self-referential-list.d

immutable struct Field {
    string type;
    string name;
}

immutable struct Structure {
    string name;
  Field[] fields;
}

mixin template Named(string name, alias value) {
  mixin("alias " ~ name ~ "= value;");
}

template StructureToStruct(Structure structure, alias StructureContainer) {
    static struct StructureToStruct {
        static foreach(field; structure.fields) {
            static if (field.type == "string") {
                mixin("string " ~ field.name ~ ";");
            } else {
                mixin("StructureContainer." ~ field.type ~ " *" ~ field.name ~ ";");
            }
        }
    }
}

const nestedStructureDefintions = [
    Structure("Struct1", [Field("string", "a"), Field("Struct2", "struct2")]),
    Structure("Struct2", [Field("string", "a"), Field("Struct1", "struct1")]),
];

const flatStructureDefintions = [
    Structure("Struct1", [Field("string", "a")]),
    Structure("Struct2", [Field("string", "a"), Field("Struct1", "struct1")]),
];

struct Structures {
    // Change to nestedStructureDefintions and this will fail.
    static foreach (structure; flatStructureDefintions) {
        // Is there a better way to rename a struct from a template?
        mixin Named!(structure.name, StructureToStruct!(structure, Structures));
    }
}

// This on the other hand compiles just fine.
struct NestedStructures {
    static struct Struct1 {
        string a;
        NestedStructures.Struct2 *struct2;
    }

    static struct Struct2 {
        string a;
        NestedStructures.Struct1 *struct1;
    }
}