str.to!Enum performance

[realhet]

Hi,

I've compared 2 ways of converting enum identifier strings to 
enum value:
- implemented with a manual associative array: 45ms
- implemented by std.conv.to: `name.to!Enum()`: 1299ms

(batch= 500_000, I tested with looking up the Segoe MDL2 Asset 
symbol characters)

Anyone can tell me how std.to() is doing the conversion, is it 
using the simplest way: linear search?
Can anyone point it out in the sources?

I have no luck finding it in std.conv, it's quite big. I've only 
found the opposite way.

Thanks in advance.