#16096: let x = ... and x = ... are not the same in GHCi -------------------------------------+------------------------------------- Reporter: osa1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.6.3 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: -------------------------------------+------------------------------------- With #7253 we implemented support for `x = ...` in GHCi which is supposed to do the same thing as `let x = ...`, but they're currently different, as observed in #16089, #15721, and probably in other tickets. Here's a reproducer: {{{ ~ $ ghci -ddump-bcos GHCi, version 8.4.4: http://www.haskell.org/ghc/ :? for help ... λ:1> let x = [True,False] ==================== Proto-BCOs ==================== ProtoBCO ExprTopLevel_E0#0 []: let sat_s1vF = ... in ... bitmap: 0 [] PUSH_G GHC.Types.[] PUSH_G GHC.Types.False PACK : 2 PUSH_L 0 PUSH_G GHC.Types.True PACK : 2 PUSH_G GHC.Types.[] PUSH_L 1 PACK : 2 PUSH_L 0 PUSH_APPLY_P PUSH_G GHC.Base.returnIO SLIDE 3 3 ENTER λ:2> x = [True,False] ==================== Proto-BCOs ==================== ProtoBCO x1_r1wJ#0 []: GHC.Types.: @ GHC.Types.Bool GHC.Types.False (GHC.Types.[] @ GHC.Types.Bool) bitmap: 0 [] PUSH_G GHC.Types.[] PUSH_G GHC.Types.False PACK : 2 ENTER ProtoBCO Ghci2.x#0 []: GHC.Types.: @ GHC.Types.Bool GHC.Types.True x1_r1wJ bitmap: 0 [] PUSH_G x1_r1wJ PUSH_G GHC.Types.True PACK : 2 ENTER ... }}} Expected behavior: these two should generate the same byte code, and should be subject to same checks (e.g. for shadowing). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16096 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler