#7071: Refactoring arrows
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Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.4.2
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: None/Unknown
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Description changed by simonpj:
Old description:
> At the moment arrow commands re-use `HsExpr` for Proc expressions. But
> with Dan Winograd-Cort I concluded that the best thing by far would be to
> separate the data type of HsExpr from that of arrow commands. I think
> that would lead to a substantial tidy up.
>
> There is also a nasty lurking bug in the type checking of commands; see
> line 290 of TcArrows. Here we call the unifier, but do not do anything
> with the coercion it returns. This is plainly wrong and will bite
> eventually. But I don't understand this code well enough to fix it.
>
> In short, I am not confident of the arrows implementation at the moment.
>
> Several tickets are blocked on this
> * #5022 (which is marked as fixed but is a pretty tricky case)
> * #5267
> * #5777
> * #5609
> * #344
> * #4359 proposal for `proc case` and multi-branch if
New description:
At the moment arrow commands re-use `HsExpr` for Proc expressions. But
with Dan Winograd-Cort I concluded that the best thing by far would be to
separate the data type of `HsExpr` from that of arrow commands. I think
that would lead to a substantial tidy up.
There is also a nasty lurking bug in the type checking of commands; see
line 290 of `TcArrows`. Here we call the unifier, but do not do anything
with the coercion it returns. This is plainly wrong and will bite
eventually. But I don't understand this code well enough to fix it.
In short, I am not confident of the arrows implementation at the moment.
Several tickets are blocked on this
* #5022 (which is marked as fixed but is a pretty tricky case)
* #5267
* #5777
* #5609
* #344
* #4359 proposal for `proc case` and multi-branch if
--
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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7071#comment:2>
GHC <http://www.haskell.org/ghc/>
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