Special-case ClassLiteral | ClassLiteral

Author: dcreager

crates/red_knot_python_semantic/resources/mdtest/binary/classes.md

@@ -13,7 +13,7 @@ python-version = "3.10"
 class A: ...
 class B: ...
 
-reveal_type(A | B)  # revealed: UnionType
+reveal_type(A | B)  # revealed: Literal[A, B]
 ```
 
 ## Union of two classes (prior to 3.10)

crates/red_knot_python_semantic/src/types/infer.rs

@@ -70,7 +70,7 @@ use crate::types::{
 };
 use crate::unpack::Unpack;
 use crate::util::subscript::{PyIndex, PySlice};
-use crate::Db;
+use crate::{Db, Program, PythonVersion};
 
 use super::context::{InferContext, WithDiagnostics};
 use super::diagnostic::{
@@ -3361,6 +3361,12 @@ impl<'db> TypeInferenceBuilder<'db> {
             (Type::Never, _, _) | (_, Type::Never, _) => Some(Type::Never),
             (Type::Unknown, _, _) | (_, Type::Unknown, _) => Some(Type::Unknown),
 
+            (Type::ClassLiteral(_), Type::ClassLiteral(_), ast::Operator::BitOr)
+                if Program::get(self.db()).python_version(self.db()) >= PythonVersion::PY310 =>
+            {
+                Some(UnionType::from_elements(self.db(), [left_ty, right_ty]))
+            }
+
             (Type::IntLiteral(n), Type::IntLiteral(m), ast::Operator::Add) => Some(
                 n.checked_add(m)
                     .map(Type::IntLiteral)