1 files changed, 12 insertions, 0 deletions
diff --git a/tests/untried/pos/t8177.scala b/tests/untried/pos/t8177.scala
new file mode 100644
index 000000000..fe265f8d0
--- /dev/null
+++ b/tests/untried/pos/t8177.scala
@@ -0,0 +1,12 @@
+// exercise coevolveSym: SingleType with an underlying RefinedType
+trait Thing { type A }
+object IntThing extends Thing { type A = Int }
+
+// The following erroneously failed with  error: method f overrides nothing.
+// because asSeenFrom produced a typeref of the shape T'#A where A referred to a symbol defined in a T of times past
+// More precisely, the TypeRef case of TypeMap's mapOver correctly modified prefix
+// from having an underlying type of { type A = Ain } to { type A = Int }, with a new symbol for A (now with info Int),
+// but the symbol in the outer type ref wasn't co-evolved (so it still referred to the { type A = AIn } underlying the old prefix)
+// coEvolveSym used to only look at prefixes that were directly RefinedTypes, but they could also be SingleTypes with an underlying RefinedType
+class View[AIn](val in: Thing { type A = AIn }) {          def f(p: in.A): in.A = p }
+class SubView extends View[Int](IntThing)       { override def f(p: in.A): in.A = p }