Bug: Cannot read properties of undefined (reading 'at') coming from typescript-eslint

[anthonyshew]

Before You File a Bug Report Please Confirm You Have Done The Following...

• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.
• I have searched for related issues and found none that matched my issue.
• I have read the FAQ and my problem is not listed.

Issue Description

NOTE: I asked @JoshuaKGoldberg for help thinking I had something misconfigured - but he's confident this is a bug. He thinks he already has the problematic code cornered. Because of this, I won't be providing a reproduction - but I am more than happy to if it ends up being needed!

While upgrading dependencies and reconfiguring our monorepo, I ran into this stack trace coming from typescript-eslint. You'll want to click the > docs:lint on line 276 to expand the error.

Reproduction Repository Link

See NOTE above.

Repro Steps

Provided to me by Josh:

1. Clone repo (https://github.com/vercel/turbo)
2. Start a pnpm i
3. npx eslint docs/components/Authors.tsx

Versions

package	version
@typescript-eslint/eslint-plugin	^6.14.0
@typescript-eslint/parser	^6.14.0
TypeScript	5.3.3
ESLint	^8.55.0
node	18.18.2

[JoshuaKGoldberg]

Can confirm! This is the error report:

joshgoldberg ~/repos/turbo $ npx eslint docs/components/Authors.tsx

Oops! Something went wrong! :(

ESLint: 8.55.0

TypeError: Cannot read properties of undefined (reading 'at')
Occurred while linting /Users/josh/repos/turbo/docs/components/Authors.tsx:13
Rule: "@typescript-eslint/unbound-method"
    at checkMethod (/Users/josh/repos/turbo/node_modules/.pnpm/@typescript-eslint+eslint-plugin@6.14.0_@typescript-eslint+parser@6.14.0_eslint@8.55.0_typescript@4.9.5/node_modules/@typescript-eslint/eslint-plugin/dist/rules/unbound-method.js:222:48)
    at checkMethodAndReport (/Users/josh/repos/turbo/node_modules/.pnpm/@typescript-eslint+eslint-plugin@6.14.0_@typescript-eslint+parser@6.14.0_eslint@8.55.0_typescript@4.9.5/node_modules/@typescript-eslint/eslint-plugin/dist/rules/unbound-method.js:160:53)
    at MemberExpression (/Users/josh/repos/turbo/node_modules/.pnpm/@typescript-eslint+eslint-plugin@6.14.0_@typescript-eslint+parser@6.14.0_eslint@8.55.0_typescript@4.9.5/node_modules/@typescript-eslint/eslint-plugin/dist/rules/unbound-method.js:181:17)
    at ruleErrorHandler (/Users/josh/repos/turbo/node_modules/.pnpm/eslint@8.55.0/node_modules/eslint/lib/linter/linter.js:1091:28)
    at /Users/josh/repos/turbo/node_modules/.pnpm/eslint@8.55.0/node_modules/eslint/lib/linter/safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (/Users/josh/repos/turbo/node_modules/.pnpm/eslint@8.55.0/node_modules/eslint/lib/linter/safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (/Users/josh/repos/turbo/node_modules/.pnpm/eslint@8.55.0/node_modules/eslint/lib/linter/node-event-generator.js:297:26)
    at NodeEventGenerator.applySelectors (/Users/josh/repos/turbo/node_modules/.pnpm/eslint@8.55.0/node_modules/eslint/lib/linter/node-event-generator.js:326:22)
    at NodeEventGenerator.enterNode (/Users/josh/repos/turbo/node_modules/.pnpm/eslint@8.55.0/node_modules/eslint/lib/linter/node-event-generator.js:340:14)

Coming from:

typescript-eslint/packages/eslint-plugin/src/rules/unbound-method.ts

Line 276 in a54a60b

const firstParam = decl.parameters.at(0);

Logging just before the crash shows:

• decl.getSourceFile().fileName: .../turbo/node_modules/.pnpm/typescript@5.3.3/node_modules/typescript/lib/lib.es5.d.ts
• ts.SyntaxKind[decl.kind]: "MethodDeclaration"
• decl.getText(): length: number

Very interesting that decl.parameters is undefined. The ts.MethodDeclaration type extends from SignatureDeclarationBase, which has a required readonly parameters: NodeArray<ParameterDeclaration>.

[JoshuaKGoldberg]

Aha! It's a versioning issue. I:

1. added "typescript": "5.3.3" in package.json's "overrides"
2. ran pnpm install
3. re-ran npx eslint docs/components/*

No crash.

Interesting that our tooling didn't report any complaint about a TypeScript version mismatch... I'm thinking it probably should.

[anthonyshew]

0% surprised that this was on my end. 😄 Yes, definitely would have loved a warning or error with some help there. I was savvy enough to adjust our TS verison in the root thinking it might have been resolving there but wasn't smart enough to dedupe all of them.

I'm unblocked! Feel free to close - unless you want something to track version mismatch warning, of course!

Thanks for the prompt help, @JoshuaKGoldberg !

[bradzacher]

@JoshuaKGoldberg

The reason there was no error was because we are supposed to support 4.7
This shouldn't crash - so it's still a bug in our tooling.

[Josh-Cena]

I haven't seen this error again and this issue doesn't provide an easy way to reproduce. Assuming this is not relevant anymore