Algorithm: Add a member variant for transform

Change-Id: I329ee764cc13dd8b794c6769a2baf2f41d6a9983
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/utils/algorithm.h

@@ -282,6 +282,15 @@ decltype(auto) transform(const C &container, R (S::*p)() const)
             >::call(container, p);
 }
 
+template<typename C,
+         typename R,
+         typename S>
+Q_REQUIRED_RESULT
+decltype(auto) transform(const C &container, R S::*member)
+{
+    return transform(container, std::mem_fn(member));
+}
+
 // different container types for input and output, e.g. transforming a QList into a QSet
 template<template<typename> class C, // result container type
          typename SC, // input container type

tests/auto/algorithm/tst_algorithm.cpp

@@ -42,6 +42,16 @@ int stringToInt(const QString &s)
     return s.toInt();
 }
 
+namespace {
+struct Struct
+{
+    Struct(int m) : member(m) {}
+    bool operator==(const Struct &other) const { return member == other.member; }
+
+    int member;
+};
+}
+
 void tst_Algorithm::transform()
 {
     // same container type
@@ -110,16 +120,11 @@ void tst_Algorithm::transform()
         Utils::sort(i3);
         QCOMPARE(i3, QList<int>({1, 1, 3}));
     }
-}
-
-namespace {
-struct Struct
     {
-    Struct(int m) : member(m) {}
-    bool operator==(const Struct &other) const { return member == other.member; }
-
-    int member;
-};
+        const QList<Struct> list({4, 3, 2, 1, 2});
+        const QList<int> trans = Utils::transform(list, &Struct::member);
+        QCOMPARE(trans, QList<int>({4, 3, 2, 1, 2}));
+    }
 }
 
 void tst_Algorithm::sort()