add test

src/test/ui/implied-bounds/issue-101951.rs

@@ -0,0 +1,50 @@
+// Taken directly from that issue.
+//
+// This test detected that we didn't correctly resolve
+// inference variables when computing implied bounds.
+//
+// check-pass
+pub trait BuilderFn<'a> {
+    type Output;
+}
+
+impl<'a, F, Out> BuilderFn<'a> for F
+where
+    F: FnOnce(&'a mut ()) -> Out,
+{
+    type Output = Out;
+}
+
+pub trait ConstructionFirm {
+    type Builder: for<'a> BuilderFn<'a>;
+}
+
+pub trait Campus<T>
+where
+    T: ConstructionFirm,
+{
+    fn add_building(
+        &mut self,
+        building: &mut <<T as ConstructionFirm>::Builder as BuilderFn<'_>>::Output,
+    );
+}
+
+struct ArchitectsInc {}
+
+impl ConstructionFirm for ArchitectsInc {
+    type Builder = fn(&mut ()) -> PrettyCondo<'_>;
+}
+
+struct PrettyCondo<'a> {
+    _marker: &'a mut (),
+}
+
+struct CondoEstate {}
+
+impl Campus<ArchitectsInc> for CondoEstate {
+    fn add_building(&mut self, _building: &mut PrettyCondo<'_>) {
+        todo!()
+    }
+}
+
+fn main() {}