// Copyright 2015 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 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. // Test that a by-ref `FnMut` closure gets an error when it tries to // mutate a value. fn call(f: F) where F : Fn() { f(); } fn main() { let mut counter = 0_u32; call(|| { counter += 1; //~^ ERROR cannot assign to data in a captured outer variable in an `Fn` closure }); }