At the very least, "bound at" should help IDEs (Emacs in particular) show exactly the right places.
> On 24 Oct 2015, at 22:14, Evan Laforge <qdun...@gmail.com> wrote: > > Ok, ticket created. I'll go see how much I can figure out on my own. > > https://ghc.haskell.org/trac/ghc/ticket/11014 > > WRT the "bound at" bits in "relevant bindings", I have no strong opinion. > What about omitting them if they are in the same file as the main error? Or > maybe they always are? I'm not totally clear how it chooses which bindings > are relevant. > > On Sat, Oct 24, 2015 at 12:50 PM, Simon Peyton Jones <simo...@microsoft.com> > wrote: > I’m all for it. Can advise. (Make a ticket.) > > > > Thanks! > > > > Simon > > > > From: Glasgow-haskell-users > [mailto:glasgow-haskell-users-boun...@haskell.org] On Behalf Of Evan Laforge > Sent: 24 October 2015 03:48 > To: GHC users > Subject: type error formatting > > > > Here's a typical simple type error from GHC: > > > > Derive/Call/India/Pakhawaj.hs:142:62: > Couldn't match type ‘Text’ with ‘(a1, Syllable)’ > Expected type: [([(a1, Syllable)], [Sequence Bol])] > Actual type: [([Syllable], [Sequence Bol])] > Relevant bindings include > syllables :: [(a1, Syllable)] > (bound at Derive/Call/India/Pakhawaj.hs:141:16) > best_match :: [(a1, Syllable)] > -> Maybe (Int, ([(a1, Syllable)], [(a1, Sequence Bol)])) > (bound at Derive/Call/India/Pakhawaj.hs:141:5) > In the second argument of ‘mapMaybe’, namely ‘all_bols’ > In the second argument of ‘($)’, namely > ‘mapMaybe (match_bols syllables) all_bols’ > > I've been having more trouble than usual reading GHC's errors, and I finally > spent some time to think about it. The problem is that this new "relevant > bindings include" section gets in between the expected and actual types (I > still don't like that wording but I've gotten used to it), which is the most > critical part, and the location context, which is second most critical. > Notice the same effect in the previous sentence :) After I see a type error > the next thing I want to see is the where it happened, so I have to skip over > the bindings, which can be long and complicated. Then I usually know what to > do, and only look into the bindings if something more complicated is going > on, like wonky inference. So how about reordering the message: > > Derive/Call/India/Pakhawaj.hs:142:62: > Couldn't match type ‘Text’ with ‘(a1, Syllable)’ > Expected type: [([(a1, Syllable)], [Sequence Bol])] > Actual type: [([Syllable], [Sequence Bol])] > In the second argument of ‘mapMaybe’, namely ‘all_bols’ > In the second argument of ‘($)’, namely > ‘mapMaybe (match_bols syllables) all_bols’ > Relevant bindings include > syllables :: [(a1, Syllable)] > (bound at Derive/Call/India/Pakhawaj.hs:141:16) > best_match :: [(a1, Syllable)] > -> Maybe (Int, ([(a1, Syllable)], [(a1, Sequence Bol)])) > (bound at Derive/Call/India/Pakhawaj.hs:141:5) > > After this, why not go one step further and set off the various sections > visibly to make it easier to scan. The context section can also be really > long if it gets an entire do block or record: > > Derive/Call/India/Pakhawaj.hs:142:62: > * Couldn't match type ‘Text’ with ‘(a1, Syllable)’ > Expected type: [([(a1, Syllable)], [Sequence Bol])] > Actual type: [([Syllable], [Sequence Bol])] > * In the second argument of ‘mapMaybe’, namely ‘all_bols’ > In the second argument of ‘($)’, namely > ‘mapMaybe (match_bols syllables) all_bols’ > * Relevant bindings include > syllables :: [(a1, Syllable)] > (bound at Derive/Call/India/Pakhawaj.hs:141:16) > best_match :: [(a1, Syllable)] > -> Maybe (Int, ([(a1, Syllable)], [(a1, Sequence Bol)])) > (bound at Derive/Call/India/Pakhawaj.hs:141:5) > > > > Or alternately, taking up a bit more vertical space: > > > > Derive/Call/India/Pakhawaj.hs:142:62: > Couldn't match type ‘Text’ with ‘(a1, Syllable)’ > Expected type: [([(a1, Syllable)], [Sequence Bol])] > Actual type: [([Syllable], [Sequence Bol])] > > ----------------------------- > In the second argument of ‘mapMaybe’, namely ‘all_bols’ > In the second argument of ‘($)’, namely > ‘mapMaybe (match_bols syllables) all_bols’ > > ----------------------------- > Relevant bindings include > > syllables :: [(a1, Syllable)] > (bound at Derive/Call/India/Pakhawaj.hs:141:16) > best_match :: [(a1, Syllable)] > -> Maybe (Int, ([(a1, Syllable)], [(a1, Sequence Bol)])) > (bound at Derive/Call/India/Pakhawaj.hs:141:5) > > > > Thoughts? It seems simple enough that I could do myself, but of course not > without buy-in. > > > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users
