Hi all, GHC HEAD currently suggests valid in-scope single-identifier substitutions for typed holes (underscores in terms). Some unrelated work somehow changed the output, and I'm wondering if this is a change for the better or for the worse. The test case is this:
f :: Int -> Int -> Int f x y = _ x y
With my patch, GHC now suggests `pure` and `return` as replacements for _ (along with the other top contenders of (-), asTypeOf, and const). (You can also increase the number of suggestions, which will then include (+) and (*) among others.) It's true that `pure` and `return` fit the bill, noting that ((->) Int) is an Applicative. But I doubt these suggestions will help the user. I'm not keen to make fixing this "valid suggestions" feature (which I do really like) a dependency of finishing my patch, but I also don't want the change to output to go unnoticed. So, I'm asking: when I merge my patch, should I post a bug asking for perhaps a priority ordering of suggestions? Thanks, Richard
I'm not sure why pure and return are reported now when they weren't before. Characterising that would be helpful.
But yes, it's an experimental feature, so I don't think you should hold up the train for it. You should talk to the author.
Simon
| -----Original Message-----
| From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Richard
| Eisenberg
| Sent: 27 October 2017 02:43
| To: ghc-devs
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Richard Eisenberg -
Simon Peyton Jones