Commit 2d1a563b authored by Committed by Ben Gamari
Implement support for user-defined type errors.
Implements Lennart's idea from the Haskell Symposium. Users may use the special type function `TypeError`, which is similar to `error` at the value level. See Trac ticket https://ghc.haskell.org/trac/ghc/ticket/9637, and wiki page https://ghc.haskell.org/trac/ghc/wiki/CustomTypeErros Test Plan: Included testcases Reviewers: simonpj, austin, hvr, goldfire, bgamari Reviewed By: goldfire, bgamari Subscribers: adamgundry, thomie Differential Revision: https://phabricator.haskell.org/D1236 GHC Trac Issues: #9637
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