But how do you know just by reading that code? It would not be obvious to me at all.

I think it's quite fine to assume the reader knows enough rust to know the difference between mutable and immutable variables.

let foo = bar; let foo = bat;

is shadowing

let foo = bar; foo = bat;

is a compilation-time error because foo isn't mutable.

let mut foo = bar; foo = bat;

is reassignment.

in working code, either foo is declared as mutable or it's not, and it's pretty obvious from the code what's happening.

I guess. I would just never write code like that.

You mean if you don't know the language?

I guess I just need to learn Rust. I wouldn't write a style of code where I have 3 lets after an other and using the same variable name.

I guess if you don't know rust you might not? But one of the first things you learn about rust is the `mut` keyword.

`let` rebinds. If there isn't a `let`, it's mutation.