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consider placeholders in fn term_is_fully_unconstrained

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This commit is contained in:
lcnr 2024-02-26 11:51:01 +01:00
parent 1c264ca9ca
commit 3b3514acec
1 changed files with 49 additions and 37 deletions
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86
compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
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@ -608,8 +608,8 @@ pub(super) fn next_term_infer_of_kind(&self, kind: ty::Term<'tcx>) -> ty::Term<'
/// Is the projection predicate is of the form `exists<T> <Ty as Trait>::Assoc = T`.
///
/// This is the case if the `term` is an inference variable in the innermost universe
/// and does not occur in any other part of the predicate.
/// This is the case if the `term` does not occur in any other part of the predicate
/// and is able to name all other placeholder and inference variables.
#[instrument(level = "debug", skip(self), ret)]
pub(super) fn term_is_fully_unconstrained(
&self,
@ -632,55 +632,67 @@ pub(super) fn term_is_fully_unconstrained(
}
};
// Guard against `<T as Trait<?0>>::Assoc = ?0>`.
struct ContainsTermOrNotNameable<'a, 'tcx> {
term: ty::Term<'tcx>,
universe_of_term: ty::UniverseIndex,
infcx: &'a InferCtxt<'tcx>,
}
impl<'a, 'tcx> ContainsTermOrNotNameable<'a, 'tcx> {
fn check_nameable(&self, universe: ty::UniverseIndex) -> ControlFlow<()> {
if self.universe_of_term.can_name(universe) {
ControlFlow::Continue(())
} else {
ControlFlow::Break(())
}
}
}
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ContainsTermOrNotNameable<'_, 'tcx> {
type BreakTy = ();
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
if let Some(vid) = t.ty_vid() {
if let ty::TermKind::Ty(term) = self.term.unpack()
&& let Some(term_vid) = term.ty_vid()
&& self.infcx.root_var(vid) == self.infcx.root_var(term_vid)
{
ControlFlow::Break(())
} else if self
.universe_of_term
.cannot_name(self.infcx.universe_of_ty(vid).unwrap())
{
ControlFlow::Break(())
} else {
ControlFlow::Continue(())
match *t.kind() {
ty::Infer(ty::TyVar(vid)) => {
if let ty::TermKind::Ty(term) = self.term.unpack()
&& let Some(term_vid) = term.ty_vid()
&& self.infcx.root_var(vid) == self.infcx.root_var(term_vid)
{
ControlFlow::Break(())
} else {
self.check_nameable(self.infcx.universe_of_ty(vid).unwrap())
}
}
ty::Placeholder(p) => self.check_nameable(p.universe),
_ => {
if t.has_non_region_infer() || t.has_placeholders() {
t.super_visit_with(self)
} else {
ControlFlow::Continue(())
}
}
} else if t.has_non_region_infer() {
t.super_visit_with(self)
} else {
ControlFlow::Continue(())
}
}
fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
if let ty::ConstKind::Infer(ty::InferConst::Var(vid)) = c.kind() {
if let ty::TermKind::Const(term) = self.term.unpack()
&& let ty::ConstKind::Infer(ty::InferConst::Var(term_vid)) = term.kind()
&& self.infcx.root_const_var(vid) == self.infcx.root_const_var(term_vid)
{
ControlFlow::Break(())
} else if self
.universe_of_term
.cannot_name(self.infcx.universe_of_ct(vid).unwrap())
{
ControlFlow::Break(())
} else {
ControlFlow::Continue(())
match c.kind() {
ty::ConstKind::Infer(ty::InferConst::Var(vid)) => {
if let ty::TermKind::Const(term) = self.term.unpack()
&& let ty::ConstKind::Infer(ty::InferConst::Var(term_vid)) = term.kind()
&& self.infcx.root_const_var(vid) == self.infcx.root_const_var(term_vid)
{
ControlFlow::Break(())
} else {
self.check_nameable(self.infcx.universe_of_ct(vid).unwrap())
}
}
ty::ConstKind::Placeholder(p) => self.check_nameable(p.universe),
_ => {
if c.has_non_region_infer() || c.has_placeholders() {
c.super_visit_with(self)
} else {
ControlFlow::Continue(())
}
}
} else if c.has_non_region_infer() {
c.super_visit_with(self)
} else {
ControlFlow::Continue(())
}
}
}