Fix phpstan/phpstan#14459: Null coalescing operator does not report redundant left operand when always defined (#5452)

Co-authored-by: ondrejmirtes <104888+ondrejmirtes@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: 3 people

src/Analyser/MutatingScope.php

@@ -1068,15 +1068,18 @@ public function issetCheck(Expr $expr, callable $typeCallback, ?bool $result = n
 
 			if ($propertyReflection->hasNativeType() && !$propertyReflection->isVirtual()->yes()) {
 				if (!$this->hasExpressionType($expr)->yes()) {
-					if ($expr instanceof Node\Expr\PropertyFetch) {
-						return $this->issetCheckUndefined($expr->var);
-					}
+					$nativeReflection = $propertyReflection->getNativeReflection();
+					if ($nativeReflection === null || !$nativeReflection->isPromoted() || (!$nativeReflection->isReadOnly() && !$nativeReflection->isHooked())) {
+						if ($expr instanceof Node\Expr\PropertyFetch) {
+							return $this->issetCheckUndefined($expr->var);
+						}
 
-					if ($expr->class instanceof Expr) {
-						return $this->issetCheckUndefined($expr->class);
-					}
+						if ($expr->class instanceof Expr) {
+							return $this->issetCheckUndefined($expr->class);
+						}
 
-					return null;
+						return null;
+					}
 				}
 			}
 

src/Rules/IssetCheck.php

@@ -183,7 +183,11 @@ static function (Type $type) use ($typeMessageCallback): ?string {
 
 				if (!$scope->hasExpressionType($expr)->yes()) {
 					$nativeReflection = $propertyReflection->getNativeReflection();
-					if ($nativeReflection !== null && !$nativeReflection->getNativeReflection()->hasDefaultValue()) {
+					if (
+						$nativeReflection !== null
+						&& !$nativeReflection->getNativeReflection()->hasDefaultValue()
+						&& (!$nativeReflection->isPromoted() || (!$nativeReflection->isReadOnly() && !$nativeReflection->isHooked()))
+					) {
 						return null;
 					}
 				}

tests/PHPStan/Rules/Variables/NullCoalesceRuleTest.php

@@ -392,6 +392,28 @@ public function testBug14458(): void
 		$this->analyse([__DIR__ . '/data/bug-14458.php'], []);
 	}
 
+	#[RequiresPhp('>= 8.1')]
+	public function testBug14459(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-14459.php'], [
+			[
+				'Property Bug14459\Dto::$policyholderId (stdClass) on left side of ?? is not nullable.',
+				34,
+			],
+		]);
+	}
+
+	#[RequiresPhp('>= 8.4')]
+	public function testBug14459Hooked(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-14459-hooked.php'], [
+			[
+				'Property Bug14459Hooked\DtoHooked::$policyholderId (stdClass) on left side of ?? is not nullable.',
+				21,
+			],
+		]);
+	}
+
 	public function testBug14393(): void
 	{
 		$this->analyse([__DIR__ . '/data/bug-14393.php'], [

tests/PHPStan/Rules/Variables/data/bug-14459-hooked.php

@@ -0,0 +1,29 @@
+<?php // lint >= 8.4
+
+declare(strict_types = 1);
+
+namespace Bug14459Hooked;
+
+final class DtoHooked
+{
+	public function __construct(
+		public \stdClass $policyholderId {
+			set => $value;
+		},
+		public ?\stdClass $nullablePolicyholderId {
+			set => $value;
+		},
+	) {}
+}
+
+function testHooked(DtoHooked $dto): \stdClass
+{
+	$x = $dto->policyholderId ?? new \stdClass();
+	return $x;
+}
+
+function testHookedNullable(DtoHooked $dto): \stdClass
+{
+	$x = $dto->nullablePolicyholderId ?? new \stdClass();
+	return $x;
+}

tests/PHPStan/Rules/Variables/data/bug-14459.php

@@ -0,0 +1,54 @@
+<?php // lint >= 8.1
+
+declare(strict_types = 1);
+
+namespace Bug14459;
+
+final class Dto
+{
+	public function __construct(
+		public readonly \stdClass $payerId,
+		public readonly \stdClass $policyholderId,
+		public readonly ?\stdClass $nullablePolicyholderId,
+	) {}
+}
+
+final class DtoNonReadonly
+{
+	public function __construct(
+		public \stdClass $payerId,
+	) {}
+}
+
+class DtoNonPromotedReadonly
+{
+	public readonly \stdClass $payerId;
+
+	public function __construct(\stdClass $payerId) {
+		$this->payerId = $payerId;
+	}
+}
+
+function test(Dto $dto): \stdClass
+{
+	$x = $dto->policyholderId ?? $dto->payerId;
+	return $x;
+}
+
+function testNullable(Dto $dto): \stdClass
+{
+	$x = $dto->nullablePolicyholderId ?? $dto->payerId;
+	return $x;
+}
+
+function testNonReadonly(DtoNonReadonly $dto): \stdClass
+{
+	$x = $dto->payerId ?? new \stdClass();
+	return $x;
+}
+
+function testNonPromotedReadonly(DtoNonPromotedReadonly $dto): \stdClass
+{
+	$x = $dto->payerId ?? new \stdClass();
+	return $x;
+}