Fix issue 6227 - Disallow comparison of different enums

[LemonBoy]

This is only for named enums, the anonymous ones are currently typed as their own base type and we can't do much about those at least with the way the anonymous enums are handled by the frontend.

I agree it is possible to fix enum.

So let's do it, one step a time!
There are no regressions in phobos or druntime which is a green flag, let's see what you (and the auto tester) has to say about this change.

[dlang-bot]

Fix	Bugzilla	Description
✓	6227	Comparison of different enums

[WalterWaldron]

Disallow -> Deprecate

[MartinNowak]

Also a changelog notice that this got deprecated would be nice.
https://github.com/dlang/dmd/tree/master/changelog

[MartinNowak]

???

[LemonBoy]

My bad. Since the array contains the full path as zero-eth element gdb decides to split the content over many lines, making the regex fail. I've never bothered to submit a fixed test and I guess this is the right moment to do so.

[MartinNowak]

Seems like it triggered on assignment as well.
Also we should address this not only for equal comparisons, but for any comparisons? What about other operations?

[LemonBoy]

Not quite, what you see in diag14950 is this EqualExp being analysed during the calculation of the values for the subsequent enum members and can be easily solved by gagging the errors during the evaluation of the + 1 expression and by making sure the memtype is an integral (or floating) one so that we can show a meaningful error.

Wrt extending this rule to the other binary operations I think that's the next logical step and can be easily added at a later time to this PR, at least once/if the team and community approves this idea.

[LemonBoy]

As an added bonus this change allows us to easily fix b16083: in the example provided both the AliasSeq are hashed to the same value since dtemplate.d expressionHash hashes the value itself (the "foo" string) and doesn't take into account the type.

[ordahan]

Hey guys, whats going on with this PR?

[WalterBright]

One issue with this is if one wants to compare such issues, a cast becomes necessary. Casts are dangerous creatures, in that if the underlying types shift, all kinds of hidden problems can emerge (like unintended truncation).

[andralex]

We plan to get this fixed. @LemonBoy are you around? Rebase please?

[UplinkCoder]

t1 and t2
are either already used or getting used futher down.
I recommend scopeing { them in a bock }

[andralex]

Since @LemonBoy seems to not be around, @UplinkCoder could you please take this over? Please let us know. Thanks!

[UplinkCoder]

@andralex @LemonBoy is around, I just saw him on irc a few days ago
I can fork this pr and fix it; but I'd rather wait a day or two.

[UplinkCoder]

@andralex done in #6821
@LemonBoy told me it's okay to take this over.

[andralex]

@UplinkCoder thx! @LemonBoy you're always welcome around!