[Bug c++/84993] New: Combination of fieldnames and accessor suggestions for misspelled private fields

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84993

            Bug ID: 84993
           Summary: Combination of fieldnames and accessor suggestions for
                    misspelled private fields
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: dmalcolm at gcc dot gnu.org
  Target Milestone: ---

Consider:

class foo
{
public:
  double get_ratio() const { return m_ratio; }

private:
  double m_ratio;
};

void test(foo *ptr)
{
  if (ptr->ratio >= 0.5)
    ;// etc
}

Currently we emit this suggestion:

<source>: In function 'void test(foo*)':
<source>:12:12: error: 'class foo' has no member named 'ratio'; did you mean
'm_ratio'?
   if (ptr->ratio >= 0.5)
            ^~~~~
            m_ratio

...but if the user follows this suggestion, they get:

<source>: In function 'void test(foo*)':
<source>:12:12: error: 'double foo::m_ratio' is private within this context
   if (ptr->m_ratio >= 0.5)
            ^~~~~~~
<source>:7:10: note: declared private here
   double m_ratio;
          ^~~~~~~
<source>:12:12: note: field 'double foo::m_ratio' can be accessed via 'double
foo::get_ratio() const'
   if (ptr->m_ratio >= 0.5)
            ^~~~~~~
            get_ratio()

It feels wrong to be emitting a fix-it hint that doesn't compile; we ought to
offer the accessor directly; something like:

<source>: In function 'void test(foo*)':
<source>:12:12: error: 'class foo' has no member named 'ratio'; did you mean
'private' field 'double foo::m_ratio', accessed by 'double foo::get_ratio()
const'?
   if (ptr->ratio >= 0.5)
            ^~~~~
            get_ratio ()

or somesuch.