c# 9.0 records and nullability

Question

I'm trying out the new record features using latest .Net5

  public record Rec {
    public string Name;
    public int Id;
    //public Rec(string name, int id) => (Name, Id) = (name, id);
  }

I get

warning CS8618: Non-nullable field 'Name' is uninitialized. Consider declaring the field as nullable.

So a constructor is not generated whereas I understood that is a feature of records ?
and why not the same warning for Id ?
If I unremark the ctor above the warning goes away (which makes sense)

Also if I do instead:

public record Rec(string Name, int Id);

There are no warnings.

EDIT

so it seems the two forms of creating a record (longer vs shorter syntax) are different, the short version makes the fields public and also adds a ctor whereas the first one does not. I can't find a reference to that.

Answer 1

So a constructor is not generated whereas I understood that is a feature of records ?

According to the documentation: A Primary Constructor is synthesized for all Value Parameters of the Parameter List for the Positional Record.

Your first example doesn't have a Parameter List and thus doesn't have Value Parameters, therefore it is not a Positional Record, and therefore it doesn't have a Primary Constructor.

and why not the same warning for Id ?

Because the default constructor for int is, and always has been, 0, not null. This isn't really specific to records, this has always been the case, since before C# 1.0.