Fix internal error when using first class callable with NullsafeMethodCall

src/Analyser/NodeScopeResolver.php

@@ -101,6 +101,7 @@
 use PHPStan\Node\MethodCallableNode;
 use PHPStan\Node\MethodReturnStatementsNode;
 use PHPStan\Node\NoopExpressionNode;
+use PHPStan\Node\NullsafeMethodCallOnFirstClassCallableNode;
 use PHPStan\Node\PropertyAssignNode;
 use PHPStan\Node\PropertyHookReturnStatementsNode;
 use PHPStan\Node\PropertyHookStatementNode;
@@ -2755,6 +2756,11 @@ public function processExprNode(
 				$newExpr = new FunctionCallableNode($expr->name, $expr);
 			} elseif ($expr instanceof MethodCall) {
 				$newExpr = new MethodCallableNode($expr->var, $expr->name, $expr);
+			} elseif ($expr instanceof Expr\NullsafeMethodCall) {
+				// $foo?->bar(...) is a fatal error in PHP ("Cannot combine nullsafe
+				// operator with Closure creation"), but it must not crash the analyser.
+				// The error is reported by NullsafeFirstClassCallableRule.
+				$newExpr = new NullsafeMethodCallOnFirstClassCallableNode($expr->var, $expr->name, $expr);
 			} elseif ($expr instanceof StaticCall) {
 				$newExpr = new StaticMethodCallableNode($expr->class, $expr->name, $expr);
 			} elseif ($expr instanceof New_ && !$expr->class instanceof Class_) {

src/Node/NullsafeMethodCallOnFirstClassCallableNode.php

@@ -0,0 +1,61 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Node;
+
+use Override;
+use PhpParser\Node\Expr;
+use PhpParser\Node\Identifier;
+
+/**
+ * Represents `$foo?->bar(...)` - combining the nullsafe operator with the
+ * first-class callable syntax. This is a fatal error in PHP ("Cannot combine
+ * nullsafe operator with Closure creation"), reported by NullsafeFirstClassCallableRule.
+ *
+ * @api
+ */
+final class NullsafeMethodCallOnFirstClassCallableNode extends Expr implements VirtualNode
+{
+
+	public function __construct(
+		private Expr $var,
+		private Identifier|Expr $name,
+		private Expr\NullsafeMethodCall $originalNode,
+	)
+	{
+		parent::__construct($originalNode->getAttributes());
+	}
+
+	public function getVar(): Expr
+	{
+		return $this->var;
+	}
+
+	/**
+	 * @return Expr|Identifier
+	 */
+	public function getName()
+	{
+		return $this->name;
+	}
+
+	public function getOriginalNode(): Expr\NullsafeMethodCall
+	{
+		return $this->originalNode;
+	}
+
+	#[Override]
+	public function getType(): string
+	{
+		return 'PHPStan_Node_NullsafeFirstClassCallableNode';
+	}
+
+	/**
+	 * @return string[]
+	 */
+	#[Override]
+	public function getSubNodeNames(): array
+	{
+		return [];
+	}
+
+}

src/Node/Printer/Printer.php

@@ -29,6 +29,7 @@
 use PHPStan\Node\InstantiationCallableNode;
 use PHPStan\Node\IssetExpr;
 use PHPStan\Node\MethodCallableNode;
+use PHPStan\Node\NullsafeMethodCallOnFirstClassCallableNode;
 use PHPStan\Node\StaticMethodCallableNode;
 use PHPStan\Type\VerbosityLevel;
 use function sprintf;
@@ -160,6 +161,11 @@ protected function pPHPStan_Node_MethodCallableNode(MethodCallableNode $expr): s
 		return sprintf('__phpstanMethodCallable(%s)', $this->p($expr->getOriginalNode()));
 	}
 
+	protected function pPHPStan_Node_NullsafeFirstClassCallableNode(NullsafeMethodCallOnFirstClassCallableNode $expr): string // phpcs:ignore
+	{
+		return sprintf('__phpstanNullsafeFirstClassCallable(%s)', $this->p($expr->getOriginalNode()));
+	}
+
 	protected function pPHPStan_Node_StaticMethodCallableNode(StaticMethodCallableNode $expr): string // phpcs:ignore
 	{
 		return sprintf('__phpstanStaticMethodCallable(%s)', $this->p($expr->getOriginalNode()));

src/Rules/Methods/NullsafeMethodCallOnFirstClassCallableRule.php

@@ -0,0 +1,34 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Methods;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Node\NullsafeMethodCallOnFirstClassCallableNode;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * @implements Rule<NullsafeMethodCallOnFirstClassCallableNode>
+ */
+#[RegisteredRule(level: 0)]
+final class NullsafeMethodCallOnFirstClassCallableRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return NullsafeMethodCallOnFirstClassCallableNode::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		return [
+			RuleErrorBuilder::message('Cannot combine nullsafe operator with Closure creation.')
+				->nonIgnorable()
+				->identifier('nullsafe.firstClassCallable')
+				->build(),
+		];
+	}
+
+}

tests/PHPStan/Analyser/AnalyserIntegrationTest.php

@@ -1599,6 +1599,17 @@ public function testBug14707(): void
 		$this->assertNoErrors($errors);
 	}
 
+	public function testBug9746(): void
+	{
+		// first-class callable NullsafeMethodCall used to crash with an internal error
+		$errors = $this->runAnalyse(__DIR__ . '/data/bug-9746.php');
+		$this->assertCount(2, $errors);
+		$this->assertSame('Call to method Bug9746\HelloWorld::sayHello() on a separate line has no effect.', $errors[0]->getMessage());
+		$this->assertSame(11, $errors[0]->getLine());
+		$this->assertSame('Cannot combine nullsafe operator with Closure creation.', $errors[1]->getMessage());
+		$this->assertSame(11, $errors[1]->getLine());
+	}
+
 	/**
 	 * @param string[]|null $allAnalysedFiles
 	 * @return list<Error>

tests/PHPStan/Analyser/data/bug-9746.php

@@ -0,0 +1,13 @@
+<?php // lint >= 8.1
+
+declare(strict_types = 1);
+
+namespace Bug9746;
+
+class HelloWorld
+{
+	public function sayHello(?self $self): void
+	{
+		$self?->sayHello(...);
+	}
+}

tests/PHPStan/Rules/Methods/NullsafeMethodCallOnFirstClassCallableRuleTest.php

@@ -0,0 +1,39 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Methods;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+use PHPUnit\Framework\Attributes\RequiresPhp;
+
+/**
+ * @extends RuleTestCase<NullsafeMethodCallOnFirstClassCallableRule>
+ */
+class NullsafeMethodCallOnFirstClassCallableRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new NullsafeMethodCallOnFirstClassCallableRule();
+	}
+
+	#[RequiresPhp('>= 8.1.0')]
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/nullsafe-first-class-callable.php'], [
+			[
+				'Cannot combine nullsafe operator with Closure creation.',
+				20,
+			],
+			[
+				'Cannot combine nullsafe operator with Closure creation.',
+				26,
+			],
+			[
+				'Cannot combine nullsafe operator with Closure creation.',
+				34,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Methods/data/nullsafe-first-class-callable.php

@@ -0,0 +1,36 @@
+<?php // lint >= 8.1
+
+declare(strict_types = 1);
+
+namespace MethodCallableNullsafe;
+
+class Foo
+{
+
+	public function doFoo(): int
+	{
+		return 1;
+	}
+
+}
+
+function test(?Foo $foo): void
+{
+	// fatal error in PHP: "Cannot combine nullsafe operator with Closure creation"
+	$foo?->doFoo(...);
+}
+
+function testDynamic(?Foo $foo, string $method): void
+{
+	// dynamic method name - also a fatal error in PHP
+	$foo?->{$method}(...);
+}
+
+
+class HelloWorld
+{
+	public function sayHello(?self $self): void
+	{
+		$self?->sayHello(...);
+	}
+}