Rollup merge of #134797 - spastorino:ergonomic-ref-counting-1, r=nikomatsakis

Ergonomic ref counting

This is an experimental first version of ergonomic ref counting.

This first version implements most of the RFC but doesn't implement any of the optimizations. This was left for following iterations.

RFC: https://github.com/rust-lang/rfcs/pull/3680
Tracking issue: https://github.com/rust-lang/rust/issues/132290
Project goal: https://github.com/rust-lang/rust-project-goals/issues/107

r? ```@nikomatsakis```

compiler/rustc_ty_utils/messages.ftl

@@ -14,6 +14,8 @@ ty_utils_borrow_not_supported = borrowing is not supported in generic constants
 
 ty_utils_box_not_supported = allocations are not allowed in generic constants
 
+ty_utils_by_use_not_supported = .use is not allowed in generic constants
+
 ty_utils_closure_and_return_not_supported = closures and function keywords are not supported in generic constants
 
 ty_utils_const_block_not_supported = const blocks are not supported in generic constants

compiler/rustc_ty_utils/src/common_traits.rs

@@ -10,6 +10,13 @@ fn is_copy_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::PseudoCanonicalInput<'tcx, Ty
     is_item_raw(tcx, query, LangItem::Copy)
 }
 
+fn is_use_cloned_raw<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    query: ty::PseudoCanonicalInput<'tcx, Ty<'tcx>>,
+) -> bool {
+    is_item_raw(tcx, query, LangItem::UseCloned)
+}
+
 fn is_sized_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::PseudoCanonicalInput<'tcx, Ty<'tcx>>) -> bool {
     is_item_raw(tcx, query, LangItem::Sized)
 }
@@ -33,5 +40,12 @@ fn is_item_raw<'tcx>(
 }
 
 pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { is_copy_raw, is_sized_raw, is_freeze_raw, is_unpin_raw, ..*providers };
+    *providers = Providers {
+        is_copy_raw,
+        is_use_cloned_raw,
+        is_sized_raw,
+        is_freeze_raw,
+        is_unpin_raw,
+        ..*providers
+    };
 }

compiler/rustc_ty_utils/src/consts.rs

@@ -230,7 +230,9 @@ fn recurse_build<'tcx>(
             error(GenericConstantTooComplexSub::LoopNotSupported(node.span))?
         }
         ExprKind::Box { .. } => error(GenericConstantTooComplexSub::BoxNotSupported(node.span))?,
-
+        ExprKind::ByUse { .. } => {
+            error(GenericConstantTooComplexSub::ByUseNotSupported(node.span))?
+        }
         ExprKind::Unary { .. } => unreachable!(),
         // we handle valid unary/binary ops above
         ExprKind::Binary { .. } => {
@@ -317,6 +319,7 @@ impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> {
             | thir::ExprKind::Box { .. }
             | thir::ExprKind::If { .. }
             | thir::ExprKind::Call { .. }
+            | thir::ExprKind::ByUse { .. }
             | thir::ExprKind::Deref { .. }
             | thir::ExprKind::Binary { .. }
             | thir::ExprKind::LogicalOp { .. }

compiler/rustc_ty_utils/src/errors.rs

@@ -55,6 +55,8 @@ pub(crate) enum GenericConstantTooComplexSub {
     BoxNotSupported(#[primary_span] Span),
     #[label(ty_utils_binary_not_supported)]
     BinaryNotSupported(#[primary_span] Span),
+    #[label(ty_utils_by_use_not_supported)]
+    ByUseNotSupported(#[primary_span] Span),
     #[label(ty_utils_logical_op_not_supported)]
     LogicalOpNotSupported(#[primary_span] Span),
     #[label(ty_utils_assign_not_supported)]