Add more type signatures.

Library/.rubocop.yml

@@ -297,15 +297,9 @@ Sorbet/ConstantsFromStrings:
 Style/AccessModifierDeclarations:
   Enabled: false
 
-# don't group nicely documented or private attr_readers
+# Conflicts with type signatures on `attr_*`s.
 Style/AccessorGrouping:
-  Exclude:
-    - 'Homebrew/formula.rb'
-    - 'Homebrew/formulary.rb'
-    - 'Homebrew/migrator.rb'
-    - 'Homebrew/resource.rb'
-    - 'Homebrew/system_command.rb'
-    - 'Homebrew/tap.rb'
+  Enabled: false
 
 # make rspec formatting more flexible
 Style/BlockDelimiters:

Library/Homebrew/bintray.rb

@@ -8,6 +8,8 @@ require "json"
 #
 # @api private
 class Bintray
+  extend T::Sig
+
   include Context
 
   API_URL = "https://api.bintray.com"
@@ -15,6 +17,7 @@ class Bintray
   class Error < RuntimeError
   end
 
+  sig { returns(String) }
   def inspect
     "#<Bintray: org=#{@bintray_org}>"
   end

Library/Homebrew/cask/artifact/abstract_artifact.rb

@@ -7,6 +7,8 @@ module Cask
     #
     # @api private
     class AbstractArtifact
+      extend T::Sig
+
       include Comparable
       extend Predicable
 
@@ -132,6 +134,7 @@ module Cask
         cask.config
       end
 
+      sig { returns(String) }
       def to_s
         "#{summarize} (#{self.class.english_name})"
       end

Library/Homebrew/cask/artifact/abstract_uninstall.rb

@@ -15,6 +15,8 @@ module Cask
     #
     # @api private
     class AbstractUninstall < AbstractArtifact
+      extend T::Sig
+
       ORDERED_DIRECTIVES = [
         :early_script,
         :launchctl,
@@ -53,6 +55,7 @@ module Cask
         directives.to_h
       end
 
+      sig { returns(String) }
       def summarize
         to_h.flat_map { |key, val| Array(val).map { |v| "#{key.inspect} => #{v.inspect}" } }.join(", ")
       end
@@ -128,6 +131,7 @@ module Cask
           end
       end
 
+      sig { returns(String) }
       def automation_access_instructions
         "Enable Automation Access for “Terminal > System Events” in " \
         "“System Preferences > Security > Privacy > Automation” if you haven't already."

Library/Homebrew/cask/artifact/artifact.rb

@@ -12,6 +12,9 @@ module Cask
     #
     # @api private
     class Artifact < Moved
+      extend T::Sig
+
+      sig { returns(String) }
       def self.english_name
         "Generic Artifact"
       end

Library/Homebrew/cask/artifact/mdimporter.rb

@@ -9,6 +9,9 @@ module Cask
     #
     # @api private
     class Mdimporter < Moved
+      extend T::Sig
+
+      sig { returns(String) }
       def self.english_name
         "Spotlight metadata importer"
       end

Library/Homebrew/cask/artifact/moved.rb

@@ -9,6 +9,9 @@ module Cask
     #
     # @api private
     class Moved < Relocated
+      extend T::Sig
+
+      sig { returns(String) }
       def self.english_description
         "#{english_name}s"
       end

Library/Homebrew/cask/artifact/prefpane.rb

@@ -9,6 +9,9 @@ module Cask
     #
     # @api private
     class Prefpane < Moved
+      extend T::Sig
+
+      sig { returns(String) }
       def self.english_name
         "Preference Pane"
       end

Library/Homebrew/cask/artifact/qlplugin.rb

@@ -9,6 +9,9 @@ module Cask
     #
     # @api private
     class Qlplugin < Moved
+      extend T::Sig
+
+      sig { returns(String) }
       def self.english_name
         "QuickLook Plugin"
       end

Library/Homebrew/cask/artifact/relocated.rb

@@ -12,6 +12,8 @@ module Cask
     #
     # @api private
     class Relocated < AbstractArtifact
+      extend T::Sig
+
       def self.from_args(cask, *args)
         source_string, target_hash = args
 
@@ -49,6 +51,7 @@ module Cask
         end
       end
 
+      sig { returns(String) }
       def summarize
         target_string = @target_string.empty? ? "" : " -> #{@target_string}"
         "#{@source_string}#{target_string}"

Library/Homebrew/cask/artifact/stage_only.rb

@@ -9,16 +9,20 @@ module Cask
     #
     # @api private
     class StageOnly < AbstractArtifact
+      extend T::Sig
+
       def self.from_args(cask, *args)
         raise CaskInvalidError.new(cask.token, "'stage_only' takes only a single argument: true") if args != [true]
 
         new(cask)
       end
 
+      sig { returns(T::Array[T::Boolean]) }
       def to_a
         [true]
       end
 
+      sig { returns(String) }
       def summarize
         "true"
       end

Library/Homebrew/cask/artifact/suite.rb

@@ -9,10 +9,14 @@ module Cask
     #
     # @api private
     class Suite < Moved
+      extend T::Sig
+
+      sig { returns(String) }
       def self.english_name
         "App Suite"
       end
 
+      sig { returns(Symbol) }
       def self.dirmethod
         :appdir
       end

Library/Homebrew/cask/artifact/symlinked.rb

@@ -9,10 +9,14 @@ module Cask
     #
     # @api private
     class Symlinked < Relocated
+      extend T::Sig
+
+      sig { returns(String) }
       def self.link_type_english_name
         "Symlink"
       end
 
+      sig { returns(String) }
       def self.english_description
         "#{english_name} #{link_type_english_name}s"
       end

Library/Homebrew/cask/audit.rb

@@ -13,6 +13,8 @@ module Cask
   #
   # @api private
   class Audit
+    extend T::Sig
+
     extend Predicable
 
     attr_reader :cask, :download
@@ -117,6 +119,7 @@ module Cask
       end
     end
 
+    sig { returns(String) }
     def summary
       summary = ["audit for #{cask}: #{result}"]
 
@@ -416,6 +419,7 @@ module Cask
       core_tap.formula_names
     end
 
+    sig { returns(String) }
     def core_formula_url
       "#{core_tap.default_remote}/blob/HEAD/Formula/#{cask.token}.rb"
     end

Library/Homebrew/cask/cask.rb

@@ -12,6 +12,8 @@ module Cask
   #
   # @api private
   class Cask
+    extend T::Sig
+
     extend Enumerable
     extend Forwardable
     extend Searchable
@@ -64,6 +66,7 @@ module Cask
       define_method(method_name) { |&block| @dsl.send(method_name, &block) }
     end
 
+    sig { returns(T::Array[[String, String]]) }
     def timestamped_versions
       Pathname.glob(metadata_timestamped_path(version: "*", timestamp: "*"))
               .map { |p| p.relative_path_from(p.parent.parent) }
@@ -89,6 +92,7 @@ module Cask
       !versions.empty?
     end
 
+    sig { returns(T.nilable(Time)) }
     def install_time
       _, time = timestamped_versions.last
       return unless time

Library/Homebrew/cask/cask_loader.rb

@@ -90,6 +90,8 @@ module Cask
 
     # Loads a cask from a URI.
     class FromURILoader < FromPathLoader
+      extend T::Sig
+
       def self.can_load?(ref)
         uri_regex = ::URI::DEFAULT_PARSER.make_regexp
         return false unless ref.to_s.match?(Regexp.new("\\A#{uri_regex.source}\\Z", uri_regex.options))
@@ -103,6 +105,7 @@ module Cask
 
       attr_reader :url
 
+      sig { params(url: T.any(URI::Generic, String)).void }
       def initialize(url)
         @url = URI(url)
         super Cache.path/File.basename(@url.path)
@@ -177,10 +180,13 @@ module Cask
 
     # Pseudo-loader which raises an error when trying to load the corresponding cask.
     class NullLoader < FromPathLoader
+      extend T::Sig
+
       def self.can_load?(*)
         true
       end
 
+      sig { params(ref: T.any(String, Pathname)).void }
       def initialize(ref)
         token = File.basename(ref, ".rb")
         super CaskLoader.default_path(token)

Library/Homebrew/cask/cmd.rb

@@ -38,6 +38,8 @@ module Cask
   #
   # @api private
   class Cmd
+    extend T::Sig
+
     include Context
 
