mypy: function return types marked as optional

Only methods can have optional return types, but it has to be applied to function
as well as method, otherwise mypy complains.

I considered making a special return type for constructors/destructors, but it
seemed to just make things too messy. Time will tell if this was the right
decision.

cxxheaderparser/parser.py

@@ -1749,6 +1749,7 @@ class CxxParser:
             return method.has_body or method.has_trailing_return
 
         else:
+            assert return_type is not None
             fn = Function(
                 return_type,
                 pqname,
@@ -1778,8 +1779,12 @@ class CxxParser:
                 if fn.template:
                     raise CxxParseError("typedef function may not have a template")
 
+                return_type = fn.return_type
+                if return_type is None:
+                    raise CxxParseError("typedef function must have return type")
+
                 fntype = FunctionType(
-                    fn.return_type,
+                    return_type,
                     fn.parameters,
                     fn.vararg,
                     fn.has_trailing_return,

cxxheaderparser/types.py

@@ -468,7 +468,9 @@ class Function:
     A function declaration, potentially with the function body
     """
 
-    return_type: DecoratedType
+    #: Only constructors and destructors don't have a return type
+    return_type: typing.Optional[DecoratedType]
+
     name: PQName
     parameters: typing.List[Parameter]
 
@@ -510,9 +512,6 @@ class Method(Function):
     A method declaration, potentially with the method body
     """
 
-    #: constructors and destructors don't have a return type
-    return_type: typing.Optional[DecoratedType]
-
     access: str = ""
 
     const: bool = False