http://d.puremagic.com/issues/show_bug.cgi?id=3979

           Summary: Order-of-compilation and forward reference errors
           Product: D
           Version: 2.041
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: blocker
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bugzilla@kyllingen.net


--- Comment #0 from Lars T. Kyllingstad <bugzilla@kyllingen.net> 2010-03-17 01:39:39 PDT ---
I've run into this while working on std.process.  Take the following two files:

    // This is a.d:
    import std.stdio;

    // This is process.d:
    module std.process;
    import std.stdio;
    void foo(File f = std.stdio.stdin);

Compile them in the order they're written here, and you get a nonsensical error:

    lars@neutrino:~/tmp$ dmd -c a.d process.d
    process.d(3): Error: cannot implicitly convert expression (stdin)
    of type File to File

Make the following change to process.d:

    module std.process;
    import std.stdio: File, stdin;  // Selective imports now
    void foo(File f = std.stdio.stdin);

This causes an additional forward reference error:

    lars@neutrino:~/tmp$ dmd -c a.d process.d
    process.d(2): Error: alias std.process.stdin forward reference of
    stdin
    process.d(3): Error: cannot implicitly convert expression (stdin)
    of type File to File

Compile them in reverse order, and it works fine in both cases:

    lars@neutrino:~/tmp$ dmd -c process.d a.d


Note:  I'm marking this as a blocker because it's rather crucial to the new std.process design, and I don't want to muck about with Andrei's makefile just to make it compile.

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug@yahoo.com.au
           Severity|blocker                     |normal


--- Comment #1 from Don <clugdbug@yahoo.com.au> 2010-06-09 23:57:00 PDT ---
This is a weird bug, but it seems to be caused by having a module with the same
name as one in the standard library. If you change the module statement to (for
example) module.std.process2; the problem disappears.
Since this is obscure (you probably won't encounter it unless you're working on
Phobos!) and has a trivial workaround, downgrading from blocker.

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--- Comment #2 from Lars T. Kyllingstad <bugzilla@kyllingen.net> 2010-06-10 00:18:56 PDT ---
I agree, the workaround is trivial up to the point where you want to include the module in Phobos.  But that's exactly where I am now.

I can build Phobos with the module in question by changing the order of modules in the makefile, but it's very fragile.  When I try to run the unittests, for instance, the bug reappears.

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Lars T. Kyllingstad <bugzilla@kyllingen.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |schveiguy@yahoo.com


--- Comment #3 from Lars T. Kyllingstad <bugzilla@kyllingen.net> 2010-07-20 11:41:52 PDT ---
Anxious to get this extremely annoying problem fixed, I've finally been able to reduce it to a small test case:

  // This is a.d
  module a;
  import b;
  struct Foo {}
  Foo foo;

  // This is b.d
  module b;
  import a;
  void fun(Foo f = a.foo);

Compilation gives:

  $ dmd -c a.d b.d
  b.d(4): Error: cannot implicitly convert expression (foo) of type Foo to Foo

Phew!  It took a while, hopefully it's worth it.

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Rainer Schuetze <r.sagitario@gmx.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |r.sagitario@gmx.de


--- Comment #4 from Rainer Schuetze <r.sagitario@gmx.de> 2010-07-20 13:24:50 PDT ---
Now, it very much looks like bug 190 with the forward reference hidden in the cyclic import.

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Adam D. Ruppe <destructionator@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |destructionator@gmail.com


--- Comment #5 from Adam D. Ruppe <destructionator@gmail.com> 2010-08-16 07:40:21 PDT ---
Has anyone tried Rainer's patch in bug 190 to see if it fixes this?

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--- Comment #6 from Rainer Schuetze <r.sagitario@gmx.de> 2010-08-16 08:15:19 PDT ---
(In reply to comment #5)
> Has anyone tried Rainer's patch in bug 190 to see if it fixes this?

Yes, I did and it works for the reduced test case, too. Can't tell about the original report, though.

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--- Comment #7 from Lars T. Kyllingstad <bugzilla@kyllingen.net> 2010-08-17 00:46:28 PDT ---
It does indeed fix the original problem.  Thanks, Rainer!

Any chance we can get this into the next release?

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


--- Comment #8 from Walter Bright <bugzilla@digitalmars.com> 2010-08-27 16:06:37 PDT ---
http://www.dsource.org/projects/dmd/changeset/634

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Steven Schveighoffer <schveiguy@yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Depends on|                            |190, 4753
         Resolution|FIXED                       |


--- Comment #9 from Steven Schveighoffer <schveiguy@yahoo.com> 2010-09-08 05:33:34 PDT ---
Reopened, Walter reverted the changes that fix this in http://www.dsource.org/projects/dmd/changeset/652

It appears that 4753 has an updated patch, can be applied soon?

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