[RFC] Primary Constructors

Zend/tests/primary_ctor/attributes.phpt

@@ -0,0 +1,31 @@
+--TEST--
+Primary constructors: attributes apply to promoted parameters/properties
+--FILE--
+<?php
+#[Attribute(Attribute::TARGET_PARAMETER | Attribute::TARGET_PROPERTY)]
+class Col {
+    public function __construct(public string $name) {}
+}
+
+/** @param int $id */
+class Row(
+    #[Col('id')] public int $id,
+) {}
+
+$class = new ReflectionClass(Row::class);
+var_dump($class->getDocComment());
+var_dump($class->getConstructor()->getDocComment());
+
+$param = $class->getConstructor()->getParameters()[0];
+var_dump($param->getAttributes()[0]->getName());
+var_dump($param->getAttributes()[0]->newInstance()->name);
+
+$prop = (new ReflectionProperty(Row::class, 'id'))->getAttributes()[0];
+var_dump($prop->newInstance()->name);
+?>
+--EXPECT--
+string(21) "/** @param int $id */"
+string(21) "/** @param int $id */"
+string(3) "Col"
+string(2) "id"
+string(2) "id"

Zend/tests/primary_ctor/basic.phpt

@@ -0,0 +1,25 @@
+--TEST--
+Primary constructors: basic promotion, defaults, named args
+--FILE--
+<?php
+class Point(public int $x, public int $y = 0) {
+    public function sum(): int { return $this->x + $this->y; }
+}
+
+$p = new Point(3);
+var_dump($p->x, $p->y, $p->sum());
+
+$p2 = new Point(x: 10, y: 20);
+var_dump($p2->sum());
+
+$r = new ReflectionMethod(Point::class, '__construct');
+var_dump($r->getNumberOfParameters());
+var_dump($r->isPublic());
+?>
+--EXPECT--
+int(3)
+int(0)
+int(3)
+int(30)
+int(2)
+bool(true)

Zend/tests/primary_ctor/docblock.phpt

@@ -0,0 +1,36 @@
+--TEST--
+Primary constructors: a class doc comment also applies to the synthesized constructor
+--FILE--
+<?php
+/** Doc for C */
+class C(public int $x) {}
+
+$rc = new ReflectionClass(C::class);
+var_dump($rc->getDocComment());
+var_dump($rc->getConstructor()->getDocComment());
+
+class D(public int $y) {}
+
+$rd = new ReflectionClass(D::class);
+var_dump($rd->getDocComment());
+var_dump($rd->getConstructor()->getDocComment());
+
+class E(
+    /** Doc for z */ public int $z,
+) {}
+
+$re = new ReflectionClass(E::class);
+var_dump($re->getDocComment());
+var_dump($re->getConstructor()->getDocComment());
+var_dump($re->getProperty('z')->getDocComment());
+?>
+--EXPECT--
+string(16) "/** Doc for C */"
+string(16) "/** Doc for C */"
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+string(16) "/** Doc for z */"
+--CREDITS--
+Robert Landers

Zend/tests/primary_ctor/error_anon_parent_args.phpt

@@ -0,0 +1,9 @@
+--TEST--
+Primary constructors: anonymous classes cannot forward arguments to the parent
+--FILE--
+<?php
+class Base { public function __construct(public int $id) {} }
+$o = new class extends Base(5) {};
+?>
+--EXPECTF--
+Fatal error: Cannot pass arguments to the parent constructor without a primary constructor in %s on line %d

Zend/tests/primary_ctor/error_enum_trait.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Primary constructors: not allowed on enums or traits
+--FILE--
+<?php
+function tryCompile(string $code): void {
+    try {
+        eval($code);
+    } catch (\ParseError $e) {
+        echo $e->getMessage(), "\n";
+    }
+}
+
+tryCompile('enum E(public int $x) { case A; }');
+tryCompile('trait T(public int $x) {}');
+?>
+--EXPECT--
+syntax error, unexpected token "(", expecting "{"
+syntax error, unexpected token "(", expecting "{"

