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#4383 — Static Semantics Contains missing base cases

• bug_id: 4383
• creation_ts: 2015-05-28 17:46:00 -0700
• short_desc: Static Semantics Contains missing base cases
• delta_ts: 2015-05-28 19:20:44 -0700
• product: Draft for 7th Edition
• component: Deferred from 6th edition
• version: unspecified
• rep_platform: All
• op_sys: All
• bug_status: CONFIRMED
• priority: Normal
• bug_severity: enhancement
• everconfirmed: true
• reporter: Brian Terlson
• assigned_to: Allen Wirfs-Brock
• cc: jmdyck

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• commentid: 14467
• comment_count: 0
• who: Brian Terlson
• bug_when: 2015-05-28 17:46:28 -0700

The base case for Contains is whether the parameter symbol matches the production being considered. Many static semantics (Arrow Functions, Generator Function Decls/Exprs, Func Decls/Exprs, etc) are missing this base case. It may not be a bug if no one ever calls Contains with a parameter of these productions but could probably be fixed for completeness's sake.

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• commentid: 14468
• comment_count: 1
• who: Michael Dyck
• bug_when: 2015-05-28 19:20:44 -0700

(In reply to Brian Terlson from comment #0)
> The base case for Contains is whether the parameter symbol matches the
> production being considered. Many static semantics (Arrow Functions,
> Generator Function Decls/Exprs, Func Decls/Exprs, etc) are missing this base
> case.

On the contrary, sections 14.1.4, 14.2.3, and 14.4.4 *do* cover such cases. However, they do so by returning false, which, while perhaps unintuitive, is not incomplete.

> It may not be a bug if no one ever calls Contains with a parameter of
> these productions but could probably be fixed for completeness's sake.

Indeed, I believe the right-hand argument to Contains is only ever:
SuperProperty
SuperCall
super
NewTarget or
ScriptBody
so how Contains would behave if it were passed any other symbol is (currently) irrelevant from a normative standpoint.