The following code compiles:
fn main() {
let directory_key = "a";
let object_key = "b";
let filepath = Path::new(&format!("{}/{}", directory_key, object_key));
// println!("{:?}", filepath);
}
However, if the println! line is commented in, the code encounters a compile-time error:
fn main() {
let directory_key = "a";
let object_key = "b";
let filepath = Path::new(&format!("{}/{}", directory_key, object_key));
println!("{:?}", filepath);
}
error[E0716]: temporary value dropped while borrowed
--> src/s3.rs:196:31
|
196 | let filepath = Path::new(&format!("{}/{}", directory_key, object_key));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - temporary value is freed at the end of this statement
| |
| creates a temporary which is freed while still in use
197 | println!("{:?}", filepath);
| -------- borrow later used here
|
= note: consider using a `let` binding to create a longer lived value
= note: this error originates in the macro `format` (in Nightly builds, run with -Z macro-backtrace for more info)
The error can be resolved by, as the compiler suggests, introducing a let binding to the result of format!. The below code demonstrates this solution:
fn main() {
let directory_key = "a";
let object_key = "b";
let filepath_string = format!("{}/{}", directory_key, object_key);
let filepath = Path::new(&filepath_string);
println!("{:?}", filepath);
}
Why does the E0717 error happen for the code from the second snippet? Does it have something to do with how format! works?
