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Report that opaque types are not allowed in impls even in the presence of other errors

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This commit is contained in:
Oli Scherer 2022-05-03 13:53:53 +00:00
parent 468492c2af
commit efc6a6f1bd
4 changed files with 64 additions and 58 deletions
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105
compiler/rustc_typeck/src/coherence/orphan.rs
View File

@ -44,6 +44,59 @@ fn orphan_check_impl(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGua
};
let sp = tcx.sess.source_map().guess_head_span(item.span);
let tr = impl_.of_trait.as_ref().unwrap();
// Ensure no opaque types are present in this impl header. See issues #76202 and #86411 for examples,
// and #84660 where it would otherwise allow unsoundness.
if trait_ref.has_opaque_types() {
trace!("{:#?}", item);
// First we find the opaque type in question.
for ty in trait_ref.substs {
for ty in ty.walk() {
let ty::subst::GenericArgKind::Type(ty) = ty.unpack() else { continue };
let ty::Opaque(def_id, _) = *ty.kind() else { continue };
trace!(?def_id);
// Then we search for mentions of the opaque type's type alias in the HIR
struct SpanFinder<'tcx> {
sp: Span,
def_id: DefId,
tcx: TyCtxt<'tcx>,
}
impl<'v, 'tcx> hir::intravisit::Visitor<'v> for SpanFinder<'tcx> {
#[instrument(level = "trace", skip(self, _id))]
fn visit_path(&mut self, path: &'v hir::Path<'v>, _id: hir::HirId) {
// You can't mention an opaque type directly, so we look for type aliases
if let hir::def::Res::Def(hir::def::DefKind::TyAlias, def_id) = path.res {
// And check if that type alias's type contains the opaque type we're looking for
for arg in self.tcx.type_of(def_id).walk() {
if let GenericArgKind::Type(ty) = arg.unpack() {
if let ty::Opaque(def_id, _) = *ty.kind() {
if def_id == self.def_id {
// Finally we update the span to the mention of the type alias
self.sp = path.span;
return;
}
}
}
}
}
hir::intravisit::walk_path(self, path)
}
}
let mut visitor = SpanFinder { sp, def_id, tcx };
hir::intravisit::walk_item(&mut visitor, item);
let reported = tcx
.sess
.struct_span_err(visitor.sp, "cannot implement trait on type alias impl trait")
.span_note(tcx.def_span(def_id), "type alias impl trait defined here")
.emit();
return Err(reported);
}
}
span_bug!(sp, "opaque type not found, but `has_opaque_types` is set")
}
match traits::orphan_check(tcx, item.def_id.to_def_id()) {
Ok(()) => {}
Err(err) => emit_orphan_check_error(
@ -143,58 +196,6 @@ fn orphan_check_impl(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGua
}
}
// Ensure no opaque types are present in this impl header. See issues #76202 and #86411 for examples,
// and #84660 where it would otherwise allow unsoundness.
if trait_ref.has_opaque_types() {
trace!("{:#?}", item);
// First we find the opaque type in question.
for ty in trait_ref.substs {
for ty in ty.walk() {
let ty::subst::GenericArgKind::Type(ty) = ty.unpack() else { continue };
let ty::Opaque(def_id, _) = *ty.kind() else { continue };
trace!(?def_id);
// Then we search for mentions of the opaque type's type alias in the HIR
struct SpanFinder<'tcx> {
sp: Span,
def_id: DefId,
tcx: TyCtxt<'tcx>,
}
impl<'v, 'tcx> hir::intravisit::Visitor<'v> for SpanFinder<'tcx> {
#[instrument(level = "trace", skip(self, _id))]
fn visit_path(&mut self, path: &'v hir::Path<'v>, _id: hir::HirId) {
// You can't mention an opaque type directly, so we look for type aliases
if let hir::def::Res::Def(hir::def::DefKind::TyAlias, def_id) = path.res {
// And check if that type alias's type contains the opaque type we're looking for
for arg in self.tcx.type_of(def_id).walk() {
if let GenericArgKind::Type(ty) = arg.unpack() {
if let ty::Opaque(def_id, _) = *ty.kind() {
if def_id == self.def_id {
// Finally we update the span to the mention of the type alias
self.sp = path.span;
return;
}
}
}
}
}
hir::intravisit::walk_path(self, path)
}
}
let mut visitor = SpanFinder { sp, def_id, tcx };
hir::intravisit::walk_item(&mut visitor, item);
let reported = tcx
.sess
.struct_span_err(visitor.sp, "cannot implement trait on type alias impl trait")
.span_note(tcx.def_span(def_id), "type alias impl trait defined here")
.emit();
return Err(reported);
}
}
span_bug!(sp, "opaque type not found, but `has_opaque_types` is set")
}
Ok(())
}

2
compiler/rustc_typeck/src/constrained_generic_params.rs
View File

@ -59,7 +59,7 @@ struct ParameterCollector {
impl<'tcx> TypeVisitor<'tcx> for ParameterCollector {
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
match *t.kind() {
ty::Projection(..) | ty::Opaque(..) if !self.include_nonconstraining => {
ty::Projection(..) if !self.include_nonconstraining => {
// projections are not injective
return ControlFlow::CONTINUE;
}

2
src/test/ui/type-alias-impl-trait/coherence.rs
View File

@ -12,6 +12,6 @@ fn use_alias<T>(val: T) -> AliasOfForeignType<T> {
}
impl<T> foreign_crate::ForeignTrait for AliasOfForeignType<T> {}
//~^ ERROR the type parameter `T` is not constrained by the impl trait, self type, or predicates
//~^ ERROR cannot implement trait on type alias impl trait
fn main() {}

13
src/test/ui/type-alias-impl-trait/coherence.stderr
View File

@ -1,9 +1,14 @@
error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates
--> $DIR/coherence.rs:14:6
error: cannot implement trait on type alias impl trait
--> $DIR/coherence.rs:14:41
|
LL | impl<T> foreign_crate::ForeignTrait for AliasOfForeignType<T> {}
| ^ unconstrained type parameter
| ^^^^^^^^^^^^^^^^^^^^^
|
note: type alias impl trait defined here
--> $DIR/coherence.rs:9:30
|
LL | type AliasOfForeignType<T> = impl LocalTrait;
| ^^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0207`.