Merge syntheticTypeParamNames and syntheticLambdaParamNames

It seems like overengineering to use different names for
poly methods in definitions and synthetic lambdas.

Author: odersky

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

@@ -735,15 +735,11 @@ object StdNames {
   class ScalaTypeNames extends ScalaNames[TypeName] {
     protected implicit def fromString(s: String): TypeName = typeName(s)
 
-    def syntheticTypeParamName(i: Int): TypeName = "T" + i
-    def syntheticLambdaParamName(i: Int): TypeName = "X" + i
+    def syntheticTypeParamName(i: Int): TypeName = "X" + i
 
     def syntheticTypeParamNames(num: Int): List[TypeName] =
       (0 until num).map(syntheticTypeParamName)(breakOut)
 
-    def syntheticLambdaParamNames(num: Int): List[TypeName] =
-      (0 until num).map(syntheticLambdaParamName)(breakOut)
-
     final val Conforms = encode("<:<")
 
     final val Uninstantiated: TypeName = "?$"

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

@@ -1267,7 +1267,7 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
       original(tp1.appliedTo(tp1.typeParams.map(_.paramBoundsAsSeenFrom(tp1))), tp2)
     else
       PolyType(
-        paramNames = tpnme.syntheticLambdaParamNames(tparams1.length),
+        paramNames = tpnme.syntheticTypeParamNames(tparams1.length),
         variances = (tparams1, tparams2).zipped.map((tparam1, tparam2) =>
           (tparam1.paramVariance + tparam2.paramVariance) / 2))(
         paramBoundsExp = tl => (tparams1, tparams2).zipped.map((tparam1, tparam2) =>

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

@@ -2623,7 +2623,7 @@ object Types {
       Some((tl.typeParams, tl.resType))
 
     def any(n: Int)(implicit ctx: Context) =
-      apply(tpnme.syntheticLambdaParamNames(n), List.fill(n)(0))(
+      apply(tpnme.syntheticTypeParamNames(n), List.fill(n)(0))(
         pt => List.fill(n)(TypeBounds.empty), pt => defn.AnyType)
   }