related to compile error in preview feature 'record'

[Alex Buckley]

In the compact constructor below, `low` refers to an implicit parameter 
of the constructor, whereas `this.low` refers to a field corresponding 
to the record component `low`.

IIRC, the field is not definitely assigned before the end of the 
constructor body, so referring to `this.low` anywhere in the constructor 
body is an error by the traditional rule at the beginning of JLS ch.16.

There is no interprocedural analysis in ch.16, so m1's independent 
reference to a field via `this.low` is allowed on the basis that the 
field was definitely assigned by the end of every constructor body.'

In an ordinary class, a constructor body that calls m1() but forgets to 
explicitly initialize the field would cause a compile-time error. There 
is no corresponding compile-time error here because the compact 
constructor body implicitly initializes the field.

Alex

On 9/30/2020 8:45 AM, Pravin Jain wrote:
> Dear sir,
> In the following code, I have commented the error.
> This error seems to be unnecessary, could have been a warning instead.
> In the constructor of record access to instance variable before
> explicit initialization, giving error, whereas same access is
> available by invoking a method.
> 
> public record TestRecord(int low, int high) {
>      public TestRecord {
>          System.out.println(low);
> //        System.out.println(this.low); // error, variable not initialized
>          m1(); // but this works, why?
>      }
>      public void m1() {
>          System.out.println(this.low);
>      }
>      public static void main(String[] args) {
>          TestRecord r1 = new TestRecord(7,12);
>      }
> }
> 
>