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--- rfc:records [2024/07/26 07:40] – remove confusing sentence withinboredom
+++ rfc:records [2024/11/17 21:38] (current) – withinboredom
@@ Line 1: / Line 1: @@
 ====== PHP RFC: Records ======
   * Version: 0.9
   * Date: 2024-07-19
-  * Author: Robert Landers, landers.robert@gmail.com
+  * Author: Robert Landers, <landers.robert@gmail.com>, <rob@bottled.codes>
-  * Status: Draft (or Under Discussion or Accepted or Declined)
+  * Status: Under Discussion (or Accepted or Declined)
   * First Published at: http://wiki.php.net/rfc/records
 ===== Introduction =====
-In modern PHP development, the need for concise and immutable data structures is increasingly recognized. Inspired by the concept of "records", "data objects", or "structs" in other languages, this RFC proposes the addition of ''record'' objects in PHP. These records will provide a concise and immutable data structure, distinct from ''readonly'' classes, enabling developers to define immutable objects with less boilerplate code.
+This RFC proposes the introduction of ''%%record%%'' objects, which are immutable classes with [[https://en.wikipedia.org/wiki/Value_semantics|value semantics]].
-===== Proposal =====
+==== Value objects ====
-This RFC proposes the introduction of a new record keyword in PHP to define immutable data objects. These objects will allow properties to be initialized concisely and will provide built-in methods for common operations such as modifying properties and equality checks using a function-like instantiation syntax. Records can implement interfaces and use traits but cannot extend other records or classes.
+Value objects are immutable objects that represent a value. They’re used to store values with a different semantic by wrapping their technical value, adding additional context. For example, a ''%%Point%%'' object with ''%%x%%'' and ''%%y%%'' properties can represent a point in a 2D space, and an ''%%ExpirationDate%%'' can represent a date when something expires. This prevents developers from accidentally using the wrong value in the wrong context.
-=== Syntax and semantics ===
+Consider this example where a function accepts an integer as a user ID, and the ID is accidentally set to a nonsensical value:
-== Definition ==
+<code php>
+function updateUserRole(int $userId, string $role): void {
+    // ...
+}
+$user = getUser(/*...*/)
+$uid = $user->id;
+// ...
+$uid = 5; // accidentally sets uid to an unrelated integer
+// ...
+updateUserRole($uid, 'admin'); // accidental passes a nonsensical value for uid
+</code>
-A ''record'' is defined by the word "record", followed by the name of its type, an open parenthesis containing zero or more typed parameters that become public, immutable, properties. They may optionally implement an interface using the ''implements'' keyword. A ''record'' body is optional.
+Currently, the only solution to this is to use a **class**, but this requires significant boilerplate code. Further, **readonly classes** have many edge cases and are rather unwieldy.
-A ''record'' may NOT contain a constructor; instead of defining initial values, property hooks should be used to produce computable values on-demand. Defining a constructor emits a compilation error.
+=== The solution ===
-A ''record'' body may contain property hooks, methods, and use traits. Regular properties may also be defined, but they are immutable by default and are no different than ''const''.
+Like arrays, strings, and other values, **record** objects are strongly equal (''%%===%%'') to each other if they contain the same values.
-Static properties and methods are forbidden in a ''record'' (this includes ''const'', a regular property may be used instead). Attempting to define static properties, methods, constants results in a compilation error.
+Let’s take a look at an updated example using a ''%%record%%'' type for ''%%UserId%%''. Thus, if someone were to pass an ''%%int%%'' to ''%%updateUserRole%%'', it would throw an error:
 <code php>
-namespace Geometry;
+record UserId(int $id);
-interface Shape {
+function updateUserRole(UserId $userId, string $role): void {
-  public function area(): float;
+    // ...
 }
-trait Dimension {
+$user = getUser(/*...*/)
-  public function dimensions(): array {
+$uid = $user->id; // $uid is a UserId object
-    return [$this->width, $this->height];
+// ...
+$uid = 5;
+// ...
+updateUserRole($uid, 'admin'); // This will throw a TypeError
+</code>
+Now, if ''%%$uid%%'' is accidentally set to an integer, the call to ''%%updateUserRole%%'' will throw a ''%%TypeError%%'' because the function expects a ''%%UserId%%'' object instead of a plain integer.
