Address review feedback: use var, explicit key values, proper Cosmos override

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: roji

src/EFCore.Relational/Query/RelationalShapedQueryCompilingExpressionVisitor.ShaperProcessingExpressionVisitor.cs

@@ -1479,7 +1479,7 @@ Expression CompensateForCollectionMaterialization(ParameterExpression parameter,
             {
                 if (_containsCollectionMaterialization)
                 {
-                    Expression expressionToAdd = parameter;
+                    var expressionToAdd = (Expression)parameter;
                     if (expressionToAdd.Type.IsValueType)
                     {
                         expressionToAdd = Convert(expressionToAdd, typeof(object));

test/EFCore.Cosmos.FunctionalTests/Query/Associations/ComplexProperties/ComplexPropertiesCollectionCosmosTest.cs

@@ -221,9 +221,12 @@ FROM root c
     }
 
 
-    // Cosmos doesn't support entity collection navigations across documents.
-    public override Task Project_struct_complex_type_with_entity_collection_navigation()
-        => Task.CompletedTask;
+    public override async Task Project_struct_complex_type_with_entity_collection_navigation()
+    {
+        await base.Project_struct_complex_type_with_entity_collection_navigation();
+
+        AssertSql();
+    }
 
     [ConditionalFact]
     public virtual void Check_all_tests_overridden()

test/EFCore.Specification.Tests/Query/Associations/ComplexProperties/ComplexPropertiesCollectionTestBase.cs

@@ -17,8 +17,9 @@ public virtual async Task Project_struct_complex_type_with_entity_collection_nav
             {
                 context.Add(new Context37926.Parent
                 {
+                    Id = 1,
                     Coords = new Context37926.Coords { X = 1, Y = 2 },
-                    Children = [new() { Name = "Child1" }]
+                    Children = [new() { Id = 1, Name = "Child1" }]
                 });
                 await context.SaveChangesAsync();
             });
@@ -37,12 +38,17 @@ public virtual async Task Project_struct_complex_type_with_entity_collection_nav
     protected class Context37926(DbContextOptions options) : DbContext(options)
     {
         protected override void OnModelCreating(ModelBuilder modelBuilder)
-            => modelBuilder.Entity<Parent>(b =>
+        {
+            modelBuilder.Entity<Parent>(b =>
             {
+                b.Property(e => e.Id).ValueGeneratedNever();
                 b.ComplexProperty(e => e.Coords);
                 b.HasMany(e => e.Children).WithOne().HasForeignKey(c => c.ParentId);
             });
 
+            modelBuilder.Entity<Child>().Property(e => e.Id).ValueGeneratedNever();
+        }
+
         public class Parent
         {
             public int Id { get; set; }