dhall-1.18.0: CHANGELOG.md

1.18.0

* Supports version 3.0.0 of the language standard:
    * See: https://github.com/dhall-lang/dhall-lang/releases/tag/v3.0.0
* BREAKING CHANGE TO THE LANGUAGE AND API: New `Some`/`None` constructors for
  `Optional` values
    * Example: `[ Some 1, None Natural ]`
    * This is a breaking change to the language because `Some` and `None` are
      now reserved keywords
    * This is a breaking change to the API because `Some` and `None` are new
      constructors for the `Expr` type
* BREAKING CHANGE TO THE LANGUAGE AND API: Support for kind polymorphism
    * This adds a new `Sort` constant above `Kind` in the hierarchy
    * i.e. `Type : Kind : Sort`
    * This is a breaking change to the language because `Sort` is now a
      reserved keyword
    * This is a breaking change to the API because `Sort` is a new
      constructor for the `Expr` type
* BREAKING CHANGE TO THE API: New `Dhall.Map` module
    * This replaces `InsOrdHashMap` in the API
    * The primary motivation is to improve performance and to remove the
      dependency on `insert-ordered-containers`
* BREAKING CHANGE TO THE API: Use standard version instead of protocol version
    * The binary protocol is now versioned alongside the standard
    * The `ProtocolVersion` type is renamed to `StandardVersion` and the
    * `--protocol-version` option is renamed to `--standard-version`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/634
* BUG FIX: Fix import chaining for custom header imports
    * See: https://github.com/dhall-lang/dhall-haskell/pull/618
* BUG FIX: Fix import chaining for imports protected by semantic integrity
  checks
    * See: https://github.com/dhall-lang/dhall-haskell/pull/584
* BUG FIX: Record literals and types produced by `∧`/`⫽`/`⩓` are now sorted
    * This ensures that β-normalization is idempotent
    * See: https://github.com/dhall-lang/dhall-haskell/pull/572
* BUG FIX: `dhall freeze` now correctly handles the starting file being
  located outside the current working directory
    * See: https://github.com/dhall-lang/dhall-haskell/commit/a22aa79d1957be9ecf166ea066e2a9a5b309e1ae
* BUG FIX: Fix parsing of IPv4-mapped IPv6 addresses
    * See: https://github.com/dhall-lang/dhall-haskell/pull/632
* FEATURE: New `--ascii` flag for ASCII output
    * See: https://github.com/dhall-lang/dhall-haskell/pull/570
* FEATURE: New `dhall encode` and `dhall decode` subcommands
    * These allow you to transform Dhall source code to and from its binary
      representation
    * See: https://github.com/dhall-lang/dhall-haskell/pull/588
* LARGE parsing performance improvements
    * Parsing is about 10x-100x faster on most code
    * See: https://github.com/dhall-lang/dhall-haskell/pull/591
    * See: https://github.com/dhall-lang/dhall-haskell/pull/592
    * See: https://github.com/dhall-lang/dhall-haskell/pull/597
    * See: https://github.com/dhall-lang/dhall-haskell/pull/601
    * See: https://github.com/dhall-lang/dhall-haskell/pull/602
    * See: https://github.com/dhall-lang/dhall-haskell/pull/604
    * See: https://github.com/dhall-lang/dhall-haskell/pull/606
* Type-checking performance improvements:
    * See: https://github.com/dhall-lang/dhall-haskell/pull/566
* Normalization performance improvements:
    * See: https://github.com/dhall-lang/dhall-haskell/pull/610
* `dhall freeze` now caches the imports as it freezes them
    * See: https://github.com/dhall-lang/dhall-haskell/pull/587
* `dhall freeze` now refreezes imports with invalid semantic integrity checks
    * See: https://github.com/dhall-lang/dhall-haskell/pull/637
* `dhall freeze` now adds a trailing newline
    * See: https://github.com/dhall-lang/dhall-haskell/pull/629
* Build against `megaparsec-7.0.*`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/565
* Support GHC 8.6
    * See: https://github.com/dhall-lang/dhall-haskell/pull/599
    * See: https://github.com/dhall-lang/dhall-haskell/pull/623
* Support GHC all the way back to 7.10.3
    * See: https://github.com/dhall-lang/dhall-haskell/pull/595
    * See: https://github.com/dhall-lang/dhall-haskell/pull/621
* Improvements to error messages:
    * See: https://github.com/dhall-lang/dhall-haskell/pull/563
    * See: https://github.com/dhall-lang/dhall-haskell/pull/576
    * See: https://github.com/dhall-lang/dhall-haskell/pull/583
    * See: https://github.com/dhall-lang/dhall-haskell/pull/589


1.17.0

* This release corresponds to version 2.0.0 of the language standard
* BREAKING CHANGE TO THE LANGUAGE AND API: Binary serialization support
    * This is a breaking change to the hash for all semantic integrity checks
    * The hash used by the semantic integrity check is now based on the
      binary representation instead of a text representation of the
      expression
    * You can pin the new hashes by supplying the `--protocol-version 1.0`
      option on the command line until you need support for newer language
      features 
    * This also includes a breaking change to `ImportType` in the API
* BREAKING CHANGE TO THE LANGUAGE: Disallow combining records of terms and
  types
    * This is mainly for consistency and to improve type errors that would
      have otherwise happened further downstream
    * This should not affect the vast majority of code
    * See: https://github.com/dhall-lang/dhall-haskell/pull/538
* BUG FIX: Semantic integrity checks now work for imported expression using
  the `constructors` keyword
    * See: https://github.com/dhall-lang/dhall-haskell/pull/554
* BUG FIX: Fix α-normalization of expressions with bound variables named `_`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/524
* BUG FIX: Fix `isNormalized` to match `normalize`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/522
* BUG FIX: `dhall lint` now correctly handles nested `let` expressions
    * See: https://github.com/dhall-lang/dhall-haskell/pull/555
* FEATURE: Imports protected by a semantic integrity check are now cached
    * See: https://github.com/dhall-lang/dhall-haskell/pull/533
* The default `dhall` command no longer outputs the type to `stderr`
    * You can add back the type as a type annotation using the
      `--annotate` switch
    * See: https://github.com/dhall-lang/dhall-haskell/pull/544
* New utilities for building `InputTypes`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/530
* Improve parsing performance for long variable names
    * See: https://github.com/dhall-lang/dhall-haskell/pull/526
* More succinct type diffs for function types
    * See: https://github.com/dhall-lang/dhall-haskell/pull/540
* Identifier names can now begin with keywords
    * i.e. `ifChanged` and `lettuce` are now legal identifiers
    * See: https://github.com/dhall-lang/dhall-haskell/pull/551

1.16.1

* Fix test failure due to missing test data file

1.16.0

* BREAKING CHANGE: Consolidate `input` family of functions
    * These now take a record of options
    * This also `_stack` field of the `Status` type from `[Import]` to
      `NonEmpty Import`
* Permit `$` in quoted variable names
    * See: https://github.com/dhall-lang/dhall-haskell/pull/510

1.15.1

* Fix infinite loop when formatting expressions containing `?`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/491

