Added isinstance tests in static analysis.

test/static_analysis/builtins.py

@@ -0,0 +1,11 @@
+# ----------
+# isinstance
+# ----------
+
+isinstance(1, int)
+isinstance(1, (int, str))
+
+#! 14 type-error-isinstance
+isinstance(1, 1)
+#! 14 type-error-isinstance
+isinstance(1, [int, str])