BUG? Created migration throw exception and cannot be reversed (only delete)

[Bartmax]

Steps to reproduce

Using this model:

public class ImageFile 
{
    public Guid ImageFileId { get; private set; }

    [Required]
    public string Filename { get; private set; }

    public string OriginalFilename { get; private set; }

    public string ContentType { get; private set; }

    public string Folder { get; set; }
}

public class Company
{
    public int CompanyId { get; set; }
    public ImageFile Watermark { get; set; }
    public ImageFile Logo { get; set; }
    public ICollection<Screenshot> Screenshots { get; set; }
    public ICollection<Photos> Photos { get; set; }
}

public abstract class ImageOrder
{
    public int ImageOrderId { get; set; }
    public int Order { get; set; }
    public ImageFile ImageFile { get; set; }
}

public class Photos : ImageOrder
{
    public string Caption { get; set; }
}

public class Screenshot : ImageOrder
{
    public string Other { get; set; }
}

### The issue 1. Migration code generated has duplicate data. 2. `ef database update` throws `Sequence contains more than one matching element` 3. `ef migrations remove` gives no error but migration is **not removed**

Migration code

public partial class initial : Migration
    {
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.CreateTable(
                name: "ImageFile",
                columns: table => new
                {
                    ImageFileId = table.Column<Guid>(nullable: false),
                    ContentType = table.Column<string>(nullable: true),
                    Filename = table.Column<string>(nullable: false),
                    Folder = table.Column<string>(nullable: true),
                    OriginalFilename = table.Column<string>(nullable: true)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_ImageFile", x => x.ImageFileId);
                });

            migrationBuilder.CreateTable(
                name: "Companies",
                columns: table => new
                {
                    CompanyId = table.Column<int>(nullable: false)
                        .Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn),
                    LogoImageFileId = table.Column<Guid>(nullable: true),
                    WatermarkImageFileId = table.Column<Guid>(nullable: true)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Companies", x => x.CompanyId);
                    table.ForeignKey(
                        name: "FK_Companies_ImageFile_LogoImageFileId",
                        column: x => x.LogoImageFileId,
                        principalTable: "ImageFile",
                        principalColumn: "ImageFileId",
                        onDelete: ReferentialAction.Restrict);
                    table.ForeignKey(
                        name: "FK_Companies_ImageFile_WatermarkImageFileId",
                        column: x => x.WatermarkImageFileId,
                        principalTable: "ImageFile",
                        principalColumn: "ImageFileId",
                        onDelete: ReferentialAction.Restrict);
                });

            migrationBuilder.CreateTable(
                name: "ImageOrder",
                columns: table => new
                {
                    ImageOrderId = table.Column<int>(nullable: false)
                        .Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn),
                    Discriminator = table.Column<string>(nullable: false),
                    ImageFileId = table.Column<Guid>(nullable: true),
                    Order = table.Column<int>(nullable: false),
                    Caption = table.Column<string>(nullable: true),
                    CompanyId = table.Column<int>(nullable: true)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_ImageOrder", x => x.ImageOrderId);
                    table.ForeignKey(
                        name: "FK_ImageOrder_ImageFile_ImageFileId",
                        column: x => x.ImageFileId,
                        principalTable: "ImageFile",
                        principalColumn: "ImageFileId",
                        onDelete: ReferentialAction.Restrict);
                    table.ForeignKey(
                        name: "FK_ImageOrder_Companies_CompanyId",
                        column: x => x.CompanyId,
                        principalTable: "Companies",
                        principalColumn: "CompanyId",
                        onDelete: ReferentialAction.Restrict);
                    table.ForeignKey(
                        name: "FK_ImageOrder_Companies_CompanyId",
                        column: x => x.CompanyId,
                        principalTable: "Companies",
                        principalColumn: "CompanyId",
                        onDelete: ReferentialAction.Restrict);
                });

            migrationBuilder.CreateIndex(
                name: "IX_Companies_LogoImageFileId",
                table: "Companies",
                column: "LogoImageFileId");

            migrationBuilder.CreateIndex(
                name: "IX_Companies_WatermarkImageFileId",
                table: "Companies",
                column: "WatermarkImageFileId");

            migrationBuilder.CreateIndex(
                name: "IX_ImageOrder_ImageFileId",
                table: "ImageOrder",
                column: "ImageFileId");

            migrationBuilder.CreateIndex(
                name: "IX_ImageOrder_CompanyId",
                table: "ImageOrder",
                column: "CompanyId");
        }

        protected override void Down(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.DropTable(
                name: "ImageOrder");

            migrationBuilder.DropTable(
                name: "Companies");

            migrationBuilder.DropTable(
                name: "ImageFile");
        }
    }

Stack trace

System.InvalidOperationException: Sequence contains more than one matching element
   at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.GetColumnType(String schema, String table, String name, Type clrType, Nullable`1 unicode, Nullable`1 maxLength, Boolean rowVersion, IModel model)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.ColumnDefinition(String schema, String table, String name, Type clrType, String type, Nullable`1 unicode, Nullable`1 maxLength, Boolean rowVersion, Boolean nullable, Object defaultValue, String defaultValueSql, String computedColumnSql, IAnnotatable annotatable, IModel model, MigrationCommandListBuilder builder)
   at Microsoft.EntityFrameworkCore.Migrations.SqlServerMigrationsSqlGenerator.ColumnDefinition(String schema, String table, String name, Type clrType, String type, Nullable`1 unicode, Nullable`1 maxLength, Boolean rowVersion, Boolean nullable, Object defaultValue, String defaultValueSql, String computedColumnSql, Boolean identity, IAnnotatable annotatable, IModel model, MigrationCommandListBuilder builder)
   at Microsoft.EntityFrameworkCore.Migrations.SqlServerMigrationsSqlGenerator.ColumnDefinition(String schema, String table, String name, Type clrType, String type, Nullable`1 unicode, Nullable`1 maxLength, Boolean rowVersion, Boolean nullable, Object defaultValue, String defaultValueSql, String computedColumnSql, IAnnotatable annotatable, IModel model, MigrationCommandListBuilder builder)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.ColumnDefinition(AddColumnOperation operation, IModel model, MigrationCommandListBuilder builder)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.Generate(CreateTableOperation operation, IModel model, MigrationCommandListBuilder builder)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.Generate(MigrationOperation operation, IModel model, MigrationCommandListBuilder builder)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.Generate(IReadOnlyList`1 operations, IModel model)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.GenerateUpSql(Migration migration)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.Design.MigrationsOperations.UpdateDatabase(String targetMigration, String contextType)
   at Microsoft.EntityFrameworkCore.Tools.Cli.DatabaseUpdateCommand.<>c__DisplayClass0_0.<Configure>b__0()
   at Microsoft.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[] args)
   at Microsoft.EntityFrameworkCore.Tools.Cli.Program.Main(String[] args)

### Further technical details

EF Core version: 1.0.0
Operating system: Windows
Visual Studio version: VS 2015 Enterprise

Other details about my project setup:

I cannot find a way to create the following (3 tables) schema using code first.
I tried everything, it just looks impossible.

Images:
ImageId - FileName

Company:
CompanyId - Name - Logo_ImageId - Watermark_ImageId

CompanyImages:
CompanyId - Discriminator - ImageId - Order

[bricelam]

Fixed by @AndriySvyryd in #6143