From 6c4d5164d9d1c6751f2c63612ad5f68f1eef3a1b Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Tue, 8 Dec 2020 19:43:58 +0100
Subject: Better error when a proc macro panics

---
 crates/proc_macro_srv/src/lib.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/crates/proc_macro_srv/src/lib.rs b/crates/proc_macro_srv/src/lib.rs
index 6e890f8e2..9cca96994 100644
--- a/crates/proc_macro_srv/src/lib.rs
+++ b/crates/proc_macro_srv/src/lib.rs
@@ -40,7 +40,8 @@ impl ProcMacroSrv {
         match expander.expand(&task.macro_name, &task.macro_body, task.attributes.as_ref()) {
             Ok(expansion) => Ok(ExpansionResult { expansion }),
             Err(msg) => {
-                Err(format!("Cannot perform expansion for {}: error {:?}", &task.macro_name, msg))
+                let msg = msg.as_str().unwrap_or("<unknown error>");
+                Err(format!("proc-macro panicked: {}", msg))
             }
         }
     }
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