[rlox] Add dedicated instruction for Nil

rlox/src/bc.rs

@@ -6,6 +6,7 @@ use std::fmt;
 pub enum Op {
     Return,
     Constant { offset: usize },
+    Nil,
     Negate,
     Add,
     Subtract,
@@ -133,7 +134,7 @@ impl fmt::Debug for TraceInfo<'_> {
         }?;
 
         match op {
-            Op::Return | Op::Negate | Op::Add | Op::Subtract | Op::Multiply | Op::Divide => {
+            Op::Return | Op::Nil | Op::Negate | Op::Add | Op::Subtract | Op::Multiply | Op::Divide => {
                 write!(f, "{:?}", op)
             }
             Op::Constant { offset } => {

rlox/src/lc.rs

@@ -352,7 +352,7 @@ impl<'src> Parser<'src> {
                     ttype: TokenType::Nil,
                     span: _,
                 } => {
-                    chunk.add_constant(Value::Nil, 0);
+                    chunk.add_op(Op::Nil, 0);
                 }
                 Token {
                     ttype: TokenType::LeftParen,
@@ -497,9 +497,9 @@ mod tests {
 
         use crate::bc::Op::*;
         let expected = Chunk::new_with(
-            vec![Constant { offset: 0 }, Constant { offset: 1 }, Add],
+            vec![Nil, Nil, Add],
+            vec![],
             vec![],
-            vec![Value::Nil, Value::Nil],
         );
 
         assert!(chunk.instr_eq(&expected));

rlox/src/vm.rs

@@ -76,6 +76,7 @@ impl VM {
             match instr {
                 Op::Return => print!("{:?}", self.pop()?),
                 Op::Constant { offset } => self.push(chunk.constants[offset]),
+                Op::Nil => self.push(Value::Nil),
                 Op::Negate => {
                     let new_val = -self.pop_num()?;
                     self.push(new_val.into());
@@ -144,9 +145,9 @@ mod tests {
     #[test]
     fn runtime_type_error() {
         let chunk = Chunk::new_with(
-            vec![Op::Constant { offset: 0 }, Op::Negate],
+            vec![Op::Nil, Op::Negate],
+            vec![],
             vec![],
-            vec![Value::Nil],
         );
 
         let mut vm = VM::new();