mirror of https://github.com/rust-lang/rust
66 lines
1.4 KiB
Rust
66 lines
1.4 KiB
Rust
//@ run-pass
|
|
// Regression test for #31849: the problem here was actually a performance
|
|
// cliff, but I'm adding the test for reference.
|
|
|
|
pub trait Upcast<T> {
|
|
fn upcast(self) -> T;
|
|
}
|
|
|
|
impl<S1, S2, T1, T2> Upcast<(T1, T2)> for (S1,S2)
|
|
where S1: Upcast<T1>,
|
|
S2: Upcast<T2>,
|
|
{
|
|
fn upcast(self) -> (T1, T2) { (self.0.upcast(), self.1.upcast()) }
|
|
}
|
|
|
|
impl Upcast<()> for ()
|
|
{
|
|
fn upcast(self) -> () { () }
|
|
}
|
|
|
|
pub trait ToStatic {
|
|
type Static: 'static;
|
|
fn to_static(self) -> Self::Static where Self: Sized;
|
|
}
|
|
|
|
impl<T, U> ToStatic for (T, U)
|
|
where T: ToStatic,
|
|
U: ToStatic
|
|
{
|
|
type Static = (T::Static, U::Static);
|
|
fn to_static(self) -> Self::Static { (self.0.to_static(), self.1.to_static()) }
|
|
}
|
|
|
|
impl ToStatic for ()
|
|
{
|
|
type Static = ();
|
|
fn to_static(self) -> () { () }
|
|
}
|
|
|
|
|
|
trait Factory {
|
|
type Output;
|
|
fn build(&self) -> Self::Output;
|
|
}
|
|
|
|
impl<S,T> Factory for (S, T)
|
|
where S: Factory,
|
|
T: Factory,
|
|
S::Output: ToStatic,
|
|
<S::Output as ToStatic>::Static: Upcast<S::Output>,
|
|
{
|
|
type Output = (S::Output, T::Output);
|
|
fn build(&self) -> Self::Output { (self.0.build().to_static().upcast(), self.1.build()) }
|
|
}
|
|
|
|
impl Factory for () {
|
|
type Output = ();
|
|
fn build(&self) -> Self::Output { () }
|
|
}
|
|
|
|
fn main() {
|
|
// More parens, more time.
|
|
let it = ((((((((((),()),()),()),()),()),()),()),()),());
|
|
it.build();
|
|
}
|