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Normalize lazy type aliases when probing for ADTs #113755

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Merged
merged 1 commit into from
Jul 17, 2023
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Normalize lazy type aliases when probing for ADTs #113755

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4 changes: 3 additions & 1 deletion compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -302,7 +302,9 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
match ty.kind() {
ty::Adt(adt_def, _) => Some(*adt_def),
// FIXME(#104767): Should we handle bound regions here?
ty::Alias(ty::Projection | ty::Inherent, _) if !ty.has_escaping_bound_vars() => {
ty::Alias(ty::Projection | ty::Inherent | ty::Weak, _)
if !ty.has_escaping_bound_vars() =>
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@fmease fmease Jul 16, 2023 •
edited
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Couldn't come up with a snippet containing a weak type alias in expression position that has escaping bound vars.

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Can't have it in path expressions, which is where this would be encountered afaict.

Also, should we only normalize away the layers of lazy type alias? This also has the side effect of an alias that normalizes to a regular projection gets normalized.

Why don't we normalize here to begin with? Does @aliemjay know?

rust/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

Line 1096 in 11da267

self_ty.map(|ty| ty.raw),

Ideally, this would just pass ty.normalized instead of ty.raw...

{
self.normalize(span, ty).ty_adt_def()
}
_ => None,
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17 changes: 17 additions & 0 deletions tests/ui/type-alias/lazy-type-alias-enum-variant.rs
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@@ -0,0 +1,17 @@
// Regression test for issue #113736.
// check-pass

#![feature(lazy_type_alias)]

enum Enum {
Unit,
Tuple(),
Struct {},
}

fn main() {
type Alias = Enum;
let _ = Alias::Unit;
let _ = Alias::Tuple();
let _ = Alias::Struct {};
}