SI-8177 refine embeddedSymbols

We look for any prefix that has a refinement class for a type symbol.
This includes ThisTypes, which were not considered before.

pos/t8177g.scala, neg/t0764*scala now compile, as they should

Additional test cases contributed by Jason & Paul.

1 files changed, 13 insertions, 0 deletions

diff --git a/test/files/pos/t8177b.scala b/test/files/pos/t8177b.scala
new file mode 100644
index 0000000000..b7ed9342a3
--- /dev/null
+++ b/test/files/pos/t8177b.scala
@@ -0,0 +1,13 @@
+// exercise coevolveSym: SingleType with an underlying RefinedType, via a type alias
+trait Thing { type A }
+object IntThing extends Thing { type A = Int }
+object ThingHolder { type Alias[AIn] = Thing { type A = AIn } }
+
+// 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: ThingHolder.Alias[AIn]) {          def f(p: in.A): in.A = p }
+class SubView extends View[Int](IntThing)       { override def f(p: in.A): in.A = p }
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