GetSingleConstructorInvokerOrDefault/GetSingleConstructorInvoker changes

- made them internal
- make them additonal to existing counterparts
- add summaries

Author: alex-kulakov

Orm/Xtensive.Orm/Reflection/TypeHelper.cs

@@ -55,9 +55,9 @@ public int GetHashCode((Type, Type[]) obj)
 
 #if NET8_0_OR_GREATER
     private static readonly ConcurrentDictionary<(Type, Type[]), ConstructorInvoker> ConstructorInvokerByTypes =
-#else
-    private static readonly ConcurrentDictionary<(Type, Type[]), ConstructorInfo> ConstructorInfoByTypes =
+      new(new TypesEqualityComparer());
 #endif
+    private static readonly ConcurrentDictionary<(Type, Type[]), ConstructorInfo> ConstructorInfoByTypes =
       new(new TypesEqualityComparer());
 
     private static readonly ConcurrentDictionary<Type, Type[]> OrderedInterfaces = new();
@@ -645,34 +645,49 @@ public static object Activate(this Type type, Type[] genericArguments, params ob
       }
     }
 
+#if NET8_0_OR_GREATER
     /// <summary>
-    /// Gets the public constructor of type <paramref name="type"/>
+    /// Gets <see cref="ConstructorInvoker"/> of the public constructor of type <paramref name="type"/>
     /// accepting specified <paramref name="argumentTypes"/>.
     /// </summary>
     /// <param name="type">The type to get the constructor for.</param>
     /// <param name="argumentTypes">The arguments.</param>
     /// <returns>
-    /// Appropriate constructor, if a single match is found;
+    /// Appropriate constructor invoker, if a single match is found;
     /// otherwise throws <see cref="InvalidOperationException"/>.
     /// </returns>
     /// <exception cref="InvalidOperationException">
     /// The <paramref name="type"/> has no constructors suitable for <paramref name="argumentTypes"/>
     /// -or- more than one such constructor.
     /// </exception>
-#if NET8_0_OR_GREATER
-    public static ConstructorInvoker GetSingleConstructorInvoker(this Type type, Type[] argumentTypes) =>
+    internal static ConstructorInvoker GetSingleConstructorInvoker(this Type type, Type[] argumentTypes) =>
       ConstructorInvokerByTypes.GetOrAdd((type, argumentTypes),
         static t => ConstructorExtractor(t) is ConstructorInfo ctor
          ? ConstructorInvoker.Create(ctor)
          : throw new InvalidOperationException(Strings.ExGivenTypeHasNoOrMoreThanOneCtorWithGivenParameters));
-#else
+
+#endif
+    /// <summary>
+    /// Gets the public constructor of type <paramref name="type"/>
+    /// accepting specified <paramref name="argumentTypes"/>.
+    /// </summary>
+    /// <param name="type">The type to get the constructor for.</param>
+    /// <param name="argumentTypes">The arguments.</param>
+    /// <returns>
+    /// Appropriate constructor, if a single match is found;
+    /// otherwise throws <see cref="InvalidOperationException"/>.
+    /// </returns>
+    /// <exception cref="InvalidOperationException">
+    /// The <paramref name="type"/> has no constructors suitable for <paramref name="argumentTypes"/>
+    /// -or- more than one such constructor.
+    /// </exception>
     public static ConstructorInfo GetSingleConstructor(this Type type, Type[] argumentTypes) =>
       ConstructorInfoByTypes.GetOrAdd((type, argumentTypes), ConstructorExtractor)
         ?? throw new InvalidOperationException(Strings.ExGivenTypeHasNoOrMoreThanOneCtorWithGivenParameters);
-#endif
 
+#if NET8_0_OR_GREATER
     /// <summary>
-    /// Gets the public constructor of type <paramref name="type"/>
+    /// Gets <see cref="ConstructorInvoker"/> of the public constructor of type <paramref name="type"/>
     /// accepting specified <paramref name="argumentTypes"/>.
     /// </summary>
     /// <param name="type">The type to get the constructor for.</param>
@@ -682,14 +697,24 @@ public static ConstructorInfo GetSingleConstructor(this Type type, Type[] argume
     /// otherwise, <see langword="null"/>.
     /// </returns>
     [CanBeNull]
-#if NET8_0_OR_GREATER
-    public static ConstructorInvoker GetSingleConstructorInvokerOrDefault(this Type type, Type[] argumentTypes) =>
+    internal static ConstructorInvoker GetSingleConstructorInvokerOrDefault(this Type type, Type[] argumentTypes) =>
       ConstructorInvokerByTypes.GetOrAdd((type, argumentTypes),
         static t => ConstructorExtractor(t) is ConstructorInfo ctor ? ConstructorInvoker.Create(ctor) : null);
-#else
+
+#endif
+    /// <summary>
+    /// Gets the public constructor of type <paramref name="type"/>
+    /// accepting specified <paramref name="argumentTypes"/>.
+    /// </summary>
+    /// <param name="type">The type to get the constructor for.</param>
+    /// <param name="argumentTypes">The arguments.</param>
+    /// <returns>
+    /// Appropriate constructor, if a single match is found;
+    /// otherwise, <see langword="null"/>.
+    /// </returns>
+    [CanBeNull]
     public static ConstructorInfo GetSingleConstructorOrDefault(this Type type, Type[] argumentTypes) =>
       ConstructorInfoByTypes.GetOrAdd((type, argumentTypes), ConstructorExtractor);
-#endif
 
     private static readonly Func<(Type, Type[]), ConstructorInfo> ConstructorExtractor = t => {
       (var type, var argumentTypes) = t;