What's New in v1.12

v1.12 brings real closures, proper generics, and auto-derived methods.

Real Closures

Lambdas now properly capture variables from their enclosing scope. This works with .map(), .filter(), .reduce(), and return closures.

var nums = [1, 2, 3, 4, 5]
var factor = 10
var scaled = nums.map(|x| x * factor)
// scaled = [10, 20, 30, 40, 50]

var threshold = 3
var big = nums.filter(|x| x > threshold)
// big = [4, 5]

Closure Factories

fn make_adder(x: int) -> fn(int) -> int {
    return |y| x + y
}

var add5 = make_adder(5)
println(add5(10))  // 15

Auto-derive to_string()

All structs automatically get a to_string() method:

struct Point { x: int, y: int }

var p = Point { x: 42, y: 99 }
println(p.to_string())  // Point(x=42, y=99)

Proper Generic Type Equality

The type system now correctly distinguishes between different generic instantiations. List<int> and List<string> are properly recognized as different types.