unneeded-cast: Improve warning message for unneeded qobject_cast

Instead of saying that no cast to base is needed, simply say that
no qobject_cast is needed. Since a static_cast might still be needed.

This is the case for the ternary operator.

BUG: 407981

3 files changed, 16 insertions, 6 deletions

diff --git a/src/checks/manuallevel/unneeded-cast.cpp b/src/checks/manuallevel/unneeded-cast.cpp
index 46c90b98..1b7aae67 100644
--- a/src/checks/manuallevel/unneeded-cast.cpp
+++ b/src/checks/manuallevel/unneeded-cast.cpp
@@ -105,10 +105,10 @@ bool UnneededCast::handleQObjectCast(Stmt *stm)
     if (!clazy::is_qobject_cast(stm, &castTo, &castFrom))
         return false;
 
-    return maybeWarn(stm, castFrom, castTo);
+    return maybeWarn(stm, castFrom, castTo, /*isQObjectCast=*/ true);
 }
 
-bool UnneededCast::maybeWarn(Stmt *stmt, CXXRecordDecl *castFrom, CXXRecordDecl *castTo)
+bool UnneededCast::maybeWarn(Stmt *stmt, CXXRecordDecl *castFrom, CXXRecordDecl *castTo, bool isQObjectCast)
 {
     castFrom = castFrom->getCanonicalDecl();
     castTo = castTo->getCanonicalDecl();
@@ -117,7 +117,17 @@ bool UnneededCast::maybeWarn(Stmt *stmt, CXXRecordDecl *castFrom, CXXRecordDecl
         emitWarning(clazy::getLocStart(stmt), "Casting to itself");
         return true;
     } else if (clazy::derivesFrom(/*child=*/ castFrom, castTo)) {
-        emitWarning(clazy::getLocStart(stmt), "explicitly casting to base is unnecessary");
+        if (isQObjectCast) {
+            const bool isTernaryOperator = clazy::getFirstParentOfType<ConditionalOperator>(m_context->parentMap, stmt) != nullptr;
+            if (isTernaryOperator) {
+                emitWarning(clazy::getLocStart(stmt), "use static_cast instead of qobject_cast");
+            } else {
+                emitWarning(clazy::getLocStart(stmt), "explicitly casting to base is unnecessary");
+            }
+        } else {
+            emitWarning(clazy::getLocStart(stmt), "explicitly casting to base is unnecessary");
+        }
+
         return true;
     }
 
diff --git a/src/checks/manuallevel/unneeded-cast.h b/src/checks/manuallevel/unneeded-cast.h
index 1e40b22c..53d6e4b3 100644
--- a/src/checks/manuallevel/unneeded-cast.h
+++ b/src/checks/manuallevel/unneeded-cast.h
@@ -53,7 +53,7 @@ public:
 private:
     bool handleNamedCast(clang::CXXNamedCastExpr *);
     bool handleQObjectCast(clang::Stmt *);
-    bool maybeWarn(clang::Stmt *, clang::CXXRecordDecl *from, clang::CXXRecordDecl *to);
+    bool maybeWarn(clang::Stmt *, clang::CXXRecordDecl *from, clang::CXXRecordDecl *to, bool isQObjectCast = false);
 };
 
 #endif
diff --git a/tests/unneeded-cast/main.cpp b/tests/unneeded-cast/main.cpp
index 808e1a87..ab7b3087 100644
--- a/tests/unneeded-cast/main.cpp
+++ b/tests/unneeded-cast/main.cpp
@@ -83,9 +83,9 @@ void test2()
 
     MyObj *o1;
     MyObj2 *o2;
-    true ? static_cast<QObject*>(o1)  : static_cast<QObject*>(o2); // Ok
+    true ? static_cast<QObject*>(o1) : static_cast<QObject*>(o2); // Ok
+    true ? qobject_cast<QObject*>(o1) : qobject_cast<QObject*>(o2); // Ok
 }
-
 class MyObj4 : public QObject
 {
     Q_OBJECT