(_) |
150 &TypeOrigin::RelateOutputImplTypes(_) |
151 &TypeOrigin::ExprAssignable(_) => "mismatched types",
152 &TypeOrigin::RelateTraitRefs(_) => "mismatched traits",
153 &TypeOrigin::MethodCompatCheck(_) => "method not compatible with trait",
154 &TypeOrigin::MatchExpressionArm(_, _) => "match arms have incompatible types",
155 &TypeOrigin::IfExpression(_) => "if and else have incompatible types",
156 &TypeOrigin::IfExpressionWithNoElse(_) => "if may be missing an else clause",
157 &TypeOrigin::RangeExpression(_) => "start and end of range have incompatible types",
158 &TypeOrigin::EquatePredicate(_) => "equality predicate not satisfied",
163 impl fmt::Display for TypeOrigin {
164 fn fmt(&self, f: &mut fmt::Formatter) -> Result<(),fmt::Error> {
165 fmt::Display::fmt(self.as_str(), f)
169 /// See `error_reporting.rs` for more details
170 #[derive(Clone, Debug)]
171 pub enum ValuePairs<'tcx> {
172 Types(ty::ExpectedFound<Ty<'tcx>>),
173 TraitRefs(ty::ExpectedFound<ty::TraitRef<'tcx>>),
174 PolyTraitRefs(ty::ExpectedFound<ty::PolyTraitRef<'tcx>>),
177 /// The trace designates the path through inference that we took to
178 /// encounter an error or subtyping constraint.
180 /// See `error_reporting.rs` for more details.
182 pub struct TypeTrace<'tcx> {
184 values: ValuePairs<'tcx>,
187 /// The origin of a `r1 <= r2` constraint.
189 /// See `error_reporting.rs` for more details
190 #[derive(Clone, Debug)]
191 pub enum SubregionOrigin<'tcx> {
192 // Marker to indicate a constraint that only arises due to new
193 // provisions from RFC 1214. This will result in a warning, not an
195 RFC1214Subregion(Rc<SubregionOrigin<'tcx>>),
197 // Arose from a subtyping relation
198 Subtype(TypeTrace<'tcx>),
200 // Stack-allocated closures cannot outlive innermost loop
201 // or function so as to ensure we only require finite stack
202 InfStackClosure(Span),
204 // Invocation of closure must be within its lifetime
207 // Dereference of reference must be within its lifetime
210 // Closure bound must not outlive captured free variables
211 FreeVariable(Span, ast::NodeId),
213 // Index into slice must be within its lifetime
216 // When casting `&'a T` to an `&'b Trait` object,
217 // relating `'a` to `'b`
218 RelateObjectBound(Span),
220 // Some type parameter was instantiated with the given type,
221 // and that type must outlive some region.
222 RelateParamBound(Span, Ty<'tcx>),
224 // The given region parameter was instantiated with a region
225 // that must outlive some other region.
226 RelateRegionParamBound(Span),
228 // A bound placed on type parameters that states that must outlive
229 // the moment of their instantiation.
230 RelateDefaultParamBound(Span, Ty<'tcx>),
232 // Creating a pointer `b` to contents of another reference
235 // Creating a pointer `b` to contents of an upvar
236 ReborrowUpvar(Span, ty::UpvarId),
238 // Data with type `Ty<'tcx>` was borrowed
239 DataBorrowed(Ty<'tcx>, Span),
241 // (&'a &'b T) where a >= b
242 ReferenceOutlivesReferent(Ty<'tcx>, Span),
244 // Type or region parameters must be in scope.
245 ParameterInScope(ParameterOrigin, Span),
247 // The type T of an expression E must outlive the lifetime for E.
248 ExprTypeIsNotInScope(Ty<'tcx>, Span),
250 // A `ref b` whose region does not enclose the decl site
251 BindingTypeIsNotValidAtDecl(Span),
253 // Regions appearing in a method receiver must outlive method call
256 // Regions appearing in a function argument must outlive func call
259 // Region in return type of invoked fn must enclose call
262 // Operands must be in scope
265 // Region resulting from a `&` expr must enclose the `&` expr
268 // An auto-borrow that does not enclose the expr where it occurs
271 // Region constraint arriving from destructor safety
272 SafeDestructor(Span),
275 /// Places that type/region parameters can appear.