1.15.0

* BREAKING CHANGE TO THE API: Support alternative imports using new `?` operator
    * This adds a new constructor which affects exhaustive pattern matches
    * See: https://github.com/dhall-lang/dhall-haskell/pull/473
* BREAKING CHANGE TO THE API: Add `Integer/toDouble` built-in function
    * This adds a new constructor which affects exhaustive pattern matches
    * See: https://github.com/dhall-lang/dhall-haskell/pull/434
* BREAKING CHANGE TO THE API: Use strict `Text` instead of lazy `Text`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/455
* BREAKING CHANGE TO THE API: Remove `Buildable` in favor of `Pretty`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/459
* BREAKING CHANGE TO THE API: Removed the `Parent` constructor from `FilePrefix`
    * Instead, use `Here` with a `".."` prefix.
    * See: https://github.com/dhall-lang/dhall-haskell/pull/407
* BUG FIX: Disallow duplicate fields in records
    * See: https://github.com/dhall-lang/dhall-haskell/pull/430
* BUG FIX: Fix stripping of leading whitespace in multi-line strings
    * See: https://github.com/dhall-lang/dhall-haskell/pull/469
* BUG FIX: Fix formatting field access of an import
    * See: https://github.com/dhall-lang/dhall-haskell/pull/471
* Add `dhall freeze` command
    * See: https://github.com/dhall-lang/dhall-haskell/pull/486
* Add `dhall diff` command
    * See: https://github.com/dhall-lang/dhall-haskell/pull/442
* Add `dhall lint` command
    * See: https://github.com/dhall-lang/dhall-haskell/pull/484
* Change `dhall-repl`/`dhall-hash`/`dhall-format` to `dhall` subcommands
    * i.e. `dhall repl`/`dhall hash`/`dhall format`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/435
    * See: https://github.com/dhall-lang/dhall-haskell/pull/452
* Add `with-http` cabal flag to disable support for remote imports
    * See: https://github.com/dhall-lang/dhall-haskell/pull/482
* Added `inputFrom` and `inputFromWith`
    * These allow naming the file that the expression is coming from for better
      error messages
    * See: https://github.com/dhall-lang/dhall-haskell/pull/464
* Performance improvements
    * See: https://github.com/dhall-lang/dhall-haskell/pull/420
* Tutorial recommends GitHub for Prelude instead of IPFS
    * See: https://github.com/dhall-lang/dhall-haskell/pull/479
* Pretty-print expressions in type errors
    * See: https://github.com/dhall-lang/dhall-haskell/pull/429
* Formatting improvements
    * See: https://github.com/dhall-lang/dhall-haskell/pull/398
    * See: https://github.com/dhall-lang/dhall-haskell/pull/458
* Diff improvements
    * See: https://github.com/dhall-lang/dhall-haskell/pull/455
    * See: https://github.com/dhall-lang/dhall-haskell/pull/470
    * See: https://github.com/dhall-lang/dhall-haskell/pull/478

1.14.0

* BREAKING CHANGE TO THE LANGUAGE: Switch grammar of `Natural` and `Integer`
    * `Natural` number literals are now unsigned and `Integer` literals always
      require a sign
    * This is a **VERY** disruptive change to most Dhall code in the wild but
      was unanimously agreed upon here:
      https://github.com/dhall-lang/dhall-lang/issues/138
    * See also: https://github.com/dhall-lang/dhall-haskell/pull/381
* BREAKING CHANGE TO THE LANGUAGE: Drop support for importing directories
    * Importing `dir/` used to resolve to `dir/@`, which is no longer supported
    * See: https://github.com/dhall-lang/dhall-haskell/pull/384
* BREAKING CHANGE TO THE LANGUAGE: Change to the grammar for imports
    * File path components can no longer contain `#` or `?` characters
    * URL imports must now contain at least one path component
    * URL path components must match the grammar for file path components
    * See: https://github.com/dhall-lang/dhall-haskell/pull/390
* BREAKING CHANGE TO THE API: Rename `Path{,Mode,Hashed,Type}` to
  `Import{,Mode,Hashed,Type}`
    * In practice this change is not breaking for the most common use cases
      since this also provides a `Path` type synonym for backwards compatibility
    * See: https://github.com/dhall-lang/dhall-haskell/pull/376
* BUG FIX: Fix α-equivalence bug when type-checking `merge`
    * `merge` expressions would sometimes reject valid code due to a
       type-checking bug
    * See: https://github.com/dhall-lang/dhall-haskell/pull/394
* Improve import caching
    * See: https://github.com/dhall-lang/dhall-haskell/pull/388
    * See: https://github.com/dhall-lang/dhall-haskell/pull/392
* Increase upper bound on `tasty`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/382
* Fix lower bound on `insert-ordered-containers`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/377

