`get self(): this` in an interface crashes the checker (6.0 regression)

🔎 Search Terms

getConditionalFlowTypeOfType, getAnnotatedAccessorType, Cannot read properties of undefined (reading 'flags'), accessor this type

🕗 Version & Regression Information

• Crashes in 6.0.3 and nightly (6.0.0-dev.20260416); 5.9.3 is clean — a 6.0 regression

💻 Code

interface I {
    get self(): this
}

🙁 Actual behavior

tsc crashes:

TypeError: Cannot read properties of undefined (reading 'flags')
    at getConditionalFlowTypeOfType (typescript/lib/_tsc.js:65892:23)
    at getTypeFromTypeNode (typescript/lib/_tsc.js:68622:12)
    at getAnnotatedAccessorType (typescript/lib/_tsc.js:62162:20)
    at getTypeOfAccessors (typescript/lib/_tsc.js:62180:99)
    at checkAccessorDeclarationDiagnostics (typescript/lib/_tsc.js:87089:26)

Any this nested inside the accessor's return type annotation triggers it too (get pair(): [this, string]). A method or property signature with the same this type is fine.

🙂 Expected behavior

No crash (5.9 checks this without errors).

Additional information about the issue

No response

Reproduce el crash con el snippet de la interfaz y los casos de accessors reportados. Empieza por getAnnotatedAccessorType, getTypeOfAccessors y getConditionalFlowTypeOfType en el checker stack reportado, y después localiza las fuentes correspondientes de TypeScript y la configuración de las pruebas de regresión. La tarea estará terminada cuando estos accessors ya no provoquen un crash y el comportamiento existente de 5.9 siga cubierto por una prueba.