How do you find the struct types in a module? - getting Error: unknown

Steven Schveighoffer schveiguy at gmail.com
Thu Feb 13 15:38:37 UTC 2020


On 2/13/20 9:47 AM, aliak wrote:
> Hi,
> 
> I'm trying to get a typed list of structs in my current module that 
> matches certain criteria. Something like:
> 
> module mod;
> 
> struct X {}
> struct Y {}
> 
> alias allTypes = ListOfTypes!mod;
> 
> But I'm having a bit of trouble. I have this so far:
> 
> template ListOfTypes(alias T) {
>      import std.meta;
>      enum isStruct(string m) = is(mixin(m) == struct);
>      enum types = Filter!(isStruct, __traits(allMembers, T));
>      alias toType(string m) = mixin(m);
>      alias all = staticMap!(toType, types);
>      alias CommandGroupsOf = all;
> }
> 
> pragma(msg, ListOfTypes!mod);
> 
> But that causes an error I've never seen before:
> 
> Error: unknown, please file report on issues.dlang.org
> onlineapp.d(30,1):        while evaluating `pragma(msg, 
> CommandGroupsOf!(mod))`
> 
> 
> Any workarounds or maybe insight in to the error?
> 
>

Not sure about your error, but here is a working version (don't use 
mixins, use __traits(getMember)):

import std.meta;
template ListOfStructs(alias mod)
{
     enum isStruct(string m) = is(__traits(getMember, mod, m) == struct);
     alias getMember(string m) = __traits(getMember, mod, m);
     alias ListOfStructs = staticMap!(getMember, Filter!(isStruct, 
__traits(allMembers, mod)));
}

-Steve


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