HaskellのflushStdHandles関数のコールグラフ (間違い？)

gistfile1.txt

flushStdHandles
-> hFlush stdout
  -> wantWritableHandle "hFlush" stdout flushWriteBuffer
     let (FileHandle _ m) = stdout -- mはMVar
       -> wantWritableHandle' "hFlush" stdout m flushWriteBuffer
          let act = checkWritableHandle flushWriteBuffer
          -> withHandle_' "hFlush" stdout m act
             let act' = \h_ -> {do a <- act h_; return (h_,a)}
             -> withHandle' "hFlush" stdout m act'
                -> (h',v) <- do_operation "hFlush" h act' m
                   h_ <- takeMVar m
                   -> checkHandleInvariants h_
                   -> act' h_
                     -> checkWritableHandle
                       -> flushWriteBuffer
                         -> flushByteWriteBuffer
                            bbuf <- readIORef haByteBuffer
                            -> bbuf' <- Buffered.flushWriteBuffer haDevice bbuf
                              -> writeBuf' haDevice buf
                                -> writeBuf haDevice buf
                                   let bytes = bufferElems bbuf
                                   let f = \ptr -> IODevice.write haDevice (ptr `plusPtr` bufL bbuf) bytes
                                   withBuffer bbuf f
                                   return bbuf{ bufL=0, bufR=0 }
                            writeIORef haByteBuffer bbuf'
                -> checkHandleInvariants h'
                putMVar m h'
                return v