Fix phpstan/phpstan#14001: Type loss in foreach when using StatementResult::getScope()

- Changed StatementResult, StatementExitPoint, and ReturnStatement to store
  and return MutatingScope instead of Scope, since mergeWith() is only on
  MutatingScope and calling it on Scope produced ErrorType, poisoning the
  variable type across foreach loop iterations
- Added toMutatingScope() calls in NodeScopeResolver where ReturnStatement
  is constructed from a Scope-typed callback parameter
- Fixed a null check on getClassReflection() in NodeScopeResolver that was
  exposed by the more precise type tracking
- Removed now-redundant toMutatingScope() calls on ReturnStatement::getScope()
- New regression test in tests/PHPStan/Analyser/nsrt/bug-14001.php

Author: staabm

src/Analyser/NodeScopeResolver.php

@@ -646,7 +646,7 @@ public function processStmtNode(
 					return;
 				}
 
-				$gatheredReturnStatements[] = new ReturnStatement($scope, $node);
+				$gatheredReturnStatements[] = new ReturnStatement($scope->toMutatingScope(), $node);
 			}, StatementContext::createTopLevel())->toPublic();
 
 			$this->callNodeCallback($nodeCallback, new FunctionReturnStatementsNode(
@@ -804,7 +804,7 @@ public function processStmtNode(
 						return;
 					}
 
-					$gatheredReturnStatements[] = new ReturnStatement($scope, $node);
+					$gatheredReturnStatements[] = new ReturnStatement($scope->toMutatingScope(), $node);
 				}, StatementContext::createTopLevel())->toPublic();
 
 				$methodReflection = $methodScope->getFunction();
@@ -842,11 +842,11 @@ public function processStmtNode(
 
 					foreach ($gatheredReturnStatements as $statement) {
 						if ($finalScope === null) {
-							$finalScope = $statement->getScope()->toMutatingScope();
+							$finalScope = $statement->getScope();
 							continue;
 						}
 
-						$finalScope = $finalScope->mergeWith($statement->getScope()->toMutatingScope());
+						$finalScope = $finalScope->mergeWith($statement->getScope());
 					}
 
 					if ($finalScope !== null) {
@@ -855,7 +855,7 @@ public function processStmtNode(
 
 				}
 			}
-			if (!$scope->getClassReflection()->isAnonymous() && !$scope->isInAnonymousFunction()) {
+			if ($scope->getClassReflection() !== null && !$scope->getClassReflection()->isAnonymous() && !$scope->isInAnonymousFunction()) {
 				$this->processPendingFibers($storage);
 			}
 		} elseif ($stmt instanceof Echo_) {
@@ -2763,7 +2763,7 @@ public function processClosureNode(
 				return;
 			}
 
-			$gatheredReturnStatements[] = new ReturnStatement($scope, $node);
+			$gatheredReturnStatements[] = new ReturnStatement($scope->toMutatingScope(), $node);
 		};
 
 		if (count($byRefUses) === 0) {
@@ -3142,7 +3142,7 @@ private function processPropertyHooks(
 					return;
 				}
 
-				$gatheredReturnStatements[] = new ReturnStatement($scope, $node);
+				$gatheredReturnStatements[] = new ReturnStatement($scope->toMutatingScope(), $node);
 			}, StatementContext::createTopLevel())->toPublic();
 
 			$this->callNodeCallback($nodeCallback, new PropertyHookReturnStatementsNode(

src/Analyser/StatementExitPoint.php

@@ -10,7 +10,7 @@
 final class StatementExitPoint
 {
 
-	public function __construct(private Stmt $statement, private Scope $scope)
+	public function __construct(private Stmt $statement, private MutatingScope $scope)
 	{
 	}
 
@@ -19,7 +19,7 @@ public function getStatement(): Stmt
 		return $this->statement;
 	}
 
-	public function getScope(): Scope
+	public function getScope(): MutatingScope
 	{
 		return $this->scope;
 	}

src/Analyser/StatementResult.php

@@ -18,7 +18,7 @@ final class StatementResult
 	 * @param EndStatementResult[] $endStatements
 	 */
 	public function __construct(
-		private Scope $scope,
+		private MutatingScope $scope,
 		private bool $hasYield,
 		private bool $isAlwaysTerminating,
 		private array $exitPoints,
@@ -29,7 +29,7 @@ public function __construct(
 	{
 	}
 
-	public function getScope(): Scope
+	public function getScope(): MutatingScope
 	{
 		return $this->scope;
 	}

src/Node/ReturnStatement.php

@@ -4,7 +4,7 @@
 
 use PhpParser\Node;
 use PhpParser\Node\Stmt\Return_;
-use PHPStan\Analyser\Scope;
+use PHPStan\Analyser\MutatingScope;
 
 /**
  * @api
@@ -14,12 +14,12 @@ final class ReturnStatement
 
 	private Node\Stmt\Return_ $returnNode;
 
-	public function __construct(private Scope $scope, Return_ $returnNode)
+	public function __construct(private MutatingScope $scope, Return_ $returnNode)
 	{
 		$this->returnNode = $returnNode;
 	}
 
-	public function getScope(): Scope
+	public function getScope(): MutatingScope
 	{
 		return $this->scope;
 	}

tests/PHPStan/Analyser/nsrt/bug-14001.php

@@ -0,0 +1,49 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14001;
+
+use PHPStan\Analyser\StatementResult;
+use PHPStan\Node\ExecutionEndNode;
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+	/**
+	 * @param list<ExecutionEndNode> $executionEnds
+	 */
+	public function testWithEarlyTermination(array $executionEnds): void
+	{
+		$finalScope = null;
+		foreach ($executionEnds as $executionEnd) {
+			$statementResult = $executionEnd->getStatementResult();
+			if ($statementResult->isAlwaysTerminating()) {
+				continue;
+			}
+			if ($finalScope === null) {
+				$finalScope = $statementResult->getScope();
+				continue;
+			}
+
+			$finalScope = $finalScope->mergeWith($statementResult->getScope());
+		}
+		assertType('PHPStan\Analyser\MutatingScope|null', $finalScope);
+	}
+
+	/**
+	 * @param list<ExecutionEndNode> $executionEnds
+	 */
+	public function testWithoutEarlyTermination(array $executionEnds): void
+	{
+		$finalScope = null;
+		foreach ($executionEnds as $executionEnd) {
+			$endScope = $executionEnd->getStatementResult()->getScope();
+			if ($finalScope === null) {
+				$finalScope = $endScope;
+				continue;
+			}
+
+			$finalScope = $finalScope->mergeWith($endScope);
+		}
+		assertType('PHPStan\Analyser\MutatingScope|null', $finalScope);
+	}
+}