     ALIASES = {
@@ -61,6 +63,7 @@ module Cask
       Cmd::Upgrade   => "brew upgrade --cask",
     }.freeze
 
+    sig { returns(String) }
     def self.description
       max_command_length = Cmd.commands.map(&:length).max
 

Library/Homebrew/cask/cmd/--cache.rb

@@ -7,18 +7,24 @@ module Cask
     #
     # @api private
     class Cache < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
 
+      sig { returns(String) }
       def self.description
         "Display the file used to cache a <cask>."
       end
 
+      sig { returns(String) }
       def self.command_name
         "--cache"
       end
 
+      sig { void }
       def run
         casks.each do |cask|
           puts self.class.cached_location(cask)

Library/Homebrew/cask/cmd/abstract_command.rb

@@ -9,16 +9,22 @@ module Cask
     #
     # @api private
     class AbstractCommand
+      extend T::Sig
+      extend T::Helpers
+
       include Homebrew::Search
 
+      sig { returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         nil
       end
 
+      sig { returns(T.nilable(Integer)) }
       def self.max_named
         nil
       end
 
+      sig { returns(String) }
       def self.banner_args
         if min_named == :cask && max_named != 1
           " <cask>"
@@ -29,6 +35,7 @@ module Cask
         end
       end
 
+      sig { returns(String) }
       def self.banner_headline
         "`#{command_name}` [<options>]#{banner_args}"
       end
@@ -72,24 +79,29 @@ module Cask
         end
       end
 
+      sig { returns(String) }
       def self.command_name
         @command_name ||= name.sub(/^.*:/, "").gsub(/(.)([A-Z])/, '\1_\2').downcase
       end
 
+      sig { returns(T::Boolean) }
       def self.abstract?
         name.split("::").last.match?(/^Abstract[^a-z]/)
       end
 
+      sig { returns(T::Boolean) }
       def self.visible?
         true
       end
 
+      sig { returns(String) }
       def self.help
         parser.generate_help_text
       end
 
+      sig { returns(String) }
       def self.short_description
-        description.split(".").first
+        description[/\A[^.]*\./]
       end
 
       def self.run(*args)

Library/Homebrew/cask/cmd/abstract_internal_command.rb

@@ -7,10 +7,14 @@ module Cask
     #
     # @api private
     class AbstractInternalCommand < AbstractCommand
+      extend T::Sig
+
+      sig { returns(String) }
       def self.command_name
         super.sub(/^internal_/i, "_")
       end
 
+      sig { returns(T::Boolean) }
       def self.visible?
         false
       end

Library/Homebrew/cask/cmd/audit.rb

@@ -9,6 +9,9 @@ module Cask
     #
     # @api private
     class Audit < AbstractCommand
+      extend T::Sig
+
+      sig { returns(String) }
       def self.description
         <<~EOS
           Check <cask> for Homebrew coding style violations. This should be run before
@@ -37,6 +40,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         require "cask/auditor"
 

Library/Homebrew/cask/cmd/cat.rb

@@ -7,14 +7,19 @@ module Cask
     #
     # @api private
     class Cat < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
 
+      sig { returns(String) }
       def self.description
         "Dump raw source of a <cask> to the standard output."
       end
 
+      sig { void }
       def run
         casks.each do |cask|
           if Homebrew::EnvConfig.bat?

Library/Homebrew/cask/cmd/create.rb

@@ -7,14 +7,19 @@ module Cask
     #
     # @api private
     class Create < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
 
+      sig { override.returns(T.nilable(Integer)) }
       def self.max_named
         1
       end
 
+      sig { returns(String) }
       def self.description
         "Creates the given <cask> and opens it in an editor."
       end
@@ -25,6 +30,7 @@ module Cask
         raise UsageError, "Only one cask can be created at a time."
       end
 
+      sig { void }
       def run
         cask_token = args.named.first
         cask_path = CaskLoader.path(cask_token)

Library/Homebrew/cask/cmd/doctor.rb

@@ -7,14 +7,19 @@ module Cask
     #
     # @api private
     class Doctor < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(Integer)) }
       def self.max_named
         0
       end
 
+      sig { returns(String) }
       def self.description
         "Checks for configuration issues."
       end
 
+      sig { void }
       def run
         require "diagnostic"
 

Library/Homebrew/cask/cmd/edit.rb

@@ -7,14 +7,19 @@ module Cask
     #
     # @api private
     class Edit < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
 
