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Ryan Scott authored
Summary: The `Read` instance for `Proxy`, as well as a handful of other data types in `base` which only have a single constructor, are doing something skeevy: they're requiring that they be surrounded by parentheses if the parsing precedence is sufficiently high. This means that `"Thing (Proxy)"` would parse, but not `"Thing Proxy"`. But the latter really ought to parse, since there's no need to surround a single constructor with parentheses. Indeed, that's the output of `show (Thing Proxy)`, so the current `Read` instance for `Proxy` violates `read . show = id`. The simple solution is to change `readParen (d > 10)` to `readParen False` in the `Read` instance for `Proxy`. But given that a derived `Read` instance would essentially accomplish the same thing, but with even fewer characters, I've opted to just replace the hand-rolled `Read` instance with a derived one. Test Plan: make test TEST=T12874 Reviewers: ekmett, austin, hvr, goldfire, bgamari Reviewed By: bgamari Subscribers: rwbarton, thomie GHC Trac Issues: #12874 Differential Revision: https://phabricator.haskell.org/D3871
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