Proposal: Allow declaring local variables with "out var" to make them continue to be accessible outside of a block

[slimCODE]

Scenario: When using the using(IDisposable) pattern to acquire something, you often need to declare variables right before, forcing you to specify the type and initialize it.

ISomething thing = null;

using(var disposable = GetDisposable())
{
    thing = disposable.GetThing();
}

thing.Consume();

With the following construct, you would save one line, and avoid having to describe the variable type.

using(var disposable = GetDisposable())
{
    out var thing = disposable.GetThing();
}

thing.Consume();

[alrz]

relates to #451

[svick]

Small correction: you don't have to initialize the variable, this is valid code:

ISomething thing;

using(var disposable = GetDisposable())
{
    thing = disposable.GetThing();
}

thing.Consume();

[jcouv]

This doesn't appeal to me. It's unclear to which scope the declaration should escape. Also, I don't feel this helps readability.

[bartdesmet]

A subset of the problems this is trying to solve may be solvable by introducing using expressions:

string text = using (var sr = new StreamReader(path)) => sr.ReadToEnd();

where I've taken the liberty to use the => syntax for the first time to "promote" a statement to an expression, given that single-body-statement using statements are already valid. Syntax could be debated at length, e.g. if => is needed at all. The bigger question is whether "expression everything" is warranted. I could see it being useful for switch (already being discussed elsewhere) and lock:

string five = lock (gate) => dictionary[5];