class Bundler::Resolver

def resolve_requirement(spec, requirement, reqs, activated)
  # We are going to try activating the spec. We need to keep track of stack of
  # requirements that got us to the point of activating this gem.
  spec.required_by.replace requirement.required_by
  spec.required_by << requirement
  activated[spec.name] = spec
  # Now, we have to loop through all child dependencies and add them to our
  # array of requirements.
  spec.dependencies.each do |dep|
    next if dep.type == :development
    dep.required_by << requirement
    reqs << dep
  end
  # We create a savepoint and mark it by the name of the requirement that caused
  # the gem to be activated. If the activated gem ever conflicts, we are able to
  # jump back to this point and try another version of the gem.
  length = @stack.length
  @stack << requirement.name
  retval = catch(requirement.name) do
    resolve(reqs, activated)
  end
  # Since we're doing a lot of throw / catches. A push does not necessarily match
  # up to a pop. So, we simply slice the stack back to what it was before the catch
  # block.
  @stack.slice!(length..-1)
  retval
end