[PoC] Associated types

Zend/tests/type_declarations/associated/associated_001.phpt

@@ -0,0 +1,32 @@
+--TEST--
+Associated types basic
+--FILE--
+<?php
+
+interface I {
+    type T;
+    public function foo(T $param): T;
+}
+
+class CS implements I {
+    public function foo(string $param): string {
+        return $param . '!';
+    }
+}
+
+class CI implements I {
+    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/associated/associated_type_cannot_be_in_intersection1.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Associated type cannot be in intersection (simple intersection with class type)
+--FILE--
+<?php
+
+interface I {
+    type T;
+    public function foo(T&Traversable $param): T&Traversable;
+}
+
+?>
+--EXPECTF--
+Fatal error: Associated type cannot be part of an intersection type in %s on line %d

Zend/tests/type_declarations/associated/associated_type_cannot_be_in_intersection2.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Associated type cannot be in intersection (DNF type)
+--FILE--
+<?php
+
+interface I {
+    type T;
+    public function foo(stdClass|(T&Traversable) $param): stdClass|(T&Traversable);
+}
+
+?>
+--EXPECTF--
+Fatal error: Associated type cannot be part of an intersection type in %s on line %d

Zend/tests/type_declarations/associated/associated_type_cannot_be_in_union1.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Associated type cannot be in union (simple union with built-in type)
+--FILE--
+<?php
+
+interface I {
+    type T;
+    public function foo(T|int $param): T|int;
+}
+
+?>
+--EXPECTF--
+Fatal error: Associated type cannot be part of a union type in %s on line %d

Zend/tests/type_declarations/associated/associated_type_cannot_be_in_union2.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Associated type cannot be in union (simple union with class type)
+--FILE--
+<?php
+
+interface I {
+    type T;
+    public function foo(T|stdClass $param): T|stdClass;
+}
+
+?>
+--EXPECTF--
+Fatal error: Associated type cannot be part of a union type in %s on line %d

Zend/tests/type_declarations/associated/associated_type_cannot_be_in_union3.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Associated type cannot be in union (DNF type)
+--FILE--
+<?php
+
+interface I {
+    type T;
+    public function foo(T|(Traversable&Countable) $param): T|(Traversable&Countable);
+}
+
+?>
+--EXPECTF--
+Fatal error: Associated type cannot be part of a union type in %s on line %d

Zend/tests/type_declarations/associated/associated_type_in_class.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Associated types in class is invalid
+--FILE--
+<?php
+
+class C {
+    type T;
+    public function foo(T $param): T;
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot use associated types outside of interfaces, used in C in %s on line %d

Zend/tests/type_declarations/associated/associated_type_in_trait.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Associated types in trait is invalid
+--FILE--
+<?php
+
+trait C {
+    type T;
+    public function foo(T $param): T;
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot use associated types outside of interfaces, used in C in %s on line %d

Zend/tests/type_declarations/associated/associated_type_with_constraint.phpt

@@ -0,0 +1,32 @@
+--TEST--
+Associated type with a constraint
+--FILE--
+<?php
+
+interface I {
+    type T : int|string;
+    public function foo(T $param): T;
+}
+
+class CS implements I {
+    public function foo(string $param): string {
+        return $param . '!';
+    }
+}
+
+class CI implements I {
+    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/associated/associated_type_with_constraint_failed.phpt

@@ -0,0 +1,17 @@
+--TEST--
+Associated type with a constraint that is not satisfied
+--FILE--
+<?php
+
+interface I {
+    type T : int|string;
+    public function foo(T $param): T;
+}
+
+class C implements I {
+    public function foo(float $param): float {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Declaration of C::foo(float $param): float must be compatible with I::foo(T<string|int> $param): T<string|int> in %s on line %d

Zend/tests/type_declarations/associated/extended_interface_associated_type_redeclared.phpt

@@ -0,0 +1,23 @@
+--TEST--
+Associated type behaviour in extended interface
+--FILE--
+<?php
+
+interface I {
+    type T : int|string;
+    public function foo(T $param): T;
+}
+
+interface I2 extends I {
+    type T;
+    public function bar(int $o, T $param): T;
+}
+
+class C implements I2 {
+    public function foo(string $param): string {}
+    public function bar(int $o, float $param): float {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot redeclare associated type T in interface I2 inherited from interface I in %s on line %d

Zend/tests/type_declarations/associated/extended_interface_associated_types.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Associated type behaviour in extended interface
+--FILE--
+<?php
+
+interface I {
+    type T : int|string|(Traversable&Countable);
+    public function foo(T $param): T;
+}
+
+interface I2 extends I {
+    public function bar(int $o, T $param): T;
+}
+
+class C implements I2 {
+    public function foo(string $param): string {}
+    public function bar(int $o, float $param): float {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Declaration of C::bar(int $o, float $param): float must be compatible with I2::bar(int $o, T $param): T in %s on line %d

