1const X = extern opaque {};
 2const Y = packed opaque {};
 3
 4export fn foo(x: *X, y: *Y) void {
 5    _ = x;
 6    _ = y;
 7}
 8
 9// error
10//
11// :1:11: error: opaque types do not support 'packed' or 'extern'
12// :2:11: error: opaque types do not support 'packed' or 'extern'