Generate a temporary for assign_ops. Issue rust-lang#2581

Author: eholk

src/rustc/middle/trans/base.rs

@@ -1439,6 +1439,7 @@ fn copy_val_no_check(bcx: block, action: copy_action, dst: ValueRef,
 // doesn't need to be dropped. (Issue #839)
 fn move_val(cx: block, action: copy_action, dst: ValueRef,
             src: lval_result, t: ty::t) -> block {
+    assert !cx.terminated;
     let _icx = cx.insn_ctxt("move_val");
     let mut src_val = src.val;
     let tcx = cx.tcx();
@@ -1721,15 +1722,24 @@ fn trans_assign_op(bcx: block, ex: @ast::expr, op: ast::binop,
       some(origin) {
         let callee_id = ast_util::op_expr_callee_id(ex);
         let fty = node_id_type(bcx, callee_id);
-        ret trans_call_inner(
+
+        let dty = expr_ty(bcx, dst);
+        let target = alloc_ty(bcx, dty);
+
+        let bcx = trans_call_inner(
             bcx, ex.info(), fty,
             expr_ty(bcx, ex),
             {|bcx|
                 // FIXME provide the already-computed address, not the expr
                 // #2528
                 impl::trans_method_callee(bcx, callee_id, dst, origin)
             },
-            arg_exprs([src]), save_in(lhs_res.val));
+            arg_exprs([src]), save_in(target));
+
+        ret move_val(bcx, DROP_EXISTING, lhs_res.val,
+                     // FIXME: should kind be owned?
+                     {bcx: bcx, val: target, kind: owned},
+                     dty);
       }
       _ {}
     }

src/test/run-pass/operator-overloading-leaks.rs

@@ -0,0 +1,74 @@
+// The cases commented as "Leaks" need to not leak. Issue #2581
+
+impl methods<T: copy> for [T] {
+    fn -(x: [T]/&) -> [T] {
+        [x[0], x[0], x[0]]
+    }
+
+    fn foo(x: [T]/&) -> [T] {
+        [x[0], x[0], x[0]]
+    }
+}
+
+impl methods<T: copy> for ~T {
+    fn +(rhs: ~T) -> ~T {
+        rhs
+    }
+}
+
+impl methods for ~int {
+    fn -(rhs: ~int) -> ~int {
+        ~(*self - *rhs)
+    }
+}
+
+impl methods for @int {
+    fn +(rhs: @int) -> @int {
+        @(*self + *rhs)
+    }
+}
+
+fn main() {
+    // leaks
+    let mut bar = [1, 2, 3];
+    bar -= [3, 2, 1];
+    bar -= [4, 5, 6];
+    
+    io::println(#fmt("%?", bar));
+
+    // okay
+    let mut bar = [1, 2, 3];
+    bar = bar.foo([3, 2, 1]);
+    bar = bar.foo([4, 5, 6]);
+
+    io::println(#fmt("%?", bar));
+
+    // okay
+    let mut bar = [1, 2, 3];
+    bar = bar - [3, 2, 1];
+    bar = bar - [4, 5, 6];
+
+    io::println(#fmt("%?", bar));
+
+    // Leaks
+    let mut bar = ~1;
+    bar += ~2;
+    bar += ~3;
+    
+    io:: println(#fmt("%?", bar));
+
+    // Leaks
+    let mut bar = ~1;
+    bar -= ~2;
+    bar -= ~3;
+    
+    io:: println(#fmt("%?", bar));
+
+    // Leaks
+    let mut bar = @1;
+    bar += @2;
+    bar += @3;
+    
+    io:: println(#fmt("%?", bar));
+
+}