[rockdoe]

If the language defers explicitness until runtime then there's nothing a compiler or interpreter can do to get rid of the overhead.

With things like a JIT it can see it at runtime, but that's still overhead to handle the detection and the bail-out situations.

[cmpitg]

I agree on the overhead. There are information available only at run-time that could be (and actually has been, in case of interpreter like PicoLisp) used to have better optimization compared to compiled code. It isn't technically faster or slower.

Edited: Correct my bad grammar.