[API Proposal]: Factory methods to create immutable dictionary instances from dictionary expressions

[cston]

Background and motivation

Add factory methods to allow creating instances of immutable dictionary types from dictionary expressions.

API Proposal

namespace System.Collections.Immutable
{
    [CollectionBuilder(typeof(ImmutableDictionary), nameof(ImmutableDictionary.CreateRange))]
    public sealed class ImmutableDictionary<TKey, TValue> : IDictionary<TKey, TValue> //, ...
    {
        // ...
    }

    public static class ImmutableDictionary
    {
        public static ImmutableDictionary<TKey, TValue> CreateRange<TKey, TValue>(
            ReadOnlySpan<KeyValuePair<TKey, TValue>> collection)
            where TKey : notnull;

        public static ImmutableDictionary<TKey, TValue> CreateRange<TKey, TValue>(
            IEqualityComparer<TKey> keyComparer,
            ReadOnlySpan<KeyValuePair<TKey, TValue>> collection)
            where TKey : notnull;
    }
}

namespace System.Collections.Frozen
{
    [CollectionBuilder(typeof(FrozenDictionary), nameof(FrozenDictionary.Create))]
    public abstract class FrozenDictionary<TKey, TValue> : IDictionary<TKey, TValue> //, ...
    {
        // ...
    }

    public static class FrozenDictionary
    {
        public static FrozenDictionary<TKey, TValue> Create<TKey, TValue>(
            ReadOnlySpan<KeyValuePair<TKey, TValue>> collection)
            where TKey : notnull;

        public static FrozenDictionary<TKey, TValue> Create<TKey, TValue>(
            IEqualityComparer<TKey> comparer,
            ReadOnlySpan<KeyValuePair<TKey, TValue>> collection)
            where TKey : notnull;
    }
}

API Usage

ImmutableDictionary<string, int> x = [with(StringComparer.Ordinal), "one":1, "two":2];

FrozenDictionary<string, int> y = [with(comparer: null), "three":3];

Alternative Designs

No response

Risks

No response

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-collections
See info in area-owners.md if you want to be subscribed.

[bartonjs]

Video

Looks good as proposed

namespace System.Collections.Immutable
{
    [CollectionBuilder(typeof(ImmutableDictionary), nameof(ImmutableDictionary.CreateRange))]
    public sealed class ImmutableDictionary<TKey, TValue> : IDictionary<TKey, TValue> //, ...
    {
        // ...
    }

    public static class ImmutableDictionary
    {
        public static ImmutableDictionary<TKey, TValue> CreateRange<TKey, TValue>(
            ReadOnlySpan<KeyValuePair<TKey, TValue>> collection)
            where TKey : notnull;

        public static ImmutableDictionary<TKey, TValue> CreateRange<TKey, TValue>(
            IEqualityComparer<TKey> keyComparer,
            ReadOnlySpan<KeyValuePair<TKey, TValue>> collection)
            where TKey : notnull;
    }
}

namespace System.Collections.Frozen
{
    [CollectionBuilder(typeof(FrozenDictionary), nameof(FrozenDictionary.Create))]
    public abstract class FrozenDictionary<TKey, TValue> : IDictionary<TKey, TValue> //, ...
    {
        // ...
    }

    public static class FrozenDictionary
    {
        public static FrozenDictionary<TKey, TValue> Create<TKey, TValue>(
            ReadOnlySpan<KeyValuePair<TKey, TValue>> collection)
            where TKey : notnull;

        public static FrozenDictionary<TKey, TValue> Create<TKey, TValue>(
            IEqualityComparer<TKey> comparer,
            ReadOnlySpan<KeyValuePair<TKey, TValue>> collection)
            where TKey : notnull;
    }
}