+===== Proposal =====
+This RFC proposes the introduction of a ''%%record%%'' keyword in PHP to define immutable value objects. These objects will allow properties to be initialized concisely and will provide built-in methods for common operations such as modifying properties, performing equality checks, and using a function-like instantiation syntax. Records can implement interfaces and use traits but can’t extend other records or classes; composition is allowed, however.
+==== Syntax and semantics ====
+=== Definition ===
+A **record** is defined by the keyword ''%%record%%'', followed by the name of its type (e.g., ''%%UserId%%''), and then must list one or more typed parameters (e.g., ''%%int $id%%'') that become properties of the record. A parameter may provide ''%%private%%'' or ''%%public%%'' modifiers, but are ''%%public%%'' when not specified. This is referred to as the "inline constructor."
+A **record** may optionally implement an interface using the ''%%implements%%'' keyword, which may optionally be followed by a record body enclosed in curly braces ''%%{}%%''.
+A **record** may not extend another record or class.
+A **record** may contain a traditional constructor with zero arguments to perform further initialization.
+A **record** body may contain property hooks, methods, and use traits.
+A **record** body may also declare properties whose values are only mutable during a constructor call. At any other time, the property is immutable.
+A **record** body may also contain static methods and properties, which behave identically to static methods and properties in classes. They may be accessed using the ''%%::%%'' operator.
+As an example, the following code defines a **record** named ''%%Pigment%%'' to represent a color, ''%%StockPaint%%'' to represent paint colors in stock, and ''%%PaintBucket%%'' to represent a collection of stock paints mixed together. The actual behavior isn’t important, but illustrates the syntax and semantics of records.
+<code php>
+namespace Paint;
+// Define a record with several primary color properties
+record Pigment(int $red, int $yellow, int $blue) {
+  // property hooks are allowed
+  public string $hexValue {
+    get => sprintf("#%02x%02x%02x", $this->red, $this->yellow, $this->blue),
+  }
+  // methods are allowed
+  public function mix(Pigment $other, float $amount): Pigment {
+    return $this->with(
+      red: $this->red * (1 - $amount) + $other->red * $amount,
+      yellow: $this->yellow * (1 - $amount) + $other->yellow * $amount,
+      blue: $this->blue * (1 - $amount) + $other->blue * $amount
+    );
+  }
+  // all properties are mutable in constructors
+  public function __construct() {
+    $this->red = max(0, min(255, $this->red));
+    $this->yellow = max(0, min(255, $this->yellow));
+    $this->blue = max(0, min(255, $this->blue));
+  }
+  public function with() {
+    // prevent the creation of a new Pigment from an existing pigment
+    throw new \LogicException("Cannot create a new Pigment from an existing pigment");
   }
 }
-record Vector2(int $x, int $y);
+// simple records do not need to define a body
+record StockPaint(Pigment $color, float $volume);
-record Rectangle(Vector2 $leftTop, Vector2 $rightBottom) implements Shape {
+record PaintBucket(StockPaint ...$constituents) {
-  use Dimension;
+  public function mixIn(StockPaint $paint): PaintBucket {
+    return $this->with(...[...$this->constituents, $paint]);
-  public int $height = 1; // this will always and forever be "1", it is immutable.
+  }
-  public int $width { get => $this->rightBottom->x - $this->topLeft->x; }
+  public function color(): Pigment {
-  public int $height { get => $this->rightBottom->y - $this->topLeft->y; }
+    return array_reduce($this->constituents, fn($color, $paint) => $color->mix($paint->color, $paint->volume), Pigment(0, 0, 0));
-  public function area(): float {
-    return $this->width * $this->height;
   }
 }
 </code>
-== Usage ==
+=== Usage ===
-A ''record'' may be used as a ''readonly class'', as the behavior of it is very similar with no key differences to assist in migration from ''readonly class''.
+A record may be used much like a class, as the behavior of the two is very similar, assisting in migrating from one implementation to another:
 <code php>
-$rect1 = Rectangle(Point(0, 0), Point(1, -1));
+$gray = $bucket->mixIn($blackPaint)->mixIn($whitePaint);
-$rect2 = $rect1->with(topLeft: Point(0, 1));
+</code>
+Records are instantiated in a function format, with ''%%&%%'' prepended. This provides visual feedback that a record is being created instead of a function call.
