Moved UselessCastRule to strict-rules

Author: ondrejmirtes

rules.neon

@@ -12,6 +12,7 @@ rules:
 	- PHPStan\Rules\BooleansInConditions\BooleanInElseIfConditionRule
 	- PHPStan\Rules\BooleansInConditions\BooleanInIfConditionRule
 	- PHPStan\Rules\BooleansInConditions\BooleanInTernaryOperatorRule
+	- PHPStan\Rules\Cast\UselessCastRule
 	- PHPStan\Rules\DisallowedConstructs\DisallowedEmptyRule
 	- PHPStan\Rules\DisallowedConstructs\DisallowedImplicitArrayCreationRule
 	- PHPStan\Rules\Functions\MissingFunctionParameterTypehintRule

src/Rules/Cast/UselessCastRule.php

@@ -0,0 +1,47 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Cast;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\Cast;
+use PHPStan\Analyser\Scope;
+use PHPStan\Type\ErrorType;
+use PHPStan\Type\TypeUtils;
+use PHPStan\Type\VerbosityLevel;
+
+class UselessCastRule implements \PHPStan\Rules\Rule
+{
+
+	public function getNodeType(): string
+	{
+		return Cast::class;
+	}
+
+	/**
+	 * @param \PhpParser\Node\Expr\Cast $node
+	 * @param \PHPStan\Analyser\Scope $scope
+	 * @return string[] errors
+	 */
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$castType = $scope->getType($node);
+		if ($castType instanceof ErrorType) {
+			return [];
+		}
+		$castType = TypeUtils::generalizeType($castType);
+
+		$expressionType = $scope->getType($node->expr);
+		if ($castType->isSuperTypeOf($expressionType)->yes()) {
+			return [
+				sprintf(
+					'Casting to %s something that\'s already %s.',
+					$castType->describe(VerbosityLevel::typeOnly()),
+					$expressionType->describe(VerbosityLevel::typeOnly())
+				),
+			];
+		}
+
+		return [];
+	}
+
+}

tests/Rules/Cast/UselessCastRuleTest.php

@@ -0,0 +1,43 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Cast;
+
+class UselessCastRuleTest extends \PHPStan\Testing\RuleTestCase
+{
+
+	protected function getRule(): \PHPStan\Rules\Rule
+	{
+		return new UselessCastRule();
+	}
+
+	public function testUselessCast(): void
+	{
+		require_once __DIR__ . '/data/useless-cast.php';
+		$this->analyse(
+			[__DIR__ . '/data/useless-cast.php'],
+			[
+				[
+					'Casting to int something that\'s already int.',
+					7,
+				],
+				[
+					'Casting to string something that\'s already string.',
+					9,
+				],
+				[
+					'Casting to stdClass something that\'s already stdClass.',
+					10,
+				],
+				[
+					'Casting to float something that\'s already float.',
+					27,
+				],
+				[
+					'Casting to string something that\'s already string.',
+					46,
+				],
+			]
+		);
+	}
+
+}

tests/Rules/Cast/data/useless-cast.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace UselessCast;
+
+function () {
+	$foo = (int) '5';
+	$foo = (int) 5;
+	$foo = (string) 5;
+	$foo = (string) '5';
+	$foo = (object) new \stdClass();
+
+	/** @var string|null $nullableString */
+	$nullableString = 'foo';
+	$foo = (string) $nullableString;
+
+	$foo = (float) (6 / 2);
+
+	$width = 1;
+	$scale = 2.0;
+	$width *= $scale;
+	echo (int) $width;
+
+	/** @var string|mixed $stringOrMixed */
+	$stringOrMixed = doFoo();
+	(string) $stringOrMixed;
+
+	$foo = (float) (100.0 / 25.432);
+
+	(int) "blabla";
+};
+
+function foo(string &$input) {
+	$input = 1;
+}
+
+function () {
+	$s = '';
+	foo($s);
+	(string) $s;
+};
+
+function () {
+	/** @var int|string $s */
+	$s = doFoo();
+	if (!is_numeric($s)) {
+		(string) $s;
+	}
+};