struct Foo;

impl Foo {
    fn num(&amp;mut self) -> usize { 0 }
    fn index(&amp;mut self, _i: usize) { }
}

let foo = Foo;
foo.index(foo.num()); //error

[–] sirdorius 2 points 1 year ago* (last edited 1 year ago)

This looks like a pretty easy fix that the compiler could do by extracting the argument to a temp variable to improve the syntax of the language.

[–] KillTheMule 1 points 1 year ago* (last edited 1 year ago) (1 children)

Note that when you change num to take &self instead, this works out (you also need to mark foo as mutable, of course).

[–] hairyballs 1 points 1 year ago

It's a toy example. In that case, the solution is to assign the expression to a variable to compute its result upfront.