From b8144e0c51259994ea88bd1302776fced19a4755 Mon Sep 17 00:00:00 2001
From: Christian Kandeler <christian.kandeler@qt.io>
Date: Tue, 5 Apr 2022 12:57:17 +0200
Subject: 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            |  1 +
 src/libs/cplusplus/Overview.h              |  1 +
 src/libs/cplusplus/TypePrettyPrinter.cpp   | 22 +++++++++++++++++-----
 src/plugins/cppeditor/cppquickfix_test.cpp |  2 +-
 src/plugins/cppeditor/cppquickfixes.cpp    |  7 +++++++
 5 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/libs/cplusplus/Overview.cpp b/src/libs/cplusplus/Overview.cpp
index 7303791b06..02288d94cd 100644
--- a/src/libs/cplusplus/Overview.cpp
+++ b/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)
diff --git a/src/libs/cplusplus/Overview.h b/src/libs/cplusplus/Overview.h
index 243390cd8a..d12daa581f 100644
--- a/src/libs/cplusplus/Overview.h
+++ b/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;
diff --git a/src/libs/cplusplus/TypePrettyPrinter.cpp b/src/libs/cplusplus/TypePrettyPrinter.cpp
index d766a3f03b..b184e2a1e1 100644
--- a/src/libs/cplusplus/TypePrettyPrinter.cpp
+++ b/src/libs/cplusplus/TypePrettyPrinter.cpp
@@ -435,11 +435,17 @@ void TypePrettyPrinter::visit(Function *type)
     retAndArgOverview.showTemplateParameters = true;
 
     if (_overview->showReturnTypes) {
-        const QString returnType = retAndArgOverview.prettyType(type->returnType());
-        if (!returnType.isEmpty()) {
-            if (!endsWithPtrOrRef(returnType) || !(_overview->starBindFlags & Overview::BindToIdentifier))
-                _text.prepend(QLatin1Char(' '));
-            _text.prepend(returnType);
+        if (_overview->trailingReturnType) {
+            _text.prepend("auto ");
+        } else {
+            const QString returnType = retAndArgOverview.prettyType(type->returnType());
+            if (!returnType.isEmpty()) {
+                if (!endsWithPtrOrRef(returnType)
+                        || !(_overview->starBindFlags & Overview::BindToIdentifier)) {
+                    _text.prepend(QLatin1Char(' '));
+                }
+                _text.prepend(returnType);
+            }
         }
     }
 
@@ -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()
diff --git a/src/plugins/cppeditor/cppquickfix_test.cpp b/src/plugins/cppeditor/cppquickfix_test.cpp
index 93845b51c8..c0ee38d6e2 100644
--- a/src/plugins/cppeditor/cppquickfix_test.cpp
+++ b/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);
 
diff --git a/src/plugins/cppeditor/cppquickfixes.cpp b/src/plugins/cppeditor/cppquickfixes.cpp
index 7afc867297..6ed9736f3e 100644
--- a/src/plugins/cppeditor/cppquickfixes.cpp
+++ b/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;
-- 
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