+      sig { override.returns(T.nilable(Integer)) }
       def self.max_named
         1
       end
 
+      sig { returns(String) }
       def self.description
         "Open the given <cask> for editing."
       end
@@ -25,6 +30,7 @@ module Cask
         raise UsageError, "Only one cask can be edited at a time."
       end
 
+      sig { void }
       def run
         exec_editor cask_path
       rescue CaskUnavailableError => e

Library/Homebrew/cask/cmd/fetch.rb

@@ -7,6 +7,9 @@ module Cask
     #
     # @api private
     class Fetch < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
@@ -18,10 +21,12 @@ module Cask
         end
       end
 
+      sig { returns(String) }
       def self.description
         "Downloads remote application files to local cache."
       end
 
+      sig { void }
       def run
         require "cask/download"
         require "cask/installer"

Library/Homebrew/cask/cmd/help.rb

@@ -7,14 +7,19 @@ module Cask
     #
     # @api private
     class Help < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(Integer)) }
       def self.max_named
         1
       end
 
+      sig { returns(String) }
       def self.description
         "Print help for `cask` commands."
       end
 
+      sig { void }
       def run
         if args.named.empty?
           puts Cmd.parser.generate_help_text

Library/Homebrew/cask/cmd/home.rb

@@ -7,10 +7,14 @@ module Cask
     #
     # @api private
     class Home < AbstractCommand
+      extend T::Sig
+
+      sig { returns(String) }
       def self.description
         "Opens the homepage of the given <cask>. If no cask is given, opens the Homebrew homepage."
       end
 
+      sig { void }
       def run
         if casks.none?
           odebug "Opening project homepage"

Library/Homebrew/cask/cmd/info.rb

@@ -9,10 +9,14 @@ module Cask
     #
     # @api private
     class Info < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
 
+      sig { returns(String) }
       def self.description
         "Displays information about the given <cask>."
       end
@@ -42,6 +46,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         if args.json == "v1"
           puts JSON.generate(args.named.to_casks.map(&:to_h))

Library/Homebrew/cask/cmd/install.rb

@@ -7,10 +7,14 @@ module Cask
     #
     # @api private
     class Install < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
 
+      sig { returns(String) }
       def self.description
         "Installs the given <cask>."
       end
@@ -34,6 +38,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         self.class.install_casks(
           *casks,

Library/Homebrew/cask/cmd/internal_help.rb

@@ -7,14 +7,19 @@ module Cask
     #
     # @api private
     class InternalHelp < AbstractInternalCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(Integer)) }
       def self.max_named
         0
       end
 
+      sig { returns(String) }
       def self.description
         "Print help for unstable internal-use commands."
       end
 
+      sig { void }
       def run
         max_command_len = Cmd.commands.map(&:length).max
         puts "Unstable Internal-use Commands:\n\n"

Library/Homebrew/cask/cmd/internal_stanza.rb

@@ -9,6 +9,8 @@ module Cask
     #
     # @api private
     class InternalStanza < AbstractInternalCommand
+      extend T::Sig
+
       # Syntax
       #
       #     brew cask _stanza <stanza_name> [ --quiet ] [ --table | --yaml ] [ <cask_token> ... ]
@@ -24,14 +26,17 @@ module Cask
         (DSL::ORDINARY_ARTIFACT_CLASSES.map(&:dsl_key) +
          DSL::ARTIFACT_BLOCK_CLASSES.map(&:dsl_key)).freeze
 
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         1
       end
 
+      sig { returns(String) }
       def self.banner_args
         " <stanza_name> [<cask>]"
       end
 
+      sig { returns(String) }
       def self.description
         <<~EOS
           Extract and render a specific stanza for the given <cask>.
@@ -80,6 +85,7 @@ module Cask
         EOS
       end
 
+      sig { void }
       def run
         if ARTIFACTS.include?(stanza)
           artifact_name = stanza

Library/Homebrew/cask/cmd/list.rb

@@ -9,6 +9,9 @@ module Cask
     #
     # @api private
     class List < AbstractCommand
+      extend T::Sig
+
+      sig { returns(String) }
       def self.description
         "Lists installed casks or the casks provided in the arguments."
       end
@@ -26,6 +29,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         self.class.list_casks(
           *casks,

