`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

Reproduisez le crash avec le snippet d’interface et les cas d’accesseurs signalés. Commencez par getAnnotatedAccessorType, getTypeOfAccessors et getConditionalFlowTypeOfType dans la pile du checker signalée, puis localisez les sources TypeScript correspondantes et la configuration des tests de régression. C’est terminé lorsque ces accesseurs ne provoquent plus de crash et que le comportement existant de 5.9 reste couvert par un test.