digitalmars.D.bugs - [Issue 10996] New: Subtyping with "alias this" conflicts with private base type
- d-bugmail puremagic.com (47/47) Sep 08 2013 http://d.puremagic.com/issues/show_bug.cgi?id=10996
- d-bugmail puremagic.com (8/8) Sep 08 2013 http://d.puremagic.com/issues/show_bug.cgi?id=10996
- d-bugmail puremagic.com (16/16) Sep 17 2013 http://d.puremagic.com/issues/show_bug.cgi?id=10996
http://d.puremagic.com/issues/show_bug.cgi?id=10996 Summary: Subtyping with "alias this" conflicts with private base type Product: D Version: D2 Platform: All OS/Version: All Status: NEW Severity: normal Priority: P2 Component: DMD AssignedTo: nobody puremagic.com ReportedBy: joseph.wakeling webdrake.net 2013-09-08 04:46:17 PDT --- Created an attachment (id=1246) Module defining a simple subtype. Consider a simple subtyping example, in the spirit of that given on TDPL p. 231. class Foo { public int a; } class Bar { private Foo _base; alias _base this; this() { _base = new Foo; } } Theoretically, the public member .a of Foo should be publicly available via Bar, as the alias itself is public. However, in practice, any attempt to access it from outside the module will result in an error: Error: class subtype.Bar member _base is not accessible Full example code is attached -- run rdmd -main -unittest subtype.d ... to see how access to Bar.a works from within the module, and then rdmd subtypemain.d ... to see it failing when accessed from outside. The ability to have a private instance of the base type is clearly desirable because you don't want the user to be able to access Bar._base directly. However, the public alias should mean that public methods of _base are made public via Bar's interface. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Sep 08 2013
http://d.puremagic.com/issues/show_bug.cgi?id=10996 2013-09-08 04:47:10 PDT --- Created an attachment (id=1247) Main program file that imports the subtype module. Run to see the bug in action. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Sep 08 2013
http://d.puremagic.com/issues/show_bug.cgi?id=10996 2013-09-17 03:09:41 PDT --- The issue also affects module-level aliases, e.g.: alias fun = Impl!int; private template Impl(T) { void Impl(){} } See: http://forum.dlang.org/thread/sqtmfbzusxzchuncfsoh forum.dlang.org Example benefit for this kind of aliasing: the programmer can define a private implementation that takes a variety of template parameters, and make publicly available only instantiations with a sane choice of parameter values (could be useful for e.g. random number generators). -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Sep 17 2013