__traits(compiles) + mixin

[Andrej Mitrovic]

On Tuesday, 5 March 2013 at 07:53:15 UTC, cal wrote:
> I'm confused about this:
>
> import std.conv;
>
> void main()
> {
>     enum s = "`1`.to!int;";
>     enum c = __traits(compiles, mixin("{auto a = new 
> "~s~";}")); // line 1
>     mixin("auto a = "~s~";");
>  // line 2
> }
>
> This does not compile, giving errors about instantiating 
> std.conv.to!(int).to!(string). If I switch the order of lines 1 
> and 2 it compiles. Is this a bug or something I don't 
> understand about __traits(compiles)?

You can't test declarations inside of __traits(compiles), only 
expressions. It's in the docs: 
http://dlang.org/traits.html#compiles