Single statement returns with out parameters

[BalassaMarton]

Not sure if this was proposed before, I couldn't find it. When a method has a return type and out parameters, it gets verbose to populate them. Consider this made up function that determines if a string needs escaping, and returns the first escaped character index if so:

    static bool NeedsEscaping(string? input, out int pos)
    {
        if (string.IsNullOrEmpty(input))
        {
            pos = -1;

            return false;
        }

        if (input.StartsWith(' '))
        {
            pos = 0;

            return true;
        }

        for (var i = 0; i < input.Length; i++)
        {
            if (input[i] is '"' or '\'' or '\\')
            {
                pos = i;

                return true;
            }
        }

        if (input.EndsWith(' '))
        {
            pos = input.Length - 1;

            return true;
        }

        pos = -1;

        return false;
    }

With the proposed new syntax, return statements can include assignments for the out parameters:

    static bool NeedsEscaping(string? input, out int pos)
    {
        if (string.IsNullOrEmpty(input))
            return false with pos = -1;

        if (input.StartsWith(' '))
            return true with pos = 0;

        for (var i = 0; i < input.Length; i++)
        {
            if (input[i] is '"' or '\'' or '\\')
                return true with pos = i;
        }

        if (input.EndsWith(' '))
            return true with pos = input.Length - 1;

        return false with pos = -1;
    }

When there are multiple out parameters, they can be assigned in a single statement, separating assignments with a comma:

return true with p1 = value1, p2 = value2, p3 = value3;

Which would be lowered into:

{
    p1 = value1;
    p2 = value2;
    p3 = value3;
    return true;
}

[HaloFour]

pos = -1; return false;

is already legal and shorter than:

return false with pos = -1;

[BalassaMarton]

That's two statements that linters will break into multiple lines.

[DavidArno]

A tuple can be used to avoid the need for out:

static (bool needed, int pos) NeedsEscaping(string? input)
{
    if (string.IsNullOrEmpty(input)) return (false, -1);
    if (input.StartsWith(' ')) return (true, 0);
    
    for (var i = 0; i < input.Length; i++)
    {
        if (input[i] is '"' or '\'' or '\\') return (true, i);
    }

    if (input.EndsWith(' ')) return (true, input.Length - 1);

    return (false, -1);
}

and that can be matched in much the same way:

if (NeedsEscaping(someString) is (true, var pos))
{
    // do something with pos...
}

Out parameters really aren't needed anymore as we have NRTs, records, tuples and hopefully soon unions that all handle multiple return values far better. Further, Microsoft's own quality analyzer rule, CA1021: Avoid out parameters discourages the use of out parameters. Therefore the case for extending syntax around out parameters really feels far from compelling to me.

[BalassaMarton]

I get it, but this is not helpful when there are legacy API constaints.

[HaloFour]

Further, Microsoft's own quality analyzer rule, CA1021: Avoid out parameters discourages the use of out parameters.

IMO that does not apply to the bool Try(out X foo) pattern, which is considered idiomatic both in C# and in the runtime.

[BalassaMarton]

Closing it as @DavidArno somewhat explained why this will never happen

Further, Microsoft's own quality analyzer rule, CA1021: Avoid out parameters discourages the use of out parameters. Therefore the case for extending syntax around out parameters really feels far from compelling to me.