`function l([w,w]) { }`: should it actually parse?
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Description
Hello
If I have understood the spec correctly, only non-strict mode functions with no array-, object-, or assignment-pattern in their parameter list are allowed to have duplicate parameters. So none are valid below:
function l(w,[w]) { }
function l(w,w=12) { }
function l(w,{w}) { }
function l([w,w]) { }
function l({w,w}) { }
function l([w], w) { }
function l({w}, w) { }
still they actually parse smoothly in esprima. I'm not a great spec grokker though, so I would be glad to know whether I've been wrong with the claims above. Thanks a lot in advance!
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First steps
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Research direction
Start by comparing the seven JavaScript function declarations with the ECMAScript duplicate-parameter rules and checking Esprima's current parsing behavior. Confirm which declarations should be rejected, then add or update parser coverage so the reported cases consistently match the specification.
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Assessment
- Tech stack
- javascript, typescript
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100