Proposal: Allow a non-fixed size array embedded in a class

[ygc369]

Related to #115 and dotnet/roslyn#6055
For example:

class A
{
    int a;
    object o[]; // not same as "object[] o;"
    public A(int a0)
    {   a=a0;  }
}
A aa=new(10) A(5); //aa.o.Length=10, aa.a=5
object o1=aa.o[9]=3; //ok, access to any elements of aa.o is ok
object[] o=aa.o; //compile error! aa.o is not a real array, it's embedded in aa, so it can't be referenced directly!

A class can only have at most one array with dynamic length, but can have more than one inline arrays with fixed length.
for example:

class A
{
    int a[10]; // fixed size
    int b[20]; //fixed size
    object c[]; //dynamic size
}

[Thaina]

You could use 3 grave accent to make code block

 > like this
 > ```C#
 > code
 > ```

[ig-sinicyn]

@ygc369
but why? You cannot save anything in terms of allocation size. You had to have an object header for the array or you will not able to pass it into another methods.

There's no gain in terms of memory locality as CLR allocates objects sequentially (this is simplified version, I know:) ).

There's no point to use embedded arrays for collection types as it's impossible to resize the embedded array without reallocating entire collection object.

And finally, there's no way to enable dynamic-sized embedded arrays for structs.

So, what's the point? 😕

The same relates to #212. There's stackalloc for locals and there will be Span / Memory for almost anything else.

What's missing? : )

[jnm2]

@Thaina you can also use more than three backticks if what you're trying to show contains three backticks:

You can use 3 backticks to make a code block:

````markdown
```c#
code
```
````

Becomes:

You can use 3 backticks to make a code block:

```c#
code
```