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

1 files changed, 8 insertions, 0 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index ac6cfcdeb59..60453f5ab9c 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2212,6 +2212,14 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
 
             // FIXME(async_closures): These are never clone, for now.
             ty::CoroutineClosure(_, _) => None,
+            // `Copy` and `Clone` are automatically implemented for an anonymous adt
+            // if all of its fields are `Copy` and `Clone`
+            ty::Adt(adt, args) if adt.is_anonymous() => {
+                // (*) binder moved here
+                Where(obligation.predicate.rebind(
+                    adt.non_enum_variant().fields.iter().map(|f| f.ty(self.tcx(), args)).collect(),
+                ))
+            }
 
             ty::Adt(..) | ty::Alias(..) | ty::Param(..) | ty::Placeholder(..) => {
                 // Fallback to whatever user-defined impls exist in this case.