[GHC] #13054: Generating unique names with template haskell

[GHC]

#13054: Generating unique names with template haskell
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        Reporter:  tim-m89           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Template Haskell  |              Version:  8.0.1
      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 RyanGlScott):

 My apologies, I was mistakenly under the impression that `NameU`s weren't
 exact.

 As for the idea of having GHC accept collisions between two `Exact` names
 with the same `nameBase` but different uniques... the idea still makes me
 a little bit queasy. I can think of a couple of unfortunate consequences
 of permitting this:

 1. The fact that the program in comment:9 would still be ambiguous.
 Allowing `newName` to create valid top-level names means that you can
 effectively only use them from Template Haskell code in the event you use
 `newName` to create multiple copies of the same name. If you did such a
 thing, any attempt to use one copy of the name would result in ambiguity.

    This means that exporting them, importing them, using them in user-
 written source code, etc. is a no-go. This really feels like the wrong
 design to me—we shouldn't be encouraging the use of such a fragile
 mechanism.
 2. How will Haddock render two top-level names with the same `nameBase`
 generated with two different calls to `newName`? Haddock would pretty much
 have to render the same function names twice, which is bound to cause
 confusion for readers.

 On the other hand `newGlobalName` would not be subject to these flaws.
 Because names produced by `newGlobalName` are truly unique (due to the
 suffix attached to them), no problems emerge from calling `newGlobalName`
 twice with the same `nameBase`. (I'm aware that programs like comment:9
 aren't the intended //purpose// of `newGlobalName`, but it would be nice
 to rule out such tomfoolery by construction.)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13054#comment:13>
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