minifier: function declaration in switch statement can result in invalid program

[hyp3rflow]

Describe the bug

Function can only be declared at top level of the program or inside the block in strict mode.
Interestingly, marking function as a generator or normal function makes program valid.

Input code

"use strict";
const k = (() => {
  let x = 1; 
  switch (x) {
    case x: async function x() {}
  } 
  return x;
})();

Config

{
  "jsc": {
    "parser": {
      "syntax": "ecmascript",
      "jsx": false
    },
    "target": "es2022",
    "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": false
    }
  },
  "module": {
    "type": "commonjs"
  },
  "minify": false,
  "isModule": false
}

Playground link (or link to the minimal reproduction)

https://play.swc.rs/?version=1.5.6-nightly-20240511.1&code=H4sIAAAAAAAAAx2MwQqAIBBE737F0EmPXRP7l1iMpDBwVzLCf2%2FrOG9m3lA5gqUkksEbOjMLdgRY6xBmPAY4oqApGj008ZWENtjm%2FhKgRQ1twsJ3Jqw1k6Qzo6ng6bro36tEqUWhN91Z518M6BU4dgAAAA%3D%3D&config=H4sIAAAAAAAAA32UO5LbMAyG%2Bz2FR3WKjMscIF3OwKFJUKZDEhoC9Fqz47sHeviRNeROwocfIAEQXx%2B7XXci1%2F3afcmn%2FAy2EtT7v1hoLGwvYunAZUuuxoG7Hzd6ogkFmwhm03UhHdvaA88q2v%2Fc71dFlxAJborVlmOJYXzO6TAPFYiebGKVkC1DYfpfv7KKnxPg2p7tB8QEtrwhxpKJhaGHqgV2mJIdCMzZViXKdFJbI6GWYoKNwZuh4qDy4iNHLJLzlXqw3jj0oKBYwXE8gyaTXCIrJNdT7jNjD4fW93Ofv6nhbFOzrOSEy9wSOa0S9YiR2IRWtBIucKMGC1yL%2B10Zg6nArZZX3Qlj2ejJXwCpQLJExWbQ4s4eQeZpSx3eKmMJMrI8KlzmW7tlgV6KamIMSmWnykDlqHWzgm8Opso67Tgr3igfRQ8GQpBZUULTZ2R31JLyOAAGBUh%2FbdCmagHm%2Fgo3%2BPQg3uDfckvWB2z1yJaP25TGfMD0JkEGPqJ%2F4yCtYNzGVbbEZdjmrXiQ0QCvujSawesSkAfAaNK8L19mQ56HRDR9wsNjTawO1%2Fsezrb0j%2Fe%2BrOKP1aHL6NsM1yU%2F9XdazdKOjOVE3cPztorvp%2B8i%2FbnJl9jXf3MIldo2BgAA

SWC Info output

No response

Expected behavior

"use strict";
let k = (()=>{
    if (1 === x1) { async function x1() {} } // <- block here!
    return 1;
})();

Actual behavior

"use strict";
let k = (()=>{
    if (1 === x1) async function x1() {}
    return 1;
})();

Version

1.5.6-nightly-20240511.1

Additional context

This may not be worth fixing because using function x meaningly will break inlining or make block on if statement.