Summary:
Clang performs expression based completion whenever it can't figure out
base of a member reference expression. It might be quite confusing in cases like
incomplete types. This patch disables that fallback.
Unfortunately `ParsePostfixExpressionSuffix` is quite tangled and this patch
adds more to it.
Reviewers: sammccall
Subscribers: cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D77570