Re: Changing GHC Error Message Wrapping

Thanks Simon. In general I think multiline tuples should have many elements per line, but honestly the tuple case was a very specific example. If possible, I'd like to change the *overall* wrapping for *all* error messages - how does `sep` know when to break lines? there's clearly a numeric value for the number of columns somewhere, but where is it, and is it user-adjustable? For now I am just hacking around this by special-casing some error messages and "un-doing" the line wrapping by parsing the messages and joining lines back together. Thanks, Andrew On Mon, Jan 6, 2014 at 7:44 AM, Simon Peyton-Jones wrote:

I think it’s line 705 in types/TypeRep.lhs

pprTcApp p pp tc tys

| isTupleTyCon tc && tyConArity tc == length tys

= pprPromotionQuote tc <>

tupleParens (tupleTyConSort tc) (sep (punctuate comma (map (pp TopPrec) tys)))

If you change ‘sep’ to ‘fsep’, you’ll get behaviour more akin to paragraph-filling (hence the “f”). Give it a try. You’ll get validation failure from the testsuite, but you can see whether you think the result is better or worse. In general, should multi-line tuples be printed with many elements per line, or just one?

Simon

*From:* ghc-devs [mailto:ghc-devs-bounces@haskell.org] *On Behalf Of *Andrew Gibiansky *Sent:* 04 January 2014 17:30 *To:* Erik de Castro Lopo *Cc:* ghc-devs@haskell.org *Subject:* Re: Changing GHC Error Message Wrapping

Apologize for the broken image formatting.

With the code I posted above, I get the following output:

Couldn't match expected type `(GHC.Types.Int,

GHC.Types.Int,

GHC.Types.Int,

t0,

t10,

t20,

t30,

t40,

t50,

t60,

t70,

t80,

t90)'

with actual type `(t1, t2, t3)'

I would like the types to be on the same line, or at least wrapped to a larger number of columns.

Does anyone know how to do this, or where in the GHC source this wrapping is done?

Thanks!

Andrew

On Sat, Jan 4, 2014 at 2:55 AM, Erik de Castro Lopo wrote:

Carter Schonwald wrote:

...

hey andrew, your image link isn't working (i'm using gmail)

I think the list software filters out image attachments.

Erik -- ---------------------------------------------------------------------- Erik de Castro Lopo http://www.mega-nerd.com/

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