CppEditor: Consider comments when extracting a new function

That is, do not place the newly created function in between the function
and its comment.

Fixes: QTCREATORBUG-6934
Change-Id: I79f564a90c7e3c45188f5d694cbde47029651324
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/cppeditor/cppquickfix_test.cpp

@@ -7843,7 +7843,8 @@ void QuickfixTest::testExtractFunction_data()
     QTest::addColumn<QByteArray>("expected");
 
     QTest::newRow("basic")
-        << _("void f()\n"
+        << _("// Documentation for f\n"
+             "void f()\n"
              "{\n"
              "    @{start}g();@{end}\n"
              "}\n")
@@ -7852,6 +7853,7 @@ void QuickfixTest::testExtractFunction_data()
              "    g();\n"
              "}\n"
              "\n"
+             "// Documentation for f\n"
              "void f()\n"
              "{\n"
              "    extracted();\n"

src/plugins/cppeditor/cppquickfixes.cpp

@@ -27,6 +27,7 @@
 #include <cplusplus/ASTPath.h>
 #include <cplusplus/CPlusPlusForwardDeclarations.h>
 #include <cplusplus/CppRewriter.h>
+#include <cplusplus/declarationcomments.h>
 #include <cplusplus/NamePrettyPrinter.h>
 #include <cplusplus/TypeOfExpression.h>
 #include <cplusplus/TypePrettyPrinter.h>
@@ -5150,6 +5151,16 @@ public:
         // formatting) it's simpler to have two different change sets.
         ChangeSet change;
         int position = currentFile->startOf(m_refFuncDef);
+
+        // Do not insert right between the function and an associated comment.
+        const QList<Token> functionDoc = commentsForDeclaration(
+            m_refFuncDef->symbol, m_refFuncDef, *currentFile->document(),
+            currentFile->cppDocument());
+        if (!functionDoc.isEmpty()) {
+            position = currentFile->cppDocument()->translationUnit()->getTokenPositionInDocument(
+                functionDoc.first(), currentFile->document());
+        }
+
         change.insert(position, funcDef);
         change.replace(m_extractionStart, m_extractionEnd, funcCall);
         currentFile->setChangeSet(change);