forbidIncrementDecrementOnNonInteger (#179)

Author: janedbal

README.md

@@ -80,6 +80,8 @@ parameters:
         forbidIdenticalClassComparison:
             enabled: true
             blacklist: ['DateTimeInterface']
+        forbidIncrementDecrementOnNonInteger:
+            enabled: true
         forbidMatchDefaultArmForEnums:
             enabled: true
         forbidMethodCallOnMixed:
@@ -516,6 +518,15 @@ parameters:
                 - Ramsey\Uuid\UuidInterface
 ```
 
+### forbidIncrementDecrementOnNonInteger
+- Denies using `$i++`, `$i--`, `++$i`, `--$i` with any non-integer
+- PHP itself is leading towards stricter behaviour here and soft-deprecated **some** non-integer usages in 8.3, see [RFC](https://wiki.php.net/rfc/saner-inc-dec-operators)
+
+```php
+$value = '2e0';
+$value++; // would be float(3), denied
+```
+
 ### forbidMatchDefaultArmForEnums
 - Denies using default arm in `match()` construct when native enum is passed as subject
 - This rules makes sense only as a complement of [native phpstan rule](https://github.com/phpstan/phpstan-src/blob/1.7.x/src/Rules/Comparison/MatchExpressionRule.php#L94) that guards that all enum cases are handled in match arms

rules.neon

@@ -59,6 +59,8 @@ parameters:
         forbidIdenticalClassComparison:
             enabled: true
             blacklist: ['DateTimeInterface']
+        forbidIncrementDecrementOnNonInteger:
+            enabled: true
         forbidMatchDefaultArmForEnums:
             enabled: true
         forbidMethodCallOnMixed:
@@ -156,6 +158,9 @@ parametersSchema:
             enabled: bool()
             blacklist: arrayOf(string())
         ])
+        forbidIncrementDecrementOnNonInteger: structure([
+            enabled: bool()
+        ])
         forbidMatchDefaultArmForEnums: structure([
             enabled: bool()
         ])
@@ -245,6 +250,8 @@ conditionalTags:
         phpstan.rules.rule: %shipmonkRules.forbidFetchOnMixed.enabled%
     ShipMonk\PHPStan\Rule\ForbidIdenticalClassComparisonRule:
         phpstan.rules.rule: %shipmonkRules.forbidIdenticalClassComparison.enabled%
+    ShipMonk\PHPStan\Rule\ForbidIncrementDecrementOnNonIntegerRule:
+        phpstan.rules.rule: %shipmonkRules.forbidIncrementDecrementOnNonInteger.enabled%
     ShipMonk\PHPStan\Rule\ForbidMatchDefaultArmForEnumsRule:
         phpstan.rules.rule: %shipmonkRules.forbidMatchDefaultArmForEnums.enabled%
     ShipMonk\PHPStan\Rule\ForbidMethodCallOnMixedRule:
@@ -348,6 +355,8 @@ services:
         class: ShipMonk\PHPStan\Rule\ForbidIdenticalClassComparisonRule
         arguments:
             blacklist: %shipmonkRules.forbidIdenticalClassComparison.blacklist%
+    -
+        class: ShipMonk\PHPStan\Rule\ForbidIncrementDecrementOnNonIntegerRule
     -
         class: ShipMonk\PHPStan\Rule\ForbidMethodCallOnMixedRule
         arguments:

src/Rule/ForbidIncrementDecrementOnNonIntegerRule.php

@@ -0,0 +1,89 @@
+<?php declare(strict_types = 1);
+
+namespace ShipMonk\PHPStan\Rule;
+
+use LogicException;
+use PhpParser\Node;
+use PhpParser\Node\Expr\PostDec;
+use PhpParser\Node\Expr\PostInc;
+use PhpParser\Node\Expr\PreDec;
+use PhpParser\Node\Expr\PreInc;
+use PHPStan\Analyser\Scope;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleError;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\VerbosityLevel;
+use function get_class;
+use function sprintf;
+
+/**
+ * @implements Rule<Node>
+ */
+class ForbidIncrementDecrementOnNonIntegerRule implements Rule
+{
+
+    public function getNodeType(): string
+    {
+        return Node::class;
+    }
+
+    /**
+     * @return list<RuleError>
+     */
+    public function processNode(Node $node, Scope $scope): array
+    {
+        if (
+            $node instanceof PostInc
+            || $node instanceof PostDec
+            || $node instanceof PreInc
+            || $node instanceof PreDec
+        ) {
+            return $this->process($node, $scope);
+        }
+
+        return [];
+    }
+
+    /**
+     * @param PostInc|PostDec|PreInc|PreDec $node
+     * @return list<RuleError>
+     */
+    private function process(Node $node, Scope $scope): array
+    {
+        $exprType = $scope->getType($node->var);
+
+        if (!$exprType->isInteger()->yes()) {
+            $errorMessage = sprintf(
+                'Using %s over non-integer (%s)',
+                $this->getIncDecSymbol($node),
+                $exprType->describe(VerbosityLevel::typeOnly()),
+            );
+            $error = RuleErrorBuilder::message($errorMessage)
+                ->identifier('shipmonk.incrementDecrementOnNonInteger')
+                ->build();
+            return [$error];
+        }
+
+        return [];
+    }
+
+    /**
+     * @param PostInc|PostDec|PreInc|PreDec $node
+     */
+    private function getIncDecSymbol(Node $node): string
+    {
+        switch (get_class($node)) {
+            case PostInc::class:
+            case PreInc::class:
+                return '++';
+
+            case PostDec::class:
+            case PreDec::class:
+                return '--';
+
+            default:
+                throw new LogicException('Unexpected node given: ' . get_class($node));
+        }
+    }
+
+}

tests/Rule/ForbidIncrementDecrementOnNonIntegerRuleTest.php

@@ -0,0 +1,24 @@
+<?php declare(strict_types = 1);
+
+namespace ShipMonk\PHPStan\Rule;
+
+use PHPStan\Rules\Rule;
+use ShipMonk\PHPStan\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<ForbidIncrementDecrementOnNonIntegerRule>
+ */
+class ForbidIncrementDecrementOnNonIntegerRuleTest extends RuleTestCase
+{
+
+    protected function getRule(): Rule
+    {
+        return new ForbidIncrementDecrementOnNonIntegerRule();
+    }
+
+    public function testClass(): void
+    {
+        $this->analyseFile(__DIR__ . '/data/ForbidIncrementDecrementOnNonIntegerRule/code.php');
+    }
+
+}

tests/Rule/data/ForbidIncrementDecrementOnNonIntegerRule/code.php

@@ -0,0 +1,20 @@
+<?php declare(strict_types = 1);
+
+namespace ForbidIncrementDecrementOnNonIntegerRule;
+
+
+class IncDec
+{
+
+    public function test(int $int, string $string, float $float, int|string $union, array $array, $mixed)
+    {
+        $int++;
+        $string++; // error: Using ++ over non-integer (string)
+        $float++; // error: Using ++ over non-integer (float)
+        $union++; // error: Using ++ over non-integer (int|string)
+        $array++; // error: Using ++ over non-integer (array)
+        $mixed++; // error: Using ++ over non-integer (mixed)
+    }
+}
+
+