sortedList.DeepClone() and immutableDictionary.DeepClone() don't compile (CS0121 ambiguous between the IDictionary and IReadOnlyDictionary overloads) #86

What's wrong

SortedList<TKey,TValue>, ImmutableDictionary<TKey,TValue> and ImmutableSortedDictionary<TKey,TValue> each implement both IDictionary<TKey,TValue> and IReadOnlyDictionary<TKey,TValue>. DeepCloneContainerExtensions has an extension for each interface (DeepClone(this IDictionary<,>) at line 148 and DeepClone(this IReadOnlyDictionary<,>) at line 268), and neither is more specific, so calling .DeepClone() directly on these types fails to compile.

#81 (commit dad2dfc) fixed this ambiguity for ConcurrentDictionary and ReadOnlyDictionary by adding concrete overloads. The three types above still have the problem. The existing ImmutableDictionary test avoids it by cloning each value by hand instead of calling the extension, so the tests don't catch it.

Reproduction

using System.Collections.Immutable;
using ktsu.DeepClone;

var a = new SortedList<string, int> { ["a"] = 1 }.DeepClone();
var b = ImmutableDictionary<string, int>.Empty.Add("a", 1).DeepClone();
var c = ImmutableSortedDictionary<string, int>.Empty.Add("a", 1).DeepClone();

error CS0121: The call is ambiguous between the following methods or properties:
'DeepCloneContainerExtensions.DeepClone<TKey, TValue>(IDictionary<TKey, TValue>)' and
'DeepCloneContainerExtensions.DeepClone<TKey, TValue>(IReadOnlyDictionary<TKey, TValue>)'

(Reproduced against the net10.0 build of current main.)

Why it matters

The README says the library clones standard collections, but a caller holding a SortedList or an immutable dictionary has to cast to one of the interfaces first. The IDictionary path then returns a plain Dictionary and loses the comparer and the sort order (tracked in #83). No cast gives back the type they started with.

Suggested fix / acceptance criteria

• Add concrete overloads, matching the dictionary.DeepClone() fails to compile (CS0121 ambiguous call) for Dictionary, SortedDictionary and ConcurrentDictionary, although the XML doc example shows that call #81 fix, that return the same type and keep its comparer:
  • SortedList<K,V> DeepClone(this SortedList<K,V>) built with new SortedList<K,V>(source.Count, source.Comparer)
  • ImmutableDictionary<K,V> DeepClone(this ImmutableDictionary<K,V>) built with ImmutableDictionary.CreateRange(source.KeyComparer, source.ValueComparer, clonedPairs)
  • ImmutableSortedDictionary<K,V> DeepClone(this ImmutableSortedDictionary<K,V>) built with source.KeyComparer and source.ValueComparer
• Add tests that call .DeepClone() directly on each type (so the test fails to compile if the ambiguity comes back), and check the result type, comparer and cloned values.