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Comment by millstone | Hacker News Reader

When I'm reading code, I may not realize that an expression can return, because it can be hard to spot a ? embedded in the middle of the line:

    sanitize(getFile(getName())?.contents);

Swift requires prefixing the line with try, which makes it easier to notice:

    try sanitize(getFile(getName()).contents)

Both are a big improvement over exceptions which have no indication at the call site.

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Bit of a correction, I believe that `try` in Swift must precede an expression that can throw, rather than preceding a statement that can throw, so AFAICT the Swift code would have to be written like this:

  sanitize((try getFile(getName())).contents)

This sort of illustrates why Rust moved away from its own prefix `try!` macro to its postfix `?` operator: in a language that encourages chaining methods, `foo()?.bar()?.qux()?` looks better than `try!(try!(try!(foo()).bar()).qux())`.

No, `try` can be applied to any expression, and will "try" all throwing calls in subexpressions of that:

  func f() throws -> Int { return 0 }
  func nothing(_ x: Int) {}
  func g() throws {
    nothing(try f())
    try (f() + f())
    try nothing(f() * f())
  }

This includes method chains:

  struct Foo {
    init() throws {}
    func bar() throws -> Foo { return self }
    func qux() throws -> Foo { return self }
  }
  try Foo().bar().qux()

Cool, thanks, I looked in the official docs but didn't notice any mention of this feature. :)

Not sure how many editors' syntax highlighting do this by default, but at least for me, it really helped to make `?` bold red.

In Swift you can still bury that `try` in the middle of the expression

  sanitize(try getFile(getName()).contents)

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