include/frozen/map.h:114:12: error: binding reference of type 'int' to value of type 'const int' drops 'const' qualifier

[nbrachet]

The following code snippet used to work (at least in git hash c5bfada) but now fails:

#include <string>

#include <frozen/string.h>
#include <frozen/map.h>

void foo(const std::string& s, int& i)
{
    static constexpr frozen::map<frozen::string, int, 2> MAP = {
        { "one", 1 },
        { "two", 2 }
    };

    i = MAP.at(frozen::string{s.data(), s.length()});
}

int main()
{
    int i;
    foo("one", i);
}

with the following error:

In file included from <source>:5:
.../frozen/include/frozen/map.h:114:12: error: binding reference of type 'int' to value of type 'const int' drops 'const' qualifier
    return at_impl(*this, key);
           ^~~~~~~~~~~~~~~~~~~
<source>:14:13: note: in instantiation of member function 'frozen::map<frozen::basic_string<char>, int, 2, std::__1::less<frozen::basic_string<char> > >::at' requested here
    i = MAP.at(frozen::string{s.data(), s.length()});
            ^
1 error generated.
Compiler returned: 1

Compiler: clang++ --std=c++14
OS: MacOS 10.15

[nbrachet]

The following looks it resolves the issue:

--- a/include/frozen/map.h
+++ b/include/frozen/map.h
@@ -110,7 +110,7 @@ public:
       : map{items, Compare{}} {}
 
   /* element access */
-  constexpr Value& at(Key const &key) const {
+  constexpr Value const& at(Key const &key) const {
     return at_impl(*this, key);
   }
   constexpr Value& at(Key const &key) {

[serge-sans-paille]

gotcha! Feel free to submit a PR (and add a testcase?)