Issue #11283 has been updated by Andrew Kozin.


Not, in my examples (from the initial post) it does not do that, but something different. Namely, it doesn't assigning a **new** proc (that would be OK)

Instead, the interpreter it looks around in search **what else** it could use when I doesn't send a proc, then takes what it found somewhere and pushes it to the method.

MRI doesn't let me decide whether the method should be called without a proc (that should be interpreted as asking for `Proc.new`, as in your example).
**This** is the bug, not the way it works out the `:define_method` call.

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Bug #11283: Block assigned implicitly
https://bugs.ruby-lang.org/issues/11283#change-53034

* Author: Andrew Kozin
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 1.9.3, 2.0, 2.1, 2.2, ruby-head
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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That is how it works:

    module Test
      def self.build(&block)
        klass = Class.new(Object)
        klass.__send__(:define_method, :foo)
        klass.__send__(:define_method, :bar)
        klass
      end
    end

    Tested = Test.build { :foo }
    # warning: tried to create Proc object without a block
    # => Tested
    Tested.new.foo
    # => :foo
    Tested.new.bar
    # => :foo

The block is assigned to all calls to `:define_method` via `Object#__send__` implicitly, while it wasn't asked to.

The behaviour is tested under MRI 1.9.3, 2.0, 2.1, 2.2, ruby-head. It doesn't occur under rbx-2 and jruby (1.7, 9.0.0.0).

For the context look at this thread https://github.com/mbj/mutant/issues/356



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