http://d.puremagic.com/issues/show_bug.cgi?id=249

           Summary: circular typedef and alias bugs
           Product: D
           Version: 0.162
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid, diagnostic, ice-on-invalid-code
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: jpelcis@gmail.com


Here are a few closely related bugs with circular typedefs and aliases.  The most important one is the first (it crashes the compiler), but each version has the same problem but a different error message.

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

module test1;

typedef foo bar;
typedef bar foo;

void main () {
        foo blah;
}

C:\programs>dmd test1.d -v
parse     test1
semantic  test1
semantic2 test1
semantic3 test1
Stack overflow


Without an error message, this can be almost impossible to track down.

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

module test2;

typedef foo bar;
alias bar foo;

void main () {
        foo blah;
}

C:\programs>dmd test2.d
test2.d(3): circular reference of typedef bar
test2.d(3): circular reference of typedef bar


Interesting way to phrase the error message.  It also appears twice, but only shows one of the line numbers.

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

module test3;

alias foo bar;
typedef bar foo;

void main () {
        foo blah;
}

C:\programs>dmd test3.d
test3.d(4): circular reference of typedef foo


This error message is similar to the last one, but it only shows up once this time.  Is it really still a typedef though, or is it an alias?  Either way, one is wrong.

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

module test4;

alias foo bar;
alias bar foo;

void main () {
        foo blah;
}

C:\programs>dmd test4.d
test4.d(4): alias test4.foo recursive alias declaration


I think the "circular" from the other error messages is better than "recursive."  Also, it still only has one of the line numbers and for some reason is the only one that keeps the module name.


-- 

d-bugmail@puremagic.com wrote:
> Here are a few closely related bugs with circular typedefs and aliases.  The
> most important one is the first (it crashes the compiler), but each version has
> the same problem but a different error message.
> 
> -------------------------------
> 
> module test1;
> 
> typedef foo bar;
> typedef bar foo;
> 
> void main () {
>         foo blah;
> }
> 
> C:\programs>dmd test1.d -v
> parse     test1
> semantic  test1
> semantic2 test1
> semantic3 test1
> Stack overflow
> 
> 
> Without an error message, this can be almost impossible to track down.

Yes, that is a bug.

> -------------------------------
> 
> module test2;
> 
> typedef foo bar;
> alias bar foo;
> 
> void main () {
>         foo blah;
> }
> 
> C:\programs>dmd test2.d
> test2.d(3): circular reference of typedef bar
> test2.d(3): circular reference of typedef bar
> 
> 
> Interesting way to phrase the error message.  It also appears twice, but only
> shows one of the line numbers.

Generally, the compiler tries to invent a fix to continue on from a syntax error, but often those fixes just result in more error messages. Not great, but not really a bug.

> -------------------------------
> 
> module test3;
> 
> alias foo bar;
> typedef bar foo;
> 
> void main () {
>         foo blah;
> }
> 
> C:\programs>dmd test3.d
> test3.d(4): circular reference of typedef foo
> 
> 
> This error message is similar to the last one, but it only shows up once this
> time.  Is it really still a typedef though, or is it an alias?  Either way, one
> is wrong.

I'm not sure why the message is wrong. The code certainly is.

> 
> -------------------------------
> 
> module test4;
> 
> alias foo bar;
> alias bar foo;
> 
> void main () {
>         foo blah;
> }
> 
> C:\programs>dmd test4.d
> test4.d(4): alias test4.foo recursive alias declaration
> 
> 
> I think the "circular" from the other error messages is better than
> "recursive."  Also, it still only has one of the line numbers and for some
> reason is the only one that keeps the module name.

It's still a reasonable error message - I agree it could be improved, but why is it a bug?

Walter Bright wrote:
> d-bugmail@puremagic.com wrote:
>> test2.d(3): circular reference of typedef bar
>> test2.d(3): circular reference of typedef bar
>>
>>  snip
>>
>> test3.d(4): circular reference of typedef foo
> 
> I'm not sure why the message is wrong. The code certainly is.

I agree that the code is wrong.  However, one of those is an alias and the other is a typedef.  I suppose it could be debated which is which, but only one is a typedef.

> It's still a reasonable error message - I agree it could be improved, but why is it a bug?

