byKeyValue is not available at compilation-time right ?

[Mike Parker]

On Sunday, 25 July 2021 at 17:38:23 UTC, someone wrote:
>
>> i.e. your AA initialization is copy-pasted into each use of 
>> it, which means your program is rebuilding this AA at runtime 
>> every time it comes up. You probably got to this point as a 
>> bare `immutable structureLocations` errored out to the 
>> non-constant expression.
>
> Sounds bad, inefficient at least :(

The whole point of a manifest constant is that it is purely a 
compile-time entity that does not exist at runtime. It has no 
address. In other words, `enum a = 10` can be seen as an alias to 
the integer literal `10`. That means anywhere you use `a`, it's 
just like you typed in `10` instead. It is *not* the same as a 
`const` or `immutable` value.

Think of them as a way to avoid "magic literals". Instead of 
typing `10` or `[1, 2, 3]` in multiple initializers or function 
calls, you use an alias instead, then when you decide to use `20` 
or `[2, 4, 6]` instead, you can simply change the declaration of 
the manifest constant instead of at multiple locations. But 
you're *still* effectively passing a literal. So if at certain 
points in your code you want to avoid any allocations a literal 
would trigger, then you shouldn't be using manifest constants at 
those points either.