  Many debugging tools rely on compiler-produced metadata to present a
source-language view of program states, such as variable values and source line
numbers. While this tends to work for unoptimised programs, current compilers
often generate only partial debugging information in optimised programs.
Current approaches for measuring the extent of coverage of local variables are
based on crude assumptions (for example, assuming variables could cover their
whole parent scope) and are not comparable from one compilation to another. In
this work, we propose some new metrics, computable by our tools, which could
serve as motivation for language implementations to improve debugging quality.
