test: add union type tests

tests/test.rs

@@ -142,6 +142,11 @@ fn exec_typevar() -> Result<(), String> {
     expect("tests/typevar.py", 0, 3)
 }
 
+#[test]
+fn exec_union() -> Result<(), String> {
+    expect("tests/union.py", 0, 0)
+}
+
 #[test]
 fn exec_widening() -> Result<(), String> {
     expect("tests/widening.py", 0, 1)

tests/union.py

@@ -0,0 +1,9 @@
+s: str | bytes = ""
+s2 = s.capitalize()
+s3 = s2.center(1)
+
+s4: str | bytes | bytearray = ""
+_ = s4.__len__()
+
+def f(x: str | bytes):
+    return x.isalnum()