Template Haskell -ddump-splices lambda pretty printing bug
Parentheses are not placed around lambda expressions when dumping template haskell splices.
One strange thing about this bug is that it only occurs when using "-ddump-splices", and not when using Language.Haskell.TH.Ppr.pprint
x = mkName "x"
thb = QuasiQuoter (const [| $(return . LamE [VarP x] $ VarE x) . id |])
undefined undefined undefined ghci THPrettyBug.hs -ddump-splices -XQuasiQuotes
GHCi, version 7.2.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.
[1 of 1] Compiling Main ( THPrettyBug.hs, interpreted )
Ok, modules loaded: Main.
*Main> [thb| |]
Loading package pretty-1.1.0.0 ... linking ... done.
Loading package array-0.3.0.3 ... linking ... done.
Loading package containers-0.4.1.0 ... linking ... done.
Loading package template-haskell ... linking ... done.
<interactive>:0:1-8: Splicing expression
" " ======> (\ x -> x . id)
<interactive>:0:1:
No instance for (Show (c0 -> c0))
arising from a use of `print'
Possible fix: add an instance declaration for (Show (c0 -> c0))
In a stmt of an interactive GHCi command: print itTrac metadata
| Trac field | Value |
|---|---|
| Version | 7.2.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Template Haskell |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |