Improve find_self_call with reborrowed receiver

Author: compiler-errors

compiler/rustc_middle/src/util/find_self_call.rs

@@ -17,26 +17,29 @@ pub fn find_self_call<'tcx>(
 debug!("find_self_call(local={:?}): terminator={:?}", local, body[block].terminator);
 ifletSome(Terminator{kind:TerminatorKind::Call{ func, args, .. }, .. }) =
 &body[block].terminator
+ && letOperand::Constant(box ConstOperand{ const_, .. }) = func
+ && let ty::FnDef(def_id, fn_args) = *const_.ty().kind()
+ && letSome(ty::AssocItem{fn_has_self_parameter:true, .. }) =
+ tcx.opt_associated_item(def_id)
+ && let[Spanned{node:Operand::Move(self_place) | Operand::Copy(self_place), .. }, ..] =
+**args
 {
-debug!("find_self_call: func={:?}", func);
-ifletOperand::Constant(box ConstOperand{ const_, .. }) = func {
-iflet ty::FnDef(def_id, fn_args) = *const_.ty().kind(){
-ifletSome(ty::AssocItem{fn_has_self_parameter:true, .. }) =
- tcx.opt_associated_item(def_id)
-{
-debug!("find_self_call: args={:?}", fn_args);
-iflet[
-Spanned{
-node:Operand::Move(self_place) | Operand::Copy(self_place), ..
-},
- ..,
-] = **args
-{
-if self_place.as_local() == Some(local){
-returnSome((def_id, fn_args));
-}
-}
-}
+if self_place.as_local() == Some(local){
+returnSome((def_id, fn_args));
+}
+
+// Handle the case where `self_place` gets reborrowed.
+// This happens when the receiver is `&T`.
+for stmt in&body[block].statements{
+ifletStatementKind::Assign(box (place, rvalue)) = &stmt.kind
+ && letSome(reborrow_local) = place.as_local()
+ && self_place.as_local() == Some(reborrow_local)
+ && letRvalue::Ref(_, _, deref_place) = rvalue
+ && letPlaceRef{local: deref_local,projection:[ProjectionElem::Deref]} =
+ deref_place.as_ref()
+ && deref_local == local
+{
+returnSome((def_id, fn_args));
 }
 }
 }

tests/ui/lint/lint-const-item-mutation.stderr

@@ -75,10 +75,15 @@ warning: taking a mutable reference to a `const` item
  --> $DIR/lint-const-item-mutation.rs:42:5
  |
 LL | (&mut MY_STRUCT).use_mut();
- | ^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: each usage of a `const` item creates a new temporary
  = note: the mutable reference will refer to this temporary, not the original `const` item
+note: mutable reference created due to call to this method
+ --> $DIR/lint-const-item-mutation.rs:9:5
+ |
+LL | fn use_mut(&mut self) {}
+ | ^^^^^^^^^^^^^^^^^^^^^
 note: `const` item defined here
  --> $DIR/lint-const-item-mutation.rs:27:1
  |