src/Validator/Rules/OverlappingFieldsCanBeMerged.php
private function subfieldConflicts(
        array $conflicts,
        $responseName,
        FieldNode $ast1,
        FieldNode $ast2
    ) {
        if (count($conflicts) === 0) {
            return null;
        }

        return [
            [
                $responseName,
                array_map(
                    static function ($conflict) {
                        return $conflict[0];
                    },
                    $conflicts
                ),
            ],
            array_reduce(
                $conflicts,
                static function ($allFields, $conflict) {
                    return array_merge($allFields, $conflict[1]);
                },
                [$ast1]
            ),
            array_reduce(
                $conflicts,
                static function ($allFields, $conflict) {
                    return array_merge($allFields, $conflict[2]);
                },
                [$ast2]
            ),
        ];
    }
private function subfieldConflicts(
        array $conflicts,
        $responseName,
        FieldNode $ast1,
        FieldNode $ast2
    ) {
        if (count($conflicts) === 0) {
            return null;
        }

        return [
            [
                $responseName,
                array_map(
                    static function ($conflict) {
                        return $conflict[0];
                    },
                    $conflicts
                ),
            ],
            array_reduce(
                $conflicts,
                static function ($allFields, $conflict) {
                    return array_merge($allFields, $conflict[1]);
                },
                [$ast1]
            ),
            array_reduce(
                $conflicts,
                static function ($allFields, $conflict) {
                    return array_merge($allFields, $conflict[2]);
                },
                [$ast2]
            ),
        ];
    }
Given a series of Conflicts which occurred between two sub-fields, generate
a single Conflict.

@param mixed[][] $conflicts
@param string    $responseName

@return mixed[]|null