[Cthulhu_]

Unfortunately in C and its derivatives, the safeguards would have to be external tools (static analysis, linters); it's a perfectly valid statement in code.

I wouldn't mind if languages simply mark assignments in conditions as errors. It's clever code, but clever code should be avoided in critical systems. And in general, I guess.

[asveikau]

Not all c-syntax languages let you implicitly convert from integer or pointer to boolean though. Java and C# don't. I have heard MISRA C doesn't allow it.

I actually don't mind this feature of C personally, just playing devil's advocate. Some people feel really strongly about not implicitly allowing conversion to bool. This is why.

[wycy]

Assignments in conditionals can be handy handy, but I think it's better when there's a keyword for it. The Rust/Swift `if let` syntax is pretty nice for this.

    if let userID = 0 {}

vs

    if userID == 0 {}

The let syntax makes this error more obvious.

[kibwen]

Since you're using Rust as an example there, worth noting that unlike in C the assignment operator in Rust does not evaluate to the assigned value (it evaluates to the unit value `()` instead). In combination with the fact that `if` expressions in Rust require their conditions to be bools (the language has no automatic coercion to bool), this means that `if foo = 0` is guaranteed to be a type error.

(This difference in the behavior of the assignment operator is a result of Rust's ownership semantics; since assignment transfers ownership, having the assignment operator evaluate to the assigned value would actually result in the original assignment being entirely undone!)

[tenebrisalietum]

Assignments in conditions can sometimes be useful and lend clarity, if it makes sense for the assignment to "fail".

For the rough, rough example the below is probably not too clever.

`if (!(my_socket=new_socket(inet_addr)) { fail(); }`