276 #[derive(Clone, Copy, Debug)]
277 pub enum ParameterOrigin {
279 MethodCall, // foo.bar() <-- parameters on impl providing bar()
280 OverloadedOperator, // a + b when overloaded
281 OverloadedDeref, // *a when overloaded
284 /// Times when we replace late-bound regions with variables:
285 #[derive(Clone, Copy, Debug)]
286 pub enum LateBoundRegionConversionTime {
287 /// when a fn is called
290 /// when two higher-ranked types are compared
293 /// when projecting an associated type
294 AssocTypeProjection(ast::Name),
297 /// Reasons to create a region inference variable
299 /// See `error_reporting.rs` for more details
300 #[derive(Clone, Debug)]
301 pub enum RegionVariableOrigin {
302 // Region variables created for ill-categorized reasons,
303 // mostly indicates places in need of refactoring
306 // Regions created by a `&P` or `[...]` pattern
309 // Regions created by `&` operator
312 // Regions created as part of an autoref of a method receiver
315 // Regions created as part of an automatic coercion
318 // Region variables created as the values for early-bound regions
319 EarlyBoundRegion(Span, ast::Name),
321 // Region variables created for bound regions
322 // in a function or method that is called
323 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
325 UpvarRegion(ty::UpvarId, Span),
327 BoundRegionInCoherence(ast::Name),
330 #[derive(Copy, Clone, Debug)]
331 pub enum FixupError {
332 UnresolvedIntTy(IntVid),
333 UnresolvedFloatTy(FloatVid),
337 pub fn fixup_err_to_string(f: FixupError) -> String {
338 use self::FixupError::*;
341 UnresolvedIntTy(_) => {
342 "cannot determine the type of this integer; add a suffix to \
343 specify the type explicitly".to_string()
345 UnresolvedFloatTy(_) => {
346 "cannot determine the type of this number; add a suffix to specify \
347 the type explicitly".to_string()
349 UnresolvedTy(_) => "unconstrained type".to_string(),
353 /// errors_will_be_reported is required to proxy to the fulfillment context
354 /// FIXME -- a better option would be to hold back on modifying
355 /// the global cache until we know that all dependent obligations
356 /// are also satisfied. In that case, we could actually remove
357 /// this boolean flag, and we'd also avoid the problem of squelching
358 /// duplicate errors that occur across fns.
359 pub fn new_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
360 tables: &'a RefCell<ty::Tables<'tcx>>,
361 param_env: Option<ty::ParameterEnvironment<'a, 'tcx>>,
362 errors_will_be_reported: bool)
363 -> InferCtxt<'a, 'tcx> {
367 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
368 int_unification_table: RefCell::new(UnificationTable::new()),
369 float_unification_table: RefCell::new(UnificationTable::new()),
370 region_vars: RegionVarBindings::new(tcx),
371 parameter_environment: param_env.unwrap_or(tcx.empty_parameter_environment()),
372 fulfillment_cx: RefCell::new(traits::FulfillmentContext::new(errors_will_be_reported)),
374 err_count_on_creation: tcx.sess.err_count()
378 pub fn normalizing_infer_ctxt<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
379 tables: &'a RefCell<ty::Tables<'tcx>>)
380 -> InferCtxt<'a, 'tcx> {
381 let mut infcx = new_infer_ctxt(tcx, tables, None, false);
382 infcx.normalize = true;
386 /// Computes the least upper-bound of `a` and `b`. If this is not possible, reports an error and
388 pub fn common_supertype<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
395 debug!("common_supertype({:?}, {:?})",
398 let trace = TypeTrace {
400 values: Types(expected_found(a_is_expected, a, b))
403 let result = cx.commit_if_ok(|_| cx.lub(a_is_expected, trace.clone()).relate(&a, &b));
407 cx.report_and_explain_type_error(trace, err);
413 pub fn mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
420 debug!("mk_subty({:?} <: {:?})", a, b);
421 cx.sub_types(a_is_expected, origin, a, b)
424 pub fn can_mk_subty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
427 -> UnitResult<'tcx> {
428 debug!("can_mk_subty({:?} <: {:?})", a, b);
430 let trace = TypeTrace {
431 origin: Misc(codemap::DUMMY_SP),
432 values: Types(expected_found(true, a, b))
434 cx.sub(true, trace).relate(&a, &b).map(|_| ())
438 pub fn can_mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>, a: Ty<'tcx>, b: Ty<'tcx>)
441 cx.can_equate(&a, &b)
444 pub fn mk_subr<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
445 origin: SubregionOrigin<'tcx>,
448 debug!("mk_subr({:?} <: {:?})", a, b);
449 let snapshot = cx.region_vars.start_snapshot();
450 cx.region_vars.make_subregion(origin, a, b);
451 cx.region_vars.commit(snapshot);
454 pub fn mk_eqty<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
461 debug!("mk_eqty({:?} <: {:?})", a, b);
462 cx.commit_if_ok(|_| cx.eq_types(a_is_expected, origin, a, b))
465 pub fn mk_sub_poly_trait_refs<'a, 'tcx>(cx: &InferCtxt<'a, 'tcx>,
468 a: ty::PolyTraitRef<'tcx>,
469 b: ty::PolyTraitRef<'tcx>)
472 debug!("mk_sub_trait_refs({:?} <: {:?})",
474 cx.commit_if_ok(|_| cx.sub_poly_trait_refs(a_is_expected, origin, a.clone(), b.clone()))
477 fn expected_found<T>(a_is_expected: bool,
480 -> ty::ExpectedFound<T>
483 ty::ExpectedFound {expected: a, found: b}
485 ty::ExpectedFound {expected: b, found: a}
489 #[must_use = "once you start a snapshot, you should always consume it"]
490 pub struct CombinedSnapshot {
491 type_snapshot: type_variable::Snapshot,
492 int_snapshot: unify::Snapshot<ty::IntVid>,
493 float_snapshot: unify::Snapshot<ty::FloatVid>,
