[clang] [clang][dataflow] Clear `ExprToLoc` and `ExprToVal` at the start of a block. (PR #72985)

[via cfe-commits]

martinboehme wrote:

The clang-format check is failing on code that this PR does not touch. To avoid touching unrelated code, I suggest not fixing the issue reported by clang-format.

https://github.com/llvm/llvm-project/pull/72985