Panic from symbol rename failure

[airhorns]

Describe the bug

When upgrading to @swc/core v1.7.19 or newer, I get a new panic when compiling and minifying:

thread '<unnamed>' panicked at /Users/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/swc_ecma_transforms_base-0.145.0/src/rename/mod.rs:204:25:
internal error: entered unreachable code: ARDUINO_KW_type is already renamed to e, but it's renamed as n
stack backtrace:
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
[webpack-cli] HookWebpackError: failed to handle: internal error: entered unreachable code: ARDUINO_KW_type is already renamed to e, but it's renamed as n

Stack backtrace:
   0: _napi_register_module_v1
   1: _wasmer_vm_imported_memory32_atomic_notify
   2: <unknown>
   3: <unknown>
   4: <unknown>
    at makeWebpackError (/Users/airhorns/Code/gadget/node_modules/.pnpm/webpack@5.88.2_@swc+core@1.7.19_webpack-cli@5.1.4/node_modules/webpack/lib/HookWebpackError.js:48:9)
    at /Users/airhorns/Code/gadget/node_modules/.pnpm/webpack@5.88.2_@swc+core@1.7.19_webpack-cli@5.1.4/node_modules/webpack/lib/Compilation.js:3068:12
    at eval (eval at create (/Users/airhorns/Code/gadget/node_modules/.pnpm/tapable@2.2.0/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:68:1)
-- inner error --
Error: failed to handle: internal error: entered unreachable code: ARDUINO_KW_type is already renamed to e, but it's renamed as n

Stack backtrace:
   0: _napi_register_module_v1
   1: _wasmer_vm_imported_memory32_atomic_notify
   2: <unknown>
   3: <unknown>
   4: <unknown>
caused by plugins in Compilation.hooks.processAssets
Error: failed to handle: internal error: entered unreachable code: ARDUINO_KW_type is already renamed to e, but it's renamed as n

Stack backtrace:
   0: _napi_register_module_v1
   1: _wasmer_vm_imported_memory32_atomic_notify
   2: <unknown>
   3: <unknown>
   4: <unknown>

@swc/core v1.7.18 works just fine. I bisected to find that v1.7.19 is the first version that fails like this for me, and it fails on v1.7.22 as well.

I am struggling to figure out what file or what element is even causing this error -- it's happening when building a very large TypeScript monorepo using SWC for TypeScript transpilation and minification via webpack and swc-loader. I tried:

• running webpack with DEBUG="*" but didn't see anything useful there
• searching for that ARDUINO_KW_type symbol in my codebase (not there) and in node_modules (also not there, searched with rg --hidden --no-ignore -g 'node_modules/**' 'ARDUINO_KW_type')
• searching the internet for that symbol, couldn't find it anywhere!

I am not sure where it's coming from but if there are any other logs I can gather and share to help hunt this down please let me know. Please make some suggestions, I am happy to hunt just not quite sure how!

Input code

<unknown>

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": true,
      "decorators": true,
      "dynamicImport": true
    },
    "target": "esnext",
    "externalHelpers": true,
    "experimental": {
      "plugins": [
        ["@swc/plugin-loadable-components", {}],
        [
          "@swc/plugin-transform-imports",
          {
            "lodash": {
              "transform": "lodash/{{member}}"
            }
          }
        ]
      ]
    }
  },
  "module": {
    "type": "es6"
  }
}

Playground link (or link to the minimal reproduction)

https://play.swc.rs/?version=1.7.19&code=H4sIAAAAAAAAA0vLzwcAIWVzjAMAAAA%3D&config=H4sIAAAAAAAAA1WPSw7DIAwF9zkF8rrbdtE79BAWdSIifrKJVBTl7iUE0maH3xsz8jooBbNoeKq1PMsQkYX4nEsi2Sf8lARIOxTNJia49XaWvRrRCtVoOxpIyBOluiX3hoMNQajjLXPGmzH%2FC3VwkUnkCu4o%2BsnSVTc0JbjwXmrZDkk50qF%2FwA%2FqsvNjMPLqm4kXGrYvhlQioBQBAAA%3D

SWC Info output

Operating System:
    Platform: darwin
    Arch: arm64
    Machine Type: arm64
    Version: Darwin Kernel Version 23.6.0: Mon Jul 29 21:13:04 PDT 2024; root:xnu-10063.141.2~1/RELEASE_ARM64_T6020
    CPU: (12 cores)
        Models: Apple M2 Max

Binaries:
    Node: 22.2.0
    npm: 10.7.0
    Yarn: 1.22.22
    pnpm: 8.12.0

Relevant Packages:
    @swc/core: 1.7.19
    @swc/helpers: 0.5.12
    @swc/types: 0.1.12
    typescript: 5.6.0-beta

SWC Config:
    output: N/A
    .swcrc path: N/A

Next.js info:
    output: N/A

Expected behavior

No panic thrown, code is assembled as normal

Actual behavior

Panic is thrown

Version

1.7.19

Additional context

No response

[kdy1]

How did you invoke SWC? Minifier mangle cache is not enabled by default at now.

[kdy1]

Relevant code:

swc/crates/swc_ecma_transforms_base/src/rename/mod.rs

Lines 198 to 216 in c562cfa

	if let Some(total_map) = &mut self.total_map {
	total_map.reserve(map.len());
	for (k, v) in &map {
	match total_map.entry(k.clone()) {
	Entry::Occupied(old) => {
	unreachable!(
	"{} is already renamed to {}, but it's renamed as {}",
	k.0,
	old.get(),
	v
	);
	}
	Entry::Vacant(e) => {
	e.insert(v.clone());
	}
	}
	}
	}

total_map is Some iff get_cached returns Some

swc/crates/swc_ecma_transforms_base/src/rename/mod.rs

Lines 221 to 226 in c562cfa

	fn load_cache(&mut self) {
	if let Some(cache) = self.renamer.get_cached() {
	self.previous_cache = cache.into_owned();
	self.total_map = Some(Default::default());
	}
	}

.

[kdy1]

Fixed by #9524

[tonyabracadabra]

I've posted an issue for Next.js here. I hope you're able to replicate the issue, and that it can be resolved in an upcoming canary release. Thanks for your attention to this!

[airhorns]

@tonyabracadabra the issue has already been fixed in swc core and is in PR for next here: vercel/next.js#69605