Revert "Disable "c_api_binop_methods" directive in 0.29.x and provide it only...

Revert "Disable "c_api_binop_methods" directive in 0.29.x and provide it only as an enabled forward option."

This reverts commit 4ac64ddf.

Cython/Compiler/ModuleNode.py

@@ -2040,10 +2040,6 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
         if scope.directives['c_api_binop_methods']:
             code.putln('#define %s %s' % (func_name, slot.left_slot.slot_code(scope)))
             return
-        else:
-            error(self.pos,
-                  "The 'c_api_binop_methods' directive is only supported for forward compatibility"
-                  " and must be True.")
 
         code.putln()
         preprocessor_guard = slot.preprocessor_guard_code()

tests/run/binop_reverse_methods_GH2056.pyx

+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)'
+
+    >>> Base() ** 2
+    'Base.__pow__(Base(), 2, None)'
+    >>> 2 ** Base()
+    'Base.__rpow__(Base(), 2, None)'
+    >>> pow(Base(), 2, 100)
+    'Base.__pow__(Base(), 2, 100)'
+    """
+    def __add__(self, other):
+        return "Base.__add__(%s, %s)" % (self, other)
+
+    def __radd__(self, other):
+        return "Base.__radd__(%s, %s)" % (self, other)
+
+    def __pow__(self, other, mod):
+        return "Base.__pow__(%s, %s, %s)" % (self, other, mod)
+
+    def __rpow__(self, other, mod):
+        return "Base.__rpow__(%s, %s, %s)" % (self, other, mod)
+
+    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)
+