Merge #3738

3738: Implement ra_proc_macro client logic r=matklad a=edwin0cheng

This PR add the actual client logic for `ra_proc_macro` crate:

1. Define all necessary rpc serialization data structure, which include `ra_tt` related data and some task messages. Although adding `Serialize` and `Deserialize` trait to ra_tt directly seem to be much easier,   we deliberately duplicate the `ra_tt` struct with `#[serde(with = "XXDef")]` for separation of  code responsibility. 
2. Define a simplified version of lsp base protocol for rpc, which basically copy from lsp-server code base. 
3. Implement the actual `IO` for the client side progress spawning and message passing.

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

1 files changed, 6 insertions, 1 deletions

diff --git a/crates/ra_tt/src/lib.rs b/crates/ra_tt/src/lib.rs
index 1015ce0a6..bd484aa30 100644
--- a/crates/ra_tt/src/lib.rs
+++ b/crates/ra_tt/src/lib.rs
@@ -189,7 +189,12 @@ impl Subtree {
 pub mod buffer;
 
 #[derive(Debug, PartialEq, Eq)]
-pub enum ExpansionError {}
+pub enum ExpansionError {
+    IOError(String),
+    JsonError(String),
+    Unknown(String),
+    ExpansionError(String),
+}
 
 pub trait TokenExpander: Debug + Send + Sync + RefUnwindSafe {
     fn expand(&self, subtree: &Subtree, attrs: Option<&Subtree>)