`DbSet.Count()` in `Select()` lambda not translating to scalar subquery expression

It appears a DbSet.Count() expression is getting evaluated ahead of time and parameterized.

Example:
```csharp
var query = dbContext.MyDbSet.Select(v => new
{
v.Id,
Count = dbContext.MyDbSet.Count()
});
string sql = query.ToQueryString();
```

Expected:

```sql
SELECT [v].[Id], (select COUNT(1) from [MyTable]) AS [Count]
FROM [MyTable] AS [v]
```

Actual:

```sql
DECLARE @__Count_0 int = 20;

SELECT [v].[Id], @__Count_0 AS [Count]
FROM [MyTable] AS [v]
```

Maybe this is by design for some reason I'm not understanding. Thank you