Fix and type-check casts to qualified cypclass

Cython/Compiler/ExprNodes.py

@@ -10951,6 +10951,9 @@ class TypecastNode(ExprNode):
                 self.op_func_type = entry.type
             if self.type.is_cyp_class:
                 self.is_temp = self.overloaded
+                if self.type.is_qualified_cyp_class:
+                    if not self.type.assignable_from(self.operand.type):
+                        error(self.pos, "Cannot cast %s to %s" % (self.operand.type, self.type))
         if self.type.is_ptr and self.type.base_type.is_cfunction and self.type.base_type.nogil:
             op_type = self.operand.type
             if op_type.is_ptr:

Cython/Compiler/Parsing.py

@@ -321,7 +321,8 @@ def p_typecast(s):
     is_memslice = isinstance(base_type, Nodes.MemoryViewSliceTypeNode)
     is_template = isinstance(base_type, Nodes.TemplatedTypeNode)
     is_const_volatile = isinstance(base_type, Nodes.CConstOrVolatileTypeNode)
-    if not is_memslice and not is_template and not is_const_volatile and base_type.name is None:
+    is_qualified = isinstance(base_type, Nodes.QualifiedCypclassNode)
+    if not is_memslice and not is_template and not is_const_volatile and not is_qualified and base_type.name is None:
         s.error("Unknown type")
     declarator = p_c_declarator(s, empty = 1)
     if s.sy == '?':