Proposal: single line 'checked;' and 'unchecked;' applying to the rest of the block

[epa]

The checked { ... } and unchecked { ... } syntax is easy to use but adds another level of blocks and indentation. A few years ago C# version 8 added an alternative syntax for using which applies to the rest of the current block. I suggest something similar:

int y = 20;
if (true)
{
    checked;
    -- From this point onwards, until the end of the block, arithmetic operations are checked for overflow.
    int x = 5 * y;
    int z = 10 * x;
}

That would be equivalent to

int y = 20;
if (true)
{
    checked
    {
        int x = 5 * y;
        int z = 10 * x;
    }
}

The same rule can handle having more than one checked; or unchecked; inside the same block: each one is equivalent to the old syntax starting a new block.

{
    checked;
    x = 5 * y;
    unchecked;
    z = 10 * x;
}

is equivalent to

{
    checked
    {
        x = 5 * y;
        unchecked
        {
            z = 10 * x;
        }
    }
}

The proposal #552 for a checked modifier on the method itself is perhaps motivated by a similar concern to reduce braces and nesting, but I think this way is simpler and more general.