Library/Homebrew/cask/cmd/outdated.rb

@@ -7,6 +7,9 @@ module Cask
     #
     # @api private
     class Outdated < AbstractCommand
+      extend T::Sig
+
+      sig { returns(String) }
       def self.description
         "List the outdated installed casks."
       end
@@ -20,6 +23,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         outdated_casks = casks(alternative: -> { Caskroom.casks(config: Config.from_args(args)) }).select do |cask|
           odebug "Checking update info of Cask #{cask}"

Library/Homebrew/cask/cmd/reinstall.rb

@@ -7,10 +7,14 @@ module Cask
     #
     # @api private
     class Reinstall < Install
+      extend T::Sig
+
+      sig { returns(String) }
       def self.description
         "Reinstalls the given <cask>."
       end
 
+      sig { void }
       def run
         self.class.reinstall_casks(
           *casks,

Library/Homebrew/cask/cmd/style.rb

@@ -10,6 +10,9 @@ module Cask
     #
     # @api private
     class Style < AbstractCommand
+      extend T::Sig
+
+      sig { returns(String) }
       def self.description
         "Checks style of the given <cask> using RuboCop."
       end
@@ -21,6 +24,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         success = Homebrew::Style.check_style_and_print(
           cask_paths,

Library/Homebrew/cask/cmd/uninstall.rb

@@ -7,10 +7,14 @@ module Cask
     #
     # @api private
     class Uninstall < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
 
+      sig { returns(String) }
       def self.description
         "Uninstalls the given <cask>."
       end
@@ -23,6 +27,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         self.class.uninstall_casks(
           *casks,

Library/Homebrew/cask/cmd/upgrade.rb

@@ -10,6 +10,9 @@ module Cask
     #
     # @api private
     class Upgrade < AbstractCommand
+      extend T::Sig
+
+      sig { returns(String) }
       def self.description
         "Upgrades all outdated casks or the specified casks."
       end
@@ -36,6 +39,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         verbose = ($stdout.tty? || args.verbose?) && !args.quiet?
         self.class.upgrade_casks(

Library/Homebrew/cask/cmd/zap.rb

@@ -7,10 +7,14 @@ module Cask
     #
     # @api private
     class Zap < AbstractCommand
+      extend T::Sig
+
+      sig { override.returns(T.nilable(T.any(Integer, Symbol))) }
       def self.min_named
         :cask
       end
 
+      sig { returns(String) }
       def self.description
         <<~EOS
           Zaps all files associated with the given <cask>. Implicitly also performs all actions associated with `uninstall`.
@@ -26,6 +30,7 @@ module Cask
         end
       end
 
+      sig { void }
       def run
         require "cask/installer"
 

Library/Homebrew/cask/denylist.rb

@@ -1,4 +1,4 @@
-# typed: true
+# typed: strict
 # frozen_string_literal: true
 
 module Cask
@@ -6,6 +6,9 @@ module Cask
   #
   # @api private
   module Denylist
+    extend T::Sig
+
+    sig { params(name: String).returns(T.nilable(String)) }
     def self.reason(name)
       case name
       when /^adobe-(after|illustrator|indesign|photoshop|premiere)/

Library/Homebrew/cask/dsl/version.rb

@@ -7,6 +7,8 @@ module Cask
     #
     # @api private
     class Version < ::String
+      extend T::Sig
+
       DIVIDERS = {
         "." => :dots,
         "-" => :hyphens,
@@ -62,6 +64,7 @@ module Cask
 
       attr_reader :raw_version
 
+      sig { params(raw_version: T.nilable(T.any(String, Symbol))).void }
       def initialize(raw_version)
         @raw_version = raw_version
         super(raw_version.to_s)
@@ -73,6 +76,7 @@ module Cask
         raw_version.scan(INVALID_CHARACTERS)
       end
 
+      sig { returns(T::Boolean) }
       def unstable?
         return false if latest?
 
@@ -84,6 +88,7 @@ module Cask
         false
       end
 
+      sig { returns(T::Boolean) }
       def latest?
         to_s == "latest"
       end
@@ -134,6 +139,7 @@ module Cask
 
       private
 
+      sig { returns(T.self_type) }
       def version
         return self if empty? || latest?
 

Library/Homebrew/cask/exceptions.rb

@@ -11,12 +11,15 @@ module Cask
   #
   # @api private
   class MultipleCaskErrors < CaskError
+    extend T::Sig
+
     def initialize(errors)
       super()
 
       @errors = errors
     end
 
+    sig { returns(String) }
     def to_s
       <<~EOS
         Problems with multiple casks:
@@ -29,12 +32,18 @@ module Cask
   #
   # @api private
   class AbstractCaskErrorWithToken < CaskError
-    attr_reader :token, :reason
+    extend T::Sig
+
+    sig { returns(String) }
+    attr_reader :token
+
+    sig { returns(String) }
+    attr_reader :reason
 
     def initialize(token, reason = nil)
       super()
 
-      @token = token
+      @token = token.to_s
       @reason = reason.to_s
     end
   end
@@ -43,6 +52,9 @@ module Cask
   #
   # @api private
   class CaskNotInstalledError < AbstractCaskErrorWithToken
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       "Cask '#{token}' is not installed."
     end
@@ -52,6 +64,8 @@ module Cask
   #
   # @api private
   class CaskConflictError < AbstractCaskErrorWithToken
+    extend T::Sig
+
     attr_reader :conflicting_cask
 
     def initialize(token, conflicting_cask)
@@ -59,6 +73,7 @@ module Cask
       @conflicting_cask = conflicting_cask
     end
 
+    sig { returns(String) }
     def to_s
       "Cask '#{token}' conflicts with '#{conflicting_cask}'."
     end
@@ -68,6 +83,9 @@ module Cask
   #
   # @api private
   class CaskUnavailableError < AbstractCaskErrorWithToken
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       "Cask '#{token}' is unavailable#{reason.empty? ? "." : ": #{reason}"}"
     end
@@ -77,6 +95,9 @@ module Cask
   #
   # @api private
   class CaskUnreadableError < CaskUnavailableError
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       "Cask '#{token}' is unreadable#{reason.empty? ? "." : ": #{reason}"}"
     end
@@ -86,6 +107,9 @@ module Cask
   #
   # @api private
   class CaskAlreadyCreatedError < AbstractCaskErrorWithToken
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       %Q(Cask '#{token}' already exists. Run #{Formatter.identifier("brew cask edit #{token}")} to edit it.)
     end
@@ -95,6 +119,9 @@ module Cask
   #
   # @api private
   class CaskAlreadyInstalledError < AbstractCaskErrorWithToken
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       <<~EOS
         Cask '#{token}' is already installed.
@@ -109,6 +136,9 @@ module Cask
   #
   # @api private
   class CaskX11DependencyError < AbstractCaskErrorWithToken
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       <<~EOS
         Cask '#{token}' requires XQuartz/X11, which can be installed using Homebrew Cask by running:
@@ -124,6 +154,9 @@ module Cask
   #
   # @api private
   class CaskCyclicDependencyError < AbstractCaskErrorWithToken
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       "Cask '#{token}' includes cyclic dependencies on other Casks#{reason.empty? ? "." : ": #{reason}"}"
     end
@@ -133,6 +166,9 @@ module Cask
   #
   # @api private
   class CaskSelfReferencingDependencyError < CaskCyclicDependencyError
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       "Cask '#{token}' depends on itself."
     end
@@ -142,6 +178,9 @@ module Cask
   #
   # @api private
   class CaskUnspecifiedError < CaskError
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       "This command requires a Cask token."
     end
@@ -151,6 +190,9 @@ module Cask
   #
   # @api private
   class CaskInvalidError < AbstractCaskErrorWithToken
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       "Cask '#{token}' definition is invalid#{reason.empty? ? "." : ": #{reason}"}"
     end
@@ -182,6 +224,9 @@ module Cask
   #
   # @api private
   class CaskSha256MissingError < CaskSha256Error
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       <<~EOS
         Cask '#{token}' requires a checksum:
@@ -194,6 +239,8 @@ module Cask
   #
   # @api private
   class CaskSha256MismatchError < CaskSha256Error
+    extend T::Sig
+
     attr_reader :path
 
     def initialize(token, expected, actual, path)
@@ -201,6 +248,7 @@ module Cask
       @path = path
     end
 
