feat(tazjin/rlox): Implement global variable access r/2274

This also includes a fix for an issue where the identifiers of
variables were pushed onto the stack, which is incorrect.

Change-Id: Id89b388268efad295f29978d767aa4b33c4ded14
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2594
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

1 files changed, 25 insertions, 5 deletions

diff --git a/users/tazjin/rlox/src/bytecode/compiler.rs b/users/tazjin/rlox/src/bytecode/compiler.rs
index f993e35557ad..b8b91667d3fa 100644
--- a/users/tazjin/rlox/src/bytecode/compiler.rs
+++ b/users/tazjin/rlox/src/bytecode/compiler.rs
@@ -145,6 +145,10 @@ fn rule_for<T: Iterator<Item = Token>>(token: &TokenKind) -> ParseRule<T> {
             ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison)
         }
 
+        TokenKind::Identifier(_) => {
+            ParseRule::new(Some(Compiler::variable), None, Precedence::None)
+        }
+
         TokenKind::String(_) => {
             ParseRule::new(Some(Compiler::string), None, Precedence::None)
         }
@@ -238,7 +242,7 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
 
     fn number(&mut self) -> LoxResult<()> {
         if let TokenKind::Number(num) = self.previous().kind {
-            self.emit_constant(Value::Number(num));
+            self.emit_constant(Value::Number(num), true);
             return Ok(());
         }
 
@@ -330,11 +334,23 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
         };
 
         let id = self.strings.intern(val);
-        self.emit_constant(Value::String(id.into()));
+        self.emit_constant(Value::String(id.into()), true);
+
+        Ok(())
+    }
 
+    fn named_variable(&mut self) -> LoxResult<()> {
+        let ident = self.identifier_str(Self::previous)?;
+        let constant_id =
+            self.emit_constant(Value::String(ident.into()), false);
+        self.emit_op(OpCode::OpGetGlobal(constant_id));
         Ok(())
     }
 
+    fn variable(&mut self) -> LoxResult<()> {
+        self.named_variable()
+    }
+
     fn parse_precedence(&mut self, precedence: Precedence) -> LoxResult<()> {
         self.advance();
         let rule: ParseRule<T> = rule_for(&self.previous().kind);
@@ -385,7 +401,7 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
         );
 
         let id = self.identifier_str(Self::previous)?;
-        Ok(self.emit_constant(Value::String(id.into())))
+        Ok(self.emit_constant(Value::String(id.into()), false))
     }
 
     fn current_chunk(&mut self) -> &mut Chunk {
@@ -409,9 +425,13 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
         self.current_chunk().add_op(op, line);
     }
 
-    fn emit_constant(&mut self, val: Value) -> usize {
+    fn emit_constant(&mut self, val: Value, with_op: bool) -> usize {
         let idx = self.chunk.add_constant(val);
-        self.emit_op(OpCode::OpConstant(idx));
+
+        if with_op {
+            self.emit_op(OpCode::OpConstant(idx));
+        }
+
         idx
     }