namespace System.Collections.Generic;
/// Values by their keys, read only: what a dictionary is to those that
/// mustn't change it.
[Intrinsic]
public interface IReadOnlyDictionary<TKey, TValue> : IReadOnlyCollection<KeyValuePair<TKey, TValue>> {
/// The value of `key`; a panic when it has none.
TValue this[TKey key] { get; }
IEnumerable<TKey> Keys { get; }
IEnumerable<TValue> Values { get; }
readonly bool ContainsKey(TKey key);
/// `key`'s value, or `null` when it has none.
readonly TValue? TryGetValue(TKey key);
}