Improve CompactVariablesRule - recognize array parameters

src/Rules/Variables/CompactVariablesRule.php

@@ -6,7 +6,9 @@
 use PHPStan\Analyser\Scope;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\Constant\ConstantArrayType;
 use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\Type;
 
 /**
  * @implements \PHPStan\Rules\Rule<\PhpParser\Node\Expr\FuncCall>
@@ -43,25 +45,47 @@ public function processNode(Node $node, Scope $scope): array
 
 		foreach ($functionArguments as $argument) {
 			$argumentType = $scope->getType($argument->value);
-			if (!$argumentType instanceof ConstantStringType) {
-				continue;
-			}
+			$constantStrings = $this->findConstantStrings($argumentType);
+			foreach ($constantStrings as $constantString) {
+				$variableName = $constantString->getValue();
+				$scopeHasVariable = $scope->hasVariableType($variableName);
 
-			$variableName = $argumentType->getValue();
-			$scopeHasVariable = $scope->hasVariableType($variableName);
-
-			if ($scopeHasVariable->no()) {
-				$messages[] = RuleErrorBuilder::message(
-					sprintf('Call to function compact() contains undefined variable $%s.', $variableName)
-				)->line($argument->getLine())->build();
-			} elseif ($this->checkMaybeUndefinedVariables && $scopeHasVariable->maybe()) {
-				$messages[] = RuleErrorBuilder::message(
-					sprintf('Call to function compact() contains possibly undefined variable $%s.', $variableName)
-				)->line($argument->getLine())->build();
+				if ($scopeHasVariable->no()) {
+					$messages[] = RuleErrorBuilder::message(
+						sprintf('Call to function compact() contains undefined variable $%s.', $variableName)
+					)->line($argument->getLine())->build();
+				} elseif ($this->checkMaybeUndefinedVariables && $scopeHasVariable->maybe()) {
+					$messages[] = RuleErrorBuilder::message(
+						sprintf('Call to function compact() contains possibly undefined variable $%s.', $variableName)
+					)->line($argument->getLine())->build();
+				}
 			}
 		}
 
 		return $messages;
 	}
 
+	/**
+	 * @param Type $type
+	 * @return array<int, ConstantStringType>
+	 */
+	private function findConstantStrings(Type $type): array
+	{
+		if ($type instanceof ConstantStringType) {
+			return [$type];
+		}
+
+		if ($type instanceof ConstantArrayType) {
+			$result = [];
+			foreach ($type->getValueTypes() as $valueType) {
+				$constantStrings = $this->findConstantStrings($valueType);
+				$result = array_merge($result, $constantStrings);
+			}
+
+			return $result;
+		}
+
+		return [];
+	}
+
 }

tests/PHPStan/Rules/Variables/CompactVariablesRuleTest.php

@@ -30,6 +30,10 @@ public function testCompactVariables(): void
 				'Call to function compact() contains possibly undefined variable $baz.',
 				23,
 			],
+			[
+				'Call to function compact() contains undefined variable $foo.',
+				29,
+			],
 		]);
 	}
 

tests/PHPStan/Rules/Variables/data/compact-variables.php

@@ -23,4 +23,9 @@ public function doFoo(string $foo): array
 			'baz'
 		);
 	}
+
+	public function doBar(): void
+	{
+		compact([[['foo']]]);
+	}
 }