@Nullable
  public Set<PsiElement> getTypeUsages(TypeMigrationUsageInfo element, TypeMigrationUsageInfo currentRoot) {
    return myRootUsagesTree.get(Pair.create(element, currentRoot));
  }
@Nullable
  public Set<PsiElement> getTypeUsages(TypeMigrationUsageInfo element, TypeMigrationUsageInfo currentRoot)