class Bundler::PubGrub::BasicPackageSource

def incompatibilities_for(package, version)
  package_deps = @cached_dependencies[package]
  sorted_versions = @sorted_versions[package]
  package_deps[version].map do |dep_package, dep_constraint_name|
    low = high = sorted_versions.index(version)
    # find version low such that all >= low share the same dep
    while low > 0 &&
        package_deps[sorted_versions[low - 1]][dep_package] == dep_constraint_name
      low -= 1
    end
    low =
      if low == 0
        nil
      else
        sorted_versions[low]
      end
    # find version high such that all < high share the same dep
    while high < sorted_versions.length &&
        package_deps[sorted_versions[high]][dep_package] == dep_constraint_name
      high += 1
    end
    high =
      if high == sorted_versions.length
        nil
      else
        sorted_versions[high]
      end
    range = VersionRange.new(min: low, max: high, include_min: true)
    self_constraint = VersionConstraint.new(package, range: range)
    if !@packages.include?(dep_package)
      # no such package -> this version is invalid
    end
    dep_constraint = parse_dependency(dep_package, dep_constraint_name)
    if !dep_constraint
      # falsey indicates this dependency was invalid
      cause = Bundler::PubGrub::Incompatibility::InvalidDependency.new(dep_package, dep_constraint_name)
      return [Incompatibility.new([Term.new(self_constraint, true)], cause: cause)]
    elsif !dep_constraint.is_a?(VersionConstraint)
      # Upgrade range/union to VersionConstraint
      dep_constraint = VersionConstraint.new(dep_package, range: dep_constraint)
    end
    Incompatibility.new([Term.new(self_constraint, true), Term.new(dep_constraint, false)], cause: :dependency)
  end
end