#10653: PatternSynonyms should be imported/exported as part of the wildcard notation -------------------------------------+------------------------------------- Reporter: gridaphobe | Owner: mpickering Type: feature request | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 7.11 Resolution: | Keywords: pattern | synonyms Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by simonpj): Thanks for the wiki page. But before implementing anything, can you make it a proposed ''specification'' rather than a general idea illustrated by an example or two? Notably: * When, precisely, is it OK to export `T( P )`, where `P` is a pattern synonym? * What, precisely, is exported by `T(..)`? To give you the idea, the [https://www.haskell.org/onlinereport/haskell2010/haskellch5.html#x11-1000005... current spec is here]. I think it's important that one can answer these questions without doing type checking. (In implementation terms, the renamer has to answer these questions, and typechecking has not happened yet.) I think your answers will say something like this. Given {{{ pattern P xs = C p1 p2 }}} where `C` is a data constructor, then `T( P )` is a valid export item iff (a) `C` is a data constructor from data type `T`, and (b) `P` is in scope. It does not matter whether or not `C` is in scope (correct?). But it gets more complicated if `C` is itself a pattern synonym; or, worse, if it is a view pattern. Maybe it's driven off the pattern signature, if there is one? You might find it helpful first to define the notion of "a pattern synonym `P` ''belongs to'' a data type `T`". Anyway, a specification is badly needed! Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10653#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler