public void RemoveSymbol(Symbol sym)
{
// TODO: should invalidate smaller region of map.
CheckWritable();
Debug.Assert(symbols.Contains(sym));
symbols.Remove(sym);
sym.Definition.RemoveSymbol(sym);
sym.SetMap(null);
SetDirty();
}
public void AddSymbol(Symbol sym)
{
// TODO: should invalidate smaller region of map.
CheckWritable();
symbols.Add(sym);
sym.SetMap(this);
sym.Definition.AddSymbol(sym);
SetDirty();
}