Long live std::pair!

Make QPair an alias for std::pair, and qMakePair just a forwarder
towards std::make_pair.

Why? Fundamentally to ditch a bunch of NIH code; gain for free
structured bindings, std::tuple and std::reference_wrapper
compatibility, and so on.

Breakages:

* Some that code manually forward declares QPair.
We don't care about it (<QContainerFwd> is the proper way).

* Some code that overloads on std::pair and QPair. Luckily
it's mostly centralized: debug, metatypes, testing macros.
Just remove the QPair overload.

* Usages of qMakePair forcing the template type parameters.
There are a handful of these in qtbase, but only one was actually
broken.

* std::pair is NOT (and will never likely be) trivially copiable.
This is agreed to be a mistake done by practically all implementations
in C++11, can can't be fixed without breaking ABI.
Some code using QPair assuming it's trivially copiable may break;
exactly one occurrence was in qtbase.

* QMetaType logic extracts the type names in two different ways,
one by looking at the source code string (e.g. extracted by moc)
and one via some ad-hoc reflection in C++. We need to make
"QPair" (as spelled in the source code) be the same as "std::pair"
(gathered via reflection, which will see through the alias)
when compared. The way it's already done e.g. for QList is
by actually replacing the moc-extracted name with the name
of the actual type used in C++; do the same here.
On libc++, std::pair is actually in an inline namespace --
i.e. std::__1::pair; the reflection will extract and store
"std::__1::pair" so we need an ad-hoc fix to QMetaType.

[ChangeLog][QtCore][QPair] QPair is now an alias to std::pair,
and does not exist as a class in Qt any more. This may break
code such as functions overloaded for both QPair and std::pair.
Usually, the overload taking a QPair can be safely discarded,
leaving only the one taking a std::pair. QPair API has not changed,
and qMakePair is still available for compatibility (although
new code is encouraged to use std::pair and std::make_pair
directly instead).

Change-Id: I7725c751bf23946cde577b1406e86a336c0a3dcf
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 3 insertions, 3 deletions

diff --git a/tests/auto/network/kernel/qauthenticator/tst_qauthenticator.cpp b/tests/auto/network/kernel/qauthenticator/tst_qauthenticator.cpp
index 8cef351554..94a998a6a6 100644
--- a/tests/auto/network/kernel/qauthenticator/tst_qauthenticator.cpp
+++ b/tests/auto/network/kernel/qauthenticator/tst_qauthenticator.cpp
@@ -82,7 +82,7 @@ void tst_QAuthenticator::basicAuth()
     QCOMPARE(priv->phase, QAuthenticatorPrivate::Start);
 
     QList<QPair<QByteArray, QByteArray> > headers;
-    headers << qMakePair<QByteArray, QByteArray>(QByteArray("WWW-Authenticate"), "Basic " + data.toUtf8());
+    headers << qMakePair(QByteArray("WWW-Authenticate"), "Basic " + data.toUtf8());
     priv->parseHttpResponse(headers, /*isProxy = */ false);
 
     QCOMPARE(auth.realm(), realm);
@@ -130,7 +130,7 @@ void tst_QAuthenticator::ntlmAuth()
     // This phase of NTLM contains no information, other than what we're willing to negotiate
     // Current implementation uses flags:
     //  NTLMSSP_NEGOTIATE_UNICODE | NTLMSSP_NEGOTIATE_NTLM | NTLMSSP_REQUEST_TARGET
-    headers << qMakePair<QByteArray, QByteArray>("WWW-Authenticate", "NTLM");
+    headers << qMakePair(QByteArrayLiteral("WWW-Authenticate"), QByteArrayLiteral("NTLM"));
     priv->parseHttpResponse(headers, /*isProxy = */ false);
     if (sso)
         QVERIFY(priv->calculateResponse("GET", "/", "").startsWith("NTLM "));
@@ -139,7 +139,7 @@ void tst_QAuthenticator::ntlmAuth()
 
     // NTLM phase 2: challenge
     headers.clear();
-    headers << qMakePair<QByteArray, QByteArray>(QByteArray("WWW-Authenticate"), "NTLM " + data.toUtf8());
+    headers << qMakePair(QByteArray("WWW-Authenticate"), "NTLM " + data.toUtf8());
     priv->parseHttpResponse(headers, /*isProxy = */ false);
 
     QEXPECT_FAIL("with-realm", "NTLM authentication code doesn't extract the realm", Continue);