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