Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires craftcms/rector dev-main -> satisfiable by craftcms/rector[dev-main]. - craftcms/rector dev-main requires rector/rector ^1.0.0 -> found rector/rector[1.0.0, ..., 1.2.10] but it conflicts with your root composer.json require (^2.0). Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.