+<code php>
+$black = &Pigment(0, 0, 0);
+$white = &Pigment(255, 255, 255);
+$blackPaint = &StockPaint($black, 1);
+$whitePaint = &StockPaint($white, 1);
+$bucket = &PaintBucket();
+$gray = $bucket->mixIn($blackPaint)->mixIn($whitePaint);
+$grey = $bucket->mixIn($blackPaint)->mixIn($whitePaint);
-var_dump($rect2->dimensions());
+assert($gray === $grey); // true
 </code>
-== Optional parameters and default values ==
+=== Optional parameters and default values ===
-A ''record'' can also be defined with optional parameters that are set if left out during instantiation.
+A ''%%record%%'' can also be defined with optional parameters that are set if omitted during instantiation.
+One or more properties defined in the inline constructor may have a default value declared using the same syntax and rules as any other default parameter in methods/functions. If a property has a default value, it is optional when instantiating the record, and PHP will assign the default value to the property if omitted.
 <code php>
 record Rectangle(int $x, int $y = 10);
-var_dump(Rectangle(10)); // output a record with x: 10 and y: 10
+var_dump(&Rectangle(10)); // output a record with x: 10 and y: 10
 </code>
-== Auto-generated ''with'' method ==
+=== Auto-generated with method ===
-To enhance the usability of records, the RFC proposes automatically generating a ''with'' method for each record. This method allows for partial updates of properties, creating a new instance of the record with the specified properties updated.
+To make records more useful, the RFC proposes generating a ''%%with%%'' method for each record. This method allows for partial updates to the properties, creating a new instance of the record with the specified properties updated.
-The auto-generated ''with'' method accepts only named arguments defined in the constructor. No other property names can be used, and it returns a new record object with the given values.
+== How the with method works ==
+**Named arguments**
+The ''%%with%%'' method accepts only named arguments defined in the inline constructor. Properties not defined in the inline constructor can’t be updated by this method.
+**Variadic arguments**
+Variadic arguments from the inline constructor don’t require named arguments in the ''%%with%%'' method. However, mixing named and variadic arguments in the same ''%%with%%'' method call is not allowed by PHP syntax.
+Using named arguments:
 <code php>
-$point1 = Point(3, 4);
+record UserId(int $id) {
-$point2 = $point1->with(x: 5);
+  public string $serialNumber;
-$point3 = $point1->with(null, 10); // must use named arguments
-echo $point1->x; // Outputs: 3
+  public function __construct() {
-echo $point2->x; // Outputs: 5
+    $this->serialNumber = "U{$this->id}";
+  }
+}
+$userId = &UserId(1);
+$otherId = $userId->with(2); // Fails: Named arguments must be used
+$otherId = $userId->with(serialNumber: "U2"); // Error: serialNumber is not defined in the inline constructor
+$otherId = $userId->with(id: 2); // Success: id is updated
 </code>
-A developer may define their own ''with'' method if they so choose.
+Using variadic arguments:
-=== Performance considerations ===
+<code php>
+record Vector(int $dimensions, int ...$values);
-To ensure that records are both performant and memory-efficient, the RFC proposes leveraging PHP's copy-on-write (COW) semantics (similar to arrays) and interning values. Unlike interned strings, the garbage collector will be allowed to clean up these interned records when they are no longer needed.
+$vector = &Vector(3, 1, 2, 3);
+$vector = $vector->with(dimensions: 4); // Success: values are updated
+$vector = $vector->with(dimensions: 4, 1, 2, 3, 4); // Error: mixing named arguments with variadic arguments is not allowed by PHP syntax
+$vector = $vector->with(dimensions: 4)->with(1, 2, 3, 4); // Success: First update dimensions, then values
+</code>
+== Custom with method ==
+A developer may define their own ''%%with%%'' method if they choose, and reference the generated ''%%with%%'' method using ''%%parent::with()%%''. This allows a developer to define policies or constraints on how data can change from instance to instance.
 <code php>
-$point1 = Point(3, 4);
+record Planet(string $name, int $population) {
-$point2 = $point1; // No data duplication, $point2 references the same data as $point1
+  // create a with method that only accepts population updates
-$point3 = Point(3, 4); // No data duplication here either, it is pointing the the same memory as $point1
+  public function with(int $population): Planet {
+    return parent::with(population: $population);
+  }
+}
+$pluto = Planet("Pluto", 0);
+// we made it!
+$pluto = $pluto->with(population: 1);
+// and then we changed the name
+$mickey = $pluto->with(name: "Mickey"); // Error: no named argument for population
+</code>
-$point4 = $point1->with(x: 5); // Data duplication occurs here, creating a new instance with modified data
+=== Constructors ===
+A **record** has two types of constructors: the inline constructor and the traditional constructor.
