Template Haskell top level scoping error

Consider this

module TH where

  $( [d| x = True; f1 = x |])

  $( [d| x = 'c'; f2 = x |] )

I think this should compile fine. There are two bindings of x, so I would not expect to be able to name x in the export list, or indeed anywhere else. But x may just be a local helper-function to the other bindings (f1 and f2 resp) so that's fine.

Alas I get

~/5builds/HEAD-4/inplace/bin/ghc-stage2 -c TH.hs -ddump-splices -ddump-tc
TH.hs:5:4-26: Splicing declarations
    [d| x_apA = True
        f1_apB = x_apA |]
  ======>
    x_a3tN = True
    f1_a3tO = x_a3tN
TH.hs:7:4-25: Splicing declarations
    [d| x_a3u4 = 'c'
        f2_a3u5 = x_a3u4 |]
  ======>
    x_a3uW = 'c'
    f2_a3uX = x_a3uW

TH.hs:7:4: error:
    Multiple declarations of ‘x’
    Declared at: TH.hs:5:4
                 TH.hs:7:4

TH.hs:7:4: error:
    The exact Name ‘x_a3uW’ is not in scope
      Probable cause: you used a unique Template Haskell name (NameU), 
      perhaps via newName, but did not bind it
      If that's it, then -ddump-splices might be useful

So:

• Perhaps we should not complain about multiple top-level bindings for x if they are all Exact RdrNames.
• And the "not in scope" message is clearly bogus.

Mind you, would you expect this to work?

x = True

$( [d| x = 'c'; f2 = x |] )

foo = x  -- Which 'x' do we get?

Maybe the occurrence of x in foo is ambiguous. If you want to splice a hidden helper binding, which can't clash with some earlier or later user-supplied thing, then use an occurrence like $x.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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