Zend/tests/primary_ctor/error_interface.phpt

@@ -0,0 +1,8 @@
+--TEST--
+Primary constructors: not allowed on interfaces
+--FILE--
+<?php
+interface I(public int $x) {}
+?>
+--EXPECTF--
+Parse error: syntax error, unexpected token "(", expecting "{" in %s on line %d

Zend/tests/primary_ctor/error_parent_args_no_primary.phpt

@@ -0,0 +1,9 @@
+--TEST--
+Primary constructors: parent constructor arguments require a primary constructor
+--FILE--
+<?php
+class Base { public function __construct(public int $id) {} }
+class Sub extends Base(5) {}
+?>
+--EXPECTF--
+Fatal error: Cannot pass arguments to the parent constructor without a primary constructor in %s on line %d

Zend/tests/primary_ctor/error_parent_empty_no_primary.phpt

@@ -0,0 +1,9 @@
+--TEST--
+Primary constructors: parent constructor call requires a primary constructor
+--FILE--
+<?php
+class Base { public function __construct() {} }
+class Sub extends Base() {}
+?>
+--EXPECTF--
+Fatal error: Cannot call the parent constructor without a primary constructor in %s on line %d

Zend/tests/primary_ctor/error_readonly_hook.phpt

@@ -0,0 +1,12 @@
+--TEST--
+Primary constructors: hooked promoted properties cannot be readonly
+--FILE--
+<?php
+readonly class Temperature(
+    public float $celsius {
+        set { $this->celsius = $value; }
+    }
+) {}
+?>
+--EXPECTF--
+Fatal error: Hooked properties cannot be readonly in %s on line %d

Zend/tests/primary_ctor/error_redeclare_construct.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Primary constructors: cannot also declare an explicit __construct()
+--FILE--
+<?php
+class Bad(public int $x) {
+    public function __construct(public int $x) {}
+}
+?>
+--EXPECTF--
+Fatal error: Cannot redeclare Bad::__construct() in %s on line %d

Zend/tests/primary_ctor/hook_cross_parameter_order_edge.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Primary constructors: promoted property hooks cannot read later promoted properties before initialization
+--FILE--
+<?php
+class Range(
+    public int $start {
+        set {
+            var_dump(isset($this->end));
+            var_dump($this->end);
+            $this->start = $value;
+        }
+    },
+    public int $end,
+) {}
+
+try {
+    new Range(1, 3);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+?>
+--EXPECT--
+bool(false)
+Typed property Range::$end must not be accessed before initialization

Zend/tests/primary_ctor/hook_cross_parameter_validation.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Primary constructors: later promoted property hooks can validate against earlier promoted properties
+--FILE--
+<?php
+class Range(
+    public int $start,
+    public int $end {
+        set {
+            if ($this->start > $value) {
+                throw new ValueError('start must precede end');
+            }
+            $this->end = $value;
+        }
+    }
+) {}
+
+$ok = new Range(1, 3);
+var_dump($ok);
+
+try {
+    new Range(3, 1);
+} catch (ValueError $e) {
+    echo $e->getMessage(), "\n";
+}
+?>
+--EXPECT--
+object(Range)#1 (2) {
+  ["start"]=>
+  int(1)
+  ["end"]=>
+  int(3)
+}
+start must precede end

Zend/tests/primary_ctor/hook_derived_state.phpt

@@ -0,0 +1,38 @@
+--TEST--
+Primary constructors: a later promoted property hook can initialize derived state
+--FILE--
+<?php
+class Range(
+    public int $start,
+    public int $end {
+        set {
+            if ($this->start > $value) {
+                throw new ValueError('start must precede end');
+            }
+            $this->end = $value;
+            $this->length = $value - $this->start;
+        }
+    }
+) {
+    public readonly int $length;
+}
+
+$range = new Range(2, 5);
+var_dump($range);
+
+try {
+    $range->length = 99;
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+?>
+--EXPECT--
+object(Range)#1 (3) {
+  ["start"]=>
+  int(2)
+  ["end"]=>
+  int(5)
+  ["length"]=>
+  int(3)
+}
+Cannot modify readonly property Range::$length

