Comment #0 by verylonglogin.reg — 2013-11-19T13:08:50Z
Currently because of Issue 1824 `opEquals` and `opCmp` aren't `const`. It's bad but works if these functions are implemented carefully.
Current dmd rejects `opCmp` call:
---
const Object o1, o2;
assert(o1 == o2); // ok, calls `opEquals`
assert(o1 <= o2); // Error: mutable method object.Object.opCmp is not callable using a const object
---
As a result e.g. `std.typecons.Tuple`-s with classes don't have `opCmp` and fails with "TypeInfo.compare is not implemented" `Error` if used as an associative array key. Error at runtime is really nasty.
Comment #1 by verylonglogin.reg — 2013-11-19T13:14:09Z
(In reply to comment #0)
> Currently because of Issue 1824 `opEquals` and `opCmp` aren't `const`. It's bad
> but works if these functions are implemented carefully.
>
> Current dmd rejects `opCmp` call:
> ---
> const Object o1, o2;
> assert(o1 == o2); // ok, calls `opEquals`
> assert(o1 <= o2); // Error: mutable method object.Object.opCmp is not callable
> using a const object
> ---
>
> As a result e.g. `std.typecons.Tuple`-s with classes don't have `opCmp` and
> fails with "TypeInfo.compare is not implemented" `Error` if used as an
> associative array key. Error at runtime is really nasty.
Why this issue is marked as "regression"? As far as I know, the code you shown had never worked correctly.
Comment #3 by verylonglogin.reg — 2013-11-20T07:31:13Z
(In reply to comment #2)
> Why this issue is marked as "regression"? As far as I know, the code you shown
> had never worked correctly.
Associative arrays use `TypeInfo.compare` and `std.typecons.Tuple` has its `opCmp` with by element comparison for a long time. As `Tuple`-s stopped working as AA keys (it worked at least a year ago) I decided it was a compiler change. If it's not please remove the REGRESSION status.
Comment #4 by k.hara.pg — 2013-11-21T07:30:09Z
(In reply to comment #3)
> (In reply to comment #2)
> > Why this issue is marked as "regression"? As far as I know, the code you shown
> > had never worked correctly.
>
> Associative arrays use `TypeInfo.compare` and `std.typecons.Tuple` has its
> `opCmp` with by element comparison for a long time. As `Tuple`-s stopped
> working as AA keys (it worked at least a year ago) I decided it was a compiler
> change. If it's not please remove the REGRESSION status.
See my comment in your PR. To me the old worked behavior was essentially wrong, and I think it should be kept broken until class const correctness will be fixed.
https://github.com/D-Programming-Language/phobos/pull/1707#issuecomment-28992632
Comment #5 by verylonglogin.reg — 2013-11-24T00:56:24Z
Filed Issue 11588 for inconsistency in abilities to compare `const`/`immutable` classes and Issue 11591 for Phobos regression.
This issue is a request to add ability to compare `const`/`immutable` classes just like currently allowed testing for equality. It will fix Issue 11588 if accepted.
Comment #6 by robert.schadek — 2024-12-13T18:14:06Z