CppEditor: Improve createContentProposal()

- Limit iterator scope
- Replace if-else chain with early continue
- Save an unneeded look-up

Change-Id: If90f726ddb21a516ed3d438379382a2e4cd248a9
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/cppeditor/cppcompletionassist.cpp

@@ -37,6 +37,8 @@
 #include <QTextDocument>
 #include <QIcon>
 
+#include <set>
+
 using namespace CPlusPlus;
 using namespace CppEditor;
 using namespace TextEditor;
@@ -847,14 +849,18 @@ bool InternalCppCompletionAssistProcessor::accepts() const
 IAssistProposal *InternalCppCompletionAssistProcessor::createContentProposal()
 {
     // Duplicates are kept only if they are snippets.
-    QSet<QString> processed;
-    auto it = m_completions.begin();
-    while (it != m_completions.end()) {
+    std::set<QString> processed;
+    for (auto it = m_completions.begin(); it != m_completions.end();) {
         if ((*it)->isSnippet()) {
             ++it;
-        } else if (!processed.contains((*it)->text())) {
+            continue;
+        }
+        if (!processed.insert((*it)->text()).second) {
+            delete *it;
+            it = m_completions.erase(it);
+            continue;
+        }
         auto item = static_cast<CppAssistProposalItem *>(*it);
-            processed.insert(item->text());
         if (!item->isOverloaded()) {
             if (auto symbol = qvariant_cast<Symbol *>(item->data())) {
                 if (Function *funTy = symbol->type()->asFunctionType()) {
@@ -864,10 +870,6 @@ IAssistProposal *InternalCppCompletionAssistProcessor::createContentProposal()
             }
         }
         ++it;
-        } else {
-            delete *it;
-            it = m_completions.erase(it);
-        }
     }
 
     m_model->loadContent(m_completions);