Merge pull request #363 from 9rnsr/fix9052

Issue 9052 - [2.061 alpha] AA.length in a const context tries to call opAssign + no error line number

src/object.di

@@ -398,6 +398,9 @@ private:
         size_t hash;
         Key key;
         Value value;
+
+        // Stop creating built-in opAssign
+        @disable void opAssign(Slot);
     }
 
     struct Hashtable

src/object_.d

@@ -2118,6 +2118,9 @@ private:
         size_t hash;
         Key key;
         Value value;
+
+        // Stop creating built-in opAssign
+        @disable void opAssign(Slot);
     }
 
     struct Hashtable
@@ -2312,6 +2315,20 @@ unittest
     assert(a == b);
 }
 
+unittest
+{
+    // test for bug 9052
+    static struct Json {
+        Json[string] aa;
+        void opAssign(Json) {}
+        size_t length() const { return aa.length; }
+        // This length() instantiates AssociativeArray!(string, const(Json)) to call AA.length(), and
+        // inside ref Slot opAssign(Slot p); (which is automatically generated by compiler in Slot),
+        // this.value = p.value would actually fail, because both side types of the assignment
+        // are const(Json).
+    }
+}
+
 // Scheduled for deprecation in December 2012.
 // Please use destroy instead of clear.
 alias destroy clear;