Range and Slice

• Add Range and Slice to the language
  • A range is an expression, may be iterated over, and has the following notation: expression ( .. | ..= ) expression [ .. expression]
  • A slice is an expression, and has the following notation: expression ( :: | ::= ) expression [ :: expression ]
    Note that unlike Python, we use :: instead of : to separate single arguments to the slice.
• Can iterate over all types which implement an iterator
• Fix several bugs associated with constraining function call arguments with expressions and property calls