On 2017-09-08 13:55, Anthony Clayden wrote:
This has been how it is in GHC for a long time now, so it really is a matter for the Haskell' committee rather than one of the GHC committees.
MPTCs, GADTs (for example) have been in GHC far longer.
AFAIUI these are far from trivial to spec without reference to implementation details such as the type inference algorithm, etc.
OK it's bit naughty GHC doesn't have a flag for something that's not compliant to the report. But that's a GHC issue, not a grounds for changing the language spec.
It's a strong hint that the spec should be changed. There aren't really any widely used Haskell compilers other than GHC and speccing for things that aren't actually used in practice is a waste of time (at best) and actively harmful (at worst). There's a reason that Design by Committee is generally seen as a bad thing if you don't actually have an implementation to guide the spec. Regards,