cgen: fix auto_eq for option eq operator overload (#20795)

Author: felipensp

vlib/v/gen/c/auto_eq_methods.v

@@ -188,7 +188,13 @@ fn (mut g Gen) gen_struct_equality_fn(left_type ast.Type) string {
 
 	// overloaded
 	if left.sym.has_method('==') {
-		fn_builder.writeln('\treturn ${fn_name}__eq(a, b);')
+		if left.typ.has_flag(.option) {
+			opt_ptr_styp := g.typ(left.typ.set_nr_muls(0).clear_flag(.option))
+			opt_fn_name := opt_ptr_styp.replace('struct ', '')
+			fn_builder.writeln('\treturn (a.state == b.state && b.state == 2) || ${opt_fn_name}__eq(*(${opt_ptr_styp}*)a.data, *(${opt_ptr_styp}*)b.data);')
+		} else {
+			fn_builder.writeln('\treturn ${fn_name}__eq(a, b);')
+		}
 		fn_builder.writeln('}')
 		return fn_name
 	}

vlib/v/tests/option_operator_overload_test.v

@@ -0,0 +1,38 @@
+import time
+
+struct SubTestTimeOptional[T] {
+	iis string
+	ext T
+}
+
+pub fn (s1 SubTestTimeOptional[T]) == (s2 SubTestTimeOptional[T]) bool {
+	return s1.iis == s2.iis
+}
+
+struct TestTimeOptional {
+	exp ?time.Time
+}
+
+fn now_optional[T]() SubTestTimeOptional[T] {
+	return SubTestTimeOptional[TestTimeOptional]{
+		iis: 'Vtest'
+		ext: TestTimeOptional{
+			exp: time.now()
+		}
+	}
+}
+
+fn now_delay_optional[T]() SubTestTimeOptional[T] {
+	return SubTestTimeOptional[T]{
+		iis: 'Vtest'
+		ext: TestTimeOptional{
+			exp: time.now().add_seconds(5)
+		}
+	}
+}
+
+fn test_main() {
+	mut t1 := now_optional[TestTimeOptional]()
+	mut t2 := now_delay_optional[TestTimeOptional]()
+	assert t1 != t2
+}