494 region_vars_snapshot: RegionSnapshot,
497 pub fn normalize_associated_type<'tcx,T>(tcx: &ty::ctxt<'tcx>, value: &T) -> T
498 where T : TypeFoldable<'tcx> + HasTypeFlags
500 debug!("normalize_associated_type(t={:?})", value);
502 let value = erase_regions(tcx, value);
504 if !value.has_projection_types() {
508 let infcx = new_infer_ctxt(tcx, &tcx.tables, None, true);
509 let mut selcx = traits::SelectionContext::new(&infcx);
510 let cause = traits::ObligationCause::dummy();
511 let traits::Normalized { value: result, obligations } =
512 traits::normalize(&mut selcx, cause, &value);
514 debug!("normalize_associated_type: result={:?} obligations={:?}",
518 let mut fulfill_cx = infcx.fulfillment_cx.borrow_mut();
520 for obligation in obligations {
521 fulfill_cx.register_predicate_obligation(&infcx, obligation);
524 let result = drain_fulfillment_cx_or_panic(DUMMY_SP, &infcx, &mut fulfill_cx, &result);
529 pub fn drain_fulfillment_cx_or_panic<'a,'tcx,T>(span: Span,
530 infcx: &InferCtxt<'a,'tcx>,
531 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
534 where T : TypeFoldable<'tcx>
536 match drain_fulfillment_cx(infcx, fulfill_cx, result) {
539 infcx.tcx.sess.span_bug(
541 &format!("Encountered errors `{:?}` fulfilling during trans",
547 /// Finishes processes any obligations that remain in the fulfillment
548 /// context, and then "freshens" and returns `result`. This is
549 /// primarily used during normalization and other cases where
550 /// processing the obligations in `fulfill_cx` may cause type
551 /// inference variables that appear in `result` to be unified, and
552 /// hence we need to process those obligations to get the complete
553 /// picture of the type.
554 pub fn drain_fulfillment_cx<'a,'tcx,T>(infcx: &InferCtxt<'a,'tcx>,
555 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
557 -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
558 where T : TypeFoldable<'tcx>
560 debug!("drain_fulfillment_cx(result={:?})",
563 // In principle, we only need to do this so long as `result`
564 // contains unbound type parameters. It could be a slight
565 // optimization to stop iterating early.
566 match fulfill_cx.select_all_or_error(infcx) {
573 // Use freshen to simultaneously replace all type variables with
574 // their bindings and replace all regions with 'static. This is
575 // sort of overkill because we do not expect there to be any
576 // unbound type variables, hence no `TyFresh` types should ever be
578 Ok(result.fold_with(&mut infcx.freshener()))
581 /// Returns an equivalent value with all free regions removed (note
582 /// that late-bound regions remain, because they are important for
583 /// subtyping, but they are anonymized and normalized as well). This
584 /// is a stronger, caching version of `ty_fold::erase_regions`.
585 pub fn erase_regions<'tcx,T>(cx: &ty::ctxt<'tcx>, value: &T) -> T
586 where T : TypeFoldable<'tcx>
588 let value1 = value.fold_with(&mut RegionEraser(cx));
589 debug!("erase_regions({:?}) = {:?}",
593 struct RegionEraser<'a, 'tcx: 'a>(&'a ty::ctxt<'tcx>);
595 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
596 fn tcx(&self) -> &ty::ctxt<'tcx> { self.0 }
598 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
599 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
604 let t_norm = ty_fold::super_fold_ty(self, ty);
605 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
609 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
610 where T : TypeFoldable<'tcx>
612 let u = self.tcx().anonymize_late_bound_regions(t);
613 ty_fold::super_fold_binder(self, &u)
616 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
617 // because late-bound regions affect subtyping, we can't
618 // erase the bound/free distinction, but we can replace
619 // all free regions with 'static.
621 // Note that we *CAN* replace early-bound regions -- the
622 // type system never "sees" those, they get substituted
623 // away. In trans, they will always be erased to 'static
624 // whenever a substitution occurs.
626 ty::ReLateBound(..) => r,
631 fn fold_substs(&mut self,
632 substs: &subst::Substs<'tcx>)
633 -> subst::Substs<'tcx> {
634 subst::Substs { regions: subst::ErasedRegions,
635 types: substs.types.fold_with(self) }
640 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
641 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
642 t.fold_with(&mut self.freshener())
645 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
647 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
652 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
653 freshen::TypeFreshener::new(self)
656 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
657 use middle::ty::UnconstrainedNumeric::{Neither, UnconstrainedInt, UnconstrainedFloat};
659 ty::TyInfer(ty::IntVar(vid)) => {
660 if self.int_unification_table.borrow_mut().has_value(vid) {
666 ty::TyInfer(ty::FloatVar(vid)) => {
667 if self.float_unification_table.borrow_mut().has_value(vid) {
677 /// Returns a type variable's default fallback if any exists. A default
678 /// must be attached to the variable when created, if it is created
679 /// without a default, this will return None.
681 /// This code does not apply to integral or floating point variables,
682 /// only to use declared defaults.
684 /// See `new_ty_var_with_default` to create a type variable with a default.
685 /// See `type_variable::Default` for details about what a default entails.
