ClangCodeModel: Do not highlight objects in method calls

... as output arguments with clangd.
We might want to do so in the future, but right now it's not intended.

Task-number: QTCREATORBUG-27111
Change-Id: Ie6941f18943a1d6942901c526c62999cba6c1125
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/libs/languageserverprotocol/lsptypes.h

@@ -141,6 +141,12 @@ public:
     { return JsonObject::contains(startKey) && JsonObject::contains(endKey); }
 };
 
+inline bool operator==(const Range &r1, const Range &r2)
+{
+    return r1.contains(r2) && r2.contains(r1);
+}
+inline bool operator!=(const Range &r1, const Range &r2) { return !(r1 == r2); }
+
 class LANGUAGESERVERPROTOCOL_EXPORT Location : public JsonObject
 {
 public:

src/plugins/clangcodemodel/clangdclient.cpp

@@ -2723,6 +2723,19 @@ static void semanticHighlighter(QFutureInterface<HighlightingResult> &future,
                 return false;
             if (it->hasConstType())
                 return false;
+
+            if (it->kind() == "CXXMemberCall") {
+                if (it == path.rbegin())
+                    return false;
+                const QList<AstNode> children = it->children().value_or(QList<AstNode>());
+                QTC_ASSERT(!children.isEmpty(), return false);
+
+                // The called object is never displayed as an output parameter.
+                // TODO: A good argument can be made to display objects on which a non-const
+                //       operator or function is called as output parameters.
+                return (it - 1)->range() != children.first().range();
+            }
+
             if (it->kind() == "Member" && it->arcanaContains("(")
                     && !it->arcanaContains("bound member function type")) {
                 return false;

src/plugins/clangcodemodel/test/clangdtests.cpp

@@ -1310,6 +1310,7 @@ void ClangdTestHighlighting::test_data()
                                 << QList<int>{C_PREPROCESSOR} << 0;
     QTest::newRow("deref operator (object)") << 960 << 10 << 960 << 11 << QList<int>{C_LOCAL} << 0;
     QTest::newRow("deref operator (member)") << 960 << 12 << 960 << 13 << QList<int>{C_FIELD} << 0;
+    QTest::newRow("nested call") << 979 << 20 << 979 << 21 << QList<int>{C_LOCAL} << 0;
 }
 
 void ClangdTestHighlighting::test()
@@ -1397,6 +1398,8 @@ void ClangdTestHighlighting::test()
         QEXPECT_FAIL("non-final virtual function call via pointer",
                      "clangd < 14 does not send virtual modifier", Continue);
     }
+    QEXPECT_FAIL("non-const reference via member function call as output argument (object)",
+                 "See below", Continue);
     QEXPECT_FAIL("non-const reference via member function call as output argument (function)",
                  "Without punctuation and comment tokens from clangd, it's not possible "
                  "to highlight entire expressions. But do we really want this? What about nested "

src/plugins/clangcodemodel/test/data/highlighting/highlighting.cpp

@@ -960,3 +960,21 @@ void derefOperator()
     if (*s.s)
         return;
 }
+
+struct my_struct
+{
+    void* method(int dummy);
+};
+
+my_struct* get_my_struct();
+
+struct my_struct2
+{
+    my_struct2(void* p);
+};
+
+void nestedCall()
+{
+    my_struct* s = get_my_struct();
+    new my_struct2(s->method(0));
+}