1Vet is a tool that checks correctness of Go programs. It runs a suite of tests, 2each tailored to check for a particular class of errors. Examples include incorrect 3Printf format verbs and malformed build tags. 4 5Over time many checks have been added to vet's suite, but many more have been 6rejected as not appropriate for the tool. The criteria applied when selecting which 7checks to add are: 8 9Correctness: 10 11Vet's checks are about correctness, not style. A vet check must identify real or 12potential bugs that could cause incorrect compilation or execution. A check that 13only identifies stylistic points or alternative correct approaches to a situation 14is not acceptable. 15 16Frequency: 17 18Vet is run every day by many programmers, often as part of every compilation or 19submission. The cost in execution time is considerable, especially in aggregate, 20so checks must be likely enough to find real problems that they are worth the 21overhead of the added check. A new check that finds only a handful of problems 22across all existing programs, even if the problem is significant, is not worth 23adding to the suite everyone runs daily. 24 25Precision: 26 27Most of vet's checks are heuristic and can generate both false positives (flagging 28correct programs) and false negatives (not flagging incorrect ones). The rate of 29both these failures must be very small. A check that is too noisy will be ignored 30by the programmer overwhelmed by the output; a check that misses too many of the 31cases it's looking for will give a false sense of security. Neither is acceptable. 32A vet check must be accurate enough that everything it reports is worth examining, 33and complete enough to encourage real confidence. 34