1.13.1

* Increase upper bound on `ansi-terminal` and `megaparsec`

1.13.0

* BUG FIX: Fix semantic integrity hashing support
    * Both parsing and pretty-printing semantic hashes were broken since version
      1.11.0
    * See: https://github.com/dhall-lang/dhall-haskell/pull/345
* BUG FIX: Allow leading whitespace in interpolated expresssions
    * See: https://github.com/dhall-lang/dhall-haskell/pull/369
* BUG FIX: Fix `deriving (Interpret)` for sum types
    * The types of alternatives were not correctly included in the corresponding
      Dhall type
    * See: https://github.com/dhall-lang/dhall-haskell/pull/348
* BREAKING CHANGE TO LANGUAGE: Records cannot store both types and terms
    * Records can also not store type-level functions (like `List`)
        * Records might be allowed to store type-level functions again in the
          future
    * This fixes a potential soundness bug
    * The primarily practical consequence of this change is that if you are
      hosting a "package" then you will need to split terms and types from your
      package into different records for your users to import
    * This also implies removing the `./Monoid` type-level function from the
      `./Prelude/package.dhall` record
    * See: https://github.com/dhall-lang/dhall-haskell/pull/335
* BREAKING CHANGE TO THE API: Replace `trifecta` with `megaparsec`
    * This change the API to use the `Parser` type from `megaparsec`
    * This also slightly changes the type of `exprFromText`
    * If you program using the type classes provided by the `parsers` library
      then this is not a breaking change as that interface is preserved
    * See: https://github.com/dhall-lang/dhall-haskell/pull/268
* BREAKING CHANGE TO THE API: New `⩓` operator for merging record types
    * Example: `{ foo : Text } ⩓ { bar : Bool } = { foo : Text, bar : Bool }`
    * This is breaking because it adds a new constructor to the `Expr` type
    * See: https://github.com/dhall-lang/dhall-haskell/pull/342
* BREAKING CHANGE TO THE API: New support for projecting a subset of fields
    * Example: `{ x = 1, y = 2, z = 3 }.{ x, y } = { x = 1, y = 2 }`
    * This is breaking because it adds a new constructor to the `Expr` type
    * See: https://github.com/dhall-lang/dhall-haskell/pull/350
* API+UX feature: New support for pretty-printing diffs of Dhall expressions
    * Error messages also use this feature to simplify large type mismatches
    * There is also a new `Dhall.Diff` module
    * See: https://github.com/dhall-lang/dhall-haskell/pull/336
* Add `version`, `resolve`, `type`, and `normalize` sub-commands to interpreter
    * See: https://github.com/dhall-lang/dhall-haskell/pull/352
* Support GHC 7.10.3
    * See: https://github.com/dhall-lang/dhall-haskell/pull/340
* `:type` command in `dhall-repl` now only displays the type
    * Before it would also display the original expression
    * See: https://github.com/dhall-lang/dhall-haskell/pull/344
* Trim dependency tree
    * See: https://github.com/dhall-lang/dhall-haskell/pull/351
    * See: https://github.com/dhall-lang/dhall-haskell/pull/268
    * See: https://github.com/dhall-lang/dhall-haskell/pull/355

1.12.0

* Additional changes to support GHC 8.4
    * See: https://github.com/dhall-lang/dhall-haskell/pull/331
* BREAKING CHANGE TO API: Replace dependency on `text-format` with `formatting`
    * This replace the `Data.Text.Buildable.Buildable` instances with
      `Formatting.Buildable.Buildable` instances, which is why this is a
       breaking change
    * `text-format` is no longer maintained and blocking GHC 8.4 support
    * See: https://github.com/dhall-lang/dhall-haskell/pull/330

1.11.1

* Support GHC 8.4
    * See: https://github.com/dhall-lang/dhall-haskell/pull/321
* Fix α-normalization bug
    * Note that this is not a type-checking bug.  This only affects users who
      were directly using the `alphaNormalize` function from the Haskell API
      because `let` expressions were not correctly α-normalized
    * See: https://github.com/dhall-lang/dhall-haskell/pull/319
* Slight tweak to syntax highlighting
    * See: https://github.com/dhall-lang/dhall-haskell/pull/324
* Increase upper bound on `ansi-terminal` and `exceptions`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/322
    * See: https://github.com/dhall-lang/dhall-haskell/pull/325

