Harmonize treatment of simplified between typer and unpickler

We got some spurious differences in the types in TemplateParents
because simplification was done in Typer but not in Unpickler.

With the change we get perfect matches for all files in pickleOK
also if we print their types.

Author: odersky

src/dotty/tools/dotc/core/pickling/TreeUnpickler.scala

@@ -787,10 +787,10 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table) {
         assert(currentAddr == end, s"$start $currentAddr $end ${astTagToString(tag)}")
         result
       }
-
-      setPos(start, 
-        if (tag < firstLengthTreeTag) readSimpleTerm()
-        else readLengthTerm())
+      
+      val tree = if (tag < firstLengthTreeTag) readSimpleTerm() else readLengthTerm()
+      tree.overwriteType(tree.tpe.simplified)
+      setPos(start, tree)
     }
 
     def readTpt()(implicit ctx: Context) = {

src/dotty/tools/dotc/typer/Typer.scala

@@ -475,7 +475,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         val expr1 = ascribeType(expr, pt)
         cpy.Block(block)(stats, expr1) withType expr1.tpe // no assignType here because avoid is redundant
       case _ =>
-        Typed(tree, TypeTree(pt))
+        Typed(tree, TypeTree(pt.simplified))
     }
     val leaks = escapingRefs(tree, localSyms)
     if (leaks.isEmpty) tree

test/dotc/tests.scala

@@ -32,7 +32,7 @@ class tests extends CompilerTest {
   val newDir = "./tests/new/"
   val dotcDir = "./src/dotty/"
 
-  @Test def pickle_pickleOK = compileDir(posDir + "pickleOK/", testPickling)
+  @Test def pickle_pickleOK = compileDir(posDir + "pickleOK/", "-Xprint-types" :: testPickling)
   @Test def pickle_pickling = compileDir(dotcDir + "tools/dotc/core/pickling", testPickling)
 
   @Test def pos_t2168_pat = compileFile(posDir, "t2168")