5 files changed, 80 insertions, 15 deletions
diff --git a/users/tazjin/rlox/src/bytecode/compiler.rs b/users/tazjin/rlox/src/bytecode/compiler.rs
index f2fdeb0e9feb..f993e35557ad 100644
--- a/users/tazjin/rlox/src/bytecode/compiler.rs
+++ b/users/tazjin/rlox/src/bytecode/compiler.rs
@@ -1,6 +1,6 @@
 use super::chunk::Chunk;
 use super::errors::{Error, ErrorKind, LoxResult};
-use super::interner::Interner;
+use super::interner::{InternedStr, Interner};
 use super::opcode::OpCode;
 use super::value::Value;
 use crate::scanner::{self, Token, TokenKind};
@@ -182,8 +182,30 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
         self.parse_precedence(Precedence::Assignment)
     }
 
+    fn var_declaration(&mut self) -> LoxResult<()> {
+        let global = self.parse_variable()?;
+
+        if self.match_token(&TokenKind::Equal) {
+            self.expression()?;
+        } else {
+            self.emit_op(OpCode::OpNil);
+        }
+
+        self.expect_semicolon("expect ';' after variable declaration")?;
+        self.define_variable(global)
+    }
+
+    fn define_variable(&mut self, var: usize) -> LoxResult<()> {
+        self.emit_op(OpCode::OpDefineGlobal(var));
+        Ok(())
+    }
+
     fn declaration(&mut self) -> LoxResult<()> {
-        self.statement()?;
+        if self.match_token(&TokenKind::Var) {
+            self.var_declaration()?;
+        } else {
+            self.statement()?;
+        }
 
         if self.panic {
             self.synchronise();
@@ -202,22 +224,14 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
 
     fn print_statement(&mut self) -> LoxResult<()> {
         self.expression()?;
-        consume!(
-            self,
-            TokenKind::Semicolon,
-            ErrorKind::ExpectedToken("Expected ';' after value")
-        );
+        self.expect_semicolon("expect ';' after print statement")?;
         self.emit_op(OpCode::OpPrint);
         Ok(())
     }
 
     fn expression_statement(&mut self) -> LoxResult<()> {
         self.expression()?;
-        consume!(
-            self,
-            TokenKind::Semicolon,
-            ErrorKind::ExpectedToken("Expected ';' after expression")
-        );
+        self.expect_semicolon("expect ';' after expression")?;
         self.emit_op(OpCode::OpPop);
         Ok(())
     }
@@ -346,6 +360,34 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
         Ok(())
     }
 
+    fn identifier_str(
+        &mut self,
+        token_fn: fn(&Self) -> &Token,
+    ) -> LoxResult<InternedStr> {
+        let ident = match &token_fn(self).kind {
+            TokenKind::Identifier(ident) => ident.to_string(),
+            _ => {
+                return Err(Error {
+                    line: self.current().line,
+                    kind: ErrorKind::ExpectedToken("Expected identifier"),
+                })
+            }
+        };
+
+        Ok(self.strings.intern(ident))
+    }
+
+    fn parse_variable(&mut self) -> LoxResult<usize> {
+        consume!(
+            self,
+            TokenKind::Identifier(_),
+            ErrorKind::ExpectedToken("expected identifier")
+        );
+
+        let id = self.identifier_str(Self::previous)?;
+        Ok(self.emit_constant(Value::String(id.into())))
+    }
+
     fn current_chunk(&mut self) -> &mut Chunk {
         &mut self.chunk
     }
@@ -367,9 +409,10 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
         self.current_chunk().add_op(op, line);
     }
 
-    fn emit_constant(&mut self, val: Value) {
+    fn emit_constant(&mut self, val: Value) -> usize {
         let idx = self.chunk.add_constant(val);
         self.emit_op(OpCode::OpConstant(idx));
+        idx
     }
 
     fn previous(&self) -> &Token {
@@ -430,6 +473,11 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
             }
         }
     }
+
+    fn expect_semicolon(&mut self, msg: &'static str) -> LoxResult<()> {
+        consume!(self, TokenKind::Semicolon, ErrorKind::ExpectedToken(msg));
+        Ok(())
+    }
 }
 
 pub fn compile(code: &str) -> Result<(Interner, Chunk), Vec<Error>> {
diff --git a/users/tazjin/rlox/src/bytecode/interner/mod.rs b/users/tazjin/rlox/src/bytecode/interner/mod.rs
index f5f695904e85..1da1a24b2c5f 100644
--- a/users/tazjin/rlox/src/bytecode/interner/mod.rs
+++ b/users/tazjin/rlox/src/bytecode/interner/mod.rs
@@ -11,7 +11,7 @@ use std::collections::HashMap;
 #[cfg(test)]
 mod tests;
 
-#[derive(Clone, Copy, Debug, PartialEq, Hash)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub struct InternedStr {
     id: usize,
 }
diff --git a/users/tazjin/rlox/src/bytecode/opcode.rs b/users/tazjin/rlox/src/bytecode/opcode.rs
index 37466b30564c..25ce03c3c182 100644
--- a/users/tazjin/rlox/src/bytecode/opcode.rs
+++ b/users/tazjin/rlox/src/bytecode/opcode.rs
@@ -29,4 +29,7 @@ pub enum OpCode {
     // Built in operations
     OpPrint,
     OpPop,
+
+    // Variable definitions
+    OpDefineGlobal(usize),
 }
diff --git a/users/tazjin/rlox/src/bytecode/value.rs b/users/tazjin/rlox/src/bytecode/value.rs
index 19a4dcc92eac..4170efadf8fe 100644
--- a/users/tazjin/rlox/src/bytecode/value.rs
+++ b/users/tazjin/rlox/src/bytecode/value.rs
@@ -8,7 +8,7 @@ pub enum Value {
     String(LoxString),
 }
 
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub enum LoxString {
     Heap(String),
     Interned(InternedStr),
diff --git a/users/tazjin/rlox/src/bytecode/vm.rs b/users/tazjin/rlox/src/bytecode/vm.rs
index 9161bdfe53b8..53431a083785 100644
--- a/users/tazjin/rlox/src/bytecode/vm.rs
+++ b/users/tazjin/rlox/src/bytecode/vm.rs
@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
 use super::chunk;
 use super::errors::*;
 use super::interner::Interner;
@@ -14,6 +16,8 @@ pub struct VM {
     stack: Vec<Value>,
     strings: Interner,
 
+    globals: HashMap<LoxString, Value>,
+
     // Operations that consume values from the stack without pushing
     // anything leave their last value in this slot, which makes it
     // possible to return values from interpreters that ran code which
@@ -157,6 +161,15 @@ impl VM {
                 OpCode::OpPop => {
                     self.last_drop = Some(self.pop());
                 }
+
+                OpCode::OpDefineGlobal(name_idx) => {
+                    let name = self.chunk.constant(*name_idx);
+                    with_type!(self, name, Value::String(name), {
+                        let name = name.clone();
+                        let val = self.pop();
+                        self.globals.insert(name, val);
+                    });
+                }
             }
 
             #[cfg(feature = "disassemble")]
@@ -197,6 +210,7 @@ pub fn interpret(strings: Interner, chunk: chunk::Chunk) -> LoxResult<Value> {
     let mut vm = VM {
         chunk,
         strings,
+        globals: HashMap::new(),
         ip: 0,
         stack: vec![],
         last_drop: None,