diff --git a/Library/.rubocop.yml b/Library/.rubocop.yml
index 2fe2394470..d749adc353 100644
--- a/Library/.rubocop.yml
+++ b/Library/.rubocop.yml
@@ -48,6 +48,12 @@ Style/AlignHash:
 Style/AlignParameters:
   Enabled: false
 
+Style/BarePercentLiterals:
+  EnforcedStyle: percent_q
+
+Style/BlockDelimiters:
+  EnforcedStyle: line_count_based
+
 Style/CaseIndentation:
   IndentWhenRelativeTo: end
 
@@ -76,9 +82,11 @@ Style/FileName:
 Style/GuardClause:
   Enabled: false
 
+# depends_on a: :b looks weird in formulae.
 Style/HashSyntax:
   EnforcedStyle: hash_rockets
 
+# disabled until it respects line length
 Style/IfUnlessModifier:
   Enabled: false
 
@@ -133,8 +141,6 @@ Style/StringLiterals:
 Style/StringLiteralsInInterpolation:
   EnforcedStyle: double_quotes
 
-# TODO: enforce when rubocop has shipped this
-# https://github.com/bbatsov/rubocop/pull/3513
 Style/TernaryParentheses:
   Enabled: false
 
@@ -142,15 +148,8 @@ Style/TernaryParentheses:
 Style/TrailingCommaInLiteral:
   EnforcedStyleForMultiline: comma
 
-Style/UnneededCapitalW:
-  Enabled: false
-
-# TODO: enforce when rubocop has fixed this
-# https://github.com/bbatsov/rubocop/issues/3516
 Style/VariableNumber:
   Enabled: false
 
-# TODO: enforce when rubocop has fixed this
-# https://github.com/bbatsov/rubocop/issues/1543
 Style/WordArray:
   Enabled: false
diff --git a/Library/Homebrew/.rubocop.yml b/Library/Homebrew/.rubocop.yml
index f4f80800aa..3256743988 100644
--- a/Library/Homebrew/.rubocop.yml
+++ b/Library/Homebrew/.rubocop.yml
@@ -9,11 +9,19 @@ AllCops:
     - 'cask/**/*'
     - '**/vendor/**/*'
 
+# so many of these in formulae but none in here
+Lint/AmbiguousRegexpLiteral:
+  Enabled: true
+
 # `formula do` uses nested method definitions
 Lint/NestedMethodDefinition:
   Exclude:
     - 'test/**/*'
 
+# so many of these in formulae but none in here
+Lint/ParenthesesAsGroupedExpression:
+  Enabled: false
+
 Metrics/ModuleLength:
   CountComments: false
   Exclude:
@@ -21,81 +29,11 @@ Metrics/ModuleLength:
     - 'cask/lib/hbc/macos.rb'
     - 'cask/lib/hbc/utils.rb'
 
-Style/BarePercentLiterals:
-  EnforcedStyle: percent_q
-
-Style/BlockDelimiters:
-  EnforcedStyle: semantic
-  FunctionalMethods:
-    - expect
-    - find
-    - let
-    - let!
-    - subject
-    - watch
-    - inject
-    - map
-    - map!
-    - collect
-    - collect!
-    - reject
-    - reject!
-    - delete_if
-    - with_object
-    - popen_read
-  ProceduralMethods:
-    - after
-    - at_exit
-    - before
-    - benchmark
-    - bm
-    - bmbm
-    - capture_io
-    - capture_output
-    - capture_subprocess_io
-    - chdir
-    - context
-    - create
-    - define_method
-    - define_singleton_method
-    - fork
-    - measure
-    - new
-    - open
-    - realtime
-    - shutup
-    - tap
-    - each
-    - each_pair
-    - each_with_index
-    - reverse_each
-    - ignore_interrupts
-  IgnoredMethods:
-    - each_with_object
-    - it
-    - its
-    - lambda
-    - proc
-    - formula
-    - mock
-    - devel
-    - stable
-    - head
-    - assert_raises
-    - assert_nothing_raised
-    - resource
-    - with_build_environment
-    - ensure_writable
-    - satisfy
-    - fetch
-    - brew
-    - expand
-    - env
-    - recursive_dependencies
-    - trap
-    - link_dir
-    - with_system_path
+# so many of these in formulae but none in here
+Style/GuardClause:
+  Enabled: true
 
+# hash-rockets preferred for formulae, a: 1 preferred elsewhere
 Style/HashSyntax:
   EnforcedStyle: ruby19_no_mixed_keys
 
