This release brings 8 new rules, as well as important bug fixes and improvements to existing ones.
We also temporarily disabled the cache when linting until some important cache-related issues are addressed in a future version.

Breaking

• variable_name rule (VariableNameRule) is now identifier_name
  (IdentifierNameRule) as it validates other identifiers as well.
  Marcelo Fabri
  #663

• Fix sorted_imports rule to sort ignoring case.
  Keith Smiley
  #1185

• Temporarily disable cache when linting. This will be re-enabled in a future
  version after important cache-related issues have been addressed.
  Marcelo Fabri

Enhancements

• Add implicitly_unwrapped_optional opt-in rule that warns against using
  implicitly unwrapped optionals, except cases when this IUO is an IBOutlet.
  Siarhei Fedartsou
  #56

• Performance improvements to generic_type_name, redundant_nil_coalescing,
  mark, first_where and vertical_whitespace rules.
  Marcelo Fabri

• Add discarded_notification_center_observer rule that warns when the result
  of NotificationCenter.addObserver(forName:object:queue:using:) is not stored
  so it can be removed later.
  Marcelo Fabri
  #1062

• Add notification_center_detachment rule that warns against an object
  removing itself from NotificationCenter in an unsafe location.
  Marcelo Fabri
  #1061

• Accept AnyObject and NSObjectProtocol in class_delegate_protocol.
  Jon Shier
  #1261

• Add ignores_function_declarations and ignores_comments as options to
  LineLengthRule.
  Michael L. Welles
  #598
  #975

• Add for_where rule that validates that where is used in a for loop
  instead of a single if expression inside the loop.
  Marcelo Fabri
  #1228

• unused_enumerated rule now warns when only the index is being used.
  You should use .indices instead of .enumerated() in this case.
  Marcelo Fabri
  #1278

• Add ignores_case_statements as option to CyclomaticComplexityRule.
  Michael L. Welles
  #1298

• Add correctable redundant_discardable_let rule that warns when
  let _ = foo() is used to discard a result from a function instead of
  _ = foo().
  Marcelo Fabri
  #1232

• Accept global and local variables in implicit_getter rule.
  Marcelo Fabri

• Add --enabled (or -e) switch to the rules CLI command, to only display
  enabled rules.
  Natan Rolnik
  #1270

• Now nesting rule can be configured with a type and statement level.
  Hayashi Tatsuya
  #1318

• Add explicit_type_interface opt-in rule that validates that the properties
  have an explicit type interface.
  Kim de Vos

• Add --lenient CLI option to lint command. Facilitates running a lint task
  that doesn't fail a pipeline of other tasks.
  aaroncrespo
  #1322

• Add fatal_error_message opt-in rule that validates that fatalError() calls
  have a message.
  Kim de Vos
  #1348

Bug Fixes

• Fix crashes when accessing cached regular expressions when linting in
  parallel.
  JP Simard
  #1344

• Fix a false positive on large_tuple rule when using closures.
  Marcelo Fabri
  #1234

• Fix force_unwrap false positive for bool negation.
  Aaron McTavish
  #918

• Fix false positive and wrong correction on number_separator rule.
  Marcelo Fabri
  #1242

• Retain closure parameter types when they are specified during autocorrect.
  Allen Zeng
  #1175

• Fix redundant_void_return matches if return type starts with Void~.
  Hayashi Tatsuya

• Ignore unused_closure_parameter rule on closures that are called inline.
  Marcelo Fabri
  #1161

• Disable valid_docs and missing_docs rules when running in Swift 2.3 or
  later as they have not been updated to work with those versions of Swift.
  Both rules are now opt-in because of this.
  JP Simard
  #728

• Fix false positive on large_tuple rule when using generics inside a tuple.
  Marcelo Fabri
  #1257

• Make ASTRule default implementation to navigate through the substructure
  even if its children are from a different kind. This fixes some violations not
  being reported in some contexts.
  Marcelo Fabri
  #1237

• Reimplement switch_case_on_newline rule to be an ASTRule and be more
  reliable, fixing some false negatives and false positives.
  Marcelo Fabri
  #1268

• Fix closure_end_indentation rule false positive when using single-line
  closures.
  Marcelo Fabri
  #1216

• Fix todo rule messages when the comment is not on a new line.
  Marcelo Fabri
  #1304

• Fix false negative on unused_closure_parameter rule.
  Hayashi Tatsuya

• Fix checkstyle report format.
  Yuki Oya