QCOMPARE: restore compatibility with braced-init-lists

a611a9f537f1187825339c2a2214c8ec4a23680f (in Qt 5) added support for
mixed-type comparisons through QCOMPARE. That commit added a new
overload for qCompare taking two types, T1 and T2; but it also left the
same-type qCompare(T, T) overload around, guarded by a Qt 6 version
check.

The mixed-type version is however not a generalization of the same-type
one, because it won't work if one of the arguments doesn't participate
in FTAD. Case in point: braced-init-lists. In Qt 5 this worked:

 QCOMPARE(some_container, {42});

but in Qt 6 it does not work any more. The mixed-type overload fails
deduction (can't deduce T2); in Qt 5 the same-type overload deduced
T=SomeContainer, and {42} was used to select a constructor for
SomeContainer.

--

There's a partial, straightforward workaround for this: default T2 to
T1 in the mized-type overload. In that case T2 has a "fallback" if it
cannot be deduced. This is partial because of course doesn't address
the case in which T1 cannot be deduced, but I don't think that is
common at all.

QList is special here, because it has qCompare overloads that makes it
comparable with arrays, initializer lists and more. I don't like that
very much -- we should probably have a qCompare(input_range,
input_range) overload, but that's an exercise for C++20.

Change-Id: I344ba33167829984978cd8d649a1904349a9edab
Pick-to: 6.5 6.6
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

8 files changed, 72 insertions, 38 deletions

diff --git a/src/testlib/qtestcase.h b/src/testlib/qtestcase.h
index 95a1d9160a..7eea2b7b32 100644
--- a/src/testlib/qtestcase.h
+++ b/src/testlib/qtestcase.h
@@ -582,7 +582,7 @@ namespace QTest
     QTEST_COMPARE_DECL(bool)
 #endif
 
-    template <typename T1, typename T2>
+    template <typename T1, typename T2 = T1>
     inline bool qCompare(const T1 &t1, const T2 &t2, const char *actual, const char *expected,
                          const char *file, int line)
     {
diff --git a/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp b/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
index 7a3817c63d..f8cf3845b1 100644
--- a/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
+++ b/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
@@ -12,6 +12,8 @@
 #include <QtGui/QVector3D>
 #include <QtGui/QVector4D>
 #endif
+#include <QSet>
+#include <vector>
 using namespace Qt::StringLiterals;
 
 /* XPM test data for QPixmap, QImage tests (use drag cursors as example) */
@@ -127,6 +129,7 @@ private slots:
     void compareQListIntToInitializerList_data();
     void compareQListIntToInitializerList();
     void compareQListDouble();
+    void compareContainerToInitializerList();
 #ifdef QT_GUI_LIB
     void compareQColor_data();
     void compareQColor();
@@ -506,6 +509,24 @@ void tst_Cmptest::compareQListDouble()
     QCOMPARE(double1, double2);
 }
 
