Python-style binary operation methods.

6 files changed, 205 insertions, 17 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 534bf5f83..c82aae518 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -56,6 +56,12 @@ Bugs fixed
 * The signature of the NumPy C-API function ``PyArray_SearchSorted()`` was fixed.
   Patch by Brock Mendel.  (Github issue #3606)
 
+* Added support for Python binary operator semantics.
+  One can now define, e.g. both ``__add__`` and ``__radd__`` for cdef classes
+  as for standard Python classes rather than a single ``__add__`` method where
+  self can be either the first or second argument. (Github issue #2056)
+  This behavior is guarded by the c_api_binop_methods directive.
+
 
 0.29.17 (2020-04-26)
 ====================
diff --git a/Cython/Compiler/ModuleNode.py b/Cython/Compiler/ModuleNode.py
index ede21ff09..193e01ee8 100644
--- a/Cython/Compiler/ModuleNode.py
+++ b/Cython/Compiler/ModuleNode.py
@@ -29,7 +29,7 @@ from . import Pythran
 from .Errors import error, warning
 from .PyrexTypes import py_object_type
 from ..Utils import open_new_file, replace_suffix, decode_filename, build_hex_version
-from .Code import UtilityCode, IncludeCode
+from .Code import UtilityCode, IncludeCode, TempitaUtilityCode
 from .StringEncoding import EncodedString
 from .Pythran import has_np_pythran
 
@@ -1255,6 +1255,9 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
                         self.generate_dict_getter_function(scope, code)
                     if scope.defines_any_special(TypeSlots.richcmp_special_methods):
                         self.generate_richcmp_function(scope, code)
+                    for slot in TypeSlots.PyNumberMethods:
+                        if slot.is_binop and scope.defines_any_special(slot.user_methods):
+                            self.generate_binop_function(scope, slot, code)
                     self.generate_property_accessors(scope, code)
                     self.generate_method_table(scope, code)
                     self.generate_getset_table(scope, code)
@@ -1892,6 +1895,44 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
         code.putln("}")  # switch
         code.putln("}")
 
+    def generate_binop_function(self, scope, slot, code):
+        func_name = scope.mangle_internal(slot.slot_name)
+        code.putln()
+        preprocessor_guard = slot.preprocessor_guard_code()
+        if preprocessor_guard:
+            code.putln(preprocessor_guard)
+        if scope.directives['c_api_binop_methods']:
+            code.putln('#define %s %s' % (func_name, slot.left_slot.slot_code(scope)))
+        else:
+            def has_slot_method(method_name):
+                entry = scope.lookup(method_name)
+                return bool(entry and entry.is_special and entry.func_cname)
+            def call_slot_method(method_name, reverse):
+                entry = scope.lookup(method_name)
+                if reverse:
+                    operands = "right, left"
+                else:
+                    operands = "left, right"
+                if entry and entry.is_special and entry.func_cname:
+                    return "%s(%s)" % (entry.func_cname, operands)
+                else:
+                    py_ident = code.intern_identifier(EncodedString(method_name))
+                    return "%s_maybe_call_super(%s, %s)" % (func_name, operands, py_ident)
+            code.putln(
+                TempitaUtilityCode.load_cached(
+                    "BinopSlot", "ExtensionTypes.c",
+                    context={
+                        "func_name": func_name,
+                        "slot_name": slot.slot_name,
+                        "overloads_left": int(has_slot_method(slot.left_slot.method_name)),
+                        "call_left": call_slot_method(slot.left_slot.method_name, reverse=False),
+                        "call_right": call_slot_method(slot.right_slot.method_name, reverse=True),
+                        "type_cname": '((PyTypeObject*) %s)' % scope.namespace_cname,
+                        }).impl.strip())
+            code.putln()
+        if preprocessor_guard:
+            code.putln("#endif")
+
     def generate_getattro_function(self, scope, code):
         # First try to get the attribute using __getattribute__, if defined, or
         # PyObject_GenericGetAttr.
diff --git a/Cython/Compiler/Options.py b/Cython/Compiler/Options.py
index a634aaf56..db497aa40 100644
--- a/Cython/Compiler/Options.py
+++ b/Cython/Compiler/Options.py
@@ -178,6 +178,7 @@ _directive_defaults = {
     'auto_pickle': None,
     'cdivision': False,  # was True before 0.12
     'cdivision_warnings': False,
+    'c_api_binop_methods': True,  # Change for 3.0
     'overflowcheck': False,
     'overflowcheck.fold': True,
     'always_allow_keywords': False,
diff --git a/Cython/Compiler/TypeSlots.py b/Cython/Compiler/TypeSlots.py
index 137ea4eba..50e09cd74 100644
--- a/Cython/Compiler/TypeSlots.py
+++ b/Cython/Compiler/TypeSlots.py
@@ -180,13 +180,14 @@ class SlotDescriptor(object):
     #  ifdef                         Full #ifdef string that slot is wrapped in. Using this causes py3, py2 and flags to be ignored.)
 
