Defer declaration analysis of cpp classes until all bases have been analysed

Cython/Compiler/Nodes.py

@@ -1510,6 +1510,8 @@ class CppClassNode(CStructOrUnionDefNode, BlockNode):
     #  decorators    [DecoratorNode] or None
 
     decorators = None
+    scope = None
+    template_types = None
 
     def declare(self, env):
         if not env.is_cpp():
@@ -1522,6 +1524,7 @@ class CppClassNode(CStructOrUnionDefNode, BlockNode):
             num_optional_templates = sum(not required for _, required in self.templates)
             if num_optional_templates and not all(required for _, required in self.templates[:-num_optional_templates]):
                 error(self.pos, "Required template parameters must precede optional template parameters.")
+        self.template_types = template_types
         self.entry = env.declare_cpp_class(
             self.name, None, self.pos, self.cname,
             base_classes=[], visibility=self.visibility, templates=template_types,
@@ -1529,37 +1532,55 @@ class CppClassNode(CStructOrUnionDefNode, BlockNode):
 
     def analyse_declarations(self, env):
         if self.templates is None:
-            template_types = template_names = None
+            template_names = None
         else:
             template_names = [template_name for template_name, _ in self.templates]
-            template_types = [PyrexTypes.TemplatePlaceholderType(template_name, not required)
+            if self.template_types is None:
+                self.template_types = [PyrexTypes.TemplatePlaceholderType(template_name, not required)
                                        for template_name, required in self.templates]
-        scope = None
-        if self.attributes is not None:
+
+        template_types = self.template_types
+
+        if self.scope is None and self.attributes is not None:
             scope = CppClassScope(self.name, env, templates=template_names)
+            self.scope = scope
+        scope = self.scope
+
         def base_ok(base_class):
             if base_class.is_cpp_class or base_class.is_struct:
                 return True
             else:
                 error(self.pos, "Base class '%s' not a struct or class." % base_class)
+
         base_types_list = [b.analyse(scope or env) for b in self.base_classes]
+        base_class_types = list(filter(base_ok, base_types_list))
+
+
+        # if this is not just a forward declaration, defer analysis until all base classes are analysed
+        if scope:
+            for base_type in base_class_types:
+                if not base_type.scope:
+                    base_type.deferred_declarations.append(lambda: self.analyse_declarations(env))
+                    return
+
+        # add implicit cyobject or acthon base if this cypclass has no explicit cypclass bases
         if self.cypclass:
             if self.activable:
                 activable_base = False
-                for base_type in base_types_list:
+                for base_type in base_class_types:
                     if not base_type.activable:
                         error(self.pos, "Activable class cannot inherit from not activable one.")
                     activable_base = activable_base or base_type.activable
                 if not activable_base:
                     from . import Builtin
-                    base_types_list.append(Builtin.acthon_activable_type)
+                    base_class_types.append(Builtin.acthon_activable_type)
 
             cyobject_base = False
-            for base_type in base_types_list:
+            for base_type in  base_class_types:
                 cyobject_base = cyobject_base or base_type.is_cyp_class
             if not cyobject_base:
-                base_types_list.append(cy_object_type)
-        base_class_types = filter(base_ok, base_types_list)
+                base_class_types.append(cy_object_type)
+
         self.entry = env.declare_cpp_class(
             self.name, scope, self.pos,
             self.cname, base_class_types, visibility=self.visibility, templates=template_types,
@@ -1593,7 +1614,10 @@ class CppClassNode(CStructOrUnionDefNode, BlockNode):
                 if self.templates is not None:
                     func.template_declaration = "template <typename %s>" % ", typename ".join(template_names)
         self.body = StatListNode(self.pos, stats=defined_funcs)
-        self.scope = scope
+
+        # analyse the subclasses that were waiting for this class (their base) to be analysed
+        for thunk in self.entry.type.deferred_declarations:
+            thunk()
 
     def analyse_expressions(self, env):
         self.body = self.body.analyse_expressions(self.entry.type.scope)

Cython/Compiler/PyrexTypes.py

@@ -3347,12 +3347,14 @@ class CStructOrUnionType(CType):
     #  scope         StructOrUnionScope, or None if incomplete
     #  typedef_flag  boolean
     #  packed        boolean
+    #  deferred_declarations [thunk] or None     Used to declare class hierarchies in order (None when this type is an union)
 
     #  entry          Entry
 
     is_struct_or_union = 1
     has_attributes = 1
     exception_check = True
+    deferred_declarations = None
 
     def __init__(self, name, kind, scope, typedef_flag, cname, packed=False):
         self.name = name
@@ -3361,6 +3363,8 @@ class CStructOrUnionType(CType):
         self.scope = scope
         self.typedef_flag = typedef_flag
         self.is_struct = kind == 'struct'
+        if self.is_struct:
+            self.deferred_declarations = []
         self.to_py_function = "%s_to_py_%s" % (
             Naming.convert_func_prefix, self.specialization_name())
         self.from_py_function = "%s_from_py_%s" % (
@@ -3535,6 +3539,7 @@ class CppClassType(CType):
     #  cname         string
     #  scope         CppClassScope
     #  templates     [string] or None
+    #  deferred_declarations [thunk]      Used to declare class hierarchies in order
 
     is_cpp_class = 1
     has_attributes = 1
@@ -3553,6 +3558,7 @@ class CppClassType(CType):
         self.cname = cname
         self.scope = scope
         self.base_classes = base_classes
+        self.deferred_declarations = []
         self.operators = []
         self.templates = templates
         self.template_type = template_type