moc: Support signals that return movable-only type

By adding std::move where it makes sense.
This is not only good for move-only types, but for any type which
can be moved as it saves copies of the return value in any case.

[ChangeLog][moc] Move-only types are now supported as return types
of signals and slots.

Change-Id: Idc9453af993e7574a6bddd4a87210eddd3da48a9
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

2 files changed, 3 insertions, 12 deletions

diff --git a/src/corelib/kernel/qobjectdefs_impl.h b/src/corelib/kernel/qobjectdefs_impl.h
index bd08ca1763..3f5f2e78bb 100644
--- a/src/corelib/kernel/qobjectdefs_impl.h
+++ b/src/corelib/kernel/qobjectdefs_impl.h
@@ -90,14 +90,9 @@ namespace QtPrivate {
         explicit ApplyReturnValue(void *data_) : data(data_) {}
     };
     template<typename T, typename U>
-    void operator,(const T &value, const ApplyReturnValue<U> &container) {
-        if (container.data)
-            *reinterpret_cast<U*>(container.data) = value;
-    }
-    template<typename T, typename U>
     void operator,(T &&value, const ApplyReturnValue<U> &container) {
         if (container.data)
-            *reinterpret_cast<U*>(container.data) = value;
+            *reinterpret_cast<U *>(container.data) = std::forward<T>(value);
     }
     template<typename T>
     void operator,(T, const ApplyReturnValue<void> &) {}
diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index db27067cf6..c4184929ef 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -1193,7 +1193,7 @@ void Generator::generateStaticMetacall()
             }
             fprintf(out, ");");
             if (f.normalizedType != "void") {
-                fprintf(out, "\n            if (_a[0]) *reinterpret_cast< %s*>(_a[0]) = _r; } ",
+                fprintf(out, "\n            if (_a[0]) *reinterpret_cast< %s*>(_a[0]) = std::move(_r); } ",
                         noRef(f.normalizedType).constData());
                 isUsed_a = true;
             }
@@ -1506,11 +1506,7 @@ void Generator::generateSignal(FunctionDef *def,int index)
     fprintf(out, ")%s\n{\n", constQualifier);
     if (def->type.name.size() && def->normalizedType != "void") {
         QByteArray returnType = noRef(def->normalizedType);
-        if (returnType.endsWith('*')) {
-            fprintf(out, "    %s _t0 = 0;\n", returnType.constData());
-        } else {
-            fprintf(out, "    %s _t0 = %s();\n", returnType.constData(), returnType.constData());
-        }
+        fprintf(out, "    %s _t0{};\n", returnType.constData());
     }
 
     fprintf(out, "    void *_a[] = { ");