`proc_macro::quote` cannot be made useful for rust-analyzer

[Veykril]

Macro in question: https://doc.rust-lang.org/proc_macro/macro.quote.html

What do I mean with this? Basically rust-analyzer cannot make use of the spans the macro generated, as these spans are generated and stored (via save_span) at compilation time of the macro, then loaded (via load_span) by the proc macro server when executed. rust-analyzer is not the tool that compiles the proc-macros though, so we are not the one saving any spans and as such we also can't really load them (even if we go through the artifacts produced, their representation differs from our spans). So for r-a to be able to make use of this feature (should it ever get stabilized), the implementation details would need to change in some way and/or r-a needs to be the one compiling the proc-macros somehow.

[Veykril]

On a related note, assuming wasm based proc-macros are ever to be a thing, this will run into a similar-ish problem there should they be shipped via crates-io.