https://d.puremagic.com/issues/show_bug.cgi?id=12059

           Summary: Smarter error messages when a module contains a
                    namespace with the same name
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: diagnostic
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2014-02-02 02:35:15 PST ---
This is just one example of a problem in D code that I have seen seen several times in D.learn and elsewhere:

http://forum.dlang.org/thread/mailman.28.1391288417.2683.digitalmars-d-learn@puremagic.com

-------------

> I am having troubles to use the enum defined in the separate
> module.
> When I try to access it, I am getting "Undefined symbol" error:
>
>
> // CodeEnum.d
>
> enum CodeEnum
> {
> 	OK = 200,
> 	FAIL = 400
> }
>
> unittest
> {
> 	auto e = CodeEnum.OK; // Works!
> }
>
>
> // Reply.d
> import CodeEnum;
>
> unittest
> {
> 	auto.e = CodeEnum.OK; // Error: undefined identifier 'OK'
> }
>
>
> What I am doing wrong?

-------------

The answer that explains the problem:

> The module and your enum have the same name. When the compiler sees
> the `CodeEnum` symbol, it considers you're referring to the module.
> This module does not have an `OK` member, hence the error.
> In D, do not use the same symbol for a module and one of its inner symbols.

-------------

Lot of time ago I was hit by a similar problem defining a "set.d" module with inside a "Set" struct plus a "set()" helper function.

There are various ways to avoid this problem. One way is to always forbid to define the name "foo" inside the module named "foo", with an error message (Like: "Error: module foo contains a member named foo. Module members cannot shadow module names" as suggested by Philippe Sigaud).

I like that idea, but it's a significant breaking change, and it looks quite restrictive.

An alternative solution that is much less disruptive change is to just improve the error message. Instead of just giving "Error: undefined identifier 'OK'" a more descriptive error message can tell the programmer what the problem exactly is and how to fix:

Error: undefined identifier 'OK' inside module 'CodeEnum.d'. Did you mean to use 'CodeEnum.CodeEnum.OK'?

This error message does not avoid the problems, so it's less good than forbidding the name duplication, but it could be enough.

-- 
Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------

https://d.puremagic.com/issues/show_bug.cgi?id=12059


Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrej.mitrovich@gmail.com


--- Comment #1 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2014-02-02 06:07:52 PST ---
The first option would break code, if someone actually wants to write code this way. So a simple diagnostic change would be preferred IMO.

-- 
Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------