public static @Nullable TypeMismatch deepCheck(@NotNull PsiType leftType,
                                                 @NotNull PsiType rightType,
                                                 @NotNull LookForMutualSubclass lookForMutualSubclass) {
    return deepCheck(leftType, rightType, new HashSet<>(), lookForMutualSubclass);
  }
public static @Nullable TypeMismatch deepCheck(@NotNull PsiType leftType,
                                                 @NotNull PsiType rightType,
                                                 @NotNull LookForMutualSubclass lookForMutualSubclass)