43 lines
1.3 KiB
Rust
43 lines
1.3 KiB
Rust
//@ check-pass
|
|
|
|
#![feature(offset_of_nested)]
|
|
#![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>();
|
|
}
|