[GHC] #15209: ~# is always in scope with TypeOperators

[GHC]

#15209: ~# is always in scope with TypeOperators
-------------------------------------+-------------------------------------
        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC accepts       |  Unknown/Multiple
  invalid program                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4763,
       Wiki Page:                    |  Phab:D4801
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"5926b6ed0dcc86f8fd6038fdcc5e2ba2856f40ce/ghc"
 5926b6ed/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="5926b6ed0dcc86f8fd6038fdcc5e2ba2856f40ce"
 Don't expose (~#), (~R#), (~P#) from GHC.Prim

 Currently, the primitive `(~#)`, `(~R#)`, and `(~P#)` type
 constructors are wired in to be exported from `GHC.Prim`. This has
 some unfortunate consequences, however. It turns out that `(~#)` is
 actually a legal infix identifier, so users can make use of unboxed
 equalities in strange ways in user code (see #15209). The other two,
 `(~R#)` and `(~P#)`, can't be used in source code, but they can be
 observed with GHCi's `:browse` command, which is somewhat unnerving.

 The fix for both of these problems is simple: just don't wire them
 to be exported from `GHC.Prim`.

 Test Plan: make test TEST="T12023 T15209"

 Reviewers: bgamari, dfeuer

 Reviewed By: bgamari, dfeuer

 Subscribers: rwbarton, thomie, carter, dfeuer

 GHC Trac Issues: #12023, #15209

 Differential Revision: https://phabricator.haskell.org/D4801
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15209#comment:11>
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