From 2f8c46f0a5abc92a8adebb7b7134a53b30e51135 Mon Sep 17 00:00:00 2001
From: Jeff <dev@jeffa.io>
Date: Tue, 17 Sep 2024 23:06:58 -0400
Subject: [PATCH] Implement closing for lists

---
 dust-lang/src/instruction.rs | 24 +++++++++++++-----------
 dust-lang/src/parser/mod.rs  |  9 +++++++++
 dust-lang/src/vm.rs          | 17 ++++++++++++++---
 3 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/dust-lang/src/instruction.rs b/dust-lang/src/instruction.rs
index 6c29268..a5ce850 100644
--- a/dust-lang/src/instruction.rs
+++ b/dust-lang/src/instruction.rs
@@ -15,10 +15,11 @@ impl Instruction {
         instruction
     }
 
-    pub fn close(to_register: u8) -> Instruction {
+    pub fn close(from_register: u8, to_register: u8) -> Instruction {
         let mut instruction = Instruction(Operation::Close as u32);
 
-        instruction.set_destination(to_register);
+        instruction.set_first_argument(from_register);
+        instruction.set_second_argument(to_register);
 
         instruction
     }
@@ -243,7 +244,12 @@ impl Instruction {
             Operation::Move => {
                 format!("R({}) = R({})", self.destination(), self.first_argument())
             }
-            Operation::Close => format!("R({})", self.destination()),
+            Operation::Close => {
+                let from_register = self.first_argument();
+                let to_register = self.second_argument().saturating_sub(1);
+
+                format!("R({from_register})..=R({to_register})")
+            }
             Operation::LoadConstant => {
                 let constant_index = self.first_argument();
 
@@ -274,7 +280,7 @@ impl Instruction {
                 let last_index = destination - 1;
 
                 format!(
-                    "R({}) = [R({})..R({})]",
+                    "R({}) = [R({})..=R({})]",
                     destination, first_index, last_index
                 )
             }
@@ -556,15 +562,11 @@ mod tests {
 
     #[test]
     fn close() {
-        let mut instruction = Instruction::close(1);
-
-        instruction.set_first_argument_to_constant();
-        instruction.set_second_argument_to_constant();
+        let instruction = Instruction::close(1, 2);
 
         assert_eq!(instruction.operation(), Operation::Close);
-        assert_eq!(instruction.destination(), 1);
-        assert!(instruction.first_argument_is_constant());
-        assert!(instruction.second_argument_is_constant());
+        assert_eq!(instruction.first_argument(), 1);
+        assert_eq!(instruction.second_argument(), 2);
     }
 
     #[test]
diff --git a/dust-lang/src/parser/mod.rs b/dust-lang/src/parser/mod.rs
index 1e495a8..0d4da5e 100644
--- a/dust-lang/src/parser/mod.rs
+++ b/dust-lang/src/parser/mod.rs
@@ -485,8 +485,17 @@ impl<'src> Parser<'src> {
         let mut length = 0;
 
         while !self.allow(TokenKind::RightSquareBrace)? && !self.is_eof() {
+            let next_register = self.current_register;
+
             self.parse(Precedence::Assignment)?; // Do not allow assignment
 
+            if next_register != self.current_register - 1 {
+                self.emit_instruction(
+                    Instruction::close(next_register, self.current_register - 1),
+                    self.current_position,
+                );
+            }
+
             length += 1;
 
             if !self.allow(TokenKind::Comma)? {
diff --git a/dust-lang/src/vm.rs b/dust-lang/src/vm.rs
index 95c261b..b71c86d 100644
--- a/dust-lang/src/vm.rs
+++ b/dust-lang/src/vm.rs
@@ -66,7 +66,14 @@ impl Vm {
 
                     self.insert(value, to, position)?;
                 }
-                Operation::Close => todo!(),
+                Operation::Close => {
+                    let from = instruction.first_argument();
+                    let to = instruction.second_argument();
+
+                    for register_index in from..to {
+                        self.register_stack[register_index as usize] = None;
+                    }
+                }
                 Operation::LoadConstant => {
                     let to_register = instruction.destination();
                     let from_constant = instruction.first_argument();
@@ -77,13 +84,17 @@ impl Vm {
                 Operation::LoadList => {
                     let to_register = instruction.destination();
                     let length = instruction.first_argument();
-                    let first_register = to_register - length;
+                    let first_register = to_register - length - 1;
                     let last_register = to_register - 1;
 
                     let mut list = Vec::with_capacity(length as usize);
 
                     for register_index in first_register..=last_register {
-                        let value = self.clone(register_index, position)?;
+                        let value = match self.clone(register_index, position) {
+                            Ok(value) => value,
+                            Err(VmError::EmptyRegister { .. }) => continue,
+                            Err(error) => return Err(error),
+                        };
 
                         list.push(value);
                     }