Thanks :) At least I didn't overlook anything :)
On Tue, May 4, 2021 at 1:46 AM Ian Lance Taylor <i...@golang.org> wrote:
> On Mon, May 3, 2021 at 4:39 PM 'Axel Wagner' via golang-nuts
> <golang-nuts@googlegroups.com> wrote:
> >
> > this thread had me wonder again about a spec question that recently came
> up which I didn't have an answer to: Where does the spec say, which
> recursive type declarations are allowed and which aren't? For example, why
> is `type T *T` legal, but `type T T`ยน isn't?
> >
> > To be clear: I know why we can't make `type T T` et al. legal - the
> compiler needs to know the size of the values and it can't know it from a
> declaration like `type T T`. I'm wondering how this follows from the spec.
> >
> > I haven't read through all of the spec in a while, so I might just be
> missing an obvious section. But it doesn't seem to be described in the
> section about type declarations and some obvious keyword searches like
> "recursive" or "size" didn't turn up anything meaningful, as far as I can
> tell. But feel free to point me to a section I overlooked, and apologies if
> the question makes me seem lazy because it ends up being obvious :)
> >
> > [1] Maybe `type T struct { T }` is a better example, as it's a
> type-literal, not a type name - just like `type T *T`.
>
> I think you are correct that this is not explicitly defined anywhere.
> The basic rule is fairly straightforward: a type definition can't
> contain or embed an instance of itself, but it can otherwise refer to
> itself. But that ought to be in the spec, and as far as I know it is
> not.
>
> Ian
>
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