Auto merge of #101241 - camsteffen:refactor-binding-annotations, r=cjgillot

`BindingAnnotation` refactor

* `ast::BindingMode` is deleted and replaced with `hir::BindingAnnotation` (which is moved to `ast`)
* `BindingAnnotation` is changed from an enum to a tuple struct e.g. `BindingAnnotation(ByRef::No, Mutability::Mut)`
* Associated constants added for convenience `BindingAnnotation::{NONE, REF, MUT, REF_MUT}`

One goal is to make it more clear that `BindingAnnotation` merely represents syntax `ref mut` and not the actual binding mode. This was especially confusing since we had `ast::BindingMode`->`hir::BindingAnnotation`->`thir::BindingMode`.

I wish there were more symmetry between `ByRef` and `Mutability` (variant) naming (maybe `Mutable::Yes`?), and I also don't love how long the name `BindingAnnotation` is, but this seems like the best compromise. Ideas welcome.

1 files changed, 3 insertions, 3 deletions

diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 9de7962bee3..77babeb5d39 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -577,7 +577,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let (pat, task_context_hid) = self.pat_ident_binding_mode(
             span,
             Ident::with_dummy_span(sym::_task_context),
-            hir::BindingAnnotation::Mutable,
+            hir::BindingAnnotation::MUT,
         );
         let param = hir::Param {
             hir_id: self.next_id(),
@@ -671,7 +671,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // this name to identify what is being awaited by a suspended async functions.
         let awaitee_ident = Ident::with_dummy_span(sym::__awaitee);
         let (awaitee_pat, awaitee_pat_hid) =
-            self.pat_ident_binding_mode(span, awaitee_ident, hir::BindingAnnotation::Mutable);
+            self.pat_ident_binding_mode(span, awaitee_ident, hir::BindingAnnotation::MUT);
 
         let task_context_ident = Ident::with_dummy_span(sym::_task_context);
 
@@ -1433,7 +1433,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // `mut iter`
         let iter = Ident::with_dummy_span(sym::iter);
         let (iter_pat, iter_pat_nid) =
-            self.pat_ident_binding_mode(head_span, iter, hir::BindingAnnotation::Mutable);
+            self.pat_ident_binding_mode(head_span, iter, hir::BindingAnnotation::MUT);
 
         // `match Iterator::next(&mut iter) { ... }`
         let match_expr = {