Improve error when parameter is missing a name

Description

declare class C {
    f({ x?: number }): void;
    g(): void;
}

src/a.ts(2,10): error TS1005: ',' expected.
src/a.ts(2,20): error TS1005: ',' expected.
src/a.ts(2,21): error TS1128: Declaration or statement expected.
src/a.ts(2,22): error TS1128: Declaration or statement expected.
src/a.ts(2,28): error TS1109: Expression expected.
src/a.ts(3,8): error TS1005: ';' expected.
src/a.ts(3,14): error TS1109: Expression expected.
src/a.ts(4,1): error TS1128: Declaration or statement expected.

Contributor guide

Tech stack

typescript

Domain

tooling

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.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

mostly clear

Prerequisites

TypeScript compiler internalsError message handling

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

40

Research direction

Investigate where optional properties in destructuring parameters are currently parsed (likely in `src/compiler/parser.ts`). Look for existing error handling for similar cases, such as `property in destructuring may not be marked optional`. The actual error is a generic `',' expected` cascade; the fix likely involves adding a check in the parser or early binder to emit a specific error when a `?` appears in a destructuring parameter. Check existing error message infrastructure at `src/compiler/diagnostics.ts` for relevant error codes.