Allow closures to take type parameters.

This shouldn't require any changes to backend,
as all type parameters will be erased in erasure

Conflicts:
	src/dotty/tools/dotc/core/Symbols.scala

Author: DarkDimius

src/dotty/tools/dotc/ast/tpd.scala

@@ -103,11 +103,14 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
    *  where the closure's type is the target type of the expression (FunctionN, unless
    *  otherwise specified).
    */
-  def Closure(meth: TermSymbol, rhsFn: List[List[Tree]] => Tree, targetType: Type = NoType)(implicit ctx: Context): Block = {
+  def Closure(meth: TermSymbol, rhsFn: List[List[Tree]] => Tree, targs: List[Tree] = Nil, targetType: Type = NoType)(implicit ctx: Context): Block = {
     val targetTpt = if (targetType.exists) TypeTree(targetType) else EmptyTree
+    val call =
+      if (targs.isEmpty) Ident(TermRef(NoPrefix, meth))
+      else TypeApply(Ident(TermRef(NoPrefix, meth)), targs)
     Block(
       DefDef(meth, rhsFn) :: Nil,
-      Closure(Nil, Ident(TermRef(NoPrefix, meth)), targetTpt))
+      Closure(Nil, call, targetTpt))
   }
 
   def CaseDef(pat: Tree, guard: Tree, body: Tree)(implicit ctx: Context): CaseDef =

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

@@ -245,7 +245,7 @@ trait Symbols { this: Context =>
     for (name <- names) {
       val tparam = newNakedSymbol[TypeName](NoCoord)
       tparamBuf += tparam
-      trefBuf += TypeRef(owner.thisType, name).withSym(tparam, Signature.NotAMethod)
+      trefBuf += TypeRef.withSymAndName(owner.thisType, tparam, name)
     }
     val tparams = tparamBuf.toList
     val bounds = boundsFn(trefBuf.toList)
@@ -319,7 +319,7 @@ object Symbols {
     type ThisName <: Name
 
     private[this] var _id: Int = nextId
-    //assert(_id != 12325)
+    //assert(_id != 5859)
 
     /** The unique id of this symbol */
     def id = _id