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Use withDict instead of unsafeCoerce to implement bindIP #165

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RyanGlScott opened this issue May 13, 2022 · 0 comments · May be fixed by #166
Open

Use withDict instead of unsafeCoerce to implement bindIP #165

RyanGlScott opened this issue May 13, 2022 · 0 comments · May be fixed by #166
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@RyanGlScott
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Currently, bindIP is implemented using unsafeCoerce:

th-desugar/Language/Haskell/TH/Desugar/Util.hs

Lines 433 to 434 in d87ea56

bindIP :: forall name a r. a -> (IP name a => r) -> r
bindIP val k = (unsafeCoerce (MagicIP @name k) :: a -> r) val

Using GHC 9.4 or later, however, we can instead implement this using withDict. This is safer to use, results in cleaner Core, and will be future-proof against future changes to "newtype classes" that are being considered here.

See goldfirere/singletons#490 and ekmett/reflection#44 for related issues.
@RyanGlScott RyanGlScott mentioned this issue May 13, 2022
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RyanGlScott added a commit that referenced this issue May 14, 2022
@RyanGlScott
Use withDict to implement bindIP on recent GHCs
53fad63 
Instead of `unsafeCoerce`, we can use the more recent `withDict` primitive
from `GHC.Exts`. Among other benefits, this is more likely to be future-proof
against possible changes to GHC's representation of "newtype classes" in the
future.

Fixes #165.
@RyanGlScott RyanGlScott linked a pull request May 14, 2022 that will close this issue
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RyanGlScott added a commit that referenced this issue May 14, 2022
@RyanGlScott
Use withDict to implement bindIP on recent GHCs
4625251 
Instead of `unsafeCoerce`, we can use the more recent `withDict` primitive
from `GHC.Exts`. Among other benefits, this is more likely to be future-proof
against possible changes to GHC's representation of "newtype classes" in the
future.

Fixes #165.
@RyanGlScott RyanGlScott mentioned this issue May 14, 2022
Closed
RyanGlScott added a commit that referenced this issue Jun 26, 2022
@RyanGlScott
Use withDict to implement bindIP on recent GHCs
ca02fd7 
Instead of `unsafeCoerce`, we can use the more recent `withDict` primitive
from `GHC.Exts`. Among other benefits, this is more likely to be future-proof
against possible changes to GHC's representation of "newtype classes" in the
future.

Fixes #165.
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Use withDict to implement bindIP on recent GHCs goldfirere/th-desugar
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