October commit

- custom parser support and infra
- type-tagging and traits (untested)
- match expressions

src/error/runtime_error.rs

@@ -1,7 +1,7 @@
 use std::fmt::Display;
-use std::rc::Rc;
+use std::sync::Arc;
 
-use crate::foreign::ExternError;
+use crate::foreign::{ExternError, XfnResult};
 
 /// Some external event prevented the operation from succeeding
 #[derive(Clone)]
@@ -13,15 +13,15 @@ pub struct RuntimeError {
 impl RuntimeError {
   /// Construct, upcast and wrap in a Result that never succeeds for easy
   /// short-circuiting
-  pub fn fail<T>(
-    message: String,
-    operation: &'static str,
-  ) -> Result<T, Rc<dyn ExternError>> {
+  pub fn fail<T>(message: String, operation: &'static str) -> XfnResult<T> {
     Err(Self { message, operation }.into_extern())
   }
 
   /// Construct and upcast to [ExternError]
-  pub fn ext(message: String, operation: &'static str) -> Rc<dyn ExternError> {
+  pub fn ext(
+    message: String,
+    operation: &'static str,
+  ) -> Arc<dyn ExternError> {
     Self { message, operation }.into_extern()
   }
 }