Non-operand pointer error when dereferencing an iterator into a time range

Question

Using

auto empty_line = [](auto& str){ return str.size() == 0; };

we can do this:

auto line_range_with_first_non_empty = 
                ranges::view::drop_while(ranges::getlines(std::cin),empty_line);
auto input1 = std::stoi(*line_range_with_first_non_empty.begin());

and we can also do this:

auto line_range2 = ranges::getlines(std::cin);
auto iter2 = ranges::find_if_not(line_range2,empty_line);
auto input2 = std::stoi(*iter2);

Unfortunately, when I try to shorten the version above:

auto iter3 = ranges::find_if_not(ranges::getlines(std::cin),empty_line);
// auto input3 = std::stoi(*iter3);

I get an error message:

<source>:22:29: error: indirection requires pointer operand ('ranges::v3::dangling<ranges::v3::_basic_iterator_::basic_iterator<ranges::v3::getlines_range::cursor> >' invalid)
    auto input3 = std::stoi(*iter3);
                            ^~~~~~

I thought because of this infinite range, but I was wrong.

auto sin = std::istringstream{"\n\n\nmy line\n"};
auto iter4 = ranges::find_if_not(ranges::getlines(sin),empty_line);
// Error when deref.
// auto input4 = std::stoi(*iter4);

This leads to the same error.

<source>:27:29: error: indirection requires pointer operand ('ranges::v3::dangling<ranges::v3::_basic_iterator_::basic_iterator<ranges::v3::getlines_range::cursor> >' invalid)
    auto input4 = std::stoi(*iter4);
                        ^~~~~~

Why can't I dereference when it ranges::find_ifaccepts a range as an rvalue?

Does the ranges::getlinesrange return ? If so, should ranges own things?

godbolt.org/g/Yo6tKa

Answer 1

, , , , dangling, . .: -)