Projection to SQL fails while using Math.Floor with LINQ Sum expression

[JuliusSenkus]

Bug

Failing to project SQL expression when Math.Floor is used inside Sum (if retrieving only sum, no other properties, everything works like expected). By documentation it seems, that it simply should wrap contents with ROUND function.

Sample code:

// See https://aka.ms/new-console-template for more information
using Microsoft.EntityFrameworkCore;

using var ctx = new MyContext();
ctx.Database.EnsureDeleted();
ctx.Database.EnsureCreated();
ctx.Carts.Add(
    new Cart { 
        Name = "Candy", 
        CartItems = new List<CartItem> { 
        new CartItem { Name = "Candy", Price = 1.15M, Quantity = 1.15M, }, 
        new CartItem { Name = "Salty Candy", Price = 1.15M, Quantity = 1.15M, }, 
        } 
    });
ctx.SaveChanges();

var cartsV1 = ctx.Carts.Select(c => new { Cart = c.Name, TotalAmount = c.CartItems.Sum(i => Math.Round(i.Quantity * i.Price, 2)), }).ToList();
var cartsV2 = ctx.Carts.Select(c => new { Cart = c.Name, TotalAmount = c.CartItems.Select(i => i.Quantity * i.Price).Sum(i => Math.Round(i, 2)), }).ToList();

Console.WriteLine($"Cart value: {cartsV1.First().TotalAmount}");

public class CartItem
{
    public Guid Id { get; set; }
    public string Name { get; set; } = String.Empty;
    public decimal Price { get; set; }
    public decimal Quantity { get; set; }
}

public class Cart {
    public Guid Id { get; set; }
    public string Name { get; set; } = String.Empty;
    public ICollection<CartItem> CartItems { get; set; } = new List<CartItem>();
}

public class MyContext : DbContext {
    public DbSet<Cart> Carts { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) {
        optionsBuilder.UseSqlServer(@"Server=(localdb)\MSSQLLocalDB;Database=FailedConversion;Integrated Security=true;");
    }
}

Stack traces:

   at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.ApplyProjection(Expression shaperExpression, ResultCardinality resultCardinality, QuerySplittingBehavior querySplittingBehavior)
   at Microsoft.EntityFrameworkCore.Query.Internal.SelectExpressionProjectionApplyingExpressionVisitor.VisitExtension(Expression extensionExpression)
   at System.Linq.Expressions.Expression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryTranslationPostprocessor.Process(Expression query)
   at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutor[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](Expression query, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](IDatabase database, Expression query, IModel model, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass9_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetEnumerator()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Program.<Main>$(String[] args) in C:\Users\Julius.Senkus\Documents\Projects\TestProjects\TestConsole\TestConsole\Program.cs:line 17

Provider and version information

EF Core version: 6.0.1
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 6.0
Operating system: Windows 10
IDE: Visual Studio 2022

[JuliusSenkus]

For anyone else simplest option to workaround this issue would be multiply everything by one:

-  var cartsV1 = ctx.Carts.Select(c => new { Cart = c.Name, TotalAmount = c.CartItems.Sum(i => Math.Round(i.Quantity * i.Price, 2)), }).ToList();
+  var cartsV1 = ctx.Carts.Select(c => new { Cart = c.Name, TotalAmount = c.CartItems.Select(i => Math.Round(i.Quantity * i.Price, 2)).Select(t => t * 1).Sum(), }).ToList();
// Desired result: `SUM(ROUND(c.Quantity * c.Price, 2))`
// Workaround solution: `SUM(ROUND(c.Quantity * c.Price, 2) * 1)`

From ef core code what I saw, it fails on not being able to extract the type from Math.Round expressions (innerSelectExpression.Limit is null).