Error: 'this' is only defined in non-static member functions, not parse

Matej Nanut matejnanut at
Tue Jan 17 09:02:12 PST 2012

On 17 January 2012 16:54, H. S. Teoh <hsteoh at> wrote:
> This may be the cause of your trouble. If the nested class references
> members in the outer class, then moving it outside will break it, since
> it won't have an outer scope anymore.
> T
> --
> Only boring people get bored. -- JM

That was my guess too — but I'm not referencing the outer class. The
outer class is just using instances of the inner one. Also, the line number
of the error points to ‘new’ statements in the static method. (The calls
which instantiate subclasses of the inner class.) If I do "return null" it
works as well, without complaining. So it's not a referencing issue I think.

As you all seem eager to help, I will copy the entire class, without
subclasses, to here. I will be grateful for any comments regarding the
current issue at hand or about the code in general.

The ‘new’-ed Nodes are defined like ‘class CostNode : Node { ... }’.

Another note, the outer class is an inner class of another class as well,
if that makes a difference. Also, the outer class isn't really a class, it's
a struct, but renaming that to ‘class’ doesn't change anything either.

---- code begin ----
        class Node
            static Node parse(ref string line)
                string mnemonic = munch(line, "A-Z");
                line = line.stripLeft();
                auto op = mnemonic in mnemonics;
                if (!op)
                    throw new Exception("Unknown mnemonic: `" ~ mnemonic ~"'");

                final switch (*op)
                case NodeType.COST:
                    return new CostNode(line);
                case NodeType.PAUSE:
                    return new PauseNode(line);
                case NodeType.COLDR:
                    return new ColDrNode(line);
                case NodeType.COLRA:
                    return new ColRaNode(line);
                case NodeType.DROP:
                    return new DropNode(line);
                case NodeType.RAISE:
                    return new RaiseNode(line);

                /* Doing something like `return new Node()' doesn't work either.
                 * Only `return null' works here. */

            enum NodeType : ubyte

            static immutable NodeType[string] mnemonics;
            static this()
                mnemonics = [
                    "COST"  : NodeType.COST,
                    "PAUSE" : NodeType.PAUSE,
                    "COLDR" : NodeType.COLDR,
                    "COLRA" : NodeType.COLRA,
                    "DROP"  : NodeType.DROP,
                    "RAISE" : NodeType.RAISE

---- code end ----

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