Allow for non-boolean singletons in if statements

[llfletch]

What if we were to allow if statements to support non-Boolean arguments if the arguments were singletons (the only argument in the if statement)? The main problem with using non-Boolean arguments in if statements seems to be having an assignment statement in the if statement such that the user doesn't realize that it is an assignment statement rather than a comparison. With singleton arguments, though, this isn't a problem and it could significantly shorten many if statements. For example:
if (variable != null) becomes if (variable)

When evaluated in an if statement, strings could be true if they have data and false if they are empty or null. Also, structures and object could be true if they contain any public data or false if they contain only the starting values (zero, false, null, etc.).

[svick]

When evaluated in an if statement, strings could be true if they have data and false if they are empty or null. Also, structures and object could be true if they contain any public data or false if they contain only the starting values (zero, false, null, etc.).

I think this would only lead to confusion about what exactly does if (x) do.

In this specific case, I believe clarity is more important than brevity.

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Also, it's not clear to me what a "singleton" is, since an if statement always takes only a single expression.

[bondsbw]

Similar: #871, #1410

[jnm2]

Also see the discussion in #196, #438, #1455.

[FurkanKambay]

If you want this for some classes you created, you can add an implicit operator for bool to your class:

public static implicit operator bool(Foo foo)
{
    return foo.IsValid; // this shows that it does not have to be a null check.
}

edit: or true and false operators if you don't want implicit casting. which are implemented like this: (you have to implement both)

public static bool operator true(Foo foo) => foo.IsValid;
public static bool operator false(Foo foo) => foo.IsValid;

[Thaina]

@FurkanKambay I think we could public static explicit operator bool(Foo foo)

[FurkanKambay]

@Thaina well that would require us to write if ((bool)foo) { } instead of if (foo) { } but I guess that has an advantage of being explicit.

[Thaina]

@FurkanKambay It seem I misunderstand your sentence if you don't want implicit casting