Merge pull request scala#4274 from retronym/ticket/9123

SI-9123 More coherent trees with patmat, dependent types

Author: adriaanm

src/compiler/scala/tools/nsc/transform/patmat/PatternMatching.scala

@@ -239,6 +239,11 @@ trait Interface extends ast.TreeDSL {
               case Ident(_) => subst(from, to)
               case _        => super.transform(tree)
             }
+            tree1 match {
+              case _: DefTree =>
+                tree1.symbol.modifyInfo(_.substituteTypes(from, toTypes))
+              case _ =>
+            }
             tree1.modifyType(_.substituteTypes(from, toTypes))
           }
         }

test/files/pos/t9123.flags

@@ -0,0 +1 @@
+-optimize -Ydelambdafy:method

test/files/pos/t9123.scala

@@ -0,0 +1,10 @@
+trait Setting {
+  type T
+  def value: T
+}
+
+object Test {
+  def test(x: Some[Setting]) = x match {
+    case Some(dep) => Some(dep.value) map (_ => true)
+  }
+}