rust/src/test/ui/no-warn-on-field-replace-issue-34101.rs
2018-12-25 21:08:33 -07:00

47 lines
1.1 KiB
Rust

// Issue 34101: Circa 2016-06-05, `fn inline` below issued an
// erroneous warning from the elaborate_drops pass about moving out of
// a field in `Foo`, which has a destructor (and thus cannot have
// content moved out of it). The reason that the warning is erroneous
// in this case is that we are doing a *replace*, not a move, of the
// content in question, and it is okay to replace fields within `Foo`.
//
// Another more subtle problem was that the elaborate_drops was
// creating a separate drop flag for that internally replaced content,
// even though the compiler should enforce an invariant that any drop
// flag for such subcontent of `Foo` will always have the same value
// as the drop flag for `Foo` itself.
// compile-pass
struct Foo(String);
impl Drop for Foo {
fn drop(&mut self) {}
}
fn inline() {
// (dummy variable so `f` gets assigned `var1` in MIR for both fn's)
let _s = ();
let mut f = Foo(String::from("foo"));
f.0 = String::from("bar");
}
fn outline() {
let _s = String::from("foo");
let mut f = Foo(_s);
f.0 = String::from("bar");
}
fn main() {
inline();
outline();
}