Making enum join variadic

[Artur Skawina via Digitalmars-d-learn]

On 05/02/14 17:27, Meta via Digitalmars-d-learn wrote:
> On Friday, 2 May 2014 at 15:18:06 UTC, Artur Skawina via Digitalmars-d-learn wrote:
>> On 05/02/14 15:38, "Nordlöw" via Digitalmars-d-learn wrote:
>>>
>>> template MemberNamesUnion(E...) if (allSatisfy!(isEnum, E))
>>> {
>>>     bool[string] allMembers;   // used to detect member collisions
>>>     mixin({
>>>             string r = "enum MemberNamesUnion { ";
>>>             foreach (T; E) {
>>>                 import std.range: join;
>>>                 foreach (member; __traits(allMembers, T)) {
>>>                     static assert (member in allMembers, "Member collision");
>>>                     allMembers[member] = true;
>>>                 }
>>>                 r ~= [__traits(allMembers, T)].join(",") ~ ",";
>>>             }
>>>             return r ~ " }";
>>>         }());
>>> }
>>>
>>> It fails as
>>>
>>> enums.d(25,46): Error: static variable allMembers cannot be read at compile time
>>> enums.d(25,21):        while evaluating: static assert("a" in allMembers)
>>>
>>> Is there a solution to this problem?
>>
>> Move the AA declaration to inside the lambda, remove the 'static'
>> from the assert, and fix the condition ("member !in allMembers"), then
>> it will work.
> 
> But that will also move the compile time check to a runtime one.

No; mixin arguments are always evaluated at CT.

artur