Drop the unused new() constraint from GetOrCreate(key, defaultValue)

Extensions.Test/DictionaryExtensionsTests.cs

@@ -42,6 +42,52 @@ public void GetOrCreateShouldAddAndReturnDefaultValue()
 		Assert.AreEqual(99, dictionary["key1"]);
 	}
 
+	// The overloads that take a default value never construct one, so they must not demand a
+	// parameterless constructor. Strings and interfaces have none, and these tests would not compile
+	// if the constraint came back.
+
+	[TestMethod]
+	public void GetOrCreateWithDefaultShouldAcceptAStringValue()
+	{
+		Dictionary<int, string> dictionary = [];
+
+		Assert.AreEqual("one", dictionary.GetOrCreate(1, "one"));
+		Assert.AreEqual("one", dictionary.GetOrCreate(1, "uno"));
+		Assert.HasCount(1, dictionary);
+	}
+
+	[TestMethod]
+	public void GetOrCreateWithDefaultShouldAcceptAnInterfaceValue()
+	{
+		Dictionary<int, IList<int>> dictionary = [];
+		List<int> first = [1];
+
+		Assert.AreSame(first, dictionary.GetOrCreate(1, first));
+		Assert.AreSame(first, dictionary.GetOrCreate(1, []));
+		Assert.HasCount(1, dictionary);
+	}
+
+	[TestMethod]
+	public void GetOrCreateConcurrentDictionaryWithDefaultShouldAcceptAStringValue()
+	{
+		ConcurrentDictionary<int, string> dictionary = new();
+
+		Assert.AreEqual("one", dictionary.GetOrCreate(1, "one"));
+		Assert.AreEqual("one", dictionary.GetOrCreate(1, "uno"));
+		Assert.HasCount(1, dictionary);
+	}
+
+	[TestMethod]
+	public void GetOrCreateConcurrentDictionaryWithDefaultShouldAcceptAnInterfaceValue()
+	{
+		ConcurrentDictionary<int, IList<int>> dictionary = new();
+		List<int> first = [1];
+
+		Assert.AreSame(first, dictionary.GetOrCreate(1, first));
+		Assert.AreSame(first, dictionary.GetOrCreate(1, []));
+		Assert.HasCount(1, dictionary);
+	}
+
 	[TestMethod]
 	public void GetOrCreateConcurrentDictionaryShouldReturnExistingValue()
 	{

Extensions/DictionaryExtensions.cs

@@ -28,19 +28,19 @@
 	/// <param name="key">The key to get the value for.</param>
 	/// <param name="defaultValue">The default value to add when an existing value is not found.</param>
 	/// <returns>The value for the key if it exists, otherwise a new value.</returns>
-	public static TVal GetOrCreate<TKey, TVal>(this IDictionary<TKey, TVal> dictionary, TKey key, TVal defaultValue) where TKey : notnull where TVal : notnull, new()
+	public static TVal GetOrCreate<TKey, TVal>(this IDictionary<TKey, TVal> dictionary, TKey key, TVal defaultValue) where TKey : notnull where TVal : notnull
 	{
 #pragma warning disable KTSU0004 // Use Ensure.NotNull instead of manual null check
 		if (dictionary is null)
 		{
 			throw new ArgumentNullException(nameof(dictionary), "The dictionary cannot be null.");
 		}
 #pragma warning restore KTSU0004 // Use Ensure.NotNull instead of manual null check
 
 #pragma warning disable KTSU0004 // Use Ensure.NotNull instead of manual null check
 		if (key is null)
 		{
 			throw new ArgumentNullException(nameof(key), "The key cannot be null.");
 		}
 #pragma warning restore KTSU0004 // Use Ensure.NotNull instead of manual null check
 
@@ -98,7 +98,7 @@
 	/// <param name="key">The key to get the value for.</param>
 	/// <param name="defaultValue">The default value to add when an existing value is not found.</param>
 	/// <returns>The value for the key if it exists, otherwise a new value.</returns>
-	public static TVal GetOrCreate<TKey, TVal>(this ConcurrentDictionary<TKey, TVal> dictionary, TKey key, TVal defaultValue) where TKey : notnull where TVal : new()
+	public static TVal GetOrCreate<TKey, TVal>(this ConcurrentDictionary<TKey, TVal> dictionary, TKey key, TVal defaultValue) where TKey : notnull
 	{
 #pragma warning disable KTSU0004 // Use Ensure.NotNull instead of manual null check
 		if (dictionary is null)