#4477: GHC silently accepts bang patterns in outermost position
---------------------------------+------------------------------------------
Reporter: dons | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler (Parser)
Version: 7.0.1 RC1 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: GHC accepts invalid program
---------------------------------+------------------------------------------
GHC 6.8, 6.12, 7.0 at least accept bang patterns on the outside of
patterns silently.
{{{
main = do
let !x = 1
return ()
}}}
I expect an "illegal bang pattern" error, but it is accepted:
{{{
$ ghci A.hs
GHCi, version 7.0.0.20101028: 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 ( A.hs, interpreted )
Ok, modules loaded: Main.
}}}
However, if we move it inside some parens, it correctly fails:
{{{
main = do
let (!x) = 1
return ()
}}}
failing with
{{{
A.hs:2:10:
Illegal bang-pattern (use -XBangPatterns):
! x
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4477>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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