OpenCL has a reserved operator (^^), the use of which was diagnosed as
an error (735c6cdebdcd4292928079cb18a90f0dd5cd65fb). However, OpenCL
also encourages working with the blocks language extension. This token
has a parsing ambiguity as a result. Consider:
unsigned x=0;
unsigned y=x^^{return 0;}();
This should result in y holding the value zero (0^0) through an
immediately invoked block call as the right-hand side of the xor
operator. However, it causes errors instead because of this reserved
token: https://godbolt.org/z/navf7jTv1
This token is still reserved in OpenCL 3.0, so we still wish to issue a
diagnostic for its use. However, we do not need to create a token for an
extension point that's been unused for about a decade. So this patch
moves the diagnostic from a parsing diagnostic to a lexing diagnostic
and no longer forms a single token. The diagnostic behavior is slightly
worse as a result, but still seems acceptable.
Part of the reason this is coming up is because WG21 is considering
using ^^ as a token for reflection, so this token may come back in the
future.
Check flags always enabled or disabled code blocks in preprocessor '#if'
conditions, such as '#if 0' and '#if 1' etc.
Reviewed By: carlosgalvezp
Differential Revision: https://reviews.llvm.org/D145617
