#15562: `-XStrict -XNoStrict` is not neutral -------------------------------------+------------------------------------- Reporter: hvr | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 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 hvr: Old description:
I assumed we already had a ticket about this, but it appears we have not.
I'm not saying this is a necessarily a bug in the implementation; but we should make sure this is properly documented in the user's guide, and ideally justify why it's done this way rather than the alternatives:
As described in StrictPragma,
`Strict` implies `StrictData`
Currently however the inverse case does not hold, i.e. `NoStrict` does *not* imply `NoStrictData`
This has the surprising property (assuming these were left-most flags on the CLI) that
- `-XStrict -XNoStrict` == `-XStrictData`
- `-XStrictData -XNoStrict` == `-XStrictData`
However, if `-XNoStrict` was to naively imply `-XNoStrictData`, we'd have the properties
- `-XStrict -XNoStrict` == *id*
- `-XStrictData -XNoStrict` == *id*
This might be a bit less confusing; another variant would be
- `-XStrict -XNoStrict` == *id*
- `-XStrictData -XNoStrict` == `-XStrictData`
Btw, I'm not sure what the following means:
- `-XStrict -XNoStrictData` == ?
New description: I assumed we already had a ticket about this, but it appears we have not. I'm not saying this is a necessarily a bug in the implementation; but we should make sure this is properly documented in the user's guide, and ideally justify why it's done this way rather than the alternatives: As described in StrictPragma,
`Strict` implies `StrictData`
Currently however the inverse case does not hold, i.e. `NoStrict` does *not* imply `NoStrictData` This has the surprising property (assuming these were left-most flags on the CLI) that - `-XStrict -XNoStrict` == `-XStrictData` - `-XStrictData -XNoStrict` == `-XStrictData` However, if `-XNoStrict` was to naively imply `-XNoStrictData`, we'd have the properties - `-XStrict -XNoStrict` == ∅ - `-XStrictData -XNoStrict` == ∅ This might be a bit less confusing; another variant would be - `-XStrict -XNoStrict` == ∅ - `-XStrictData -XNoStrict` == `-XStrictData` (strictly speaking, it's not ∅ unless it's these are the left-most flags; also, any `-XNo` still has a cancellation effect on any flags occuring to the left on the CLI) Btw, I'm not sure what the following means: - `-XStrict -XNoStrictData` == ? -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15562#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler