fix: Edge cases for async functions and noNewArrow assumption

packages/babel-helper-wrap-function/src/index.ts

@@ -9,6 +9,7 @@ import {
   isFunctionDeclaration,
   isRestElement,
   returnStatement,
+  isCallExpression,
 } from "@babel/types";
 import type * as t from "@babel/types";
 
@@ -89,37 +90,50 @@ function classOrObjectMethod(
 }
 
 function plainFunction(
-  path: NodePath<Exclude<t.Function, t.Method>>,
+  inPath: NodePath<Exclude<t.Function, t.Method>>,
   callId: t.Expression,
   noNewArrows: boolean,
   ignoreFunctionLength: boolean,
 ) {
-  let functionId = null;
+  let path: NodePath<
+    | t.FunctionDeclaration
+    | t.FunctionExpression
+    | t.CallExpression
+    | t.ArrowFunctionExpression
+  > = inPath;
   let node;
-  if (path.isArrowFunctionExpression()) {
+  let functionId = null;
+  const nodeParams = inPath.node.params;
+
+  if (inPath.isArrowFunctionExpression()) {
     if (process.env.BABEL_8_BREAKING) {
-      path = path.arrowFunctionToExpression({ noNewArrows });
+      path = inPath.arrowFunctionToExpression({ noNewArrows });
     } else {
       // arrowFunctionToExpression returns undefined in @babel/traverse < 7.18.10
-      path = path.arrowFunctionToExpression({ noNewArrows }) ?? path;
+      path = inPath.arrowFunctionToExpression({ noNewArrows }) ?? inPath;
     }
-    node = path.node as t.FunctionDeclaration | t.FunctionExpression;
+    node = path.node as
+      | t.FunctionDeclaration
+      | t.FunctionExpression
+      | t.CallExpression;
   } else {
     node = path.node as t.FunctionDeclaration | t.FunctionExpression;
   }
 
   const isDeclaration = isFunctionDeclaration(node);
 
-  functionId = node.id;
-  node.id = null;
-  node.type = "FunctionExpression";
-
-  const built = callExpression(callId, [
-    node as Exclude<typeof node, t.FunctionDeclaration>,
-  ]);
+  let built = node;
+  if (!isCallExpression(node)) {
+    functionId = node.id;
+    node.id = null;
+    node.type = "FunctionExpression";
+    built = callExpression(callId, [
+      node as Exclude<typeof node, t.FunctionDeclaration>,
+    ]);
+  }
 
   const params: t.Identifier[] = [];
-  for (const param of node.params) {
+  for (const param of nodeParams) {
     if (isAssignmentPattern(param) || isRestElement(param)) {
       break;
     }

packages/babel-preset-env/test/fixtures/plugins-integration/issue-15170/exec.js

@@ -0,0 +1,3 @@
+expect(() => {
+  x = async x => 0 ;
+}).not.toThrow();

packages/babel-preset-env/test/fixtures/plugins-integration/issue-15170/input.js

@@ -0,0 +1 @@
+x = async x => 0 ;

packages/babel-preset-env/test/fixtures/plugins-integration/issue-15170/options.json

@@ -0,0 +1,4 @@
+{
+  "presets": ["env"],
+  "assumptions": { "noNewArrows": false }
+}

packages/babel-preset-env/test/fixtures/plugins-integration/issue-15170/output.js

@@ -0,0 +1,42 @@
+var _this = this;
+x = /*#__PURE__*/function () {
+  var _ref = function (_x) {
+    var _marked = /*#__PURE__*/babelHelpers.regeneratorRuntime().mark(x);
+    function x(_x2) {
+      var _args = arguments;
+      return babelHelpers.regeneratorRuntime().wrap(function x$(_context) {
+        while (1) {
+          switch (_context.prev = _context.next) {
+            case 0:
+              return _context.delegateYield(_x.apply(this, _args), "t0", 1);
+            case 1:
+              return _context.abrupt("return", _context.t0);
+            case 2:
+            case "end":
+              return _context.stop();
+          }
+        }
+      }, _marked, this);
+    }
+    x.toString = function () {
+      return _x.toString();
+    };
+    return x;
+  }( /*#__PURE__*/babelHelpers.regeneratorRuntime().mark(function _callee(x) {
+    return babelHelpers.regeneratorRuntime().wrap(function _callee$(_context2) {
+      while (1) {
+        switch (_context2.prev = _context2.next) {
+          case 0:
+            babelHelpers.newArrowCheck(this, _this);
+            return _context2.abrupt("return", 0);
+          case 2:
+          case "end":
+            return _context2.stop();
+        }
+      }
+    }, _callee, this);
+  }));
+  return function (_x3) {
+    return _ref.apply(this, arguments);
+  };
+}().bind(this);

packages/babel-traverse/src/path/conversion.ts

@@ -158,7 +158,9 @@ export function arrowFunctionToExpression(
     specCompliant?: boolean | void;
     noNewArrows?: boolean;
   } = {},
-): NodePath<Exclude<t.Function, t.Method | t.ArrowFunctionExpression>> {
+): NodePath<
+  Exclude<t.Function, t.Method | t.ArrowFunctionExpression> | t.CallExpression
+> {
   if (!this.isArrowFunctionExpression()) {
     throw (this as NodePath).buildCodeFrameError(
       "Cannot convert non-arrow function to a function expression.",