Optional methods use ? tokens like this:
interface X { y?(): z; }
It seems easiest to detect and disambiguate these from ternary
expressions by checking if the code is in a declaration context. Turns
out that that didn't quite work properly for interfaces in Java and JS,
and for JS file root contexts.
Patch by Martin Probst, thank you.
llvm-svn: 236488
9326f91922