anchor.diff:                  [ match tcref.TypeReprInfo with
                     | TMeasureableRepr reprTy ->
                          for ity in GetImmediateInterfacesOfType skipUnref g amap m reprTy do
  -                          if isAppTy g ity then
  -                              let itcref = tcrefOfAppTy g ity
  +                          match tryTcrefOfAppTy g ity with
  +                          | ValueNone -> ()
  +                          | ValueSome itcref ->
                                 if not (tyconRefEq g itcref g.system_GenericIComparable_tcref) &&
  -                                 not (tyconRefEq g itcref g.system_GenericIEquatable_tcref)  then
  +                                 not (tyconRefEq g itcref g.system_GenericIEquatable_tcref) then
                                      yield ity
                     | _ -> ()
                     yield mkAppTy g.system_GenericIComparable_tcref [ty]
  
positive.code: let private FoldHierarchyOfTypeAux followInterfaces allowMultiIntfInst skipUnref visitor g amap m ty acc =
      let rec loop ndeep ty ((visitedTycon, visited: TyconRefMultiMap<_>, acc) as state) =
  
          let seenThisTycon = isAppTy g ty && Set.contains (tcrefOfAppTy g ty).Stamp visitedTycon
  
          // Do not visit the same type twice. Could only be doing this if we've seen this tycon
          if seenThisTycon && List.exists (typeEquiv g ty) (visited.Find (tcrefOfAppTy g ty)) then state else
  
negative.code: 
  /// Indicates if an F# type is the type associated with an F# exception declaration
  let isExnDeclTy g ty =
      match tryTcrefOfAppTy g ty with
      | ValueSome tcref -> tcref.IsExceptionDecl
      | _ -> false
  
  /// Get the base type of a type, taking into account type instantiations. Return None if the
  /// type has no base type.
  let GetSuperTypeOfType g amap m ty =
  #if !NO_EXTENSIONTYPING
      let ty =
          match tryTcrefOfAppTy g ty with
          | ValueSome tcref when tcref.IsProvided -> stripTyEqns g ty 
          | _ -> stripTyEqnsAndMeasureEqns g ty
  #else
      let ty = stripTyEqnsAndMeasureEqns g ty
  #endif
  