{"action":"created","issue":{"url":"https://api.github.com/repos/marijnh/acorn/issues/274","labels_url":"https://api.github.com/repos/marijnh/acorn/issues/274/labels{/name}","comments_url":"https://api.github.com/repos/marijnh/acorn/issues/274/comments","events_url":"https://api.github.com/repos/marijnh/acorn/issues/274/events","html_url":"https://github.com/marijnh/acorn/issues/274","id":89320986,"number":274,"title":"Arrow function should disallow duplicate param names","user":{"login":"RReverser","id":557590,"avatar_url":"https://avatars.githubusercontent.com/u/557590?v=3","gravatar_id":"","url":"https://api.github.com/users/RReverser","html_url":"https://github.com/RReverser","followers_url":"https://api.github.com/users/RReverser/followers","following_url":"https://api.github.com/users/RReverser/following{/other_user}","gists_url":"https://api.github.com/users/RReverser/gists{/gist_id}","starred_url":"https://api.github.com/users/RReverser/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/RReverser/subscriptions","organizations_url":"https://api.github.com/users/RReverser/orgs","repos_url":"https://api.github.com/users/RReverser/repos","events_url":"https://api.github.com/users/RReverser/events{/privacy}","received_events_url":"https://api.github.com/users/RReverser/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"milestone":null,"comments":5,"created_at":"2015-06-18T15:20:45Z","updated_at":"2015-10-20T15:56:35Z","closed_at":"2015-10-19T21:15:17Z","body":"According to the spec, arrow functions should forbid presence of duplicate parameter names."},"comment":{"url":"https://api.github.com/repos/marijnh/acorn/issues/comments/149614407","html_url":"https://github.com/marijnh/acorn/issues/274#issuecomment-149614407","issue_url":"https://api.github.com/repos/marijnh/acorn/issues/274","id":149614407,"user":{"login":"nzakas","id":38546,"avatar_url":"https://avatars.githubusercontent.com/u/38546?v=3","gravatar_id":"","url":"https://api.github.com/users/nzakas","html_url":"https://github.com/nzakas","followers_url":"https://api.github.com/users/nzakas/followers","following_url":"https://api.github.com/users/nzakas/following{/other_user}","gists_url":"https://api.github.com/users/nzakas/gists{/gist_id}","starred_url":"https://api.github.com/users/nzakas/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/nzakas/subscriptions","organizations_url":"https://api.github.com/users/nzakas/orgs","repos_url":"https://api.github.com/users/nzakas/repos","events_url":"https://api.github.com/users/nzakas/events{/privacy}","received_events_url":"https://api.github.com/users/nzakas/received_events","type":"User","site_admin":false},"created_at":"2015-10-20T15:56:35Z","updated_at":"2015-10-20T15:56:35Z","body":"Ideally, yes. It can get a bit complicated since you'd need to track the scope. \r\n\r\nShift handles these early errors by doing two passes: the first pass did the parsing and the second pass does the errors (via AST traversal). They've said this resulted in better perf than doing it all in a 'single pass. "}}