ClangCodeModel: Make sure not to overwrite macros with their expansion

... when highlighting with clangd.

Change-Id: I89ec8bf5a1ed4d43e0e9a398b26705df00ca9a46
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangdclient.cpp

@@ -3140,6 +3140,18 @@ void ExtraHighlightingResultsCollector::insertResult(const HighlightingResult &r
         return;
     const auto it = std::lower_bound(m_results.begin(), m_results.end(), result, lessThan);
     if (it == m_results.end() || *it != result) {
+
+        // Prevent inserting expansions for function-like macros. For instance:
+        //     #define TEST() "blubb"
+        //     const char *s = TEST();
+        // The macro name is always shorter than the expansion and starts at the same
+        // location, so it should occur right before the insertion position.
+        if (it > m_results.begin() && (it - 1)->line == result.line
+                && (it - 1)->column == result.column
+                && (it - 1)->textStyles.mainStyle == C_PREPROCESSOR) {
+            return;
+        }
+
         qCDebug(clangdLogHighlight) << "adding additional highlighting result"
                                     << result.line << result.column << result.length;
         m_results.insert(it, result);