[ruby-core:113765] [Ruby master Feature#19708] Support `attr_reader :foo?`

Issue #19708 has been updated by byroot (Jean Boussier).


This was proposed and rejected by Matz several time in the past (see the linked issues).

Not saying it's impossible to try again, but you'll likely need a much stronger case than that to convince Matz.



----------------------------------------
Feature #19708: Support `attr_reader :foo?`
https://bugs.ruby-lang.org/issues/19708#change-103415

* Author: AMomchilov (Alexander Momchilov)
* Status: Open
* Priority: Normal
----------------------------------------
Creating reader methods with `attr_reader` is preferable over defining them by hand, not only because it's more convenient, but also because it hits a fast path in MRI (see `VM_METHOD_TYPE_IVAR`).

Since local and instance variables can't end with `?`, you can't use `attr_reader` to define predicate-style methods for boolean values, like:

```ruby
class Person
  attr_reader :name, :age, :active? # invalid attribute name `active?' (NameError)
  
  def initialize
    @name = "Bob"
    @age = 30
    @active = true
  end
end
```

It would be nice if `attr_reader` (and friends) could behave like:

```ruby
def active? = @active
```

(`attr_writer` and `attr_accessor` couldn't do the same, since `def active?=(new_value)` isn't valid, so they'd probably stick with `def active=(new_value)`)



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