[MobiusHorizons]

I should probably have said, not compilable to efficient code. rather than not efficiently compilable. Basically I was referring to dynamic typing. Typically such languages are interpreted, although there is probably a way to compile the same sequence the interpreter would take as an AOT compiler. When types are not known until runtime, the compiler can't emit efficient code, and instead has to emit code that checks the type on each function invocation which is basically exactly what the interpreter was already doing. This is where JITs really shine, since they can produce one or more compilations of the same function specialized to types that have been observed to be used frequently. the interpreter can then call those specialized versions of the functions directly when appropriate.