Merge #3727

3727: Introduce ra_proc_macro r=matklad a=edwin0cheng

This PR implemented:

1.  Reading dylib path of proc-macro crate from cargo check , similar to how `OUTDIR` is obtained.
2.  Added a new crate `ra_proc_macro` and implement the foot-work for reading result from external proc-macro expander. 
3. Added a struct `ProcMacroClient` , which will be responsible to the client side communication to the External process.



Co-authored-by: Edwin Cheng <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/crates/ra_mbe/src/lib.rs b/crates/ra_mbe/src/lib.rs
index 6a9037bfc..535b7daa0 100644
--- a/crates/ra_mbe/src/lib.rs
+++ b/crates/ra_mbe/src/lib.rs
@@ -28,6 +28,13 @@ pub enum ExpandError {
     BindingError(String),
     ConversionError,
     InvalidRepeat,
+    ProcMacroError(tt::ExpansionError),
+}
+
+impl From<tt::ExpansionError> for ExpandError {
+    fn from(it: tt::ExpansionError) -> Self {
+        ExpandError::ProcMacroError(it)
+    }
 }
 
 pub use crate::syntax_bridge::{