Microsoft/TypeScript

Should not allow `import.defer?.('x')`

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#63,679 opened on Jul 25, 2026

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 (2 comments) (0 reactions) (0 assignees)TypeScript (13,395 forks)batch import
BugDomain: ParserHelp Wanted

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Description

🔎 Search Terms

"import defer"

🕗 Version & Regression Information

  • This changed between versions ______ and _______
  • This changed in commit or PR _______
  • This is the behavior in every version I tried, and I reviewed the FAQ for entries about 6.0.3_____
  • I was unable to test this on prior versions because _______

⏯ Playground Link

https://www.typescriptlang.org/play/?moduleResolution=99&target=99&ssl=3&ssc=40&pln=2&pc=1#code/JYWwDg9gTgLgBPAZlCI4HIYE8wFMDOAxlMGDOgNwBQVhEAdvvGHALxyiSwB0AJrolxQA-NwAUmHAWKlyASgpA

💻 Code

import.defer?.('x');

🙁 Actual behavior

No errors.

🙂 Expected behavior

Should not allow it as an optional call.

Additional information about the issue

Parsers like Oxc, Yuku, SWC, Babel all reject it. I didn't read the spec, but unless they are wrong.

Contributor guide

Research direction
Examine the TypeScript parser code related to import.defer and optional call. Look for how import.defer expression is created in the AST and how optional call (?.()) is handled. Fix the parser to reject optional calls on import.defer.
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.
2
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
GitNode.js
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75