Compile time generics W.I.P.

Author: Girgias

Zend/tests/type_declarations/abstract_generics/abstract_generic_001.phpt

@@ -0,0 +1,31 @@
+--TEST--
+Abstract generic types basic
+--FILE--
+<?php
+
+interface I<T> {
+    public function foo(T $param): T;
+}
+
+class CS implements I<string> {
+    public function foo(string $param): string {
+        return $param . '!';
+    }
+}
+
+class CI implements I<int> {
+    public function foo(int $param): int {
+        return $param + 42;
+    }
+}
+
+$cs = new CS();
+var_dump($cs->foo("Hello"));
+
+$ci = new CI();
+var_dump($ci->foo(5));
+
+?>
+--EXPECT--
+string(6) "Hello!"
+int(47)

Zend/tests/type_declarations/abstract_generics/big_example.phpt

@@ -0,0 +1,100 @@
+--TEST--
+Concrete example of using AT
+--CREDITS--
+Levi Morrison
+--FILE--
+<?php declare(strict_types=1);
+
+namespace Sequence;
+
+// No null. This is probably going to be painful, but let's try it.
+interface Sequence<Item : object|array|string|float|int|bool>
+{
+    function next(): ?Item;
+
+    /**
+     * @param callable(Item, Item): Item $f
+     * @return ?Item
+     */
+    function reduce(callable $f): ?Item;
+}
+
+final class StringTablePair
+{
+    public function __construct(
+        public readonly string $string,
+        public readonly int $id,
+    ) {}
+}
+
+final class StringTableSequence implements Sequence<StringTablePair>
+{
+    private array $strings;
+
+    public function __construct(StringTable $string_table) {
+        $this->strings = $string_table->to_assoc_array();
+    }
+
+    function next(): ?StringTablePair
+    {
+        $key = \array_key_first($this->strings);
+        if (!isset($key)) {
+            return null;
+        }
+        $value = \array_shift($this->strings);
+        return new StringTablePair($key, $value);
+    }
+
+    /**
+     * @param callable(Item, Item): Item $f
+     * @return ?Item
+     */
+    function reduce(callable $f): ?StringTablePair
+    {
+        $reduction = $this->next();
+        if (!isset($reduction)) {
+            return null;
+        }
+
+        while (($next = $this->next()) !== null) {
+            $reduction = $f($reduction, $next);
+        }
+        return $reduction;
+    }
+}
+
+final class StringTable
+{
+    private array $strings = ["" => 0];
+
+    public function __construct() {}
+
+    public function offsetGet(string $offset): int
+    {
+        return $this->strings[$offset] ?? throw new \Exception();
+    }
+
+    public function offsetExists(string $offset): bool
+    {
+        return \isset($this->strings[$offset]);
+    }
+
+    public function intern(string $str): int
+    {
+        return $this->strings[$str]
+            ?? ($this->strings[$str] = \count($this->strings));
+    }
+
+    public function to_sequence(): StringTableSequence
+    {
+        return new StringTableSequence($this);
+    }
+
+    public function to_assoc_array(): array {
+        return $this->strings;
+    }
+}
+
+?>
+--EXPECTF--
+Fatal error: Generic type cannot be part of a union type in %s on line %d

Zend/tests/type_declarations/abstract_generics/constraints/abstract_generic_type_with_constraint.phpt

@@ -0,0 +1,31 @@
+--TEST--
+Abstract generic type with a constraint
+--FILE--
+<?php
+
+interface I<T : int|string> {
+    public function foo(T $param): T;
+}
+
+class CS implements I<string> {
+    public function foo(string $param): string {
+        return $param . '!';
+    }
+}
+
+class CI implements I<int> {
+    public function foo(int $param): int {
+        return $param + 42;
+    }
+}
+
+$cs = new CS();
+var_dump($cs->foo("Hello"));
+
+$ci = new CI();
+var_dump($ci->foo(5));
+
+?>
+--EXPECT--
+string(6) "Hello!"
+int(47)

Zend/tests/type_declarations/abstract_generics/constraints/abstract_generic_type_with_constraint_failed.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Abstract generic type with a constraint that is not satisfied
+--FILE--
+<?php
+
+interface I<T : int|string> {
+    public function foo(T $param): T;
+}
+
+class C implements I<float> {
+    public function foo(float $param): float {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Bound type float is not a subtype of the constraint type string|int of generic type T of interface I in %s on line %d

Zend/tests/type_declarations/abstract_generics/constraints/errors/using_generic_type_as_constraint.phpt

@@ -0,0 +1,12 @@
+--TEST--
+Cannot use generic type as a constraint
+--FILE--
+<?php
+
+interface I<T1, T2 : T1> {
+    public function foo(T $param): T;
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot use generic parameter T1 to constrain generic parameter T2 in %s on line %d

Zend/tests/type_declarations/abstract_generics/constraints/errors/using_never_as_constraint.phpt

@@ -0,0 +1,12 @@
+--TEST--
+Cannot use never as a constraint
+--FILE--
+<?php
+
+interface I<T : never> {
+    public function foo(T $param): T;
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot use static, void, or never to constrain generic parameter T in %s on line %d

Zend/tests/type_declarations/abstract_generics/constraints/errors/using_static_as_constraint.phpt

@@ -0,0 +1,12 @@
+--TEST--
+Cannot use void as a constraint
+--FILE--
+<?php
+
+interface I<T : static> {
+    public function foo(T $param): T;
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot use static, void, or never to constrain generic parameter T in %s on line %d

Zend/tests/type_declarations/abstract_generics/constraints/errors/using_void_as_constraint.phpt

@@ -0,0 +1,12 @@
+--TEST--
+Cannot use void as a constraint
+--FILE--
+<?php
+
+interface I<T : void> {
+    public function foo(T $param): T;
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot use static, void, or never to constrain generic parameter T in %s on line %d

Zend/tests/type_declarations/abstract_generics/constraints/extended_interface_abstract_generic_constraint_failure.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Abstract generic type behaviour in extended interface violates type constraint
+--FILE--
+<?php
+
+interface I<T : int|string|(Traversable&Countable)> {
+    public function foo(T $param): T;
+}
+
+interface I2<T> extends I<T> {
+    public function bar(int $o, T $param): T;
+}
+
+class C implements I2<string> {
+    public function foo(string $param): string {}
+    public function bar(int $o, float $param): float {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Constraint type mixed of generic type T of interface I2 is not a subtype of the constraint type (Traversable&Countable)|string|int of generic type T of interface I in %s on line %d

Zend/tests/type_declarations/abstract_generics/constraints/implicit_interface_different_bound_types.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Implicit interface inheritance with different bound types
+--FILE--
+<?php
+
+interface I1<T> {
+    public function foo(T $param): T;
+}
+
+interface I2<T> extends I1<T> {
+    public function bar(int $o, T $param): T;
+}
+
+class C implements I2<float>, I1<string> {
+    public function foo(float $param): float {}
+    public function bar(int $o, float $param): float {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Bound type T for interface I1 implemented explicitly in C with type string must match the implicitly bound type float from interface I2 in %s on line %d