Fix C++ compilation error when if/else expression has extension class type.

Cython/Compiler/ExprNodes.py

@@ -9234,6 +9234,8 @@ class CondExprNode(ExprNode):
         self.true_val = self.true_val.analyse_types(env)
         self.false_val = self.false_val.analyse_types(env)
         self.type = PyrexTypes.independent_spanning_type(self.true_val.type, self.false_val.type)
+        if self.type.is_pyobject:
+            self.result_ctype = py_object_type
         if self.true_val.type.is_pyobject or self.false_val.type.is_pyobject:
             self.true_val = self.true_val.coerce_to(self.type, env)
             self.false_val = self.false_val.coerce_to(self.type, env)

tests/run/if_else_expr.pyx

 # mode: run
-# tag: if_else_expr
+# tag: condexpr
+
+cimport cython
 
 cdef class Foo:
+    cdef dict data
+
     def __repr__(self):
         return '<Foo>'
 
@@ -14,3 +18,16 @@ cpdef test_type_cast(Foo obj, cond):
     <Foo>
     """
     return [obj] if cond else obj
+
+
+cdef func(Foo foo, dict data):
+    return foo, data
+
+
+@cython.test_fail_if_path_exists('//PyTypeTestNode')
+def test_cpp_pyobject_cast(Foo obj1, Foo obj2, cond):
+    """
+    >>> test_cpp_pyobject_cast(Foo(), Foo(), True)
+    (<Foo>, None)
+    """
+    return func(obj1 if cond else obj2, obj1.data if cond else obj2.data)