[ruby-core:112303] [Ruby master Bug#19426] Endless `Range#step` of object with `#succ` method does not work

Issue #19426 has been updated by nobu (Nobuyoshi Nakada).


Sorry that I merged the PR before seeing the reply.

With the same object, `Range#each` works as expected.

```ruby
(c..).each do |d|
  p d.i
  break if d.i > 3
end
```

This is because `c` is not compared against `nil` first.
I think `#step` should behave like this.

----------------------------------------
Bug #19426: Endless `Range#step` of object with `#succ` method does not work
https://bugs.ruby-lang.org/issues/19426#change-101739

* Author: nobu (Nobuyoshi Nakada)
* Status: Closed
* Priority: Normal
* Backport: 2.7: REQUIRED, 3.0: REQUIRED, 3.1: REQUIRED, 3.2: REQUIRED
----------------------------------------
Consider this `c` object which hash `#succ` method.

```ruby
c = Struct.new(:i) do
  def succ; self.class.new(i+1); end
  def <=>(other) i <=> other.i;end
end.new(0)
```

This `Range#step` works.

```ruby
(c..c.succ).step(1) do |d|
  p d.i # 0, 1
end
```

But it fails on an endless range.

```ruby
(c..).step(1) do |d|
  p d.i
  break if d.i > 3
end
```

```
-:3:in `<=>': undefined method `i' for nil:NilClass (NoMethodError)
	from -:10:in `step'
	from -:10:in `<main>'
```




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