For try loops

[hyeonu]

@ibraheemdev

for try x in foo.to_str()?.chars().next()?.foo()? {
  // ...
}

It seems similar with previously discussed for match syntax.

@ibraheemdev

for x in y {
    try {
        let x = foo.to_str()?.chars().next()?.foo()?;
        ...
    }
}

I don't think ignoring the error case is something we should encourage.