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: nob...@puremagic.com
ReportedBy: joseph.wakel...@webdrake.net
--- Comment #0 from Joseph Rushton Wakeling <joseph.wakel...@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.
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