@@ -109,4 +47,3 @@ Style/PredicateName:
   Exclude:
     - 'compat/**/*'
   NameWhitelist: is_32_bit?, is_64_bit?
-
diff --git a/Library/Homebrew/cmd/missing.rb b/Library/Homebrew/cmd/missing.rb
index 525461108b..148fe5bef0 100644
--- a/Library/Homebrew/cmd/missing.rb
+++ b/Library/Homebrew/cmd/missing.rb
@@ -20,7 +20,7 @@ module Homebrew
 
     Diagnostic.missing_deps(ff) do |name, missing|
       print "#{name}: " if ff.size > 1
-      puts (missing * " ").to_s
+      puts missing.join(" ")
     end
   end
 end
diff --git a/Library/Homebrew/cmd/style.rb b/Library/Homebrew/cmd/style.rb
index 9538b890a9..08eb111a50 100644
--- a/Library/Homebrew/cmd/style.rb
+++ b/Library/Homebrew/cmd/style.rb
@@ -49,7 +49,7 @@ module Homebrew
     fix = options[:fix]
     Homebrew.install_gem_setup_path! "rubocop", "0.43.0"
 
-    args = %W[
+    args = %w[
       --force-exclusion
     ]
     args << "--auto-correct" if fix
diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index 9a15c6de71..12eaf9167e 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -137,7 +137,7 @@ class FormulaAuditor
 
   attr_reader :formula, :text, :problems
 
-  BUILD_TIME_DEPS = %W[
+  BUILD_TIME_DEPS = %w[
     autoconf
     automake
     boost-build
@@ -449,9 +449,8 @@ class FormulaAuditor
     end
 
     return unless @new_formula
-    unless formula.deprecated_options.empty?
-      problem "New formulae should not use `deprecated_option`."
-    end
+    return if formula.deprecated_options.empty?
+    problem "New formulae should not use `deprecated_option`."
   end
 
   def audit_desc
diff --git a/Library/Homebrew/extend/ENV/super.rb b/Library/Homebrew/extend/ENV/super.rb
index a3837c695a..a75cba406d 100644
--- a/Library/Homebrew/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/ENV/super.rb
@@ -139,7 +139,7 @@ module Superenv
   end
 
   def determine_pkg_config_libdir
-    paths = %W[/usr/lib/pkgconfig]
+    paths = %w[/usr/lib/pkgconfig]
     paths += homebrew_extra_pkg_config_paths
     paths.to_path_s
   end
diff --git a/Library/Homebrew/locale.rb b/Library/Homebrew/locale.rb
index e749a5004c..5e778f3b4d 100644
--- a/Library/Homebrew/locale.rb
+++ b/Library/Homebrew/locale.rb
@@ -51,20 +51,20 @@ class Locale
   def include?(other)
     other = self.class.parse(other) unless other.is_a?(self.class)
 
-    [:language, :region, :script].all? { |var|
+    [:language, :region, :script].all? do |var|
       if other.public_send(var).nil?
         true
       else
         public_send(var) == other.public_send(var)
       end
-    }
+    end
   end
 
   def eql?(other)
     other = self.class.parse(other) unless other.is_a?(self.class)
-    [:language, :region, :script].all? { |var|
+    [:language, :region, :script].all? do |var|
       public_send(var) == other.public_send(var)
-    }
+    end
   rescue ParserError
     false
   end
diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index d970a0a37f..3659abe4ff 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -206,7 +206,7 @@ class Tap
       end
 
       ohai "Unshallowing #{name}" unless quiet
-      args = %W[fetch --unshallow]
+      args = %w[fetch --unshallow]
       args << "-q" if quiet
       path.cd { safe_system "git", *args }
       return
diff --git a/Library/Homebrew/utils/formatter.rb b/Library/Homebrew/utils/formatter.rb
index 4685e8c5db..8a9afb9af4 100644
--- a/Library/Homebrew/utils/formatter.rb
+++ b/Library/Homebrew/utils/formatter.rb
@@ -78,9 +78,9 @@ module Formatter
     rows.times do |row_index|
       item_indices_for_row = row_index.step(objects.size - 1, rows).to_a
 
-      first_n = item_indices_for_row[0...-1].map { |index|
+      first_n = item_indices_for_row[0...-1].map do |index|
         objects[index] + "".rjust(col_width - object_lengths[index])
-      }
+      end
 
       # don't add trailing whitespace to last column
       last = objects.values_at(item_indices_for_row.last)