fix(es/compat): Hoist arguments in object method while lowering async functions (#10167)

**Related issue:** - Closes #10149

Author: magic-akari

.changeset/foo-bar.md

@@ -0,0 +1,6 @@
+---
+swc_ecma_compat_es2017: patch
+swc_core: patch
+---
+
+fix(es/compat): Hoist arguments in object method while lowering async functions

crates/swc/tests/fixture/issues-10xxx/10149/1/input/.swcrc

@@ -0,0 +1,11 @@
+{
+ "jsc": {
+ "parser": {
+ "syntax": "ecmascript",
+ "jsx": false
+ },
+ "target": "es5"
+ },
+ "minify": false,
+ "isModule": true
+}

crates/swc/tests/fixture/issues-10xxx/10149/1/input/index.ts

@@ -0,0 +1,15 @@
+var foo = {
+ async bar({ name }) {
+ console.log("arguments.length", arguments.length);
+ },
+};
+
+class Foo {
+ async bar({ name }) {
+ console.log("arguments.length", arguments.length);
+ }
+}
+
+async function bar({ name }) {
+ console.log("arguments.length", arguments.length);
+}

crates/swc/tests/fixture/issues-10xxx/10149/1/output/index.ts

@@ -0,0 +1,59 @@
+var _async_to_generator = require("@swc/helpers/_/_async_to_generator");
+var _class_call_check = require("@swc/helpers/_/_class_call_check");
+var _create_class = require("@swc/helpers/_/_create_class");
+var _ts_generator = require("@swc/helpers/_/_ts_generator");
+var foo = {
+ bar: function bar(param) {
+ var name = param.name;
+ var _arguments = arguments;
+ return _async_to_generator._(function() {
+ return _ts_generator._(this, function(_state) {
+ console.log("arguments.length", _arguments.length);
+ return [
+ 2
+ ];
+ });
+ })();
+ }
+};
+var Foo = /*#__PURE__*/ function() {
+ "use strict";
+ function Foo() {
+ _class_call_check._(this, Foo);
+ }
+ _create_class._(Foo, [
+ {
+ key: "bar",
+ value: function bar(param) {
+ var name = param.name;
+ var _arguments = arguments;
+ return _async_to_generator._(function() {
+ return _ts_generator._(this, function(_state) {
+ console.log("arguments.length", _arguments.length);
+ return [
+ 2
+ ];
+ });
+ })();
+ }
+ }
+ ]);
+ return Foo;
+}();
+function bar(_) {
+ return _bar.apply(this, arguments);
+}
+function _bar() {
+ _bar = _async_to_generator._(function(param) {
+ var name;
+ var _arguments = arguments;
+ return _ts_generator._(this, function(_state) {
+ name = param.name;
+ console.log("arguments.length", _arguments.length);
+ return [
+ 2
+ ];
+ });
+ });
+ return _bar.apply(this, arguments);
+}

crates/swc/tests/fixture/issues-10xxx/10149/2/input/.swcrc

@@ -0,0 +1,11 @@
+{
+ "jsc": {
+ "parser": {
+ "syntax": "ecmascript",
+ "jsx": false
+ },
+ "target": "es2016"
+ },
+ "minify": false,
+ "isModule": true
+}

crates/swc/tests/fixture/issues-10xxx/10149/2/input/index.ts

@@ -0,0 +1,15 @@
+var foo = {
+ async bar({ name }) {
+ console.log("arguments.length", arguments.length);
+ },
+};
+
+class Foo {
+ async bar({ name }) {
+ console.log("arguments.length", arguments.length);
+ }
+}
+
+async function bar({ name }) {
+ console.log("arguments.length", arguments.length);
+}

crates/swc/tests/fixture/issues-10xxx/10149/2/output/index.ts

@@ -0,0 +1,26 @@
+var _async_to_generator = require("@swc/helpers/_/_async_to_generator");
+var foo = {
+ bar ({ name }) {
+ var _arguments = arguments;
+ return _async_to_generator._(function*() {
+ console.log("arguments.length", _arguments.length);
+ })();
+ }
+};
+class Foo {
+ bar({ name }) {
+ var _arguments = arguments;
+ return _async_to_generator._(function*() {
+ console.log("arguments.length", _arguments.length);
+ })();
+ }
+}
+function bar(_) {
+ return _bar.apply(this, arguments);
+}
+function _bar() {
+ _bar = _async_to_generator._(function*({ name }) {
+ console.log("arguments.length", arguments.length);
+ });
+ return _bar.apply(this, arguments);
+}

