5 ms·

> File.open(path).orReturnErr() Method syntax is reserved for functions. There are no method syntax macros. Since a return in a function terminates execution

> File.open(path).orReturnErr() Method syntax is reserved for functions. There are no method syntax macros. Since a return in a function terminates execution of this function, and not its caller, your example would not work.

zozbot234 5y ago
Right, so this should really be .orReturnErr , by analogy with .await . We just overload the dot symbol to mean both "method call" and "weird monadic stuff is happening here".
- simon_o 5y ago
  Exactly. ! for macros was a mistake anyway, I guess that's why they stopped using it with await.
  - yakubin 5y ago
    It wasn't. Without "!" it isn't obvious that you cannot take a: let a: Result<u8, u8> = /* whatever *; let b = match a { Ok(v) => Ok(foo(v)), e => e, }; and transform it into: let a: Result<u8, u8> = /* whatever *; let b = a.map(foo); if "foo" is a macro. When you substitute "foo!" for all the "foo" above, it is obvious.
    - simon_o 5y ago
      Perhaps macros shouldn't do things that aren't "obvious" then?
      - infogulch 5y ago
        As a rule, rust rejects the "simpler" choice that instead lay the burden of correctness at the feet of the user. I'm glad they keep a hard line here.
  - steveklabnik 5y ago
    > I guess that's why they stopped using it with await await cannot be a macro, it has to be built into the language, and so it doesn't have the ! because it's not one.
simon_o 5y ago
You realize the syntax has changed more than that?
- yakubin 5y ago
  Yes, but "->" vs ":", or kinds of brackets are superficial, while method syntax has a specific meaning.