#15985: `pprint EqualityT` infinitely loops -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: 8.8.1 Component: Template Haskell | Version: 8.6.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5403 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ryan Scott <ryan.gl.scott@…>): In [changeset:"89d80921d9328499ffca9877e7dea540350be9c1/ghc" 89d8092/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="89d80921d9328499ffca9877e7dea540350be9c1" Fix embarrassing infinite loop in pprParendType Summary: `pprParendType` was missing an explicit case for `EqualityT`, which caused it to fall through to a catch-all case that invokes `ppr`. But `ppr` itself does not have a case for a partial application of `EqualityT`, so //it// falls back to `pprParendType`, resulting in an infinite loop! The fix is simple: add a case for `EqualityT` in `pprParendType`. While I was in the neighborhood, I removed the catch-call case in `pprParendType` to make this sort of mistake less likely to happen in the future. Test Plan: make test TEST=T15985 Reviewers: bgamari, monoidal, simonpj Reviewed By: monoidal, simonpj Subscribers: rwbarton, carter GHC Trac Issues: #15985 Differential Revision: https://phabricator.haskell.org/D5403 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15985#comment:2> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler