1const Foo = union {
 2    A: i32,
 3    B: f32,
 4    C: bool,
 5};
 6export fn entry(foo: Foo) void {
 7    _ = foo;
 8}
 9
10// error
11// target=x86_64-linux
12//
13// :6:17: error: parameter of type 'tmp.Foo' not allowed in function with calling convention 'x86_64_sysv'
14// :6:17: note: only extern unions and ABI sized packed unions are extern compatible
15// :1:13: note: union declared here