686 pub fn default(&self, ty: Ty<'tcx>) -> Option<type_variable::Default<'tcx>> {
688 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().default(vid),
693 pub fn unsolved_variables(&self) -> Vec<ty::Ty<'tcx>> {
694 let mut variables = Vec::new();
696 let unbound_ty_vars = self.type_variables
698 .unsolved_variables()
700 .map(|t| self.tcx.mk_var(t));
702 let unbound_int_vars = self.int_unification_table
704 .unsolved_variables()
706 .map(|v| self.tcx.mk_int_var(v));
708 let unbound_float_vars = self.float_unification_table
710 .unsolved_variables()
712 .map(|v| self.tcx.mk_float_var(v));
714 variables.extend(unbound_ty_vars);
715 variables.extend(unbound_int_vars);
716 variables.extend(unbound_float_vars);
721 fn combine_fields(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
722 -> CombineFields<'a, 'tcx> {
723 CombineFields {infcx: self,
724 a_is_expected: a_is_expected,
729 // public so that it can be used from the rustc_driver unit tests
730 pub fn equate(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
731 -> equate::Equate<'a, 'tcx>
733 self.combine_fields(a_is_expected, trace).equate()
736 // public so that it can be used from the rustc_driver unit tests
737 pub fn sub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
738 -> sub::Sub<'a, 'tcx>
740 self.combine_fields(a_is_expected, trace).sub()
743 // public so that it can be used from the rustc_driver unit tests
744 pub fn lub(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
745 -> lub::Lub<'a, 'tcx>
747 self.combine_fields(a_is_expected, trace).lub()
750 // public so that it can be used from the rustc_driver unit tests
751 pub fn glb(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>)
752 -> glb::Glb<'a, 'tcx>
754 self.combine_fields(a_is_expected, trace).glb()
757 fn start_snapshot(&self) -> CombinedSnapshot {
759 type_snapshot: self.type_variables.borrow_mut().snapshot(),
760 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
761 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
762 region_vars_snapshot: self.region_vars.start_snapshot(),
766 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot) {
767 debug!("rollback_to(cause={})", cause);
768 let CombinedSnapshot { type_snapshot,
771 region_vars_snapshot } = snapshot;
775 .rollback_to(type_snapshot);
776 self.int_unification_table
778 .rollback_to(int_snapshot);
779 self.float_unification_table
781 .rollback_to(float_snapshot);
783 .rollback_to(region_vars_snapshot);
786 fn commit_from(&self, snapshot: CombinedSnapshot) {
787 debug!("commit_from!");
788 let CombinedSnapshot { type_snapshot,
791 region_vars_snapshot } = snapshot;
795 .commit(type_snapshot);
796 self.int_unification_table
798 .commit(int_snapshot);
799 self.float_unification_table
801 .commit(float_snapshot);
803 .commit(region_vars_snapshot);
806 /// Execute `f` and commit the bindings
807 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
811 let snapshot = self.start_snapshot();
813 self.commit_from(snapshot);
817 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
818 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
819 F: FnOnce(&CombinedSnapshot) -> Result<T, E>
821 debug!("commit_if_ok()");
822 let snapshot = self.start_snapshot();
823 let r = f(&snapshot);
824 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
826 Ok(_) => { self.commit_from(snapshot); }
827 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
832 /// Execute `f` and commit only the region bindings if successful.
833 /// The function f must be very careful not to leak any non-region
834 /// variables that get created.
835 pub fn commit_regions_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
836 F: FnOnce() -> Result<T, E>
838 debug!("commit_regions_if_ok()");
839 let CombinedSnapshot { type_snapshot,
842 region_vars_snapshot } = self.start_snapshot();
844 let r = self.commit_if_ok(|_| f());
846 debug!("commit_regions_if_ok: rolling back everything but regions");
848 // Roll back any non-region bindings - they should be resolved
849 // inside `f`, with, e.g. `resolve_type_vars_if_possible`.
852 .rollback_to(type_snapshot);
853 self.int_unification_table
855 .rollback_to(int_snapshot);
856 self.float_unification_table
858 .rollback_to(float_snapshot);
860 // Commit region vars that may escape through resolved types.
