#9867: PatternSynonyms + ScopedTypeVariables triggers an internal error -------------------------------------+------------------------------------- Reporter: antalsz | Owner: cactus Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 (Type checker) | Keywords: pattern synonyms Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: Compile- | Related Tickets: time crash | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by cactus): Some brainstorming: The patsyn builders are typechecked from this code: {{{ (binds', (extra_binds', thing)) <- tcBindGroups top_lvl sig_fn prag_fn binds $ do { thing <- thing_inside -- See Note [Pattern synonym builders don't yield dependencies] ; patsyn_builders <- mapM tcPatSynBuilderBind patsyns ; let extra_binds = [ (NonRecursive, builder) | builder <- patsyn_builders ] ; return (extra_binds, thing) } }}} At the time we call `tcPatSynBuilderBind`, all the typechecked pattern synonyms are available in the global environment, so we could look up whatever we could possibly need from the output of the typechecker. Currently, it is only easy to grab stuff from the `PatSyn` (which deliberately doesn't contain any details of the actual definition of the pattern synonym, only its type), but we should be able to look up the `PatSynBind Id Id` for a given `PatSynBind Name Name`; and then we should be in business. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9867#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler