6901: Temp fixes panic caused by no ast for proc-macro r=maklad a=edwin0cheng
There are some panic when hover/goto definition for proc-macro. It is because in current design, we don't have `ast-node` for proc-macro and then it trigger [this](479d1f7eec/crates/hir/src/has_source.rs (L116)) line to panic.
This PR is a temp fix for all of these similar to bd4c352831/crates/completion/src/render/macro_.rs (L42)
Co-authored-by: Edwin Cheng <edwin0cheng@gmail.com>
We used to have `Def` suffix for all symbols, but we moved off from
that. `FunctionDef` isn't better than `Function`. Looks like we've
forgot to change `Impl` though!