__traits(compiles , mixin ... )

Adam D. Ruppe destructionator at gmail.com
Wed Oct 25 20:04:47 UTC 2017


On Wednesday, 25 October 2017 at 19:50:31 UTC, SrMordred wrote:
> so why this line resolves to false?

Because it is illegal to put a statement or declaration inside 
__traits(compiles). sorry, I should have said that before... even 
though the mixin can be legal in another context, it won't be in 
the __traits context due to this:

https://dlang.org/spec/traits.html#compiles

"Returns a bool true if all of the arguments compile (are 
semantically correct). The arguments can be symbols, types, or 
expressions that are syntactically correct. The arguments cannot 
be statements or declarations. "


When there's a closing ;, it is a mixin statement.

> void F(){}
> pragma(msg, __traits( compiles, mixin("F();") ) );//false




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