Fix incorrect line number if a `helper_method` errors

Currently if you use `helper_method` to define a method, and inside that method you get an error, the backtrace is off by one line.

This PR fixes that so that the backtrace now points to the line where you called `helper_method`.

actionpack/lib/abstract_controller/helpers.rb

@@ -84,10 +84,13 @@ module AbstractController
         file, line = location.path, location.lineno
 
         methods.each do |method|
-          _helpers_for_modification.class_eval <<~ruby_eval, file, line
+          # def current_user(*args, &block)
-            def #{method}(*args, &block)                    # def current_user(*args, &block)
+          #   controller.send(:'current_user', *args, &block)
-              controller.send(:'#{method}', *args, &block)  #   controller.send(:'current_user', *args, &block)
+          # end
-            end                                             # end
+          _helpers_for_modification.class_eval <<~ruby_eval.lines.map(&:strip).join(";"), file, line
+            def #{method}(*args, &block)
+              controller.send(:'#{method}', *args, &block)
+            end
             ruby2_keywords(:'#{method}')
           ruby_eval
         end

actionpack/test/controller/helper_test.rb

@@ -98,6 +98,9 @@ class HelperTest < ActiveSupport::TestCase
     def delegate_method() end
     def delegate_method_arg(arg); arg; end
     def delegate_method_kwarg(hi:); hi; end
+    def method_that_raises
+      raise "an error occurred"
+    end
   end
 
   def setup
@@ -145,6 +148,16 @@ class HelperTest < ActiveSupport::TestCase
     assert_equal(:there, @controller_class.new.helpers.delegate_method_kwarg(hi: :there))
   end
 
+  def test_helper_method_with_error_has_correct_backgrace
+    @controller_class.helper_method :method_that_raises
+    expected_backtrace_pattern = "#{__FILE__}:#{__LINE__ - 1}"
+
+    error = assert_raises(RuntimeError) do
+      @controller_class.new.helpers.method_that_raises
+    end
+    assert_not_nil error.backtrace.find { |line| line.include?(expected_backtrace_pattern) }
+  end
+
   def test_helper_attr
     assert_nothing_raised { @controller_class.helper_attr :delegate_attr }
     assert_includes master_helper_methods, :delegate_attr