When formatting an expression that has partial application via `...`, and the application is formatted on several lines, the pretty printer adds a trailing `,` after the partial application`...`, like `...,`. Try pressing format on this playground to see it in effect: https://rescript-lang.org/try?version=v11.0.0-beta.1&code=DYUwLgBAZgdhC8EAUBLANBAfgCxMYA9hpgLYEBOIA4gSAM4ASIlxADuQQG4oDWKMAcwCyAV2BgUwfiABiFEgEMwEwQrXqNmzQEoEAPggBvAFAQIKCAGoIufASsQylGvSaUH7Lr37CxEqTCy8koqAlrh4cYAvsbGoJCsCuQSCsAIptAwSDh4hPAAjMRO1LSMzCAFbBzcfIKi4pLScuSKyj4RHeqVEAB0fdrGQA