Start writing a Contribution Guide. Fix mypy scope and some small type errors.

docs/source/contributing/dev-workflow.md

+# Development Workflow
+
+This page contains instructions on how to get started with developing pystencils.
+
+## Prepare the Git Repository
+
+The pystencils Git repository is hosted at [i10git.cs.fau.de](https://i10git.cs.fau.de), the GitLab instance of the
+[Chair for Systems Simulation](https://www.cs10.tf.fau.de/) at [FAU Erlangen-Nürnberg](https://fau.de).
+In order to contribute code to pystencils, you will need to acquire an account there; to do so,
+please follow the instructions on the GitLab landing page.
+
+### Create a Fork
+
+Only the core developers of pystencils have write-access to the primary repository.
+To contribute, you will therefore have to create a fork of that repository
+by navigating to the [repository page](https://i10git.cs.fau.de/pycodegen/pystencils)
+and selecting *Fork* there.
+In this fork, you may freely create branches and develop code, which may later be merged to a primary branch
+via merge requests.
+
+### Create a Local Clone
+
+Once you have a fork of the repository, you can clone it to your local machine using the git command-line.
+
+:::{note}
+To clone via SSH, which is recommended, you will first have to [register an SSH key](https://docs.gitlab.com/ee/user/ssh.html).
+:::
+
+Open up a shell and navigate to a directory you want to work in.
+Then, enter
+
+```bash
+git clone git@i10git.cs.fau.de:<your-username>/pystencils.git
+```
+
+to clone your fork of pystencils.
+
+:::{note}
+To keep up to date with the upstream repository, you can add it as a secondary remote to your clone:
+```bash
+git remote add upstream git@i10git.cs.fau.de:pycodegen/pystencils.git
+```
+You can point your clone's `master` branch at the upstream master like this:
+```bash
+git pull --set-upstream upstream master
+```
+:::
+
+## Set Up the Python Environment
+
+To develop pystencils, you will need at least the following software installed on your machine:
+
+- Python 3.10 or later: Since pystencils minimal supported version is Python 3.10, we recommend that you work with Python 3.10 directly.
+- An up-to-date C++ compiler, used by pystencils to JIT-compile generated code
+- [Nox](https://nox.thea.codes/en/stable/), which we use for test automation.
+  Nox will be used extensively in the instructions on testing below.
+- Optionally [CUDA](https://developer.nvidia.com/cuda-toolkit),
+  if you have an Nvidia or AMD GPU and plan to develop on pystencils' GPU capabilities
+
+Once you have these, set up a [virtual environment](https://docs.python.org/3/library/venv.html) for development.
+This ensures that your system's installation of Python is kept clean, and isolates your development environment
+from outside influence.
+Use the following commands to create a virtual environment at `.venv` and perform an editable install of pystencils into it:
+
+```bash
+python -m venv .venv
+source .venv/bin/activate
+export PIP_REQUIRE_VIRTUALENV=true
+pip install -e .[dev]
+```
+
+:::{note}
+Setting `PIP_REQUIRE_VIRTUALENV` ensures that pip refuses to install packages globally --
+Consider setting this variable globally in your shell's configuration file.
+:::
+
+You are now ready to go! Create a new git branch to work on, open up an IDE, and start coding.
+Make sure your IDE recognizes the virtual environment you created, though.
+
+## Static Code Analysis
+
+### PEP8 Code Style
+
+We use [flake8](https://github.com/PyCQA/flake8/tree/main) to check our code for compliance with the
+[PEP8](https://peps.python.org/pep-0008/) code style.
+You can either run `flake8` directly, or through Nox, to analyze your code with respect to style errors:
+
+::::{grid}
+:::{grid-item}
+```bash
+nox -s lint
+```
+:::
+:::{grid-item}
+```bash
+flake8 src/pystencils
+```
+:::
+::::
+
+### Static Type Checking
+
+New code added to pystencils is required to carry type annotations,
+and its types are checked using [mypy](https://mypy.readthedocs.io/en/stable/index.html#).
+To discover type errors, run *mypy* either directly or via Nox:
+
+::::{grid}
+:::{grid-item}
+```bash
+nox -s typecheck
+```
+:::
+:::{grid-item}
+```bash
+mypy src/pystencils
+```
+:::
+::::
+
+:::{note}
+Type checking is currently restricted to the `codegen`, `jit`, `backend`, and `types` modules,
+since most code in the remaining modules is significantly older and is not comprehensively
+type-annotated. As more modules are updated with type annotations, this list will expand in the future.
+If you think a new module is ready to be type-checked, add an exception clause for it in the `mypy.ini` file.
+:::
+
+## Running the Test Suite
+
+Pystencils comes with an extensive and steadily growing suite of unit tests.
+To run the testsuite, you may invoke a variant of the Nox `testsuite` session.
+There are multiple different versions of the `testsuite` session, depending on whether you are testing with our
+without CUDA, or which version of Python you wish to test with.
+You can list the available sessions using `nox -l`.
+Select one of the `testsuite` variants and run it via `nox -s "testsuite(<variant>)"`, e.g.
+```
+nox -s "testsuite(cpu)"
+```
+for the CPU-only suite.
+
+During the testsuite run, coverage information is collected and displayed using [coverage.py](https://coverage.readthedocs.io/en/7.6.10/).
+You can display a detailed overview of code coverage by opening the generated `htmlcov/index.html` page.
+
+## Building the Documentation
+
+The pystencils documentation pages are written in MyST Markdown and ReStructuredText,
+located at the `docs` folder, and built using Sphinx.
+To build the documentation pages of pystencils, simply run the `docs` Nox session:
+```bash
+nox -s docs
+```
+
+This will emit the generated HTML pages to `docs/build/html`.
+The `docs` session permits two parameters to customize its execution:
+ - `--clean`: Clean the page generator's output before building
+ - `--fail-on-warnings`: Have the build fail (finish with a nonzero exit code) if Sphinx emits any warnings.
+
+You must pass any of these to the session command *after a pair of dashes* (`--`); e.g.:
+```bash
+nox -s docs -- --clean
+```

