Function get_proc_macro_info 

pub fn get_proc_macro_info<'p>(
    target: &Target,
    path: &'p Path,
    metadata_loader: &dyn MetadataLoader,
    cfg_version: &'static str,
) -> Result<Vec<ProcMacroKind>, MetadataError<'p>>

A function to get information about all macros inside a proc-macro crate.

Used by rust-analyzer-proc-macro-srv.