[Gabriel Fonseca (gabrielvfonseca)]

Fixes #64438. Automatic JSX runtime in a script file now reports TS2884 with guidance to add export {}. Added regression coverage and updated legacy module-detection baselines. Validation: npx hereby test (168194 tests, 2148 skipped), npx hereby lint, npx hereby check:format, and npx hereby build.

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[Copilot]

🟡 Changes recommended

The new guard also rejects valid preserve and react-native scripts that only need JSX type resolution.

1 open issue

• Preserve JSX type lookup for non-transforming JSX modes · New

1 file not reviewed

• tsc/internal/diagnostics/diagnostics_generated.go: Generated file

What changed in this PR

Improves the automatic JSX diagnostic for script files, addressing #64438 with guidance to add export {}.

Changes:

• Adds TS2884 and a script-file check.
• Adds regression coverage and updates legacy module-detection baselines.

File	Description
tsc/​testdata/​tests/​cases/​compiler/​jsxScriptFile.tsx	Adds script-file regression case.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFile.types	Records inferred types.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFile.symbols	Records symbols.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFile.js	Records emitted JavaScript.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFile.errors.txt	Records expected diagnostics.
tsc/​testdata/​baselines/​reference/​compiler/​commentsOnJSXExpressionsArePreserved(jsx=react-jsxdev,module=commonjs,moduledetection=legacy).errors.txt	Updates development-runtime diagnostic.
tsc/​testdata/​baselines/​reference/​compiler/​commentsOnJSXExpressionsArePreserved(jsx=react-jsx,module=commonjs,moduledetection=legacy).errors.txt	Updates production-runtime diagnostic.
tsc/​internal/​diagnostics/​diagnostics_generated.go	Registers generated TS2884 message.
tsc/​internal/​diagnostics/​diagnosticMessages.json	Defines TS2884.
tsc/​internal/​diagnostics/​diagnosticMessages.generated.json	Adds generated diagnostic entry.
tsc/​internal/​checker/​jsx.go	Reports script-specific JSX error.

_{Review effort: Balanced}