Repro issue https://github.com/aspnet/EntityFramework/issues/7863

.cs

using System.Collections.Generic;
using System.Linq;
using Microsoft.Data.Sqlite;
using Microsoft.EntityFrameworkCore;

namespace Repro
{
    public class Program
    {
        public static void Main()
        {
            var db = GetContext();
            var inmemcheck = new InMemoryCheck();
            var variableName = "test";
            var differentVariableName = "test";

            // True (or any other expression translatable to SQL) seems required to get it into the ShaperCommandContext
            DbContext.Set<Entity>().Where(e => e.Id == 4).Where(e2 => inmemcheck.Check(variableName, e2.Id.ToString()) || true).Count();
            DbContext.Set<Entity>().Where(e => e.Id == 4).Where(e2 => inmemcheck.Check(differentVariableName, e2.Id.ToString()) || true).Count();

            // No exception if var (variableName) is the same
            // DbContext.Set<Entity>().Where(e => e.Id == 4).Where(e2 => inmemcheck.Check(variableName, e2.Id.ToString()) || true).Count();
            // DbContext.Set<Entity>().Where(e => e.Id == 4).Where(e2 => inmemcheck.Check(variableName, e2.Id.ToString()) || true).Count();
        }

        private static DbContext DbContext { get; } = GetContext();
        private static DbContext GetContext()
        {
            var connection = new SqliteConnection("DataSource=:memory:");
            connection.Open();

            var db = new DbContext(new DbContextOptionsBuilder<DbContext>().UseSqlite(connection).Options);
            db.Database.EnsureCreated();
            db.Entities.AddRange(new List<Entity> { new Entity { Id = 1 }, new Entity { Id = 3 } });
            db.SaveChanges();

            return db;
        }
    }

    public class Entity
    {
        public int Id { get; set; }
    }

    public class DbContext : Microsoft.EntityFrameworkCore.DbContext
    {
        public DbSet<Entity> Entities { get; set; }
        public DbContext(DbContextOptions<DbContext> options) : base(options) { }
    }

    public class InMemoryCheck
    {
        private Dictionary<string, string> _data = new Dictionary<string, string>();
        public bool Check(string input1, string input2)
            => _data.ContainsKey(input1) && _data[input1] == input2;
    }
}