Proposal: allow 'stackalloc' followed by initialization

[ygc369]

For example:

Span<int> prime = stackalloc int[10] {2, 3, 5, 7, 11, 13, 17, 19, 23, 29}; // this should be allowed

[jcouv]

Tagging @VSadov @OmarTawfik

[alrz]

I think Span is similar to initializer_list<T> in C++. so we could default to Span when no type is specified.

var span = {1, 2, 3};

[orthoxerox]

@alrz What would be the backing store of {1, 2, 3}, an array?

[alrz]

@orthoxerox It could be a shorthand for Span<int> span = stackalloc int[3] {1, 2, 3};

[orthoxerox]

@alrz I think this might be too confusing. Nothing indicates that you cannot return this value from your method, but you can't.

[alrz]

Yeah, var x = { 1 }; is probably too magical, but I think these should be possible:

Span<int> x = { 1 };
Span<int> x = stackalloc [] { 1 };
Span<int> x = stackalloc int[] { 1 };
Span<int> x = stackalloc int[1] { 1 };

With arrays, you can use var in all cases except for the first one.

[VSadov]

The question of array initializers for stackalloc comes up very often nowdays.

It is fairly uncontroversial and a relatively small feature. It has been discussed before with near universal agreement that it should be done at some point

I have posted a proposal here #1122 - to make sure it does not fall off the list.