+The inline constructor is always required and must define at least one parameter. The traditional constructor is optional and can be used for further initialization logic, but must not accept any arguments.
+When a traditional constructor exists and is called, the properties are already initialized to the values from the inline constructor and are mutable until the end of the method, at which point they become immutable.
+<code php>
+// Inline constructor defining two properties
+record User(string $name, string $emailAddress) {
+  public string $id;
+  // Traditional constructor
+  public function __construct() {
+    if (!is_valid_email($this->emailAddress)) {
+      throw new InvalidArgumentException("Invalid email address");
+    }
+    $this->id = hash('sha256', $this->emailAddress);
+    $this->name = ucwords($this->name);
+    // all properties are now immutable
+  }
+}
 </code>
-== Cloning and with() ===
+==== Implementing Interfaces ====
-Calling ''clone'' on a ''record'' results in the exact same record object being returned. As it is a "value" object, it represents a value and is the same thing as saying ''clone 3''—you expect to get back a ''3''.
+A **record** can implement interfaces, but it cannot extend other records or classes, but may use traits:
-''with'' may be called with no arguments, and it is the same behavior as ''clone''. This is an important consideration because a developer may call ''$new = $record->with(...$array)'' and we don't want to crash. If a developer wants to crash, they can do by ''assert($new !== $record)''.
+<code php>
+interface Vehicle {}
-=== Equality ===
+interface Car extends Vehicle {
+  public function drive(): void;
+}
-A ''record'' is always strongly equal (''==='') to another record with the same value in the properties, much like an ''array'' is strongly equal to another array containing the same elements. For all intents, ''$recordA === $recordB'' is the same as ''$recordA == $recordB''.
+interface SpaceShip extends Vehicle {
+  public function launch(): void;
+}
-Comparison operations will behave exactly like they do for classes.
+record FancyCar(string $model) implements Car {
+  public function drive(): void {
+    echo "Driving a Fancy Car {$this->model}";
+  }
+}
-==== Reflection ====
+record SpaceCar(string $model) implements Car, SpaceShip {
+  public function drive(): void {
+    echo "Driving a Space Car {$this->model}";
+  }
+  public function launch(): void {
+    echo "Launching a Space Car {$this->model}";
+  }
+}
-Records in PHP will be fully supported by the reflection API, providing access to their properties and methods just like regular classes. However, immutability and special instantiation rules will be enforced.
+record Submarine(string $model) implements Vehicle {
+  use Submersible;
+}
-=== ReflectionClass support ===
+record TowTruct(string $model, private Car $towing) implements Car {
+  use Towable;
+}
+</code>
-''ReflectionClass'' can be used to inspect records, their properties, and methods. Any attempt to modify record properties via reflection will throw an exception, maintaining immutability. Attempting to create a new instance via ''ReflectionClass'' will cause a ''ReflectionException'' to be thrown.
+==== Mental models and how it works ====
+From the perspective of a developer, declaring a record declares an object with the same name. The developer can consider the record function (the inline constructor) as a factory function that creates a new object or retrieves an existing object from an array.
