That's a little different: the situation was that rms has denied GCC to provide the AST inspection features which Clang provides. This is to prevent non-free to

That's a little different: the situation was that rms has denied GCC to provide the AST inspection features which Clang provides. This is to prevent non-free tools from using GCC's core. For the same reason, It is highly unlikely that Emacs core will ever build in support for Clang. In the meantime, if you want great Clang integration, there's Rtags.