Zend/tests/type_declarations/associated/extended_interface_new_associated_types.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Associated type behaviour in extended interface
+--FILE--
+<?php
+
+interface I {
+    type T : int|string|(Traversable&Countable);
+    public function foo(T $param): T;
+}
+
+interface I2 extends I {
+    type T2 : float|bool|stdClass;
+    public function bar(T2 $o, T $param): T2;
+}
+
+class C implements I2 {
+    public function foo(string $param): string {}
+    public function bar(float $o, string $param): float {}
+}
+
+// TODO: Ideally error message would be:
+//Fatal error: Declaration of C::bar(float $o, string $param): float must be compatible with I2::bar(T2<stdClass|float|bool> $o, T<(Traversable&Countable)|int|string> $param): T2<stdClass|float|bool> in %s on line %d
+//Improve zend_append_type_hint()?
+?>
+--EXPECTF--
+Fatal error: Declaration of C::bar(float $o, string $param): float must be compatible with I2::bar(T2<stdClass|float|bool> $o, T $param): T2<stdClass|float|bool> in %s on line %d

Zend/tests/type_declarations/associated/multiple_associated_type.phpt

@@ -0,0 +1,74 @@
+--TEST--
+Multiple associated types
+--FILE--
+<?php
+
+interface I {
+    type K;
+    type V;
+    public function set(K $key, V $value): void;
+    public function get(K $key): V;
+}
+
+class C1 implements I {
+    public array $a = [];
+    public function set(int $key, string $value): void {
+        $this->a[$key] = $value . '!';
+    }
+    public function get(int $key): string {
+        return $this->a[$key];
+    }
+}
+
+class C2 implements I {
+    public array $a = [];
+    public function set(string $key, object $value): void {
+        $this->a[$key] = $value;
+    }
+    public function get(string $key): object {
+        return $this->a[$key];
+    }
+}
+
+$c1 = new C1();
+$c1->set(5, "Hello");
+var_dump($c1->a);
+var_dump($c1->get(5));
+
+$c2 = new C2();
+$c2->set('C1', $c1);
+var_dump($c2->a);
+var_dump($c2->get('C1'));
+
+try {
+    $c1->set('blah', "Hello");
+} catch (\Throwable $e) {
+    echo $e::class, ': ', $e->getMessage(), PHP_EOL;
+}
+
+
+?>
+--EXPECTF--
+array(1) {
+  [5]=>
+  string(6) "Hello!"
+}
+string(6) "Hello!"
+array(1) {
+  ["C1"]=>
+  object(C1)#1 (1) {
+    ["a"]=>
+    array(1) {
+      [5]=>
+      string(6) "Hello!"
+    }
+  }
+}
+object(C1)#1 (1) {
+  ["a"]=>
+  array(1) {
+    [5]=>
+    string(6) "Hello!"
+  }
+}
+TypeError: C1::set(): Argument #1 ($key) must be of type int, string given, called in %s on line %d

Zend/tests/type_declarations/associated/repeated_associated_type.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Repeated associated type
+--FILE--
+<?php
+
+interface I {
+    type T;
+    type T;
+    public function foo(T $param): T;
+}
+
+class C implements I {
+    public function foo(string $param): string {}
+}
+
+?>
+--EXPECTF--
+Fatal error: Cannot have two associated types with the same name "T" in %s on line %d

Zend/zend.c

@@ -732,6 +732,7 @@ static void compiler_globals_ctor(zend_compiler_globals *compiler_globals) /* {{
 
 	compiler_globals->script_encoding_list = NULL;
 	compiler_globals->current_linking_class = NULL;
+	compiler_globals->bound_associated_types = NULL;
 
 	/* Map region is going to be created and resized at run-time. */
 	compiler_globals->map_ptr_real_base = NULL;

Zend/zend.h

@@ -218,6 +218,9 @@ struct _zend_class_entry {
 	zend_trait_precedence **trait_precedences;
 	HashTable *attributes;
 
+	/* Only for interfaces */
+	HashTable *associated_types;
+
 	uint32_t enum_backing_type;
 	HashTable *backed_enum_table;
 

Zend/zend_ast.c

@@ -2664,6 +2664,16 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 			smart_str_appends(str, ": ");
 			ast = ast->child[1];
 			goto tail_call;
+		case ZEND_AST_ASSOCIATED_TYPE:
+			smart_str_appends(str, "type ");
+			zend_ast_export_name(str, ast->child[0], 0, indent);
+			if (ast->child[1]) {
+				smart_str_appends(str, " : ");
+				smart_str_appends(str, " : ");
+				zend_ast_export_type(str, ast->child[1], indent);
+			}
+			smart_str_appendc(str, ';');
+		break;
 
 		/* 3 child nodes */
 		case ZEND_AST_METHOD_CALL:

Zend/zend_ast.h

@@ -154,6 +154,7 @@ enum _zend_ast_kind {
 	ZEND_AST_MATCH_ARM,
 	ZEND_AST_NAMED_ARG,
 	ZEND_AST_PARENT_PROPERTY_HOOK_CALL,
+	ZEND_AST_ASSOCIATED_TYPE,
 
 	/* 3 child nodes */
 	ZEND_AST_METHOD_CALL = 3 << ZEND_AST_NUM_CHILDREN_SHIFT,