Avoid crashing when compiling stdLib213

    package scala does not have a member class Tuple2$mcCI$sp while compiling
    /__w/dotty/dotty/community-build/community-projects/stdLib213/src/library/scala/AnyValCompanion.scala,
    ...
    [error] dotty.tools.dotc.core.TypeError: package scala does not have a member class Tuple2$mcCI$sp
    [error] 	at dotty.tools.dotc.core.Denotations$Denotation.requiredSymbol(Denotations.scala:305)
    [error] 	at dotty.tools.dotc.core.Denotations$Denotation.requiredClass(Denotations.scala:340)
    [error] 	at dotty.tools.dotc.core.Definitions.SpecialisedTuple(Definitions.scala:1335)
    [error] 	at dotty.tools.dotc.transform.SpecializeTuples.transformApply(SpecializeTuples.scala:27)

Author: dwijnand

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

@@ -1634,6 +1634,7 @@ class Definitions {
       case List(x)    => Tuple1SpecializedParamClasses().contains(x.typeSymbol)
       case List(x, y) => Tuple2SpecializedParamClasses().contains(x.typeSymbol) && Tuple2SpecializedParamClasses().contains(y.typeSymbol)
       case _          => false
+    && base.owner.denot.info.member(base.name.specializedName(args)).disambiguate(_.isClass).exists
 
   def isSpecializableFunction(cls: ClassSymbol, paramTypes: List[Type], retType: Type)(using Context): Boolean =
     paramTypes.length <= 2