createExportAssignment: parenthesize nested class or function expression

Fixes: #25222

Author: ajafff

src/compiler/factory.ts

@@ -4185,12 +4185,16 @@ namespace ts {
      */
     export function parenthesizeDefaultExpression(e: Expression) {
         const check = skipPartiallyEmittedExpressions(e);
-        return (check.kind === SyntaxKind.ClassExpression ||
-            check.kind === SyntaxKind.FunctionExpression ||
-            check.kind === SyntaxKind.CommaListExpression ||
-            isBinaryExpression(check) && check.operatorToken.kind === SyntaxKind.CommaToken)
-            ? createParen(e)
-            : e;
+        let needsParens = check.kind === SyntaxKind.CommaListExpression ||
+            isBinaryExpression(check) && check.operatorToken.kind === SyntaxKind.CommaToken;
+        if (!needsParens) {
+            switch (getLeftmostExpression(check, /*stopAtCallExpression*/ false).kind) {
+                case SyntaxKind.ClassExpression:
+                case SyntaxKind.FunctionExpression:
+                    needsParens = true;
+            }
+        }
+        return needsParens ? createParen(e) : e;
     }
 
     /**