Pitch: `borrow` and `inout` declaration keywords

[orobio (Manolo van Ee)]

@TeamPuzel

For certain programs this new feature will be used more than var and let, it's not some niche optimisation keyword that will appear once every 1 000 lines of code in an iOS app.

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 {}