Fix missing detection of dead code in closures (#4148)

Author: staabm

src/Analyser/NodeScopeResolver.php

@@ -4639,6 +4639,9 @@ private function processClosureNode(
 			throw new ShouldNotHappenException();
 		}
 
+		$returnType = $closureType->getReturnType();
+		$isAlwaysTerminating = ($returnType instanceof NeverType && $returnType->isExplicit());
+
 		$nodeCallback(new InClosureNode($closureType, $expr), $closureScope);
 
 		$executionEnds = [];
@@ -4690,7 +4693,7 @@ private function processClosureNode(
 				array_merge($statementResult->getImpurePoints(), $closureImpurePoints),
 			), $closureScope);
 
-			return new ProcessClosureResult($scope, $statementResult->getThrowPoints(), $statementResult->getImpurePoints(), $invalidateExpressions);
+			return new ProcessClosureResult($scope, $statementResult->getThrowPoints(), $statementResult->getImpurePoints(), $invalidateExpressions, $isAlwaysTerminating);
 		}
 
 		$count = 0;
@@ -4736,7 +4739,7 @@ private function processClosureNode(
 			array_merge($statementResult->getImpurePoints(), $closureImpurePoints),
 		), $closureScope);
 
-		return new ProcessClosureResult($scope->processClosureScope($closureResultScope, null, $byRefUses), $statementResult->getThrowPoints(), $statementResult->getImpurePoints(), $invalidateExpressions);
+		return new ProcessClosureResult($scope->processClosureScope($closureResultScope, null, $byRefUses), $statementResult->getThrowPoints(), $statementResult->getImpurePoints(), $invalidateExpressions, $isAlwaysTerminating);
 	}
 
 	/**
@@ -5180,6 +5183,7 @@ private function processArgs(
 				if ($callCallbackImmediately) {
 					$throwPoints = array_merge($throwPoints, array_map(static fn (ThrowPoint $throwPoint) => $throwPoint->isExplicit() ? ThrowPoint::createExplicit($scope, $throwPoint->getType(), $arg->value, $throwPoint->canContainAnyThrowable()) : ThrowPoint::createImplicit($scope, $arg->value), $closureResult->getThrowPoints()));
 					$impurePoints = array_merge($impurePoints, $closureResult->getImpurePoints());
+					$isAlwaysTerminating = $isAlwaysTerminating || $closureResult->isAlwaysTerminating();
 				}
 
 				$uses = [];

src/Analyser/ProcessClosureResult.php

@@ -17,6 +17,7 @@ public function __construct(
 		private array $throwPoints,
 		private array $impurePoints,
 		private array $invalidateExpressions,
+		private bool $isAlwaysTerminating,
 	)
 	{
 	}
@@ -50,4 +51,9 @@ public function getInvalidateExpressions(): array
 		return $this->invalidateExpressions;
 	}
 
+	public function isAlwaysTerminating(): bool
+	{
+		return $this->isAlwaysTerminating;
+	}
+
 }

tests/PHPStan/Analyser/ExpressionResultTest.php

@@ -113,6 +113,22 @@ public static function dataIsAlwaysTerminating(): array
 				'call_user_func(fn() => exit());',
 				true,
 			],
+			[
+				'(function() { exit(); })();',
+				true,
+			],
+			[
+				'function () {};',
+				false,
+			],
+			[
+				'call_user_func(function() { exit(); });',
+				true,
+			],
+			[
+				'usort($arr, static function($a, $b):int { return $a <=> $b; });',
+				false,
+			],
 			[
 				'var_dump(1+exit());',
 				true,