I wonder if we can keep our nice separation of types being declarative and terms being operational by augmenting Richard's proposed partialityIsOK :: String -> (Partial => r) -> r with partialityIsOKWithCallStack :: String -> (Partial => r) -> r Then it would become the call site's choice whether to ask for a call stack rather than just unilaterally providing one whether the caller wants it or not (which I believe is the current situation -- I admit I don't understand HasCallStack). Tom On Wed, Jun 09, 2021 at 11:51:12AM -0400, Carter Schonwald wrote:
The sad part is seemingly it discards having an informative stack trace?
On Wed, Jun 9, 2021 at 10:16 AM Simon Peyton Jones via Libraries < libraries@haskell.org> wrote:
| If we indeed had something like | | head :: Partial => [a] -> a | | that would be both informative and fairly straightforward to | explain to students, for example. (Even if it is not clear to | me that a type class really is the right way to express | partiality of functions: I always thought information about | partiality ought to be tied to the function arrow.)
OK -- that sounds promising. It's what Richard suggested earlier, and sounds pretty good to me.