Should the mutable borrow of self in method call range over the arguments? #20403
Description
When a &mut self method is called, the receiver is mutably borrowed before the arguments are evaluated, so the following program does not compile:
fn main() {
let mut vec = vec![1, 2, 3];
vec.push(vec.len());
assert_eq!(vec, vec![1, 2, 3, 4]);
}
But when the argument explicitly evaluated before the call in a let statement, is compiles just fine:
fn main() {
let mut vec = vec![1, 2, 3];
let vec_len = vec.len();
vec.push(vec_len);
assert_eq!(vec, vec![1, 2, 3, 3]);
}
I am not sure if there is a good reason for the first program to be rejected, I would expect e1(e2) to be equivalent to { let x = e2; e1(x) }.