Line number information is usually passed down the chain because it's required for generating debug info anyway. However, as you descend into deeper optimizati

Line number information is usually passed down the chain because it's required for generating debug info anyway. However, as you descend into deeper optimization layers of the compiler, errors are less and less likely to occur. Optimizations are either possible or not, though sometimes these layers can warn you about possible inefficiencies at the source code level (unused local, etc.)