[project @ 2004-10-04 09:27:32 by simonpj]

Make combineSrcSpans commutative

diff --git a/ghc/compiler/basicTypes/SrcLoc.lhs b/ghc/compiler/basicTypes/SrcLoc.lhs
index 8d02e03..95b7172 100644 (file)
--- a/ghc/compiler/basicTypes/SrcLoc.lhs
+++ b/ghc/compiler/basicTypes/SrcLoc.lhs
@@ -284,21 +284,25 @@ mkSrcSpan loc1 loc2
        file = srcLocFile loc1
 
 combineSrcSpans        :: SrcSpan -> SrcSpan -> SrcSpan
+-- Assumes the 'file' part is the same in both
 combineSrcSpans        (ImportedSpan str) _  = ImportedSpan str
 combineSrcSpans        (UnhelpfulSpan str) r = r -- this seems more useful
 combineSrcSpans        _ (ImportedSpan str)  = ImportedSpan str
 combineSrcSpans        l (UnhelpfulSpan str) = l
 combineSrcSpans        start end 
- | line1 == line2 = if col1 == col2
-                       then SrcSpanPoint file line1 col1
-                       else SrcSpanOneLine file line1 col1 col2
- | otherwise      = SrcSpanMultiLine file line1 col1 line2 col2
+ = case line1 `compare` line2 of
+     EQ -> case col1 `compare` col2 of
+               EQ -> SrcSpanPoint file line1 col1
+               LT -> SrcSpanOneLine file line1 col1 col2
+               GT -> SrcSpanOneLine file line1 col2 col1
+     LT -> SrcSpanMultiLine file line1 col1 line2 col2
+     GT -> SrcSpanMultiLine file line2 col2 line1 col1
   where
        line1 = srcSpanStartLine start
+       col1  = srcSpanStartCol start
        line2 = srcSpanEndLine end
-       col1 = srcSpanStartCol start
-       col2 = srcSpanEndCol end
-       file = srcSpanFile start
+       col2  = srcSpanEndCol end
+       file  = srcSpanFile start
 
 instance Outputable SrcSpan where
     ppr span