Rollup merge of rust-lang#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: rust-lang/rfcs#3680
Tracking issue: rust-lang#132290
Project goal: rust-lang/rust-project-goals#107

r? ```@nikomatsakis```

Author: matthiaskrgr

clippy_lints/src/escape.rs

@@ -150,6 +150,8 @@ impl<'tcx> Delegate<'tcx> for EscapeDelegate<'_, 'tcx> {
         }
     }
 
+    fn use_cloned(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
+
     fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {
         if cmt.place.projections.is_empty() {
             if let PlaceBase::Local(lid) = cmt.place.base {

clippy_lints/src/loops/mut_range_bound.rs

@@ -79,6 +79,8 @@ struct MutatePairDelegate<'a, 'tcx> {
 impl<'tcx> Delegate<'tcx> for MutatePairDelegate<'_, 'tcx> {
     fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
 
+    fn use_cloned(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
+
     fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, diag_expr_id: HirId, bk: ty::BorrowKind) {
         if bk == ty::BorrowKind::Mutable {
             if let PlaceBase::Local(id) = cmt.place.base {

clippy_lints/src/loops/never_loop.rs

@@ -160,6 +160,7 @@ fn never_loop_expr<'tcx>(
         | ExprKind::UnsafeBinderCast(_, e, _) => never_loop_expr(cx, e, local_labels, main_loop_id),
         ExprKind::Let(let_expr) => never_loop_expr(cx, let_expr.init, local_labels, main_loop_id),
         ExprKind::Array(es) | ExprKind::Tup(es) => never_loop_expr_all(cx, es.iter(), local_labels, main_loop_id),
+        ExprKind::Use(expr, _) => never_loop_expr(cx, expr, local_labels, main_loop_id),
         ExprKind::MethodCall(_, receiver, es, _) => {
             never_loop_expr_all(cx, once(receiver).chain(es.iter()), local_labels, main_loop_id)
         },

clippy_lints/src/matches/manual_utils.rs

@@ -99,7 +99,7 @@ where
                 });
                 if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
                     match captures.get(l) {
-                        Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return None,
+                        Some(CaptureKind::Value | CaptureKind::Use | CaptureKind::Ref(Mutability::Mut)) => return None,
                         Some(CaptureKind::Ref(Mutability::Not)) if binding_ref_mutability == Mutability::Mut => {
                             return None;
                         },

clippy_lints/src/methods/iter_overeager_cloned.rs

@@ -147,6 +147,8 @@ impl<'tcx> Delegate<'tcx> for MoveDelegate {
         }
     }
 
+    fn use_cloned(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
+
     fn borrow(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId, _: BorrowKind) {}
 
     fn mutate(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}

clippy_lints/src/needless_pass_by_ref_mut.rs

@@ -396,6 +396,8 @@ impl<'tcx> euv::Delegate<'tcx> for MutablyUsedVariablesCtxt<'tcx> {
         }
     }
 
+    fn use_cloned(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId) {}
+
     #[allow(clippy::if_same_then_else)]
     fn borrow(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, id: HirId, borrow: ty::BorrowKind) {
         self.prev_bind = None;

clippy_lints/src/needless_pass_by_value.rs

@@ -326,6 +326,8 @@ impl<'tcx> euv::Delegate<'tcx> for MovedVariablesCtxt {
         self.move_common(cmt);
     }
 
+    fn use_cloned(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId) {}
+
     fn borrow(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {}
 
     fn mutate(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: HirId) {}

clippy_lints/src/operators/assign_op_pattern.rs

@@ -112,6 +112,7 @@ fn imm_borrows_in_expr(cx: &LateContext<'_>, e: &hir::Expr<'_>) -> HirIdSet {
         }
 
         fn consume(&mut self, _: &PlaceWithHirId<'_>, _: HirId) {}
+        fn use_cloned(&mut self, _: &PlaceWithHirId<'_>, _: HirId) {}
         fn mutate(&mut self, _: &PlaceWithHirId<'_>, _: HirId) {}
         fn fake_read(&mut self, _: &PlaceWithHirId<'_>, _: FakeReadCause, _: HirId) {}
         fn copy(&mut self, _: &PlaceWithHirId<'_>, _: HirId) {}
@@ -137,6 +138,7 @@ fn mut_borrows_in_expr(cx: &LateContext<'_>, e: &hir::Expr<'_>) -> HirIdSet {
         }
 
         fn consume(&mut self, _: &PlaceWithHirId<'_>, _: HirId) {}
+        fn use_cloned(&mut self, _: &PlaceWithHirId<'_>, _: HirId) {}
         fn mutate(&mut self, _: &PlaceWithHirId<'_>, _: HirId) {}
         fn fake_read(&mut self, _: &PlaceWithHirId<'_>, _: FakeReadCause, _: HirId) {}
         fn copy(&mut self, _: &PlaceWithHirId<'_>, _: HirId) {}

clippy_lints/src/option_if_let_else.rs

@@ -177,7 +177,7 @@ fn try_get_option_occurrence<'tcx>(
                         .then_some(())
                         .and_then(|()| none_captures.get(local_id))
                 }) {
-                    Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return None,
+                    Some(CaptureKind::Value | CaptureKind::Use | CaptureKind::Ref(Mutability::Mut)) => return None,
                     Some(CaptureKind::Ref(Mutability::Not)) if as_mut => return None,
                     Some(CaptureKind::Ref(Mutability::Not)) | None => (),
                 }

clippy_lints/src/unwrap.rs

@@ -230,6 +230,8 @@ impl<'tcx> Delegate<'tcx> for MutationVisitor<'tcx> {
 
     fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
 
+    fn use_cloned(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
+
     fn fake_read(&mut self, _: &PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
 }