From: merch-redmine@...
Date: 2016-10-24T04:20:33+00:00
Subject: [ruby-core:77736] [Ruby trunk Bug#12861] super in a block can be either lexically or dynamically scoped depending on how the block is invoked

Issue #12861 has been updated by Jeremy Evans.


I don't think this is a bug, the ability to change the scope of a block is just part of ruby, and arguably one of the things that makes ruby flexible and a joy to program in:

~~~ ruby
foo = proc do
  bar
end

foo.call # main.bar method call

Object.define_method(:foo, &foo)
Object.foo # Object#bar method call

Object.define_singleton_method(:foo, &foo)
Object.foo # Object.bar method call

a = 'a'
a.instance_eval(&foo) # a.bar method call

Object.class_eval(&foo) # Object.bar method call
~~~

The fact that super is sometimes lexical and sometimes dynamic follows naturally from how method calls in blocks are sometimes lexical and sometimes dynamic, depending on how the block is invoked.

In any case, changing super behavior to be purely lexical by default would likely break a ton of existing ruby code.

----------------------------------------
Bug #12861: super in a block can be either lexically or dynamically scoped depending on how the block is invoked
https://bugs.ruby-lang.org/issues/12861#change-61038

* Author: bug hit
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux]
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
----------------------------------------
```ruby
class Class1
  def self.foo
    'foo'
  end
  def self.method1
    'method1'
  end
end

class Class2 < Class1
  def self.foo
    bar do
      super()
    end
  end
  def self.bar(&block)
    a = block.()
    define_singleton_method :method1, &block
    b = send(:method1)
    c = block.()
    [a, b, c]
  end
end

p Class2.foo # ["foo", "method1", "foo"]
```

It doesn't seem like a good idea for a given language construct to be either lexically or dynamically scoped, depending on how its surrounding block is invoked (which is not visible at the point of definition).  I think it would be better if super were always lexically scoped, and a different keyword (dynamic_super) were always dynamically scoped



-- 
https://bugs.ruby-lang.org/

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