Add Python 3.13 guard

crates/ty_python_semantic/resources/mdtest/scopes/class_implicit_attrs.md

@@ -2,17 +2,45 @@
 
 ## Class body implicit attributes
 
-Python makes certain names available implicitly inside class body scopes. These are `__qualname__`,
-`__module__`, and `__firstlineno__`, as documented at
+Python makes certain names available implicitly inside class body scopes. These are `__qualname__`
+and `__module__`, as documented at
 <https://docs.python.org/3/reference/datamodel.html#creating-the-class-object>.
 
 ```py
 class Foo:
     reveal_type(__qualname__)  # revealed: str
     reveal_type(__module__)  # revealed: str
+```
+
+## `__firstlineno__` (Python 3.13+)
+
+Python 3.13 added `__firstlineno__` to the class body namespace.
+
+### Available in Python 3.13+
+
+```toml
+[environment]
+python-version = "3.13"
+```
+
+```py
+class Foo:
     reveal_type(__firstlineno__)  # revealed: int
 ```
 
+### Not available in Python 3.12 and earlier
+
+```toml
+[environment]
+python-version = "3.12"
+```
+
+```py
+class Foo:
+    # error: [unresolved-reference]
+    __firstlineno__
+```
+
 ## Nested classes
 
 These implicit attributes are also available in nested classes, and refer to the nested class:
@@ -32,17 +60,32 @@ within the class body:
 ```py
 __qualname__ = 42
 __module__ = 42
-__firstlineno__ = "not an int"
 
 class Foo:
     # Inside the class body, these are the implicit class attributes
     reveal_type(__qualname__)  # revealed: str
     reveal_type(__module__)  # revealed: str
-    reveal_type(__firstlineno__)  # revealed: int
 
 # Outside the class, the globals are visible
 reveal_type(__qualname__)  # revealed: Literal[42]
 reveal_type(__module__)  # revealed: Literal[42]
+```
+
+## `__firstlineno__` has priority over globals (Python 3.13+)
+
+The same applies to `__firstlineno__` on Python 3.13+:
+
+```toml
+[environment]
+python-version = "3.13"
+```
+
+```py
+__firstlineno__ = "not an int"
+
+class Foo:
+    reveal_type(__firstlineno__)  # revealed: int
+
 reveal_type(__firstlineno__)  # revealed: Literal["not an int"]
 ```
 

crates/ty_python_semantic/src/place.rs

@@ -1,4 +1,5 @@
 use ruff_db::files::File;
+use ruff_python_ast::PythonVersion;
 
 use crate::dunder_all::dunder_all_names;
 use crate::module_resolver::{KnownModule, file_to_module, resolve_module_confident};
@@ -1646,17 +1647,11 @@ pub(crate) fn class_body_implicit_symbol<'db>(
     name: &str,
 ) -> PlaceAndQualifiers<'db> {
     match name {
-        // __qualname__ is the fully-qualified name of the class
         "__qualname__" => Place::bound(KnownClass::Str.to_instance(db)).into(),
-
-        // __module__ is the module name where the class is defined
         "__module__" => Place::bound(KnownClass::Str.to_instance(db)).into(),
-
-        // __firstlineno__ was added in Python 3.13, but we don't version-check since
-        // it's always available in the class body namespace (just the __firstlineno__
-        // attribute on the class itself may not be present)
-        "__firstlineno__" => Place::bound(KnownClass::Int.to_instance(db)).into(),
-
+        "__firstlineno__" if Program::get(db).python_version(db) >= PythonVersion::PY313 => {
+            Place::bound(KnownClass::Int.to_instance(db)).into()
+        }
         _ => Place::Undefined.into(),
     }
 }