1.11.0

* BREAKING CHANGE TO THE API: Fix `{Natural,Optional,List}/build` semantics to
  match standard
    * This is a breaking change because the `OptionalLit` and `ListLit`
      constructors changed their representations to efficiently support the
      standard semantics
    * `ListLit` now stores a `Data.Sequence.Seq` instead of a
      `Data.Vector.Vector`
    * `OptionalLit` now stores a `Maybe` instead of a `Data.Vector.Vector`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/300
* BREAKING CHANGE TO THE COMMAND LINE: `dhall` executable always formats output
    * Previously you had to opt into formatting using `--pretty`
    * Now formatting is obligatory and the `--pretty` flag is gone
    * See: https://github.com/dhall-lang/dhall-haskell/pull/303
* Feature: New `:save` command for `dhall-repl`
    * Now you can save an expression to a file: `./yourFile = someExpression`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/309
* Improvement: Add new simplifications to match standard
    * See: https://github.com/dhall-lang/dhall-haskell/pull/312
    * See: https://github.com/dhall-lang/dhall-haskell/pull/316
* Improvement: Fix equivalence check to match standard
    * Practically this means that more corner cases of the language correctly
      type-check than before
* Improvement: New `--plain` flag to disable syntax highlighting
    * See: https://github.com/dhall-lang/dhall-haskell/pull/310
* Improvement: Prelude now provides an umbrella `package.dhall` import
    * This is primarily for convenience
    * See: https://github.com/dhall-lang/dhall-haskell/pull/298
* Improvement: Context is now normalized
    * See: https://github.com/dhall-lang/dhall-haskell/pull/302
* Replace `cryptohash` dependency with `cryptonite`
    * See: https://github.com/dhall-lang/dhall-haskell/commit/5d2012927a062ec8bdf2bbaba77150344f38db77
* Increase upper bound on exceptions
    * See: https://github.com/dhall-lang/dhall-haskell/pull/306
* Fix type error in tutorial
    * See: https://github.com/dhall-lang/dhall-haskell/commit/5a9126b2f684d3236fc1e8e20e206cfaf47d97db

1.10.0

* Feature: Records/unions can now have fields/alternatives that are types
    * i.e. `{ foo = Text, bar = List }` is legal now
    * See: https://github.com/dhall-lang/dhall-haskell/pull/273
* Feature: New `dhall-repl` for interactively evaluating Dhall expressions
    * See: https://github.com/dhall-lang/dhall-haskell/pull/266
* Feature: Syntax highlighting
    * See: https://github.com/dhall-lang/dhall-haskell/pull/260
* Feature: BREAKING CHANGE TO THE API: `dhall-format` preserves field order
    * This changes the syntax tree to use an `InsOrdHashMap` instead of a `Map`
* BREAKING CHANGE TO THE API: Use Haskell's `Scientific` type
    * This is fixes the interpreter to correct handle really large/small numbers
    * This also allows marshaling into Haskell's `Scientific` type
    * See: https://github.com/dhall-lang/dhall-haskell/pull/256
* BREAKING CHANGE TO THE API: Remove `system-filepath`/`system-fileio` dependencies
    * Now the library uses `Prelude.FilePath`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/248
* Feature: Labels can now begin with reserved names
    * i.e. `List/map` is now a legal label
    * See: https://github.com/dhall-lang/dhall-haskell/pull/255
* Fix: Rendered labels are now correctly escaped if they are numbers
    * See: https://github.com/dhall-lang/dhall-haskell/pull/252
* Add the instance `Interpret String`.
    * See: https://github.com/dhall-lang/dhall-haskell/pull/247
* Fix: Custom contexts passed to `typeWith` are now checked
    * This prevents a custom context from triggering an infinite loop
    * See: https://github.com/dhall-lang/dhall-haskell/pull/259

