Disable type simplify in unpickler

Author: noti0na1

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -1297,8 +1297,6 @@ class TreeUnpickler(reader: TastyReader,
       }
 
       val tree = if (tag < firstLengthTreeTag) readSimpleTerm() else readLengthTerm()
-      if (!tree.isInstanceOf[TypTree]) // FIXME: Necessary to avoid self-type cyclic reference in tasty_tools
-        tree.overwriteType(tree.tpe.simplified)
       setSpan(start, tree)
     }
 

tests/pos/pickleSkelom.scala

@@ -0,0 +1,15 @@
+class A
+
+type B = A
+
+def f[T](x: T): x.type & T = ???
+
+def g = {
+  var a: B = ???
+  f[A](a)
+}
+
+def testNN = {
+  var s: String = ???
+  s.nn
+}