Add bug testcase for GH-337

tests/api/test-bug-is-primitive-invalid-index-gh337.c

@@ -0,0 +1,52 @@
+/*
+ *  Bug in duk_is_primitive() prior to Duktape 1.3.0: returns 1 for invalid
+ *  index.
+ *
+ *  https://github.com/svaarala/duktape/issues/337
+ */
+
+/*===
+*** test_1 (duk_safe_call)
+0
+final top: 0
+==> rc=0, result='undefined'
+*** test_2 (duk_safe_call)
+0
+final top: 0
+==> rc=0, result='undefined'
+*** test_3 (duk_safe_call)
+1
+0
+final top: 1
+==> rc=0, result='undefined'
+===*/
+
+static duk_ret_t test_1(duk_context *ctx) {
+	printf("%ld\n", (long) duk_is_primitive(ctx, -1));
+
+	printf("final top: %ld\n", (long) duk_get_top(ctx));
+	return 0;
+}
+
+static duk_ret_t test_2(duk_context *ctx) {
+	printf("%ld\n", (long) duk_is_primitive(ctx, DUK_INVALID_INDEX));
+
+	printf("final top: %ld\n", (long) duk_get_top(ctx));
+	return 0;
+}
+
+static duk_ret_t test_3(duk_context *ctx) {
+	duk_push_null(ctx);
+
+	printf("%ld\n", (long) duk_is_primitive(ctx, 0));  /* valid */
+	printf("%ld\n", (long) duk_is_primitive(ctx, 1));  /* invalid */
+
+	printf("final top: %ld\n", (long) duk_get_top(ctx));
+	return 0;
+}
+
+void test(duk_context *ctx) {
+	TEST_SAFE_CALL(test_1);
+	TEST_SAFE_CALL(test_2);
+	TEST_SAFE_CALL(test_3);
+}