Ill-formed or incorrect multiline string in compiler/main/GHC.hs
After trying to (indirectly) parse GHC.hs using hothasktags, I kept getting an "Illegal character in string gap" error. After reconstructing the file using cpphs I found that the issue is caused by an incorrect multiline string in the raw (i.e. before cpp includes) GHC.hs, that trips the (perhaps stricter?) parser in haskell-src-exts...
The following part of the code:
Nothing -> panic "compileToCoreModule: target FilePath not found in\ module dependency graph"
Nothing -> panic "compileToCoreModule: target FilePath not found in\ \module dependency graph"
It seems the issue goes back to several other versions of the file. Of course it is not really a big deal, but it was hard to trigger (try to parse the file with haskell-src-exts), and to hunt!!