From cc9e8eda3364dcb7bf5b92a3d3824b66c85ef05f Mon Sep 17 00:00:00 2001
From: Adriaan Moors <adriaan.moors@epfl.ch>
Date: Fri, 26 Feb 2010 09:16:22 +0000
Subject: closes #2797 -- no review (already done in tick...

closes #2797 -- no review (already done in ticket by Martin)

1) isHigherKindedType is now false for singletontype 2) toInstance
recurses when pre is a typevar: the problem is that pre.widen.typeSymbol
isNonBottomSubClass symclazz is true while pre.baseType(symclazz) is
NoType
---
 src/compiler/scala/tools/nsc/symtab/Types.scala | 15 ++++++---------
 test/files/pos/t2797.scala                      |  9 +++++++++
 2 files changed, 15 insertions(+), 9 deletions(-)
 create mode 100644 test/files/pos/t2797.scala

diff --git a/src/compiler/scala/tools/nsc/symtab/Types.scala b/src/compiler/scala/tools/nsc/symtab/Types.scala
index aa88996876..509f9b3835 100644
--- a/src/compiler/scala/tools/nsc/symtab/Types.scala
+++ b/src/compiler/scala/tools/nsc/symtab/Types.scala
@@ -968,6 +968,7 @@ trait Types extends reflect.generic.Types { self: SymbolTable =>
       incCounter(singletonBaseTypeSeqCount)
       underlying.baseTypeSeq prepend this
     }
+    override def isHigherKinded = false // singleton type classifies objects, thus must be kind *
     override def safeToString: String = prefixString + "type"
 /*
     override def typeOfThis: Type = typeSymbol.typeOfThis
@@ -1082,9 +1083,9 @@ trait Types extends reflect.generic.Types { self: SymbolTable =>
         underlyingPeriod = currentPeriod
         if (!isValid(period)) {
           underlyingCache = pre.memberType(sym).resultType;
+          assert(underlyingCache ne this, this)
         }
       }
-      assert(underlyingCache ne this, this)
       underlyingCache
     }
 
@@ -3051,17 +3052,13 @@ A type's typeSymbol should never be inspected directly.
 
     var capturedPre = emptySymMap
 
-    def stabilize(pre: Type, clazz: Symbol): Type = {
-      capturedPre get clazz match {
-        case Some(qvar) =>
-          qvar
-        case _ =>
+    def stabilize(pre: Type, clazz: Symbol): Type =
+      capturedPre.getOrElse(clazz, {
           val qvar = clazz freshExistential ".type" setInfo singletonBounds(pre)
           capturedPre += (clazz -> qvar)
           capturedParams = qvar :: capturedParams
           qvar
-      }
-    }.tpe
+      }).tpe
 
     /** Return pre.baseType(clazz), or if that's NoType and clazz is a refinement, pre itself.
      *  See bug397.scala for an example where the second alternative is needed.
@@ -3122,7 +3119,7 @@ A type's typeSymbol should never be inspected directly.
                   appliedType(as.head, args mapConserve (this)) // @M: was as.head
                 else instParam(ps.tail, as.tail);
               val symclazz = sym.owner
-              if (symclazz == clazz && (pre.widen.typeSymbol isNonBottomSubClass symclazz)) {
+              if (symclazz == clazz && !pre.isInstanceOf[TypeVar] && (pre.widen.typeSymbol isNonBottomSubClass symclazz)) {
                 pre.baseType(symclazz) match {
                   case TypeRef(_, basesym, baseargs) =>
                     //Console.println("instantiating " + sym + " from " + basesym + " with " + basesym.typeParams + " and " + baseargs+", pre = "+pre+", symclazz = "+symclazz);//DEBUG
diff --git a/test/files/pos/t2797.scala b/test/files/pos/t2797.scala
new file mode 100644
index 0000000000..4323664e91
--- /dev/null
+++ b/test/files/pos/t2797.scala
@@ -0,0 +1,9 @@
+class MyVector[A] {
+  def map[B](f: A => B): MyVector[B] = error("")
+}
+
+object Test {
+  def unzip[B, C](_this: MyVector[(B, C)]): (MyVector[B], MyVector[C]) = {
+    (_this.map{ bc => bc._1 }, _this.map{ bc => bc._2 })
+  }
+}
\ No newline at end of file
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