fix(51245): Class with parameter decorator in arrow function causes "convert to default export" refactoring failure

src/services/formatting/rules.ts

@@ -725,17 +725,7 @@ namespace ts.formatting {
     }
 
     function isEndOfDecoratorContextOnSameLine(context: FormattingContext): boolean {
-        return context.TokensAreOnSameLine() &&
-            hasDecorators(context.contextNode) &&
-            nodeIsInDecoratorContext(context.currentTokenParent) &&
-            !nodeIsInDecoratorContext(context.nextTokenParent);
-    }
-
-    function nodeIsInDecoratorContext(node: Node): boolean {
-        while (isExpressionNode(node)) {
-            node = node.parent;
-        }
-        return node.kind === SyntaxKind.Decorator;
+        return context.TokensAreOnSameLine() && hasDecorators(context.contextNode) && isDecorator(context.currentTokenParent);
     }
 
     function isStartOfVariableDeclarationList(context: FormattingContext): boolean {

tests/cases/fourslash/refactorConvertExport_namedToDefault2.ts

@@ -0,0 +1,23 @@
+/// <reference path='fourslash.ts' />
+
+// @Filename: /a.ts
+/////*a*/export const f = () => {
+////    return class C {
+////        constructor(@Foo() param: any) { }
+////    }
+////}/*b*/
+////function Foo(...args: any[]): any {}
+
+goTo.select("a", "b");
+edit.applyRefactor({
+    refactorName: "Convert export",
+    actionName: "Convert named export to default export",
+    actionDescription: "Convert named export to default export",
+    newContent:
+`export default () => {
+    return class C {
+        constructor(@Foo() param: any) { }
+    }
+}
+function Foo(...args: any[]): any {}`,
+});