     def __init__(self, slot_name, dynamic=False, inherited=False,
-                 py3=True, py2=True, ifdef=None):
+                 py3=True, py2=True, ifdef=None, is_binop=False):
         self.slot_name = slot_name
         self.is_initialised_dynamically = dynamic
         self.is_inherited = inherited
         self.ifdef = ifdef
         self.py3 = py3
         self.py2 = py2
+        self.is_binop = is_binop
 
     def preprocessor_guard_code(self):
         ifdef = self.ifdef
@@ -405,6 +406,17 @@ class SyntheticSlot(InternalMethodSlot):
             return self.default_value
 
 
+class BinopSlot(SyntheticSlot):
+    def __init__(self, signature, slot_name, left_method, **kargs):
+        assert left_method.startswith('__')
+        right_method = '__r' + left_method[2:]
+        SyntheticSlot.__init__(
+                self, slot_name, [left_method, right_method], "0", is_binop=True, **kargs)
+        # MethodSlot causes special method registration.
+        self.left_slot = MethodSlot(signature, "", left_method)
+        self.right_slot = MethodSlot(signature, "", right_method)
+
+
 class RichcmpSlot(MethodSlot):
     def slot_code(self, scope):
         entry = scope.lookup_here(self.method_name)
@@ -728,23 +740,23 @@ property_accessor_signatures = {
 PyNumberMethods_Py3_GUARD = "PY_MAJOR_VERSION < 3 || (CYTHON_COMPILING_IN_PYPY && PY_VERSION_HEX < 0x03050000)"
 
 PyNumberMethods = (
-    MethodSlot(binaryfunc, "nb_add", "__add__"),
-    MethodSlot(binaryfunc, "nb_subtract", "__sub__"),
-    MethodSlot(binaryfunc, "nb_multiply", "__mul__"),
-    MethodSlot(binaryfunc, "nb_divide", "__div__", ifdef = PyNumberMethods_Py3_GUARD),
-    MethodSlot(binaryfunc, "nb_remainder", "__mod__"),
-    MethodSlot(binaryfunc, "nb_divmod", "__divmod__"),
-    MethodSlot(ternaryfunc, "nb_power", "__pow__"),
+    BinopSlot(binaryfunc, "nb_add", "__add__"),
+    BinopSlot(binaryfunc, "nb_subtract", "__sub__"),
+    BinopSlot(binaryfunc, "nb_multiply", "__mul__"),
+    BinopSlot(binaryfunc, "nb_divide", "__div__", ifdef = PyNumberMethods_Py3_GUARD),
+    BinopSlot(binaryfunc, "nb_remainder", "__mod__"),
+    BinopSlot(binaryfunc, "nb_divmod", "__divmod__"),
+    BinopSlot(ternaryfunc, "nb_power", "__pow__"),
     MethodSlot(unaryfunc, "nb_negative", "__neg__"),
     MethodSlot(unaryfunc, "nb_positive", "__pos__"),
     MethodSlot(unaryfunc, "nb_absolute", "__abs__"),
     MethodSlot(inquiry, "nb_nonzero", "__nonzero__", py3 = ("nb_bool", "__bool__")),
     MethodSlot(unaryfunc, "nb_invert", "__invert__"),
-    MethodSlot(binaryfunc, "nb_lshift", "__lshift__"),
-    MethodSlot(binaryfunc, "nb_rshift", "__rshift__"),
-    MethodSlot(binaryfunc, "nb_and", "__and__"),
-    MethodSlot(binaryfunc, "nb_xor", "__xor__"),
-    MethodSlot(binaryfunc, "nb_or", "__or__"),
+    BinopSlot(binaryfunc, "nb_lshift", "__lshift__"),
+    BinopSlot(binaryfunc, "nb_rshift", "__rshift__"),
+    BinopSlot(binaryfunc, "nb_and", "__and__"),
+    BinopSlot(binaryfunc, "nb_xor", "__xor__"),
+    BinopSlot(binaryfunc, "nb_or", "__or__"),
     EmptySlot("nb_coerce", ifdef = PyNumberMethods_Py3_GUARD),
     MethodSlot(unaryfunc, "nb_int", "__int__", fallback="__long__"),
     MethodSlot(unaryfunc, "nb_long", "__long__", fallback="__int__", py3 = "<RESERVED>"),
@@ -767,8 +779,8 @@ PyNumberMethods = (
 
