mirror of
https://github.com/rust-lang/rust.git
synced 2024-11-01 06:51:58 +00:00
21 lines
632 B
Rust
21 lines
632 B
Rust
// Ensure that you cannot use generic types to return a region outside
|
|
// of its bound. Here, in the `return_it()` fn, we call with() but
|
|
// with R bound to &isize from the return_it. Meanwhile, with()
|
|
// provides a value that is only good within its own stack frame. This
|
|
// used to successfully compile because we failed to account for the
|
|
// fact that fn(x: &isize) rebound the region &.
|
|
|
|
fn with<R, F>(f: F) -> R where F: FnOnce(&isize) -> R {
|
|
f(&3)
|
|
}
|
|
|
|
fn return_it<'a>() -> &'a isize {
|
|
with(|o| o)
|
|
//~^ ERROR lifetime may not live long enough
|
|
}
|
|
|
|
fn main() {
|
|
let x = return_it();
|
|
println!("foo={}", *x);
|
|
}
|