qmlformat: Preserve variable declaration scope type

If the user used for(let x;...) we need to preserve the let and must not
change it to var.

Pick-to: 6.2 6.3 6.4
Fixes: QTBUG-105361
Change-Id: I49fc3797505b569cc9b8a9138dd57ec7e70d3eb9
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/qmldom/qqmldomreformatter.cpp

@@ -552,16 +552,27 @@ class Rewriter : protected BaseVisitor
         return false;
     }
 
+
+    void outputScope(VariableScope scope) {
+        switch (scope) {
+        case VariableScope::Const:
+            out("const ");
+            break;
+        case VariableScope::Let:
+            out("let ");
+            break;
+        case VariableScope::Var:
+            out("var ");
+            break;
+        default:
+            break;
+        }
+    }
+
     bool visit(PatternElement *ast) override
     {
         if (ast->isForDeclaration) {
-            if (ast->scope == VariableScope::Var) {
-                out("var ");
-            } else if (ast->scope == VariableScope::Let) {
-                out("let ");
-            } else if (ast->scope == VariableScope::Const) {
-                out("const ");
-            }
+            outputScope(ast->scope);
         }
         accept(ast->bindingTarget);
         switch (ast->type) {
@@ -647,7 +658,7 @@ class Rewriter : protected BaseVisitor
         if (ast->initialiser) {
             accept(ast->initialiser);
         } else if (ast->declarations) {
-            out("var ");
+            outputScope(ast->declarations->declaration->scope);
             accept(ast->declarations);
         }
         out("; "); // ast->firstSemicolonToken

tests/auto/qml/qmlformat/data/forWithLet.formatted.qml

@@ -0,0 +1,8 @@
+import QtQml
+
+QtObject {
+    function foo() {
+        for (let i = 0; i < 5; ++i)
+            console.log(i);
+    }
+}

tests/auto/qml/qmlformat/data/forWithLet.qml

@@ -0,0 +1,8 @@
+import QtQml
+
+QtObject {
+function foo() {
+for (let i = 0; i < 5; ++i)
+console.log(i);
+}
+}

tests/auto/qml/qmlformat/tst_qmlformat.cpp

@@ -273,6 +273,9 @@ void TestQmlformat::testFormat_data()
     QTest::newRow("settings") << "settings/Example1.qml"
                               << "settings/Example1.formatted_mac_cr.qml" << QStringList {}
                               << RunOption::OrigToCopy;
+    QTest::newRow("forWithLet")
+            << "forWithLet.qml"
+            << "forWithLet.formatted.qml" << QStringList {} << RunOption::OnCopy;
 }
 
 void TestQmlformat::testFormat()