Resharper C++ 20 module support wants to add forward declaration

Created December 31, 2022 01:10

I have created a project from the Named modules tutorial C++ using the steps in the web-site using vs2022 17.4.3 and Resharper c++ 2022.3.1

The project compiles and runs correctly.

However, Resharper incorrectly suggest in the module unit implementation file - BasicPlane.Figures-Rectangle.cpp - that a forward declaration for Rectangle is required, highlights the class name and provides a popup to make the fix. However, the fix is unnecessary. See the image below:

If the fix is applied, then further errors are indicated (Type Rectangle is incomplete). See below:

I have been able to turn off the fix popup but not remove the red highlighting. Is there some way of turning off the fix suggestion altogether? Is there any other work around?

5 comments

Igor Akhmetov

Created December 31, 2022 07:17

Hello,

Could you please send us your project for investigation? You can upload it to https://uploads.jetbrains.com/, let us know the upload id.

Thanks!

Rogerbeck145

Created January 02, 2023 23:57

Done.

Upload ID: 2023_01_02_2cLp6sA4dzXFKTKW26DGvk

Igor Akhmetov

Created January 03, 2023 11:19

Thanks!

I believe both the MSVC compiler and the tutorial are incorrect and that you need "import :Rectangle;" in BasicPlane.Figures-Rectangle.cpp to make the code conforming to the standard.

I've filed an issue with MS with my reasoning - https://developercommunity.visualstudio.com/t/%D0%A120-modules:-a-partition-implementatio/10243503, take a look if you're interested in details.

Igor Akhmetov

Created January 05, 2023 17:24

One more note. According to the C++ standard (https://eel.is/c++draft/module#unit-3), it looks like a single module partition cannot be defined in multiple module units, e.g. a .cpp and an. ixx files:

A module partition is a module unit whose module-declaration contains a module-partition. A named module shall not contain multiple module partitions with the same module-partition.

So this means that the BasicPlane.Figures:Rectangle partition cannot be split over two files in conformant code, and the tutorial is somewhat misleading.

Rogerbeck145

Created January 10, 2023 07:58

Thanks for the feedback

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