fix Issue 18457 - betterC - struct destructor is always called at fun…

…ction return

src/dmd/func.d

@@ -98,8 +98,17 @@ public:
     {
         DtorExpStatement des;
         if (fd.nrvo_can && s.finalbody && (des = s.finalbody.isDtorExpStatement()) !is null &&
-            fd.nrvo_var == des.var && global.params.useExceptions && ClassDeclaration.throwable)
+            fd.nrvo_var == des.var)
         {
+            if (!(global.params.useExceptions && ClassDeclaration.throwable))
+            {
+                /* Don't need to call destructor at all, since it is nrvo
+                 */
+                replaceCurrent(s._body);
+                s._body.accept(this);
+                return;
+            }
+
             /* Normally local variable dtors are called regardless exceptions.
              * But for nrvo_var, its dtor should be called only when exception is thrown.
              *

test/runnable/betterc.d

@@ -26,6 +26,7 @@ extern (C) void main()
     test(1);
     test18472();
     testRuntimeLowerings();
+    test18457();
 }
 
 /*******************************************/
@@ -156,3 +157,31 @@ void testRuntimeLowerings()
             break;
     }
 }
+
+/**********************************************/
+// https://issues.dlang.org/show_bug.cgi?id=18457
+
+__gshared int dtor;
+
+struct S18457
+{
+    int a = 3;
+    ~this() { a = 0; ++dtor; }
+}
+
+S18457 myFunction()
+{
+    S18457 s = S18457();
+    return s;
+}
+
+void test18457()
+{
+    {
+        S18457 s = myFunction();
+        assert(s.a == 3);
+        assert(dtor == 0);
+    }
+    assert(dtor == 1);
+}
+