#2530: deriving Show adds extra parens for constructor with record syntax
-----------------------+----------------------------------------------------
Reporter: spl | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.8.3 | Severity: normal
Keywords: | Testcase:
Architecture: x86 | Os: MacOS X
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Since record construction binds more tightly than function application, no
parentheses are needed when passing a constructor with record syntax to a
function constructor. As a result, we can pass {{{Just A {x = 5}}}} as
shown below.
{{{
module Main where
data A = A {x :: Int} deriving (Show)
main :: IO ()
main = print $ Just A {x = 5}
}}}
But we get the result in the GHCi session below:
{{{
*Main> main
Just (A {x = 5})
}}}
I tried looking through {{{TcGenDeriv}}}, but didn't figure out quite
where the parenifying was done. {{{nested_compose_Expr}}}?
{{{show_thingies}}}?
I just wanted to make a ticket for general knowledge. Of course, this is
not a real bug. Perhaps you could reclassify it as a feature. Either way,
it would be nice to have.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2530>
GHC <http://www.haskell.org/ghc/>
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