docs/source/contributing/index.md

+# Contributor Guide
+
+Welcome to the Contributor's Guide to pystencils!
+If you are interested in contributing to the development of pystencils, this is the place to start.
+
+Pystencils is an open-source package licensed under the [AGPL v3](https://www.gnu.org/licenses/agpl-3.0.en.html).
+As such, the act of contributing to pystencils by submitting a merge request is taken as agreement to the terms of the licence.
+
+:::{toctree}
+:maxdepth: 2    
+dev-workflow
+:::

docs/source/index.rst

@@ -95,8 +95,9 @@ Topics
 
 .. toctree::
   :maxdepth: 1
-  :caption: Advanced
+  :caption: Topics
 
+  contributing/index
   migration
   backend/index
 

mypy.ini

@@ -11,6 +11,12 @@ ignore_errors = False
 [mypy-pystencils.types.*]
 ignore_errors = False
 
+[mypy-pystencils.codegen.*]
+ignore_errors = False
+
+[mypy-pystencils.jit.*]
+ignore_errors = False
+
 [mypy-setuptools.*]
 ignore_missing_imports=true
 
@@ -22,3 +28,6 @@ ignore_missing_imports=true
 
 [mypy-cupy.*]
 ignore_missing_imports=true
+
+[mypy-cpuinfo.*]
+ignore_missing_imports=true

src/pystencils/codegen/config.py

@@ -448,6 +448,7 @@ class CreateKernelConfig:
         if cpu_openmp is not None:
             _deprecated_option("cpu_openmp", "cpu_optim.openmp")
 
+            deprecated_omp: OpenMpConfig | bool
             match cpu_openmp:
                 case True:
                     deprecated_omp = OpenMpConfig()

src/pystencils/codegen/driver.py

@@ -116,6 +116,7 @@ class DefaultKernelCreationDriver:
         self._target = self._cfg.get_target()
         self._platform = self._get_platform()
 
+        self._intermediates: CodegenIntermediates | None
         if retain_intermediates:
             self._intermediates = CodegenIntermediates()
         else: