rust/tests/ui/nll/closure-requirements/escape-argument.rs

// Test closure that:
//
// - takes an argument `y`
// - stores `y` into another, longer-lived spot
//
// but is invoked with a spot that doesn't live long
// enough to store `y`.
//
// The error is reported in the caller: invoking the closure links the
// lifetime of the variable that is given as `y` (via subtyping) and
// thus forces the corresponding borrow to live too long. This is
// basically checking that the MIR type checker correctly enforces the
// closure signature.

//@ compile-flags:-Zverbose-internals

#![feature(rustc_attrs)]

#[rustc_regions]
fn test() {
    let x = 44;
    let mut p = &x;

    {
        let y = 22;
        let mut closure = expect_sig(|p, y| *p = y);
        closure(&mut p, &y);
        //~^ ERROR `y` does not live long enough [E0597]
    }

    deref(p);
}

fn expect_sig<F>(f: F) -> F
    where F: for<'a, 'b> FnMut(&'a mut &'b i32, &'b i32)
{
    f
}

fn deref(_p: &i32) { }

fn main() { }