Block-scoping bug

[seansonb]

I have the following script:

let res = [];

let a = 2;
res.push(a === 2);

{
let b = 1;
}
res.push(typeof b === "undefined");

if(true) {
let b = 0;
}
res.push(typeof b === "undefined");

for(let b = 0; b < 10; b++) {
}
res.push(typeof b === "undefined");

function test() {
let b = 7;
}
res.push(typeof b === "undefined");

console.log(res);

I expect this to evaluate to [true, true, true, true, true], but am getting [true, false, false, false, false] because the first block-scoped variable b is not renamed or prepended with an underscore. Here's the link to the swc-playground transpilation. In babel the transpilation looks like the following with all block-scoped let assignments prepended with underscores and incremented:

var res = [];
var a = 2;
res.push(a === 2);
{
var _b = 1;
}
res.push(typeof b === "undefined");

if (true) {
var _b2 = 0;
}

res.push(typeof b === "undefined");

for (var _b3 = 0; _b3 < 10; _b3++) {}

res.push(typeof b === "undefined");

function test() {
var b = 7;
}

res.push(typeof b === "undefined");
res;

Config:

{
"jsc": {
"target": "es5",
"parser": {
"syntax": "ecmascript"
}
}
"module": {
"type": "commonjs",
"strict": true
"strictMode": true
},
"sourceMaps": true
}

[magic-akari]

related issues:

• Variable being renamed unnecessarily is breaking code #3213
• resolver should use different mark for top level bindings and unresolved identifiers #2956

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.