1 files changed, 19 insertions, 0 deletions
diff --git a/tests/ui/traits/next-solver/dont-remap-tait-substs.rs b/tests/ui/traits/next-solver/dont-remap-tait-substs.rs
new file mode 100644
index 000000000..b089f0df3
--- /dev/null
+++ b/tests/ui/traits/next-solver/dont-remap-tait-substs.rs
@@ -0,0 +1,19 @@
+// compile-flags: -Znext-solver
+// check-pass
+
+// Makes sure we don't prepopulate the MIR typeck of `define`
+// with `Foo<T, U> = T`, but instead, `Foo<B, A> = B`, so that
+// the param-env predicates actually apply.
+
+#![feature(type_alias_impl_trait)]
+
+type Foo<T: Send, U> = impl NeedsSend<T>;
+
+trait NeedsSend<T> {}
+impl<T: Send> NeedsSend<T> for T {}
+
+fn define<A, B: Send>(a: A, b: B, _: Foo<B, A>) {
+    let y: Option<Foo<B, A>> = Some(b);
+}
+
+fn main() {}