[clang] [clang-repl] Ensure clang-repl accepts all C keywords supported in all language models (PR #142749)

[Anutosh Bhat via cfe-commits]

anutosh491 wrote:

The error comes from here to be precise
https://github.com/llvm/llvm-project/blob/41841e625db8d14d6701e7cb211b2fcab6a32a50/clang/lib/Parse/Parser.cpp#L1026-L1028

`IsDeclarationStatement` should be true but return false enabling a faulty call to `ParseTopLevelStmtDecl`

https://github.com/llvm/llvm-project/pull/142749