Fix #7375: Add regression test

tests/pos/i7375.scala

@@ -0,0 +1,23 @@
+trait Entity[M, T, P]:
+  extension (me: M) def receive(sender: T)(msg: P)(using Entity[T, M, P]): Unit
+  extension (me: M) def name(): String
+
+class GreetingPerson(private val name: String)
+
+object GreetingPerson:
+  given GreetingPersonEntity: Entity[GreetingPerson, GreetedPerson, String] with
+    extension (me: GreetingPerson) def receive(sender: GreetedPerson)(msg: String)(using Entity[GreetedPerson, GreetingPerson, String]): Unit =
+       println(f"Thanks for saying $msg, ${sender.name()}")
+
+    extension (me: GreetingPerson) def name() =
+      me.name
+
+class GreetedPerson(private val name: String)
+
+object GreetedPerson:
+  given GreetedPersonEntity: Entity[GreetedPerson, GreetingPerson, String] with
+    extension (me: GreetedPerson) def receive(sender: GreetingPerson)(msg: String)(using Entity[GreetingPerson, GreetedPerson, String]): Unit =
+      println(f"Thanks for saying $msg, ${sender.name()}")
+
+    extension (me: GreetedPerson) def name() =
+      me.name

tests/run/i7375.scala

@@ -0,0 +1,6 @@
+class Foo(private val name: String)
+
+extension (f: Foo) def name() = "bar"
+
+@main def Test =
+  assert(Foo("foo").name() == "bar")