From 7cbe0f9ef347fd0d4c43b51792cc3fa1847ce062 Mon Sep 17 00:00:00 2001
From: Marijn Haverbeke <marijn@haverbeke.nl>
Date: Tue, 4 May 2021 12:12:30 +0200
Subject: [PATCH] Add explicit exception for 'async of' not starting arrow in
 for init context

FIX: Fix issue where the library couldn't parse 'for (async of ...)'.

Closes #1031
---
 acorn/src/expression.js  | 7 +++++--
 acorn/src/state.js       | 1 +
 test/tests-asyncawait.js | 2 ++
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/acorn/src/expression.js b/acorn/src/expression.js
index 0d1b3fa8a..9ee0951f9 100644
--- a/acorn/src/expression.js
+++ b/acorn/src/expression.js
@@ -124,8 +124,10 @@ pp.parseMaybeAssign = function(noIn, refDestructuringErrors, afterLeftParse) {
   }
 
   let startPos = this.start, startLoc = this.startLoc
-  if (this.type === tt.parenL || this.type === tt.name)
+  if (this.type === tt.parenL || this.type === tt.name) {
     this.potentialArrowAt = this.start
+    this.forbidAsyncOfArrow = !!noIn
+  }
   let left = this.parseMaybeConditional(noIn, refDestructuringErrors)
   if (afterLeftParse) left = afterLeftParse.call(this, left, startPos, startLoc)
   if (this.type.isAssign) {
@@ -414,7 +416,8 @@ pp.parseExprAtom = function(refDestructuringErrors) {
     if (canBeArrow && !this.canInsertSemicolon()) {
       if (this.eat(tt.arrow))
         return this.parseArrowExpression(this.startNodeAt(startPos, startLoc), [id], false)
-      if (this.options.ecmaVersion >= 8 && id.name === "async" && this.type === tt.name && !containsEsc) {
+      if (this.options.ecmaVersion >= 8 && id.name === "async" && this.type === tt.name && !containsEsc &&
+          (!this.forbidAsyncOfArrow || this.value !== "of" || this.containsEsc)) {
         id = this.parseIdent(false)
         if (this.canInsertSemicolon() || !this.eat(tt.arrow))
           this.unexpected()
diff --git a/acorn/src/state.js b/acorn/src/state.js
index 6bfa56298..8545ce568 100644
--- a/acorn/src/state.js
+++ b/acorn/src/state.js
@@ -65,6 +65,7 @@ export class Parser {
 
     // Used to signify the start of a potential arrow function
     this.potentialArrowAt = -1
+    this.forbidAsyncOfArrow = false
 
     // Positions to delayed-check that yield/await does not exist in default parameters.
     this.yieldPos = this.awaitPos = this.awaitIdentPos = 0
diff --git a/test/tests-asyncawait.js b/test/tests-asyncawait.js
index 7b0f4107c..6cbbed757 100644
--- a/test/tests-asyncawait.js
+++ b/test/tests-asyncawait.js
@@ -3522,6 +3522,8 @@ test(
 
 test("({ async delete() {} })", {}, {ecmaVersion: 8})
 
+test("for (async of []) {}", {}, {ecmaVersion: 8})
+
 testFail("abc: async function a() {}", "Unexpected token (1:5)", {ecmaVersion: 8})
 
 testFail("(async() => { await 4 ** 2 })()", "Unexpected token (1:22)", {ecmaVersion: 8})