HACK: Handle escaping bound vars from the canonical query
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@ -7,8 +7,8 @@ use crate::ty::subst::{GenericArg, InternalSubsts, SubstsRef};
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use crate::ty::visit::ValidateBoundVars;
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use crate::ty::InferTy::*;
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use crate::ty::{
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self, AdtDef, DefIdTree, Discr, Term, Ty, TyCtxt, TypeFlags, TypeSuperVisitable, TypeVisitable,
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TypeVisitor,
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self, AdtDef, DefIdTree, Discr, FallibleTypeFolder, Term, Ty, TyCtxt, TypeFlags, TypeFoldable,
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TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitor,
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};
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use crate::ty::{List, ParamEnv};
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use hir::def::DefKind;
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@ -1106,6 +1106,17 @@ impl<'tcx, T> Binder<'tcx, T> {
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if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
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}
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pub fn no_bound_vars_ignoring_escaping(self, tcx: TyCtxt<'tcx>) -> Option<T>
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where
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T: TypeFoldable<'tcx>,
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{
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if !self.0.has_escaping_bound_vars() {
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Some(self.skip_binder())
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} else {
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self.0.try_fold_with(&mut SkipBindersAt { index: ty::INNERMOST, tcx }).ok()
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}
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}
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/// Splits the contents into two things that share the same binder
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/// level as the original, returning two distinct binders.
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///
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@ -1135,6 +1146,81 @@ impl<'tcx, T: IntoIterator> Binder<'tcx, T> {
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}
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}
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struct SkipBindersAt<'tcx> {
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tcx: TyCtxt<'tcx>,
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index: ty::DebruijnIndex,
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}
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impl<'tcx> FallibleTypeFolder<'tcx> for SkipBindersAt<'tcx> {
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type Error = ();
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fn tcx(&self) -> TyCtxt<'tcx> {
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self.tcx
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}
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fn try_fold_binder<T>(&mut self, t: Binder<'tcx, T>) -> Result<Binder<'tcx, T>, Self::Error>
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where
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T: ty::TypeFoldable<'tcx>,
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{
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self.index.shift_in(1);
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let value = t.try_map_bound(|t| t.try_fold_with(self));
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self.index.shift_out(1);
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value
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}
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fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
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if !ty.has_escaping_bound_vars() {
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Ok(ty)
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} else if let ty::Bound(index, bv) = *ty.kind() {
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if index == self.index {
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Err(())
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} else {
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Ok(self.tcx().mk_ty(ty::Bound(index.shifted_out(1), bv)))
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}
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} else {
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ty.try_super_fold_with(self)
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}
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}
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fn try_fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, Self::Error> {
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if !r.has_escaping_bound_vars() {
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Ok(r)
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} else if let ty::ReLateBound(index, bv) = r.kind() {
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if index == self.index {
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Err(())
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} else {
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Ok(self.tcx().mk_region(ty::ReLateBound(index.shifted_out(1), bv)))
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}
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} else {
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r.try_super_fold_with(self)
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}
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}
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fn try_fold_const(&mut self, ct: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
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if !ct.has_escaping_bound_vars() {
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Ok(ct)
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} else if let ty::ConstKind::Bound(index, bv) = ct.kind() {
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if index == self.index {
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Err(())
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} else {
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Ok(self.tcx().mk_const(
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ty::ConstKind::Bound(index.shifted_out(1), bv),
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ct.ty().try_fold_with(self)?,
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))
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}
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} else {
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ct.try_super_fold_with(self)
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}
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}
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fn try_fold_predicate(
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&mut self,
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p: ty::Predicate<'tcx>,
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) -> Result<ty::Predicate<'tcx>, Self::Error> {
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if !p.has_escaping_bound_vars() { Ok(p) } else { p.try_super_fold_with(self) }
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}
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}
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/// Represents the projection of an associated type.
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///
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/// For a projection, this would be `<Ty as Trait<...>>::N`.
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@ -213,7 +213,7 @@ impl<'tcx> EvalCtxt<'tcx> {
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// recanonicalizing.
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let Goal { param_env, predicate } = canonical_goal.value;
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if let Some(kind) = predicate.kind().no_bound_vars() {
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if let Some(kind) = predicate.kind().no_bound_vars_ignoring_escaping(self.tcx) {
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match kind {
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ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => self.compute_trait_goal(
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canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
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