The error message is correct, you have a lone ':' in that asm, and that
must be followed by asm constraints (a string literal) or be removed.
Your example doesn't contain any inline functions, so I doubt it would
have worked before the indicated commit, but that commit caused some
inline functions to be parsed and syntax analyzed when they weren't before
the commit, so invalid source (like the above when contained within an
inline function) might have been accepted before and now is diagnosed.