Check for "Optional[ctype]" earlier because we need to make sure that...

Check for "Optional[ctype]" earlier because we need to make sure that "Optional[int]" etc. interprets "int" as (valid) Python int type and not (invalid) C int type.

See https://github.com/cython/cython/issues/3883

Cython/Compiler/Nodes.py

@@ -969,10 +969,7 @@ class CArgDeclNode(Node):
         if arg_type and arg_type.python_type_constructor_name == "typing.Optional":
             # "x: Optional[...]"  =>  explicitly allow 'None'
             arg_type = arg_type.resolve()
-            if arg_type and not arg_type.is_pyobject:
-                error(annotation.pos, "Only Python type arguments can use typing.Optional[...]")
-            else:
-                self.or_none = True
+            self.or_none = True
         elif arg_type and arg_type.is_pyobject and self.default and self.default.is_none:
             # "x: ... = None"  =>  implicitly allow 'None'
             self.or_none = True
@@ -1225,6 +1222,16 @@ class TemplatedTypeNode(CBaseTypeNode):
                     if type is None and base_type.is_cpp_class:
                         error(template_node.pos, "unknown type in template argument")
                         type = error_type
+                    elif type and base_type.python_type_constructor_name and not (type.is_pyobject or type.is_memoryviewslice):
+                        if type.is_numeric and template_node.is_name and template_node.name in ('int', 'long', 'float', 'complex'):
+                            # int, long, float, complex  =>  make sure we use the Python types
+                            type = env.builtin_scope().lookup_here(template_node.name).type
+                        else:
+                            error(template_node.pos, "%s[...] cannot be applied to non-Python type %s" % (
+                                base_type.python_type_constructor_name,
+                                type,
+                            ))
+                            type = error_type
                     # for indexed_pytype we can be a bit more flexible and pass None
                     template_types.append(type)
                 self.type = base_type.specialize_here(self.pos, env, template_types)
@@ -3155,7 +3162,7 @@ class DefNode(FuncDefNode):
                 else:
                     # probably just a plain 'object'
                     arg.accept_none = True
-            else:
+            elif not arg.type.is_error:
                 arg.accept_none = True  # won't be used, but must be there
                 if arg.not_none:
                     error(arg.pos, "Only Python type arguments can have 'not None'")

Cython/Compiler/PyrexTypes.py

@@ -4482,17 +4482,9 @@ class SpecialPythonTypeConstructor(PythonTypeConstructor):
         # return a copy of the template type with python_type_constructor_name as an attribute
         # so it can be identified, and a resolve function that gets back to
         # the original type (since types are usually tested with "is")
-        new_type = template_values[0]
-        if self.python_type_constructor_name == "typing.ClassVar":
-            # classvar must remain a py_object_type
-            new_type = py_object_type
-        if (self.python_type_constructor_name == "typing.Optional" and
-                not new_type.is_pyobject):
-            # optional must be a py_object, but can be a specialized py_object
-            new_type = py_object_type
         return SpecialPythonTypeConstructor(
             self.python_type_constructor_name,
-            template_type=new_type)
+            template_type=template_values[0])
 
     def __getattr__(self, name):
         if self.template_type:

tests/errors/e_typing_optional.py

@@ -8,11 +8,10 @@ except ImportError:
     pass
 
 
-def optional_pytypes(i: Optional[int], f: Optional[float]):
-    pass
-
+# not OK
 
-def optional_cython_types(i: Optional[cython.int], d: Optional[cython.double], f: Optional[cython.float]):
+def optional_cython_types(i: Optional[cython.int], d: Optional[cython.double], f: Optional[cython.float],
+                          c: Optional[cython.complex], l: Optional[cython.long], ll: Optional[cython.longlong]):
     pass
 
 
@@ -22,13 +21,23 @@ def optional_cstruct(x: Optional[MyStruct]):
     pass
 
 
+# OK
+
+def optional_pytypes(i: Optional[int], f: Optional[float], c: Optional[complex], l: Optional[long]):
+    pass
+
+
+def optional_memoryview(d: double[:], o: Optional[double[:]]):
+    pass
+
+
 _ERRORS = """
-15:29: Only Python type arguments can use typing.Optional[...]
-15:54: Only Python type arguments can use typing.Optional[...]
-15:82: Only Python type arguments can use typing.Optional[...]
-21:24: Only Python type arguments can use typing.Optional[...]
-
-# FIXME: these should be allowed!
-11:24: Only Python type arguments can use typing.Optional[...]
-11:42: Only Python type arguments can use typing.Optional[...]
+13:44: typing.Optional[...] cannot be applied to non-Python type int
+13:69: typing.Optional[...] cannot be applied to non-Python type double
+13:97: typing.Optional[...] cannot be applied to non-Python type float
+14:44: typing.Optional[...] cannot be applied to non-Python type double complex
+14:73: typing.Optional[...] cannot be applied to non-Python type long
+14:100: typing.Optional[...] cannot be applied to non-Python type long long
+
+20:33: typing.Optional[...] cannot be applied to non-Python type MyStruct
 """