Skip PEP 695 fixes for TypeVars with starred constraints (UP040, UP046, UP047, RUF053)

Author: LckyLke

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

@@ -132,3 +132,8 @@ 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]
+
+# TypeVar with starred constraints has no PEP 695 equivalent
+constraints = (int, str)
+T_starred = TypeVar("T_starred", *constraints)
+StarredList: TypeAlias = list[T_starred]

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP046_0.py

@@ -142,3 +142,12 @@ class DefaultOnlyTypeVar(Generic[W]):  # -> [W = int]
 class Outer:
     class Inner(Generic[T]):
         var: T
+
+
+# TypeVar with starred constraints has no PEP 695 equivalent
+constraints = (int, str)
+U = TypeVar("U", *constraints)
+
+
+class StarredConstraints(Generic[U]):
+    var: U

crates/ruff_linter/resources/test/fixtures/pyupgrade/UP047_0.py

@@ -63,3 +63,11 @@ def multi_param(t: list[T], c: Callable[[T], None]) -> T:
 def outer():
     def inner(t: T) -> T:
         return t
+
+
+constraints = (int, str)
+U = TypeVar("U", *constraints)
+
+
+def starred_constraints(var: U) -> U:
+    return var

crates/ruff_linter/resources/test/fixtures/ruff/RUF053.py

@@ -101,6 +101,12 @@ class C[T: [a]](Generic[_A]): ...
 # class C[T: (*a,)](Generic[_A]): ...        # TODO: Uncomment this
 
 
+# TypeVar with starred constraints has no PEP 695 equivalent
+constraints = (str, bytes)
+_H = TypeVar('_H', *constraints)
+class C[T](Generic[_H]): ...
+
+
 ### No errors
 
 class C(Generic[_A]): ...

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

@@ -93,6 +93,16 @@ impl TypeVar<'_> {
             source,
         }
     }
+
+    /// Returns `true` for a starred constraint like `TypeVar("T", *constraints)`, which has no
+    /// equivalent in PEP 695 syntax.
+    pub(crate) fn has_starred_constraint(&self) -> bool {
+        matches!(
+            &self.restriction,
+            Some(TypeVarRestriction::Constraint(constraints))
+                if constraints.iter().any(|constraint| constraint.is_starred_expr())
+        )
+    }
 }
 
 impl Display for DisplayTypeVar<'_> {
@@ -399,7 +409,7 @@ fn check_type_vars<'a>(vars: Vec<TypeVar<'a>>, checker: &Checker) -> Option<Vec<
         return None;
     }
 
-    if non_default_follows_default(&vars) {
+    if non_default_follows_default(&vars) || vars.iter().any(TypeVar::has_starred_constraint) {
         return None;
     }
 

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

@@ -268,7 +268,9 @@ fn create_diagnostic(
         return;
     }
 
-    if non_default_follows_default(type_vars) {
+    if non_default_follows_default(type_vars)
+        || type_vars.iter().any(TypeVar::has_starred_constraint)
+    {
         return;
     }
 

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 | # TypeVar with starred constraints has no PEP 695 equivalent
+    |
 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

crates/ruff_linter/src/rules/ruff/rules/class_with_mixed_type_vars.rs

@@ -231,6 +231,7 @@ fn generic_arguments_to_type_vars<'a>(
 ///
 /// * If `type_var` is a `TypeVar`:
 ///     * It must not be unpacked
+///     * It must not have a starred constraint
 /// * If `type_var` is a `TypeVarTuple`:
 ///     * It must be unpacked
 ///     * It must not have any restrictions
@@ -248,5 +249,9 @@ fn type_var_is_valid(type_var: &TypeVar, unpacked: bool) -> bool {
         return false;
     }
 
+    if type_var.has_starred_constraint() {
+        return false;
+    }
+
     true
 }

crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__class-with-mixed-type-vars_RUF053.py.snap

@@ -449,3 +449,12 @@ help: Remove `Generic` base class
 97 |
    |
 note: This is an unsafe fix and may change runtime behavior
+
+RUF053 Class with type parameter list inherits from `Generic`
+   --> RUF053.py:107:12
+    |
+105 | constraints = (str, bytes)
+106 | _H = TypeVar('_H', *constraints)
+107 | class C[T](Generic[_H]): ...
+    |            ^^^^^^^^^^^
+help: Remove `Generic` base class