docs: list EquatableArray in the changelog, the README and the docs

Adds an Unreleased section to the changelog, the type to the collection
lists, and its folders and libraries to the agent instructions.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: xperiandri

.github/copilot-instructions.md

@@ -23,6 +23,9 @@
 │   │   ├── FlatList.fs / FlatList.fsi
 │   │   ├── FlatListBuilder.fs
 │   │   └── FlatListCE.fs
+│   ├── EquatableArray/                                 – ImmutableArray with value semantics, JSON converter, patterns
+│   │   ├── EquatableArray.fs / EquatableArray.fsi
+│   │   └── EquatableArrayPatterns.fs / EquatableArrayPatterns.fsi
 │   ├── IndexedList/                                    – ImmutableList API surface and builders
 │   │   ├── IIndexedList.fs / IIndexedList.fsi
 │   │   ├── IndexedList.fs / IndexedList.fsi
@@ -52,9 +55,11 @@
 │       ├── ISortedSet.fs / ISortedSet.fsi
 │       ├── SortedSet.fs / SortedSet.fsi
 │       └── SortedSetCE.fs
+├── tests/FSharp.Collections.Immutable.CSharp.Tests/     – MSTest project in C#: collection expressions, ranges, operators
 └── tests/FSharp.Collections.Immutable.Tests/            – MSTest test project
     ├── HelperTests.fs
     ├── TestCategories.fs                               – centralized custom test category attributes
+    ├── EquatableArray/                                 – focused test files per operation group
     ├── FlatList/                                       – focused test files per operation group
     ├── IndexedList/                                    – focused test files per operation group
     ├── HashMap/                                        – focused test files per operation group
@@ -69,8 +74,10 @@
 
 * [`System.Collections.Immutable`](https://www.nuget.org/packages/System.Collections.Immutable/) – immutable collections foundation
 * [`FSharp.Core`](https://www.nuget.org/packages/FSharp.Core/) – F# language core library
+* [`System.Text.Json`](https://learn.microsoft.com/dotnet/standard/serialization/system-text-json/overview) – the JSON converter of `EquatableArray` (shared framework, no package)
 * [`MSTest`](https://github.com/microsoft/testfx) – test framework
 * [`Unquote`](https://github.com/SwensenSoftware/unquote) – expressive assertions for complex checks
+* [`FSharp.SystemTextJson`](https://github.com/Tarmil/FSharp.SystemTextJson) – JSON tests with F# records and unions
 * [`FAKE`](https://fake.build/) – build and release scripting
 * [`Argu`](https://github.com/fsprojects/Argu) – command-line parsing for build tooling
 

CHANGELOG.md

@@ -5,6 +5,20 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+* `EquatableArray<'T>`: a struct over one `ImmutableArray<'T>` with value semantics, for fields of records and unions,
+  dictionary and set keys and persisted documents (ADR 0002)
+  * Equality and the hash code use all elements; every caller gets them, C# `==` and `!=` included
+  * Comparison puts shorter arrays first, then orders by the first different element, in the order of F# comparison
+  * The default value is the empty array
+  * Conversion to and from `ImmutableArray<'T>` does not copy; C# collection expressions and ranges work
+  * A System.Text.Json converter that needs no registration
+  * The `EquatableArray` module: `empty`, `ofArray`, `ofImmutableArray`, `ofList`, `ofSeq`, `singleton`,
+    `unsafeOfArray`, `isEmpty`, `length`, `map`, `toImmutableArray`
+  * The struct partial active patterns `Arr0`, `Arr1`, `Arr2`, `Arr3` and `ArrN`
+
 ## [1.0.0] - 2020-02-23
 
 First release

README.md

@@ -11,6 +11,7 @@ Please also join the [F# Open Source Group](http://fsharp.github.com)
 ## Features
 
 * `FlatList` (`ImmutableArray`)
+* `EquatableArray<'T>` (an `ImmutableArray` with value equality, comparison and an empty default value)
 * `ImmutableList`
 * `Stack` (`ImmutableStack`)
 * `Queue` (`ImmutableQueue`)

docsSrc/Explanations/Background.md

@@ -25,6 +25,7 @@ While F# has its own built-in immutable collections, System.Collections.Immutabl
 ## Available Collections
 
 - `FlatList` (`ImmutableArray`)
+- `EquatableArray<'T>` (an `ImmutableArray` with value equality, comparison and an empty default value)
 - `ImmutableList`
 - `Stack` (`ImmutableStack`)
 - `Queue` (`ImmutableQueue`)

docsSrc/index.md

@@ -7,6 +7,7 @@ F# bindings for [System.Collections.Immutable](https://learn.microsoft.com/en-us
 ## Key Features
 
 - `FlatList` (`ImmutableArray`)
+- `EquatableArray<'T>` (an `ImmutableArray` with value equality, comparison and an empty default value)
 - `ImmutableList`
 - `Stack` (`ImmutableStack`)
 - `Queue` (`ImmutableQueue`)