+void tst_Cmptest::compareContainerToInitializerList()
+{
+    // Protect ',' in the list
+#define ARG(...) __VA_ARGS__
+    QSet<int> set{1, 2, 3};
+    QCOMPARE(set, ARG({1, 2, 3}));
+
+    std::vector<int> vec{1, 2, 3};
+    QCOMPARE(vec, ARG({1, 2, 3}));
+
+    vec.clear();
+    QCOMPARE(vec, {});
+
+    vec.push_back(42);
+    QCOMPARE(vec, {42});
+#undef ARG
+}
+
 #ifdef QT_GUI_LIB
 void tst_Cmptest::compareQColor_data()
 {
diff --git a/tests/auto/testlib/selftests/expected_cmptest.junitxml b/tests/auto/testlib/selftests/expected_cmptest.junitxml
index 7ec9e2e05f..3f042d6ac0 100644
--- a/tests/auto/testlib/selftests/expected_cmptest.junitxml
+++ b/tests/auto/testlib/selftests/expected_cmptest.junitxml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" ?>
-<testsuite name="tst_Cmptest" timestamp="@TEST_START_TIME@" hostname="@HOSTNAME@" tests="70" failures="49" errors="0" skipped="0" time="@TEST_DURATION@">
+<testsuite name="tst_Cmptest" timestamp="@TEST_START_TIME@" hostname="@HOSTNAME@" tests="71" failures="49" errors="0" skipped="0" time="@TEST_DURATION@">
   <properties>
     <property name="QTestVersion" value="@INSERT_QT_VERSION_HERE@"/>
     <property name="QtVersion" value="@INSERT_QT_VERSION_HERE@"/>
@@ -173,6 +173,7 @@
    Expected (double2): 1]]>
     </failure>
   </testcase>
+  <testcase name="compareContainerToInitializerList" classname="tst_Cmptest" time="@TEST_DURATION@"/>
   <testcase name="compareQColor(Qt::yellow vs &quot;yellow&quot;)" classname="tst_Cmptest" time="@TEST_DURATION@"/>
   <testcase name="compareQColor(Qt::yellow vs Qt::green)" classname="tst_Cmptest" time="@TEST_DURATION@">
     <failure type="fail" message="Compared values are not the same">
diff --git a/tests/auto/testlib/selftests/expected_cmptest.lightxml b/tests/auto/testlib/selftests/expected_cmptest.lightxml
index 6328632c69..9a8e9b4b91 100644
--- a/tests/auto/testlib/selftests/expected_cmptest.lightxml
+++ b/tests/auto/testlib/selftests/expected_cmptest.lightxml
@@ -234,6 +234,10 @@
     </Incident>
     <Duration msecs="0"/>
   </TestFunction>
+  <TestFunction name="compareContainerToInitializerList">
+    <Incident type="pass" file="" line="0" />
+    <Duration msecs="0"/>
+  </TestFunction>
   <TestFunction name="compareQColor">
     <Incident type="pass" file="" line="0">
       <DataTag><![CDATA[Qt::yellow vs "yellow"]]></DataTag>
diff --git a/tests/auto/testlib/selftests/expected_cmptest.tap b/tests/auto/testlib/selftests/expected_cmptest.tap
index 368d3aafb4..3e460903b8 100644
--- a/tests/auto/testlib/selftests/expected_cmptest.tap
+++ b/tests/auto/testlib/selftests/expected_cmptest.tap
@@ -303,8 +303,9 @@ not ok 38 - compareQListDouble()
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-ok 39 - compareQColor(Qt::yellow vs "yellow")
-not ok 40 - compareQColor(Qt::yellow vs Qt::green)
+ok 39 - compareContainerToInitializerList()
+ok 40 - compareQColor(Qt::yellow vs "yellow")
+not ok 41 - compareQColor(Qt::yellow vs Qt::green)
   ---
   type: QCOMPARE
   message: Compared values are not the same
@@ -316,7 +317,7 @@ not ok 40 - compareQColor(Qt::yellow vs Qt::green)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 41 - compareQColor(0x88ff0000 vs 0xffff0000)
+not ok 42 - compareQColor(0x88ff0000 vs 0xffff0000)
   ---
   type: QCOMPARE
   message: Compared values are not the same
@@ -328,8 +329,8 @@ not ok 41 - compareQColor(0x88ff0000 vs 0xffff0000)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-ok 42 - compareQPixmaps(both null)
-not ok 43 - compareQPixmaps(one null)
+ok 43 - compareQPixmaps(both null)
+not ok 44 - compareQPixmaps(one null)
   ---
   type: QCOMPARE
   message: Compared QPixmaps differ.
@@ -341,7 +342,7 @@ not ok 43 - compareQPixmaps(one null)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 44 - compareQPixmaps(other null)
+not ok 45 - compareQPixmaps(other null)
   ---
   type: QCOMPARE
   message: Compared QPixmaps differ.
@@ -353,8 +354,8 @@ not ok 44 - compareQPixmaps(other null)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-ok 45 - compareQPixmaps(equal)
-not ok 46 - compareQPixmaps(different size)
