#11098: TH mishandles type variables that begin with an underscore -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Template | Version: 7.10.2 Haskell | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following GHCi exchange was reported [https://github.com/goldfirere /th-desugar/pull/36 here] (you need not follow the link to understand this ticket, though). {{{ Prelude Language.Haskell.TH> runQ [d|foo :: forall _a . _a -> _a;foo x = x|] [SigD foo_6 (ForallT [PlainTV _a_5] [] (AppT (AppT ArrowT (WildCardT (Just _a_5))) (WildCardT (Just _a_5)))),FunD foo_6 [Clause [VarP x_7] (NormalB (VarE x_7)) []]] }}} The problem is that the quoted expression uses no wildcards, yet the TH output does. That quoted expression just uses a type variable that begins with an underscore. Such an expression was allowed in Haskell long before wildcards. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11098 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler