phpunit/code/inheritance_error_generator_return_widened.php

@@ -0,0 +1,14 @@
+<?php
+
+interface GeneratorReturnContract
+{
+    public function values(): \Generator;
+}
+
+class GeneratorReturnImplementation implements GeneratorReturnContract
+{
+    public function values(): iterable
+    {
+        yield 1;
+    }
+}

phpunit/src/InheritanceErrorTest.php

@@ -73,6 +73,11 @@ class InheritanceErrorTest extends TestCase
         $this->exec('must be compatible', 'inheritance_error_return_never_widened.php');
     }
 
+    public function testGeneratorReturnTypeCannotBeWidenedToIterable(): void
+    {
+        $this->exec('must be compatible', 'inheritance_error_generator_return_widened.php');
+    }
+
     public function testIntersectionReturnTypeCanNarrowToIntersectionOrConcreteSubtype(): void
     {
         $this->assertCompiles('return_type_covariance_intersection.php');

src/Entity/FunctionDef.php

@@ -74,6 +74,20 @@ class FunctionDef
     /** Original union/nullable return type AST node. */
     public ?NodeAbstract $returnTypeNode = null;
 
+    /**
+     * Source-level return type declared on a generator method, preserved after
+     * `prepareGeneratorFunction()` neutralizes the runtime return type. A
+     * generator actually returns a `\FiberGenerator` (which implements
+     * `Iterator`), so the C++ return type and runtime type check are left
+     * neutral; this copy is only used by interface/abstract return-type
+     * covariance checks so a generator method can still satisfy a contract such
+     * as `: \Generator`.
+     */
+    public ?string $declaredReturnType = null;
+    public string $declaredReturnClass = '';
+    public ?array $declaredReturnTypeCheck = null;
+    public string $declaredReturnTypeStr = '';
+
     public function __construct(string $name, string $returnType, string $namespace)
     {
         $this->name = $name;

src/Generator/FiberGenerator.php

@@ -72,6 +72,18 @@ trait FiberGenerator
         if (!$this->generatorReturnTypeAcceptsFiber($v->returnType)) {
             $this->fatalError($v, 'Generator return type must accept \\FiberGenerator; use Iterator, Traversable, iterable, object, mixed, or omit the return type');
         }
+        // Preserve the source-level declared return type before neutralizing the
+        // runtime return type. The override compatibility check still needs it so
+        // a generator method can satisfy an interface/abstract contract such as
+        // `: \Generator` (the runtime object is a `\FiberGenerator`, not a Zend
+        // `Generator`, so the C++ return type and runtime check stay neutral).
+        if ($v->returnType !== null) {
+            $declared = $this->buildTypeCheckFromNode($v->returnType);
+            $functionDef->declaredReturnTypeCheck = $declared['check'] ?: null;
+        }
+        $functionDef->declaredReturnType = $functionDef->returnType;
+        $functionDef->declaredReturnClass = $functionDef->returnClass;
+        $functionDef->declaredReturnTypeStr = $functionDef->returnTypeStr;
         $functionDef->generator = true;
         $functionDef->returnType = Type::VAR;
         $functionDef->returnClass = '';
@@ -112,7 +124,11 @@ trait FiberGenerator
 
         [, $class] = $this->resolveTypeDecl($type, self::DECL_TYPE_OF_RETURN);
         $class = strtolower(ltrim($class, '\\'));
-        return in_array($class, ['iterator', 'traversable', 'fibergenerator'], true);
+        // `\Generator` is the return type PHP programmers naturally write for a
+        // generator. TypePHP generators actually return a `\FiberGenerator`, so
+        // accepting the declared `Generator` type keeps PHP source compatible
+        // while the runtime object remains a `\FiberGenerator`.
+        return in_array($class, ['iterator', 'traversable', 'fibergenerator', 'generator'], true);
     }
 
     protected function parseYieldExpr(Yield_ $expr): string

src/Translator.php

@@ -3745,21 +3745,34 @@ CODE;
 