+ok 46 - compareQPixmaps(equal)
+not ok 47 - compareQPixmaps(different size)
   ---
   type: QCOMPARE
   message: Compared QPixmaps differ in size.
@@ -366,14 +367,14 @@ not ok 46 - compareQPixmaps(different size)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 47 - compareQPixmaps(different pixels)
+not ok 48 - compareQPixmaps(different pixels)
   ---
   # Compared values are not the same
   at: tst_Cmptest::compareQPixmaps() (qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp:0)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 48 - compareQPixmaps(different dpr)
+not ok 49 - compareQPixmaps(different dpr)
   ---
   type: QCOMPARE
   message: Compared QPixmaps differ in device pixel ratio.
@@ -385,8 +386,8 @@ not ok 48 - compareQPixmaps(different dpr)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-ok 49 - compareQImages(both null)
-not ok 50 - compareQImages(one null)
+ok 50 - compareQImages(both null)
+not ok 51 - compareQImages(one null)
   ---
   type: QCOMPARE
   message: Compared QImages differ.
@@ -398,7 +399,7 @@ not ok 50 - compareQImages(one null)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 51 - compareQImages(other null)
+not ok 52 - compareQImages(other null)
   ---
   type: QCOMPARE
   message: Compared QImages differ.
@@ -410,8 +411,8 @@ not ok 51 - compareQImages(other null)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-ok 52 - compareQImages(equal)
-not ok 53 - compareQImages(different size)
+ok 53 - compareQImages(equal)
+not ok 54 - compareQImages(different size)
   ---
   type: QCOMPARE
   message: Compared QImages differ in size.
@@ -423,7 +424,7 @@ not ok 53 - compareQImages(different size)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 54 - compareQImages(different format)
+not ok 55 - compareQImages(different format)
   ---
   type: QCOMPARE
   message: Compared QImages differ in format.
@@ -435,14 +436,14 @@ not ok 54 - compareQImages(different format)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 55 - compareQImages(different pixels)
+not ok 56 - compareQImages(different pixels)
   ---
   # Compared values are not the same
   at: tst_Cmptest::compareQImages() (qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp:0)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 56 - compareQImages(different dpr)
+not ok 57 - compareQImages(different dpr)
   ---
   type: QCOMPARE
   message: Compared QImages differ in device pixel ratio.
@@ -454,8 +455,8 @@ not ok 56 - compareQImages(different dpr)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-ok 57 - compareQRegion(equal-empty)
-not ok 58 - compareQRegion(1-empty)
+ok 58 - compareQRegion(equal-empty)
+not ok 59 - compareQRegion(1-empty)
   ---
   type: QCOMPARE
   message: Compared values are not the same
@@ -467,8 +468,8 @@ not ok 58 - compareQRegion(1-empty)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-ok 59 - compareQRegion(equal)
-not ok 60 - compareQRegion(different lists)
+ok 60 - compareQRegion(equal)
+not ok 61 - compareQRegion(different lists)
   ---
   type: QCOMPARE
   message: Compared values are not the same
@@ -480,7 +481,7 @@ not ok 60 - compareQRegion(different lists)
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 61 - compareQVector2D()
+not ok 62 - compareQVector2D()
   ---
   type: QCOMPARE
   message: Compared values are not the same
@@ -492,7 +493,7 @@ not ok 61 - compareQVector2D()
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 62 - compareQVector3D()
+not ok 63 - compareQVector3D()
   ---
   type: QCOMPARE
   message: Compared values are not the same
@@ -504,7 +505,7 @@ not ok 62 - compareQVector3D()
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 63 - compareQVector4D()
+not ok 64 - compareQVector4D()
   ---
   type: QCOMPARE
   message: Compared values are not the same
@@ -516,7 +517,7 @@ not ok 63 - compareQVector4D()
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 64 - tryCompare()
+not ok 65 - tryCompare()
   ---
   type: QCOMPARE
   message: Compared values are not the same
@@ -532,7 +533,7 @@ not ok 64 - tryCompare()
