Improve "uninitialised element" error message

[alexwl]

Compaction (http://hackage.haskell.org/package/ghc-compact-0.1.0.0/docs/GHC-Compact.html#v:compact) of an immutable vector may crash with the confusing "uninitialised element" error message #220:

module Main where

import qualified Data.Vector as V
import GHC.Compact

main :: IO ()
main = do
  c <- compact $ V.fromList [1, 2, 3]
  pure ()

*** Exception: Data.Vector.Mutable: uninitialised element

As far as I understand, there is no simple way to fix this. However, there is an easy workaround: use the force function.

This code doesn't crash:

c <- compact $ V.force $ V.fromList [1, 2, 3]

The PR adds a suggestion to use the force function in the error message.

[cartazio]

Thanks! I’ll go over this and merge it in soonish.

…

On Wed, Dec 12, 2018 at 9:18 AM Alexey Kiryushin ***@***.***> wrote: Compaction ( http://hackage.haskell.org/package/ghc-compact-0.1.0.0/docs/GHC-Compact.html#v:compact) of an immutable vector may crash with the confusing "uninitialised element" error message #220 <#220>: module Main where import qualified Data.Vector as Vimport GHC.Compact main :: IO () main = do c <- compact $ V.fromList [1, 2, 3] pure () *** Exception: Data.Vector.Mutable: uninitialised element As far as I understand, there is no simple way to fix this. However, there is an easy workaround: use the force function. This code doesn't crash: c <- compact $ V.force $ V.fromList [1, 2, 3] The PR adds a suggestion to use the force function in the error message. ------------------------------ You can view, comment on, or merge this pull request online at: #231 Commit Summary - Add a suggestion to use the 'force' function in the 'uninitialised element' error message File Changes - *M* Data/Vector/Mutable.hs <https://github.com/haskell/vector/pull/231/files#diff-0> (2) Patch Links: - https://github.com/haskell/vector/pull/231.patch - https://github.com/haskell/vector/pull/231.diff — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#231>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAQwnVKCUh5Q4IpqLDA-TJauVFPjmrfks5u4RBFgaJpZM4ZPh5N> .

[recursion-ninja]

Is this still mergable?

It would help a user of both vector & compact packages with debugging diagnostics.

[cartazio]

I’ll takw a look now.

…

On Tue, Jul 9, 2019 at 1:37 PM recursion-ninja ***@***.***> wrote: Is this still mergable? It would help with a user of both vector & compact packages with debugging diognostics. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#231?email_source=notifications&email_token=AAABBQWE2TJRRH5PROJHHBDP6TEETA5CNFSM4GJ6DZG2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODZQ7M4Q#issuecomment-509736562>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAABBQTSEWIUJXWK3H3QX4LP6TEETANCNFSM4GJ6DZGQ> .

[enobayram]

I wish this PR were merged and released. Would've saved us many hours of debugging.

[cartazio]

Please add it to the release checklist ticket if it’s not merged into master already and I’ll get to it shortly.

…

On Wed, Jan 15, 2020 at 3:15 AM Enis Bayramoğlu ***@***.***> wrote: I wish this PR were merged and released. Would've saved us many hours of debugging. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#231?email_source=notifications&email_token=AAABBQW775RJA4K5GGEG6E3Q53AZLA5CNFSM4GJ6DZG2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEI7OBMI#issuecomment-574546097>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAABBQSJVCYGDV62ZGBEFFLQ53AZLANCNFSM4GJ6DZGQ> .

[enobayram]

Thanks, I believe that's what you meant.

[recursion-ninja]

Thanks, I've lost well over 40 man-hours getting bitten by this multiple times, usually in a trasitive dependency. It will be nice to get a moderately useful error message.