Merge commit '7e5867' into refcounting

src/runtime/import.cpp

@@ -222,8 +222,15 @@ SearchResult findModule(const std::string& name, BoxedString* full_name, BoxedLi
     llvm::SmallString<128> joined_path;
     for (int i = 0; i < path_list->size; i++) {
         Box* _p = path_list->elts->elts[i];
-        if (_p->cls != str_cls)
+        if (isSubclass(_p->cls, unicode_cls)) {
+            _p = PyUnicode_AsEncodedString(_p, Py_FileSystemDefaultEncoding, NULL);
+            if (_p == NULL) {
                 continue;
+            }
+        }
+        if (!isSubclass(_p->cls, str_cls)) {
+            continue;
+        }
         BoxedString* p = static_cast<BoxedString*>(_p);
 
         joined_path.clear();
@@ -697,7 +704,7 @@ static int isdir(const char* path) {
 Box* nullImporterInit(Box* self, Box* _path) {
     RELEASE_ASSERT(self->cls == null_importer_cls, "");
 
-    if (_path->cls != str_cls)
+    if (!isSubclass(_path->cls, str_cls))
         raiseExcHelper(TypeError, "must be string, not %s", getTypeName(_path));
 
     BoxedString* path = (BoxedString*)_path;

src/runtime/types.cpp

@@ -4152,6 +4152,7 @@ void setupRuntime() {
     slice_cls->giveAttr("step", new BoxedMemberDescriptor(BoxedMemberDescriptor::OBJECT, offsetof(BoxedSlice, step)));
     slice_cls->freeze();
     slice_cls->tp_compare = (cmpfunc)slice_compare;
+    slice_cls->tp_flags &= ~Py_TPFLAGS_BASETYPE;
 
     static PyMappingMethods attrwrapper_as_mapping;
     attrwrapper_cls->tp_as_mapping = &attrwrapper_as_mapping;

test/tests/builtin_type_not_subclassable.py

+# should_error
+class foo(slice):
+   pass

test/tests/sys_path_str.py

+import sys
+sys.path.append("test_package")
+import import_target

test/tests/sys_path_str_subclass.py

+import sys
+class TestClass(str):
+    pass
+t = TestClass("test_package")
+sys.path.append(t)
+import import_target

test/tests/sys_path_unicode.py

+import sys
+sys.path.append(u"test_package")
+import import_target

test/tests/sys_path_unicode_subclass.py

+import sys
+class TestClass(unicode):
+    pass
+t = TestClass("test_package")
+sys.path.append(t)
+import import_target