Add ImplPtr and makeImpl

The original (more complex and comprehensive) solution belongs to
https://oliora.github.io/2015/12/29/pimpl-and-rule-of-zero.html - this
commit only provides a small wrapper for non-copyable Private class
implementations common throughout libQuotient. Unlike the original,
default initialisation is made explicit - you have to pass
ZeroImpl<Private>() instead (and I firmly believe it's a good thing:
normally pointers to Private should not remain nullptr). The reason
ZeroImpl<> is not a template variable is quite simple: unique_ptr is
non-copyable and so cannot be initialised from; while a template
function will initialise the value in-place thanks to copy elision.

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/connection.cpp b/lib/connection.cpp
index 8d1c80f1..1915c2a9 100644
--- a/lib/connection.cpp
+++ b/lib/connection.cpp
@@ -246,7 +246,8 @@ public:
 };
 
 Connection::Connection(const QUrl& server, QObject* parent)
-    : QObject(parent), d(new Private(std::make_unique<ConnectionData>(server)))
+    : QObject(parent)
+    , d(makeImpl<Private>(std::make_unique<ConnectionData>(server)))
 {
     d->q = this; // All d initialization should occur before this line
 }