1.9.1

* `dhall-format` now emits single-quoted strings for multi-line strings
    * See: https://github.com/dhall-lang/dhall-haskell/pull/237
* Improved error messages for list elements with the wrong type
    * See: https://github.com/dhall-lang/dhall-haskell/pull/236
* Change `lens` dependency to `lens-family-core`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/238

1.9.0

* Feature: BREAKING CHANGE TO LANGUAGE AND API: Add `constructors` keyword
    * This new keyword generates constructors from a union type
        * See the updated Haskell tutorial for more details
    * This means that `constructors` is now a reserved keyword
    * This adds a new `Constructors` constructor to the `Expr` type
    * See: https://github.com/dhall-lang/dhall-haskell/pull/199
* Feature: BREAKING CHANGE TO THE API: `dhall-format` preserves interpolation
    * This changes the `TextLit` constructor to represent an interpolated `Text`
      literal
    * See: https://github.com/dhall-lang/dhall-haskell/pull/220
* Feature: You can now define type synonyms using `let`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/202
* Feature: Extend valid set of quoted labels
    * See: https://github.com/dhall-lang/dhall-lang/pull/65
    * See: https://github.com/dhall-lang/dhall-lang/pull/77
* Performance: Improve startup time when importing files, but not URLs
    * See: https://github.com/dhall-lang/dhall-haskell/pull/194
* Security: `localhost`/`127.0.0.1` imports no longer count as local imports
    * Specifically: they cannot import environment variables or files
    * See: https://github.com/dhall-lang/dhall-haskell/pull/197
* Security: Fix potential type-checking bug
    * See: https://github.com/dhall-lang/dhall-haskell/pull/198
* Fix: BREAKING CHANGE TO API: Improve localization of error messages
    * This required fixing the type of `normalize`/`shift`/`subst` to preserve
      the first type parameter of `Expr` (i.e. they no longer delete `Note`
      constructors)
    * A new `denote` function was added for the explicit purpose of deleting
      `Note` constructors
    * See: https://github.com/dhall-lang/dhall-haskell/pull/218
* Expose `MissingEnvironmentVariable` exception type
    * See: https://github.com/dhall-lang/dhall-haskell/pull/196
* Add `genericAuto`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/195
* Add `inputWith`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/222
* Add`loadWithContext`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/215
* Add `pair`/`unit`/`string`/`list`
    * See: https://github.com/dhall-lang/dhall-haskell/pull/227

1.8.2

* Add `typeWithA` for type-checking custom `Embed`ded values
* Fix `dhall{,-*}` executables to ignore ambient locale and use UTF8
* Increase upper bound on `tasty` dependency

1.8.1

* `dhall` executable can now format output using `--pretty`
* Improved Unicode suppport on Windows

1.8.0

* BREAKING CHANGE TO LANGUAGE: Add support for import integrity checks
    * In practice, the likelihood of this breaking code in the wild is
      astronomically low
    * This would only break code of the form `sha256:aaa...aaa` (i.e. a
      variabled named `sha256` with a type annotation for a type with a name
      64 characters long drawn from the first 6 characters of the alphabet)
* BUG FIX: Fix parsing of single quotes in single-quoted strings
* BUG FIX: Fix superfluous parentheses introduced by `dhall-format`
* New `dhall-hash` executable
    * This goes hand-in-hand with the added support for integrity checks since
      the executable lets you compute the current hash of an import

1.7.0

* BREAKING CHANGE TO LANGUAGE: Update parser to match standardized grammar
    * Trailing commas and bars no longer supported for union and record literals
    * Paths no longer permit commas
    * URL grammar is now RFC-compliant
    * Environment variables can now be quoted to support full range of
      POSIX-compliant names
    * Text literals support full set of JSON escape sequences (such as `\u2192`)
* BREAKING CHANGE TO LANGUAGE: Single quoted strings strip leading newlines
* BUG FIX: Fixed type-checking infinite loops due to non-type-checked variables
  in context
* BUG FIX: Fixed type-checking bug due to missing context when type-checking
  certain expressions
* BUG FIX: Fixed type-checking bug due to off-by-one errors in name shadowing
  logic
* New `dhall-format` executable to automatically format code
* Performance optimizations to `Natural/fold` and `List/fold`
* Improved parsing performance (over 3x faster)
* Union literals can now specify the set value anywhere in the literal
    * i.e. `< A : Integer | B = False | C : Text >`
* New `Inject` instance for `()`
* Several tutorial fixes and improvements

