From 03e4f217bdf7f3bbeff9a96919106abde2bebd03 Mon Sep 17 00:00:00 2001
From: FancyFlame <fancyflame@163.com>
Date: Thu, 13 Apr 2023 20:54:50 +0800
Subject: [PATCH] fix TypeTuple::to_tokens may result in TypeParen

---
 src/ty.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/ty.rs b/src/ty.rs
index 9b341dafaf..9282ba4e61 100644
--- a/src/ty.rs
+++ b/src/ty.rs
@@ -1076,6 +1076,11 @@ mod printing {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             self.paren_token.surround(tokens, |tokens| {
                 self.elems.to_tokens(tokens);
+                // If we only have one argument, we need a trailing comma to
+                // distinguish TypeTuple from TypeParen.
+                if self.elems.len() == 1 && !self.elems.trailing_punct() {
+                    <Token![,]>::default().to_tokens(tokens);
+                }
             });
         }
     }