Auto merge of #115367 - frank-king:feature/unnamed-fields-hir, r=davidtwco

Lowering unnamed fields and anonymous adt

This implements #49804.

Goals:
- [x] lowering anonymous ADTs from AST to HIR
- [x] generating definitions of anonymous ADTs
- [x] uniqueness check of the unnamed fields
- [x] field projection of anonymous ADTs
- [x] `#[repr(C)]` check of the anonymous ADTs

Non-Goals (will be in the next PRs)
- capturing generic params for the anonymous ADTs from the parent ADT
- pattern matching of anonymous ADTs
- structural expressions of anonymous ADTs
- rustdoc support of anonymous ADTs

Author: bors

compiler/rustc_ast/src/ast.rs

@@ -2107,9 +2107,9 @@ pub enum TyKind {
     /// A tuple (`(A, B, C, D,...)`).
     Tup(ThinVec<P<Ty>>),
     /// An anonymous struct type i.e. `struct { foo: Type }`
-    AnonStruct(ThinVec<FieldDef>),
+    AnonStruct(NodeId, ThinVec<FieldDef>),
     /// An anonymous union type i.e. `union { bar: Type }`
-    AnonUnion(ThinVec<FieldDef>),
+    AnonUnion(NodeId, ThinVec<FieldDef>),
     /// A path (`module::module::...::Type`), optionally
     /// "qualified", e.g., `<Vec<T> as SomeTrait>::SomeType`.
     ///
@@ -2161,6 +2161,10 @@ impl TyKind {
             None
         }
     }
+
+    pub fn is_anon_adt(&self) -> bool {
+        matches!(self, TyKind::AnonStruct(..) | TyKind::AnonUnion(..))
+    }
 }
 
 /// Syntax used to declare a trait object.

compiler/rustc_ast/src/mut_visit.rs

@@ -514,7 +514,8 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
             visit_vec(bounds, |bound| vis.visit_param_bound(bound));
         }
         TyKind::MacCall(mac) => vis.visit_mac_call(mac),
-        TyKind::AnonStruct(fields) | TyKind::AnonUnion(fields) => {
+        TyKind::AnonStruct(id, fields) | TyKind::AnonUnion(id, fields) => {
+            vis.visit_id(id);
             fields.flat_map_in_place(|field| vis.flat_map_field_def(field));
         }
     }