#include <algorithm>
#include <iterator>
#include <map>
#include <string>
#include <vector>

std::vector<int> GetValuesAt(
    const std::multimap<std::string, std::string>& in,
    const std::string& key) {
    std::vector<int> out;
    std::transform(
        in.lower_bound(key),
        in.upper_bound(key),
        std::back_inserter(out),
        [](const std::string& value) {
            return std::stoi(value);
        });
    return out;
}

In file included from <source>:1:

/opt/compiler-explorer/clang-trunk-20200401/bin/../include/c++/v1/algorithm:1948:21: error: no matching function for call to object of type '(lambda at <source>:15:9)'

        *__result = __op(*__first);

                    ^~~~

<source>:11:10: note: in instantiation of function template specialization 'std::__1::transform<std::__1::__map_const_iterator<std::__1::__tree_const_iterator<std::__1::__value_type<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>, std::__1::__tree_node<std::__1::__value_type<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>, void *> *, long>>, std::__1::back_insert_iterator<std::__1::vector<int, std::__1::allocator<int>>>, (lambda at <source>:15:9)>' requested here

    std::transform(

         ^

<source>:15:9: note: candidate function not viable: no known conversion from 'const std::__1::__map_const_iterator<std::__1::__tree_const_iterator<std::__1::__value_type<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>, std::__1::__tree_node<std::__1::__value_type<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>, void *> *, long>>::value_type' (aka 'const pair<const std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>') to 'const std::string' (aka 'const basic_string<char, char_traits<char>, allocator<char>>') for 1st argument

        [](const std::string& value) {

        ^

<source>:15:9: note: conversion candidate of type 'int (*)(const std::string &)' (aka 'int (*)(const basic_string<char, char_traits<char>, allocator<char>> &)')

1 error generated.