Battle-plan for CTFE

[Rory McGuire via Digitalmars-d-announce]

On Thu, Sep 1, 2016 at 11:26 PM, ag0aep6g via Digitalmars-d-announce <
digitalmars-d-announce at puremagic.com> wrote:

> On 09/01/2016 11:01 PM, Rory McGuire via Digitalmars-d-announce wrote:
>
>> I'm actually asking why we can't catch the ctfe error.
>>
>
> There is no CTFE error in your example. It doesn't compile in the first
> place, even without attempting any CTFE.
>
> [...]
>
>> Surely the ctfe engine could be changed to catch unsupported code
>> errors. (Not invalid, just unsupported at CT).
>>
>
> Maybe. It isn't obvious to me that it would be a good idea, but it's not
> obviously terrible either.
>
> The ctfe engine would have to "go past" the try anyway, right? This is
>> the part I don't understand. Is it because ctfe actually hasn't started
>> yet and some other analysis is freaking out?
>>
>
> It's just a compiler error. The snippet on its own fails compilation and
> there is no CTFE in there. Something like `static assert(_checkCTFE());`
> would involve CTFE. But that's not needed to trigger the error.
>



Yeah, I'm using an enum to force the evaluation during CT, and its dying
before CTFE from what I can tell. Here is another example:

void main() {
enum ret = ctfefunc();
mixin(ret);
}


string ctfefunc() {
static if (!assertCTFE!true) {
throw new Exception("Only during ctfe please...");
}
return `import std.stdio; writeln("ctfe generated this");`;
}

template assertCTFE(bool b) {
enum assertCTFE = __traits(compiles, _checkCTFE1());
}
void _checkCTFE1() {
static if (__ctfe) {

}
}
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