[GHC] #11035: Add implicit call-stacks to partial functions in base

[GHC]

#11035: Add implicit call-stacks to partial functions in base
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        Reporter:  gridaphobe        |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by gridaphobe):

 Replying to [comment:12 simonmar]:
 > *Please* do not do this in base, instead provide a separate package that
 people can use if they want this functionality.
 >
 > I'm concerned about all the points you raise in the description.  I
 don't think I need to expand on them, you've done a great job of
 explaining the problems this leads to.  So this gets a strong -1 from me,
 at least in base.

 Noted. I actually do have a separate package that exports location-aware
 variants of common partial functions (https://hackage.haskell.org/package
 /located-base), and I don't mind keeping the broader use of CallStacks out
 of base. I opened this ticket primarily because I'm not very satisfied
 with the error produced in the description:

 {{{
 ghci> minimumBy compare []
 *** Exception: Prelude.foldr1: empty list
 CallStack:
   error, called at libraries/base/GHC/List.hs:999:3 in
 base-4.8.2.0:GHC.List
 }}}

 This CallStack adds no value to the error (since `foldr1` is already
 identified as the culprit), but does add a fair bit of noise. Adding more
 CallStacks would make this error much more useful, but it doesn't sound
 like that will happen at this point.

 The other thing we could do is suppress CallStacks inside base. We'd still
 export a CallStack-enhanced `error` and `undefined`, we just wouldn't use
 them internally.

 Do you think the error message would be better without the partial
 CallStack, or does it seem more like a non-issue?

 ------------

 > I should also mention that I'm working on extending profiling to work
 with GHCi, so people using GHCi will get the benefit of full and detailed
 call stacks without any changes at the source level.

 Is there a ticket for this?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11035#comment:13>
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