Added ImplodeFunctionRule

conf/config.level5.neon

@@ -11,6 +11,8 @@ parameters:
 	checkFunctionArgumentTypes: true
 	checkArgumentsPassedByReference: true
 
+rules:
+	- PHPStan\Rules\Functions\ImplodeFunctionRule
 
 services:
 	-

src/Rules/Functions/ImplodeFunctionRule.php

@@ -0,0 +1,64 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Functions;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\FuncCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\ReflectionProvider;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\ErrorType;
+use PHPStan\Type\UnionType;
+
+/**
+ * @implements \PHPStan\Rules\Rule<\PhpParser\Node\Expr\FuncCall>
+ */
+class ImplodeFunctionRule implements \PHPStan\Rules\Rule
+{
+
+	private \PHPStan\Reflection\ReflectionProvider $reflectionProvider;
+
+	public function __construct(
+		ReflectionProvider $reflectionProvider
+	)
+	{
+		$this->reflectionProvider = $reflectionProvider;
+	}
+
+	public function getNodeType(): string
+	{
+		return FuncCall::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (!($node->name instanceof \PhpParser\Node\Name)) {
+			return [];
+		}
+
+		$functionName = $this->reflectionProvider->resolveFunctionName($node->name, $scope);
+		if (!in_array($functionName, ['implode', 'join'], true)) {
+			return [];
+		}
+
+		$args = $node->getArgs();
+		if (count($args) === 1) {
+			$arrayType = $scope->getType($args[0]->value);
+		} elseif (count($args) === 2) {
+			$arrayType = $scope->getType($args[1]->value);
+		} else {
+			return [];
+		}
+
+		if ($arrayType->getIterableValueType()->toString() instanceof ErrorType) {
+			return [
+				RuleErrorBuilder::message(
+					sprintf('Call to %s with invalid non-string argument.', $functionName)
+				)->build(),
+			];
+		}
+
+		return [];
+	}
+
+}

tests/PHPStan/Rules/Functions/ImplodeFunctionRuleTest.php

@@ -0,0 +1,47 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Functions;
+
+/**
+ * @extends \PHPStan\Testing\RuleTestCase<ImplodeFunctionRule>
+ */
+class ImplodeFunctionRuleTest extends \PHPStan\Testing\RuleTestCase
+{
+
+	protected function getRule(): \PHPStan\Rules\Rule
+	{
+		$reflectionProvider = $this->createReflectionProvider();
+		return new ImplodeFunctionRule($reflectionProvider);
+	}
+
+	public function testFile(): void
+	{
+		$this->analyse([__DIR__ . '/data/implode.php'], [
+			[
+				'Call to implode with invalid non-string argument.',
+				9,
+			],
+			[
+				'Call to implode with invalid non-string argument.',
+				11,
+			],
+			[
+				'Call to implode with invalid non-string argument.',
+				12,
+			],
+			[
+				'Call to implode with invalid non-string argument.',
+				13,
+			],
+			[
+				'Call to implode with invalid non-string argument.',
+				15,
+			],
+			[
+				'Call to join with invalid non-string argument.',
+				16,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Functions/data/implode.php

@@ -0,0 +1,25 @@
+<?php declare(strict_types = 1);
+
+namespace ImplodeFunction;
+
+class Foo
+{
+	public function invalidArgs(): void
+	{
+		implode('', ['12', '123', ['1234', '12345']]);
+
+		implode([['1234', '12345']]);
+		implode([[1234, 12345]]);
+		implode([[true, 12345]]);
+
+		implode('', [['1234', '12345']]);
+		join('', [['1234', '12345']]);
+	}
+
+	public function valid() {
+		implode(['12', '345']);
+
+		implode('', ['12', '345']);
+		join('', ['12', '345']);
+	}
+}