zero- and one-element tuples

[gafter]

To best align positional pattern-matching (which won't restrict the number of values being deconstructed) with tuples, please support zero-element and one-element tuple types and tuple expressions.

[AdamSpeight2008]

Doesn't the current tuple parser require a minimum of 2 values?

[alrz]

@AdamSpeight2008 Yes.

[bbarry]

Why not align the other way, don't recognize deconstruction syntax with fewer than 2 elements?

[HaloFour]

@gafter

I assume that this will be a post-C# 7.0 consideration?

@bbarry

Without support for conditional deconstruction of zero/one values then patterns like None() and Some(T) would be impossible.

[orthoxerox]

@bbarry Single-value tuples are necessary for primitive wrapper types.

[dsaf]

Would leveraging it for naming primitive return values be considered an abuse?

(int id) SaveSomethingToDb(Something smth);

instead of

int SaveSomethingToDbAndReturnId(Something smth);

[HaloFour]

I like how Swift handles "womples", they're effectively just the scalar value itself. So an Int32 is an (Int32) is an ((Int32)). This makes sense as 1, (1) and ((1)) are all the same value. Swift does not allow for naming the element of a "womple", though, which kind of makes sense.

[Richiban]

Will the zero-tuple be explicitly referred to as unit anywhere?

I'd love to see some support for this in the future, such as being able to use Func<int, ()> instead of Action<int>, for example.

[alrz]

I think the type (and literal) for unit could be () if it wasn't ambigious, but using it in place of void probably requires language support so you dont need to explicitly return ().

[jcouv]

@gafter Is this tracking a compiler/API change or a language feature? If the latter, could you close or move to csharplang?

[gafter]

Issue moved to dotnet/csharplang #883 via ZenHub