Refactor SrcLoc and SrcSpan

The "Unhelpful" cases are now in a separate type. This allows us to
improve various things, e.g.:
* Most of the panic's in SrcLoc are now gone
* The Lexer now works with RealSrcSpans rather than SrcSpans, i.e. it
  knows that it has real locations and thus can assume that the line
  number etc really exists
* Some of the more suspicious cases are no longer necessary, e.g.
  we no longer need this case in advanceSrcLoc:
      advanceSrcLoc loc _ = loc -- Better than nothing

More improvements can probably be made, e.g. tick locations can
probably use RealSrcSpans too.

1 files changed, 5 insertions, 5 deletions

diff --git a/compiler/main/HeaderInfo.hs b/compiler/main/HeaderInfo.hs
index 24a216a4ab..93ce824964 100644
--- a/compiler/main/HeaderInfo.hs
+++ b/compiler/main/HeaderInfo.hs
@@ -55,7 +55,7 @@ getImports :: DynFlags
            -> IO ([Located (ImportDecl RdrName)], [Located (ImportDecl RdrName)], Located ModuleName)
               -- ^ The source imports, normal imports, and the module name.
 getImports dflags buf filename source_filename = do
-  let loc  = mkSrcLoc (mkFastString filename) 1 1
+  let loc  = mkRealSrcLoc (mkFastString filename) 1 1
   case unP parseHeader (mkPState dflags buf loc) of
     PFailed span err -> parseError span err
     POk pst rdr_module -> do
@@ -143,7 +143,7 @@ lazyGetToks dflags filename handle = do
   buf <- hGetStringBufferBlock handle blockSize
   unsafeInterleaveIO $ lazyLexBuf handle (pragState dflags buf loc) False
  where
-  loc  = mkSrcLoc (mkFastString filename) 1 1
+  loc  = mkRealSrcLoc (mkFastString filename) 1 1
 
   lazyLexBuf :: Handle -> PState -> Bool -> IO [Located Token]
   lazyLexBuf handle state eof = do
@@ -160,7 +160,7 @@ lazyGetToks dflags filename handle = do
                   _other    -> do rest <- lazyLexBuf handle state' eof
                                   return (t : rest)
       _ | not eof   -> getMore handle state
-        | otherwise -> return [L (last_loc state) ITeof]
+        | otherwise -> return [L (RealSrcSpan (last_loc state)) ITeof]
                          -- parser assumes an ITeof sentinel at the end
 
   getMore :: Handle -> PState -> IO [Located Token]
@@ -175,12 +175,12 @@ lazyGetToks dflags filename handle = do
 getToks :: DynFlags -> FilePath -> StringBuffer -> [Located Token]
 getToks dflags filename buf = lexAll (pragState dflags buf loc)
  where
-  loc  = mkSrcLoc (mkFastString filename) 1 1
+  loc  = mkRealSrcLoc (mkFastString filename) 1 1
 
   lexAll state = case unP (lexer return) state of
                    POk _      t@(L _ ITeof) -> [t]
                    POk state' t -> t : lexAll state'
-                   _ -> [L (last_loc state) ITeof]
+                   _ -> [L (RealSrcSpan (last_loc state)) ITeof]
 
 
 -- | Parse OPTIONS and LANGUAGE pragmas of the source file.