Unable to translate set operation when matching columns on both sides have different store types

Include your code

using System;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

namespace HelloEFCore
{
    public class Program
    {
        public static async Task Main(string[] args)
        {
            var testContext = new TestContext();

            var test1 = testContext.Test1.Select(a => new Test
            {
                Id = a.Id,
                Name = "Test1"
            });

            var test2 = testContext.Test2.Select(a => new Test
            {
                Id = a.Id,
                Name = a.Name
            });

            var test = test1.Union(test2).ToList();
            foreach (var item in test)
            {
                Console.WriteLine($"{item.Id}\t{item.Name}");
            }
        }
    }

    public partial class TestContext : DbContext
    {
        public TestContext()
        {
        }

        public TestContext(DbContextOptions<TestContext> options)
            : base(options)
        {
        }

        public virtual DbSet<Test1> Test1 { get; set; }
        
        public virtual DbSet<Test2> Test2 { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
                optionsBuilder.UseSqlServer("");
            }
        }
    }

    public class Test
    {
        public Guid Id { get; set; }

        public string Name { get; set; }
    }

    public class Test1
    {
        [Key]
        public Guid Id { get; set; }

        [Required]
        [StringLength(50)]
        public string Name { get; set; }
    }

    public class Test2
    {
        [Key]
        public Guid Id { get; set; }

        [Required]
        [StringLength(50)]
        public string Name { get; set; }
    }
}

Include stack traces

Unhandled exception. System.InvalidOperationException: Unable to translate set operation when matching columns on both sides have different store types.
   at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.ApplySetOperation(SetOperationType setOperationType, SelectExpression select2, Boolean distinct)
   at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.ApplyUnion(SelectExpression source2, Boolean distinct)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryableMethodTranslatingExpressionVisitor.TranslateUnion(ShapedQueryExpression source1, ShapedQueryExpression source2)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.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__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 HelloEFCore.Program.Main(String[] args) in E:\Projects\HelloEFCore\HelloEFCore\Program.cs:line 27
   at HelloEFCore.Program.<Main>(String[] args)

Include provider and version information

EF Core version:5.0.5 Database provider: Microsoft.EntityFrameworkCore.SqlServer Target framework: .NET 5.0 Operating system:win 10 IDE: Visual Studio 2019 16.9

[roji]

It may be correct in this case to infer the constant mapping from the column on the other side of the set operation, like how we do with binary operators. But this can be done as part of #19129 when the time comes…

[smitpatel]

like how we do with binary operators.

Those are orthogonal concepts and it is responsibility of set operations to align the types across column, which is what #19129 tracks specifically.