862 .commit(region_vars_snapshot);
867 /// Execute `f` then unroll any bindings it creates
868 pub fn probe<R, F>(&self, f: F) -> R where
869 F: FnOnce(&CombinedSnapshot) -> R,
872 let snapshot = self.start_snapshot();
873 let r = f(&snapshot);
874 self.rollback_to("probe", snapshot);
878 pub fn add_given(&self,
882 self.region_vars.add_given(sub, sup);
885 pub fn sub_types(&self,
892 debug!("sub_types({:?} <: {:?})", a, b);
893 self.commit_if_ok(|_| {
894 let trace = TypeTrace::types(origin, a_is_expected, a, b);
895 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
899 pub fn eq_types(&self,
906 self.commit_if_ok(|_| {
907 let trace = TypeTrace::types(origin, a_is_expected, a, b);
908 self.equate(a_is_expected, trace).relate(&a, &b).map(|_| ())
912 pub fn sub_trait_refs(&self,
915 a: ty::TraitRef<'tcx>,
916 b: ty::TraitRef<'tcx>)
919 debug!("sub_trait_refs({:?} <: {:?})",
922 self.commit_if_ok(|_| {
923 let trace = TypeTrace {
925 values: TraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
927 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
931 pub fn sub_poly_trait_refs(&self,
934 a: ty::PolyTraitRef<'tcx>,
935 b: ty::PolyTraitRef<'tcx>)
938 debug!("sub_poly_trait_refs({:?} <: {:?})",
941 self.commit_if_ok(|_| {
942 let trace = TypeTrace {
944 values: PolyTraitRefs(expected_found(a_is_expected, a.clone(), b.clone()))
946 self.sub(a_is_expected, trace).relate(&a, &b).map(|_| ())
950 pub fn construct_skolemized_subst(&self,
951 generics: &ty::Generics<'tcx>,
952 snapshot: &CombinedSnapshot)
953 -> (subst::Substs<'tcx>, SkolemizationMap) {
954 /*! See `higher_ranked::construct_skolemized_subst` */
956 higher_ranked::construct_skolemized_substs(self, generics, snapshot)
959 pub fn skolemize_late_bound_regions<T>(&self,
960 value: &ty::Binder<T>,
961 snapshot: &CombinedSnapshot)
962 -> (T, SkolemizationMap)
963 where T : TypeFoldable<'tcx>
965 /*! See `higher_ranked::skolemize_late_bound_regions` */
967 higher_ranked::skolemize_late_bound_regions(self, value, snapshot)
970 pub fn leak_check(&self,
971 skol_map: &SkolemizationMap,
972 snapshot: &CombinedSnapshot)
975 /*! See `higher_ranked::leak_check` */
977 match higher_ranked::leak_check(self, skol_map, snapshot) {
979 Err((br, r)) => Err(TypeError::RegionsInsufficientlyPolymorphic(br, r))
983 pub fn plug_leaks<T>(&self,
984 skol_map: SkolemizationMap,
985 snapshot: &CombinedSnapshot,
988 where T : TypeFoldable<'tcx>
990 /*! See `higher_ranked::plug_leaks` */
992 higher_ranked::plug_leaks(self, skol_map, snapshot, value)
995 pub fn equality_predicate(&self,
997 predicate: &ty::PolyEquatePredicate<'tcx>)
998 -> UnitResult<'tcx> {
999 self.commit_if_ok(|snapshot| {
1000 let (ty::EquatePredicate(a, b), skol_map) =
1001 self.skolemize_late_bound_regions(predicate, snapshot);
1002 let origin = EquatePredicate(span);
1003 let () = try!(mk_eqty(self, false, origin, a, b));
1004 self.leak_check(&skol_map, snapshot)
1008 pub fn region_outlives_predicate(&self,
1010 predicate: &ty::PolyRegionOutlivesPredicate)
1011 -> UnitResult<'tcx> {
1012 self.commit_if_ok(|snapshot| {
1013 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
1014 self.skolemize_late_bound_regions(predicate, snapshot);
1015 let origin = RelateRegionParamBound(span);
1016 let () = mk_subr(self, origin, r_b, r_a); // `b : a` ==> `a <= b`
1017 self.leak_check(&skol_map, snapshot)
1021 pub fn next_ty_var_id(&self, diverging: bool) -> TyVid {
1024 .new_var(diverging, None)
1027 pub fn next_ty_var(&self) -> Ty<'tcx> {
1028 self.tcx.mk_var(self.next_ty_var_id(false))
1031 pub fn next_ty_var_with_default(&self,
1032 default: Option<type_variable::Default<'tcx>>) -> Ty<'tcx> {
1033 let ty_var_id = self.type_variables
1035 .new_var(false, default);
1037 self.tcx.mk_var(ty_var_id)
1040 pub fn next_diverging_ty_var(&self) -> Ty<'tcx> {
1041 self.tcx.mk_var(self.next_ty_var_id(true))
1044 pub fn next_ty_vars(&self, n: usize) -> Vec<Ty<'tcx>> {
1045 (0..n).map(|_i| self.next_ty_var()).collect()
1048 pub fn next_int_var_id(&self) -> IntVid {
1049 self.int_unification_table
1054 pub fn next_float_var_id(&self) -> FloatVid {
1055 self.float_unification_table
1060 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region {
1061 ty::ReInfer(ty::ReVar(self.region_vars.new_region_var(origin)))
1064 pub fn region_vars_for_defs(&self,
1066 defs: &[ty::RegionParameterDef])
1067 -> Vec<ty::Region> {
1069 .map(|d| self.next_region_var(EarlyBoundRegion(span, d.name)))
1073 // We have to take `&mut Substs` in order to provide the correct substitutions for defaults
1074 // along the way, for this reason we don't return them.
1075 pub fn type_vars_for_defs(&self,
1077 space: subst::ParamSpace,
1078 substs: &mut Substs<'tcx>,
1079 defs: &[ty::TypeParameterDef<'tcx>]) {
1081 let mut vars = Vec::with_capacity(defs.len());
1083 for def in defs.iter() {
1084 let default = def.default.map(|default| {
1085 type_variable::Default {
1086 ty: default.subst_spanned(self.tcx, substs, Some(span)),
1088 def_id: def.default_def_id
1092 let ty_var = self.next_ty_var_with_default(default);
1093 substs.types.push(space, ty_var);
1098 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1099 /// type/region parameter to a fresh inference variable.
