feat(tazjin/rlox): Implement else clauses r/2987

Change-Id: I0bc2333c0b4dd3e2e584a90d0d15b28c48130f03
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3740
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>

1 files changed, 14 insertions, 0 deletions

diff --git a/users/tazjin/rlox/src/bytecode/compiler.rs b/users/tazjin/rlox/src/bytecode/compiler.rs
index 1b87e94a5512..3e8a80653f91 100644
--- a/users/tazjin/rlox/src/bytecode/compiler.rs
+++ b/users/tazjin/rlox/src/bytecode/compiler.rs
@@ -343,8 +343,17 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
         );
 
         let then_jump = self.emit_op(OpCode::OpJumpPlaceholder(false));
+        self.emit_op(OpCode::OpPop);
         self.statement()?;
+        let else_jump = self.emit_op(OpCode::OpJumpPlaceholder(true));
         self.patch_jump(then_jump);
+        self.emit_op(OpCode::OpPop);
+
+        if self.match_token(&TokenKind::Else) {
+            self.statement()?;
+        }
+
+        self.patch_jump(else_jump);
 
         Ok(())
     }
@@ -620,6 +629,11 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
     fn patch_jump(&mut self, idx: CodeIdx) {
         let offset = CodeOffset(self.chunk.code.len() - idx.0 - 1);
 
+        if let OpCode::OpJumpPlaceholder(true) = self.chunk.code[idx.0] {
+            self.chunk.code[idx.0] = OpCode::OpJump(offset);
+            return;
+        }
+
         if let OpCode::OpJumpPlaceholder(false) = self.chunk.code[idx.0] {
             self.chunk.code[idx.0] = OpCode::OpJumpIfFalse(offset);
             return;