1.6.0

* BREAKING CHANGE TO THE API: Drop support for GHC 7.*
* BREAKING CHANGE TO THE API: Add support for customizing Dhall import
    * This is a breaking change because this changes the type of `loadWith`
* BREAKING CHANGE TO THE API: Add field to `UnboundVariable` error containing
* BUG FIX: Fix parsing single quotes in string literals
  the name of the unbound variable
* Add `List/concatMap` to the Prelude
* You can now derive `Inject` and `Interpret` for types with unlabeled fields
* Add new instances for `Interpret`:
    * `[]`
    * `(,)`
* Add new instance for `Inject`
    * `[]`, `Data.Set.Set`, `Data.Sequence.Seq`
    * `(,)`
    * `Int`, `Word8`, `Word16`, `Word32`, `Word64`
* Add `Eq` instance for `Src`

1.5.1

* Increase upper bound on `vector` and `optparse-generic`

1.5.0

* BREAKING CHANGE: Add list concatenation operator: `(#)`
    * This is a breaking change because it adds a new constructor to the `Expr`
      type which breaks exhaustive pattern matches
* BREAKING CHANGE: Add `Interpret` support for lazy `Text`
    * This is a breaking change because it renames `text` to `strictText`
* Add `Interpret` instance for decoding (a limited subset of) Dhall functions
* Dhall no longer requires Template Haskell to compile
    * This helps with cross-compilation
* Add `rawInput` utility for decoding a Haskell value from the `Expr` type
* Add `loadWith`/`normalizeWith` utilities for normalizing/importing modules
  with a custom context
* Export `Type` constructor

1.4.2

* Fix missing `Prelude` files in package archive uploaded to Hackage

1.4.1

* Fix missing `tests/Tutorial.hs` module in package archive uploaded to Hackage

1.4.0

* BREAKING CHANGE TO THE LANGUAGE AND API: You can now supply custom headers for
  URL imports with the new `using` keyword
    * This is a breaking change to the language because this adds a new reserved
      `using` keyword
    * This is a breaking change to the API because this adds a new field to the
      `URL` constructor to store optional custom headers
* BUG FIX: `:` is no longer a disallowed path character
    * This was breaking URL imports with a port
* BUG FIX: If you import a home-anchored path (i.e. `~/foo`) and that imports a
  relative path (like `./bar`), then the canonical path of the relative import
  should be home-anchored (i.e. `~/bar`).  However, there was a bug that made
  lose the home anchor (i.e. `./foo/bar`), which this release fixes
  likely fail due to no longer being home-anchored (i.e. `./foob
* Add support for string interpolation
* `merge` no longer requires a type annotation if you are merging at least one
  alternative
* Expanded Prelude
    * `./Prelude/Optional/all`
    * `./Prelude/Optional/any`
    * `./Prelude/Optional/filter`
    * `./Prelude/Optional/length`
    * `./Prelude/Optional/null`
    * `./Prelude/Text/concatMap`
    * `./Prelude/Text/concatMapSep`
    * `./Prelude/Text/concatSep`
* Rearrange detailed error messages to put summary information at the bottom of
  the message

1.3.0

* BREAKING CHANGE TO THE API: Add support for new primitives, specifically:
    * `(//)` - Right-biased and shallow record merge
    * `Optional/build` (now a built-in in order to support build/fold fusion)
    * `Natural/show`
    * `Integer/show`
    * `Double/show`
    * `Natural/toInteger`
    * These all add new constructors to the `Expr` type, which would break
      exhaustive pattern matches
* BREAKING CHANGE TO THE LANGUAGE: Imported paths and URLs no longer support
  the characters: "()[]{}<>:"
    * This reduces the number of cases where you have to add a space after
      imports
    * Note that this does not exclude the `:` in the URL scheme (i.e. `http://`)
* Increase connection timeout for imports
* Variable names now allow the `-` character for all but the first character
* You can now escape identifiers with backticks
    * This lets you name identifiers so that they don't conflict with reserved
      key words
    * This is most useful when converting Dhall to other file formats (like
      JSON) where you might need to emit a field that conflicts with one of
      Dhall's reserved keywords
* New `--version` flag for the `dhall` executable