crates/swc/tests/fixture/issues-1xxx/1575/case1/output/index.js

@@ -3,14 +3,15 @@ var _ts_generator = require("@swc/helpers/_/_ts_generator");
 Vue.component("test", {
  methods: {
  onSend: function onSend() {
+ var _this = this;
  return _async_to_generator._(function() {
  return _ts_generator._(this, function(_state) {
- if (this.msg === "") {}
+ if (_this.msg === "") {}
  return [
  2
  ];
  });
- }).apply(this);
+ })();
  }
  }
 });

crates/swc/tests/fixture/issues-1xxx/1575/case2/output/index.js

@@ -3,14 +3,15 @@ var _ts_generator = require("@swc/helpers/_/_ts_generator");
 var obj = {
  foo: 5,
  method: function method() {
+ var _this = this;
  return _async_to_generator._(function() {
  return _ts_generator._(this, function(_state) {
  return [
  2,
- this.foo
+ _this.foo
  ];
  });
- }).apply(this);
+ })();
  }
 };
 obj.method().then(function(v) {

crates/swc_ecma_compat_es2017/src/async_to_generator.rs

@@ -6,7 +6,7 @@ use swc_ecma_ast::*;
 use swc_ecma_transforms_base::{helper, helper_expr, perf::Check};
 use swc_ecma_transforms_macros::fast_path;
 use swc_ecma_utils::{
- contains_this_expr, find_pat_ids,
+ find_pat_ids,
  function::{init_this, FnEnvHoister, FnWrapperResult, FunctionWrapper},
  prepend_stmt, private_ident, quote_ident, ExprFactory, Remapper, StmtLike,
 };
@@ -339,54 +339,52 @@ impl VisitMut for Actual {
  return;
  }
 
- let is_this_used = contains_this_expr(&prop.function.body);
-
- let original_fn_params = prop.function.params.take();
-
- let prop_method_span = prop.function.span;
- let prop_method_body_span = if let Some(body) = &prop.function.body {
- body.span
- } else {
- DUMMY_SP
+ let Function {
+ span,
+ params,
+ body: Some(body),
+ ..
+ } = &mut *prop.function
+ else {
+ return;
  };
- prop.function.span = prop_method_body_span;
 
- let fn_ref = make_fn_ref(
- Function {
- params: Vec::new(),
- ..*prop.function.take()
- }
- .into(),
- );
+ let span = *span;
+ let params = params.take();
+ let mut visitor = FnEnvHoister::new(self.unresolved_ctxt);
+ body.visit_mut_with(&mut visitor);
 
- let fn_ref = if is_this_used {
- fn_ref.apply(DUMMY_SP, ThisExpr { span: DUMMY_SP }.into(), Vec::new())
- } else {
- CallExpr {
- span: DUMMY_SP,
- callee: fn_ref.as_callee(),
- args: Vec::new(),
- ..Default::default()
- }
- .into()
- };
+ let expr = make_fn_ref(FnExpr {
+ ident: None,
+ function: prop.function.take(),
+ });
 
  prop.function = Function {
- params: original_fn_params,
- span: prop_method_span,
- is_async: false,
- is_generator: false,
+ span,
+ params,
  body: Some(BlockStmt {
- span: DUMMY_SP,
- stmts: vec![Stmt::Return(ReturnStmt {
- span: DUMMY_SP,
- arg: Some(Box::new(fn_ref)),
- })],
+ stmts: visitor
+ .to_stmt()
+ .into_iter()
+ .chain(iter::once(
+ ReturnStmt {
+ span: DUMMY_SP,
+ arg: Some(
+ CallExpr {
+ callee: expr.as_callee(),
+ ..Default::default()
+ }
+ .into(),
+ ),
+ }
+ .into(),
+ ))
+ .collect(),
  ..Default::default()
  }),
  ..Default::default()
  }
- .into()
+ .into();
  }
 
  fn visit_mut_stmts(&mut self, _n: &mut Vec<Stmt>) {}