#11156: Type-changing record update catch-all in sum type doesn't typecheck -------------------------------------+------------------------------------- Reporter: afarmer | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type | Version: 7.10.2 checker) | Resolution: invalid | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): This is analogous to wanting this function to typecheck: {{{ plusOne :: Int -> Int plusOne n = if True then n + 1 else 'A' -- unreachable }}} But the Haskell 98/Haskell 2010 standard says it should not typecheck: "The type of e1 must be Bool; e2 and e3 must have the same type, which is also the type of the entire conditional expression." The same for the original program, though the typing rules for record update are more complicated. But they similarly do not depend on knowledge about the value of the record-to-be-updated. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11156#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler