#5508: Template Haskell -ddump-splices lambda pretty printing bug
---------------------------------+------------------------------------------
Reporter: mgsloan1 | Owner:
Type: bug | Status: new
Priority: normal | Component: Template Haskell
Version: 7.2.1 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Incorrect warning at
compile-time
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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 it
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5508>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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