feat: usable?

src/ty/common.rs

@@ -1,13 +1,24 @@
+use std::fmt::{Display, Formatter, Result as FmtResult};
 use std::ops::Deref;
 
-use ecow::EcoString;
 use derive_more::Constructor;
+use ecow::EcoString;
 
 #[derive(Clone, Debug, PartialEq, Constructor)]
 pub struct Catchable {
     msg: Option<String>,
 }
 
+impl Display for Catchable {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        if let Some(ref msg) = self.msg {
+            write!(f, "<error: {msg}>")
+        } else {
+            write!(f, "<error>")
+        }
+    }
+}
+
 #[derive(Debug, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Constructor)]
 pub struct Symbol(EcoString);
 
@@ -17,6 +28,12 @@ impl<T: Into<EcoString>> From<T> for Symbol {
     }
 }
 
+impl Display for Symbol {
+    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
+        write!(f, r#"Sym({})"#, self.0)
+    }
+}
+
 impl Deref for Symbol {
     type Target = str;
     fn deref(&self) -> &Self::Target {