bjoernager/rust
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Explain the span search logic

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This commit is contained in:
Oli Scherer 2022-04-12 12:31:00 +00:00
parent 08ef70bd13
commit 93a3cfb748
1 changed files with 6 additions and 0 deletions
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6
compiler/rustc_typeck/src/coherence/orphan.rs
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@ -146,11 +146,14 @@ fn orphan_check_impl(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGua
// and #84660 where it would otherwise allow unsoundness. // and #84660 where it would otherwise allow unsoundness.
if trait_ref.has_opaque_types() { if trait_ref.has_opaque_types() {
trace!("{:#?}", item); trace!("{:#?}", item);
// First we find the opaque type in question.
for ty in trait_ref.substs { for ty in trait_ref.substs {
for ty in ty.walk() { for ty in ty.walk() {
let ty::subst::GenericArgKind::Type(ty) = ty.unpack() else { continue }; let ty::subst::GenericArgKind::Type(ty) = ty.unpack() else { continue };
let ty::Opaque(def_id, _) = *ty.kind() else { continue }; let ty::Opaque(def_id, _) = *ty.kind() else { continue };
trace!(?def_id); trace!(?def_id);
// Then we search for mentions of the opaque type's type alias in the HIR
struct SpanFinder<'tcx> { struct SpanFinder<'tcx> {
sp: Span, sp: Span,
def_id: DefId, def_id: DefId,
@ -159,11 +162,14 @@ fn orphan_check_impl(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGua
impl<'v, 'tcx> hir::intravisit::Visitor<'v> for SpanFinder<'tcx> { impl<'v, 'tcx> hir::intravisit::Visitor<'v> for SpanFinder<'tcx> {
#[instrument(level = "trace", skip(self, _id))] #[instrument(level = "trace", skip(self, _id))]
fn visit_path(&mut self, path: &'v hir::Path<'v>, _id: hir::HirId) { 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 { 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() { for arg in self.tcx.type_of(def_id).walk() {
if let GenericArgKind::Type(ty) = arg.unpack() { if let GenericArgKind::Type(ty) = arg.unpack() {
if let ty::Opaque(def_id, _) = *ty.kind() { if let ty::Opaque(def_id, _) = *ty.kind() {
if def_id == self.def_id { if def_id == self.def_id {
// Finally we update the span to the mention of the type alias
self.sp = path.span; self.sp = path.span;
return; return;
} }