In my pet project I'm casting a lot of strings to named enum members.

    enum Animal { Gorilla, Shark, Alien, Rambo, Dolphin }
    auto foo = "Dolphin";
    auto fooAsEnum = foo.to!Animal;

While micro-optimizing because it's fun, I see that it's much faster (by some factor of >3.5x) to do such casts as associative array lookups rather than by using std.conv.to as above. As in, populate an Animal[string] array with all enum members indexed by the strings of their names, allowing you to get the Animal you want via animalAA[foo] or (foo in animalAA).

In comparison, what code is generated from the foo.to!Animal cast? A big final switch? A long if-else-if-else chain?

http://dpaste.dzfl.pl/7e700a1053c0

(Can the compiler not generate such code instead?)

enum to string uses a switch if possible (src/phobos/std/conv.d line 844)

I think the code that does string to enum is on line 2194, which is a foreach { if {} } loop that never breaks; it always checks all of them.