[ruby-core:71158] [Ruby trunk - Feature #11537] Introduce "Safe navigation operator"

Issue #11537 has been updated by Ary Borenszweig.


I know this is already decided and the commit is out there, but since you are adding new syntax and a new feature to the language, I suggest you reconsider https://bugs.ruby-lang.org/issues/9076

With that change, instead of adding special syntax for safe nil traversing, you get generalized syntax for the implicit block argument. Instead of this:

```
obj.?bar(x, y)
```

You do:

```
obj.try &.bar(x, y)
```

The `try` method is simply:

```
class Object
  # But obviously implemented in C for performance reasons
  def try
    yield self unless self.is_a?(NilClass)
  end
end
```

As I mention in the original issue, `foo &.bar` simply gets translated *by the parser* to something like `foo { |x| x.bar }` (where `x` doesn't conflict with any other identifier in the method). So it's just a change in the parser, no need to change compile.c, insns.def, etc (although I can understand that nil checking might be optimized with a VM instruction).

My main worry is code like this:

```
obj.?empty?
```

That looks confusing to the eye. I associate "?" next to method names to "query" methods, and now when reading an expression "?" can have several meanings (in addition to the ternary operator).

We already have this syntax in [Crystal](http://www.crystal-lang.org) and it's working really well.

----------------------------------------
Feature #11537: Introduce "Safe navigation operator"
https://bugs.ruby-lang.org/issues/11537#change-54531

* Author: Hiroshi SHIBATA
* Status: Closed
* Priority: Normal
* Assignee: Yukihiro Matsumoto
----------------------------------------
I sometimes write following code with rails application:

```ruby
u = User.find(id)
if u && u.profile && u.profile.thumbnails && u.profiles.thumbnails.large
  ...
```

or

```ruby
# Use ActiveSupport
if u.try!(:profile).try!(:thumbnails).try!(:large)
 ...
```
I hope to write shortly above code. Groovy has above operator named "Safe navigation operator" with "`?.`" syntax.
Ruby can't use "`?.`" operator.

Can we use "`.?`" syntax. like this:

```ruby
u = User.find(id)
u.?profile.?thumbnails.?large
```

Matz. How do you think about this?




-- 
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