Add support for PHP 8.5 #[\NoDiscard] on functions

Author: DanielEScherzer

src/Rules/Functions/CallToFunctionStatementWithNoDiscardRule.php

@@ -0,0 +1,66 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Functions;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Reflection\ReflectionProvider;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use function sprintf;
+
+/**
+ * @implements Rule<Node\Stmt\Expression>
+ */
+#[RegisteredRule(level: 4)]
+final class CallToFunctionStatementWithNoDiscardRule implements Rule
+{
+
+	public function __construct(private ReflectionProvider $reflectionProvider)
+	{
+	}
+
+	public function getNodeType(): string
+	{
+		return Node\Stmt\Expression::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (!$node->expr instanceof Node\Expr\FuncCall) {
+			return [];
+		}
+
+		$funcCall = $node->expr;
+		if (!($funcCall->name instanceof Node\Name)) {
+			return [];
+		}
+
+		if (!$this->reflectionProvider->hasFunction($funcCall->name, $scope)) {
+			return [];
+		}
+
+		$function = $this->reflectionProvider->getFunction($funcCall->name, $scope);
+
+		$attributes = $function->getAttributes();
+		$hasNoDiscard = false;
+		foreach ($attributes as $attrib) {
+			if ($attrib->getName() === 'NoDiscard') {
+				$hasNoDiscard = true;
+				break;
+			}
+		}
+		if (!$hasNoDiscard) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message(sprintf(
+				'Call to function %s() on a separate line discards return value.',
+				$function->getName(),
+			))->identifier('function.resultDiscarded')->build(),
+		];
+	}
+
+}

tests/PHPStan/Rules/Functions/CallToFunctionStatementWithNoDiscardRuleTest.php

@@ -0,0 +1,30 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Functions;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<CallToFunctionStatementWithNoDiscardRule>
+ */
+class CallToFunctionStatementWithNoDiscardRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new CallToFunctionStatementWithNoDiscardRule(self::createReflectionProvider());
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/function-call-statement-result-discarded.php'], [
+			[
+				'Call to function FunctionCallStatementResultDiscarded\withSideEffects() on a separate line discards return value.',
+				11,
+			],
+		]);
+
+	}
+
+}

tests/PHPStan/Rules/Functions/data/function-call-statement-result-discarded.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace FunctionCallStatementResultDiscarded;
+
+#[\NoDiscard]
+function withSideEffects(): int {
+	echo __FUNCTION__ . "\n";
+	return 1;
+}
+
+withSideEffects();