I was surprised to see that it is possible to write:
for i = 0…4 {
let k = i
print( k )
}
with an evolving value of k although it is a constant.
Then I realised that the scope of k was delimited by the braces {}
I checked this assumption by writing the following code without compiler complaint:
if true {
let k = 15
}
if true {
let k = 33
}