py/runtime: If inplace binop fails then try corresponding normal binop.

The code that handles inplace-operator to normal-binary-operator fallback
is moved in this commit from py/objtype.c to py/runtime.c, making it apply
to all types, not just user classes.

Signed-off-by: Damien George <damien@micropython.org>

py/objtype.c

@@ -534,7 +534,6 @@ STATIC mp_obj_t instance_binary_op(mp_binary_op_t op, mp_obj_t lhs_in, mp_obj_t
     // Note: For ducktyping, CPython does not look in the instance members or use
     // __getattr__ or __getattribute__.  It only looks in the class dictionary.
     mp_obj_instance_t *lhs = MP_OBJ_TO_PTR(lhs_in);
-retry:;
     qstr op_name = mp_binary_op_method_name[op];
     /* Still try to lookup native slot
     if (op_name == 0) {
@@ -559,22 +558,12 @@ retry:;
         res = mp_call_method_n_kw(1, 0, dest);
         res = op == MP_BINARY_OP_CONTAINS ? mp_obj_new_bool(mp_obj_is_true(res)) : res;
     } else {
-        // If this was an inplace method, fallback to normal method
-        // https://docs.python.org/3/reference/datamodel.html#object.__iadd__ :
-        // "If a specific method is not defined, the augmented assignment
-        // falls back to the normal methods."
-        if (op >= MP_BINARY_OP_INPLACE_OR && op <= MP_BINARY_OP_INPLACE_POWER) {
-            op -= MP_BINARY_OP_INPLACE_OR - MP_BINARY_OP_OR;
-            goto retry;
-        }
         return MP_OBJ_NULL; // op not supported
     }
 
     #if MICROPY_PY_BUILTINS_NOTIMPLEMENTED
     // NotImplemented means "try other fallbacks (like calling __rop__
-    // instead of __op__) and if nothing works, raise TypeError". As
+    // instead of __op__) and if nothing works, raise TypeError".
-    // MicroPython doesn't implement any fallbacks, signal to raise
-    // TypeError right away.
     if (res == mp_const_notimplemented) {
         return MP_OBJ_NULL; // op not supported
     }

py/runtime.c

@@ -625,6 +625,15 @@ generic_binary_op:
         }
     }
 
+    // If this was an inplace method, fallback to the corresponding normal method.
+    // https://docs.python.org/3/reference/datamodel.html#object.__iadd__ :
+    // "If a specific method is not defined, the augmented assignment falls back
+    // to the normal methods."
+    if (op >= MP_BINARY_OP_INPLACE_OR && op <= MP_BINARY_OP_INPLACE_POWER) {
+        op += MP_BINARY_OP_OR - MP_BINARY_OP_INPLACE_OR;
+        goto generic_binary_op;
+    }
+
     #if MICROPY_PY_REVERSE_SPECIAL_METHODS
     if (op >= MP_BINARY_OP_OR && op <= MP_BINARY_OP_POWER) {
         mp_obj_t t = rhs;

tests/basics/class_reverse_op.py

@@ -46,3 +46,8 @@ print("a" | B("b"))
 print("a" + B("b"))
 print("a" * B("b"))
 print("a" / B("b"))
+
+x = "a"; x |= B("b"); print(x)
+x = "a"; x += B("b"); print(x)
+x = "a"; x *= B("b"); print(x)
+x = "a"; x /= B("b"); print(x)

tests/basics/list_mult.py

@@ -11,6 +11,16 @@ a = [1, 2, 3]
 c = a * 3
 print(a, c)
 
+# check inplace multiplication
+a = [4, 5, 6]
+a *= 3
+print(a)
+
+# check reverse inplace multiplication
+a = 3
+a *= [7, 8, 9]
+print(a)
+
 # unsupported type on RHS
 try:
     [] * None

tests/basics/string_mult.py

@@ -10,3 +10,13 @@ for i in (-4, -2, 0, 2, 4):
 a = '123'
 c = a * 3
 print(a, c)
+
+# check inplace multiplication
+a = '456'
+a *= 3
+print(a)
+
+# check reverse inplace multiplication
+a = 3
+a *= '789'
+print(a)