What code were you trying to parse?

I try to lint the following code:

asyncsomething(@Arg(){ email}:SomeInput):Promise<boolean>{}

The linting crashes with the stack trace listed under "What actually happened?".

Changing the code to:

asyncsomething(@Arg()input:SomeInput):Promise<boolean>{}

makes the rule run fine.

I created a repo for easier reproduction:https://github.com/rfermann/args-decorator-parser-error.

What did you expect to happen?
I expect to not get aTypeError during linting

What actually happened?
I got aTypeError during linting:

eslint index.ts

TypeError: Cannot read property 'type' of undefined
at isForInRef (C:\Users\parser-issue\node_modules\eslint\lib\rules\no-unused-vars.js:434:24)
at variable.references.some.ref (C:\Users\parser-issue\node_modules\eslint\lib\rules\no-unused-vars.js:471:21)
at Array.some ()
at isUsedVariable (C:\Users\parser-issue\node_modules\eslint\lib\rules\no-unused-vars.js:470:40)
at collectUnusedVariables (C:\Users\parser-issue\node_modules\eslint\lib\rules\no-unused-vars.js:582:26)
at collectUnusedVariables (C:\Users\parser-issue\node_modules\eslint\lib\rules\no-unused-vars.js:589:17)
at Program:exit (C:\Users\parser-issue\node_modules\eslint\lib\rules\no-unused-vars.js:634:36)
at listeners.(anonymous function).forEach.listener (C:\Users\parser-issue\node_modules\eslint\lib\util\safe-emitter.js:45:58)
at Array.forEach ()
at Object.emit (C:\Users\parser-issue\node_modules\eslint\lib\util\safe-emitter.js:45:38)
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