October commit

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

src/systems/stl/panic.rs

@@ -1,5 +1,5 @@
 use std::fmt::Display;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use crate::foreign::{xfn_1ary, ExternError, XfnResult};
 use crate::interpreted::Clause;
@@ -7,7 +7,8 @@ use crate::{ConstTree, Interner, OrcString};
 
 /// An unrecoverable error in Orchid land. Because Orchid is lazy, this only
 /// invalidates expressions that reference the one that generated it.
-pub struct OrchidPanic(Rc<String>);
+#[derive(Clone)]
+pub struct OrchidPanic(Arc<String>);
 
 impl Display for OrchidPanic {
   fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
@@ -20,7 +21,7 @@ impl ExternError for OrchidPanic {}
 /// Takes a message, returns an [ExternError] unconditionally.
 pub fn orc_panic(msg: OrcString) -> XfnResult<Clause> {
   // any return value would work, but Clause is the simplest
-  Err(OrchidPanic(Rc::new(msg.get_string())).into_extern())
+  Err(OrchidPanic(Arc::new(msg.get_string())).into_extern())
 }
 
 pub fn panic(i: &Interner) -> ConstTree {