ArcanistTautologicalExpressionXHPASTLinterRule.php
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ArcanistTautologicalExpressionXHPASTLinterRule.php
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	<?php

	final class ArcanistTautologicalExpressionXHPASTLinterRule
	extends ArcanistXHPASTLinterRule {

	const ID = 20;

	public function getLintName() {
	return pht('Tautological Expression');
	}

	public function process(XHPASTNode $root) {
	$expressions = $root->selectDescendantsOfType('n_BINARY_EXPRESSION');

	static $operators = array(
	'-' => true,
	'/' => true,
	'-=' => true,
	'/=' => true,
	'<=' => true,
	'<' => true,
	'==' => true,
	'===' => true,
	'!=' => true,
	'!==' => true,
	'>=' => true,
	'>' => true,
	);

	static $logical = array(
	'\|\|' => true,
	'&&' => true,
	);

	foreach ($expressions as $expr) {
	$operator = $expr->getChildByIndex(1)->getConcreteString();
	if (!empty($operators[$operator])) {
	$left = $expr->getChildByIndex(0)->getSemanticString();
	$right = $expr->getChildByIndex(2)->getSemanticString();

	if ($left === $right) {
	$this->raiseLintAtNode(
	$expr,
	pht(
	'Both sides of this expression are identical, so it always '.
	'evaluates to a constant.'));
	}
	}

	if (!empty($logical[$operator])) {
	$left = $expr->getChildByIndex(0)->getSemanticString();
	$right = $expr->getChildByIndex(2)->getSemanticString();

	// NOTE: These will be null to indicate "could not evaluate".
	$left = $this->evaluateStaticBoolean($left);
	$right = $this->evaluateStaticBoolean($right);

	if (($operator === '\|\|' && ($left === true \|\| $right === true)) \|\|
	($operator === '&&' && ($left === false \|\| $right === false))) {
	$this->raiseLintAtNode(
	$expr,
	pht(
	'The logical value of this expression is static. '.
	'Did you forget to remove some debugging code?'));
	}
	}
	}
	}

	}