From 86fce0ec0f6aaa9114b0e21b9ce8148f2c2e2971 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Thu, 2 Jan 2020 17:25:01 -0500
Subject: [PATCH] fix: check await in params when passing async arrow
 expression

---
 .../babel-parser/src/parser/expression.js     |  10 ++
 .../input.js                                  |   1 +
 .../output.json                               | 107 ++++++++++++++++++
 3 files changed, 118 insertions(+)
 create mode 100644 packages/babel-parser/test/fixtures/es2017/async-functions/async-await-as-arrow-binding-identifier/input.js
 create mode 100644 packages/babel-parser/test/fixtures/es2017/async-functions/async-await-as-arrow-binding-identifier/output.json

diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
index 1ef6fcf82f96..cd02f8cc2882 100644
--- a/packages/babel-parser/src/parser/expression.js
+++ b/packages/babel-parser/src/parser/expression.js
@@ -955,8 +955,18 @@ export default class ExpressionParser extends LValParser {
           this.match(tt.name) &&
           !this.canInsertSemicolon()
         ) {
+          const oldMaybeInArrowParameters = this.state.maybeInArrowParameters;
+          const oldYieldPos = this.state.yieldPos;
+          const oldAwaitPos = this.state.awaitPos;
+          this.state.maybeInArrowParameters = true;
+          this.state.yieldPos = -1;
+          this.state.awaitPos = -1;
           const params = [this.parseIdentifier()];
           this.expect(tt.arrow);
+          this.checkYieldAwaitInDefaultParams();
+          this.state.maybeInArrowParameters = oldMaybeInArrowParameters;
+          this.state.yieldPos = oldYieldPos;
+          this.state.awaitPos = oldAwaitPos;
           // let foo = async bar => {};
           this.parseArrowExpression(node, params, true);
           return node;
diff --git a/packages/babel-parser/test/fixtures/es2017/async-functions/async-await-as-arrow-binding-identifier/input.js b/packages/babel-parser/test/fixtures/es2017/async-functions/async-await-as-arrow-binding-identifier/input.js
new file mode 100644
index 000000000000..769cb1594534
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2017/async-functions/async-await-as-arrow-binding-identifier/input.js
@@ -0,0 +1 @@
+async await => {}
diff --git a/packages/babel-parser/test/fixtures/es2017/async-functions/async-await-as-arrow-binding-identifier/output.json b/packages/babel-parser/test/fixtures/es2017/async-functions/async-await-as-arrow-binding-identifier/output.json
new file mode 100644
index 000000000000..b264aa447eeb
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2017/async-functions/async-await-as-arrow-binding-identifier/output.json
@@ -0,0 +1,107 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 17,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 17
+    }
+  },
+  "errors": [
+    "SyntaxError: Await cannot be used as name inside an async function (1:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 17,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 17
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 17,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 17
+          }
+        },
+        "expression": {
+          "type": "ArrowFunctionExpression",
+          "start": 0,
+          "end": 17,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 17
+            }
+          },
+          "id": null,
+          "generator": false,
+          "async": true,
+          "params": [
+            {
+              "type": "Identifier",
+              "start": 6,
+              "end": 11,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 6
+                },
+                "end": {
+                  "line": 1,
+                  "column": 11
+                },
+                "identifierName": "await"
+              },
+              "name": "await"
+            }
+          ],
+          "body": {
+            "type": "BlockStatement",
+            "start": 15,
+            "end": 17,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 15
+              },
+              "end": {
+                "line": 1,
+                "column": 17
+              }
+            },
+            "body": [],
+            "directives": []
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
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