The following

unittest
{
    import std.datetime.date : Date;
    Date date;
    import core.internal.hash : hashOf;
    auto hash = date.hashOf;
}

errors (with DMD v2.081.0-beta.1) as

/usr/include/dmd/druntime/import/core/internal/convert.d(619,101): Error: template `core.internal.convert.toUbyte` cannot deduce function from argument types `!()(Month)`, candidates are:
/usr/include/dmd/druntime/import/core/internal/convert.d(14,16):        `core.internal.convert.toUbyte(T)(ref T val) if (is(Unqual!T == float) || is(Unqual!T == double) || is(Unqual!T == real) || is(Unqual!T == ifloat) || is(Unqual!T == idouble) || is(Unqual!T == ireal))`
/usr/include/dmd/druntime/import/core/internal/convert.d(479,16):        `core.internal.convert.toUbyte(T)(T[] arr) if (T.sizeof == 1)`
/usr/include/dmd/druntime/import/core/internal/convert.d(485,16):        `core.internal.convert.toUbyte(T)(T[] arr) if (is(typeof(toUbyte(arr[0])) == const(ubyte)[]) && (T.sizeof > 1))`
/usr/include/dmd/druntime/import/core/internal/convert.d(503,16):        `core.internal.convert.toUbyte(T)(ref T val) if (__traits(isIntegral, T) && !is(T == enum))`
/usr/include/dmd/druntime/import/core/internal/convert.d(537,16):        `core.internal.convert.toUbyte(T)(ref T val) if (is(Unqual!T == cfloat) || is(Unqual!T == cdouble) || is(Unqual!T == creal))`
/usr/include/dmd/druntime/import/core/internal/convert.d(619,101):        ... (2 more, -v to show) ...
/usr/include/dmd/druntime/import/core/internal/hash.d(145,37): Error: template instance `core.internal.convert.toUbyte!(Date)` error instantiating
foo.d(6,21):        instantiated from here: `hashOf!(Date)`

but not with 2.080.1. A regression?

On Sunday, June 17, 2018 18:15:19 Per Nordlöw via Digitalmars-d wrote:
> The following
>
> unittest
> {
>      import std.datetime.date : Date;
>      Date date;
>      import core.internal.hash : hashOf;
>      auto hash = date.hashOf;
> }
>
> errors (with DMD v2.081.0-beta.1) as
>
> /usr/include/dmd/druntime/import/core/internal/convert.d(619,101): Error:
> template `core.internal.convert.toUbyte` cannot deduce function from
> argument types `!()(Month)`, candidates are:
> /usr/include/dmd/druntime/import/core/internal/convert.d(14,16):
> `core.internal.convert.toUbyte(T)(ref T val) if
> (is(Unqual!T == float) || is(Unqual!T == double) || is(Unqual!T
> == real) || is(Unqual!T == ifloat) || is(Unqual!T == idouble) ||
> is(Unqual!T == ireal))`
> /usr/include/dmd/druntime/import/core/internal/convert.d(479,16):
>         `core.internal.convert.toUbyte(T)(T[] arr) if (T.sizeof ==
> 1)`
> /usr/include/dmd/druntime/import/core/internal/convert.d(485,16):
>         `core.internal.convert.toUbyte(T)(T[] arr) if
> (is(typeof(toUbyte(arr[0])) == const(ubyte)[]) && (T.sizeof > 1))`
> /usr/include/dmd/druntime/import/core/internal/convert.d(503,16):
>         `core.internal.convert.toUbyte(T)(ref T val) if
> (__traits(isIntegral, T) && !is(T == enum))`
> /usr/include/dmd/druntime/import/core/internal/convert.d(537,16):
>         `core.internal.convert.toUbyte(T)(ref T val) if
> (is(Unqual!T == cfloat) || is(Unqual!T == cdouble) || is(Unqual!T
> == creal))`
> /usr/include/dmd/druntime/import/core/internal/convert.d(619,101):
> ... (2 more, -v to show) ...
> /usr/include/dmd/druntime/import/core/internal/hash.d(145,37):
> Error: template instance `core.internal.convert.toUbyte!(Date)`
> error instantiating
> foo.d(6,21):        instantiated from here: `hashOf!(Date)`
>
> but not with 2.080.1. A regression?

I'm not very familiar with the details of hashOf, so I can't say for sure whether this is a regression or not, but in most cases, if something worked in a previous release but doesn't work now, and there are no deprecation messages involved, then it's probably a regression (especially if the changelog doesn't say anything about it). Occasionally, the breakage is intentional, but you pretty much can't go wrong by reporting it as a regression. Worst case, it turns out that it was completely on purpose, and the bug report will be closed accordingly. But if you don't report it as a regression, and it is one, then it probably won't be fixed before the actual release.

Glancing over the changelog, there are multiple entries which have to do with improving core.internal.hash, and my guess would be that one of those changes accidentally broke something.

- Jonathan M Davis

On Sunday, 17 June 2018 at 18:15:19 UTC, Per Nordlöw wrote:
> The following
>
> unittest
> {
>     import std.datetime.date : Date;
>     Date date;
>     import core.internal.hash : hashOf;
>     auto hash = date.hashOf;
> }
>
> [...]

Well it definitely used to work before:

https://run.dlang.io/is/ayjpcH

I opened an issue for you:

https://issues.dlang.org/show_bug.cgi?id=19005

The PR that introduced this regression was https://github.com/dlang/druntime/pull/2200

On Tuesday, 19 June 2018 at 02:15:46 UTC, Seb wrote:
> I opened an issue for you:
>
> https://issues.dlang.org/show_bug.cgi?id=19005
>
> The PR that introduced this regression was https://github.com/dlang/druntime/pull/2200

Thank you so much again, Seb!