ClangCodeModel: Properly highlight built-in defines

These are not reported as semantic tokens, so consult the AST

Task-number: QTCREATORBUG-27111
Change-Id: I38efcfbdc3197173a50033a74a1bc631eaa8d2c1
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/clangcodemodel/clangdclient.cpp

@@ -3598,8 +3598,16 @@ void ExtraHighlightingResultsCollector::collectFromNode(const AstNode &node)
     }
 
     const bool isExpression = node.role() == "expression";
-    const bool isDeclaration = node.role() == "declaration";
+    if (isExpression && node.kind() == "Predefined") {
+        HighlightingResult result;
+        result.useTextSyles = true;
+        result.textStyles.mainStyle = C_PREPROCESSOR;
+        setResultPosFromRange(result, node.range());
+        insertResult(result);
+        return;
+    }
 
+    const bool isDeclaration = node.role() == "declaration";
     const int nodeStartPos = posForNodeStart(node);
     const int nodeEndPos = posForNodeEnd(node);
     const QList<AstNode> children = node.children().value_or(QList<AstNode>());

src/plugins/clangcodemodel/test/clangdtests.cpp

@@ -1302,6 +1302,12 @@ void ClangdTestHighlighting::test_data()
                                                   << QList<int>{C_FIELD} << 0;
     QTest::newRow("output arg") << 945 << 20 << 945 << 23
                                 << QList<int>{C_LOCAL, C_OUTPUT_ARGUMENT} << 0;
+    QTest::newRow("built-in define 1") << 950 << 21 << 950 << 29
+                                << QList<int>{C_PREPROCESSOR} << 0;
+    QTest::newRow("built-in define 2") << 951 << 21 << 951 << 33
+                                << QList<int>{C_PREPROCESSOR} << 0;
+    QTest::newRow("built-in define 3") << 952 << 21 << 952 << 40
+                                << QList<int>{C_PREPROCESSOR} << 0;
 }
 
 void ClangdTestHighlighting::test()

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

@@ -944,3 +944,10 @@ void inputsAndOutputsFromObject(const WithVector &s)
     std::vector<int> out;
     transform(s.v, out, [] {});
 }
+
+void builtinDefines()
+{
+    const auto f1 = __func__;
+    const auto f2 = __FUNCTION__;
+    const auto f3 = __PRETTY_FUNCTION__;
+}