rust/src/test/compile-fail/closure-no-fn.rs

// Copyright 2017 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.

// Ensure that capturing closures are never coerced to fns
// Especially interesting as non-capturing closures can be.

fn main() {
    let mut a = 0u8;
    let foo: fn(u8) -> u8 = |v: u8| { a += v; a };
    //~^ ERROR mismatched types
    let b = 0u8;
    let bar: fn() -> u8 = || { b };
    //~^ ERROR mismatched types
    let baz: fn() -> u8 = || { b } as fn() -> u8;
    //~^ ERROR mismatched types
    //~^^ ERROR non-scalar cast
}