[__s]

Lua gets sone perf with simple types that can represent lots of types without pointers easily. Truthiness is also fast since only nil/false singletons are falsy. Whereas Python has ´__bool__´. But look at metatable stuff for how much lua has to check

All of these introduce guards in with JIT or inline cache, preferable to have no guard at all

This isn't unique to dynamic languages, see C++ map having a layer of indirection forced to support pointer lifetimes of access living past inserts. Whereas Rust doesn't allow borrowing past that, & Go doesn't allow taking address of map value

Other examples: C optimizations having to worry about pointer aliasing. Or Go interfaces having to box everything. It used to have small value types be able to avoid boxing for interface value, but dropped when switching to precise GC