     private function getReturnAcceptedTypes(FunctionDef $functionDef, string $declaringClass): array
     {
-        if (!empty($functionDef->returnTypeCheck)) {
+        $returnTypeCheck = $functionDef->generator
+            ? $functionDef->declaredReturnTypeCheck
+            : $functionDef->returnTypeCheck;
+        $returnType = $functionDef->generator
+            ? $functionDef->declaredReturnType
+            : $functionDef->returnType;
+        $returnClass = $functionDef->generator
+            ? $functionDef->declaredReturnClass
+            : $functionDef->returnClass;
+        $returnTypeStr = $functionDef->generator
+            ? $functionDef->declaredReturnTypeStr
+            : $functionDef->returnTypeStr;
+
+        if (!empty($returnTypeCheck)) {
             return array_map(
                 fn (array $type): array => $this->normalizeReturnTypeEntry($type, $declaringClass),
-                $functionDef->returnTypeCheck,
+                $returnTypeCheck,
             );
         }
 
         if ($functionDef->returnTypeKeyword === 'static') {
             return [['kind' => 'isStatic', 'class' => $declaringClass]];
         }
-        if ($functionDef->returnType === Type::OBJECT && $functionDef->returnClass !== '') {
+        if ($returnType === Type::OBJECT && $returnClass !== '') {
-            return [['kind' => 'instanceof', 'class' => $functionDef->returnClass]];
+            return [['kind' => 'instanceof', 'class' => $returnClass]];
         }
 
-        $declaredType = strtolower($functionDef->returnTypeStr);
+        $declaredType = strtolower($returnTypeStr);
         return match ($declaredType) {
             'mixed' => [['kind' => 'isMixed']],
             'never' => [['kind' => 'isNever']],
@@ -3770,7 +3783,7 @@ CODE;
             'callable' => [['kind' => 'callable']],
             'iterable' => [['kind' => 'iterable']],
             'object' => [['kind' => 'isObject']],
-            default => match ($functionDef->returnType) {
+            default => match ($returnType) {
                 Type::INT => [['kind' => 'isInt']],
                 Type::FLOAT => [['kind' => 'isFloat']],
                 Type::BOOL => [['kind' => 'isBool']],

tests/compiler/generator/generator-foreach-yield.phpt

@@ -0,0 +1,57 @@
+--TEST--
+generator re-yielding array elements via foreach with \Generator return type
+--FILE--
+<?php
+
+function main()
+{
+    $g = test([1, 2, 3]);
+    var_dump($g);
+    foreach ($g as $value)
+    {
+        var_dump($value);
+    }
+}
+
+function test(array $array): \Generator
+{
+    foreach ($array as $value)
+    {
+        yield $value;
+    }
+}
+
+// main();
+?>
+--EXPECTF--
+object(FiberGenerator)#%d (9) {
+  ["callback":"FiberGenerator":private]=>
+  object(Closure)#%d (2) {
+    ["function"]=>
+    string(19) "stdClass::{closure}"
+    ["this"]=>
+    object(stdClass)#%d (1) {
+      ["box"]=>
+      resource(%d) of type (php::box)
+    }
+  }
+  ["fiber":"FiberGenerator":private]=>
+  NULL
+  ["current":"FiberGenerator":private]=>
+  NULL
+  ["key":"FiberGenerator":private]=>
+  NULL
+  ["valid":"FiberGenerator":private]=>
+  bool(false)
+  ["state":"FiberGenerator":private]=>
+  int(0)
+  ["yield_count":"FiberGenerator":private]=>
+  int(0)
+  ["next_index":"FiberGenerator":private]=>
+  int(0)
+  ["return_value":"FiberGenerator":private]=>
+  NULL
+}
+int(1)
+int(2)
+int(3)

tests/compiler/generator/generator-return-type-generator.phpt

@@ -0,0 +1,53 @@
+--TEST--
+generator return type accepts \Generator for methods, nullable and union variants
+--FILE--
+<?php
+
+class Box
+{
+    public function gen(array $array): \Generator
+    {
+        foreach ($array as $value) {
+            yield $value * 2;
+        }
+    }
+}
+
+function nullableGen(array $array): ?\Generator
+{
+    foreach ($array as $value) {
+        yield $value;
+    }
+}
+
+function unionGen(array $array): \Generator|\Iterator
+{
+    foreach ($array as $value) {
+        yield $value;
+    }
+}
+
+function main()
+{
+    $b = new Box();
+    foreach ($b->gen([1, 2, 3]) as $v) {
+        var_dump($v);
+    }
+    $g = nullableGen([4, 5]);
+    foreach ($g as $v) {
+        var_dump($v);
+    }
+    $u = unionGen([6, 7]);
+    foreach ($u as $v) {
+        var_dump($v);
+    }
+}
+?>
+--EXPECT--
+int(2)
+int(4)
+int(6)
+int(4)
+int(5)
+int(6)
+int(7)

tests/compiler/generator/interface-return-type-variants.phpt

@@ -0,0 +1,96 @@
+--TEST--
+generator methods implementing interfaces with iterable, nullable and union return types
+--FILE--
+<?php
+interface GenInterface
+{
+    public function gen(array $array): \Generator;
+}
+
+interface IterableInterface
+{
+    public function it(array $array): iterable;
+
+    public function narrowed(array $array): iterable;
+}
+
+interface NullableInterface
+{
+    public function nullable(array $array): ?\Generator;
+}
+
+interface UnionInterface
+{
+    public function union(array $array): \Generator|\Iterator;
+}
+
+class Box implements GenInterface, IterableInterface, NullableInterface, UnionInterface
+{
+    public function gen(array $array): \Generator
+    {
+        foreach ($array as $value) {
+            yield $value * 2;
+        }
+    }
+
+    public function it(array $array): iterable
+    {
+        foreach ($array as $value) {
+            yield $value;
+        }
+    }
+
+    public function narrowed(array $array): \Generator
+    {
+        foreach ($array as $value) {
+            yield $value;
+        }
+    }
+
+    public function nullable(array $array): ?\Generator
+    {
+        foreach ($array as $value) {
+            yield $value;
+        }
+    }
+
+    public function union(array $array): \Generator|\Iterator
+    {
+        foreach ($array as $value) {
+            yield $value;
+        }
+    }
+}
+
+function main()
+{
+    $box = new Box();
+    foreach ($box->gen([1, 2, 3]) as $v) {
+        var_dump($v);
+    }
+    foreach ($box->it([4, 5]) as $v) {
+        var_dump($v);
+    }
+    foreach ($box->narrowed([10, 11]) as $v) {
+        var_dump($v);
+    }
+    foreach ($box->nullable([6, 7]) as $v) {
+        var_dump($v);
+    }
+    foreach ($box->union([8, 9]) as $v) {
+        var_dump($v);
+    }
+}
+?>
+--EXPECT--
+int(2)
+int(4)
+int(6)
+int(4)
+int(5)
+int(10)
+int(11)
+int(6)
+int(7)
+int(8)
+int(9)

tests/compiler/generator/interface-return-type.phpt

@@ -0,0 +1,38 @@
+--TEST--
+generator method implementing an interface that declares \Generator return type
+--FILE--
+<?php
+interface T
+{
+    public function test(array $array): \Generator;
+}
+
+class TestClass implements T
+{
+    public function test(array $array): \Generator
+    {
+        foreach ($array as $value) {
+            yield $value;
+        }
+    }
+}
+
+function main()
+{
+    $test = new TestClass;
+    $g = $test->test([1, 2, 3]);
+    // TypePHP generators return a \FiberGenerator which implements Iterator
+    // but is NOT the Zend \Generator class.
+    var_dump($g instanceof \Generator);
+    var_dump($g instanceof \Iterator);
+    foreach ($g as $value) {
+        var_dump($value);
+    }
+}
+?>
+--EXPECT--
+bool(false)
+bool(true)
+int(1)
+int(2)
+int(3)