ClangCodeModel: Do not traverse the AST in the semantic highlighter

... with clangd >= 17. We do not need to look at AST nodes anymore;
everything comes from the server.

Change-Id: I46eb91f26515e31b752020edbc32f1b23c1d79c7
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/plugins/clangcodemodel/clangdclient.cpp

@@ -1468,6 +1468,9 @@ void ClangdClient::Private::handleSemanticTokens(TextDocument *doc,
         data.highlighter->setHighlightingRunner(runner);
         data.highlighter->run();
     };
+    if (q->versionNumber().majorVersion() >= 17)
+        astHandler({}, {});
+    else
         getAndHandleAst(doc, astHandler, AstCallbackMode::SyncIfPossible);
 }
 

src/plugins/clangcodemodel/clangdsemantichighlighting.cpp

@@ -461,6 +461,7 @@ void ExtraHighlightingResultsCollector::collect()
 
     if (!m_ast.isValid())
         return;
+    QTC_ASSERT(m_clangdVersion < 17, return);
     visitNode(m_ast);
 }
 
@@ -656,7 +657,6 @@ void ExtraHighlightingResultsCollector::collectFromNode(const ClangdAstNode &nod
         return;
     }
 
-    if (m_clangdVersion < 17) {
     if (isDeclaration && (node.kind() == "FunctionTemplate" || node.kind() == "ClassTemplate")) {
         // The child nodes are the template parameters and and the function or class.
         // The opening angle bracket is before the first child node, the closing angle
@@ -776,7 +776,6 @@ void ExtraHighlightingResultsCollector::collectFromNode(const ClangdAstNode &nod
         }
         return;
     }
-    }
 
     if (!isExpression && !isDeclaration)
         return;