Reimplement entity equality

New implementation of entity equality rewriter, which follows exact
entity (and anonymous) from roots to the comparison expression, for
more precise rewriting.

Closes #15588

src/EFCore/Diagnostics/CoreEventId.cs

@@ -236,7 +236,7 @@ private enum Id
         ///         This event is in the <see cref="DbLoggerCategory.Query" /> category.
         ///     </para>
         ///     <para>
-        ///         This event uses the <see cref="NavigationPathEventData" /> payload when used with a <see cref="DiagnosticSource" />.
+        ///         This event uses the <see cref="NavigationEventData" /> payload when used with a <see cref="DiagnosticSource" />.
         ///     </para>
         /// </summary>
         public static readonly EventId PossibleUnintendedCollectionNavigationNullComparisonWarning

src/EFCore/Diagnostics/CoreLoggerExtensions.cs

@@ -503,10 +503,10 @@ public static void SensitiveDataLoggingEnabledWarning<TLoggerCategory>(
         ///     Logs for the <see cref="CoreEventId.PossibleUnintendedCollectionNavigationNullComparisonWarning" /> event.
         /// </summary>
         /// <param name="diagnostics"> The diagnostics logger to use. </param>
-        /// <param name="navigationPath"> The navigation properties being used. </param>
+        /// <param name="navigation"> The navigation being used. </param>
         public static void PossibleUnintendedCollectionNavigationNullComparisonWarning(
             [NotNull] this IDiagnosticsLogger<DbLoggerCategory.Query> diagnostics,
-            [NotNull] IReadOnlyList<IPropertyBase> navigationPath)
+            [NotNull] INavigation navigation)
         {
             var definition = CoreResources.LogPossibleUnintendedCollectionNavigationNullComparison(diagnostics);
 
@@ -516,25 +516,25 @@ public static void PossibleUnintendedCollectionNavigationNullComparisonWarning(
                 definition.Log(
                     diagnostics,
                     warningBehavior,
-                    string.Join(".", navigationPath.Select(p => p.Name)));
+                    $"{navigation.DeclaringEntityType.Name}.{navigation.GetTargetType().Name}");
             }
 
             if (diagnostics.DiagnosticSource.IsEnabled(definition.EventId.Name))
             {
                 diagnostics.DiagnosticSource.Write(
                     definition.EventId.Name,
-                    new NavigationPathEventData(
+                    new NavigationEventData(
                         definition,
                         PossibleUnintendedCollectionNavigationNullComparisonWarning,
-                        navigationPath));
+                        navigation));
             }
         }
 
         private static string PossibleUnintendedCollectionNavigationNullComparisonWarning(EventDefinitionBase definition, EventData payload)
         {
             var d = (EventDefinition<string>)definition;
-            var p = (NavigationPathEventData)payload;
-            return d.GenerateMessage(string.Join(".", p.NavigationPath.Select(pb => pb.Name)));
+            var p = (NavigationEventData)payload;
+            return d.GenerateMessage($"{p.Navigation.DeclaringEntityType.Name}.{p.Navigation.GetTargetType().Name}");
         }
 
         /// <summary>

src/EFCore/Extensions/Internal/ExpressionExtensions.cs

@@ -373,35 +373,6 @@ public static bool IsNullPropagationCandidate(
             return true;
         }
 
-        /// <summary>
-        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
-        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
-        ///     any release. You should only use it directly in your code with extreme caution and knowing that
-        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
-        /// </summary>
-        public static Expression CreateKeyAccessExpression(
-            [NotNull] this Expression target,
-            [NotNull] IReadOnlyList<IProperty> properties)
-        {
-            Check.NotNull(target, nameof(target));
-            Check.NotNull(properties, nameof(properties));
-
-            return properties.Count == 1
-                ? target.CreateEFPropertyExpression(properties[0])
-                : Expression.New(
-                    AnonymousObject.AnonymousObjectCtor,
-                    Expression.NewArrayInit(
-                        typeof(object),
-                        properties
-                            .Select(
-                                p =>
-                                    Expression.Convert(
-                                        target.CreateEFPropertyExpression(p),
-                                        typeof(object)))
-                            .Cast<Expression>()
-                            .ToArray()));
-        }
-
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
         ///     the same compatibility standards as public APIs. It may be changed or removed without notice in

src/EFCore/Properties/CoreStrings.resx

@@ -1168,4 +1168,7 @@
   <data name="NoNavigation" xml:space="preserve">
     <value>There is no navigation on entity type '{entityType}' associated with the foreign key {foreignKey}.</value>
   </data>
-</root>
+  <data name="SubqueryWithCompositeKeyNotSupported" xml:space="preserve">
+    <value>This query would cause multiple evaluation of a subquery because entity '{entityType}' has a composite key. Rewrite your query avoiding the subquery.</value>
+  </data>
+</root>