Re: [PATCH] C++: fix-it hints suggesting accessors for private fields

[Nathan Sidwell <nathan@acm.org>]

On 04/26/2017 12:34 PM, David Malcolm wrote:

> Thanks - yes; that gives information on the const vs non-const of the
> "this" parameter, but doesn't say whether the argument was const vs non
> -const.

> However, within:
> 
> int test_const_ptr (const t1 *ptr)
> {
>    return ptr->m_color;
> }
> from which we can see the const-ness of the t1:

correct.

> but the call to lookup_member from within
> finish_class_member_access_expr discards this information, giving just
> "access_path": a BINFO that wraps the RECORD_TYPE for t1 directly.

Correct.

lookup_member just looks for a matching name.  the BINFO represents the 
class hierarchy - it's not modified depending on the cvquals of where 
you came from.

> A somewhat invasive solution would be for lookup_member to grow an extra:
>    tree object
> parameter, and to pass this information down through the access
> -enforcement code, so that locate_field_accessor can look at the const
> -ness of the lookup, and avoid suggesting const methods when the object
> is const.  The code would probably need to support the new param being
> NULL_TREE for cases where we're looking up a static member.  Or maybe
> an enum of access style for const vs non-const vs static.
> Maybe name the param "access_hint" to signify that it's merely there
> for the purpose of hints for the user, and not to affect the parsing
> itself?

Hm, that does seem rather unfortunate.
> Another solution would be to not bother offering non-const methods as
> accessors.

I think that would be very unfortunate.

How about adding a tsubst_flag value?

   tf_const_obj = 1 << 11, /* For alternative accessor suggestion help.  */

and pass that in?  the tsubst flags have grown in meaning somewhat since 
they first appeared -- their name is no longer so appropriate.

(of course we have the same problem with volatile, but that's probably 
overkill for first attempt.)

Jason, WDYT?

nathan

-- 
Nathan Sidwell