---

yaml
---
r: 272854
b: refs/heads/beta
c: cfe4efd
h: refs/heads/master

Author: bluss

[refs]

@@ -23,7 +23,7 @@ refs/tags/0.9: 36870b185fc5f5486636d4515f0e22677493f225
 refs/tags/0.10: ac33f2b15782272ae348dbd7b14b8257b2148b5a
 refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
-refs/heads/beta: d5b6599ab64b2e44d2fe13eea884e2369ffdaa47
+refs/heads/beta: cfe4efd0523cd8106b20ba732f7d7677548f8157
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
 refs/heads/tmp: e06d2ad9fcd5027bcaac5b08fc9aa39a49d0ecd3
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f

branches/beta/src/librustc/middle/liveness.rs

@@ -1086,11 +1086,17 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
           }
 
           hir::ExprAssignOp(_, ref l, ref r) => {
-            // see comment on lvalues in
-            // propagate_through_lvalue_components()
-            let succ = self.write_lvalue(&l, succ, ACC_WRITE|ACC_READ);
-            let succ = self.propagate_through_expr(&r, succ);
-            self.propagate_through_lvalue_components(&l, succ)
+            // an overloaded assign op is like a method call
+            if self.ir.tcx.is_method_call(expr.id) {
+                let succ = self.propagate_through_expr(&l, succ);
+                self.propagate_through_expr(&r, succ)
+            } else {
+                // see comment on lvalues in
+                // propagate_through_lvalue_components()
+                let succ = self.write_lvalue(&l, succ, ACC_WRITE|ACC_READ);
+                let succ = self.propagate_through_expr(&r, succ);
+                self.propagate_through_lvalue_components(&l, succ)
+            }
           }
 
           // Uninteresting cases: just propagate in rev exec order

branches/beta/src/test/compile-fail/liveness-unused.rs

@@ -127,5 +127,24 @@ fn f6() {
     }) += 1;
 }
 
+
+struct MutRef<'a>(&'a mut i32);
+
+impl<'a> AddAssign<i32> for MutRef<'a> {
+    fn add_assign(&mut self, rhs: i32) {
+        *self.0 += rhs;
+    }
+}
+
+fn f7() {
+    let mut a = 1;
+    {
+        // `b` does not trigger unused_variables
+        let mut b = MutRef(&mut a);
+        b += 1;
+    }
+    drop(a);
+}
+
 fn main() {
 }