Following example will fail to compile in editor:

DROP FUNCTION "public"."isdate" (in text, in b integer, in integer, in d date, in date, in "g'" text, in integer, in "g quoted' name" integer, in "a""''""a" bigint)
GO
CREATE FUNCTION "public"."isdate" (in text, in b integer, in integer, in d date DEFAULT NULL::date, in date DEFAULT '2016-12-07'::date, in "g'" text DEFAULT 'test'::text, in integer DEFAULT 10, in "g quoted' name" integer DEFAULT NULL::integer, in "a""''""a" bigint DEFAULT NULL::bigint) RETURNS date AS
$$
begin
     if ($1 is null) then
         return FALSE;
     end if;
     perform $1::date;
     return  'Test \ string';
exception when others then
     return FALSE;
end;
$$
LANGUAGE 'plpgsql'
GO

This example works fine in query analyzer and alter GUI.  Extraction and scripting is working correctly.  I am not sure why it fails to compile in edtior but I am guessing it has to do with the parameter names having single quotes or double quotes in them.  

The error message is : "Function with this signature does not exist"