1 files changed, 27 insertions, 0 deletions
diff --git a/src/test/ui/type-alias-impl-trait/implied_lifetime_wf_check.rs b/src/test/ui/type-alias-impl-trait/implied_lifetime_wf_check.rs
new file mode 100644
index 000000000..b6a7264a5
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/implied_lifetime_wf_check.rs
@@ -0,0 +1,27 @@
+#![feature(type_alias_impl_trait)]
+
+// known-bug: #99840
+// this should not compile
+// check-pass
+
+type Alias = impl Sized;
+
+fn constrain() -> Alias {
+    1i32
+}
+
+trait HideIt {
+    type Assoc;
+}
+
+impl HideIt for () {
+    type Assoc = Alias;
+}
+
+pub trait Yay {}
+
+impl Yay for <() as HideIt>::Assoc {}
+// impl Yay for i32 {} // this already errors
+// impl Yay for u32 {} // this also already errors
+
+fn main() {}