[ruby-core:123215] [Ruby Feature#21555] Add support for predicate attribute reader names

Issue #21555 has been updated by matz (Yukihiro Matsumoto).

Status changed from Open to Rejected

I still ask you to define `def valid? = @valid` manually. It is not much worse than `attr_reader :valid?`.

Matz.


----------------------------------------
Feature #21555: Add support for predicate attribute reader names
https://bugs.ruby-lang.org/issues/21555#change-114545

* Author: shan (Shannon Skipper)
* Status: Rejected
----------------------------------------
After manually aliasing predicate methods many times, I wanted to propose letting `attr_reader` take predicate method names that correspond to instance variables of the base name without a trailing question mark. https://github.com/ruby/ruby/pull/14391

If the base name method doesn't already exist, a predicate name defines a base name method attribute reader to alias then undefines the base name.

For example, this creates an `enabled?` method that reads `@enabled`:
```ruby
attr_reader :enabled?
```

This feature is only supported for `attr_reader` and `attr`, not `attr_writer` or `attr_accessor`, since setter methods cannot have question marks.

Example:
```ruby
class Example
  attr_reader :valid?, :meaning

  def initialize
    @valid = [true, false].sample
    @meaning = 42
  end
end

Example.new.valid? #=> true
```



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