Make RootObject equals and toChars const

[edi33416]

This PR is useful to the the C++ header generator to generate the dmd frontend header files that are used by gdc.

The issue that I'm attempting to solve: D has function covariance, but C++ does not. What this means is that if I have the following D code

extern (C++) class A
{
  void foo() {}
}

extern (C++) class B :  A
{
  override void foo() const {}
}

the generated header will look like

class A
{
  virtual void foo();
}

class B : public A
{
  void foo() const;
}

Note that B has void foo() const
Compiling this code with g++ -Woverloaded-virtual (as gdc does) will result in the following warning

warning: 'virtual void A::foo()' was hidden

by `void B::foo() const`

[dlang-bot]

Thanks for your pull request and interest in making D better, @edi33416! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
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• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
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• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

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Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + dmd#10293"

[edi33416]

@andralex

[ibuclaw]

Not all sources look to be updated, headers should be updated as well too if they haven't been.

[edi33416]

Nothing all sources look to be updated,

I'm sorry, but what do you mean by this?

headers should be updated as well too if they haven't been.

I haven't updated the headers as they have dropped the const from the function declaration in order to work. Adding the const won't change the name mangling so I left the headers unchanged, in the "hope" of getting the auto-generated header in soon. I've managed to build gdc's decl.cc with the auto-generated header, so I really hope we'll get there soon.

[ibuclaw]

I'm sorry, but what do you mean by this?

I think I meant not, but autocomplete got in the way. There were some D related errors at last look.

[rainers]

See comments

[rainers]

Adding the const won't change the name mangling

It does on Windows and I would be surprised if it doesn't elsewhere (e.g. for overloads), but it is usually irrelevant for virtual function calls if the vtbl is generated on the D side.

[edi33416]

@rainers do you know why the tests are failing? I didn't manage to find the struct S that's causing problems with toString. I guess that struct needs to override with a toString() const.

[Geod24]

@edi33416 :

dmd/src/dmd/root/array.d

Line 252 in 4abeae0

string toString()

[edi33416]

@edi33416 :

dmd/src/dmd/root/array.d

Line 252 in 4abeae0

string toString()

I hadn't rebase with master..

[rainers]

LGTM. Please squash commits. (Or do we use "squash and merge"? I suspect it will just concatenate commit messages that don't look to nice).

[thewilsonator]

I'll just do the squashing manually.

[Geod24]

@rainers : FYI, Using squash and merge on Github allows you to edit the message. But the bot just squash them, yes.

[edi33416]

LGTM. Please squash commits. (Or do we use "squash and merge"? I suspect it will just concatenate commit messages that don't look to nice).

I thought the squash and merge will keep only the first commit message. That's why I didn't do it myself and why I just named the future commits "qf".. Will pay more attention in the future. Thanks @thewilsonator for doing it for me