Closes #2651

1 files changed, 23 insertions, 12 deletions

diff --git a/src/compiler/scala/tools/nsc/dependencies/Changes.scala b/src/compiler/scala/tools/nsc/dependencies/Changes.scala
index 2486c71acb..3c000f8a18 100644
--- a/src/compiler/scala/tools/nsc/dependencies/Changes.scala
+++ b/src/compiler/scala/tools/nsc/dependencies/Changes.scala
@@ -41,6 +41,8 @@ abstract class Changes {
   }
   case class ParentChanged(e: Entity) extends Change
 
+  private val changedTypeParams = new mutable.ListBuffer[String]
+
   private def sameSymbol(sym1: Symbol, sym2: Symbol): Boolean =
     sym1.fullName == sym2.fullName
   private def sameFlags(sym1: Symbol, sym2: Symbol): Boolean =
@@ -49,14 +51,14 @@ abstract class Changes {
     annotationsChecked.forall(a =>
       (sym1.hasAnnotation(a) == sym2.hasAnnotation(a)))
 
-  private def sameType(tp1: Type, tp2: Type) = {
+  private def sameType(tp1: Type, tp2: Type)(implicit strict: Boolean) = {
     def typeOf(tp: Type): String = tp.toString + "[" + tp.getClass + "]"
     val res = sameType0(tp1, tp2)
     //if (!res) println("\t different types: " + typeOf(tp1) + " : " + typeOf(tp2))
     res
   }
 
-  private def sameType0(tp1: Type, tp2: Type): Boolean = ((tp1, tp2) match {
+  private def sameType0(tp1: Type, tp2: Type)(implicit strict: Boolean): Boolean = ((tp1, tp2) match {
     /*case (ErrorType, _) => false
     case (WildcardType, _) => false
     case (_, ErrorType) => false
@@ -75,12 +77,18 @@ abstract class Changes {
     case (ConstantType(value1), ConstantType(value2)) =>
       value1 == value2
     case (TypeRef(pre1, sym1, args1), TypeRef(pre2, sym2, args2)) =>
-      sameType(pre1, pre2) &&
-      (sameSymbol(sym1, sym2) ||
-       ( sym1.isType && sym2.isType && sameType(sym1.info, sym2.info))) &&
-      (sym1.variance == sym2.variance) &&
-      ((tp1.isHigherKinded && tp2.isHigherKinded && tp1.normalize =:= tp2.normalize) ||
-         sameTypes(args1, args2))
+      val testSymbols =
+        if (!sameSymbol(sym1, sym2)) {
+          val v = (!strict && sym1.isType && sym2.isType && sameType(sym1.info, sym2.info))
+          if (v) changedTypeParams += sym1.fullName
+          v
+        } else
+          !sym1.isTypeParameter || !changedTypeParams.contains(sym1.fullName)
+
+      testSymbols && sameType(pre1, pre2) &&
+        (sym1.variance == sym2.variance) &&
+        ((tp1.isHigherKinded && tp2.isHigherKinded && tp1.normalize =:= tp2.normalize) ||
+           sameTypes(args1, args2))
          // @M! normalize reduces higher-kinded case to PolyType's
 
     case (RefinedType(parents1, ref1), RefinedType(parents2, ref2)) =>
@@ -106,7 +114,7 @@ abstract class Changes {
     case (PolyType(tparams1, res1), PolyType(tparams2, res2)) =>
       sameTypeParams(tparams1, tparams2) && sameType(res1, res2)
     case (ExistentialType(tparams1, res1), ExistentialType(tparams2, res2)) =>
-      sameTypeParams(tparams1, tparams2) && sameType(res1, res2)
+      sameTypeParams(tparams1, tparams2)(false) && sameType(res1, res2)(false)
     case (TypeBounds(lo1, hi1), TypeBounds(lo2, hi2)) =>
       sameType(lo1, lo2) && sameType(hi1, hi2)
     case (BoundedWildcardType(bounds), _) =>
@@ -139,25 +147,28 @@ abstract class Changes {
       ((tp1n ne tp1) || (tp2n ne tp2)) && sameType(tp1n, tp2n)
     }
 
-  private def sameTypeParams(tparams1: List[Symbol], tparams2: List[Symbol]) =
+  private def sameTypeParams(tparams1: List[Symbol], tparams2: List[Symbol])(implicit strict: Boolean) =
     sameTypes(tparams1 map (_.info), tparams2 map (_.info)) &&
     sameTypes(tparams1 map (_.tpe), tparams2 map (_.tpe)) &&
     (tparams1 corresponds tparams2)((t1, t2) => sameAnnotations(t1, t2))
 
-  def sameTypes(tps1: List[Type], tps2: List[Type]) = (tps1 corresponds tps2)(sameType)
+  private def sameTypes(tps1: List[Type], tps2: List[Type])(implicit strict: Boolean) =
+    (tps1 corresponds tps2)(sameType(_, _))
 
   /** Return the list of changes between 'from' and 'toSym.info'.
    */
   def changeSet(from: Type, toSym: Symbol): List[Change] = {
     implicit val defaultReason = "types"
+    implicit val defaultStrictTypeRefTest = true
 
     val to = toSym.info
+    changedTypeParams.clear
     def omitSymbols(s: Symbol): Boolean = !s.hasFlag(LOCAL | LIFTED | PRIVATE)
     val cs = new mutable.ListBuffer[Change]
 
     if ((from.parents zip to.parents) exists { case (t1, t2) => !sameType(t1, t2) })
       cs += Changed(toEntity(toSym))(from.parents.zip(to.parents).toString)
-    if (!sameTypeParams(from.typeParams, to.typeParams))
+    if (!sameTypeParams(from.typeParams, to.typeParams)(false))
       cs += Changed(toEntity(toSym))(" tparams: " + from.typeParams.zip(to.typeParams))
 
     // new members not yet visited