Fix phpstan/phpstan#13902: Chaining phpstan-assert fails to assert types

- In TypeSpecifier::specifyTypesInCondition(), recurse into inner method calls when processing a method chain in null context, so assertions from all methods in the chain are applied
- In TypeSpecifier::specifyTypesFromAsserts(), unwrap $this mapping through method calls whose return type equals the caller type, so outer assertions resolve to the original object
- Only recurse when $expr->var is a MethodCall to avoid breaking ImpossibleCheckTypeHelper's rootExpr tracking
- New regression test in tests/PHPStan/Analyser/nsrt/bug-13902.php

Author: staabm

src/Analyser/TypeSpecifier.php

@@ -590,11 +590,18 @@ public function specifyTypesInCondition(
 					));
 					$specifiedTypes = $this->specifyTypesFromAsserts($context, $expr, $asserts, $parametersAcceptor, $scope);
 					if ($specifiedTypes !== null) {
+						if ($context->null() && $expr->var instanceof MethodCall) {
+							return $specifiedTypes->unionWith($this->specifyTypesInCondition($scope, $expr->var, $context));
+						}
 						return $specifiedTypes;
 					}
 				}
 			}
 
+			if ($context->null() && $expr->var instanceof MethodCall) {
+				return $this->specifyTypesInCondition($scope, $expr->var, $context);
+			}
+
 			return $this->handleDefaultTruthyOrFalseyContext($context, $expr, $scope);
 		} elseif ($expr instanceof StaticCall && $expr->name instanceof Node\Identifier) {
 			if ($expr->class instanceof Name) {
@@ -1665,7 +1672,16 @@ private function specifyTypesFromAsserts(TypeSpecifierContext $context, Expr\Cal
 		}
 
 		if ($call instanceof MethodCall) {
-			$argsMap['this'] = [$call->var];
+			$callVar = $call->var;
+			while ($callVar instanceof MethodCall) {
+				$callerType = $scope->getType($callVar->var);
+				$returnType = $scope->getType($callVar);
+				if (!$callerType->equals($returnType)) {
+					break;
+				}
+				$callVar = $callVar->var;
+			}
+			$argsMap['this'] = [$callVar];
 		}
 
 		/** @var SpecifiedTypes|null $types */

tests/PHPStan/Analyser/nsrt/bug-13902.php

@@ -0,0 +1,46 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace Bug13902;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+	public mixed $a = null;
+	public mixed $b = null;
+
+	/**
+	 * @phpstan-assert int $this->a
+	 * @return $this
+	 */
+	public function setA()
+	{
+		$this->a = 1;
+		return $this;
+	}
+	/**
+	 * @phpstan-assert int $this->b
+	 * @return $this
+	 */
+	public function setB()
+	{
+		$this->b = 1;
+		return $this;
+	}
+}
+
+function test(): void
+{
+	$o = new HelloWorld;
+	$o->setA()->setB();
+	assertType('int', $o->a);
+	assertType('int', $o->b);
+
+	$o2 = new HelloWorld;
+	$o2->setA();
+	$o2->setB();
+	assertType('int', $o2->a);
+	assertType('int', $o2->b);
+}