Fixes

  - bring back valueOf, the old one fails many tests
  - correct check file
  - exclude pickling test involving Predef.implicitly

Author: odersky

compiler/test/dotc/pos-test-pickling.blacklist

@@ -49,3 +49,7 @@ i8651b.scala
 
 # uneliminated @uncheckedVariance after pickling
 annot-bootstrap.scala
+
+# interaction with Scala-2's implicitly
+i9793.scala
+

library/src/dotty/DottyPredef.scala

@@ -26,9 +26,9 @@ object DottyPredef {
    * }}}
    * @group utilities
    */
-  //inline def valueOf[T]: T = summonFrom {
-  //  case ev: ValueOf[T] => ev.value
-  //}
+  inline def valueOf[T]: T = summonFrom {
+    case ev: ValueOf[T] => ev.value
+  }
 
   /** Summon a given value of type `T`. Usually, the argument is not passed explicitly.
    *

tests/neg/implicitSearch.check

@@ -10,4 +10,4 @@
 -- Error: tests/neg/implicitSearch.scala:15:38 -------------------------------------------------------------------------
 15 |    listOrd(listOrd(implicitly[Ord[T]] /*not found*/)) // error
    |                                      ^
-   |  no implicit argument of type Test.Ord[T] was found for parameter ev of method implicitly in object DottyPredef
+   |        no implicit argument of type Test.Ord[T] was found for parameter e of method implicitly in object Predef