#11224: Program doesn't preserve semantics after pattern synonym inlining. -------------------------------------+------------------------------------- Reporter: anton.dubovik | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Resolution: | Keywords: | PatternSynonyms Operating System: Windows | Architecture: x86_64 Type of failure: Incorrect result | (amd64) at runtime | Test Case: Blocked By: | Blocking: Related Tickets: #11225 | Differential Rev(s): Phab:D1632 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"f40e122b7709c11d4ad20fd5cb26bf719235dbf1/ghc" f40e122/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="f40e122b7709c11d4ad20fd5cb26bf719235dbf1" Fix typechecking for pattern synonym signatures Various tickets have revealed bad shortcomings in the typechecking of pattern type synonyms. Discussed a lot in (the latter part of) Trac #11224. This patch fixes the most complex issues: - Both parser and renamer now treat pattern synonyms as an ordinary LHsSigType. Nothing special. Hooray. - tcPatSynSig (now in TcPatSyn) typechecks the signature, and decomposes it into its pieces. See Note [Pattern synonym signatures] - tcCheckPatSyn has had a lot of refactoring. See Note [Checking against a pattern signature] The result is a lot tidier and more comprehensible. Plus, it actually works! NB: this patch doesn't actually address the precise target of #11224, namely "inlining pattern synonym does not preserve semantics". That's an unrelated bug, with a separate patch. ToDo: better documentation in the user manual Test Plan: Validate Reviewers: austin, hvr, goldfire Subscribers: goldfire, mpickering, thomie, simonpj Differential Revision: https://phabricator.haskell.org/D1685 GHC Trac Issues: #11224 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11224#comment:26> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler