Check for mutable borrow of counter variable

src/loops.rs

@@ -351,6 +351,7 @@ fn visit_expr(&mut self, expr: &'v Expr) {
                             }
                         },
                     ExprAssign(ref lhs, _) if lhs.id == expr.id => *state = VarState::DontWarn,
+                    ExprAddrOf(mutability,_) if mutability == MutMutable => *state = VarState::DontWarn,
                     _ => ()
                 }
             }
@@ -430,6 +431,7 @@ fn visit_expr(&mut self, expr: &'v Expr) {
                         } else {
                             VarState::DontWarn
                         }},
+                    ExprAddrOf(mutability,_) if mutability == MutMutable => self.state = VarState::DontWarn,
                     _ => ()
                 }
             }

tests/compile-fail/for_loop.rs

@@ -179,4 +179,8 @@ fn main() {
     let mut _index = 1;
     if false { _index = 0 };
     for _v in &vec { _index += 1 }
+
+    let mut _index = 0;
+    { let mut _x = &mut _index; }
+    for _v in &vec { _index += 1 }
 }