D-Programming-Language/dmd — pull request #2453 by 9rnsr (2013-08-07 04:57:03+00:00)
Title: Issue 10768 - DMD does not show deprecation message for missing 'override' keyword 

http://d.puremagic.com/issues/show_bug.cgi?id=10768

If a class/struct/template is not speculatively instantiated, error gagging should be ungagged temporarily during its semantic.
Use RAII idiom to do it reliably.