Minor improvements

Author: cdce8p

mypy/checkexpr.py

@@ -3561,7 +3561,9 @@ def literal_expression_addition(self, e: OpExpr, left_type: Type) -> Type | None
         )
         if len(values) == 1:
             return LiteralType(values[0], self.named_type(lvalue[1]))
-        return UnionType([LiteralType(val, self.named_type(lvalue[1])) for val in values])
+        return make_simplified_union(
+            [LiteralType(val, self.named_type(lvalue[1])) for val in values]
+        )
 
     def visit_comparison_expr(self, e: ComparisonExpr) -> Type:
         """Type check a comparison expression.

test-data/unit/check-literal.test

@@ -2968,17 +2968,17 @@ from typing_extensions import Literal
 str_a: Literal["a"]
 str_b: Literal["b"]
 str_union_1: Literal["a", "b"]
-str_union_2: Literal["c", "d"]
+str_union_2: Literal["d", "c"]
 s: str
 int_1: Literal[1]
 int_2: Literal[2]
 int_union_1: Literal[1, 2]
-int_union_2: Literal[3, 4]
+int_union_2: Literal[4, 3]
 i: int
 bytes_a: Literal[b"a"]
 bytes_b: Literal[b"b"]
 bytes_union_1: Literal[b"a", b"b"]
-bytes_union_2: Literal[b"c", b"d"]
+bytes_union_2: Literal[b"d", b"c"]
 b: bytes
 
 misc_union: Literal["a", 1]