GitHub search breaks on really simple things, too:
- Queries <= 3 characters in length
- Certain common characters are totally not supported in queries - quotes, etc.
- Forks cannot be searched.
I always just clone and use a proper search tool if I know what I am looking for is in a specific codebase.
Though I've always found GitHub's code search to be less than useful in general. I think it doesn't really make sense to not have overloading because GitHub doesn't support semantic indexing in 2015, especially since you can easily just not use GitHub for code search.