[PATCH] Improve error recovery around colon.

[Richard Smith]

> Fixing this case is a bit trickier because declspec is parsed with colon
> protection turned off, otherwise we cannot recover typos like:
>
>   A:B c;

With your patch, it's parsed with colon protection turned on, right? Or do we also need to add colon protection to tentative parsing of member-declarations?

If you want to detect and recover from the above case, you need more lookahead than you're currently using: you need to check if the colon is followed by *two* identifiers. If it is, you can temporarily turn off colon protection.

================
Comment at: lib/Parse/Parser.cpp:1692-1694
@@ +1691,5 @@
+///
+/// Setting NeedType influences error recovery. If it is set, parser avoids
+/// replacements ':' -> '::' if it produces non-type entity. With it we can
+/// parse correctly code like this:
+/// \code
----------------
This doesn't seem correct. Even if `A::B::C` is a type, we still should not do the recovery here, because this may still be an unnamed bitfield.

Also, I'm concerned about whether this `NeedType` thing is correct, since we use `TryAnnotateCXXScopeSpec` from tentative parsing when we don't know whether we expect a type or not.

http://reviews.llvm.org/D3653