     # Added in release 2.2
     # The following require the Py_TPFLAGS_HAVE_CLASS flag
-    MethodSlot(binaryfunc, "nb_floor_divide", "__floordiv__"),
-    MethodSlot(binaryfunc, "nb_true_divide", "__truediv__"),
+    BinopSlot(binaryfunc, "nb_floor_divide", "__floordiv__"),
+    BinopSlot(binaryfunc, "nb_true_divide", "__truediv__"),
     MethodSlot(ibinaryfunc, "nb_inplace_floor_divide", "__ifloordiv__"),
     MethodSlot(ibinaryfunc, "nb_inplace_true_divide", "__itruediv__"),
 
@@ -776,7 +788,7 @@ PyNumberMethods = (
     MethodSlot(unaryfunc, "nb_index", "__index__"),
 
     # Added in release 3.5
-    MethodSlot(binaryfunc, "nb_matrix_multiply", "__matmul__", ifdef="PY_VERSION_HEX >= 0x03050000"),
+    BinopSlot(binaryfunc, "nb_matrix_multiply", "__matmul__", ifdef="PY_VERSION_HEX >= 0x03050000"),
     MethodSlot(ibinaryfunc, "nb_inplace_matrix_multiply", "__imatmul__", ifdef="PY_VERSION_HEX >= 0x03050000"),
 )
 
