1 files changed, 35 insertions, 0 deletions
diff --git a/tests/ui/traits/new-solver/tait-eq-proj.rs b/tests/ui/traits/new-solver/tait-eq-proj.rs
new file mode 100644
index 000000000..01ef2ec95
--- /dev/null
+++ b/tests/ui/traits/new-solver/tait-eq-proj.rs
@@ -0,0 +1,35 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+#![feature(type_alias_impl_trait)]
+
+type Tait = impl Iterator<Item = impl Sized>;
+
+/*
+
+Consider the goal - AliasRelate(Tait, <[i32; 32] as IntoIterator>::IntoIter)
+which is registered on the line above.
+
+A. SubstRelate - fails (of course).
+
+B. NormalizesToRhs - Tait normalizes-to <[i32; 32] as IntoIterator>::IntoIter
+    * infer definition - Tait := <[i32; 32] as IntoIterator>::IntoIter
+
+C. NormalizesToLhs - <[i32; 32] as IntoIterator>::IntoIter normalizes-to Tait
+    * Find impl candidate, after substitute - std::array::IntoIter<i32, 32>
+    * Equate std::array::IntoIter<i32, 32> and Tait
+        * infer definition - Tait := std::array::IntoIter<i32, 32>
+
+B and C are not equal, but they are equivalent modulo normalization.
+
+We get around this by evaluating both the NormalizesToRhs and NormalizesToLhs
+goals together. Essentially:
+    A alias-relate B if A normalizes-to B and B normalizes-to A.
+
+*/
+
+fn a(_: Tait) {
+    let _: Tait = IntoIterator::into_iter([0i32; 32]);
+}
+
+fn main() {}