[Shivashis Adhikari (shivashis-adhikari)]

Fixes #63584

Adding a label to a rest element made a recursive tuple type fail:

type Ok  = string | ["i", ...Ok[]];          // OK
type Bad = string | ["i", ...rest: Bad[]];   // error TS2456: Type alias 'Bad' circularly references itself.

Cause

mayResolveTypeAlias decides whether a tuple type is deferred, and deferral is what lets a type alias refer to itself through a tuple. For an unlabeled rest element ...T[] (a RestType) it checks the element type T. A labeled rest element ...rest: T[] is a NamedTupleMember, and that case passed the array type T[] to mayResolveTypeAlias, which returns false for array types. The tuple was then resolved eagerly and hit the cycle. Because the alias then resolved to any, values assigned to it were no longer checked either.

Fix

A NamedTupleMember with a ... token now goes through the same check as a RestType. The check moved into a small helper so both cases share it

Tests

recursiveTupleTypeLabeledRestElement.ts covers a labeled rest element on its own, after and before other labeled elements, with a parenthesized element type, in a union of tuples (the example from the issue), in a generic alias, and in a JSDoc @typedef. It also assigns valid and invalid values to each type, so the baselines show the types are checked again.

The first commit adds the test with the current baselines which show the false TS2456 errors. The second commit is the fix, and the third updates the baselines.

Labeled and unlabeled rest elements already behaved the same for ...[T], ...T[][] and ...readonly T[]. This change does not affect those, and no existing baselines change.

npx hereby validate --all passes.

AI disclosure: I've used Claude Code to help me with this. I have reviewed it and will respond to review feedback myself.

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