> One other point that matters is time: running 20k unit and integration tests to verify the types are all correct for your 6kloc will take much longer than compiling 6kloc
I'll disagree here. The kind of thing you can verify at compile-time can be tested very quickly, and compilers with less useful type systems can be much faster. All in, the tests are probably faster to run.
But yeah, compilers do make a better job on incremental validation. That's probably intrinsic; validation is very likely more prone to be incremental than tests.
> The kind of thing you can verify at compile-time can be tested very quickly
I’m not sure I entirely agree with this. For example, a type system can ensure a function is always called with the right units, but testing that every use of the function is correct might be a lot more tedious, depending on the code base.
> and compilers with less useful type systems can be much faster.
This depends very heavily on the language (e.g., OCaml being a language with a relatively complex type system that also compiled fairly quickly), but Id agree that what you said appears to be the general trend.
I'll disagree here. The kind of thing you can verify at compile-time can be tested very quickly, and compilers with less useful type systems can be much faster. All in, the tests are probably faster to run.
But yeah, compilers do make a better job on incremental validation. That's probably intrinsic; validation is very likely more prone to be incremental than tests.