py/obj: Add support for __int__ special method.

Based on the discussion, this special method is available unconditionally,
as converting to int is a common operation.

1 files changed, 16 insertions, 4 deletions

diff --git a/py/runtime.c b/py/runtime.c
index 33c4c1822..e512b8b0d 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -228,6 +228,7 @@ mp_obj_t mp_unary_op(mp_unary_op_t op, mp_obj_t arg) {
             case MP_UNARY_OP_HASH:
                 return arg;
             case MP_UNARY_OP_POSITIVE:
+            case MP_UNARY_OP_INT:
                 return arg;
             case MP_UNARY_OP_NEGATIVE:
                 // check for overflow
@@ -265,12 +266,23 @@ mp_obj_t mp_unary_op(mp_unary_op_t op, mp_obj_t arg) {
                 return result;
             }
         }
+        // With MP_UNARY_OP_INT, mp_unary_op() becomes a fallback for mp_obj_get_int().
+        // In this case provide a more focused error message to not confuse, e.g. chr(1.0)
         if (MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE) {
-            mp_raise_TypeError("unsupported type for operator");
+            if (op == MP_UNARY_OP_INT) {
+                mp_raise_TypeError("can't convert to int");
+            } else {
+                mp_raise_TypeError("unsupported type for operator");
+            }
         } else {
-            nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError,
-                "unsupported type for %q: '%s'",
-                mp_unary_op_method_name[op], mp_obj_get_type_str(arg)));
+            if (op == MP_UNARY_OP_INT) {
+                nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError,
+                    "can't convert %s to int", mp_obj_get_type_str(arg)));
+            } else {
+                nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError,
+                    "unsupported type for %q: '%s'",
+                    mp_unary_op_method_name[op], mp_obj_get_type_str(arg)));
+            }
         }
     }
 }