+For example, this would be a valid mental model for a Point record:
 <code php>
-$point = Point(3, 4);
+record Point(int $x, int $y) {
-$reflection = new \ReflectionClass($point);
+    public float $magnitude;
+    public function __construct() {
+        $this->magnitude = sqrt($this->x ** 2 + $this->y ** 2);
+    }
+    public function add(Point $point): Point {
+        return &Point($this->x + $point->x, $this->y + $point->y);
+    }
+    public function dot(Point $point): int {
+        return $this->x * $point->x + $this->y * $point->y;
+    }
+}
+// similar to declaring the following function and class
+// used during construction to allow mutability
+class Point_Implementation {
+    public int $x;
+    public int $y;
+    public float $magnitude;
+    public function __construct() {
+        $this->magnitude = sqrt($this->x ** 2 + $this->y ** 2);
+    }
+    public function with(...$parameters) {
+        // validity checks omitted for brevity
+        $parameters = array_merge([$this->x, $this->y], $parameters);
+        return Point(...$parameters);
+    }
+    public function add(Point $point): Point {
+        return Point($this->x + $point->x, $this->y + $point->y);
+    }
+    public function dot(Point $point): int {
+        return $this->x * $point->x + $this->y * $point->y;
+    }
+}
+// used to enforce immutability but has nearly the same implementation
+readonly class Point {
+    public float $magnitude;
+    public function __construct(public int $x, public int $y) {}
+    public function with(...$parameters): self {
+        // validity checks omitted for brevity
+        $parameters = array_merge([$this->x, $this->y], $parameters);
+        return Point(...$parameters);
+    }
+    public function add(Point $point): Point {
+        return Point($this->x + $point->x, $this->y + $point->y);
+    }
+    public function dot(Point $point): int {
+        return $this->x * $point->x + $this->y * $point->y;
+    }
+}
-foreach ($reflection->getProperties() as $property) {
+function Point(int $x, int $y): Point {
-    echo $property->getName() . ': ' . $property->getValue($point) . PHP_EOL;
+    static $points = [];
+    $key = hash_object($mutablePoint);
+    if ($points[$key] ?? null) {
+        // return an existing point
+        return $points[$key];
+    }
+    // create a new point
+    $reflector = new \ReflectionClass(Point_Implementation::class);
+    $mutablePoint = $reflector->newInstanceWithoutConstructor();
+    $mutablePoint->x = $x;
+    $mutablePoint->y = $y;
+    $mutablePoint->__construct();
+    // copy properties to an immutable Point and return it
+    $point = new Point($mutablePoint->x, $mutablePoint->y);
+    $point->magnitude = $mutablePoint->magnitude;
+    return $points[$key] = $point;
 }
 </code>
-=== Immutability enforcement ===
+In reality, this is quite different from how it works in the engine, but this provides a mental model of how behavior should be expected to work.
-Attempts to modify record properties via reflection will throw an exception.
+==== Performance considerations ====
+To ensure that records are both performant and memory-efficient, the RFC proposes leveraging PHP’s copy-on-write (COW) semantics (similar to arrays) and interning values. Unlike interned strings, the garbage collector will be allowed to clean up these interned records when they’re no longer referenced.
+<code php>
+$point1 = &Point(3, 4);
+$point2 = $point1; // No data duplication, $point2 references the same data as $point1
+$point3 = Point(3, 4); // No data duplication, it is pointing to the same memory as $point1
+$point4 = $point1->with(x: 5); // Data duplication occurs here, creating a new instance
+$point5 = &Point(5, 4); // No data duplication, it is pointing to the same memory as $point4
+</code>
+=== Cloning and with() ===
+Calling ''%%clone%%'' on a ''%%record%%'' results in the same record object being returned. As it is a "value" object, it represents a value and is the same thing as saying ''%%clone 3%%''—you expect to get back a ''%%3%%''.
+If ''%%->with()%%'' is called with no arguments, a warning will be emitted, as this is most likely a mistake.
+==== Serialization and deserialization ====
+Records are fully serializable and deserializable, even when nested.
+<code php>
+record Single(string $value);
+record Multiple(string $value1, string $value2);
+echo $single = serialize(&Single('value')); // Outputs: "O:6:"Single":1:{s:5:"value";s:5:"value";}"
+echo $multiple = serialize(&Multiple('value1', 'value2')); // Outputs: "O:8:"Multiple":1:{s:6:"values";a:2:{i:0;s:6:"value1";i:1;s:6:"value2";}}"
+echo unserialize($single) === &Single('value'); // Outputs: true
+echo unserialize($multiple) === &Multiple('value1', 'value2'); // Outputs: true
+</code>
+If a record contains objects or values that are unserializable, the record will not be serializable.
+==== Equality ====
+A ''%%record%%'' is always strongly equal (''%%===%%'') to another record with the same value in the properties, much like an ''%%array%%'' is strongly equal to another array containing the same elements. For all intents, ''%%$recordA === $recordB%%'' is the same as ''%%$recordA == $recordB%%''.
+Comparison operations will behave exactly like they do for classes, which is currently undefined.
+=== Non-trivial values ===
+For non-trivial values (e.g., objects, closures, resources, etc.), the ''%%===%%'' operator will return ''%%true%%'' if the two operands reference the same instances.
