need to use regular functions for `rec {}` getters but arrow functions for `{}` getters, to ensure that using `this` for property access works correctly

ADD TO TESTS:
let a = 0; in rec { a = 1; foo = bar: a * 2 }
# 2

let a = 0; in rec { a = 1; foo = let func = bar: a * 2; in rec { a = 3; baz = func; }; }
# 2