Tuples

[Diggory]

On Monday, 27 May 2013 at 02:31:50 UTC, Jonathan M Davis wrote:
> On Monday, May 27, 2013 04:24:51 Diggory wrote:
>> It also shouldn't break any code since the only addition to
>> TypeTuple is a check to make sure that the undocumented 
>> behaviour
>> of using it with non-types is disallowed, and in the case that
>> this undocumented feature is used the code can simply switch to
>> StaticTuple and be done.
>
> Well, changing TypeTuple to only accept types _will_ break 
> code. It gets used
> quite heavily with foreach to get a static foreach, and that 
> can involve using
> expressions instead of types. Anyone using TypeTuple heavily 
> knows what it can
> do and will probably have used it for expressions at some 
> point. It wouldn't
> surprise me in the least if it's already done in Phobos, and 
> there's no way to
> know how much it is or isn't done elsewhere.
>
> Because you're generally in control of the TypeTuples that 
> you're using (you
> aren't usually getting the from APIs and the like), I really 
> don' think that
> the fact that it can hold both types and expressions is a big 
> deal. I expect
> that it pretty much never causes problems in actual code. It 
> just makes it so
> that the name sucks. I don't think that we'd gain much (if 
> anything) by
> separating out TypeTuple into three different types. Renaming 
> it would be nice,
> but given the current push to stop making breaking changes like 
> that, I would
> expect that at best, we'd get an alias with a better name.
>
> - Jonathan M Davis

Hmm, given that the fix can be entirely automated incredibly 
simply with find and replace it doesn't seem that bad, especially 
as the broken behaviour is undocumented. Given that the 
documentation specifically disambiguates between TypeTuples and 
ExpressionTuples I think at least emitting a warning when 
non-types are used to a TypeTuple is reasonable.