Error
Background
Given a file named "pen.json" with:
{
  "type": "library",
  "dependencies": {}
}Call an error function
Given a file named "Foo.pen" with:
f = \() error {
  error(none)
}When I run pen build
Then the exit status should be 0.
Call a source function
Given a file named "Foo.pen" with:
f = \(e error) any {
  source(e)
}When I run pen build
Then the exit status should be 0.
Use a try operator
Given a file named "Foo.pen" with:
f = \(x number | error) number | error {
  x? + 1
}When I run pen build
Then the exit status should be 0.
Use a try operator with a union type
Given a file named "Foo.pen" with:
f = \(x number | none | error) number | error {
  if x = x? as number {
    x + 1
  } else if none {
    0
  }
}When I run pen build
Then the exit status should be 0.