Calling super() from sub-sub-class leads to infinite loop

[espruino-discuss]

Posted at 2020-07-27 by coajaxial

Example:

class A {
  constructor() {
  }
}
class B extends A {
  constructor() {
    super();
  }
}
class C extends B {
  constructor() {
    super();
  }
}
new C();

Result:

Uncaught Error: Too much recursion - the stack is about to overflow
 at line 7 col 1
super();
^
in function called from line 7 col 7
super();
      ^
[.......]
in function called from line 7 col 7
super();
      ^
Execution Interrupted

[espruino-discuss]

Posted at 2020-07-27 by user115787

@op, this probably won't help you directly.

I have done some reading about super lately. Here's a summary:

• functions created with funcName() syntax (as in class { }) have a hidden attribute pointing to their "HomeObject" - C.prototype and B.prototype in the example here.
  • also true in an object-literal like { foo() { } }, as a pedantic side note
• super is (should be) Object.prototypeOf(HomeObject)
• in constructor, super() is shorthand for super.constructor()

It looks like the call to super at line 7 may be resolving super as Object.prototypeOf(this) instead.

https://2ality.com/2011/11/super-references.html

HTH someone

[gfwilliams]

Posted at 2020-07-28 by @gfwilliams

Hi - I'm afraid I think you've just hit this bug in Espruino:

Classes cannot extend classes that extend classes #1529

espruino/Espruino#1529

Until it gets fixed there's a workaround mentioned there though