Minifier produces incorrect code when template literals are used

[abdulsattar]

Describe the bug

The minifier is reusing a variable defined inside of a function when it's not safe to do so. This changes the runtime behavior as demonstrated in this repro.

Input code

let a = 0;
function f(arr) {
  let b = a;
  return `${arr.map((child) => {
  a = b + "str";
})}`;
}

function g(arr) {
    return f(arr);
}
globalThis.g = g;
g([1,2,3])
console.log(a);

Config

{
  "jsc": {
    "parser": {
      "syntax": "ecmascript",
      "jsx": false
    },
    "target": "es2015",
    "loose": false,
    "minify": {
      "compress": {
        "arguments": false,
        "arrows": true,
        "booleans": true,
        "booleans_as_integers": false,
        "collapse_vars": true,
        "comparisons": true,
        "computed_props": true,
        "conditionals": true,
        "dead_code": true,
        "directives": true,
        "drop_console": false,
        "drop_debugger": true,
        "evaluate": true,
        "expression": false,
        "hoist_funs": false,
        "hoist_props": true,
        "hoist_vars": false,
        "if_return": true,
        "join_vars": true,
        "keep_classnames": false,
        "keep_fargs": true,
        "keep_fnames": false,
        "keep_infinity": false,
        "loops": true,
        "negate_iife": true,
        "properties": true,
        "reduce_funcs": false,
        "reduce_vars": false,
        "side_effects": true,
        "switches": true,
        "typeofs": true,
        "unsafe": false,
        "unsafe_arrows": false,
        "unsafe_comps": false,
        "unsafe_Function": false,
        "unsafe_math": false,
        "unsafe_symbols": false,
        "unsafe_methods": false,
        "unsafe_proto": false,
        "unsafe_regexp": false,
        "unsafe_undefined": false,
        "unused": true,
        "const_to_let": true,
        "pristine_globals": true
      },
      "mangle": {
        "toplevel": false,
        "keep_classnames": false,
        "keep_fnames": false,
        "keep_private_props": false,
        "ie8": false,
        "safari10": false
      }
    }
  },
  "module": {
    "type": "es6"
  },
  "minify": true,
  "isModule": true
}

Playground link

https://play.swc.rs/?version=1.3.84&code=H4sIAAAAAAAAA0XNTQrDIBAF4L2nGEIXSoP0ZynJKborhag1RphqUbMKuXsnLTSbgcd7fIOugoYOToqNc7Q1pAgj1zkLWBgAUm2o1opCdnXOEYbDQr186Tfndgr4FND13%2FUGGThCU2puFFvFOtBlu%2Bx3%2Bc%2F9vm07j8lovE2hSE%2BSV8zz%2B7m9tNeHYDbFktBJTIQI9QGn86FuuAAAAA%3D%3D&config=H4sIAAAAAAAAA41VwW7bMAy99ysCn3doB3QY9gG77RsExaIcZbJoiJSboMi%2Fj1bsNG1oY5cg5tMjRfKRen%2Fa7Zojtc2v3bv8lY%2FBZoJ8%2BxYLnRPbk1gaaHtLbQ4DN98W9EgT5G0kqKbLFWnY5g64suj788vrzGgiIsHCmG19SMGf72O22A8ZiO5sYhWXpYfE9Jk%2FYxnfJoBzubfvESPYtIEYSyYkhg6y5rjFGO1AYEabFS%2FTTW0OhFqICSwMzgwZBxVPLnDAJDEfUQfWmRYdKFDI0HIYQaNJLKElkvSUfCrsYF%2B6rvb5CxtGG4tlJSacakvktorXAwZi40vSSngFV2pwBefifmUGbzJwyemRd8SQVnryF0AqEC1Rsj1ofusJL3paY%2FtNZkheJMtnBRd9a1km6KSoJgSvVHaqDGQOWjczuNLCVNlWu84Mr5SPggMD3otWFNf0Frg9aEH5PAB6BZD%2BWq%2Bp6gqY2xSu4NNAbMC%2FJUvWBTaf6C0f1lE693uMGwF64AO6jQPSCsZ1OMuWOA3reEkORBrg1COFKvC4BGQAGE2s%2B%2FJBGzIe4tF0Efcfa2I%2BcLnt4d6mrs773b5kHCKMENdk%2FB8jsonK3cZJ1ctkP0wv%2FNREaWXwwsvzp2dDUnlafmtSTY%2Bu3CVUNXl9Tn40H4eWl2OpWhPoz0Ksdbr8A8XlsejjBgAA

SWC Info output

No response

Expected behavior

Unminified code prints 0str while minified code prints 0strstrstr.

Actual behavior

No response

Version

1.3.85

Additional context

No response

[kdy1]

Investigation

This only occurs if minifier is invoked using transform().

[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.