Constness behavior of Handle<Object> vs. Object

[Jakob Gruber]

Hi team,

I came across this yesterday and found the behavior surprising, thus this quick fyi email.

`Handle<Object>` and `Object` class members have different behavior wrt to const. The former behaves like a plain old C++ pointer (`ClassXYZ*`) while the latter behaves like an instance (`ClassXYZ`). This is a bit strange, since conceptually both `Handle<Object>` and `Object` otherwise behave like pointers underneath (e.g. `Object x; x = y;` is a reference copy, not a value-copy).

Examples:

class C {

 void foo() const { x_.nonconst_function(); }  // compile-time error.

 ClassXYZ x_;

}

   

class C' {

 void foo() const { x_->nonconst_function(); }  // okay.

 ClassXYZ* x_;

}

class C'' {

 void foo() const { x_.nonconst_function(); }  // compile-time error.

 Object x_;

}

   

class C''' {

 void foo() const { x_->nonconst_function(); }  // okay.

 Handle<Object> x_;

}

While not terribly important, equal behavior between Object and Handle<Object> would be more consistent.

[Leszek Swirski]

I would imagine this would be solvable by providing different overloads for const and non-const operator-> (and operator*) in Handle.

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[Jakob Gruber]

On Wed, Apr 14, 2021 at 1:08 PM Leszek Swirski <les...@chromium.org> wrote:

I would imagine this would be solvable by providing different overloads for const and non-const operator-> (and operator*) in Handle.

That'd make both C'' and C''' behave like C (value member), but given their similarity to pointers it may make sense to have them behave like C' (pointer member).

 

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