1100 pub fn fresh_substs_for_generics(&self,
1102 generics: &ty::Generics<'tcx>)
1103 -> subst::Substs<'tcx>
1105 let type_params = subst::VecPerParamSpace::empty();
1108 generics.regions.map(
1109 |d| self.next_region_var(EarlyBoundRegion(span, d.name)));
1111 let mut substs = subst::Substs::new(type_params, region_params);
1113 for space in subst::ParamSpace::all().iter() {
1114 self.type_vars_for_defs(
1118 generics.types.get_slice(*space));
1124 /// Given a set of generics defined on a trait, returns a substitution mapping each output
1125 /// type/region parameter to a fresh inference variable, and mapping the self type to
1127 pub fn fresh_substs_for_trait(&self,
1129 generics: &ty::Generics<'tcx>,
1131 -> subst::Substs<'tcx>
1134 assert!(generics.types.len(subst::SelfSpace) == 1);
1135 assert!(generics.types.len(subst::FnSpace) == 0);
1136 assert!(generics.regions.len(subst::SelfSpace) == 0);
1137 assert!(generics.regions.len(subst::FnSpace) == 0);
1139 let type_params = Vec::new();
1141 let region_param_defs = generics.regions.get_slice(subst::TypeSpace);
1142 let regions = self.region_vars_for_defs(span, region_param_defs);
1144 let mut substs = subst::Substs::new_trait(type_params, regions, self_ty);
1146 let type_parameter_defs = generics.types.get_slice(subst::TypeSpace);
1147 self.type_vars_for_defs(span, subst::TypeSpace, &mut substs, type_parameter_defs);
1152 pub fn fresh_bound_region(&self, debruijn: ty::DebruijnIndex) -> ty::Region {
1153 self.region_vars.new_bound(debruijn)
1156 /// Apply `adjustment` to the type of `expr`
1157 pub fn adjust_expr_ty(&self,
1159 adjustment: Option<&ty::AutoAdjustment<'tcx>>)
1162 let raw_ty = self.expr_ty(expr);
1163 let raw_ty = self.shallow_resolve(raw_ty);
1164 let resolve_ty = |ty: Ty<'tcx>| self.resolve_type_vars_if_possible(&ty);
1165 raw_ty.adjust(self.tcx,
1169 |method_call| self.tables
1173 .map(|method| resolve_ty(method.ty)))
1176 pub fn node_type(&self, id: ast::NodeId) -> Ty<'tcx> {
1177 match self.tables.borrow().node_types.get(&id) {
1180 None if self.tcx.sess.err_count() - self.err_count_on_creation != 0 =>
1184 &format!("no type for node {}: {} in fcx",
1185 id, self.tcx.map.node_to_string(id)));
1190 pub fn expr_ty(&self, ex: &ast::Expr) -> Ty<'tcx> {
1191 match self.tables.borrow().node_types.get(&ex.id) {
1194 self.tcx.sess.bug(&format!("no type for expr in fcx"));
1199 pub fn resolve_regions_and_report_errors(&self,
1200 free_regions: &FreeRegionMap,
1201 subject_node_id: ast::NodeId) {
1202 let errors = self.region_vars.resolve_regions(free_regions, subject_node_id);
1203 self.report_region_errors(&errors); // see error_reporting.rs
1206 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1207 self.resolve_type_vars_if_possible(&t).to_string()
1210 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1211 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1212 format!("({})", tstrs.join(", "))
1215 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1216 self.resolve_type_vars_if_possible(t).to_string()
1219 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1221 ty::TyInfer(ty::TyVar(v)) => {
1222 // Not entirely obvious: if `typ` is a type variable,
1223 // it can be resolved to an int/float variable, which
1224 // can then be recursively resolved, hence the
1225 // recursion. Note though that we prevent type
1226 // variables from unifying to other type variables
1227 // directly (though they may be embedded
1228 // structurally), and we prevent cycles in any case,
1229 // so this recursion should always be of very limited
1231 self.type_variables.borrow()
1233 .map(|t| self.shallow_resolve(t))
1237 ty::TyInfer(ty::IntVar(v)) => {
1238 self.int_unification_table
1241 .map(|v| v.to_type(self.tcx))
1245 ty::TyInfer(ty::FloatVar(v)) => {
1246 self.float_unification_table
1249 .map(|v| v.to_type(self.tcx))
1259 pub fn resolve_type_vars_if_possible<T:TypeFoldable<'tcx>>(&self, value: &T) -> T {
1261 * Where possible, replaces type/int/float variables in
1262 * `value` with their final value. Note that region variables
1263 * are unaffected. If a type variable has not been unified, it
1264 * is left as is. This is an idempotent operation that does
1265 * not affect inference state in any way and so you can do it
1269 let mut r = resolve::OpportunisticTypeResolver::new(self);
1270 value.fold_with(&mut r)
1273 /// Resolves all type variables in `t` and then, if any were left
1274 /// unresolved, substitutes an error type. This is used after the
1275 /// main checking when doing a second pass before writeback. The
1276 /// justification is that writeback will produce an error for
1277 /// these unconstrained type variables.
