let keyword

let introduces a new variable.

let x = 0
// Variables can be reassigned.
x = 1

You can add type annotations to let.

let x: List<Int> = []

If you have a tuple, you can use let to destructure the tuple elements.

let position = (1, 2)
let (x, y) = position

dbg(x) // 1
dbg(y) // 2

You can also use let to shadow variables, where you introduce a new variable that hides the old value.

let i = 0

if True {
  let i = 1
  dbg(i) // 1
  Unit
}

dbg(i) // 0