Maybe your case was more complicated but most IDE's now will tell you about unused variables, methods/functions etc. So if variables storing the calculations that were being built up never ended up being used in the end context of the function you may have gotten a nice gray/red line. It becomes harder to trace if those values are being updated into some table which then never gets used.

It is amusing that sometimes huge swaths of complicated code exist simply because everyone inheriting them is to scared to touch them even though they are basically orphaned and have a net 0 effect on outcome.