1278 fn resolve_type_vars_or_error(&self, t: &Ty<'tcx>) -> mc::McResult<Ty<'tcx>> {
1279 let ty = self.resolve_type_vars_if_possible(t);
1280 if ty.references_error() || ty.is_ty_var() {
1281 debug!("resolve_type_vars_or_error: error from {:?}", ty);
1288 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1290 * Attempts to resolve all type/region variables in
1291 * `value`. Region inference must have been run already (e.g.,
1292 * by calling `resolve_regions_and_report_errors`). If some
1293 * variable was never unified, an `Err` results.
1295 * This method is idempotent, but it not typically not invoked
1296 * except during the writeback phase.
1299 resolve::fully_resolve(self, value)
1302 // [Note-Type-error-reporting]
1303 // An invariant is that anytime the expected or actual type is TyError (the special
1304 // error type, meaning that an error occurred when typechecking this expression),
1305 // this is a derived error. The error cascaded from another error (that was already
1306 // reported), so it's not useful to display it to the user.
1307 // The following four methods -- type_error_message_str, type_error_message_str_with_expected,
1308 // type_error_message, and report_mismatched_types -- implement this logic.
1309 // They check if either the actual or expected type is TyError, and don't print the error
1310 // in this case. The typechecker should only ever report type errors involving mismatched
1311 // types using one of these four methods, and should not call span_err directly for such
1313 pub fn type_error_message_str<M>(&self,
1317 err: Option<&ty::TypeError<'tcx>>) where
1318 M: FnOnce(Option<String>, String) -> String,
1320 self.type_error_message_str_with_expected(sp, mk_msg, None, actual_ty, err)
1323 pub fn type_error_message_str_with_expected<M>(&self,
1326 expected_ty: Option<Ty<'tcx>>,
1328 err: Option<&ty::TypeError<'tcx>>) where
1329 M: FnOnce(Option<String>, String) -> String,
1331 debug!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
1333 let resolved_expected = expected_ty.map(|e_ty| self.resolve_type_vars_if_possible(&e_ty));
1335 if !resolved_expected.references_error() {
1336 let error_str = err.map_or("".to_string(), |t_err| {
1337 format!(" ({})", t_err)
1340 self.tcx.sess.span_err(sp, &format!("{}{}",
1341 mk_msg(resolved_expected.map(|t| self.ty_to_string(t)), actual_ty),
1344 if let Some(err) = err {
1345 self.tcx.note_and_explain_type_err(err, sp)
1350 pub fn type_error_message<M>(&self,
1353 actual_ty: Ty<'tcx>,
1354 err: Option<&ty::TypeError<'tcx>>) where
1355 M: FnOnce(String) -> String,
1357 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1359 // Don't report an error if actual type is TyError.
1360 if actual_ty.references_error() {
1364 self.type_error_message_str(sp,
1365 move |_e, a| { mk_msg(a) },
1366 self.ty_to_string(actual_ty), err);
1369 pub fn report_mismatched_types(&self,
1373 err: &ty::TypeError<'tcx>) {
1374 let trace = TypeTrace {
1376 values: Types(ty::ExpectedFound {
1381 self.report_and_explain_type_error(trace, err);
1384 pub fn report_conflicting_default_types(&self,
1386 expected: type_variable::Default<'tcx>,
1387 actual: type_variable::Default<'tcx>) {
1388 let trace = TypeTrace {
1390 values: Types(ty::ExpectedFound {
1391 expected: expected.ty,
1396 self.report_and_explain_type_error(trace,
1397 &TypeError::TyParamDefaultMismatch(ty::ExpectedFound {
1403 pub fn replace_late_bound_regions_with_fresh_var<T>(
1406 lbrct: LateBoundRegionConversionTime,
1407 value: &ty::Binder<T>)
1408 -> (T, FnvHashMap<ty::BoundRegion,ty::Region>)
1409 where T : TypeFoldable<'tcx>
1411 ty_fold::replace_late_bound_regions(
1414 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1417 /// See `verify_generic_bound` method in `region_inference`
1418 pub fn verify_generic_bound(&self,
1419 origin: SubregionOrigin<'tcx>,
1420 kind: GenericKind<'tcx>,
1422 bound: VerifyBound) {
1423 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1428 self.region_vars.verify_generic_bound(origin, kind, a, bound);
1431 pub fn can_equate<'b,T>(&'b self, a: &T, b: &T) -> UnitResult<'tcx>
1432 where T: Relate<'b,'tcx> + fmt::Debug
1434 debug!("can_equate({:?}, {:?})", a, b);
1436 // Gin up a dummy trace, since this won't be committed
1437 // anyhow. We should make this typetrace stuff more
