Disallow optional calls on import.defer

[KIM HYEONSANG (HyeonsangKim)]

Fixes #63679

Summary

• Report a parse error for import.defer?.(...).
• Cover the TypeScript generic optional-call form import.defer?.<T>(...) as well.
• Preserve normal import.defer(...) calls and add conformance baselines for all three cases.

The parser reuses the existing TS1005: '(' expected diagnostic. This matches the current diagnostics for other invalid standalone uses of import.defer and avoids adding a new public diagnostic for the same grammar requirement.

Tests

• go -C ./tsc test -count=1 -run='TestLocal/importDeferOptionalCall' ./internal/testrunner
• npx hereby generate
• npx hereby build
• npx hereby test
• npx hereby test:all
• npx hereby lint
• npx hereby check:format
• npm run -w @typescript/typescript build
• npm run -w @typescript/typescript test
• npm run -w native-preview build
• go -C ./tsc mod tidy -diff
• go -C ./tools mod tidy -diff
• go work sync

The full suite was also rerun with Node.js 24 LTS.

Prior work

This incorporates the syntax coverage identified in #63690 and microsoft/typescript-go#4794. Those PRs were closed during the TypeScript/Go repository transition rather than because the parser direction was rejected.

AI assistance disclosure

I used Codex to help implement and validate this patch. I selected this specific issue, reviewed and understand the parser change and generated baselines, and will personally respond to review feedback and revise the change as needed.

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[Copilot]

Pull request overview

Disallows optional-call syntax on import.defer while preserving standard deferred imports.

Changes:

• Adds parser diagnostics for ordinary and generic optional calls.
• Adds conformance coverage and generated baselines.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tsc/internal/parser/parser.go	Rejects optional import.defer calls.
tsc/testdata/tests/cases/conformance/importDefer/importDeferOptionalCall.ts	Adds conformance cases.
tsc/testdata/baselines/reference/conformance/importDeferOptionalCall.errors.txt	Captures diagnostics.
tsc/testdata/baselines/reference/conformance/importDeferOptionalCall.js	Captures emitted JavaScript.
tsc/testdata/baselines/reference/conformance/importDeferOptionalCall.types	Captures inferred types.
tsc/testdata/baselines/reference/conformance/importDeferOptionalCall.symbols	Captures symbol resolution.

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