[ruby-core:92643] [Ruby trunk Feature#15848] Silence warning when conditional assignments are wrapped in parentheses

[sawadatsuyoshi@gmail.com]

Issue #15848 has been updated by sawa (Tsuyoshi Sawada).


Why does the parentheses indicate that assignment is intended, and not comparison?

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Feature #15848: Silence warning when conditional assignments are wrapped in parentheses
https://bugs.ruby-lang.org/issues/15848#change-78006

* Author: sos4nt (Stefan Schüßler)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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Sometime it's convenient to have an assignment in an `if`-condition. The Ruby documentation even contains an example showing this *"most common use of side-effect"* practice:

http://ruby-doc.org/core-2.6.3/doc/syntax/control_expressions_rdoc.html#label-if+Expression
```ruby
if a = object.some_value
  # do something to a
end
```

Running that code however results in a warning:

> warning: found = in conditional, should be ==

It's very unfortunate that the Ruby docs contain example code that the parser complains about. And it's unfortunate that we can't make use of conditional assignments without getting warnings or turning off warnings.

I propose an obvious change to the current warning mechanism:

**Don't show the warning when the assignment is wrapped in parentheses.**

```ruby
if a = object.some_value
  # warning
end

if (a = object.some_value)
  # no warning
end
```

This is the way RoboCop already works and it's also a known workaround from other languages.

It would also allow the documentation to contain a warning-free example.



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