grammar/src/when.grm

/**
#### When-expression

See [When-expression](control-flow.html#when-expression)
*/

when
  : "when" ("(" expression ")")? "{"
        whenEntry*
    "}"
  ;

whenEntry
  : whenCondition{","} "->" controlStructureBody SEMI
  : "else" "->" controlStructureBody SEMI
  ;

whenCondition
  : expression
  : ("in" | "!in") expression
  : ("is" | "!is") type
  ;