Even if clang never ends up supporting nested functions, it would be nice if we could detect what's going on and give an easily recognizable error message. Currently, it gives "expected ';' at end of declaration", which isn't obvious without going in and looking at the file in question.
Related: <rdar://problem/6880357> improve parse failure with nested functions and "missing }"
*** Bug 9260 has been marked as a duplicate of this bug. ***
*** Bug 5324 has been marked as a duplicate of this bug. ***
*** Bug 10885 has been marked as a duplicate of this bug. ***
Fixed in r179603