[GHC] #13614: Rewrite rules not applied exhaustively when simplifying from plugin

[GHC]

#13614: Rewrite rules not applied exhaustively when simplifying from plugin
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHC API           |              Version:  8.1
      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):

 Ah now I get it

 > As far as I can tell, the rule foo1 and foo2 are attached to all
 occurrences of foo in the module – excluding the ones on the RHS of the
 rules themselves!

 That should not matter: at every occurrence of a variable it is looked up
 in the in-scope set, to get the "master copy", so after simplification all
 occurrences point to the binder.  This is done by `SimplEnv.substId`.

 There is a debug WARN if the `Id` is not in the in-scope set.

 But I bet you have a non-debug compiler; and that you have an in-scope set
 that does not include `foo`.  Might that be it?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13614#comment:3>
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