tint: Add builtin tests for arguments passed by var

Change-Id: I81b69d23e40675d7f525e6369afec9aa0659d043
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/92321
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/test/tint/builtins/gen/var/insertBits/428b0b.wgsl.expected.wgsl b/test/tint/builtins/gen/var/insertBits/428b0b.wgsl.expected.wgsl
new file mode 100644
index 0000000..2dbf357
--- /dev/null
+++ b/test/tint/builtins/gen/var/insertBits/428b0b.wgsl.expected.wgsl
@@ -0,0 +1,23 @@
+fn insertBits_428b0b() {
+  var arg_0 = vec3<i32>();
+  var arg_1 = vec3<i32>();
+  var arg_2 = 1u;
+  var arg_3 = 1u;
+  var res : vec3<i32> = insertBits(arg_0, arg_1, arg_2, arg_3);
+}
+
+@stage(vertex)
+fn vertex_main() -> @builtin(position) vec4<f32> {
+  insertBits_428b0b();
+  return vec4<f32>();
+}
+
+@stage(fragment)
+fn fragment_main() {
+  insertBits_428b0b();
+}
+
+@stage(compute) @workgroup_size(1)
+fn compute_main() {
+  insertBits_428b0b();
+}