I think that the error messages are good, even if they aren't perfect. My point is that those four pieces of code are essentially the same but all four produce different error messages.  Could they all be made the same?

James Pelcis wrote:
> I think that the error messages are good, even if they aren't perfect. My point is that those four pieces of code are essentially the same but all four produce different error messages.  Could they all be made the same?

I like to keep error messages generated by different parts of the compiler slightly different - makes it easier to track them down.

On Tue, 11 Jul 2006 15:53:11 +1000, Walter Bright <newshound@digitalmars.com> wrote:

> James Pelcis wrote:
>> I think that the error messages are good, even if they aren't perfect. My point is that those four pieces of code are essentially the same but all four produce different error messages.  Could they all be made the same?
>
> I like to keep error messages generated by different parts of the compiler slightly different - makes it easier to track them down.

Try using message IDs like most professional designers do. They are LOTS more easier to track, document and maintain.

-- 
Derek Parnell
Melbourne, Australia

Derek Parnell wrote:

> Try using message IDs like most professional designers do. They are LOTS more easier to track, document and maintain.

Yes, good idea.

Compiler error IDs are also easy to look for in documentation (see VS + MSDN
for example).



-- 

Derek Parnell wrote:
> On Tue, 11 Jul 2006 15:53:11 +1000, Walter Bright <newshound@digitalmars.com> wrote:
> 
>> James Pelcis wrote:
>>> I think that the error messages are good, even if they aren't perfect. My point is that those four pieces of code are essentially the same but all four produce different error messages.  Could they all be made the same?
>>
>> I like to keep error messages generated by different parts of the compiler slightly different - makes it easier to track them down.
> 
> Try using message IDs like most professional designers do. They are LOTS more easier to track, document and maintain.

LOL. I use message IDs in the C++ compiler. I like using the text ones better. (And the issue is the same, if message X comes up, I like it generated in one place, which means each message ID must be used only once.)

Walter Bright wrote:
> Derek Parnell wrote:
>> On Tue, 11 Jul 2006 15:53:11 +1000, Walter Bright <newshound@digitalmars.com> wrote:
>>
>>> James Pelcis wrote:
>>>> I think that the error messages are good, even if they aren't perfect. My point is that those four pieces of code are essentially the same but all four produce different error messages.  Could they all be made the same?
>>>
>>> I like to keep error messages generated by different parts of the compiler slightly different - makes it easier to track them down.
>>
>> Try using message IDs like most professional designers do. They are LOTS more easier to track, document and maintain.
> 
> LOL. I use message IDs in the C++ compiler. I like using the text ones better. (And the issue is the same, if message X comes up, I like it generated in one place, which means each message ID must be used only once.)

Perhaps a context ID would be useful?  Could even encode it into the message ID--set the upper N bits as the message pointer and the lower N bits as the location.  Still not quite as easy to track down as a search for an embedded string though, I'll admit.


Sean

Walter Bright wrote:
> Derek Parnell wrote:
>> On Tue, 11 Jul 2006 15:53:11 +1000, Walter Bright <newshound@digitalmars.com> wrote:
>>
>>> James Pelcis wrote:
>>>> I think that the error messages are good, even if they aren't perfect. My point is that those four pieces of code are essentially the same but all four produce different error messages.  Could they all be made the same?
>>>
>>> I like to keep error messages generated by different parts of the compiler slightly different - makes it easier to track them down.
>>
>> Try using message IDs like most professional designers do. They are LOTS more easier to track, document and maintain.
> 
> LOL. I use message IDs in the C++ compiler. I like using the text ones better. (And the issue is the same, if message X comes up, I like it generated in one place, which means each message ID must be used only once.)

Once we have a 1.0 release, it might be good to have a grep the source to generate a list all of the possible error messages, then put them in a Wiki page.

In article <e918in$lhk$1@digitaldaemon.com>, Andrei Khropov says...
>
>Derek Parnell wrote:
>
>> Try using message IDs like most professional designers do. They are LOTS more easier to track, document and maintain.
>
>Yes, good idea.
>
>Compiler error IDs are also easy to look for in documentation (see VS + MSDN
>for example).

Even if (or especially if) Walter wasn't the one doing the documenting, message IDs would be helpful. For example: http://www.prowiki.org/wiki4d/wiki.cgi?ErrorMessages/CompilerErrors

jcc7