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Don't unnecessarily lower associated type bounds to impl trait

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This commit is contained in:
Michael Goulet 2024-02-02 00:41:26 +00:00
parent 22d582a38d
commit 548929dc5e
1 changed files with 11 additions and 13 deletions
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24
compiler/rustc_ast_lowering/src/lib.rs
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@ -1094,24 +1094,22 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
// Piggy-back on the `impl Trait` context to figure out the correct behavior.
let desugar_kind = match itctx {
// We are in the return position:
//
// fn foo() -> impl Iterator<Item: Debug>
//
// so desugar to
//
// fn foo() -> impl Iterator<Item = impl Debug>
ImplTraitContext::ReturnPositionOpaqueTy { .. }
| ImplTraitContext::TypeAliasesOpaqueTy { .. } => DesugarKind::ImplTrait,
// We are in the argument position, but within a dyn type:
// in an argument, RPIT, or TAIT, if we are within a dyn type:
//
// fn foo(x: dyn Iterator<Item: Debug>)
//
// so desugar to
// then desugar to:
//
// fn foo(x: dyn Iterator<Item = impl Debug>)
ImplTraitContext::Universal if self.is_in_dyn_type => DesugarKind::ImplTrait,
//
// This is because dyn traits must have all of their associated types specified.
ImplTraitContext::ReturnPositionOpaqueTy { .. }
| ImplTraitContext::TypeAliasesOpaqueTy { .. }
| ImplTraitContext::Universal
if self.is_in_dyn_type =>
{
DesugarKind::ImplTrait
}
ImplTraitContext::Disallowed(position) if self.is_in_dyn_type => {
DesugarKind::Error(position)