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-rw-r--r--src/test/ui/project-cache-issue-31849.rs65
1 files changed, 65 insertions, 0 deletions
diff --git a/src/test/ui/project-cache-issue-31849.rs b/src/test/ui/project-cache-issue-31849.rs
new file mode 100644
index 000000000..07fb6abae
--- /dev/null
+++ b/src/test/ui/project-cache-issue-31849.rs
@@ -0,0 +1,65 @@
+// 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();
+}