On 10/17/2014 05:41 AM, Steven Schveighoffer via dmd-beta wrote:
On Oct 16, 2014, at 3:42 PM, Martin Nowak via dmd-beta <[email protected]>
wrote:
On 10/16/2014 01:32 PM, Steven Schveighoffer via dmd-beta wrote:
I am too actually. From your earlier messages, Martin, I thought you said we
would add it as a warning? Has that been done for 2.066.1? I didn't see it in
my github traffic.
FWIW, I think a warning is sufficient, even if it only lasts a few versions. As
long as silent behavior changes do not happen.
Well I made a pull and we eventually agreed that even a warning would do more
harm than good, because one cannot explicitly use the compiler generated toHash
and opEquals. A opCmp that wouldn't comply with default equality also required
a custom toHash, which makes it even more unlikely that we will break code.
I think there is a misunderstanding, the issue is not that opCmp and opEquals
are not consistent. The problem is this:
1. As of 2.065, AAs used opCmp and NOT opEquals.
2. Despite the spec's assertion that BOTH opEquals and opCmp should be defined
for AA to work properly, the compiler allowed any combination, and let the
implementation tell the story.
3. All that was required was to override opCmp and toHash to make AAs work.
4. In 2.066, we no longer use opCmp and use opEquals.
5. Without an error, any code that ONLY defined opCmp (and defined it
differently than the default) despite the warnings from the spec will now
silently compile, and do the incorrect thing.
The gordian knot is that we cannot add an error or even a warning for
correct code as there is no way to be explicit about a missing opEquals
(`bool opEquals() = default;`).
I don't have a good idea here other than emphasizing the changelog and
properly describing the state of affairs.
http://dlang.org/changelog.html#aa-key-requirement
This was already released with 2.066 over 2 month ago.
Has anyone heard of a real issue with this change?
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