Report deprecated backtick operator in PHP 8.5

Author: ondrejmirtes

src/Php/PhpVersion.php

@@ -444,4 +444,9 @@ public function deprecatesNonStandardCasts(): bool
 		return $this->versionId >= 80500;
 	}
 
+	public function deprecatesBacktickOperator(): bool
+	{
+		return $this->versionId >= 80500;
+	}
+
 }

src/Rules/Operators/BacktickRule.php

@@ -0,0 +1,44 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Operators;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\ShellExec;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Php\PhpVersion;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * @implements Rule<ShellExec>
+ */
+#[RegisteredRule(level: 0)]
+final class BacktickRule implements Rule
+{
+
+	public function __construct(
+		private PhpVersion $phpVersion,
+	)
+	{
+	}
+
+	public function getNodeType(): string
+	{
+		return ShellExec::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (!$this->phpVersion->deprecatesBacktickOperator()) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message('Backtick operator is deprecated in PHP 8.5. Use shell_exec() function call instead.')
+				->identifier('backtick.deprecated')
+				->build(),
+		];
+	}
+
+}

tests/PHPStan/Rules/Operators/BacktickRuleTest.php

@@ -0,0 +1,35 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Operators;
+
+use PHPStan\Php\PhpVersion;
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+use const PHP_VERSION_ID;
+
+/**
+ * @extends RuleTestCase<BacktickRule>
+ */
+class BacktickRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new BacktickRule(new PhpVersion(PHP_VERSION_ID));
+	}
+
+	public function testRule(): void
+	{
+		$errors = [];
+		if (PHP_VERSION_ID >= 80500) {
+			$errors = [
+				[
+					'Backtick operator is deprecated in PHP 8.5. Use shell_exec() function call instead.',
+					4,
+				],
+			];
+		}
+		$this->analyse([__DIR__ . '/data/backtick.php'], $errors);
+	}
+
+}

tests/PHPStan/Rules/Operators/data/backtick.php

@@ -0,0 +1,5 @@
+<?php
+
+function (): void {
+	`echo "foo";`;
+};