• NaN (4/4) Jan 18 2019 Template mixins can only mixin declarations. Was it ever
• Simen =?UTF-8?B?S2rDpnLDpXM=?= (15/18) Jan 18 2019 It's been suggested many times. Some explanation for why it's not
• Nicholas Wilson (3/6) Jan 18 2019 I plan to have a good discussion about it at DConf and see what
• H. S. Teoh (24/29) Jan 18 2019 I don't remember the rationale for this, but if you want to mixin

NaN <divide by.zero> writes:

Template mixins can only mixin declarations. Was it ever 
considered to allow them to mixin statements? Is it ever likely 
to be added? Or are there reasons it wasnt allowed?

Thanks.

Simen =?UTF-8?B?S2rDpnLDpXM=?= <simen.kjaras gmail.com> writes:

On Friday, 18 January 2019 at 11:07:10 UTC, NaN wrote:
 Template mixins can only mixin declarations. Was it ever 
 considered to allow them to mixin statements? Is it ever likely 
 to be added? Or are there reasons it wasnt allowed?

It's been suggested many times. Some explanation for why it's not 
allowed is in https://issues.dlang.org/show_bug.cgi?id=1734, but 
the motivations for disallowing it aren't really clear there.

Anyways, there is of course a workaround:

mixin template tmp() {
     auto __tmp = (() => i = 3)();
}

unittest {
     int i = 0;
     mixin tmp!();
     assert(i == 3);
}

--
   Simen

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Friday, 18 January 2019 at 11:07:10 UTC, NaN wrote:
 Template mixins can only mixin declarations. Was it ever 
 considered to allow them to mixin statements? Is it ever likely 
 to be added?

I plan to have a good discussion about it at DConf and see what 
can be done about/with it.

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Fri, Jan 18, 2019 at 11:07:10AM +0000, NaN via Digitalmars-d wrote:
 Template mixins can only mixin declarations. Was it ever considered to
 allow them to mixin statements? Is it ever likely to be added? Or are
 there reasons it wasnt allowed?
 
 Thanks.

I don't remember the rationale for this, but if you want to mixin
statements, you can use the Do template in the following workaround:

	import std.stdio;
	mixin template Do(alias fun) {
		int _dummy = { fun(); return 0; }();
	}
	
	mixin template MyMixin() {
		string strDecl = "abc";
		mixin Do!({ writeln("look ma, a statement!"); });
		int intDecl = 123;
		mixin Do!({ writeln("look ma, another statement!"); });
	}
	
	void main() {
		mixin MyMixin!();
		writeln(strDecl);
		writeln(intDecl);
	}

It's a bit ugly, but it works.


T

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