Allow inline variable declaration for in and ref parameter types

[gafter]

@Kentalot commented on Mon Jan 29 2018

Version Used:
I'm using C# 7.2 and version 15.5.3 of VS 2017 Enterprise.

Steps to Reproduce:

private static void GetValue(out string input)
{
    input = null;
}
private static void DoNothing(ref string input)
{
}

private static void DoNothingIn(in string input)
{
}

private static void Call()
{
    GetValue(out var x);
    DoNothing(ref var y = x);
    DoNothingIn(in var z = null);
}

Expected Behavior: Compiles and y is usable after calling DoNothing and z is usable after calling DoNothingIn and all of x, y, and z are basically null;

Actual Behavior:
Does not compile since you can't inline declare variables for ref or in keywords. I hope that's clear. Thanks!

---

@HaloFour commented on Mon Jan 29 2018

Proposals to change the behavior of the language are taken at the C# Language repository.

[MkazemAkhgary]

Also #1077.

[Kentalot]

Thanks guys. Sorry for posting in the wrong repo. #1077 is similar for the ref part, but I guess mine is new-ish that it's requesting a similar thing for the in keyword (I know they're related). But anyway, thanks for considering my request!

[MkazemAkhgary]

@ghost symmetry for out would be post assignment.

public bool M1(out Foo x)
{
    return M2(x = out Bar y);
}

pre assignment is not possible, because methods with out parameter are always forced to initialize out parameters which leads to overwriting your default values. its a completely unexpected behavior.