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//@ check-pass
#![deny(dead_code)]
// This struct contains a projection that can only be normalized after getting the field type.
struct A<T: Project> {
a: <T as Project>::EquateParamTo,
}
// This is the inner struct that we want to get.
struct MyFieldIsNotDead {
not_dead: u8,
}
// These are some helpers.
// Inside the param env of `test`, we want to make it so that it considers T=MyFieldIsNotDead.
struct GenericIsEqual<T>(T);
trait Project {
type EquateParamTo;
}
impl<T> Project for GenericIsEqual<T> {
type EquateParamTo = T;
}
fn test<T>() -> usize
where
GenericIsEqual<T>: Project<EquateParamTo = MyFieldIsNotDead>,
{
// The first field of the A that we construct here is
// `<GenericIsEqual<T>> as Project>::EquateParamTo`.
// Typeck normalizes this and figures that the not_dead field is totally fine and accessible.
// But importantly, the normalization ends up with T, which, as we've declared in our param
// env is MyFieldDead. When we're in the param env of the `a` field, the where bound above
// is not in scope, so we don't know what T is - it's generic.
// If we use the wrong param env, the lint will ICE.
std::mem::offset_of!(A<GenericIsEqual<T>>, a.not_dead)
}
fn main() {
test::<MyFieldIsNotDead>();
}
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