py: Simplify and remove redundant code for __iter__ method lookup.

py/obj.h

@@ -285,7 +285,7 @@ struct _mp_obj_type_t {
                                     // value=MP_OBJ_NULL means delete, value=MP_OBJ_SENTINEL means load, else store
                                     // can return MP_OBJ_NULL if op not supported
 
-    mp_fun_1_t getiter;
+    mp_fun_1_t getiter;             // corresponds to __iter__ special method
     mp_fun_1_t iternext; // may return MP_OBJ_STOP_ITERATION as an optimisation instead of raising StopIteration() (with no args)
 
     mp_buffer_p_t buffer_p;

py/objtype.c

@@ -644,21 +644,13 @@ STATIC mp_obj_t instance_getiter(mp_obj_t self_in) {
     };
     mp_obj_class_lookup(&lookup, self->base.type);
     if (member[0] == MP_OBJ_NULL) {
-        // This kinda duplicates code in mp_getiter()
-        lookup.attr = MP_QSTR___getitem__;
-        lookup.meth_offset = 0; // TODO
-        mp_obj_class_lookup(&lookup, self->base.type);
-        if (member[0] != MP_OBJ_NULL) {
-            // __getitem__ exists, create an iterator
-            return mp_obj_new_getitem_iter(member);
-        }
         return MP_OBJ_NULL;
-    }
-    if (member[0] == MP_OBJ_SENTINEL) {
+    } else if (member[0] == MP_OBJ_SENTINEL) {
         mp_obj_type_t *type = mp_obj_get_type(self->subobj[0]);
         return type->getiter(self->subobj[0]);
+    } else {
+        return mp_call_method_n_kw(0, 0, member);
     }
-    return mp_call_method_n_kw(0, 0, member);
 }
 
 STATIC mp_int_t instance_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {

py/runtime.c

@@ -957,37 +957,31 @@ void mp_store_attr(mp_obj_t base, qstr attr, mp_obj_t value) {
 
 mp_obj_t mp_getiter(mp_obj_t o_in) {
     assert(o_in);
+
+    // check for native getiter (corresponds to __iter__)
     mp_obj_type_t *type = mp_obj_get_type(o_in);
     if (type->getiter != NULL) {
         mp_obj_t iter = type->getiter(o_in);
-        if (iter == MP_OBJ_NULL) {
-            goto not_iterable;
+        if (iter != MP_OBJ_NULL) {
+            return iter;
         }
-        return iter;
+    }
+
+    // check for __getitem__
+    mp_obj_t dest[2];
+    mp_load_method_maybe(o_in, MP_QSTR___getitem__, dest);
+    if (dest[0] != MP_OBJ_NULL) {
+        // __getitem__ exists, create and return an iterator
+        return mp_obj_new_getitem_iter(dest);
+    }
+
+    // object not iterable
+    if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError,
+            "object not iterable"));
     } else {
-        // check for __iter__ method
-        mp_obj_t dest[2];
-        mp_load_method_maybe(o_in, MP_QSTR___iter__, dest);
-        if (dest[0] != MP_OBJ_NULL) {
-            // __iter__ exists, call it and return its result
-            return mp_call_method_n_kw(0, 0, dest);
-        } else {
-            mp_load_method_maybe(o_in, MP_QSTR___getitem__, dest);
-            if (dest[0] != MP_OBJ_NULL) {
-                // __getitem__ exists, create an iterator
-                return mp_obj_new_getitem_iter(dest);
-            } else {
-                // object not iterable
-not_iterable:
-                if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
-                    nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError,
-                        "object not iterable"));
-                } else {
-                    nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError,
-                        "'%s' object is not iterable", mp_obj_get_type_str(o_in)));
-                }
-            }
-        }
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError,
+            "'%s' object is not iterable", mp_obj_get_type_str(o_in)));
     }
 }
 

tests/basics/iter0.py

@@ -0,0 +1,6 @@
+# builtin type that is not iterable
+try:
+    for i in 1:
+        pass
+except TypeError:
+    print('TypeError')

tests/basics/iter1.py

@@ -1,5 +1,14 @@
 # test user defined iterators
 
+# this class is not iterable
+class NotIterable:
+    pass
+try:
+    for i in NotIterable():
+        pass
+except TypeError:
+    print('TypeError')
+
 class MyStopIteration(StopIteration):
     pass