Commit 071bef18 authored by Vladislav Zavialov's avatar Vladislav Zavialov Committed by Marge Bot

Fix optSemi type in Parser.y

The definition of 'optSemi' claimed it had type

([Located a],Bool)

Note that its production actually returns ([Located Token],Bool):

  : ';' { ([$1],True) }   -- $1 :: Located Token

Due to an infelicity in the implementation of 'happy -c', it effectively
resulted in 'unsafeCoerce :: Token -> a'.
See https://github.com/simonmar/happy/pull/134

If any consumer of 'optSemi' tried to instantiate 'a' to something not
representationally equal to 'Token', they would experience a segfault.

In addition to that, this definition made it impossible to compile Parser.y
without the -c flag (as it's reliant on this bug to cast 'Token' to 'forall
a. a').
parent ced729f6
-- -*-haskell-*-
-- ---------------------------------------------------------------------------
-- (c) The University of Glasgow 1997-2003
......@@ -2581,7 +2580,7 @@ exp10 :: { LHsExpr GhcPs }
| scc_annot exp {% ams (sLL $1 $> $ HsSCC noExt (snd $ fst $ unLoc $1) (snd $ unLoc $1) $2)
(fst $ fst $ unLoc $1) }
optSemi :: { ([Located a],Bool) }
optSemi :: { ([Located Token],Bool) }
: ';' { ([$1],True) }
| {- empty -} { ([],False) }
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment