Plug another space leak.

`initInfo` was retained in Symbols. When called from `Namer`, `initInfo` referred to
a completer, which referred to a context.

With this space leak plugged, we can now compile 1000 times core/Comments.scala (460lines)
with -Xmx400M.

There still seems to be a space leak on the order of 200KB per run, though. But that seems
to have to do with symbols, not contexts.

Author: odersky

src/dotty/tools/dotc/core/SymDenotations.scala

@@ -105,7 +105,7 @@ object SymDenotations {
     ownerIfExists: Symbol,
     final val name: Name,
     initFlags: FlagSet,
-    final val initInfo: Type,
+    initInfo: Type,
     initPrivateWithin: Symbol = NoSymbol) extends SingleDenotation(symbol) {
 
     //assert(symbol.id != 4940, name)
@@ -232,7 +232,7 @@ object SymDenotations {
           case _ =>
         }
         */
-      if (Config.checkNoSkolemsInInfo) assertNoSkolems(initInfo)
+      if (Config.checkNoSkolemsInInfo) assertNoSkolems(tp)
       myInfo = tp
     }
 
@@ -751,7 +751,7 @@ object SymDenotations {
     //    def isOverridable: Boolean = !!! need to enforce that classes cannot be redefined
     def isSkolem: Boolean = name == nme.SKOLEM
 
-    def isInlineMethod(implicit ctx: Context): Boolean = is(InlineMethod, butNot = Accessor) 
+    def isInlineMethod(implicit ctx: Context): Boolean = is(InlineMethod, butNot = Accessor)
 
     // ------ access to related symbols ---------------------------------
 

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

@@ -477,11 +477,9 @@ object ProtoTypes {
     def apply(tp: Type) = wildApprox(tp, this)
   }
 
-  @sharable private def dummyTree = untpd.Literal(Constant(null))
-
   /** Dummy tree to be used as an argument of a FunProto or ViewProto type */
   object dummyTreeOfType {
-    def apply(tp: Type): Tree = dummyTree withTypeUnchecked tp
+    def apply(tp: Type): Tree = untpd.Literal(Constant(null)) withTypeUnchecked tp
     def unapply(tree: Tree): Option[Type] = tree match {
       case Literal(Constant(null)) => Some(tree.typeOpt)
       case _ => None