Microsoft/TypeScript

Indexing/element access on `super` avoids instance property checks

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#55,899 opened on Sep 28, 2023

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 (1 comment) (0 reactions) (1 assignee)TypeScript (6,726 forks)batch import
BugDomain: classesEffort: CasualFix AvailableHelp WantedRescheduled

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Description

Discovered in conversation at https://github.com/microsoft/TypeScript/pull/55892#discussion_r1339658106

class C {
    yadda = () => {};
}

class D extends C {
    badda() {
        super["yadda"]();
    }
}

new D().badda()

Currently there is no error for this code; however, if you switched it to a property access, you'd get the error introduced at https://github.com/microsoft/TypeScript/pull/54056.

class C {
    yadda = () => {};
}

class D extends C {
    badda() {
        super.yadda(); // ❌ errors, as expected
    }
}

Contributor guide

Research direction
In the TypeScript checker, locate where property access on super (e.g., super.prop) is handled and where element access (super['prop']) is handled. The fix likely involves ensuring that element access on super also triggers the instance property check (introduced in PR #54056). Trace the code path from the checker's handling of SuperPropertyAccessExpression and SuperElementAccessExpression.
Tech stack
typescript
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitTypeScript basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65