Keep non nullability if right expr is NeverType (#1063)

Author: rajyan

src/Analyser/NodeScopeResolver.php

@@ -2283,7 +2283,11 @@ function (MutatingScope $scope) use ($expr, $nodeCallback, $context): Expression
 			$hasYield = $result->hasYield();
 			$throwPoints = $result->getThrowPoints();
 			$scope = $result->getScope();
-			$scope = $this->revertNonNullability($scope, $nonNullabilityResult->getSpecifiedExpressions());
+
+			$rightExprType = $scope->getType($expr->right);
+			if (!$rightExprType instanceof NeverType || !$rightExprType->isExplicit()) {
+				$scope = $this->revertNonNullability($scope, $nonNullabilityResult->getSpecifiedExpressions());
+			}
 
 			if ($expr->left instanceof PropertyFetch || $expr->left instanceof Expr\NullsafePropertyFetch) {
 				$scope = $this->lookForExitVariableAssign($scope, $expr->left->var);

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -155,6 +155,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/pow.php');
 		if (PHP_VERSION_ID >= 80000 || self::$useStaticReflectionProvider) {
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/throw-expr.php');
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-5351.php');
 		}
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/non-empty-array.php');

tests/PHPStan/Analyser/data/bug-5351.php

@@ -0,0 +1,29 @@
+<?php // lint >= 8.0
+
+namespace Bug5351;
+
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+
+	public function doFoo(?string $html): void
+	{
+		$html ?? throw new \Exception();
+		assertType('string', $html);
+	}
+
+	/**
+	 * @return never
+	 */
+	public function neverReturn() {
+		throw new \Exception();
+	}
+
+	public function doBar(?string $html): void
+	{
+		$html ?? $this->neverReturn();
+		assertType('string', $html);
+	}
+
+}