[ufo]

The main advantage is that anything that you can turn into a a type error will be reported at compilation time, much earlier in the development cycle. This is not just a matter of safety but also helps in terms of refactoring and testing.

This includes things like typos (wrong method names, etc) but where types really shine is refactoring. If you want to add or remove a parameter from a function or change a string field to an integer then you can use guidance from the type checker to be sure that you didn't forget to update anything. Its a bit like adding bumpers to the side of the bowling lane - it lets you be more reckless, updating things until the compiler shuts up without needing to carefully go through each line.

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Also, don't forget that gradual typing solutions such as Typed Lua are all about letting you program dynamically if you want. The idea is that you would only convert to the typed dialect in the parts of your program where that would suit you.