Constrain the comparison operators for our container classes

This had already been in very few places, where we ran into issues with
this before. More generic constraints here will significantly reduce the
amount of error messages a user has to parse in case he tries to instantiate
an operator by accident (or with a lacking comparison operator for one of
it's template arguments).

Change-Id: I1521d19c55d99732d9742402bd534c390a8e4242
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 3b9eb154ed..c2e5e12a1d 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -162,7 +162,8 @@ public:
 
     void swap(QList<T> &other) noexcept { qSwap(d, other.d); }
 
-    friend bool operator==(const QList &l, const QList &r)
+    template <typename U = T>
+    friend QTypeTraits::compare_eq_result<U> operator==(const QList &l, const QList &r)
     {
         if (l.size() != r.size())
             return false;
@@ -172,7 +173,8 @@ public:
         // do element-by-element comparison
         return l.d->compare(l.begin(), r.begin(), l.size());
     }
-    friend bool operator!=(const QList &l, const QList &r)
+    template <typename U = T>
+    friend QTypeTraits::compare_eq_result<U> operator!=(const QList &l, const QList &r)
     {
         return !(l == r);
     }