From 2daeda78401ab2b850ed472d8c04f44daf5e2746 Mon Sep 17 00:00:00 2001
From: Devon Govett <devongovett@gmail.com>
Date: Sun, 3 Jan 2021 19:51:14 -0500
Subject: [PATCH] Parenthesize unary expressions of prefix operators

---
 src/astring.js                          | 8 +++-----
 src/tests/fixtures/syntax/precedence.js | 7 ++++---
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/astring.js b/src/astring.js
index 2d1e6717..ff5b62cb 100644
--- a/src/astring.js
+++ b/src/astring.js
@@ -830,15 +830,13 @@ export const baseGenerator = {
   UnaryExpression(node, state) {
     if (node.prefix) {
       state.write(node.operator)
-      if (
-        node.operator.length > 1 ||
-        node.argument.type === 'UnaryExpression'
-      ) {
+      if (node.operator.length > 1) {
         state.write(' ')
       }
       if (
         EXPRESSIONS_PRECEDENCE[node.argument.type] <
-        EXPRESSIONS_PRECEDENCE.UnaryExpression
+          EXPRESSIONS_PRECEDENCE.UnaryExpression ||
+        node.argument.prefix
       ) {
         state.write('(')
         this[node.argument.type](node.argument, state)
diff --git a/src/tests/fixtures/syntax/precedence.js b/src/tests/fixtures/syntax/precedence.js
index 2d6d7fbd..c2d9eb9d 100644
--- a/src/tests/fixtures/syntax/precedence.js
+++ b/src/tests/fixtures/syntax/precedence.js
@@ -14,7 +14,7 @@ a = !false;
 b = !x instanceof Number;
 c = !(x instanceof Number);
 d = typeof a === 'boolean';
-e = ! typeof a === 'boolean';
+e = !(typeof a) === 'boolean';
 f = !(typeof a === 'boolean');
 a = (1.1).toString();
 b = new A().toString();
@@ -29,5 +29,6 @@ e = 2 ** +3;
 f = a + (b = 3);
 g = 1 && (() => {});
 g = (() => {}) && 1;
-g = (1, + +2);
-g = (1, + +(2 + 3));
+g = (1, +(+2));
+g = (1, +(+(2 + 3)));
+a = -(--i);