From 2f2bcbb590ba3cb67251387c996e7cbe1d1be9aa Mon Sep 17 00:00:00 2001
From: Micha Reiser <micha@reiser.io>
Date: Thu, 13 Mar 2025 08:42:14 +0100
Subject: [PATCH] [`pyupgrade`]: Deprecate `non-pep604-isinstance` (`UP038`)
 (#16681)

## Summary

This PR deprecates UP038. Using PEP 604 syntax in `isinstance` and
`issubclass` calls isn't a recommended pattern (or community agreed best
practice)
and it negatively impacts performance.

Resolves https://github.com/astral-sh/ruff/issues/7871

## Test Plan

I tested that selecting `UP038` results in a warning in no-preview mode
and an error in preview mode
---
 crates/ruff_linter/src/codes.rs                            | 2 +-
 .../src/rules/pyupgrade/rules/use_pep604_isinstance.rs     | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/crates/ruff_linter/src/codes.rs b/crates/ruff_linter/src/codes.rs
index 28e1346a5d..68fe4a9db4 100644
--- a/crates/ruff_linter/src/codes.rs
+++ b/crates/ruff_linter/src/codes.rs
@@ -532,7 +532,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pyupgrade, "035") => (RuleGroup::Stable, rules::pyupgrade::rules::DeprecatedImport),
         (Pyupgrade, "036") => (RuleGroup::Stable, rules::pyupgrade::rules::OutdatedVersionBlock),
         (Pyupgrade, "037") => (RuleGroup::Stable, rules::pyupgrade::rules::QuotedAnnotation),
-        (Pyupgrade, "038") => (RuleGroup::Stable, rules::pyupgrade::rules::NonPEP604Isinstance),
+        (Pyupgrade, "038") => (RuleGroup::Deprecated, rules::pyupgrade::rules::NonPEP604Isinstance),
         (Pyupgrade, "039") => (RuleGroup::Stable, rules::pyupgrade::rules::UnnecessaryClassParentheses),
         (Pyupgrade, "040") => (RuleGroup::Stable, rules::pyupgrade::rules::NonPEP695TypeAlias),
         (Pyupgrade, "041") => (RuleGroup::Stable, rules::pyupgrade::rules::TimeoutErrorAlias),
diff --git a/crates/ruff_linter/src/rules/pyupgrade/rules/use_pep604_isinstance.rs b/crates/ruff_linter/src/rules/pyupgrade/rules/use_pep604_isinstance.rs
index 067ee2acbd..4da657f473 100644
--- a/crates/ruff_linter/src/rules/pyupgrade/rules/use_pep604_isinstance.rs
+++ b/crates/ruff_linter/src/rules/pyupgrade/rules/use_pep604_isinstance.rs
@@ -33,6 +33,12 @@ impl CallKind {
     }
 }
 
+/// ## Deprecation
+/// This rule was deprecated as using [PEP 604] syntax in `isinstance` and `issubclass` calls
+/// isn't recommended practice, and it incorrectly suggests that other typing syntaxes like [PEP 695]
+/// would be supported by `isinstance` and `issubclass`. Using the [PEP 604] syntax
+/// is also slightly slower.
+///
 /// ## What it does
 /// Checks for uses of `isinstance` and `issubclass` that take a tuple
 /// of types for comparison.
@@ -64,6 +70,7 @@ impl CallKind {
 /// - [Python documentation: `issubclass`](https://docs.python.org/3/library/functions.html#issubclass)
 ///
 /// [PEP 604]: https://peps.python.org/pep-0604/
+/// [PEP 695]: https://peps.python.org/pep-0695/
 #[derive(ViolationMetadata)]
 pub(crate) struct NonPEP604Isinstance {
     kind: CallKind,