The `@ts-ignore` vs. `@ts-expect-error` Dilemma: Missing a Warning-Only Redundancy Check

まだ誰も着手していません。

### ⭐ Suggestion

We propose introducing a mechanism (either a new directive or a configuration option) that provides a **Warning-level diagnostic** when a type suppression comment is unused.

This feature is needed to fill the gap between the permanently silent `@ts-ignore` and the build-breaking `@ts-expect-error`. The goal is to allow active awareness of stale code without halting the CI pipeline.

Specifically, we request one of the following:

1. **A New Directive:** A directive functionally equivalent to `// @ts-expect-error`, but which emits its unused check (the equivalent of `TS2578`) as a **Warning**.
2. **A Compiler Flag:** An option to explicitly downgrade the severity of the **`TS2578: Unused '@ts-expect-error' directive`** diagnostic from **Error** to **Warning**.

### 📃 Motivating Example

For development teams managing projects with frequent dependency updates, the choice between `@ts-ignore` and `@ts-expect-error` is a risk management problem.

Current strictness dictates that a successful, external fix to a dependency's type definition must immediately break our codebase to enforce comment removal. This high-cost cleanup process often drives teams toward the permanently unsafe `@ts-ignore` to maintain CI stability.

A warning-level check removes this friction. It guarantees that temporary suppressions are *never* forgotten (like `@ts-expect-error`) while ensuring that the build process remains robust and responsive to upstream improvements (unlike `@ts-ignore`). This allows teams to prioritize cleaning up stale suppressions as a continuous maintenance task, rather than a critical, synchronous intervention.

### 💻 Use Cases

1. **What do you want to use this for?**

This feature would be used primarily for **temporary suppressions that are dependent on frequently changing external code** (such as library dependencies or rapid internal package updates), ensuring the temporary fix is never forgotten while allowing the system to tolerate the external fix being resolved.

2. **What shortcomings exist with current approaches?**

The shortcomings are the two extremes created by the current directives:

| Directive | Does It Alert When Unused? | Unused Diagnostic Output | Workflow Impact |
| :--- | :--- | :--- | :--- |
| **`@ts-ignore`** | **No** | None | **Too Loose:** Encourages type safety neglect and hides new, unrelated bugs. |
| **`@ts-expect-error`** | **Yes** | Hard Compilation Error (`TS2578`) | **Too Strict:** Halts the entire build/CI pipeline when the suppression becomes unused. |

When a developer explicitly or implicitly updates a dependency and the underlying type error is resolved, the resulting `TS2578` error immediately fails the build. This forces a synchronous context switch and cleanup task, making it an impractical solution for temporary dependency workarounds in high-velocity teams.

3. **What workarounds are you using in the meantime?**

The current workarounds leave much to be desired:
* Falling back to the permanently unsafe `@ts-ignore` to maintain CI stability.
* Implementing brittle internal patches to TS to intercept and programmatically downgrade the severity of the `TS2578` error

### 🔍 Search Terms

@ts-expect-error @ts-ignore warning

### ✅ Viability Checklist

- [x] This wouldn't be a breaking change in existing TypeScript/JavaScript code
- [x] This wouldn't change the runtime behavior of existing JavaScript code
- [x] This could be implemented without emitting different JS based on the types of the expressions
- [x] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
- [x] This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
- [x] This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

ファイルやテストは指定されていません。まず、@ts-expect-error と診断 TS2578 の既存の処理を追跡し、次に提案されているディレクティブとコンパイラーオプションの設計を比較してください。未使用の抑制によって警告レベルの診断が生成され、build が失敗しなければ完了です。

索引モデルが issue の本文から書いたものです。