1438 // generic so we don't have to do anything quite this
1440 let e = self.tcx.types.err;
1441 let trace = TypeTrace { origin: Misc(codemap::DUMMY_SP),
1442 values: Types(expected_found(true, e, e)) };
1443 self.equate(true, trace).relate(a, b)
1447 pub fn node_ty(&self, id: ast::NodeId) -> McResult<Ty<'tcx>> {
1448 let ty = self.node_type(id);
1449 self.resolve_type_vars_or_error(&ty)
1452 pub fn expr_ty_adjusted(&self, expr: &ast::Expr) -> McResult<Ty<'tcx>> {
1453 let ty = self.adjust_expr_ty(expr, self.tables.borrow().adjustments.get(&expr.id));
1454 self.resolve_type_vars_or_error(&ty)
1457 pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
1458 let ty = self.resolve_type_vars_if_possible(&ty);
1459 !traits::type_known_to_meet_builtin_bound(self, ty, ty::BoundCopy, span)
1460 // FIXME(@jroesch): should be able to use:
1461 // ty.moves_by_default(&self.parameter_environment, span)
1464 pub fn node_method_ty(&self, method_call: ty::MethodCall)
1465 -> Option<Ty<'tcx>> {
1470 .map(|method| method.ty)
1471 .map(|ty| self.resolve_type_vars_if_possible(&ty))
1474 pub fn node_method_id(&self, method_call: ty::MethodCall)
1475 -> Option<ast::DefId> {
1480 .map(|method| method.def_id)
1483 pub fn adjustments(&self) -> Ref<NodeMap<ty::AutoAdjustment<'tcx>>> {
1484 fn project_adjustments<'a, 'tcx>(tables: &'a ty::Tables<'tcx>)
1485 -> &'a NodeMap<ty::AutoAdjustment<'tcx>> {
1489 Ref::map(self.tables.borrow(), project_adjustments)
1492 pub fn is_method_call(&self, id: ast::NodeId) -> bool {
1493 self.tables.borrow().method_map.contains_key(&ty::MethodCall::expr(id))
1496 pub fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<CodeExtent> {
1497 self.tcx.region_maps.temporary_scope(rvalue_id)
1500 pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture> {
1501 self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
1504 pub fn param_env<'b>(&'b self) -> &'b ty::ParameterEnvironment<'b,'tcx> {
1505 &self.parameter_environment
1508 pub fn closure_kind(&self,
1510 -> Option<ty::ClosureKind>
1512 self.tables.borrow().closure_kinds.get(&def_id).cloned()
1515 pub fn closure_type(&self,
1517 substs: &ty::ClosureSubsts<'tcx>)
1518 -> ty::ClosureTy<'tcx>
1520 let closure_ty = self.tables
1525 .subst(self.tcx, &substs.func_substs);
1528 normalize_associated_type(&self.tcx, &closure_ty)
1535 impl<'tcx> TypeTrace<'tcx> {
1536 pub fn span(&self) -> Span {
1540 pub fn types(origin: TypeOrigin,
1541 a_is_expected: bool,
1544 -> TypeTrace<'tcx> {
1547 values: Types(expected_found(a_is_expected, a, b))
1551 pub fn dummy(tcx: &ty::ctxt<'tcx>) -> TypeTrace<'tcx> {
1553 origin: Misc(codemap::DUMMY_SP),
1554 values: Types(ty::ExpectedFound {
1555 expected: tcx.types.err,
1556 found: tcx.types.err,
1562 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1563 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1564 write!(f, "TypeTrace({:?})", self.origin)
1569 pub fn span(&self) -> Span {
1571 MethodCompatCheck(span) => span,
1572 ExprAssignable(span) => span,
1574 RelateTraitRefs(span) => span,
1575 RelateSelfType(span) => span,
1576 RelateOutputImplTypes(span) => span,
1577 MatchExpressionArm(match_span, _) => match_span,
1578 IfExpression(span) => span,
1579 IfExpressionWithNoElse(span) => span,
1580 RangeExpression(span) => span,
1581 EquatePredicate(span) => span,
1586 impl<'tcx> SubregionOrigin<'tcx> {
1587 pub fn span(&self) -> Span {
1589 RFC1214Subregion(ref a) => a.span(),
1590 Subtype(ref a) => a.span(),
1591 InfStackClosure(a) => a,
1592 InvokeClosure(a) => a,
1593 DerefPointer(a) => a,
1594 FreeVariable(a, _) => a,
1596 RelateObjectBound(a) => a,
1597 RelateParamBound(a, _) => a,
1598 RelateRegionParamBound(a) => a,
1599 RelateDefaultParamBound(a, _) => a,
1601 ReborrowUpvar(a, _) => a,
1602 DataBorrowed(_, a) => a,
1603 ReferenceOutlivesReferent(_, a) => a,
1604 ParameterInScope(_, a) => a,
1605 ExprTypeIsNotInScope(_, a) => a,
1606 BindingTypeIsNotValidAtDecl(a) => a,
1613 SafeDestructor(a) => a,
1618 impl RegionVariableOrigin {
1619 pub fn span(&self) -> Span {
1621 MiscVariable(a) => a,
1622 PatternRegion(a) => a,
1623 AddrOfRegion(a) => a,
1626 EarlyBoundRegion(a, _) => a,
1627 LateBoundRegion(a, _, _) => a,
1628 BoundRegionInCoherence(_) => codemap::DUMMY_SP,
1629 UpvarRegion(_, a) => a