2.1 regression: "variable referenced from scope '', but it is not defined" exception in GroupBy query translation

[JesperTreetop]

A particular form of GroupBy seems to not work with 2.1 yet worked flawlessly in 2.0.

Exception message: variable 'secondGroup' of type 'System.Linq.IGrouping`2[<>f__AnonymousType0`3[System.String,System.Decimal,System.DateTime],EF21Regression.DbC]' referenced from scope '', but it is not defined
Stack trace:
   at System.Linq.Expressions.Compiler.VariableBinder.Reference(ParameterExpression node, VariableStorageKind storage)
   at System.Linq.Expressions.Compiler.VariableBinder.VisitParameter(ParameterExpression node)
   at System.Linq.Expressions.ParameterExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Linq.Expressions.ExpressionVisitor.VisitMember(MemberExpression node)
   at System.Linq.Expressions.MemberExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Linq.Expressions.ExpressionVisitor.VisitMember(MemberExpression node)
   at System.Linq.Expressions.MemberExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Linq.Expressions.ExpressionVisitor.Visit(ReadOnlyCollection`1 nodes)
   at System.Linq.Expressions.Compiler.VariableBinder.VisitLambda[T](Expression`1 node)
   at System.Linq.Expressions.Expression`1.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Linq.Expressions.ExpressionVisitor.Visit(ReadOnlyCollection`1 nodes)
   at System.Linq.Expressions.Compiler.VariableBinder.VisitLambda[T](Expression`1 node)
   at System.Linq.Expressions.Expression`1.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.Compiler.VariableBinder.Visit(Expression node)
   at System.Linq.Expressions.Compiler.LambdaCompiler.Compile(LambdaExpression lambda)
   at System.Linq.Expressions.Expression`1.Compile(Boolean preferInterpretation)
   at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.CreateExecutorLambda[TResults]()
   at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.CreateQueryExecutor[TResult](QueryModel queryModel)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](Expression query, IQueryModelGenerator queryModelGenerator, IDatabase database, IDiagnosticsLogger`1 logger, Type contextType)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass13_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Remotion.Linq.QueryableBase`1.GetEnumerator()
   at System.Collections.Generic.List`1.AddEnumerable(IEnumerable`1 enumerable)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at EF21Regression.Program.Main(String[] args) in c:\EF21Regression\EF21Regression\Program.cs:line 21

Steps to reproduce

This example .NET Core console app project has a single package reference to Microsoft.EntityFrameworkCore.Sqlite. I encounter the problem with version 2.1.0-preview2-final, but not with 2.0.2.

using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;

namespace EF21Regression
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var db = new RegressionDbContext())
            {
                db.Database.EnsureDeleted();
                db.Database.EnsureCreated();

                DateTime tenDaysAgo = DateTime.Today.AddDays(-10);

                List<IR> result = db.Cs
                    .Include(c => c.B)
                    .ThenInclude(b => b.A)
                    .Where(joinedData => joinedData.P == 0
                        && joinedData.B.AKey == joinedData.B.A.AKey
                        && joinedData.B.DT > tenDaysAgo)
                    .GroupBy(firstGroup => new
                    {
                        firstGroup.B.A.Name,
                        R = firstGroup.R,
                        D = firstGroup.B.DT,
                    })
                    .GroupBy(secondGroup => secondGroup.Key.Name)
                    .Select(firstSelect => new
                    {
                        Name = firstSelect.Key,
                        Latest = firstSelect.OrderByDescending(z => z.Key.D).First().Key
                    })
                    .Select(secondSelect => new IR
                    {
                        Name = secondSelect.Name,
                        ID = secondSelect.Latest.R * 100,
                        D = secondSelect.Latest.D,
                    })
                    .ToList();
            }
        }
    }


    public class RegressionDbContext : DbContext
    {
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<DbA>().ToTable("dbA");
            modelBuilder.Entity<DbB>().ToTable("dbB");
            modelBuilder.Entity<DbC>().ToTable("dbC");

            modelBuilder.Entity<DbA>()
                .HasIndex(p => p.Name)
                .HasName("IX_Name")
                .IsUnique();
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlite("Data Source=regression.db");
        }

        public DbSet<DbA> As { get; set; }
        public DbSet<DbB> Bs { get; set; }
        public DbSet<DbC> Cs { get; set; }
    }

    public class DbC
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public long CKey { get; set; }

        [ForeignKey(nameof(BKey))]
        public DbB B { get; set; }
        public long BKey { get; set; }

        public byte P { get; set; }
        public decimal R { get; set; }
    }

    public class DbB
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public long BKey { get; set; }
        public DateTime DT { get; set; }

        [ForeignKey(nameof(AKey))]
        public DbA A { get; set; }
        public int AKey { get; set; }

        public virtual ICollection<DbC> Cs { get; set; }
    }

    public class DbA
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int AKey { get; set; }

        [MaxLength(20)]
        public string Name { get; set; }
    }

    public class IR
    {
        public string Name { get; set; }
        public decimal ID { get; set; }
        public DateTime D { get; set; }
    }

}

Further technical details

EF Core version: 2.1.0-preview2-final
Database Provider: Microsoft.EntityFrameworkCore.Sqlite in the regression code example provided above but seen in Microsoft.EntityFrameworkCore.SqlServer in the real project
Operating system: Windows 10 (Version 1709)
IDE: Visual Studio 2017 15.7 Preview 5

[smitpatel]

Passing over to @maumar since he is working on a fix.

[maumar]

fixed in af08612

[JesperTreetop]

Impressively expedient. Will this make it in in time for the rc?

[ajcvickers]

@JesperTreetop RC1 has already locked down. This fix will be included in the RTM release.