Module Constant oddity

module_madness.rb

module Mod
  A = :a
  const_set('B', :b)
end
Mod.module_exec do
  C = :c #This seems to just vanish entirely, but its actually being assigned elsewhere. See comments below.
  const_set('D', :d)
end

Mod::A #=> :a
Mod::B #=> :b

Mod::C #=> uninitialized constant Mod::C
Mod::D #=> :d

::C #=> :c

Colin is right, it seems that, due to a 'quirk' in the way ruby parses and evaluates the assignments of constants. They are set to the global namespace when attempted to be assigned in a block such as module_exec. This can be worked around by explicitly declaring the namespace, but it might not always be useful.

Mod.module_exec do
  Mod::C = :c
end

Mod::C #=> :c