SE-0519: Borrow and Inout types for safe, first-class references

[orobio (Manolo van Ee)]

This seemed to be one of the most liked spellings when I suggested something similar a couple of years ago. It was slightly different because I optimized for immutable bindings:

ref x = y      // immutable borrow
ref var x = &y // mutable borrow

for ref x in array {}
for ref var x in &array {}

Pitch: `borrow` and `inout` declaration keywords

I agree, it should be relatively easy to type. Just another suggestion: ref x = y // immutable borrow ref var x = &y // mutable borrow for ref x in array {} for ref var x in &array {}