src/object.d

@@ -1658,6 +1658,7 @@ class Throwable : Object
         sink("@"); sink(file);
         sink("("); sink(sizeToTempString(line, tmpBuff, 10)); sink(")");
 
+        auto msg = message();
         if (msg.length)
         {
             sink(": "); sink(msg);
@@ -1678,6 +1679,19 @@ class Throwable : Object
             }
         }
     }
+
+    /**
+     * Get the message describing the error.
+     * Base behavior is to return the `Throwable.msg` field.
+     * Override to return some other error message.
+     *
+     * Returns:
+     *  message
+     */
+    const(char)[] message() const
+    {
+        return msg;
+    }
 }