src/test/ui/closures/closure-expected-type/expect-region-supply-region.rs

// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#![allow(warnings)]

fn closure_expecting_bound<F>(_: F)
    where F: FnOnce(&u32)
{
}

fn closure_expecting_free<'a, F>(_: F)
    where F: FnOnce(&'a u32)
{
}

fn expect_bound_supply_nothing() {
    // Because `x` is inferred to have a bound region, we cannot allow
    // it to escape into `f`:
    let mut f: Option<&u32> = None;
    closure_expecting_bound(|x| {
        f = Some(x); //~ ERROR borrowed data cannot be stored outside of its closure
    });
}

fn expect_bound_supply_bound() {
    // Because `x` is inferred to have a bound region, we cannot allow
    // it to escape into `f`, even with an explicit type annotation on
    // closure:
    let mut f: Option<&u32> = None;
    closure_expecting_bound(|x: &u32| {
        f = Some(x); //~ ERROR borrowed data cannot be stored outside of its closure
    });
}

fn expect_bound_supply_named<'x>() {
    let mut f: Option<&u32> = None;

    // Here we give a type annotation that `x` should be free. We get
    // an error because of that.
    closure_expecting_bound(|x: &'x u32| {
        //~^ ERROR mismatched types
        //~| ERROR mismatched types

        // And we still cannot let `x` escape into `f`.
        f = Some(x);
        //~^ ERROR borrowed data cannot be stored outside of its closure
    });
}

fn expect_free_supply_nothing() {
    let mut f: Option<&u32> = None;
    closure_expecting_free(|x| f = Some(x)); // OK
}

fn expect_free_supply_bound() {
    let mut f: Option<&u32> = None;

    // Here, even though the annotation `&u32` could be seen as being
    // bound in the closure, we permit it to be defined as a free
    // region (which is inferred to something in the fn body).
    closure_expecting_free(|x: &u32| f = Some(x)); // OK
}

fn expect_free_supply_named<'x>() {
    let mut f: Option<&u32> = None;

    // Here, even though the annotation `&u32` could be seen as being
    // bound in the closure, we permit it to be defined as a free
    // region (which is inferred to something in the fn body).
    closure_expecting_free(|x: &'x u32| f = Some(x)); // OK
}

fn main() { }