Merge pull request #3412 from retronym/ticket/2066-2.10-compat

 -Xsource:2.10: lenient treatment of variance in <:<, =:=

3 files changed, 5 insertions, 2 deletions

diff --git a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
index 28afd18fe0..816916787e 100644
--- a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
+++ b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
@@ -51,6 +51,8 @@ abstract class MutableSettings extends AbsSettings {
 
   def Yrecursion: IntSetting
   def maxClassfileName: IntSetting
+
+  def isScala211: Boolean
 }
 
 object MutableSettings {
diff --git a/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala b/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
index 3c4e93f11d..f9b10c90be 100644
--- a/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
+++ b/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
@@ -173,11 +173,11 @@ trait TypeComparers {
   // SI-2066 This prevents overrides with incompatible variance in higher order type parameters.
   private def methodHigherOrderTypeParamsSameVariance(sym1: Symbol, sym2: Symbol) = {
     def ignoreVariance(sym: Symbol) = !(sym.isHigherOrderTypeParameter && sym.logicallyEnclosingMember.isMethod)
-    ignoreVariance(sym1) || ignoreVariance(sym2) || sym1.variance == sym2.variance
+    !settings.isScala211 || ignoreVariance(sym1) || ignoreVariance(sym2) || sym1.variance == sym2.variance
   }
 
   private def methodHigherOrderTypeParamsSubVariance(low: Symbol, high: Symbol) =
-    methodHigherOrderTypeParamsSameVariance(low, high) || low.variance.isInvariant
+    !settings.isScala211 || methodHigherOrderTypeParamsSameVariance(low, high) || low.variance.isInvariant
 
   def isSameType2(tp1: Type, tp2: Type): Boolean = {
     def retry(lhs: Type, rhs: Type) = ((lhs ne tp1) || (rhs ne tp2)) && isSameType(lhs, rhs)
diff --git a/src/reflect/scala/reflect/runtime/Settings.scala b/src/reflect/scala/reflect/runtime/Settings.scala
index 11db83d7d5..de5ba99900 100644
--- a/src/reflect/scala/reflect/runtime/Settings.scala
+++ b/src/reflect/scala/reflect/runtime/Settings.scala
@@ -48,4 +48,5 @@ private[reflect] class Settings extends MutableSettings {
 
   val Yrecursion        = new IntSetting(0)
   val maxClassfileName  = new IntSetting(255)
+  def isScala211        = true
 }