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Rollup merge of #102338 - compiler-errors:assoc-ty-binding-in-assoc-ty-binding, r=cjgillot

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Deny associated type bindings within associated type bindings

Fixes #102335

This was made worse by #100865, which unified the way we generate substs for GATs and non-generic associated types. However, the issue was not _caused_ by #100865, evidenced by the test I added for GATs:

```rust
trait T {
    type A: S<C<(), i32 = ()> = ()>;
    //~^ ERROR associated type bindings are not allowed here
}

trait Q {}

trait S {
    type C<T>: Q;
}

fn main() {}
```

^ which passes on beta (where GATs are stable) and presumably ever since GATs support was added to `create_substs_for_associated_item` in astconv.
This commit is contained in:
Yuki Okushi 2022-09-28 13:07:18 +09:00 • committed by GitHub
commit b263b7e64c
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9 changed files with 82 additions and 5 deletions
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12
compiler/rustc_hir_analysis/src/astconv/mod.rs
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@ -595,7 +595,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
"create_substs_for_associated_item(span: {:?}, item_def_id: {:?}, item_segment: {:?}",
span, item_def_id, item_segment
);
self.create_substs_for_ast_path(
let (args, _) = self.create_substs_for_ast_path(
span,
item_def_id,
parent_substs,
@ -603,8 +603,14 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
item_segment.args(),
item_segment.infer_args,
None,
)
.0
);
let assoc_bindings = self.create_assoc_bindings_for_generic_args(item_segment.args());
if let Some(b) = assoc_bindings.first() {
Self::prohibit_assoc_ty_binding(self.tcx(), b.span);
}
args
}
/// Instantiates the path for the given trait reference, assuming that it's