Guidance on AI coding tools (#5670)

Establish some guidance on using AI coding tools when contributing to
the Carbon
Language project. These tools have growing popularity and interest, and
it would
be good to have a clear and actively documented set of guidance for
folks
interested or already using them.

---------

Co-authored-by: Jon Ross-Perkins <jperkins@google.com>

CONTRIBUTING.md

@@ -25,6 +25,7 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
     -   [Collaboration systems](#collaboration-systems)
         -   [Getting access](#getting-access)
     -   [Contribution tools](#contribution-tools)
+        -   [Using AI-based contribution tools](#using-ai-based-contribution-tools)
     -   [Contribution guidelines and standards](#contribution-guidelines-and-standards)
         -   [Guidelines and philosophy for contributions](#guidelines-and-philosophy-for-contributions)
         -   [How to say things](#how-to-say-things)
@@ -228,6 +229,25 @@ as well as helpful tooling that will ease the contribution process. For example,
 [pre-commit](https://pre-commit.com) is used to simplify
 [code review](/docs/project/code_review.md).
 
+#### Using AI-based contribution tools
+
+All submissions to Carbon need to follow our
+[Contributor License Agreement (CLA)](#contributor-license-agreements-clas), in
+which contributors agree that their contribution is an original work of
+authorship. This doesn’t prohibit the use of coding assistance tools, but what’s
+submitted does need to be a contributor’s original creation.
+
+All contributions, regardless of what tools are used, are also still subject to
+normal code review and our
+[guidelines and standards](#contribution-guidelines-and-standards) below.
+
+Additionally, we want contributions to Carbon to also be viable as contributions
+to LLVM so that we can move things between these projects where relevant. We
+selected our license in part for this reason, and the same should be true for
+the use of AI-based coding tools. Any contributions to Carbon should also abide
+by the guidance in the
+[LLVM Developer Policy around AI generated code](https://llvm.org/docs/DeveloperPolicy.html#ai-generated-contributions).
+
 ### Contribution guidelines and standards
 
 All documents and pull requests must be consistent with the guidelines and

proposals/p5670.md

@@ -0,0 +1,89 @@
+# Guidance on AI coding tools
+
+<!--
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+-->
+
+[Pull request](https://github.com/carbon-language/carbon-lang/pull/5670)
+
+<!-- toc -->
+
+## Table of contents
+
+-   [Abstract](#abstract)
+-   [Problem](#problem)
+-   [Background](#background)
+-   [Proposal](#proposal)
+-   [Rationale](#rationale)
+-   [Alternatives considered](#alternatives-considered)
+    -   [Place more restrictions around AI-based tool usage when contributing](#place-more-restrictions-around-ai-based-tool-usage-when-contributing)
+
+<!-- tocstop -->
+
+## Abstract
+
+Establish some guidance on using AI coding tools when contributing to the Carbon
+Language project. These tools have growing popularity and interest, and it would
+be good to have a clear and actively documented set of guidance for folks
+interested or already using them.
+
+## Problem
+
+AI-based coding tools are wildly popular at this point and we should have active
+guidance about how and when to use them when contributing to Carbon rather than
+being reactive.
+
+## Background
+
+-   [LLVM Developer Policy guidance on AI generated code](https://llvm.org/docs/DeveloperPolicy.html#ai-generated-contributions)
+
+## Proposal
+
+All submissions to Carbon need to follow our Contributor License Agreement
+(CLA), in which contributors agree that their contribution is an original work
+of authorship. This doesn’t prohibit the use of coding assistance tools, but
+what’s submitted does need to be a contributor’s original creation.
+
+Carbon's license was also selected specifically to maintain full compatibility
+between any contributions to Carbon and contributions to LLVM so that we can
+potentially move things between these projects easily. We want the same to be
+true regarding the use of AI-based coding tools, and so any contributions to
+Carbon should also abide by the guidance in the
+[LLVM Developer Policy around AI generated code](https://llvm.org/docs/DeveloperPolicy.html#ai-generated-contributions)
+
+This proposal updates our contributing documentation to contain both these
+points.
+
+## Rationale
+
+-   [Community and culture](/docs/project/goals.md#community-and-culture)
+    -   Explicitly documenting what is and isn't required when contributing to
+        Carbon makes the project more open and welcoming to new contributors.
+
+## Alternatives considered
+
+### Place more restrictions around AI-based tool usage when contributing
+
+We could consider adopting more restrictions on how AI-based tools can be used
+as part of contributing to Carbon. However, at this point we don't have a
+compelling rationale for this.
+
+There are real concerns around the quality of code output from AI-based tools in
+some cases. However, we should not rely on avoiding the tools to provide
+protection from low-quality code. Instead, as we already do, we have a system of
+code review, coding standards, and extensive testing to ensure high-quality
+contributions regardless of the tools used. **The quality, correctness, and
+utility expectations of contributions are true regardless of which tools are
+used as part of authoring the contribution.**
+
+We have also seen abuse where large volumes of automatically generated
+"contributions" have been sent to projects, overwhelming their community. Again,
+this is never OK, regardless of which tools are used to achieve it. We hold the
+contributors responsible for using any and all tools responsibly and making
+useful and constructive contributions with them.
+
+Last but not least, we also understand that there may contributors who do not
+wish to use these tools. Currently, we are not proposing any tools in the
+required workflow of the project.