[dragonwriter]

> The value in types is telling the compiler to make certain assumptions so it can optimize the output.

Correctness is more important (in general and as a benefit of type checking) than optimization. Doing the wrong thing fast is easy, but not valuable.

[dllthomas]

Perhaps Devil's advocate, but my rebuttal would be that we're not necessarily comparing similar gains to correctness as to optimisation, and that perhaps the correctness gains can be better attained another way where the optimisation gains cannot.

(Personally I find a type checker tremendously valuable for communicating with myself - and my team, I suppose - about assumptions being made in other parts of the program, which can probably be accounted "correctness".)