Microsoft/TypeScript

Default type imported with `import type` from not-found module not flagged when used as a value

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#57,820 opened on Mar 18, 2024

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 (3 comments) (0 reactions) (0 assignees)TypeScript (6,726 forks)batch import
BugDomain: BinderHelp Wanted

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Description

🔎 Search Terms

cannot be used as a value because it was imported using import type

🕗 Version & Regression Information

  • This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.4.2#code/JYWwDg9gTgLgBDAnmApnAKnAZlCIBQA9IXAAIwDOAtCgB6oDGMNUuU+ccA5CBACZcA3PnwMIAOwrx4AXgzD8oSLDgBvJKjgBVAL7ZcBYmUo16KJizYduvAQrGT4AVzhytwoA

💻 Code

import type T from
// @ts-expect-error
  'mod';

const t = T;

import {type U} from
// @ts-expect-error
  'mod';

const u = U;

🙁 Actual behavior

TS does not error on the usage of T.

TS errors on the usage of U with the error

'U' cannot be used as a value because it was imported using 'import type'.(1361)

🙂 Expected behavior

TS errors on the usage of T with the error

'T' cannot be used as a value because it was imported using 'import type'.(1361)

TS errors on the usage of U with the error

'U' cannot be used as a value because it was imported using 'import type'.(1361)

Additional information about the issue

No response

Contributor guide

Research direction
Investigate the type checker logic for detecting value usage of type only imports. Specifically, look at how default imports are handled compared to named imports in the import type resolution. The error 1361 is emitted when a type only import is used as a value; currently it works for named imports but not for default imports. Find where the check occurs and extend it to cover default imports.
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
TypeScriptGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65