1.2.0

* BREAKING CHANGE: Add support for customizing derived `Interpret` instances
    * This is a breaking change to the Dhall library API since this changes the
      signature of the `Interpret` class by replacing the `auto` method with a
      more general `autoWith` method.  This `autoWith` now takes an
      `InterpretOptions` argument that lets you customize derived field and
      constuctor names
    * In practice user programs that use the common path will be unaffected by
      this change
    * This is not a breaking change to the Dhall language
* BREAKING CHANGE: Type annotations now bind more tightly than lambda
  abstraction
    * This is a breaking change to the Dhall language.  An expression like this:

      ```
      λ(x : A) → y : B
      ```

      ... used to parenthesized implicitly as:

      ```
      (λ(x : A) → y) : T
      ```

      ... but is now parenthesized implicitly as:

      ```
      λ(x : A) → (y : T)
      ```

      This is now consistent with Haskell's precedence and also consistent with
      the precedence of `List` and `Optional` type annotations

    * This change affects programs with an expression like this:

      ```
      -- Assuming that `y : B`
      λ(x : A) → y : A → B
      ```

      The above program would type-check before this change but not type-check
      after this change.  You would you need to fix the above program by either
      changing the type signature to annotate just the type of `y` like this:

      ```
      λ(x : A) → y : B
      ```

      ... or by adding explicit parentheses like this:

      ```
      (λ(x : A) → y) : A → B
      ```

    * This is not a breaking change to the Dhall library API
* BREAKING CHANGE: Add support for importing a path's contents as raw `Text` by
  adding `as Text` after the import
    * This is a breaking change to the Dhall language
    * This is technically a breaking change, but is extremely unlikely to affect
      you program.  This only changes the behavior of old programs that had an
      expression of the form:

      ```
      /some/imported/function as Text
      ```

      ... where `/some/imported/function` is an imported function being applied
      to two arguments, the first of which is a bound variable named `as` and
      the second of which is the type `Text`
    * This is not a breaking change to the Dhall library API
* BREAKING CHANGE: Add support for importing environment variables using
  `env:VAR` syntax
    * This is a breaking change to the Dhall library API since it adds a new
      `Path` constructor
    * This also technically a breaking change to the Dhall language but
      extremely unlikely to affect your program.  This only changes the behavior
      of old programs that had an expression of the form:

      ```
      env:VAR
      ```

      ... where `env` was the name of a bound variable and `:VAR` was a type
      annotation without spaces around the type annotation operator

      After this change the program would be interpreted as an import of the
      contents for the environment variable named `VAR`
* BREAKING CHANGE: Support importing paths relative to home directory using
  `~/some/path` syntax
    * This is a breaking change to the Dhall library API since it adds a new
      field to the `File` constructor indicating whether or not the imported
      path is relative to the home directory
    * This is not a breaking change to the Dhall language and the new syntax
      does not override any old syntax
* Permit trailing commas and bars in record/union syntax
* Improve location information for parsing errors

1.1.0

* BREAKING CHANGE: Non-empty lists no longer require a type annotation
    * This is a breaking change to the Haskell library, not the Dhall language
    * This change does not break existing Dhall programs
    * The `Expr` type was modified in a non-backwards-compatible way
* Add new `exprA` parser
* Add new `InvalidType` exception if `input` fails on an invalid `Type`
* Improve documentation and tutorial

1.0.2

* Add support for Nix-style "double single-quote" multi-line string literals
* Add `isNormalized`
* Improve documentation and tutorial
* Build against wider range of `http-client` versions

1.0.1

* Initial release

1.0.0

* Accidental premature upload to Hackage.  This release was blacklisted