Bring back iterator-from from pending

Author: odersky

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -657,7 +657,7 @@ trait Implicits { self: Typer =>
     arg.tpe match {
       case ambi: AmbiguousImplicits =>
         msg(s"ambiguous implicit arguments: ${ambi.explanation} of $where")(
-            s"ambiguous implicit arguments of type $pt found for $where")
+            s"ambiguous implicit arguments of type ${pt.show} found for $where")
       case _ =>
         val userDefined =
           for {

tests/pending/run/iterator-from.scala renamed to tests/run/iterator-from.scala

@@ -67,7 +67,7 @@ object Test extends dotty.runtime.LegacyApp {
     // The following does not work with the implicit change that propagates nested ambiguous errors to the top.
     // We get ambiguous implicits because Predef.$conforms and convertIfView both fit WeekDay.Value => Ordered[WeekDay.Value].
     // It does not work in scalac either; there we get a divergent implicit.
-    // testSet(Weekday.ValueSet(days:_*), days)
+    testSet(Weekday.ValueSet(days:_*), days)
 
     val treeMap = immutable.TreeMap(keyValues:_*)
     testMap(treeMap, keyValues)