module T::Private::Methods

def self._on_method_added(hook_mod, method_name, is_singleton_method: false)
  if T::Private::DeclState.current.skip_on_method_added
    return
  end
  current_declaration = T::Private::DeclState.current.active_declaration
  mod = is_singleton_method ? hook_mod.singleton_class : hook_mod
  if T::Private::Final.final_module?(mod) && (current_declaration.nil? || !current_declaration.decl_builder.final?)
    raise "#{mod} was declared as final but its method `#{method_name}` was not declared as final"
  end
  # Don't compute mod.ancestors if we don't need to bother checking final-ness.
  if @was_ever_final_names.include?(method_name) && @modules_with_final.include?(mod.object_id)
    _check_final_ancestors(mod, mod.ancestors, [method_name], nil)
    # We need to fetch the active declaration again, as _check_final_ancestors
    # may have reset it (see the comment in that method for details).
    current_declaration = T::Private::DeclState.current.active_declaration
  end
  if current_declaration.nil?
    return
  end
  T::Private::DeclState.current.reset!
  if method_name == :method_added || method_name == :singleton_method_added
    raise(
      "Putting a `sig` on `#{method_name}` is not supported" \
      " (sorbet-runtime uses this method internally to perform `sig` validation logic)"
    )
  end
  original_method = mod.instance_method(method_name)
  sig_block = lambda do
    T::Private::Methods.run_sig(hook_mod, method_name, original_method, current_declaration)
  end
  # Always replace the original method with this wrapper,
  # which is called only on the *first* invocation.
  # This wrapper is very slow, so it will subsequently re-wrap with a much faster wrapper
  # (or unwrap back to the original method).
  key = method_owner_and_name_to_key(mod, method_name)
  unless current_declaration.raw
    T::Private::ClassUtils.replace_method(mod, method_name) do |*args, &blk|
      method_sig = T::Private::Methods.maybe_run_sig_block_for_key(key)
      method_sig ||= T::Private::Methods._handle_missing_method_signature(
        self,
        original_method,
        __callee__,
      )
      # Should be the same logic as CallValidation.wrap_method_if_needed but we
      # don't want that extra layer of indirection in the callstack
      if method_sig.mode == T::Private::Methods::Modes.abstract
        # We're in an interface method, keep going up the chain
        if defined?(super)
          super(*args, &blk)
        else
          raise NotImplementedError.new("The method `#{method_sig.method_name}` on #{mod} is declared as `abstract`. It does not have an implementation.")
        end
      # Note, this logic is duplicated (intentionally, for micro-perf) at `CallValidation.wrap_method_if_needed`,
      # make sure to keep changes in sync.
      elsif method_sig.check_level == :always || (method_sig.check_level == :tests && T::Private::RuntimeLevels.check_tests?)
        CallValidation.validate_call(self, original_method, method_sig, args, blk)
      elsif T::Configuration::AT_LEAST_RUBY_2_7
        original_method.bind_call(self, *args, &blk)
      else
        original_method.bind(self).call(*args, &blk)
      end
    end
  end
  @sig_wrappers[key] = sig_block
  if current_declaration.decl_builder.final?
    @was_ever_final_names[method_name] = true
    # use hook_mod, not mod, because for example, we want class C to be marked as having final if we def C.foo as
    # final. change this to mod to see some final_method tests fail.
    note_module_deals_with_final(hook_mod)
    add_module_with_final_method(hook_mod, method_name, is_singleton_method)
  end
end