[Oberon] Type compatibility rules for Pointers

[August Karlstrom]

On 2020-06-15 21:09, chris wrote:
> TYPE
> 	R = RECORD i : INTEGER END;
> 	P1 = POINTER TO R;
> 	P2 = POINTER TO R;
> 
> PROCEDURE Test();
> VAR
> 	p1 : P1; p2 : P2;
> BEGIN
> 	NEW(p1); NEW(p2);
> 	IF p1 IS P2 THEN (* true *) END;
> 	p1 := p2;
> END Test;
[...]
> I am a bit confused that p1 := p2 compiles without errors.
Section 6.4 in the language report says that "Pointer types inherit the 
extension relation of their base types, if there is any." Also P2 is a 
(trivial) extension of P1 and vice versa.

August