test-repo/changelog_unreleased/javascript/10278.md

Fix error thrown on expressions like a(b => c => function (){}) (#10278 by @thorn0)

Regression from v2.2.0.

// Input
a(b => c => function (){})

// Prettier stable
TypeError: Cannot read property 'length' of undefined

// Prettier main
a((b) => (c) => function () {});