no size yet for forward reference error

[Erik Smith via Digitalmars-d]

In the process of converting my working database interface to be 
template based, I now get the following compiler error:

Error: struct 
std.database.mock.database.Statement!int.Statement.Payload no 
size yet for forward reference

I minimized the code to make it easier reason about.  It seems to 
have something to do with Payload, but it may also have something 
to do with the ResultRange / Row circular references.

The error is reported in object.d(2762,45).  This is DMD v2.070.

Any Ideas?


unittest {
    auto db = Database!int.create();
    auto con = Connection!int(db);
}

struct Database(T) {
    static Database create() { return Database!T();}
}

struct Connection(T) {
    alias Database = .Database!T;
    alias Statement = .Statement!T;
}

struct Statement(T) {
    alias Connection = .Connection!T;
    alias Result = .Result;

    private:

    struct Payload {
        Connection con;
        this(Connection con_) {con = con_;}
        this(this) { assert(false); }
        void opAssign(Statement.Payload rhs) { assert(false); }
    }

    alias RefCounted!(Payload, RefCountedAutoInitialize.no) Data;
    Data data_;
}

struct Result(T) {
    alias Statement = .Statement!T;
    alias ResultRange = .ResultRange!T;
    alias Range = .ResultRange;
    alias Row = .Row;

    this(Statement stmt) {data_ = Data(stmt);}
    ResultRange range() {return ResultRange(this);}
}

struct ResultRange(T) {
    alias Result = .Result!T;
    alias Row = .Row!T;
    private Result result_;
    this(Result result) {result_ = result;}
}


struct Row(T) {
    alias Result = .Result!T;
    this(Result* result) { result_ = result;}
    private Result* result_;
}