conlang: Unify binding operations!

This breaks out the pattern matching/unification algorithm from cl-interpret/interpret.rs to cl-interpret/pattern.rs

TODO: pattern destructuring in const, static :^)

compiler/cl-ast/src/ast_visitor/fold.rs

@@ -111,8 +111,8 @@ pub trait Fold {
         }
     }
     fn fold_param(&mut self, p: Param) -> Param {
-        let Param { mutability, name } = p;
-        Param { mutability: self.fold_mutability(mutability), name: self.fold_sym(name) }
+        let Param { mutability, bind } = p;
+        Param { mutability: self.fold_mutability(mutability), bind: self.fold_pattern(bind) }
     }
     fn fold_struct(&mut self, s: Struct) -> Struct {
         let Struct { name, kind } = s;

compiler/cl-ast/src/ast_visitor/visit.rs

@@ -89,9 +89,9 @@ pub trait Visit<'a>: Sized {
         }
     }
     fn visit_param(&mut self, p: &'a Param) {
-        let Param { mutability, name } = p;
+        let Param { mutability, bind } = p;
         self.visit_mutability(mutability);
-        self.visit_sym(name);
+        self.visit_pattern(bind);
     }
     fn visit_struct(&mut self, s: &'a Struct) {
         let Struct { name, kind } = s;