1const Foo = extern struct {
 2    derp: i32,
 3};
 4export fn foo(a: *i32) *Foo {
 5    return @fieldParentPtr("a", a);
 6}
 7
 8// error
 9//
10// :5:28: error: no field named 'a' in struct 'tmp.Foo'
11// :1:20: note: struct declared here