[fine] Evaluate is expressions, SO MANY BUG FIXES

fine/src/semantics.rs

@@ -123,6 +123,7 @@ pub enum Type {
     // TODO: Numeric literals should be implicitly convertable, unlike other
     //       types. Maybe just "numeric literal" type?
     F64,
+    I64,
     String,
     Bool,
 
@@ -172,6 +173,7 @@ impl fmt::Display for Type {
             Assignment(_) => write!(f, "assignment"),
             Nothing => write!(f, "()"),
             F64 => write!(f, "f64"),
+            I64 => write!(f, "i64"),
             String => write!(f, "string"),
             Bool => write!(f, "bool"),
             Function(args, ret) => {
@@ -831,6 +833,9 @@ impl<'a> Semantics<'a> {
             return Environment::error();
         };
 
+        // TODO: This binding should be un-assignable! Don't assign to this!
+        //       (UNLESS VERY SPECIFIC CIRCUMSTANCES; WHICH ARE COMPLEX)
+
         let mut env = Environment::new(Some(parent), Location::Local);
         env.insert(variable, type_expr);
         return EnvironmentRef::new(env);