     - severity: info
       message: Should now time out and fail
   ...
-not ok 65 - verify()
+not ok 66 - verify()
   ---
   type: QVERIFY
   message: Verification failed
@@ -544,7 +545,7 @@ not ok 65 - verify()
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 66 - verify2()
+not ok 67 - verify2()
   ---
   type: QVERIFY
   message: 42 >= 2 (as expected, in fact)
@@ -556,7 +557,7 @@ not ok 66 - verify2()
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-not ok 67 - tryVerify()
+not ok 68 - tryVerify()
   ---
   type: QVERIFY
   message: Verification failed
@@ -572,7 +573,7 @@ not ok 67 - tryVerify()
     - severity: info
       message: Should now time out and fail
   ...
-not ok 68 - tryVerify2()
+not ok 69 - tryVerify2()
   ---
   type: QVERIFY
   message: Should time out and fail
@@ -584,9 +585,9 @@ not ok 68 - tryVerify2()
   file: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp
   line: 0
   ...
-ok 69 - verifyExplicitOperatorBool()
-ok 70 - cleanupTestCase()
-1..70
-# tests 70
-# pass 21
+ok 70 - verifyExplicitOperatorBool()
+ok 71 - cleanupTestCase()
+1..71
+# tests 71
+# pass 22
 # fail 49
diff --git a/tests/auto/testlib/selftests/expected_cmptest.teamcity b/tests/auto/testlib/selftests/expected_cmptest.teamcity
index dfc8cdb2ce..7c7e64b9f2 100644
--- a/tests/auto/testlib/selftests/expected_cmptest.teamcity
+++ b/tests/auto/testlib/selftests/expected_cmptest.teamcity
@@ -101,6 +101,8 @@
 ##teamcity[testStarted name='compareQListDouble()' flowId='tst_Cmptest']
 ##teamcity[testFailed name='compareQListDouble()' message='Failure! |[Loc: qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp(0)|]' details='Compared lists differ at index 0.|n Actual (double1): 1.5|n Expected (double2): 1' flowId='tst_Cmptest']
 ##teamcity[testFinished name='compareQListDouble()' flowId='tst_Cmptest']
+##teamcity[testStarted name='compareContainerToInitializerList()' flowId='tst_Cmptest']
+##teamcity[testFinished name='compareContainerToInitializerList()' flowId='tst_Cmptest']
 ##teamcity[testStarted name='compareQColor(Qt::yellow vs "yellow")' flowId='tst_Cmptest']
 ##teamcity[testFinished name='compareQColor(Qt::yellow vs "yellow")' flowId='tst_Cmptest']
 ##teamcity[testStarted name='compareQColor(Qt::yellow vs Qt::green)' flowId='tst_Cmptest']
diff --git a/tests/auto/testlib/selftests/expected_cmptest.txt b/tests/auto/testlib/selftests/expected_cmptest.txt
index 602202bafc..9d96fb7643 100644
--- a/tests/auto/testlib/selftests/expected_cmptest.txt
+++ b/tests/auto/testlib/selftests/expected_cmptest.txt
@@ -116,6 +116,7 @@ FAIL!  : tst_Cmptest::compareQListDouble() Compared lists differ at index 0.
    Actual   (double1): 1.5
    Expected (double2): 1
    Loc: [qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp(0)]
+PASS   : tst_Cmptest::compareContainerToInitializerList()
 PASS   : tst_Cmptest::compareQColor(Qt::yellow vs "yellow")
 FAIL!  : tst_Cmptest::compareQColor(Qt::yellow vs Qt::green) Compared values are not the same
    Actual   (colorA): #ffffff00
@@ -207,5 +208,5 @@ FAIL!  : tst_Cmptest::tryVerify2() '!c' returned FALSE. (Should time out and fai
    Loc: [qtbase/tests/auto/testlib/selftests/cmptest/tst_cmptest.cpp(0)]
 PASS   : tst_Cmptest::verifyExplicitOperatorBool()
 PASS   : tst_Cmptest::cleanupTestCase()
-Totals: 21 passed, 49 failed, 0 skipped, 0 blacklisted, 0ms
+Totals: 22 passed, 49 failed, 0 skipped, 0 blacklisted, 0ms
 ********* Finished testing of tst_Cmptest *********
diff --git a/tests/auto/testlib/selftests/expected_cmptest.xml b/tests/auto/testlib/selftests/expected_cmptest.xml
index a0e8e76179..ba9d617aed 100644
--- a/tests/auto/testlib/selftests/expected_cmptest.xml
+++ b/tests/auto/testlib/selftests/expected_cmptest.xml
@@ -236,6 +236,10 @@
     </Incident>
     <Duration msecs="0"/>
   </TestFunction>
+  <TestFunction name="compareContainerToInitializerList">
+    <Incident type="pass" file="" line="0" />
+    <Duration msecs="0"/>
+  </TestFunction>
   <TestFunction name="compareQColor">
     <Incident type="pass" file="" line="0">
       <DataTag><![CDATA[Qt::yellow vs "yellow"]]></DataTag>