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Prevent accurate comparison of floating-point numbers #38

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70 changes: 70 additions & 0 deletions src/Rules/Operators/OperandsInComparisonRule.php
Original file line number Diff line number Diff line change
@@ -0,0 +1,70 @@
<?php declare(strict_types = 1);

namespace PHPStan\Rules\Operators;

use PhpParser\Node;
use PhpParser\Node\Expr\BinaryOp;
use PHPStan\Analyser\Scope;
use PHPStan\Rules\Rule;
use PHPStan\Type\FloatType;

class OperandsInComparisonRule implements Rule
{

public function getNodeType(): string
{
return BinaryOp::class;
}

/**
* @param Node $node
* @param Scope $scope
* @return string[]
*/
public function processNode(Node $node, Scope $scope): array
{
if (!$node instanceof BinaryOp\Equal
&& !$node instanceof BinaryOp\Identical
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&& !$node instanceof BinaryOp\NotEqual
&& !$node instanceof BinaryOp\NotIdentical
&& !$node instanceof BinaryOp\GreaterOrEqual
&& !$node instanceof BinaryOp\SmallerOrEqual
) {
return [];
}

$rightType = $scope->getType($node->right);
$leftType = $scope->getType($node->left);

if ($rightType instanceof FloatType || $leftType instanceof FloatType) {
if ($node instanceof BinaryOp\Equal || $node instanceof BinaryOp\Identical) {
return [
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `abs($left - $right) < $epsilon`, where $epsilon is maximum allowed deviation.',
];
}

if ($node instanceof BinaryOp\NotEqual || $node instanceof BinaryOp\NotIdentical) {
return [
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `abs($left - $right) >= $epsilon`, where $epsilon is maximum allowed deviation.',
];
}

if ($node instanceof BinaryOp\GreaterOrEqual) {
return [
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `$left - $right >= $epsilon`, where $epsilon is maximum allowed deviation.',
];
}

return [
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `$right - $left >= $epsilon`, where $epsilon is maximum allowed deviation.',
];
}

return [];
}

}
51 changes: 51 additions & 0 deletions tests/Rules/Operators/OperandsInComparisonRuleTest.php
Original file line number Diff line number Diff line change
@@ -0,0 +1,51 @@
<?php declare(strict_types = 1);

namespace PHPStan\Rules\Operators;

use PHPStan\Rules\Rule;

class OperandsInComparisonRuleTest extends \PHPStan\Testing\RuleTestCase
{

protected function getRule(): Rule
{
return new OperandsInComparisonRule();
}

public function testRule(): void
{
$this->analyse([__DIR__ . '/data/operators.php'], [
[
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `abs($left - $right) < $epsilon`, where $epsilon is maximum allowed deviation.',
113,
],
[
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `abs($left - $right) < $epsilon`, where $epsilon is maximum allowed deviation.',
114,
],
[
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `abs($left - $right) >= $epsilon`, where $epsilon is maximum allowed deviation.',
115,
],
[
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `abs($left - $right) >= $epsilon`, where $epsilon is maximum allowed deviation.',
116,
],
[
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `$left - $right >= $epsilon`, where $epsilon is maximum allowed deviation.',
117,
],
[
'Exact comparison of floating-point numbers is not accurate.' . PHP_EOL
. 'You should use `$right - $left >= $epsilon`, where $epsilon is maximum allowed deviation.',
118,
],
]);
}

}
7 changes: 7 additions & 0 deletions tests/Rules/Operators/data/operators.php
Original file line number Diff line number Diff line change
Expand Up @@ -109,3 +109,10 @@ function (array $array, int $int, $mixed) {

explode($mixed, $mixed) + $int;
};

$float === 123.2;
$float == 123.2;
$float !== 123.2;
$float != 123.2;
$float >= 123.2;
$float <= 123.2;