0.2.0

Version 0.2 (2022-07-29)

Breaking changes

• Using a contract as part of a static type annotation will in most cases fail with an appropriate error message. This is a temporary limitation in order to fix previously unsound behavior in the typechecker. This restriction will likely be lifted in the upcoming 0.3.x release.
  For more details, see issues #701 and #724

Fixes

• Fix unnecessarily restricted record contract for record.update
• Fix wrong interpretation of long interpolation-like sequences %..%{ in strings
• Fix panic when evaluating a switch in specific cases
• Fix fields without definition being assigned to null, instead of just being marked as undefined

Language features

• Merging null values together gives null, and merging empty lists together gives an empty list, instead of failing with error: non mergeable terms
• Add recursive let-bindings (let rec)
• Add type wildcards. Use _ in place of a type to let the typechecker fill
  the gap. Example: let foo : _ = array.all ((==) 2) [1,2,3]
• Add builtin.to_str and string.from to convert generic values to a string
• Re-introduce an official syntax for enum types

Tooling

• Add the nickel pprint-ast command to pretty print a parsed program (mostly for debugging purpose)
• Add the nickel doc command to produce simple markdown documentation from the in-code doc metadata

Documentation

• Fix various typos and remove use of deprecated syntax in the user manual