Support specialized method-handle based lambdas

```
scala> (x: Int) => {??? : Int}
res2: Int => Int = $$Lambda$1371/1961176822@6ed3ccb2

scala> res2(42)
scala.NotImplementedError: an implementation is missing
  at scala.Predef$.$qmark$qmark$qmark(Predef.scala:225)
  at .$anonfun$1(<console>:8)
  at $$Lambda$1371/1961176822.apply$mcII$sp(Unknown Source)
  ... 33 elided

scala> (x: Int, y: Long) => {??? : Int}
res4: (Int, Long) => Int = $$Lambda$1382/1796047085@6f8e8894

scala> res4(0, 0L)
scala.NotImplementedError: an implementation is missing
  at scala.Predef$.$qmark$qmark$qmark(Predef.scala:225)
  at .$anonfun$1(<console>:8)
  at $$Lambda$1382/1796047085.apply$mcIIJ$sp(Unknown Source)
  ... 33 elided
```

1 files changed, 16 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
index 086512677e..4f834d31ff 100644
--- a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
+++ b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
@@ -303,6 +303,17 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
     }
   }
 
+  def specializedFunctionName(sym: Symbol, args: List[Type]) = exitingSpecialize {
+    require(isFunctionSymbol(sym), sym)
+    val env: TypeEnv = TypeEnv.fromSpecialization(sym, args)
+    specializedClass.get((sym, env)) match {
+      case Some(x) =>
+        x.name
+      case None =>
+        sym.name
+    }
+  }
+
   /** Return the specialized name of 'sym' in the given environment. It
    *  guarantees the same result regardless of the map order by sorting
    *  type variables alphabetically.
@@ -315,10 +326,14 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
       if (sym.isClass) env.keySet
       else specializedTypeVars(sym).intersect(env.keySet)
     )
+    specializedName(sym.name, tvars, env)
+  }
+
+  private def specializedName(name: Name, tvars: immutable.Set[Symbol], env: TypeEnv): TermName = {
     val (methparams, others) = tvars.toList sortBy ("" + _.name) partition (_.owner.isMethod)
     // debuglog("specName(" + sym + ") env: " + env + " tvars: " + tvars)
 
-    specializedName(sym.name, methparams map env, others map env)
+    specializedName(name, methparams map env, others map env)
   }
 
   /** Specialize name for the two list of types. The first one denotes