Can't use quotations ([| ... |]) insides declaration splices

Normal Template Haskell allows many levels of splicing and quotations:

> runQ [| (const $([|"Int"|])) |]
AppE (VarE GHC.Base.const) (LitE (StringL "Int"))

And TH can parse declarations easily:

> runQ [d| type T = Int|]
[TySynD T [] (ConT GHC.Base.Int)]

But splicing inside a declaration gives a syntax error:

> runQ [d| type T = $([t|Int|])|]
parse error on input `$('

Another example. Bulat Ziganshin defines the cnst function (http://www.haskell.org/bz/th3.htm) as:

cnst 0 str = [| str |]
cnst n str = [| \_ -> $(cnst (n-1) str) |]

Which evaluates to a function that takes n arguments and returns the string given. It would make sense that a function to define a data constructor which takes n arguments could be written similarly:

dataCnst n = [d|data D = D $(dataCnst' n)|]
dataCnst' n = [t|Int|] ++ dataCnst' (n - 1)

Finally, a function that makes a data type which varies the field type based on an argument:

dataVar n = [d|data D = D $(dataVar' n)|]
dataVar' "Int" = ''Int
dataVar' "String" = ''String
etc.

Trac metadata

Trac field	Value
Version	6.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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