src/test/run-pass/issue-41803.rs


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// 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.

/// A compile-time map from identifiers to arbitrary (heterogeneous) expressions
macro_rules! ident_map {
    ( $name:ident = { $($key:ident => $e:expr,)* } ) => {
        macro_rules! $name {
            $(
                ( $key ) => { $e };
            )*
            // Empty invocation expands to nothing. Needed when the map is empty.
            () => {};
        }
    };
}

ident_map!(my_map = {
    main => 0,
});

fn main() {
    my_map!(main);
}