DuplicateRecordFields + TemplateHaskell

The DuplicateRecordFields extension works by mangling the Names of field selector functions, and treating fields specially in the renamer. Thus if you define

data T = MkT { foo :: Int }

then GHC will actually generate a selector called $sel:foo:MkT, but will resolve foo to refer to this selector.

In general we want this name-mangling to be internal only, but at the moment it is visible when using Template Haskell, because the TH AST doesn't have a way to represent the distinction between the selector name and the field label. For example, if you reify ''T above and then pretty-print it you will currently get

data T = MkT { $sel:foo:MkT :: Int }

which is obviously bad.

I'm not sure how best to address this. We could represent the name as mkNameG_v pkg mod "foo", which will look okay when inspected, but if it is subsequently reified it might be ambiguous. Should we add a new NameFlavour?

Trac metadata

Trac field	Value
Version	7.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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