diff --git a/Cython/Utility/ExtensionTypes.c b/Cython/Utility/ExtensionTypes.c
index 1b39c9e42..d34916642 100644
--- a/Cython/Utility/ExtensionTypes.c
+++ b/Cython/Utility/ExtensionTypes.c
@@ -278,3 +278,59 @@ __PYX_GOOD:
     Py_XDECREF(setstate_cython);
     return ret;
 }
+
+/////////////// BinopSlot ///////////////
+
+static CYTHON_INLINE PyObject *{{func_name}}_maybe_call_super(PyObject *self, PyObject *other, PyObject* name) {
+    PyObject *res;
+    PyObject *method;
+    if (!Py_TYPE(self)->tp_base) {
+        return Py_INCREF(Py_NotImplemented), Py_NotImplemented;
+    }
+    // TODO: Use _PyType_LookupId or similar.
+    method = PyObject_GetAttr((PyObject*) Py_TYPE(self)->tp_base, name);
+    if (!method) {
+        PyErr_Clear();
+        return Py_INCREF(Py_NotImplemented), Py_NotImplemented;
+    }
+    res = __Pyx_PyObject_Call2Args(method, self, other);
+    Py_DECREF(method);
+    if (!res) {
+        return Py_INCREF(Py_NotImplemented), Py_NotImplemented;
+    }
+    return res;
+}
+
+static PyObject *{{func_name}}(PyObject *left, PyObject *right) {
+    PyObject *res;
+    int maybe_self_is_left, maybe_self_is_right = 0;
+    maybe_self_is_left = Py_TYPE(left) == Py_TYPE(right)
+            || (Py_TYPE(left)->tp_as_number && Py_TYPE(left)->tp_as_number->{{slot_name}} == &{{func_name}})
+            || PyType_IsSubtype(Py_TYPE(left), {{type_cname}});
+    // Optimize for the common case where the left operation is defined (and successful).
+    if (!{{overloads_left}}) {
+        maybe_self_is_right = Py_TYPE(left) == Py_TYPE(right)
+                || (Py_TYPE(right)->tp_as_number && Py_TYPE(right)->tp_as_number->{{slot_name}} == &{{func_name}})
+                || PyType_IsSubtype(Py_TYPE(right), {{type_cname}});
+    }
+    if (maybe_self_is_left) {
+        if (maybe_self_is_right && !{{overloads_left}}) {
+            res = {{call_right}};
+            if (res != Py_NotImplemented) return res;
+            Py_DECREF(res);
+            maybe_self_is_right = 0;  // Don't bother calling it again.
+        }
+        res = {{call_left}};
+        if (res != Py_NotImplemented) return res;
+        Py_DECREF(res);
+    }
+    if ({{overloads_left}}) {
+        maybe_self_is_right = Py_TYPE(left) == Py_TYPE(right)
+                || (Py_TYPE(right)->tp_as_number && Py_TYPE(right)->tp_as_number->{{slot_name}} == &{{func_name}})
+                || PyType_IsSubtype(Py_TYPE(right), {{type_cname}});
+    }
+    if (maybe_self_is_right) {
+        return {{call_right}};
+    }
+    return Py_INCREF(Py_NotImplemented), Py_NotImplemented;
+}
diff --git a/tests/run/binop_reverse_methods_GH2056.pyx b/tests/run/binop_reverse_methods_GH2056.pyx
new file mode 100644
index 000000000..480853d93
--- /dev/null
+++ b/tests/run/binop_reverse_methods_GH2056.pyx
@@ -0,0 +1,72 @@
+cimport cython
+
+@cython.c_api_binop_methods(False)
+@cython.cclass
+class Base(object):
+    """
+    >>> Base() + 2
+    'Base.__add__(Base(), 2)'
+    >>> 2 + Base()
+    'Base.__radd__(Base(), 2)'
+    """
+    def __add__(self, other):
+        return "Base.__add__(%s, %s)" % (self, other)
+
+    def __radd__(self, other):
+        return "Base.__radd__(%s, %s)" % (self, other)
+
+    def __repr__(self):
+        return "%s()" % (self.__class__.__name__)
+
+@cython.c_api_binop_methods(False)
+@cython.cclass
+class OverloadLeft(Base):
+    """
+    >>> OverloadLeft() + 2
+    'OverloadLeft.__add__(OverloadLeft(), 2)'
+    >>> 2 + OverloadLeft()
+    'Base.__radd__(OverloadLeft(), 2)'
+
+    >>> OverloadLeft() + Base()
+    'OverloadLeft.__add__(OverloadLeft(), Base())'
+    >>> Base() + OverloadLeft()
+    'Base.__add__(Base(), OverloadLeft())'
+    """
+    def __add__(self, other):
+        return "OverloadLeft.__add__(%s, %s)" % (self, other)
+
+
+@cython.c_api_binop_methods(False)
+@cython.cclass
+class OverloadRight(Base):
+    """
+    >>> OverloadRight() + 2
+    'Base.__add__(OverloadRight(), 2)'
+    >>> 2 + OverloadRight()
+    'OverloadRight.__radd__(OverloadRight(), 2)'
+
+    >>> OverloadRight() + Base()
+    'Base.__add__(OverloadRight(), Base())'
+    >>> Base() + OverloadRight()
+    'OverloadRight.__radd__(OverloadRight(), Base())'
+    """
+    def __radd__(self, other):
+        return "OverloadRight.__radd__(%s, %s)" % (self, other)
+
+@cython.c_api_binop_methods(True)
+@cython.cclass
+class OverloadCApi(Base):
+    """
+    >>> OverloadCApi() + 2
+    'OverloadCApi.__add__(OverloadCApi(), 2)'
+    >>> 2 + OverloadCApi()
+    'OverloadCApi.__add__(2, OverloadCApi())'
+
+    >>> OverloadCApi() + Base()
+    'OverloadCApi.__add__(OverloadCApi(), Base())'
+    >>> Base() + OverloadCApi()
+    'OverloadCApi.__add__(Base(), OverloadCApi())'
+    """
+    def __add__(self, other):
+        return "OverloadCApi.__add__(%s, %s)" % (self, other)
+