+For example, if two different DateTime records reference the exact same date and are stored in a record, the records will not be considered equal:
+<code php>
+$date1 = DateTime('2024-07-19');
+$date2 = DateTime('2024-07-19');
+record Date(DateTime $date);
+$dateRecord1 = Date($date1);
+$dateRecord2 = Date($date2);
+echo $dateRecord1 === $dateRecord2; // Outputs: false
+</code>
+However, this can be worked around by being a bit creative (see: mental model) as only the values passed in the constructor are compared:
 <code php>
-try {
+record Date(string $date) {
-    $property = $reflection->getProperty('x');
+    public DateTime $datetime;
-    $property->setValue($point, 10); // This will throw an exception
-} catch (\ReflectionException $e) {
+    public function __construct() {
-    echo 'Exception: ' . $e->getMessage() . PHP_EOL; // "Cannot modify a record property"
+        $this->datetime = new DateTime($this->date);
+    }
 }
+$date1 = &Date('2024-07-19');
+$date2 = &Date('2024-07-19');
+echo $date1->datetime === $date2->datetime ? 'true' : 'false'; // Outputs: true
 </code>
-=== ReflectionFunction for implicit constructor ===
+==== Type hinting ====
-Using ''ReflectionFunction'' on a record will reflect the implicit constructor.
+A ''%%\Record%%'' interface will be added to the engine to allow type hinting for records. All records implement this interface.
 <code php>
-$constructor = new \ReflectionFunction('Geometry\Point');
+function doSomething(\Record $record): void {
-echo 'Constructor Parameters: ';
+    // ...
-foreach ($constructor->getParameters() as $param) {
-    echo $param->getName() . ' ';
 }
 </code>
-=== New functions and methods ===
+The only method on the interface is ''%%with%%'', which is a variadic method that accepts named arguments and returns ''%%self%%''.
-  * Calling ''is_object($record)'' will return ''true''.
+==== Reflection ====
-  * A new function, ''is_record($record)'', will return ''true'' for records, and ''false'' otherwise
-  * Calling ''get_class($record)'' will return the record name
+A new reflection class will be added to support records: ''%%ReflectionRecord%%'' which will inherit from ''%%ReflectionClass%%'' and add a few additional methods:
+  * ''%%ReflectionRecord::finalizeRecord(object $instance): Record%%'': Finalizes a record under construction, making it immutable.
+  * ''%%ReflectionRecord::isRecord(mixed $object): bool%%'': Returns ''%%true%%'' if the object is a record, and ''%%false%%'' otherwise.
+  * ''%%ReflectionRecord::getInlineConstructor(): ReflectionFunction%%'': Returns the inline constructor of the record as ''%%ReflectionFunction%%''.
+  * ''%%ReflectionRecord::getTraditionalConstructor(): ReflectionMethod%%'': Returns the traditional constructor of the record as ''%%ReflectionMethod%%''.
+  * ''%%ReflectionRecord::makeMutable(Record $instance): object%%'': Returns a new record instance with the properties mutable.
+  * ''%%ReflectionRecord::isMutable(Record $instance): bool%%'': Returns ''%%true%%'' if the record is mutable, and ''%%false%%'' otherwise.
+Using ''%%ReflectionRecord%%'' will allow developers to inspect records, their properties, and methods, as well as create new instances for testing or custom deserialization.
+Attempting to use ''%%ReflectionClass%%'' or ''%%ReflectionFunction%%'' on a record will throw a ''%%ReflectionException%%'' exception.
+=== finalizeRecord() ===
+The ''%%finalizeRecord()%%'' method is used to make a record immutable and look up its value in the internal cache, returning an instance that represents the finalized record.
+Calling ''%%finalizeRecord()%%'' on a record that has already been finalized will return the same instance. Attempting to finalize a regular object will throw a ''%%ReflectionException%%''.
+=== isRecord() ===
+The ''%%isRecord()%%'' method is used to determine if an object is a record. It returns ''%%true%%'' if the object is a finalized record.
+=== getInlineConstructor() ===
+The ''%%getInlineConstructor()%%'' method is used to get the inline constructor of a record as a ''%%ReflectionFunction%%''. This can be used to inspect inlined properties and their types.
+Invoking the ''%%invoke()%%'' method on the ''%%ReflectionFunction%%'' will create a finalized record.
+=== getTraditionalConstructor() ===
+The ''%%getTraditionalConstructor()%%'' method is used to get the traditional constructor of a record as a ''%%ReflectionMethod%%''. This can be useful to inspect the constructor for further initialization.
+Invoking the ''%%invoke()%%'' method on the ''%%ReflectionMethod%%'' on a finalized record will throw an exception.
+=== makeMutable() ===
+The ''%%makeMutable()%%'' method is used to create a new instance of a record with mutable properties. The returned instance doesn’t provide any value semantics and should only be used for testing purposes or when there is no other option.
