#2497: Weird scoping for tyvars in rules
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Reporter: rl | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.8.3
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Architecture: Unknown
Os: Unknown |
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Comment (by simonpj):
After talking to Simon, and Ian, and taking on board Roman's comments, I
now propose:
* Do '''not''' add `-XRewriteRules`. A RULE is in a pragma, and so is
silently ignored by other compilers anyway. Other pragmas like SPECIALISE
do not have a language extension flag. They will generate errors if they
are plain wrong (e.g. variables out of scope). But adding a language flag
would be inconsistent.
* Inside a RULE, switch on the `forall`-as-keyword in the lexer,
unconditionally. Simon M will do this, and send a patch to Simon PJ for
validation.
* Merge the `-XScopedTypeVariables` and `-XPatternSignatures` flags.
Distinguishing them isn't senseless, but it's jolly confusing.
* Inside a RULE, switch on `-XScopedTypeVariables` unconditionally.
* Change `-frewrite-rules` to `-fuse-rewrite-rules`; deprecate the
former.
Any dissenters?
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2497#comment:4>
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