Disallow await in using declaration

packages/babel-parser/src/parse-error/standard-errors.ts

@@ -33,6 +33,8 @@ export default {
     "Can not use 'await' as identifier inside a static block.",
   AwaitExpressionFormalParameter:
     "'await' is not allowed in async function parameters.",
+  AwaitInUsingBinding:
+    "'await' is not allowed to be used as a name in 'using' declarations.",
   AwaitNotInAsyncContext:
     "'await' is only allowed within async functions and at the top levels of modules.",
   AwaitNotInAsyncFunction: "'await' is only allowed within async functions.",

packages/babel-parser/src/parser/statement.ts

@@ -471,7 +471,7 @@ export default abstract class StatementParser extends ExpressionParser {
         return this.parseTryStatement(node as Undone<N.TryStatement>);
 
       case tt._using:
-        // using [no LineTerminator here] BindingList[+Using]
+        // using [no LineTerminator here][lookahead != `await`] BindingList[+Using]
         if (
           this.hasFollowingLineBreak() ||
           this.state.containsEsc ||
@@ -1507,6 +1507,11 @@ export default abstract class StatementParser extends ExpressionParser {
     decl: Undone<N.VariableDeclarator>,
     kind: "var" | "let" | "const" | "using",
   ): void {
+    // Unlike "let" which must be handled in checkLVal, it suffices to check
+    // await here because `using` must not precede binding patterns.
+    if (kind === "using" && !this.inModule && this.match(tt._await)) {
+      this.raise(Errors.AwaitInUsingBinding, { at: this.state.startLoc });
+    }
     const id = this.parseBindingAtom();
     this.checkLVal(id, {
       in: { type: "VariableDeclarator" },

packages/babel-parser/test/fixtures/experimental/explicit-resource-management/invalid-using-binding-await/input.js

@@ -0,0 +1,6 @@
+{
+  using await = h();
+}
+{
+  using \u0061wait = h();
+}

packages/babel-parser/test/fixtures/experimental/explicit-resource-management/invalid-using-binding-await/options.json

@@ -0,0 +1,3 @@
+{
+  "sourceType": "script"
+}

packages/babel-parser/test/fixtures/experimental/explicit-resource-management/invalid-using-binding-await/output.json

@@ -0,0 +1,83 @@
+{
+  "type": "File",
+  "start":0,"end":54,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":6,"column":1,"index":54}},
+  "errors": [
+    "SyntaxError: 'await' is not allowed to be used as a name in 'using' declarations. (2:8)",
+    "SyntaxError: 'await' is not allowed to be used as a name in 'using' declarations. (5:8)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":54,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":6,"column":1,"index":54}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "BlockStatement",
+        "start":0,"end":24,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":3,"column":1,"index":24}},
+        "body": [
+          {
+            "type": "VariableDeclaration",
+            "start":4,"end":22,"loc":{"start":{"line":2,"column":2,"index":4},"end":{"line":2,"column":20,"index":22}},
+            "declarations": [
+              {
+                "type": "VariableDeclarator",
+                "start":10,"end":21,"loc":{"start":{"line":2,"column":8,"index":10},"end":{"line":2,"column":19,"index":21}},
+                "id": {
+                  "type": "Identifier",
+                  "start":10,"end":15,"loc":{"start":{"line":2,"column":8,"index":10},"end":{"line":2,"column":13,"index":15},"identifierName":"await"},
+                  "name": "await"
+                },
+                "init": {
+                  "type": "CallExpression",
+                  "start":18,"end":21,"loc":{"start":{"line":2,"column":16,"index":18},"end":{"line":2,"column":19,"index":21}},
+                  "callee": {
+                    "type": "Identifier",
+                    "start":18,"end":19,"loc":{"start":{"line":2,"column":16,"index":18},"end":{"line":2,"column":17,"index":19},"identifierName":"h"},
+                    "name": "h"
+                  },
+                  "arguments": []
+                }
+              }
+            ],
+            "kind": "using"
+          }
+        ],
+        "directives": []
+      },
+      {
+        "type": "BlockStatement",
+        "start":25,"end":54,"loc":{"start":{"line":4,"column":0,"index":25},"end":{"line":6,"column":1,"index":54}},
+        "body": [
+          {
+            "type": "VariableDeclaration",
+            "start":29,"end":52,"loc":{"start":{"line":5,"column":2,"index":29},"end":{"line":5,"column":25,"index":52}},
+            "declarations": [
+              {
+                "type": "VariableDeclarator",
+                "start":35,"end":51,"loc":{"start":{"line":5,"column":8,"index":35},"end":{"line":5,"column":24,"index":51}},
+                "id": {
+                  "type": "Identifier",
+                  "start":35,"end":45,"loc":{"start":{"line":5,"column":8,"index":35},"end":{"line":5,"column":18,"index":45},"identifierName":"await"},
+                  "name": "await"
+                },
+                "init": {
+                  "type": "CallExpression",
+                  "start":48,"end":51,"loc":{"start":{"line":5,"column":21,"index":48},"end":{"line":5,"column":24,"index":51}},
+                  "callee": {
+                    "type": "Identifier",
+                    "start":48,"end":49,"loc":{"start":{"line":5,"column":21,"index":48},"end":{"line":5,"column":22,"index":49},"identifierName":"h"},
+                    "name": "h"
+                  },
+                  "arguments": []
+                }
+              }
+            ],
+            "kind": "using"
+          }
+        ],
+        "directives": []
+      }
+    ],
+    "directives": []
+  }
+}