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, 14 insertions, 15 deletions

diff --git a/crates/ra_hir_expand/src/proc_macro.rs b/crates/ra_hir_expand/src/proc_macro.rs
index a8dee2052..4d270e0de 100644
--- a/crates/ra_hir_expand/src/proc_macro.rs
+++ b/crates/ra_hir_expand/src/proc_macro.rs
@@ -1,33 +1,32 @@
 //! Proc Macro Expander stub
 
-use crate::{db::AstDatabase, LazyMacroId, MacroCallKind, MacroCallLoc};
-use ra_db::CrateId;
+use crate::{db::AstDatabase, LazyMacroId};
+use ra_db::{CrateId, ProcMacroId};
 
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
 pub struct ProcMacroExpander {
     krate: CrateId,
+    proc_macro_id: ProcMacroId,
 }
 
 impl ProcMacroExpander {
-    pub fn new(krate: CrateId) -> ProcMacroExpander {
-        ProcMacroExpander { krate }
+    pub fn new(krate: CrateId, proc_macro_id: ProcMacroId) -> ProcMacroExpander {
+        ProcMacroExpander { krate, proc_macro_id }
     }
 
     pub fn expand(
         &self,
         db: &dyn AstDatabase,
-        id: LazyMacroId,
-        _tt: &tt::Subtree,
+        _id: LazyMacroId,
+        tt: &tt::Subtree,
     ) -> Result<tt::Subtree, mbe::ExpandError> {
-        let loc: MacroCallLoc = db.lookup_intern_macro(id);
-        let name = match loc.kind {
-            MacroCallKind::FnLike(_) => return Err(mbe::ExpandError::ConversionError),
-            MacroCallKind::Attr(_, name) => name,
-        };
+        let krate_graph = db.crate_graph();
+        let proc_macro = krate_graph[self.krate]
+            .proc_macro
+            .get(self.proc_macro_id.0 as usize)
+            .clone()
+            .ok_or_else(|| mbe::ExpandError::ConversionError)?;
 
-        log::debug!("Proc-macro-expanding name = {}", name);
-
-        // Return nothing for now
-        return Ok(tt::Subtree::default());
+        proc_macro.expander.expand(&tt, None).map_err(mbe::ExpandError::from)
     }
 }