[clang] [Clang][Sema] Error message refers to `__begin1` with `constexpr` variable in range-based for loop (PR #218145)

[Akash Manna via cfe-commits]

akash-manna-sky wrote:

> LGTM, but wait a few days to see if @zygoloid has any other suggestions; if not, feel free to ping me again to merge this

Ping @Sirraide 

https://github.com/llvm/llvm-project/pull/218145