#11787: Infer HasCallStack where possible -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- Consider {{{ Prelude> :t error error :: GHC.Stack.Types.HasCallStack => [Char] -> a Prelude> :t (\x -> error x) (\x -> error x) :: (?callStack::GHC.Stack.Types.CallStack) => [Char] -> a }}} We would prefer to get the same type for the latter as the former. Moreover, when we execute on #11376 (comment 25), `:t error` will show the more complicated type too. My suggestion: during generalisation, when we see `?callStack::CallStack`, use the built-in type synonym `HasCallStack`. Note that this should only happen if the name used for the implicit parameter is actually `?callstack`. Eric would you like to consider this? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11787 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler