[GHC] #14527: Warn on recursive bindings

GHC ghc-devs at haskell.org
Tue Nov 28 10:35:27 UTC 2017


#14527: Warn on recursive bindings
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        Reporter:  chrisdone         |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      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:                    |
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Comment (by simonpj):

 > So I'm afraid it's less straight-forward than I hoped.

 It's only a warning so it's ok to have ad-hoc (but still well specified)
 conditions.  For example: you get a warning if

 * The binding is recursive (or part of a recursive group)
 * It is a pattern or simple variable binding; that is there are no
 argument on the LHS
 * The LHS does not have a top-level tilde
 * The RHS is not a syntactic value.

 Then define syntactic values to be: literal, constructor application,
 lambda, `\case`, etc.    (This is the slightly ad-hoc bit.)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14527#comment:13>
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