[clang] Return available function types for BindingDecls. (PR #102196)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

Is this a bug fix? If so, do you have a test case for this?

If the change is supposed to be user or API visible, a release note explaining it would also be useful.

https://github.com/llvm/llvm-project/pull/102196