Simplify EtaExpand

Author: odersky

compiler/src/dotty/tools/dotc/core/TypeApplications.scala

@@ -10,7 +10,7 @@ import Decorators._
 import util.Stats._
 import Names._
 import NameOps._
-import Variances.{varianceConforms, variancesConform}
+import Variances.variancesConform
 import dotty.tools.dotc.config.Config
 
 object TypeApplications {
@@ -250,11 +250,9 @@ class TypeApplications(val self: Type) extends AnyVal {
   /** Convert a type constructor `TC` which has type parameters `X1, ..., Xn`
    *  to `[X1, ..., Xn] -> TC[X1, ..., Xn]`.
    */
-  def EtaExpand(tparams: List[TypeSymbol])(implicit ctx: Context): Type = {
-    val tparamsToUse = if (variancesConform(typeParams, tparams)) tparams else typeParamSymbols
-    HKTypeLambda.fromParams(tparamsToUse, self.appliedTo(tparams.map(_.typeRef)))
+  def EtaExpand(tparams: List[TypeSymbol])(implicit ctx: Context): Type =
+    HKTypeLambda.fromParams(tparams, self.appliedTo(tparams.map(_.typeRef)))
       //.ensuring(res => res.EtaReduce =:= self, s"res = $res, core = ${res.EtaReduce}, self = $self, hc = ${res.hashCode}")
-  }
 
   /** If self is not lambda-bound, eta expand it. */
   def ensureLambdaSub(implicit ctx: Context): Type =

compiler/src/dotty/tools/dotc/typer/VarianceChecker.scala

@@ -49,8 +49,8 @@ object VarianceChecker {
           def apply(x: Boolean, t: Type) = x && {
             t match {
               case tref: TypeParamRef if tref.binder `eq` tl =>
-                val v = paramVarianceSign(tref)
-                varianceConforms(variance, v) || { error(tref); false }
+                varianceConforms(variance, paramVarianceSign(tref))
+                || { error(tref); false }
               case AnnotatedType(_, annot) if annot.symbol == defn.UncheckedVarianceAnnot =>
                 x
               case _ =>