deal with unknown types at the syntax phase

src/syntax/eval.rs

@@ -45,6 +45,11 @@ impl Program {
                     let value = env
                         .get(&name.clone().intern())
                         .ok_or_else(|| EvalError::LookupFailed(loc.clone(), name.name.clone()))?;
+                    let value = if let Value::Number(x) = value {
+                        Value::U64(*x)
+                    } else {
+                        value.clone()
+                    };
                     let line = format!("{} = {}\n", name, value);
                     stdout.push_str(&line);
                     last_result = Value::Void;
@@ -64,7 +69,7 @@ impl Expression {
         match self {
             Expression::Value(_, v) => match v {
                 super::Value::Number(_, ty, v) => match ty {
-                    None => Ok(Value::U64(*v)),
+                    None => Ok(Value::Number(*v)),
                     // FIXME: make these types validate their input size
                     Some(ConstantType::Void) => Ok(Value::Void),
                     Some(ConstantType::I8) => Ok(Value::I8(*v as i8)),