fix: Preserve multiline UP040 alias grouping

Parenthesize multiline binary and boolean expressions when converting TypeAliasType assignments to type statements. The call syntax previously provided grouping that was lost by the fix, producing invalid Python.

See #28102

Author: fredrikniche

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP040.py

@@ -132,3 +132,11 @@ class Foo:
 # Test case for TypeVar with default - should be converted when preview mode is enabled
 T_default = TypeVar("T_default", default=int)
 DefaultList: TypeAlias = list[T_default]
+
+# Preserve parentheses around a multiline union in a TypeAliasType call.
+LongAlias = TypeAliasType(
+    "LongAlias",
+    int
+    | str
+    | float
+)

crates/ruff_linter/src/rules/pyupgrade/rules/pep695/non_pep695_type_alias.rs

@@ -193,6 +193,8 @@ pub(crate) fn non_pep695_type_alias_type(checker: &Checker, stmt: &StmtAssign) {
         value,
         &vars,
         TypeAliasKind::TypeAliasType,
+        parenthesized_range(value.into(), arguments.into(), checker.tokens())
+            .unwrap_or(value.range()),
     );
 }
 
@@ -247,6 +249,7 @@ pub(crate) fn non_pep695_type_alias(checker: &Checker, stmt: &StmtAnnAssign) {
         value,
         &vars,
         TypeAliasKind::TypeAlias,
+        parenthesized_range(value.into(), stmt.into(), checker.tokens()).unwrap_or(value.range()),
     );
 }
 
@@ -255,9 +258,10 @@ fn create_diagnostic(
     checker: &Checker,
     stmt: StmtRef,
     name: &Name,
-    value: &Expr,
+    value_expr: &Expr,
     type_vars: &[TypeVar],
     type_alias_kind: TypeAliasKind,
+    range_with_parentheses: TextRange,
 ) {
     // If any type variables have defaults, skip the rule unless
     // running with preview mode enabled and targeting Python 3.13+.
@@ -273,16 +277,22 @@ fn create_diagnostic(
     }
 
     let source = checker.source();
-    let tokens = checker.tokens();
     let comment_ranges = checker.comment_ranges();
 
-    let range_with_parentheses =
-        parenthesized_range(value.into(), stmt.into(), tokens).unwrap_or(value.range());
+    let value = &source[range_with_parentheses];
+    let value = if type_alias_kind == TypeAliasKind::TypeAliasType
+        && value.contains('\n')
+        && matches!(value_expr, Expr::BinOp(_) | Expr::BoolOp(_))
+    {
+        format!("({value})")
+    } else {
+        value.to_string()
+    };
 
     let content = format!(
         "type {name}{type_params} = {value}",
         type_params = DisplayTypeVars { type_vars, source },
-        value = &source[range_with_parentheses]
+        value = value,
     );
     let edit = Edit::range_replacement(content, stmt.range());
 

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__UP040.py.snap

@@ -436,3 +436,27 @@ help: Use the `type` keyword
 123 |     # comment1
     |
 note: This is an unsafe fix and may change runtime behavior
+
+UP040 [*] Type alias `LongAlias` uses `TypeAliasType` assignment instead of the `type` keyword
+   --> UP040.py:137:1
+    |
+136 |   # Preserve parentheses around a multiline union in a TypeAliasType call.
+137 | / LongAlias = TypeAliasType(
+138 | |     "LongAlias",
+139 | |     int
+140 | |     | str
+141 | |     | float
+142 | | )
+    | |_^
+help: Use the `type` keyword
+    |
+136 | # Preserve parentheses around a multiline union in a TypeAliasType call.
+    - LongAlias = TypeAliasType(
+    -     "LongAlias",
+    -     int
+137 + type LongAlias = (int
+138 |     | str
+    -     | float
+    - )
+139 +     | float)
+    |

crates/ruff_linter/src/rules/pyupgrade/snapshots/ruff_linter__rules__pyupgrade__tests__UP040.py__preview_diff.snap

@@ -56,10 +56,14 @@ UP040 [*] Type alias `DefaultList` uses `TypeAlias` annotation instead of the `t
 133 | T_default = TypeVar("T_default", default=int)
 134 | DefaultList: TypeAlias = list[T_default]
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+135 |
+136 | # Preserve parentheses around a multiline union in a TypeAliasType call.
+    |
 help: Use the `type` keyword
     |
 133 | T_default = TypeVar("T_default", default=int)
     - DefaultList: TypeAlias = list[T_default]
 134 + type DefaultList[T_default = int] = list[T_default]
+135 |
     |
 note: This is an unsafe fix and may change runtime behavior