no-duplicate-case

:mag_right: works better with type information

Detects identical case clauses within a single switch statement.

Without type information the clauses are compared for syntactic equality. With type information this rule additionally detects clauses that definitely have the same value at runtime.

Rationale

Duplicate case clauses are dead code. Only the first matching clause is reachable.

Examples

:thumbsdown: Examples of incorrect code

switch (v) {
  case 1:
  case +'1': // same as above
  case true:
  case !false: // same as above
  case 'foo':
  case "foo": // same as above
  case `foo`: // same as above
  case someVariable:
  case someVariable: // same as above
}

:thumbsup: Examples of correct code

switch (v) {
  case 1:
  case true:
  case false:
  case 'foo':
  case 'bar':
  case (condition ? 'bar' : 'baz'):
  case someVariable:
  case someOtherVariable:
}

Related Rules

• no-case-declaration
• no-fallthrough