NullReferenceException when translating nested SelectMany with Constructor calls

[JakenVeina]

I'm getting a reproducible NullReferenceException when translating the following query...

var results3 = await context.Set<MyParentVersionEntity>()
    .Where(pv => pv.NextVersionId == null)
    .Select(pv => new MyParentDetailViewModel(
        pv.ParentId,
        pv.Name,
        pv.Parent.Children
            .SelectMany(c => c.Versions
                .Where(cv => cv.NextVersionId == null)
                .Where(cv => !cv.IsDeleted)
                .Select(cv => new MyChildIdentityViewModel(
                    cv.ChildId,
                    cv.Name)))
            .ToArray()))
    .ToArrayAsync();

The query runs correctly with either of the following tweaks:

Un-nesting the subquery within .SelectMany()

var results2 = await context.Set<MyParentVersionEntity>()
    .Where(pv => pv.NextVersionId == null)
    .Select(pv => new MyParentDetailViewModel(
        pv.ParentId,
        pv.Name,
        pv.Parent.Children
            .SelectMany(c => c.Versions)
            .Where(cv => cv.NextVersionId == null)
            .Where(cv => !cv.IsDeleted)
            .Select(cv => new MyChildIdentityViewModel(
                cv.ChildId,
                cv.Name))
            .ToArray()))
    .ToArrayAsync();

Replacing the constructor calls with anonymous objects

var results1 = await context.Set<MyParentVersionEntity>()
    .Where(pv => pv.NextVersionId == null)
    .Select(pv => new
    {
        pv.ParentId,
        pv.Name,
        Children = pv.Parent.Children
            .SelectMany(c => c.Versions
                .Where(cv => cv.NextVersionId == null)
                .Where(cv => !cv.IsDeleted)
                .Select(cv => new
                {
                    cv.ChildId,
                    cv.Name
                }))
            .ToArray()
    })
    .ToArrayAsync();

Full reproduction test case: https://github.com/JakenVeina/EFCoreSelectManyTest.

Stack Trace:

   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.MemberAccessShiftingExpressionVisitor.VisitExtension(Expression node)
   at System.Linq.Expressions.Expression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
   at System.Linq.Expressions.ExpressionVisitor.VisitNew(NewExpression node)
   at System.Linq.Expressions.NewExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.CombineShapers(Expression queryExpression, Expression outerShaper, Expression innerShaper, Type transparentIdentifierType)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.TranslateResultSelectorForJoin(ShapedQueryExpression outer, LambdaExpression resultSelector, Expression innerShaper, Type transparentIdentifierType)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.TranslateSelectMany(ShapedQueryExpression source, LambdaExpression collectionSelector, LambdaExpression resultSelector)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.TranslateSubquery(Expression expression)
   at Microsoft.EntityFrameworkCore.Query.RelationalSqlTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Query.Internal.NpgsqlSqlTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCall)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.RelationalSqlTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Query.Internal.NpgsqlSqlTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCall)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.RelationalSqlTranslatingExpressionVisitor.Translate(Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.Visit(Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.VisitNew(NewExpression newExpression)
   at System.Linq.Expressions.NewExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.Visit(Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.RelationalProjectionBindingExpressionVisitor.Translate(SelectExpression selectExpression, Expression expression)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.TranslateSelect(ShapedQueryExpression source, LambdaExpression selector)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   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__DisplayClass12_0`1.<ExecuteAsync>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetAsyncEnumerator(CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.ConfiguredCancelableAsyncEnumerable`1.GetAsyncEnumerator()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.<ToListAsync>d__64`1.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.<ToArrayAsync>d__65`1.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at EFCoreSelectManyTest.Program.<Main>d__0.MoveNext() in D:\Projects\EFCoreSelectManyTest\Program.cs:line 61

EF Core version: 3.1.0
Database provider: Npgsql.EntityFrameworkCore.PostgreSQL
Target framework: .NET Core 3.0
Operating system: Windows 8.1 Pro
IDE: Visual Studio Community 2019 16.4.0

[ghost]

It's still an issue in EF Core 3.1.2 for SQL Server.

[smitpatel]

This happens when TranslateResultSelectorForJoin runs through a client eval projection.

[smitpatel]

Poaching. Need this for #20892