[Issue 19828] maxElement give wrong results

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19828

--- Comment #1 from Simen Kjaeraas <simen.kjaras at gmail.com> ---
This issue boils down to this line in std.algorithm.searching:

    static if (__traits(isSame, map, a => a))

For some reason, that returns true for some lambdas that are absolutely not
identical. Reduced version:

import std.stdio : writeln;

unittest {
    int[] arr = [0, 1];

    // Different.
    writeln(__traits(isSame, i => arr[i], a => a) ? "Same" : "Different");

    // Same.
    test!(i => arr[i], a => a);

    // Different.
    test!(i => arr[i], a => a * 4);
}

auto test(alias map1, alias map2)() {
    writeln(__traits(isSame, map1, map2) ? "Same" : "Different");
}

Filed that as a separate issue 19829 as this can be fixed in Phobos without
fixing DMD.

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