+A mutable record can be finalized again using ''%%finalizeRecord()%%''. A mutable record will not be considered a record by ''%%isRecord()%%'' or implement the ''%%\Record%%'' interface. It is a regular object with the same properties and methods as the record. For example, ''%%var_dump()%%'' will output ''%%object%%'' instead of ''%%record%%''.
+=== isMutable() ===
+The ''%%isMutable()%%'' method is used to determine if a record has been made mutable via ''%%makeMutable()%%'' or otherwise not yet finalized.
+=== Custom deserialization example ===
+In cases where custom deserialization is required, a developer can use ''%%ReflectionRecord%%'' to manually construct a new instance of a record.
+<code php>
+record Seconds(int $seconds);
+$example = &Seconds(5);
+$reflector = new ReflectionRecord(Seconds::class);
+$expiration = $reflector->newInstanceWithoutConstructor(); // this is a mutable object
+$expiration->seconds = 5;
+assert($example !== $expiration); // true
+$expiration = $reflector->finalizeRecord($expiration);
+assert($example === $expiration); // true
+</code>
-=== var_dump ===
+==== var_dump ====
-Calling ''var_dump'' will look much like it does for objects, but instead of ''object'' it will say ''record''.
+When passed an instance of a record the ''%%var_dump()%%'' function will output the same as if an equivalent object were passed — e.g., both having the same properties — except the output generated will replace the prefix text "object" with the text "record."
-<code>
+<code txt>
 record(Point)#1 (2) {
   ["x"]=>
@@ Line 179: / Line 550: @@
 ==== Considerations for implementations ====
-A ''record'' cannot be named after an existing ''record'', ''class'' or ''function''. This is because defining a ''record'' creates both a ''class'' and a ''function'' with the same name.
+A ''%%record%%'' cannot share its name with an existing ''%%record%%'', ''%%class%%'', ''%%interface%%'', ''%%trait%%'', or ''%%function%%'', just like a class.
-==== Auto loading ====
+==== Autoloading ====
-As invoking a record value by its name looks remarkably similar to calling a function, and PHP has no function autoloader, auto loading will not be supported in this implementation. If function auto loading were to be implemented in the future, an autoloader could locate the ''record'' and autoload it. The author of this RFC strongly encourages someone to put forward a function auto loading RFC if auto loading is desired for records.
+Records will be autoloaded in the same way as classes.
+==== New Functions ====
+  * ''%%record_exists%%'' will return ''%%true%%'' if a record exists and ''%%false%%'' otherwise. It has the same signature as ''%%class_exists%%''.
 ===== Backward Incompatible Changes =====
-No backward incompatible changes.
+To avoid conflicts with existing code, the ''%%record%%'' keyword will be handled similarly to ''%%enum%%'' to prevent backward compatibility issues.
+Since ''%%&%%'' is currently a syntax error when prefixed on a function call, it will be used to denote a record instantiation.
 ===== Proposed PHP Version(s) =====
 PHP 8.5
 ===== RFC Impact =====
 ==== To SAPIs ====
 N/A
 ==== To Existing Extensions ====
 N/A
 ==== To Opcache ====
 Unknown.
 ==== New Constants ====
 None
 ==== php.ini Defaults ====
 None
 ===== Open Issues =====
-Todo
+  * Distill how CoW works, exactly.
+  * Address conflict with ''%%&%%'' syntax: https://3v4l.org/CE5rt
 ===== Unaffected PHP Functionality =====
@@ Line 216: / Line 603: @@
 ===== Future Scope =====
+  * Records for "record-like" types, such as DateTime, DateInterval, and others.
+  * Short definition syntax for classes
 ===== Proposed Voting Choices =====
-Include these so readers know where you are heading and can discuss the proposed voting options.
+/3 majority.
 ===== Patches and Tests =====
@@ Line 225: / Line 615: @@
 ===== Implementation =====
-After the project is implemented, this section should contain
-  - the version(s) it was merged into
+To be completed during a later phase of discussion.
-  - a link to the git commit(s)
-  - a link to the PHP manual entry for the feature
-  - a link to the language specification section (if any)
 ===== References =====
-Links to external references, discussions or RFCs
+  * [[https://en.wikipedia.org/wiki/Value_semantics|Value semantics]]
 ===== Rejected Features =====
-Keep this updated with features that were discussed on the mail lists.
+TBD

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