Incorrect SQL translation for negated nullable boolean equality

[ixtreon]

Description

According to C# null semantics, given a bool? A, the expressions !(A == true) and A != true should be equivalent. When used in a filter, both expressions should translate to SQL that includes rows where A is null. Previous versions of EF correctly reflected this behaviour. However, in v9, !(A == true) is incorrectly translated to SQL that excludes rows where A is null, while A != true is translated correctly.

This seems to apply to both the SQL Server and Sqlite providers.

Steps to reproduce

using Microsoft.EntityFrameworkCore;

var db = new MyContext();
var notBlocked = db.Set<User>().Where(x => !(x.IsBlocked == true)).ToQueryString();
var notBlocked2 = db.Set<User>().Where(x => x.IsBlocked != true).ToQueryString();

Console.WriteLine($"""
    Query 1:
    {notBlocked}

    Query 2:
    {notBlocked2}
    """);

class MyContext : DbContext
{
    public DbSet<User> Users { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) 
        => optionsBuilder.UseSqlite();
}

class User
{
    public int Id { get; set; }
    public bool? IsBlocked { get; set; }
}

Expected Output

Using version 8.0.12 of EF and the Sqlite provider:

Query 1:
SELECT "u"."Id", "u"."IsBlocked"
FROM "Users" AS "u"
WHERE "u"."IsBlocked" = 0 OR "u"."IsBlocked" IS NULL

Query 2:
SELECT "u"."Id", "u"."IsBlocked"
FROM "Users" AS "u"
WHERE "u"."IsBlocked" <> 1 OR "u"."IsBlocked" IS NULL

Version 7.0.20 produces virtually the same output, only wrapping the IS NULL comparison in parentheses.

Actual Output

Using version 9.0.1 of EF and the Sqlite provider:

Query 1:
SELECT "u"."Id", "u"."IsBlocked"
FROM "Users" AS "u"
WHERE "u"."IsBlocked" = 0

Query 2:
SELECT "u"."Id", "u"."IsBlocked"
FROM "Users" AS "u"
WHERE "u"."IsBlocked" = 0 OR "u"."IsBlocked" IS NULL

Environment

EF Core version: 9.0.1
Database provider: Microsoft.EntityFrameworkCore.SqlServer, Microsoft.EntityFrameworkCore.Sqlite
Target framework: .NET 9.0
Operating system: Windows 11
IDE: Visual Studio 2022 17.12.3

[maumar]

This is a duplicate of #35393, which will be fixed in 9.0.3