testlib: Don't print QCOMPARE values if they lack string representation

Before 0681a2dd5a8095baddb5905fb21a58ce19b958c5, QCOMPARE'ing types
for which no QTest::toString specialization exists did not output
Actual and Expected lines on failure, as that would only print <null>
for both values (which then look like the same value, confusingly).

Commit 0681a2dd5a8095baddb5905fb21a58ce19b958c5 changed that behavior,
and started printing the confusing <null> values.

Take care of the logic in the formatFailMessage function: if both values
are nullptr, then print only the variable names, but not the confusing
<null> text representation of the values.

Remove dead and duplicated code related to the formatting logic, add a
self-test function, and update the expected_cmptest files.

Fixes: QTBUG-104867
Pick-to: 6.4
Change-Id: I4be98e79f91196b14690a2cc0a68ffd50b431a45
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions