py: Fix builtin callable so it checks user-defined instances correctly.

Addresses issue #953.

py/obj.c

@@ -34,6 +34,7 @@
 #include "misc.h"
 #include "qstr.h"
 #include "obj.h"
+#include "objtype.h"
 #include "mpz.h"
 #include "objint.h"
 #include "runtime0.h"
@@ -145,7 +146,11 @@ bool mp_obj_is_true(mp_obj_t arg) {
 }
 
 bool mp_obj_is_callable(mp_obj_t o_in) {
-    return mp_obj_get_type(o_in)->call != NULL;
+    mp_call_fun_t call = mp_obj_get_type(o_in)->call;
+    if (call != mp_obj_instance_call) {
+        return call != NULL;
+    }
+    return mp_obj_instance_is_callable(o_in);
 }
 
 mp_int_t mp_obj_hash(mp_obj_t o_in) {

py/objtype.c

@@ -583,7 +583,7 @@ STATIC mp_obj_t instance_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value
     }
 }
 
-STATIC mp_obj_t instance_call(mp_obj_t self_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
+bool mp_obj_instance_is_callable(mp_obj_t self_in) {
     mp_obj_instance_t *self = self_in;
     mp_obj_t member[2] = {MP_OBJ_NULL};
     struct class_lookup_data lookup = {
@@ -593,6 +593,19 @@ STATIC mp_obj_t instance_call(mp_obj_t self_in, mp_uint_t n_args, mp_uint_t n_kw
         .dest = member,
     };
     mp_obj_class_lookup(&lookup, self->base.type);
+    return member[0] != MP_OBJ_NULL;
+}
+
+mp_obj_t mp_obj_instance_call(mp_obj_t self_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
+    mp_obj_instance_t *self = self_in;
+    mp_obj_t member[2] = {MP_OBJ_NULL, MP_OBJ_NULL};
+    struct class_lookup_data lookup = {
+        .obj = self,
+        .attr = MP_QSTR___call__,
+        .meth_offset = offsetof(mp_obj_type_t, call),
+        .dest = member,
+    };
+    mp_obj_class_lookup(&lookup, self->base.type);
     if (member[0] == MP_OBJ_NULL) {
         nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "'%s' object is not callable", mp_obj_get_type_str(self_in)));
     }
@@ -777,7 +790,7 @@ mp_obj_t mp_obj_new_type(qstr name, mp_obj_t bases_tuple, mp_obj_t locals_dict)
     o->load_attr = instance_load_attr;
     o->store_attr = instance_store_attr;
     o->subscr = instance_subscr;
-    o->call = instance_call;
+    o->call = mp_obj_instance_call;
     o->getiter = instance_getiter;
     o->bases_tuple = bases_tuple;
     o->locals_dict = locals_dict;

py/objtype.h

@@ -32,3 +32,7 @@ typedef struct _mp_obj_instance_t {
     mp_obj_t subobj[];
     // TODO maybe cache __getattr__ and __setattr__ for efficient lookup of them
 } mp_obj_instance_t;
+
+// these need to be exposed so mp_obj_is_callable can work correctly
+bool mp_obj_instance_is_callable(mp_obj_t self_in);
+mp_obj_t mp_obj_instance_call(mp_obj_t self_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args);

tests/basics/builtin_callable.py

@@ -1,5 +1,43 @@
-import sys
+# test builtin callable
+
+# primitives should not be callable
+print(callable(None))
 print(callable(1))
+print(callable([]))
 print(callable("dfsd"))
-print(callable(callable))
+
+# modules should not be callabe
+import sys
 print(callable(sys))
+
+# builtins should be callable
+print(callable(callable))
+
+# lambdas should be callable
+print(callable(lambda:None))
+
+# user defined functions should be callable
+def f():
+    pass
+print(callable(f))
+
+# types should be callable, but not instances
+class A:
+    pass
+print(callable(A))
+print(callable(A()))
+
+# instances with __call__ method should be callable
+class B:
+    def __call__(self):
+        pass
+print(callable(B()))
+
+# this checks internal use of callable when extracting members from an instance
+class C:
+    def f(self):
+        return "A.f"
+class D:
+    g = C() # g is a value and is not callable
+print(callable(D().g))
+print(D().g.f())