Missing nullability warning for an explicit conversion to a type parameter

[AlekseyTs]

        [Fact]
        public void Test()
        {
            var source = @"
class Outer
{
    void M1<T>(T x1, object? y1) where T : class?
    {
        x1 = (T)y1;
    }

    void M2<T>(T x2, object? y2) where T : class?
    {
        x2 = y2;
    }

    void M3(string x3, object? y3)
    {
        x3 = (string)y3;
    }

    void M4(string x4, object? y4)
    {
        x4 = y4;
    }
}
";

            CreateCompilation(source, options: WithNonNullTypesTrue()).VerifyDiagnostics(
                // (11,14): error CS0266: Cannot implicitly convert type 'object' to 'T'. An explicit conversion exists (are you missing a cast?)
                //         x2 = y2;
                Diagnostic(ErrorCode.ERR_NoImplicitConvCast, "y2").WithArguments("object", "T").WithLocation(11, 14),
                // (11,14): warning CS8619: Nullability of reference types in value of type 'object' doesn't match target type 'T'.
                //         x2 = y2;
                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "y2").WithArguments("object", "T").WithLocation(11, 14),
                // (16,14): warning CS8600: Converting null literal or possible null value to non-nullable type.
                //         x3 = (string)y3;
                Diagnostic(ErrorCode.WRN_ConvertingNullableToNonNullable, "(string)y3").WithLocation(16, 14),
                // (16,14): warning CS8600: Converting null literal or possible null value to non-nullable type.
                //         x3 = (string)y3;
                Diagnostic(ErrorCode.WRN_ConvertingNullableToNonNullable, "(string)y3").WithLocation(16, 14),
                // (21,14): error CS0266: Cannot implicitly convert type 'object' to 'string'. An explicit conversion exists (are you missing a cast?)
                //         x4 = y4;
                Diagnostic(ErrorCode.ERR_NoImplicitConvCast, "y4").WithArguments("object", "string").WithLocation(21, 14),
                // (21,14): warning CS8600: Converting null literal or possible null value to non-nullable type.
                //         x4 = y4;
                Diagnostic(ErrorCode.WRN_ConvertingNullableToNonNullable, "y4").WithLocation(21, 14),
                // (21,14): warning CS8619: Nullability of reference types in value of type 'object' doesn't match target type 'string'.
                //         x4 = y4;
                Diagnostic(ErrorCode.WRN_NullabilityMismatchInAssignment, "y4").WithArguments("object", "string").WithLocation(21, 14)
                );
        }

Observed:
No warnings for x1 = (T)y1;.

Expected :
A warning because T could be a not nullable reference type and y1 is object?.

[jcouv]

I think this was fixed by #32850
I'll add a test to verify