1.30.0

• Supports version 14.0.0 of the standard
• BREAKING CHANGE TO THE API: Add --check flag to dhall {lint,freeze}
  • You can now use the --check flag to verify that a file has already been
    linted or frozen
  • This is a breaking change to the types used by the Dhall.Format module
• BREAKING CHANGE TO THE LANGUAGE: Disallow Natural literals with leading zeros
  • Now a literal like 042 is no longer valid
  • See the changelog for standard version 14.0.0 for more details
• BUG FIX: Fix parsing of Double literal trailing whitespace
  • Certain expressions using Double literals would fail to parse, which this
    change fixes
• BUG FIX: Use DeriveLift instead of GHC Generics to derive Lift
  • This fixes a build failure on GHC 8.10
• Drop support for GHC 7.10.3
  • GHC 8.0.2 is now the earliest supported version
• Add support for dotted field syntax
  • { x.y.z = 1 } now legal syntax for nested fields
  • See the changelog for standard version 14.0.0 for more details
• Add support for duplicate record fields
  • This combines with the previous feature to let you write
    { x.y = 1, x.z = True }, which is equivalent to
    { x = { y = 1, z = True } }
  • See the changelog for standard version 14.0.0 for more details
• Add dhall lint support for deprecating Optional/{fold,build}
  • The Optional/{fold,build} built-ins are deprecated and can be implemented
    in terms of other language features
  • Optional/fold can be implemented in terms of merge (which now works on
    Optional values)
  • Optional/build could always be implemented using Some/None
  • dhall lint now transforms the deprecated built-ins to use their
    equivalent built-in-free versions
• Support Template Haskell for multiple datatypes
  • This extends the Template Haskell support added in the previous release to
    work for datatypes that refer to one another
• Add support for custom substitutions
  • You can now add custom substitutions, which are like let bindings that
    propagate to transitive imports
• Small formatting fixes