module T::Private::Methods

def self.build_sig(hook_mod, method_name, original_method, current_declaration, loc)
  begin
    # We allow `sig` in the current module's context (normal case) and inside `class << self`
    if hook_mod != current_declaration.mod && hook_mod.singleton_class != current_declaration.mod
      raise "A method (#{method_name}) is being added on a different class/module (#{hook_mod}) than the " \
            "last call to `sig` (#{current_declaration.mod}). Make sure each call " \
            "to `sig` is immediately followed by a method definition on the same " \
            "class/module."
    end
    if current_declaration.returns.equal?(ARG_NOT_PROVIDED)
      sig_error(loc, "You must provide a return type; use the `.returns` or `.void` builder methods. Method: #{original_method}")
    end
    signature = Signature.new(
      method: original_method,
      method_name: method_name,
      raw_arg_types: current_declaration.params,
      raw_return_type: current_declaration.returns,
      bind: current_declaration.bind,
      mode: current_declaration.mode,
      check_level: current_declaration.checked,
      soft_notify: current_declaration.soft_notify,
      override_allow_incompatible: current_declaration.override_allow_incompatible,
      generated: current_declaration.generated,
    )
    SignatureValidation.validate(signature)
    signature
  rescue => e
    super_method = original_method&.super_method
    super_signature = signature_for_method(super_method) if super_method
    T::Private::ErrorHandler.handle_sig_validation_error(
      e,
      method: original_method,
      declaration: current_declaration,
      signature: signature,
      super_signature: super_signature
    )
    Signature.new_untyped(method: original_method)
  end
end