Difference between "can call" and "can compile"

[FeepingCreature]

On Tuesday, 8 September 2020 at 20:04:32 UTC, Steven 
Schveighoffer wrote:
>
> Here's what it says when there is no constraint (and when I 
> actually call fun inside use):
>
> onlineapp.d(9): Error: undefined identifier oops
> onlineapp.d(4): Error: template instance onlineapp.bad!() error 
> instantiating
> onlineapp.d(20):        instantiated from here: use!(bad)
>
> This is what I want it to do. Why can't it just do that? Why do 
> I need to see 10 more or even 5 more lines of irrelevant error 
> messages?
>
> -Steve

Hear, hear.

And yes, `hasMember` also doesn't solve my problem in any way at 
all.