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Add AliasKind::Weak for type aliases.

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Only use it when the type alias contains an opaque type.

Also does wf-checking on such type aliases.
This commit is contained in:
Oli Scherer
2023-03-07 12:03:11 +00:00
parent 4fdd07fe88
commit f3b7dd6388
86 changed files with 474 additions and 199 deletions
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40
compiler/rustc_hir_analysis/src/check/wfcheck.rs
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@@ -217,10 +217,10 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
check_item_fn(tcx, def_id, item.ident, item.span, sig.decl);
}
hir::ItemKind::Static(ty, ..) => {
check_item_type(tcx, def_id, ty.span, false);
check_item_type(tcx, def_id, ty.span, UnsizedHandling::Forbid);
}
hir::ItemKind::Const(ty, ..) => {
check_item_type(tcx, def_id, ty.span, false);
check_item_type(tcx, def_id, ty.span, UnsizedHandling::Forbid);
}
hir::ItemKind::Struct(_, ast_generics) => {
check_type_defn(tcx, item, false);
@@ -242,6 +242,12 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
}
// `ForeignItem`s are handled separately.
hir::ItemKind::ForeignMod { .. } => {}
hir::ItemKind::TyAlias(hir_ty, ..) => {
if tcx.type_of(item.owner_id.def_id).skip_binder().has_opaque_types() {
// Bounds are respected for `type X = impl Trait` and `type X = (impl Trait, Y);`
check_item_type(tcx, def_id, hir_ty.span, UnsizedHandling::Allow);
}
}
_ => {}
}
}
@@ -258,7 +264,9 @@ fn check_foreign_item(tcx: TyCtxt<'_>, item: &hir::ForeignItem<'_>) {
hir::ForeignItemKind::Fn(decl, ..) => {
check_item_fn(tcx, def_id, item.ident, item.span, decl)
}
hir::ForeignItemKind::Static(ty, ..) => check_item_type(tcx, def_id, ty.span, true),
hir::ForeignItemKind::Static(ty, ..) => {
check_item_type(tcx, def_id, ty.span, UnsizedHandling::AllowIfForeignTail)
}
hir::ForeignItemKind::Type => (),
}
}
@@ -1100,20 +1108,32 @@ fn check_item_fn(
})
}
fn check_item_type(tcx: TyCtxt<'_>, item_id: LocalDefId, ty_span: Span, allow_foreign_ty: bool) {
enum UnsizedHandling {
Forbid,
Allow,
AllowIfForeignTail,
}
fn check_item_type(
tcx: TyCtxt<'_>,
item_id: LocalDefId,
ty_span: Span,
unsized_handling: UnsizedHandling,
) {
debug!("check_item_type: {:?}", item_id);
enter_wf_checking_ctxt(tcx, ty_span, item_id, |wfcx| {
let ty = tcx.type_of(item_id).subst_identity();
let item_ty = wfcx.normalize(ty_span, Some(WellFormedLoc::Ty(item_id)), ty);
let mut forbid_unsized = true;
if allow_foreign_ty {
let tail = tcx.struct_tail_erasing_lifetimes(item_ty, wfcx.param_env);
if let ty::Foreign(_) = tail.kind() {
forbid_unsized = false;
let forbid_unsized = match unsized_handling {
UnsizedHandling::Forbid => true,
UnsizedHandling::Allow => false,
UnsizedHandling::AllowIfForeignTail => {
let tail = tcx.struct_tail_erasing_lifetimes(item_ty, wfcx.param_env);
!matches!(tail.kind(), ty::Foreign(_))
}
}
};
wfcx.register_wf_obligation(ty_span, Some(WellFormedLoc::Ty(item_id)), item_ty.into());
if forbid_unsized {