Further simplifications and test fixes

Author: odersky

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

@@ -596,14 +596,7 @@ class TypeComparer(initctx: Context) extends ConstraintHandling[AbsentContext] w
             val saved = comparedTypeLambdas
             comparedTypeLambdas += tp1
             comparedTypeLambdas += tp2
-            val variancesOK =
-              variancesConform(tp1.typeParams, tp2.typeParams)
-              || { // if tp1 is of the form [X] =>> C[X] where `C` is co- or contra-variant
-                   // assume the variance of `C` for `tp1` instead. Fixes #7648.
-                tp1 match
-                  case EtaExpansion(tycon1) => variancesConform(tycon1.typeParams, tp2.typeParams)
-                  case _ => false
-              }
+            val variancesOK = variancesConform(tp1.typeParams, tp2.typeParams)
             try variancesOK && boundsOK && isSubType(tp1.resType, tp2.resType.subst(tp2, tp1))
             finally comparedTypeLambdas = saved
           case _ =>

compiler/test-resources/repl/i6474

@@ -1,8 +1,8 @@
 scala> object Foo1 { type T[+A] = (A, Int) }
 // defined object Foo1
-scala> object Foo2 { type T[+A] = [+B] =>> (A, B) }
+scala> object Foo2 { type T[+A] = [B] =>> (A, B) }
 // defined object Foo2
-scala> object Foo3 { type T[+A] = [+B] =>> [C] =>> (A, B) }
+scala> object Foo3 { type T[+A] = [B] =>> [C] =>> (A, B) }
 // defined object Foo3
 scala> ((1, 2): Foo1.T[Int]): Foo1.T[Any]
 val res0: (Any, Int) = (1,2)