// Copyright 2018 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. #![feature(rustc_attrs, const_fn)] #[rustc_args_required_const(0)] fn foo(_a: i32) { } #[rustc_args_required_const(1)] fn bar(_a: i32, _b: i32) { } const A: i32 = 3; const fn baz() -> i32 { 3 } fn main() { foo(2); foo(2 + 3); foo(baz()); let a = 4; foo(A); foo(a); //~ ERROR: argument 1 is required to be a constant bar(a, 3); bar(a, a); //~ ERROR: argument 2 is required to be a constant }