Passing an rvalue as ~self causes double-free

[thestinger]

This somehow causes a destructor to be called twice:

struct Foo {
    data: ~[int]
}

impl Foo {
    fn bar(~self) -> ~Foo { self }
}

fn main() {
    (~Foo{data: ~[1,2,3]}).bar();
}

[bblum]

6644da5 also points to this, which I ran into independently, though that problem might be something different? Looks like using v.consume() or v.partition() (possibly among others) always crash, and consume(v) and partition(v) work fine.

[nikomatsakis]

Not critical for 0.6; removing milestone

[erickt]

Here's an even simpler version of this bug:

trait A {
    fn a(self);
}

impl A for ~int {
    fn a(self) { }
}

fn main() {
    (~1).a();
}

However, if we use ~self it works fine:

trait A {
    fn a(~self);
}

impl A for int {
    fn a(~self) { }
}

fn main() {
    (~1).a();
}

[Blei]

This seems to be fixed on master.

[Blei]

Correction: the "simpler version" now runs correctly, the original code still segfaults.

[bblum]

I believe the problem is only for rvalues.

use std::util;

struct Foo;

impl Foo {
    fn eat(~self) { util::ignore(self); }
}

fn main() {
    (~Foo).eat();
}

This dies, but works fine if you change it to:

let x = ~Foo;
x.eat();