From 6e79126a7df44075b22d382e44540d78e4cb1909 Mon Sep 17 00:00:00 2001
From: Lai-YT <381xvmvbib@gmail.com>
Date: Mon, 10 Jun 2024 16:12:01 +0800
Subject: [PATCH] Check type of comma operator

---
 src/type_checker.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/type_checker.cpp b/src/type_checker.cpp
index 04c40d5e..a2e9a282 100644
--- a/src/type_checker.cpp
+++ b/src/type_checker.cpp
@@ -507,6 +507,15 @@ void TypeChecker::Visit(UnaryExprNode& unary_expr) {
 void TypeChecker::Visit(BinaryExprNode& bin_expr) {
   bin_expr.lhs->Accept(*this);
   bin_expr.rhs->Accept(*this);
+
+  // NOTE: The left operand of a comma operator is evaluated as a void
+  // expression; there is a sequence point after its evaluation. Then the right
+  // operand is evaluated; the result has its type and value.
+  if (bin_expr.op == BinaryOperator::kComma) {
+    bin_expr.type = bin_expr.rhs->type->Clone();
+    return;
+  }
+
   if (!bin_expr.lhs->type->IsEqual(*bin_expr.rhs->type)) {
     // TODO: invalid operands to binary +
   } else {