useSingleCaseStatement

Invalid

switch (foo) {
    case true:
    case false:
        let foo = '';
        foo;
}

warning[useSingleCaseStatement]: A switch case should only have a single statement. If you want more, then wrap it in a block.
  ┌─ useSingleCaseStatement.js:4:9
  │  
4 │ ┌         let foo = '';
5 │ │         foo;
  │ └────────────'

Suggested fix: Wrap the statements in a block
    | @@ -1,6 +1,7 @@
0 0 |   switch (foo) {
1 1 |       case true:
2   | -     case false:
  2 | +     case false: {
3 3 |           let foo = '';
4 4 |           foo;
  5 | +     }
5 6 |   }

Valid

switch (foo) {
    case true:
    case false: {
        let foo = '';
        foo;
    }
}