v18.0.0

Breaking changes:

• Enable with optimizations

  The standard now gives implementations more freedom to optimize the
  β-reduction of with expressions, mainly in order to avoid pathological
  time and space complexity when interpreting chained with expressions, like:

  r with x.y = a with z = b

  Along the way, this changes how with expressions are encoded in the
  binary representation, which means that this is a technically breaking
  change.

  In practice, you are unlikely to to be affected by this change, except for the
  rare case where you protect an import with a semantic integrity check and the
  contents of the protected import contain a with expression where the
  left-hand side of the with expression is abstract, such as this one:

  λ(x: { a : Natural}) → x with a = 42 

  Other than that, semantic integrity checks are not affected because the
  interpreter will β-normalize away the with expression, which will then
  not affect the final hash.

New features:

• Add Prelude/Map/unpackOptionals

Other changes:

• Fixes and improvements to the Prelude:

  • Use dhall-docs comment format for Prelude
  • Amend relative import expressions on Prelude to use .dhall extensions