Zend/tests/primary_ctor/hook_validation.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Primary constructors: a set hook on a promoted parameter validates during construction
+--FILE--
+<?php
+class Temperature(
+    public float $celsius {
+        set {
+            if ($value < -273.15) {
+                throw new ValueError('below absolute zero');
+            }
+            $this->celsius = $value;
+        }
+    }
+) {}
+
+var_dump((new Temperature(20.0))->celsius);
+
+try {
+    new Temperature(-300.0);
+} catch (ValueError $e) {
+    echo $e->getMessage(), "\n";
+}
+?>
+--EXPECT--
+float(20)
+below absolute zero

Zend/tests/primary_ctor/parent_call_variants.phpt

@@ -0,0 +1,23 @@
+--TEST--
+Primary constructors: extends Base() calls parent, extends Base (no parens) does not
+--FILE--
+<?php
+class WithCtor {
+    public int $v = 0;
+    public function __construct() { echo "WithCtor::__construct\n"; $this->v = 7; }
+}
+
+class A(public int $x) extends WithCtor() {}
+$a = new A(1);
+var_dump($a->x, $a->v);
+
+class B(public int $x) extends WithCtor {}
+$b = new B(2);
+var_dump($b->x, $b->v);
+?>
+--EXPECT--
+WithCtor::__construct
+int(1)
+int(7)
+int(2)
+int(0)

Zend/tests/primary_ctor/parent_forwarding.phpt

@@ -0,0 +1,31 @@
+--TEST--
+Primary constructors: forward arguments to the parent constructor via extends
+--FILE--
+<?php
+abstract class Shape(protected string $name) {
+    abstract public function area(): float;
+    public function name(): string { return $this->name; }
+}
+
+final class Circle(
+    public readonly float $radius,
+    string $name = 'circle',
+) extends Shape($name) {
+    public function area(): float { return $this->radius ** 2 * 3; }
+}
+
+$c = new Circle(2.0);
+printf("%s %.1f\n", $c->name(), $c->area());
+
+$c2 = new Circle(1.0, 'unit');
+echo $c2->name(), "\n";
+
+$rp = (new ReflectionMethod(Circle::class, '__construct'))->getParameters();
+printf("radius promoted=%s, name promoted=%s\n",
+    $rp[0]->isPromoted() ? 'yes' : 'no',
+    $rp[1]->isPromoted() ? 'yes' : 'no');
+?>
+--EXPECT--
+circle 12.0
+unit
+radius promoted=yes, name promoted=no

Zend/tests/primary_ctor/promotion_and_bare.phpt

@@ -0,0 +1,31 @@
+--TEST--
+Primary constructors: explicit modifier promotes, bare parameter does not
+--FILE--
+<?php
+class Foo(
+    int $x,
+    public int $y,
+    private int $z = 9,
+) {
+    public function z(): int { return $this->z; }
+}
+
+$f = new Foo(1, 2);
+var_dump(property_exists($f, 'x'));
+var_dump(property_exists($f, 'y'));
+var_dump(property_exists($f, 'z'));
+var_dump($f->y, $f->z());
+
+foreach ((new ReflectionMethod(Foo::class, '__construct'))->getParameters() as $p) {
+    printf("%s promoted=%s\n", $p->getName(), $p->isPromoted() ? 'yes' : 'no');
+}
+?>
+--EXPECT--
+bool(false)
+bool(true)
+bool(true)
+int(2)
+int(9)
+x promoted=no
+y promoted=yes
+z promoted=yes