Add an LLM policy for rust-lang/rust

src/SUMMARY.md

@@ -87,6 +87,7 @@
     - [Project groups](./governance/project-groups.md)
 - [Policies](./policies/index.md)
     - [Crate ownership policy](./policies/crate-ownership.md)
+    - [LLM usage policy](./policies/llm-usage.md)
 - [Infrastructure](./infra/index.md)
     - [Other Installation Methods](./infra/other-installation-methods.md)
     - [Archive of Rust Stable Standalone Installers](./infra/archive-stable-version-installers.md)

src/how-to-start-contributing.md

@@ -129,6 +129,8 @@ To achieve this goal, we want to build trust and respect of each other's time an
 - Please respect the reviewers' time: allow some days between reviews, only ask for reviews when your code compiles and tests pass, or give an explanation for why you are asking for a review at that stage (you can keep them in draft state until they're ready for review)
 - Try to keep comments concise, don't worry about a perfect written communication. Strive for clarity and being to the point
 
+See also our [LLM usage policy](./policies/llm-usage.md).
+
 [^1]: Free-Open Source Project, see: https://en.wikipedia.org/wiki/Free_and_open-source_software
 
 ### Different kinds of contributions

src/policies/llm-usage.md

@@ -0,0 +1,139 @@
+## LLM Usage Policy
+
+For additional information about the policy itself, see [the appendix](#appendix).
+
+### Overview
+
+Using an LLM while working on `rust-lang/rust` is conditionally allowed.
+However, we find it important to keep the following points in mind:
+
+- Many people find LLM-generated code and writing deeply unpleasant to read or review.
+- Many people find LLMs to be a significant aid to learning and discovery.
+- LLMs are a new technology, and we are still learning how to use, moderate, and improve them.
+  Since we're still learning, we have chosen an intentionally conservative policy that lets us maintain the standard of quality that Rust is known for.
+
+Therefore, the guidelines are roughly as follows:
+
+> It's fine to use LLMs to answer questions, analyze, distill, refine, check, suggest, review. But not to **create**.
+
+> LLMs work best when used as a tool to write *better*, not *faster*.
+
+#### Legend
+
+- ✅ Allowed
+- ❌ Banned
+- ⚠️ Allowed with caveats. Must disclose that an LLM was used.
+- ℹ️ Adds additional detail to the policy. These bullets are normative.
+
+### Rules
+
+#### ✅ Allowed
+The following are allowed.
+- Asking an LLM questions about an existing codebase.
+- Asking an LLM to summarize comments on an issue, PR, or RFC.
+    - ℹ️ This does not allow reposting the summary publicly. This only includes your own personal use.
+- Asking an LLM to privately review your code or writing.
+    - ℹ️ This does not apply to public comments. See "review bots" under ⚠️ below.
+- Writing dev-tools for your own personal use using an LLM, as long as you don't try to merge them into `rust-lang/rust`.
+- Using an LLM to discover bugs, as long as you personally verify the bug, write it up yourself, and disclose that an LLM was used.
+  Please refer to [our guidelines for fuzzers](https://rustc-dev-guide.rust-lang.org/fuzzing.html#guidelines).
+    - ℹ️ This also includes reviewers who use LLMs to discover flaws in unmerged code.
+
+#### ❌ Banned
+The following are banned.
+- Comments from a personal user account that are originally authored by an LLM.
+    - ℹ️ This also applies to issue bodies and PR descriptions.
+    - ℹ️ See also "machine-translation" in ⚠️ below.
+- Documentation that is originally authored by an LLM.
+    - ℹ️ This includes non-trivial source comments, such as doc-comments or multiple paragraphs of non-doc-comments.
+    - ℹ️ This includes compiler diagnostics.
+- Code changes that are originally authored by an LLM.
+    - ℹ️ This does not include "trivial" changes that do not meet the [threshold of originality](https://fsfe.org/news/2025/news-20250515-01.en.html), which fall under ⚠️ below.
+    - ℹ️ Be cautious about PRs that consist solely of trivial changes.
+      See also [the compiler team's typo fix policy](https://rustc-dev-guide.rust-lang.org/contributing.html#writing-documentation:~:text=Please%20notice%20that%20we%20don%E2%80%99t%20accept%20typography%2Fspellcheck%20fixes%20to%20internal%20documentation).
+    - See also "learning from an LLM's solution" in ⚠️ below.
+- Treating an LLM review as a sufficient condition to merge or reject a change.
+  LLM reviews, if enabled by a team, **must** be advisory-only.
+  Teams can have a policy that code can be merged without review, and they can have a policy that code must be reviewed by at least one person,
+  but they may not have a policy that an LLM review substitutes for a human review.
+    - ℹ️ See "review bots" in ⚠️ below.
+    - ℹ️ An LLM review does not substitute for self-review. Authors are expected to review their own code before posting and after each change.
+
+#### ⚠️ Allowed with caveats
+The following are decided on a case-by-case basis.
+In general, new contributors will be scrutinized more heavily than existing contributors,
+since they haven't yet established trust with their reviewers.
