http://d.puremagic.com/issues/show_bug.cgi?id=2095

           Summary: covariance w/o typechecks = bugs
           Product: D
           Version: 2.012
          Platform: PC
               URL: http://www.digitalmars.com/webnews/newsgroups.php?art_gr
                    oup=digitalmars.D&article_id=71480
        OS/Version: Windows
            Status: NEW
          Keywords: spec
          Severity: normal
          Priority: P2
         Component: www.digitalmars.com
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: terranium@yandex.ru


class A{}
class B:A{}

B[] ba=[new B];
A[] aa=ba;
aa[0]=new A;
ba[0].methodB(); //ba[0] is expected to be B, but is A


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http://d.puremagic.com/issues/show_bug.cgi?id=2095


terranium@yandex.ru changed:

           What    |Removed                     |Added
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                 CC|                            |fraserofthenight@gmail.com




------- Comment #1 from terranium@yandex.ru  2008-10-10 09:04 -------
*** Bug 2412 has been marked as a duplicate of this bug. ***


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http://d.puremagic.com/issues/show_bug.cgi?id=2095


maxmo@pochta.ru changed:

           What    |Removed                     |Added
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                 CC|                            |lat7h@virginia.edu




------- Comment #2 from maxmo@pochta.ru  2009-02-18 04:40 -------
*** Bug 2544 has been marked as a duplicate of this bug. ***


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http://d.puremagic.com/issues/show_bug.cgi?id=2095


maxmo@pochta.ru changed:

           What    |Removed                     |Added
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OtherBugsDependingO|                            |2573
              nThis|                            |




------- Comment #3 from maxmo@pochta.ru  2009-02-18 04:43 -------
solution was proposed in bug 2412 comment 3


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http://d.puremagic.com/issues/show_bug.cgi?id=2095


smjg@iname.com changed:

           What    |Removed                     |Added
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                 CC|                            |smjg@iname.com




------- Comment #4 from smjg@iname.com  2009-02-18 04:53 -------
This and bug 2412 are about covariance of classes.  Bug 2544 describes covariance of array constancy, which is basically the same but we need to remember that the solution needs applying to both.

See also http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=81566


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http://d.puremagic.com/issues/show_bug.cgi?id=2095





------- Comment #5 from maxmo@pochta.ru  2009-02-18 05:28 -------
As I remember, it was pointed out that rules for implicit conversions of arrays are formulated uniformly for complex and primitive types, and this report is exactly about those rules, and solution for classes works for primitive types.


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http://d.puremagic.com/issues/show_bug.cgi?id=2095


jason.james.house@gmail.com changed:

           What    |Removed                     |Added
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                 CC|                            |jason.james.house@gmail.com




------- Comment #6 from jason.james.house@gmail.com  2009-02-18 22:06 -------
I don't know if it's wise to mark bug 2544 as a duplicate of this bug.  For example, the proposed solution (comment 3) shows a lack of understanding of this related issue.

Specifically, I believe the proposed solution in bug 2412 comment 3 says the
following would be ok:
class base{}
class derived:base{}

derived[] x = new derived[2];
const(base)[] safe = x;

That really isn't true.  Take the following code that should resize the arrays
in place:
derived[] x = new derived[2];
derived.length = 1;
const(base)[] safe = x;
x ~= new derived(); // x[1] is now valid derived instance
safe ~= new base(); // just overwrote x[1] with a non-derived instance


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http://d.puremagic.com/issues/show_bug.cgi?id=2095





------- Comment #7 from maxmo@pochta.ru  2009-02-19 03:01 -------
isn't this bug 2093?


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http://d.puremagic.com/issues/show_bug.cgi?id=2095





------- Comment #8 from maxmo@pochta.ru  2009-02-19 03:09 -------
int[] x=[1,2];
x.length=1;
int[] y=x;
x~=3; // x=[1,3]
y~=4; // x=[1,4]
bug 2093 has little to do with covariance. Added as dependency.


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http://d.puremagic.com/issues/show_bug.cgi?id=2095





------- Comment #9 from maxmo@pochta.ru  2009-02-24 03:24 -------
This turned out to be well-known. Bug 926.
In NG: http://www.digitalmars.com/d/archives/17039.html


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