#8474: Extremely slow compilation of a program with multiply implicit parameters --------------------------------------------+------------------------------ Reporter: akamaus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ Old description:
Adding yet another ?tstX variable in this snippet slows down compilation by a factor of ten or so. Giving an explicit type annotation to tst1 makes compilation instant.
{-# LANGUAGE ImplicitParams #-}
data D = D Int deriving Show
slow_to_compile :: IO () slow_to_compile = do tst1 <- return 1
let ?tst1 = tst1 let ?tst2 = tst1 let ?tst3 = tst1 let ?tst4 = tst1 let ?tst5 = tst1 let ?tst6 = tst1 let ?tst7 = tst1
print $ D ?tst1
New description: Adding yet another ?tstX variable in this snippet slows down compilation by a factor of ten or so. Giving an explicit type annotation to tst1 makes compilation instant. {{{ {-# LANGUAGE ImplicitParams #-} data D = D Int deriving Show slow_to_compile :: IO () slow_to_compile = do tst1 <- return 1 let ?tst1 = tst1 let ?tst2 = tst1 let ?tst3 = tst1 let ?tst4 = tst1 let ?tst5 = tst1 let ?tst6 = tst1 let ?tst7 = tst1 print $ D ?tst1 }}} -- Comment (by simonpj): Yes, you're right. We'll fix this! Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8474#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler