digitalmars.D.bugs - [Issue 2028] New: Can't create template class in module of same name
- d-bugmail puremagic.com Apr 24 2008
- "Jarrett Billingsley" <kb3ctd2 yahoo.com> Apr 24 2008
- d-bugmail puremagic.com Apr 24 2008
- d-bugmail puremagic.com Apr 24 2008
- "Jarrett Billingsley" <kb3ctd2 yahoo.com> Apr 24 2008
- d-bugmail puremagic.com Apr 24 2008
http://d.puremagic.com/issues/show_bug.cgi?id=2028 Summary: Can't create template class in module of same name Product: D Version: 2.012 Platform: PC OS/Version: Linux Status: NEW Severity: normal Priority: P2 Component: DMD AssignedTo: bugzilla digitalmars.com ReportedBy: jlquinn us.ibm.com I'm not sure this is a bug or a language limitation, but it feels like a bug... I have 2 modules: a.d: class a(T) {} b.d: import a; class b { a!(int) x; } When I try to compile this, I get the following error: ~/dmd/bin/dmd -c a.d b.d b.d(4): template instance a is not a template declaration, it is a import b.d(4): Error: a!(int) is used as a type b.d(4): variable b.b.x voids have no value Why can't I do this? --
Apr 24 2008
"Jarrett Billingsley" <kb3ctd2 yahoo.com> <d-bugmail puremagic.com> wrote in message news:bug-2028-3 http.d.puremagic.com/issues/...http://d.puremagic.com/issues/show_bug.cgi?id=2028 Summary: Can't create template class in module of same name Product: D Version: 2.012 Platform: PC OS/Version: Linux Status: NEW Severity: normal Priority: P2 Component: DMD AssignedTo: bugzilla digitalmars.com ReportedBy: jlquinn us.ibm.com I'm not sure this is a bug or a language limitation, but it feels like a bug... I have 2 modules: a.d: class a(T) {} b.d: import a; class b { a!(int) x; } When I try to compile this, I get the following error: ~/dmd/bin/dmd -c a.d b.d b.d(4): template instance a is not a template declaration, it is a import b.d(4): Error: a!(int) is used as a type b.d(4): variable b.b.x voids have no value Why can't I do this?
I don't think it's a "bug" but just a sort of unintuitive bit of symbol lookup. In b.d, when you import a, it creates an entry in b's symbol table that maps from 'a' to 'module a'. It also creates entries for all the symbols inside 'module a', except for anything that conflicts. So when you refer to 'a' in 'module b', it refers to 'module a' and not 'class a'. This is only a problem if the class (or really any symbol) name is the same as the *top-level name* of a module. So if you instead had "mylib.a" as the name of the module, accessing 'class a' would not be a problem. Of course, then accessing a symbol named "mylib" would.
Apr 24 2008
http://d.puremagic.com/issues/show_bug.cgi?id=2028 ------- Comment #1 from webmaster villagersonline.com 2008-04-24 15:47 ------- I don't know whether to call this a bug or a language design issue, but I know the workaround: specify the full name Use a.a instead of a --
Apr 24 2008
http://d.puremagic.com/issues/show_bug.cgi?id=2028 ------- Comment #2 from wbaxter gmail.com 2008-04-24 17:04 ------- (In reply to comment #1)I don't know whether to call this a bug or a language design issue, but I know the workaround: specify the full name Use a.a instead of a
I think this can also be avoided by having the module in a package. Then DMD seems not to get confused. I've not totally understood the specifics, it seems modules and other symbols conflict in ways that package names don't. So I think if you put a.d into an 'a' directory, make it's module statement be "module a.a;" then do import a.a; then you won't get the conflict. Can anyone confirm this? Don't have time at the moment... --
Apr 24 2008
<d-bugmail puremagic.com> wrote in message news:fur052$309q$1 digitalmars.com...http://d.puremagic.com/issues/show_bug.cgi?id=2028 ------- Comment #2 from wbaxter gmail.com 2008-04-24 17:04 ------- (In reply to comment #1)I don't know whether to call this a bug or a language design issue, but I know the workaround: specify the full name Use a.a instead of a
I think this can also be avoided by having the module in a package. Then DMD seems not to get confused. I've not totally understood the specifics, it seems modules and other symbols conflict in ways that package names don't. So I think if you put a.d into an 'a' directory, make it's module statement be "module a.a;" then do import a.a; then you won't get the conflict. Can anyone confirm this? Don't have time at the moment...
That wouldn't work either, since the top-level name is also a. It's that modules and packages have a higher precedence than the symbols within them.
Apr 24 2008
http://d.puremagic.com/issues/show_bug.cgi?id=2028 ------- Comment #3 from wbaxter gmail.com 2008-04-24 18:23 ------- (In reply to comment #2)(In reply to comment #1)I don't know whether to call this a bug or a language design issue, but I know the workaround: specify the full name Use a.a instead of a
I think this can also be avoided by having the module in a package. Then DMD seems not to get confused. I've not totally understood the specifics, it seems modules and other symbols conflict in ways that package names don't. So I think if you put a.d into an 'a' directory, make it's module statement be "module a.a;" then do import a.a; then you won't get the conflict. Can anyone confirm this? Don't have time at the moment...
Jarrett Billingsley wrote:That wouldn't work either, since the top-level name is also a. It's that
Ah, ok. So I guess when I've gotten rid of such problems in the past by putting the offending module in a package, it worked because I named the package something that didn't conflict. But this still does point out the issue with namespace pollution that arises when using top-level, no-package modules. Seems like that should be a general rule of thumb for D programming -- "Effective D": Rule #1: always put your classes in a package. --
Apr 24 2008