+
+- Using an LLM to generate a solution to an issue, learning from its solution, and then rewriting it from scratch in your own style.
+- Using machine-translation (e.g. Google Translate) from your native language without posting your original message.
+  Doing so can introduce new miscommunications that weren't there originally, and prevents someone who speaks the language from providing a better translation.
+    - ℹ️ Posting both your original message and the translated version is always ok, but you must still disclose that machine-translation was used.
+- Using an LLM as a "review bot" for PRs.
+    - ℹ️ Review bots **must** have a separate GitHub account that marks them as an LLM.
+      You **must not** post (or allow a tool to post) LLM reviews verbatim on your personal account unless clearly quoted with your own personal interpretation of the bot's analysis.
+    - ℹ️ Review bot accounts must be blockable by individual users via the standard GitHub user-blocking mechanism. (Note that some GitHub "app" accounts post comments that look like users but cannot be blocked.)
+    - ℹ️ Review bots that post without being approved by a maintainer will be banned.
+    - ℹ️ If a more reliable tool, such as a linter or formatter, already exists for the language you're writing, we strongly suggest using that tool instead of or in addition to the LLM.
+    - ℹ️ Configure LLM review tools to reduce false positives and excessive focus on trivialities, as these are common, exhausting failure modes.
+    - ℹ️ LLM comments **must not** be blocking; reviewers must indicate which comments they want addressed. It's ok to require a *response* to each comment but the response can be "the bot's wrong here".
+        - In other words, reviewers must explicitly endorse an LLM comment before blocking a PR. They are responsible for their own analysis of the LLM's comment and cannot treat it as a CI failure.
+    - ℹ️ This does not apply to private use of an LLM for reviews; see ✅ above.
+
+All of these **must** disclose that an LLM was used.
+
+## Appendix
+
+### Moderation policy
+#### It's not your job to play detective
+["The optimal amount of fraud is not zero"](https://www.bitsaboutmoney.com/archive/optimal-amount-of-fraud/).
+Do not try to be the police for whether someone has used an LLM.
+If it's clear they've broken the rules, point them to this policy; if it's borderline, report it to the mods and move on.
+
+#### Be honest
+Conversely, lying about whether or how you've used an LLM is considered a [code of conduct](https://rust-lang.org/policies/code-of-conduct/) violation.
+If you are not sure where something you would like to do falls in this policy, please talk to the [moderation team](mailto:rust-mods@rust-lang.org).
+Don't try to hide it.
+
+#### Penalties
+The policies below follow the same guidelines as the code of conduct:
+Violations will first result in a warning, and repeated violations may result in a ban.
+- 🔨 Comments from a personal account originally authored by an LLM
+- 🔨 Violations of the "Be honest" section
+
+Other violations are left up to the discretion of reviewers and moderators.
+For most cases we recommend closing and locking the PR or issue, but not escalating further.
+
+Using an LLM does **not** mean it's ok to harrass a contributor.
+All contributors must be treated with respect.
+The code-of-conduct applies to *all* conversations in the Rust project.
+
+### Responsibility
+
+Your contributions are your responsibility; you cannot place any blame on an LLM.
+- ℹ️ This includes when asking people to address review comments originally authored by an LLM. See "review bots" under ⚠️ above.
+
+### The meaning of "originally authored"
+
+This document uses the phrase "originally authored" to mean "text that was generated by an LLM (and then possibly edited by a human)".
+No amount of editing can change authorship; authorship sets the initial style and it is very hard to change once it's set.
+
+For more background about analogous reasoning, see ["What Colour are your bits?"](https://ansuz.sooke.bc.ca/entry/23)
+
+### Non-exhaustive policy
+
+This policy does not aim to be exhaustive.
+If you have a use of LLMs in mind that isn't on this list, judge it in the spirit of this overview:
+- Usages that do not use LLMs for creation and do not show LLM output to another human are likely allowed ✅ 
+- Usages that use LLMs for creation or show LLM output to another human are likely banned ❌
+
+### Conditions for modification or dissolution
+This policy is not set in stone, and we can evolve it as we gain more experience working with LLMs.
+
+Minor changes, such as typo fixes, only require a normal PR approval.
+Major changes, such as adding a new rule or cancelling an existing rule, require
+a simple majority of members of teams using rust-lang/rust (without concerns).
+
+This policy can be dissolved in a few ways:
+
+- An accepted FCP by teams using rust-lang/rust.
+- An objective concern raised about active harm the policy is having on the reputation of Rust, with evidence; as decided by a leadership council FCP.