A value was moved whose size was not known at compile time.
Erroneous code example:
#![feature(box_syntax)]
trait Bar {
fn f(self);
}
impl Bar for i32 {
fn f(self) {}
}
fn main() {
let b: Box<dyn Bar> = box (0 as i32);
b.f();
// error: cannot move a value of type dyn Bar: the size of dyn Bar cannot
// be statically determined
}In Rust, you can only move a value when its size is known at compile time.
To work around this restriction, consider “hiding” the value behind a reference:
either &x or &mut x. Since a reference has a fixed size, this lets you move
it around as usual. Example:
#![feature(box_syntax)]
trait Bar {
fn f(&self);
}
impl Bar for i32 {
fn f(&self) {}
}
fn main() {
let b: Box<dyn Bar> = box (0 as i32);
b.f();
// ok!
}