Monomorphisation is the name of the technique of producing a different version of the code for each set of type parameters that are used in the program. C++ and Rust use monomorphisation instead of doing runtime checks because they're trading off slightly bigger binaries for greater speed.
By not doing runtime checks you get to skip that work at runtime, obviously, but you also get to enable other optimizations like inlining the monomorphised version.
By not doing runtime checks you get to skip that work at runtime, obviously, but you also get to enable other optimizations like inlining the monomorphised version.