This is commonly believed, but in fact, a type checker introduces bugs. It shifts the cost of a certain class of mistakes so much that the kinds of mistakes people make in the presence of a type checker destroy their ability to think clearly about types.
Experience strongly suggests that people who use strongly-typed languages and have compilers who produce informative error messages when type constraints are violated, cause their programmers to believe several idiotic ideas: (1) Type errors are important. They are not. You would not make them if the cost of making type errors was higher. (2) Satisfying the compiler is no longer only an inconsequential necessary condition for a program to be correct, it becomes a sufficient condition in the minds of those who make the first mistake. (3) Errors in programs are separated into two kinds of vastly different nature: static errors (which the compiler may report) and dynamic errors (which the compiler cannot find).
This false dichotomy completely warps the minds of progrrammers in these languages: Instead of becoming fundamentally stupid errors that the compiler should just go and fix, static errors become /more/ important than dynamic errors, leading to serious growth of dynamic errors because programmers tend to rely on the compiler for detection and correction of mistakes.