• Per =?UTF-8?B?Tm9yZGzDtnc=?= (10/10) Oct 11 2019 I want to check whether
• Paul Backus (7/17) Oct 11 2019 Seems like the second one requires strictly less semantic

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

I want to check whether

     auto _ = pred(T.init);
     static assert(is(typeof(_) == bool));

compiles or not.

Which one

     __traits(compiles, { auto _ = pred(T.init); static 
assert(is(typeof(_) == bool)); })

and

     is(typeof(pred(T.init)) == bool)

is preferred compilation performance-wise?

Paul Backus <snarwin gmail.com> writes:

On Friday, 11 October 2019 at 09:05:25 UTC, Per Nordlöw wrote:
 I want to check whether

     auto _ = pred(T.init);
     static assert(is(typeof(_) == bool));

 compiles or not.

 Which one

     __traits(compiles, { auto _ = pred(T.init); static 
 assert(is(typeof(_) == bool)); })

 and

     is(typeof(pred(T.init)) == bool)

 is preferred compilation performance-wise?

Seems like the second one requires strictly less semantic 
analysis and is shorter and easier to read, so I'd go with that.

Note that `pred(T.init)` will fail if pred accepts its argument 
by ref. If you want to handle that case, you have to do something 
like

     is(ReturnType!((T arg) => pred(arg)) == bool))