✨ feat(array-methods): add Array.Unshift method

[AshGreyG]

📝 Description

This PR introduces a new method of Array namespace:

• Array.Unshift<Arr, E>

🌴 PR Type

• ✨ Feature
• 🐛 Bugfix
• 🚑 Hotfix
• 💡 Doc comment
• 🧪 Test
• 📝 Document
• 🐋 Other (please describe)

🔥 Linked issues

👾 Additional context

⛳ Change log

• I have updated the changelog/next.md with my changes.

Summary by Sourcery

Introduce the Array.Unshift type helper to the Array namespace for prepending elements to tuple types, and register corresponding tests and changelog updates

New Features:

• Add Array.Unshift<Arr, E> type to prepend an element to tuple types

Documentation:

• Fix changelog date formatting and add an entry for Array.Unshift

Tests:

• Add type-level tests for Array.Unshift in lib-Array.test.ts and update the lib-gen script for its test cases

[sourcery-ai]

Reviewer's Guide

Implements a new Array.Unshift utility by prepending an element to a tuple via variadic tuple spread, complete with JSDoc, unit tests, script integration, and changelog entry.

Class diagram for the new Array.Unshift type

classDiagram
  class Array {
    <<namespace>>
  }
  class Unshift {
    <<type>>
    +<Arr extends unknown[], E extends unknown> [E, ...Arr]
  }
  Array <|.. Unshift : contains

Loading

File-Level Changes

Change	Details	Files
Implement Unshift type alias for Arrays	Add JSDoc comment describing Unshift semantics Define Unshift<Arr, E> = [E, ...Arr] type	lib/Array/index.d.ts
Add unit tests for Unshift	Add Expect assertions covering empty and non-empty arrays Test element prepending in various scenarios	test/lib-Array.test.ts
Integrate Unshift into test generation script	Insert Array.Unshift case into lib-gen.sh test_cases	test/script/lib-gen.sh
Record Unshift in changelog	Add Unshift entry under 2025-07-10 release section	changelog/next.md

---

Tips and commands

Interacting with Sourcery

• Trigger a new review: Comment @sourcery-ai review on the pull request.
• Continue discussions: Reply directly to Sourcery's review comments.
• Generate a GitHub issue from a review comment: Ask Sourcery to create an
  issue from a review comment by replying to it. You can also reply to a
  review comment with @sourcery-ai issue to create an issue from it.
• Generate a pull request title: Write @sourcery-ai anywhere in the pull
  request title to generate a title at any time. You can also comment
  @sourcery-ai title on the pull request to (re-)generate the title at any time.
• Generate a pull request summary: Write @sourcery-ai summary anywhere in
  the pull request body to generate a PR summary at any time exactly where you
  want it. You can also comment @sourcery-ai summary on the pull request to
  (re-)generate the summary at any time.
• Generate reviewer's guide: Comment @sourcery-ai guide on the pull
  request to (re-)generate the reviewer's guide at any time.
• Resolve all Sourcery comments: Comment @sourcery-ai resolve on the
  pull request to resolve all Sourcery comments. Useful if you've already
  addressed all the comments and don't want to see them anymore.
• Dismiss all Sourcery reviews: Comment @sourcery-ai dismiss on the pull
  request to dismiss all existing Sourcery reviews. Especially useful if you
  want to start fresh with a new review - don't forget to comment
  @sourcery-ai review to trigger a new review!

Customizing Your Experience

Access your dashboard to:

• Enable or disable review features such as the Sourcery-generated pull request
  summary, the reviewer's guide, and others.
• Change the review language.
• Add, remove or edit custom review instructions.
• Adjust other review settings.

Getting Help

• Contact our support team for questions or feedback.
• Visit our documentation for detailed guides and information.
• Keep in touch with the Sourcery team by following us on X/Twitter, LinkedIn or GitHub.

[sourcery-ai]

Hey @AshGreyG - I've reviewed your changes and they look great!

Prompt for AI Agents

Please address the comments from this code review:
## Individual Comments

### Comment 1
<location> `test/lib-Array.test.ts:20` </location>
<code_context>
   Expect<Equal<Array.CreateArrayFromLength<0>, []>>,
   Expect<Equal<Array.CreateArrayFromLength<-1>, []>>,

+  // Array.Unshift
+  Expect<Equal<Array.Unshift<[1,2,3], 4>, [4,1,2,3]>>,
+  Expect<Equal<Array.Unshift<[], []>, [[]]>>,
+  Expect<Equal<Array.Unshift<[1], []>, [[],1]>>,
+  Expect<Equal<Array.Unshift<[], 1>, [1]>>,
+
   // Array.MultipleConcat
</code_context>

<issue_to_address>
Missing tests for edge cases with complex element types in Array.Unshift.

Please add tests for unshifting arrays, objects, and union types to verify Unshift handles complex element types correctly.
</issue_to_address>

<suggested_fix>
<<<<<<< SEARCH
  Expect<Equal<Array.Unshift<[1,2,3], 4>, [4,1,2,3]>>,
  Expect<Equal<Array.Unshift<[], []>, [[]]>>,
  Expect<Equal<Array.Unshift<[1], []>, [[],1]>>,
  Expect<Equal<Array.Unshift<[], 1>, [1]>>,
=======
  Expect<Equal<Array.Unshift<[1,2,3], 4>, [4,1,2,3]>>,
  Expect<Equal<Array.Unshift<[], []>, [[]]>>,
  Expect<Equal<Array.Unshift<[1], []>, [[],1]>>,
  Expect<Equal<Array.Unshift<[], 1>, [1]>>,

  // Array.Unshift edge cases with complex element types
  Expect<Equal<Array.Unshift<[{a: 1}, {b: 2}], {c: 3}>, [{c: 3}, {a: 1}, {b: 2}]>>,
  Expect<Equal<Array.Unshift<[[1, 2], [3, 4]], [5, 6]>, [[5, 6], [1, 2], [3, 4]]>>,
  Expect<Equal<Array.Unshift<[1 | 2, 3], 4 | 5>, [4 | 5, 1 | 2, 3]>>,
  Expect<Equal<Array.Unshift<[], {foo: string; bar: number}>, [{foo: string; bar: number}]>>,
  Expect<Equal<Array.Unshift<[{x: number}], {y: boolean}>, [{y: boolean}, {x: number}]>>,
>>>>>>> REPLACE

</suggested_fix>

---

Sourcery is free for open source - if you like our reviews please consider sharing them ✨

• X
• Mastodon
• LinkedIn
• Facebook

_{Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.}