From 278c7dd751bb968ffbe58d9e57e412a4fb692680 Mon Sep 17 00:00:00 2001
From: mo <mocompute@outlook.com>
Date: Wed, 2 Sep 2026 13:01:39 +1200
Subject: [PATCH] Detect and error on chained offset_of expressions.

Fixes #5851.

This disallows expressions like `offset_of(a.b.c)`.
---
 src/check_builtin.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/check_builtin.cpp b/src/check_builtin.cpp
index 00065b701..b4ab960d6 100644
--- a/src/check_builtin.cpp
+++ b/src/check_builtin.cpp
@@ -3146,6 +3146,13 @@ gb_internal bool check_builtin_procedure(CheckerContext *c, Operand *operand, As
 			}
 
 			ast_node(se, SelectorExpr, arg0);
+			if (unparen_expr(se->expr)->kind == Ast_SelectorExpr) {
+				gbString x = expr_to_string(arg0);
+				error(ce->args[0], "Chained expressions are not allowed for '%.*s', got '%s' ", LIT(builtin_name), x);
+				gb_string_free(x);
+				return false;
+
+			}
 
 			Operand x = {};
 			check_expr(c, &x, se->expr);