#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 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by osa1: Old description:

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).

New description: 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). (Example above uses 8.4.4, but this can be reproduced with GHC HEAD too) -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16096#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#16096: let x = ... and x = ... are not the same in GHCi -------------------------------------+------------------------------------- Reporter: osa1 | Owner: osa1 Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by osa1): * owner: (none) => osa1 Comment: I have a fix, will submit a diff soon. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16096#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#16096: let x = ... and x = ... are not the same in GHCi -------------------------------------+------------------------------------- Reporter: osa1 | Owner: osa1 Type: bug | Status: patch Priority: normal | Milestone: Component: GHCi | Version: 8.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5473 Wiki Page: | -------------------------------------+------------------------------------- Changes (by osa1): * status: new => patch * differential: => Phab:D5473 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16096#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#16096: let x = ... and x = ... are not the same in GHCi -------------------------------------+------------------------------------- Reporter: osa1 | Owner: osa1 Type: bug | Status: patch Priority: normal | Milestone: Component: GHCi | Version: 8.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #11606 | Differential Rev(s): Phab:D5473 Wiki Page: | -------------------------------------+------------------------------------- Comment (by osa1): Actually Phab:D5473 even fixes #16089, but in an unexpected way. I'll update #16089. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16096#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#16096: let x = ... and x = ... are not the same in GHCi -------------------------------------+------------------------------------- Reporter: osa1 | Owner: osa1 Type: bug | Status: closed Priority: normal | Milestone: Component: GHCi | Version: 8.6.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #11606 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by osa1): * status: patch => closed * resolution: => fixed Comment: Fixed with a34ee6154. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16096#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#16096: let x = ... and x = ... are not the same in GHCi -------------------------------------+------------------------------------- Reporter: osa1 | Owner: osa1 Type: bug | Status: closed Priority: normal | Milestone: 8.8.1 Component: GHCi | Version: 8.6.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | ghci/should_run/T16096 Blocked By: | Blocking: Related Tickets: #11606 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ömer Sinan Ağacan ): In [changeset:"a34ee61545930d569d0dbafb3a4a5db3a7a711e5/ghc" a34ee615/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="a34ee61545930d569d0dbafb3a4a5db3a7a711e5" Refactor GHCi UI to fix #11606, #12091, #15721, #16096 Instead of parsing and executing a statement or declaration directly we now parse them first and then execute in a separate step. This gives us the flexibility to inspect the parsed declaration before execution. Using this we now inspect parsed declarations, and if it's a single declaration of form `x = y` we execute it as `let x = y` instead, fixing a ton of problems caused by poor declaration support in GHCi. To avoid any users of the modules I left `execStmt` and `runDecls` unchanged and added `execStmt'` and `runDecls'` which work on parsed statements/declarations. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16096#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler