Document the behaviour of switches w.r.t 18712

[thewilsonator]

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[thewilsonator]

@n8sh can you approve this?

[n8sh]

@thewilsonator I'll look it over.

[n8sh]

What do you mean about the scope extending to the end of a mixin statement? It sounds to me like you're saying this code shouldn't work because x is out of scope at writeln(x), but it works:

https://run.dlang.io/is/cSGXa6

void main(string[] args)
{
    import std.stdio;

    switch (args.length)
    {
    case 1:
        int x;
        mixin("x += 2;");
        writeln(x);
        break;
    default:
        writeln("default");
    }
}

[thewilsonator]

Perhaps that should be case labels, as

void main(string[] args)
{
    import std.stdio;

    switch (args.length)
    {
    mixin("case 1:");
        int x;
        x += 2;
        writeln(x);
        break;
    default:
        writeln("default");
    }
}

doesn't work.

[n8sh]

This also fails with the same error message:

void main(string[] args)
{
    import std.stdio;

    switch (args.length)
    {
    case 1:
        int x;
        x += 2;
        mixin("writeln(x);");
    mixin("default:");
        writeln("default");
    }
}

So the end of a mixin statement definitely doesn't close a case label's implicit scope.

[thewilsonator]

Huh. So the advice should be "don't mixin a case label".

[n8sh]

I think the problem is that a mixed-in case label neither starts a new scope nor closes the previous case label's scope. This works:

void main(string[] args)
{
    import std.stdio;

    switch (args.length)
    {
    case 1:
        int x;
        x += 2;
        writeln(x);
        break;
    case 2:
        writeln("2");
        break;
    mixin("default:");
        writeln("default");
    }
}

[thewilsonator]

Wow. I'll have to think a bit more about how to word this. Thanks!