Merge pull request scala#4368 from som-snytt/review/7784

SI-7784 Allow a singleton type over a constant value defn.

Author: lrytz

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -5193,7 +5193,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
         if (refTyped.isErrorTyped) {
           setError(tree)
         } else {
-          tree setType refTyped.tpe.resultType
+          tree setType refTyped.tpe.resultType.deconst
           if (refTyped.isErrorTyped || treeInfo.admitsTypeSelection(refTyped)) tree
           else UnstableTreeError(tree)
         }

test/files/neg/logImplicits.check

@@ -4,7 +4,7 @@ logImplicits.scala:2: applied implicit conversion from xs.type to ?{def size: ?}
 logImplicits.scala:7: applied implicit conversion from String("abc") to ?{def map: ?} = implicit def augmentString(x: String): scala.collection.immutable.StringOps
   def f = "abc" map (_ + 1)
           ^
-logImplicits.scala:15: inferred view from String("abc") to Int = C.this.convert:(p: String("abc"))Int
+logImplicits.scala:15: inferred view from String("abc") to Int = C.this.convert:(p: String)Int
   math.max(122, x: Int)
                 ^
 logImplicits.scala:19: applied implicit conversion from Int(1) to ?{def ->: ?} = implicit def ArrowAssoc[A](self: A): ArrowAssoc[A]

test/files/pos/t7784.scala

@@ -0,0 +1,13 @@
+object Test {
+  final val a = ""
+  var b: a.type = a
+  b = a
+
+  final val x = classOf[Object]
+  var y: x.type = x
+  y = x
+
+  final val e = Thread.State.NEW
+  var e1: e.type = e
+  e1 = e
+}