Converted Interner to work with Rc-s

- Interner no longer contains unsafe code
- Tokens now hold a reference to the value they represent directly

This will enable many future improvements

src/interpreter/apply.rs

@@ -108,7 +108,7 @@ pub fn apply(
       if let Some(sym) = ctx.symbols.get(name) {
         Ok((Clause::Apply { f: sym.clone(), x }, (ctx.gas, false)))
       } else {
-        Err(RuntimeError::MissingSymbol(*name, loc.clone()))
+        Err(RuntimeError::MissingSymbol(name.clone(), loc.clone()))
       },
     Clause::P(Primitive::Atom(atom)) => {
       // take a step in expanding atom

src/interpreter/error.rs

@@ -1,7 +1,7 @@
+use std::fmt::Display;
 use std::rc::Rc;
 
 use crate::foreign::ExternError;
-use crate::interner::InternedDisplay;
 use crate::representations::interpreted::ExprInst;
 use crate::{Location, Sym};
 
@@ -22,12 +22,8 @@ impl From<Rc<dyn ExternError>> for RuntimeError {
   }
 }
 
-impl InternedDisplay for RuntimeError {
-  fn fmt_i(
-    &self,
-    f: &mut std::fmt::Formatter<'_>,
-    i: &crate::Interner,
-  ) -> std::fmt::Result {
+impl Display for RuntimeError {
+  fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
     match self {
       Self::Extern(e) => write!(f, "Error in external function: {e}"),
       Self::NonFunctionApplication(expr) => {
@@ -37,7 +33,7 @@ impl InternedDisplay for RuntimeError {
         write!(
           f,
           "{}, called at {loc} is not loaded",
-          i.extern_vec(*sym).join("::")
+          sym.extern_vec().join("::")
         )
       },
     }

src/interpreter/run.rs

@@ -30,8 +30,9 @@ pub fn run(expr: ExprInst, mut ctx: Context) -> Result<Return, RuntimeError> {
             i = clause.clone();
           },
           Clause::Constant(c) => {
-            let symval = (ctx.symbols.get(c))
-              .ok_or_else(|| RuntimeError::MissingSymbol(*c, loc.clone()))?;
+            let symval = (ctx.symbols.get(c)).ok_or_else(|| {
+              RuntimeError::MissingSymbol(c.clone(), loc.clone())
+            })?;
             ctx.gas = ctx.gas.map(|g| g - 1); // cost of lookup
             i = symval.expr().clause.clone();
           },