cppinsights.io shows expanded function templates as explicit specializations. It's built on LLVM, but I don't think that this tool is upstreamed.
https://cppinsights.io/lnk?code=dm9pZCBmb28oYXV0bykge30KCnZv...
https://cppinsights.io/lnk?code=dm9pZCBmb28oYXV0bykge30KCnZv...
I found the source at https://github.com/andreasfertig/cppinsights