I wonder if you could actually write a compiler that does this for compilation speed. Have one mode where the compiler is super fast, has no error checking and can compile some malformed programs, and another mode where the compiler does all the checks.

This would be useful for dependencies for example, in most circumstances you can safely assume that dependency code doesn't contain compilation errors, so any passes that check for them are just pure and unnecessary overhead.

I don't know how practical this is, I don't have much experience in compiler design (beyond very small and toy compilers).