#14117: stg-lint fails on unlifted-type join point binding -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- While validating GHC with `BuildFlavour=devel2` and `-dstg-lint` I found that the linter chokes when it finds a join point of unlifted type (like this one from the `Binary` module), {{{ ghc-stage1: panic! (the 'impossible' happened) (GHC version 8.3.20170815 for x86_64-unknown-linux): *** Stg Lint ErrMsgs: in Stg2Stg *** <no location info>: warning: [RHS of $j_sDSL :: (# State# RealWorld, () #)] Let(rec) binder ‘$j_sDSL’ has unlifted type ‘(# State# RealWorld, () #)’ RHS: \r [] src<compiler/utils/Binary.hs:516:9-17> src<compiler/utils/Binary.hs:(516,21)-(518,26)> src<compiler/utils/Binary.hs:260:1-45> src<compiler/utils/Binary.hs:(239,1)-(246,34)> case readIntArray# [ww_sDSF 0# w1_sDSJ] of { ... }}} If I'm not mistaken there is no problem with join points having unlifted type (see `Note [CoreSyn let/app invariant]`). We just need to update the STG linter appropriately. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14117> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler