id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
7351	showRichTokenStream has an off-by one error on starting col	alanz	simonmar	"When using showRichTokenStream to re-create a source file, all lines after the first one start one column from the left.

The code for advancing to a new line has an off-by one bug where it assumes zero based columns.

I have marked what I assume to be a fix in the pasted code below.

{{{
showRichTokenStream ts = go startLoc ts """"
    where sourceFile = getFile $ map (getLoc . fst) ts
          getFile [] = panic ""showRichTokenStream: No source file found""
          getFile (UnhelpfulSpan _ : xs) = getFile xs
          getFile (RealSrcSpan s : _) = srcSpanFile s
          startLoc = mkRealSrcLoc sourceFile 1 1
          go _ [] = id
          go loc ((L span _, str):ts)
              = case span of
                UnhelpfulSpan _ -> go loc ts
                RealSrcSpan s
                 | locLine == tokLine -> ((replicate (tokCol - locCol) ' ') ++)
                                       . (str ++)
                                       . go tokEnd ts
                 | otherwise -> ((replicate (tokLine - locLine) '\n') ++)
                              . ((replicate (tokCol - 1) ' ') ++) -- AZ: updated line
                              . (str ++)
                              . go tokEnd ts
                  where (locLine, locCol) = (srcLocLine loc, srcLocCol loc)
                        (tokLine, tokCol) = (srcSpanStartLine s, srcSpanStartCol s)
                        tokEnd = realSrcSpanEnd s
}}}
"	bug	closed	normal	7.6.2	GHC API	7.6.1	fixed			Unknown/Multiple	Unknown/Multiple	None/Unknown	Unknown