Unhandled and undesired borrow error

[timfennis]

let x = 0
let g = fn(a, b) { print(x); a + b }
x g= 3

outputs:

thread 'main' panicked at src/interpreter/environment.rs:154:20:
already mutably borrowed: BorrowError

[timfennis]

Attempted a bad fix but it's probably not going to work.

The problem is that evaluating g wants to borrow x when printing, but it also hold a mutable borrow to x. I fixed this implementation but there are also implication for this case.

let x = %{0: 0};
let g = fn(a, b) { print(x); a + b };
x[0] g= 3;

which errors like this:

thread 'main' panicked at src/interpreter/sequence.rs:89:33:
already mutably borrowed: BorrowError
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace