From: shugo@...
Date: 2015-12-17T03:14:06+00:00
Subject: [ruby-core:72203] [Ruby trunk - Bug #11816] Partial safe navigation	operator

Issue #11816 has been updated by Shugo Maeda.


Marc-Andre Lafortune wrote:
> Matz, did you get a chance to think about the "precedence" level of `&.`? It would be harder to change after christmas...

Is it really hard to change after the release of Ruby 2.3?

IMHO, the current behavior of `x&.foo.bar` is useless, so users have to use `x&.foo&.bar` instead.
Even if the behavior of `x&.foo.bar` is changed as you expect, `x&.foo&.bar` still works, and users
can switch from `x&.foo&.bar` to `x&.foo.bar` gradually.

Please tell me if I miss anything.

I'm not against the proposal itself, but there's no enough time left....

FYI, the behavior of Groovy's `?.` seems to be the same as Ruby's `&.`:

```
$ groovy -e 'x = null; print(x?.foo.bar)' 
Caught: java.lang.NullPointerException: Cannot get property 'bar' on null object
java.lang.NullPointerException: Cannot get property 'bar' on null object
	at script_from_command_line.run(script_from_command_line:1)
```

Please tell me if someone knows the behavior in C#.


----------------------------------------
Bug #11816: Partial safe navigation operator
https://bugs.ruby-lang.org/issues/11816#change-55614

* Author: Marc-Andre Lafortune
* Status: Open
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* ruby -v: preview 2
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
I'm extremely surprised (and disappointed) that, currently:

    x = nil
    x&.foo.bar # => NoMethodError: undefined method `bar' for nil:NilClass

To make it safe, you have to write `x&.foo&.bar`. But if `foo` is never supposed to return `nil`, then that code isn't "fail early" in case it actually does. `nil&.foo.bar` is more expressive, simpler and is perfect if you want to an error if `foo` returned `nil`. To actually get what you want, you have to resort using the old form `x && x.foo.bar`...

In CoffeeScript, you can write `x()?.foo.bar` and it will work well, since it gets compiled to

    if ((_ref = x()) != null) {
      _ref.foo.bar;
    }

All the discussion in #11537 focuses on `x&.foo&.bar`, so I have to ask:

Matz, what is your understanding of `x&.foo.bar`?

I feel the current implementation is not useful and should be changed to what I had in mind. I can't see any legitimate use of `x&.foo.bar` currently.




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