[clang] [clang-tools-extra] [Clang] Use TargetInfo when deciding is an address space is compatible (PR #115777)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> Oh, you can just forward-declare `class ASTContext` at the top of that file. It's funny that that isn't already there.

Done, and a sema test.

https://github.com/llvm/llvm-project/pull/115777