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Rollup merge of #104296 - compiler-errors:opaque-ty-ffi-normalization-cycle, r=lcnr

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Walk types more carefully in `ProhibitOpaqueTypes` visitor

The visitor didn't account for the case where you could have `<TAIT as Trait>::Assoc` normalize to itself, in the case of a `type TAIT = impl Trait` with an unconstrained associated type. That causes the visitor to loop on the same type over and over.

Fixes #104291
This commit is contained in:
Matthias Krüger 2022-11-15 10:44:10 +01:00 • committed by GitHub
commit d8b416db0a
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3 changed files with 72 additions and 21 deletions
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37
compiler/rustc_lint/src/types.rs
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@ -1195,35 +1195,30 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
}
fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
struct ProhibitOpaqueTypes<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
}
impl<'a, 'tcx> ty::visit::TypeVisitor<'tcx> for ProhibitOpaqueTypes<'a, 'tcx> {
struct ProhibitOpaqueTypes;
impl<'tcx> ty::visit::TypeVisitor<'tcx> for ProhibitOpaqueTypes {
type BreakTy = Ty<'tcx>;
fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
match ty.kind() {
ty::Opaque(..) => ControlFlow::Break(ty),
// Consider opaque types within projections FFI-safe if they do not normalize
// to more opaque types.
ty::Projection(..) => {
let ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, ty);
if !ty.has_opaque_types() {
return ControlFlow::CONTINUE;
}
// If `ty` is an opaque type directly then `super_visit_with` won't invoke
// this function again.
if ty.has_opaque_types() {
self.visit_ty(ty)
} else {
ControlFlow::CONTINUE
}
}
_ => ty.super_visit_with(self),
if let ty::Opaque(..) = ty.kind() {
ControlFlow::Break(ty)
} else {
ty.super_visit_with(self)
}
}
}
if let Some(ty) = ty.visit_with(&mut ProhibitOpaqueTypes { cx: self.cx }).break_value() {
if let Some(ty) = self
.cx
.tcx
.normalize_erasing_regions(self.cx.param_env, ty)
.visit_with(&mut ProhibitOpaqueTypes)
.break_value()
{
self.emit_ffi_unsafe_type_lint(ty, sp, fluent::lint_improper_ctypes_opaque, None);
true
} else {