CppEditor: Use trailing return type when moving function definition

... if the original definition also used a trailing return type.

Task-number: QTCREATORBUG-27132
Change-Id: Iaeeeac08601f1d931aabe12be9f89ca0240d97a2
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/libs/cplusplus/Overview.cpp

@@ -86,6 +86,7 @@ Overview::Overview()
       showTemplateParameters(false),
       showEnclosingTemplate(false),
       includeWhiteSpaceInOperatorName(true),
+      trailingReturnType(false),
       markedArgument(0),
       markedArgumentBegin(0),
       markedArgumentEnd(0)

src/libs/cplusplus/Overview.h

@@ -69,6 +69,7 @@ public:
     bool showTemplateParameters: 1;
     bool showEnclosingTemplate: 1;
     bool includeWhiteSpaceInOperatorName: 1; /// "operator =()" vs "operator=()"
+    bool trailingReturnType: 1;
 
     int markedArgument;
     int markedArgumentBegin;

src/libs/cplusplus/TypePrettyPrinter.cpp

@@ -435,13 +435,19 @@ void TypePrettyPrinter::visit(Function *type)
     retAndArgOverview.showTemplateParameters = true;
 
     if (_overview->showReturnTypes) {
+        if (_overview->trailingReturnType) {
+            _text.prepend("auto ");
+        } else {
             const QString returnType = retAndArgOverview.prettyType(type->returnType());
             if (!returnType.isEmpty()) {
-            if (!endsWithPtrOrRef(returnType) || !(_overview->starBindFlags & Overview::BindToIdentifier))
+                if (!endsWithPtrOrRef(returnType)
+                        || !(_overview->starBindFlags & Overview::BindToIdentifier)) {
                     _text.prepend(QLatin1Char(' '));
+                }
                 _text.prepend(returnType);
             }
         }
+    }
 
     if (_overview->showEnclosingTemplate) {
         if (Template *templ = type->enclosingTemplate()) {
@@ -529,6 +535,12 @@ void TypePrettyPrinter::visit(Function *type)
             _text += QLatin1String(spec->chars());
         }
     }
+
+    if (_overview->showReturnTypes && _overview->trailingReturnType) {
+        const QString returnType = retAndArgOverview.prettyType(type->returnType());
+        if (!returnType.isEmpty())
+            _text.append(" -> ").append(returnType);
+    }
 }
 
 void TypePrettyPrinter::appendSpace()

src/plugins/cppeditor/cppquickfix_test.cpp

@@ -6137,7 +6137,7 @@ struct Derived : public Base {
     original = "#include \"file.h\"\n";
     expected = R"DELIM(#include "file.h"
 
-void Derived::func() const &&noexcept {}
+auto Derived::func() const &&noexcept -> void {}
 )DELIM";
     testDocuments << CppTestDocument::create("file.cpp", original, expected);
 

src/plugins/cppeditor/cppquickfixes.cpp

@@ -6234,6 +6234,13 @@ QString definitionSignature(const CppQuickFixInterface *assist,
     oo.showArgumentNames = true;
     oo.showEnclosingTemplate = true;
     oo.showTemplateParameters = true;
+    oo.trailingReturnType = functionDefinitionAST->declarator
+            && functionDefinitionAST->declarator->postfix_declarator_list
+            && functionDefinitionAST->declarator->postfix_declarator_list->value
+            && functionDefinitionAST->declarator->postfix_declarator_list
+                    ->value->asFunctionDeclarator()
+            && functionDefinitionAST->declarator->postfix_declarator_list
+                    ->value->asFunctionDeclarator()->trailing_return_type;
     const Name *name = func->name();
     if (name && nameIncludesOperatorName(name)) {
         CoreDeclaratorAST *coreDeclarator = functionDefinitionAST->declarator->core_declarator;