Merge pull request #1227 from paulp/issue/6034

Fix for SI-6034, covariant value classes.

3 files changed, 10 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
index 2831afc48e..0820d3e714 100644
--- a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
+++ b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
@@ -111,7 +111,8 @@ abstract class ExtensionMethods extends Transform with TypingTransformers {
       }
 
     def extensionMethInfo(extensionMeth: Symbol, origInfo: Type, clazz: Symbol): Type = {
-      var newTypeParams = cloneSymbolsAtOwner(clazz.typeParams, extensionMeth)
+      // No variance for method type parameters
+      var newTypeParams = cloneSymbolsAtOwner(clazz.typeParams, extensionMeth) map (_ resetFlag COVARIANT | CONTRAVARIANT)
       val thisParamType = appliedType(clazz.typeConstructor, newTypeParams map (_.tpeHK))
       val thisParam     = extensionMeth.newValueParameter(nme.SELF, extensionMeth.pos) setInfo thisParamType
       def transform(clonedType: Type): Type = clonedType match {
diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala
index 37f41e2868..2e045b08b9 100644
--- a/src/reflect/scala/reflect/internal/Symbols.scala
+++ b/src/reflect/scala/reflect/internal/Symbols.scala
@@ -516,6 +516,7 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     def isTypeParameterOrSkolem = false
     def isTypeSkolem            = false
     def isTypeMacro             = false
+    def isInvariant             = !isCovariant && !isContravariant
 
     /** Qualities of Terms, always false for TypeSymbols.
      */
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index 01f615c5cc..b13b893635 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -3712,10 +3712,15 @@ trait Types extends api.Types { self: SymbolTable =>
    *  may or may not be poly? (It filched the standard "canonical creator" name.)
    */
   object GenPolyType {
-    def apply(tparams: List[Symbol], tpe: Type): Type = (
+    def apply(tparams: List[Symbol], tpe: Type): Type = {
+      tpe match {
+        case MethodType(_, _) =>
+          assert(tparams forall (_.isInvariant), "Trying to create a method with variant type parameters: " + ((tparams, tpe)))
+        case _                =>
+      }
       if (tparams.nonEmpty) typeFun(tparams, tpe)
       else tpe // it's okay to be forgiving here
-    )
+    }
     def unapply(tpe: Type): Option[(List[Symbol], Type)] = tpe match {
       case PolyType(tparams, restpe) => Some((tparams, restpe))
       case _                         => Some((Nil, tpe))