py/objtype: Fix assertion failures in mp_obj_new_type by checking types.

Fixes assertion failures when the arguments to type() were not of valid
types, e.g., when making calls like:

    type("", (), 3)
    type("", 3, {})

1 files changed, 18 insertions, 0 deletions

diff --git a/tests/basics/builtin_type.py b/tests/basics/builtin_type.py
index 83c45c64b..c5fb36626 100644
--- a/tests/basics/builtin_type.py
+++ b/tests/basics/builtin_type.py
@@ -11,3 +11,21 @@ try:
     type(1, 2)
 except TypeError:
     print('TypeError')
+
+# second arg should be a tuple
+try:
+    type('abc', None, None)
+except TypeError:
+    print('TypeError')
+
+# third arg should be a dict
+try:
+    type('abc', (), None)
+except TypeError:
+    print('TypeError')
+
+# elements of second arg (the bases) should be types
+try:
+    type('abc', (1,), {})
+except TypeError:
+    print('TypeError')