bug: nullish coalescing with function invokation is not properly compiled

[layershifter]

Describe the bug

The problem appears on ArrowFunctionExpression that don't have BlockStatement:

const foo = () => baz() ?? qux;

SWC result 🟥

var _baz; // <<<< variable is in a module scope 💣 
const foo = ()=>(_baz = baz()) !== null && _baz !== void 0 ? _baz : qux;

Babel 🟢

const foo = () => {
  var _baz;
  return (_baz = baz()) !== null && _baz !== void 0 ? _baz : qux;
};

TS 🟢

const foo = () => {
    var _baz;
    return (_baz = baz()) !== null && _baz !== void 0 ? _baz : qux;
};

Input code

const foo = () => baz() ?? qux;

Config

{
  "$schema": "https://json.schemastore.org/swcrc",
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": false,
      "dynamicImport": true
    },
    "transform": {
      "react": {
        "runtime": "automatic"
      }
    },
    "baseUrl": "./",
    "target": "es2019",
    "keepClassNames": true,
    "minify": {
      "compress": false
    }
  },
  "isModule": true,
  "module": {
    "type": "es6"
  },
  "minify": false
}

Playground link

https://play.swc.rs/?version=1.3.86&code=H4sIAAAAAAAAA0vOzysuUUjLz1ewVdDQVLC1U0hKrAIy7O0VCksrrAEQVEH%2BHwAAAA%3D%3D&config=H4sIAAAAAAAAA1WQTU7EMAyF93OKymKJWmCBxGxZsYAdBzAZdyZDnUS2K6hGvTtJ%2F1R28ffs9xzfDlUFd%2BouxAjHCi5mSY9Nc9UY6hmrRaE6yrnRHycO7svIVV1uv%2BVnLhKKkmx1JjoEw99iaEMideKTTYOTalqkFjuljZ2GgOzdG6collWTniZtnFvABIO2UXifI4TOdqCgPphnKtnYW2Q072CRx3%2BOX6j0KV3prBtYY1DOVCyB9Onh8WXl30TptUPVD2TSZcFFYx98O%2Bz3cpGTkOr6zcOaPmWD1%2Fd46jva2QCvZDlqOdy8xjNsg1vS7Dr%2BAd6pGL%2B%2FAQAA

SWC Info output

N/A

Expected behavior

As in Babel & TS, the variable should be created in a scope of function instead of module scope i.e. the following result:

const foo = () => {
    var _baz;
    return (_baz = baz()) !== null && _baz !== void 0 ? _baz : qux;
};

Actual behavior

var _baz; // <<<< variable is in a module scope 💣 
const foo = ()=>(_baz = baz()) !== null && _baz !== void 0 ? _baz : qux;

The variable will be created in a module scope, this creates memory leaks if baz() returns an object that references other objects.

Note: the following snippet is compiled properly:

const foo = () => { return baz() ?? qux; }
// ⬇️⬇️⬇️
const foo = ()=>{
    var _baz;
    return (_baz = baz()) !== null && _baz !== void 0 ? _baz : qux;
};

Version

1.3.86

Additional context

No response

[swc-bot]

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