Proposal: yield each operator

[aeroelec]

Consider adding yield each operator that iterates through a list/array/enumerable, yield returning each element.

Option 1
The syntax could be

yield each var item in list where ... ;

This would simplify code to iterate through elements of a list. For example,

foreach (int i in numbers)
{
    if (i > 300) yield return i;
}

could be simplified to

yield each int i in numbers where i > 300;

If where clause is not needed, discard could be used

yield each _ in list;

Option 2
The syntax could be

yield each list;

Using the same example as in option 1,

foreach (int i in numbers)
{
    if (i > 300) yield return i;
}

could be simplified to

yield each numbers.Where(i => i > 300);

This is also useful for recursive iterators, such as

public static IEnumerable<Control> Children(this Control control)
{
    foreach (Control child in control.Controls)
    {
        yield return child;
        foreach (var grandchild in Children(child))
        {
            yield return grandchild;
        }
    }
}

could be simplified to

public static IEnumerable<Control> Children(this Control control)
{
    foreach (Control child in control.Controls)
    {
        yield return child;
        yield each Children(child);
    }
}

[333fred]

Duplicate of #378.