Input

Found in sveltejs/svelte repo.

Files: packages/svelte/src/compiler/legacy.js (20+ instances), packages/svelte/src/compiler/phases/3-transform/client/visitors/EachBlock.js, packages/svelte/src/compiler/phases/3-transform/client/visitors/Program.js, packages/svelte/src/compiler/phases/3-transform/server/visitors/Program.js, packages/svelte/src/compiler/phases/3-transform/shared/transform-async.js

Minimal reproduction:

// Example 1: .map() callback
const result = items.map(
  (child) => /** @type {SomeType} */ (visit(child))
);

// Example 2: function argument
const body = transform_body(
  state.analysis.instance_body,
  b.id('$.run'),
  (node) => /** @type {Node} */ (context.visit(node))
);

Config

{
  "useTabs": true,
  "singleQuote": true,
  "trailingComma": "none",
  "printWidth": 100
}

Oxfmt output

// Example 1
const result = items.map((child) =>
	/** @type {SomeType} */ (visit(child))
);

// Example 2
const body = transform_body(state.analysis.instance_body, b.id('$.run'), (node) =>
	/** @type {Node} */ (context.visit(node))
);

Prettier output

Prettier version: 3.8.1

// Example 1
const result = items.map(
	(child) => /** @type {SomeType} */ (visit(child))
);

// Example 2
const body = transform_body(
	state.analysis.instance_body,
	b.id('$.run'),
	(node) => /** @type {Node} */ (context.visit(node))
);

Additional notes

When an arrow function body starts with a JSDoc inline type cast (/** @type {X} */), Prettier breaks after the opening parenthesis and keeps the entire arrow expression on one line, while Oxfmt breaks after => and puts the JSDoc type cast + body on the next line.

This pattern occurs 20+ times in legacy.js alone (all with the same .map((child) => /** @type {X} */ (visit(child))) pattern), plus several other files. It's the most frequent diff in the Svelte repo.