Deprecate UP027 (#12843)

Co-authored-by: Alex Waygood <[email protected]>
Closes #12754

Author: MichaReiser

crates/ruff_linter/src/codes.rs

@@ -510,7 +510,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pyupgrade, "024") => (RuleGroup::Stable, rules::pyupgrade::rules::OSErrorAlias),
         (Pyupgrade, "025") => (RuleGroup::Stable, rules::pyupgrade::rules::UnicodeKindPrefix),
         (Pyupgrade, "026") => (RuleGroup::Stable, rules::pyupgrade::rules::DeprecatedMockImport),
-        (Pyupgrade, "027") => (RuleGroup::Stable, rules::pyupgrade::rules::UnpackedListComprehension),
+        (Pyupgrade, "027") => (RuleGroup::Deprecated, rules::pyupgrade::rules::UnpackedListComprehension),
         (Pyupgrade, "028") => (RuleGroup::Stable, rules::pyupgrade::rules::YieldInForLoop),
         (Pyupgrade, "029") => (RuleGroup::Stable, rules::pyupgrade::rules::UnnecessaryBuiltinImport),
         (Pyupgrade, "030") => (RuleGroup::Stable, rules::pyupgrade::rules::FormatLiterals),

crates/ruff_linter/src/rules/pyupgrade/rules/unpacked_list_comprehension.rs

@@ -7,13 +7,17 @@ use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
 
+/// ## Deprecation
+/// There's no [evidence](https://github.com/astral-sh/ruff/issues/12754) that generators are
+/// meaningfully faster than list comprehensions when combined with unpacking.
+///
 /// ## What it does
 /// Checks for list comprehensions that are immediately unpacked.
 ///
 /// ## Why is this bad?
 /// There is no reason to use a list comprehension if the result is immediately
-/// unpacked. Instead, use a generator expression, which is more efficient as
-/// it avoids allocating an intermediary list.
+/// unpacked. Instead, use a generator expression, which avoids allocating
+/// an intermediary list.
 ///
 /// ## Example
 /// ```python