message: Improve convert() output type
diff: @@ -69,7 +69,7 @@ class IfElseToSwitch {
  this.path = path;
  }
  - convert(): ast.Node {
  + convert(): ast.SwitchStatement | ast.IfStatement {
  this.convertNode(this.path.node);
  return this.discriminant && this.canConvertAllBranches
  