Macro indexset_with_default 

macro_rules! indexset_with_default {
    () => { ... };
    ($H:ty $(;)?) => { ... };
    ($H:ty; $($value:expr),+ $(,)?) => { ... };
}

Create an IndexSet from a list of values and a BuildHasherDefault-wrapped custom hasher.

Example

use indexmap::indexset_with_default;
use std::collections::hash_map::DefaultHasher;

let set = indexset_with_default!{
    DefaultHasher;
    "a",
    "b",
};
assert!(set.contains("a"));
assert!(set.contains("b"));
assert!(!set.contains("c"));

// "a" is the first value
assert_eq!(set.iter().next(), Some(&"a"));

This can also be initialized in const contexts:

use indexmap::{IndexSet, indexset_with_default};
use std::collections::hash_map::DefaultHasher;
use std::hash::BuildHasherDefault;
use std::sync::Mutex;

type DefaultHashBuilder = BuildHasherDefault<DefaultHasher>;

static INTERN: Mutex<IndexSet<String, DefaultHashBuilder>> =
    Mutex::new(indexset_with_default!());

if let Ok(mut set) = INTERN.lock() {
    set.insert("a".into());
    set.insert("b".into());
    set.insert("c".into());
}

assert!(INTERN.lock().unwrap().contains("a"));
assert!(INTERN.lock().unwrap().contains("b"));
assert!(INTERN.lock().unwrap().contains("c"));