Scope
Every function and block ({ ... }) introduces a new scope for declarations.
Each function and block can refer to declarations in its scope or any of the outer scopes.
let x = 10
fun f(): Int {
let y = 10
return x + y
}
f() // is `20`
// Invalid: the identifier `y` is not in scope.
//
y
fun doubleAndAddOne(_ n: Int): Int {
fun double(_ x: Int) {
return x * 2
}
return double(n) + 1
}
// Invalid: the identifier `double` is not in scope.
//
double(1)
Each scope can introduce new declarations, i.e., the outer declaration is shadowed.
let x = 2
fun test(): Int {
let x = 3
return x
}
test() // is `3`
Scope is lexical, not dynamic.
let x = 10
fun f(): Int {
return x
}
fun g(): Int {
let x = 20
return f()
}
g() // is `10`, not `20`
Declarations are not moved to the top of the enclosing function (hoisted).
let x = 2
fun f(): Int {
if x == 0 {
let x = 3
return x
}
return x
}
f() // is `2`