Compile delegate with enum into proper function?

[jmh530]

On Sunday, 8 May 2022 at 03:58:06 UTC, Tejas wrote:
> [snip]
>
> If there is only one possible value for the  overload, is there 
> an issue with using default arguments?
> [snip]

Default arguments are intended to be resolved at runtime. That 
is, if you compile a function with two parameters and one of them 
has a default, then the compiler will compile one function that 
has two parameters as inputs.

However, since `foo` above is a relatively simple function, if 
you compile with -O, then it gets inlined. It doesn't matter so 
much that whether `a` is an enum or a literal since the compiler 
knows what it is at compile time and will inline it to remove the 
call to `foo` anyway.

I am interested in more complex cases where the compiler isn't 
able to inline the function and where the behavior of the second 
parameter might be more significant. The default parameter would 
then be doing the calculation at runtime when ideally may be 
known at compile-time and the compiler could generate a separate 
function that is simpler taking only one parameter.