+    sig { returns(String) }
     def to_s
       <<~EOS
         Checksum for Cask '#{token}' does not match.
@@ -218,6 +266,9 @@ module Cask
   #
   # @api private
   class CaskNoShasumError < CaskSha256Error
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       <<~EOS
         Cask '#{token}' does not have a sha256 checksum defined and was not installed.
@@ -230,6 +281,8 @@ module Cask
   #
   # @api private
   class CaskQuarantineError < CaskError
+    extend T::Sig
+
     attr_reader :path, :reason
 
     def initialize(path, reason)
@@ -239,6 +292,7 @@ module Cask
       @reason = reason
     end
 
+    sig { returns(String) }
     def to_s
       s = +"Failed to quarantine #{path}."
 
@@ -256,6 +310,9 @@ module Cask
   #
   # @api private
   class CaskQuarantinePropagationError < CaskQuarantineError
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       s = +"Failed to quarantine one or more files within #{path}."
 
@@ -273,6 +330,9 @@ module Cask
   #
   # @api private
   class CaskQuarantineReleaseError < CaskQuarantineError
+    extend T::Sig
+
+    sig { returns(String) }
     def to_s
       s = +"Failed to release #{path} from quarantine."
 

Library/Homebrew/cask/installer.rb

@@ -18,6 +18,8 @@ module Cask
   #
   # @api private
   class Installer
+    extend T::Sig
+
     extend Predicable
     # TODO: it is unwise for Cask::Staged to be a module, when we are
     #       dealing with both staged and unstaged casks here. This should
@@ -142,6 +144,7 @@ module Cask
       Installer.new(installed_cask, binaries: binaries?, verbose: verbose?, force: true, upgrade: upgrade?).uninstall
     end
 
+    sig { returns(String) }
     def summary
       s = +""
       s << "#{Homebrew::EnvConfig.install_badge}  " unless Homebrew::EnvConfig.no_emoji?

Library/Homebrew/cask/quarantine.rb

@@ -9,6 +9,8 @@ module Cask
   #
   # @api private
   module Quarantine
+    extend T::Sig
+
     module_function
 
     QUARANTINE_ATTRIBUTE = "com.apple.quarantine"
@@ -25,6 +27,7 @@ module Cask
     end
     private :xattr
 
+    sig { returns(Symbol) }
     def check_quarantine_support
       odebug "Checking quarantine support"
 

Library/Homebrew/cask/utils.rb

@@ -13,6 +13,8 @@ module Cask
   #
   # @api private
   module Utils
+    extend T::Sig
+
     def self.gain_permissions_remove(path, command: SystemCommand)
       if path.respond_to?(:rmtree) && path.exist?
         gain_permissions(path, ["-R"], command) do |p|
@@ -72,10 +74,12 @@ module Cask
       end
     end
 
+    sig { params(path: Pathname).returns(T::Boolean) }
     def self.path_occupied?(path)
-      File.exist?(path) || File.symlink?(path)
+      path.exist? || path.symlink?
     end
 
+    sig { returns(String) }
     def self.error_message_with_suggestions
       <<~EOS
         Follow the instructions here:

Library/Homebrew/cli/args.rb

@@ -7,11 +7,14 @@ require "ostruct"
 module Homebrew
   module CLI
     class Args < OpenStruct
+      extend T::Sig
+
       attr_reader :options_only, :flags_only
 
       # undefine tap to allow --tap argument
       undef tap
 
+      sig { void }
       def initialize
         super()
 
@@ -131,6 +134,7 @@ module Homebrew
         flag_with_value.delete_prefix(arg_prefix)
       end
 
+      sig { returns(Context::ContextStruct) }
       def context
         Context::ContextStruct.new(debug: debug?, quiet: quiet?, verbose: verbose?)
       end

Library/Homebrew/cli/parser.rb

@@ -14,6 +14,8 @@ OPTION_DESC_WIDTH = 43
 module Homebrew
   module CLI
     class Parser
+      extend T::Sig
+
       attr_reader :processed_options, :hide_from_man_page
 
       def self.from_cmd_path(cmd_path)
@@ -94,6 +96,7 @@ module Homebrew
         ]
       end
 
+      sig { returns(T::Array[[String, String, String]]) }
       def self.global_options
         [
           ["-d", "--debug",   "Display any debugging information."],
@@ -103,6 +106,9 @@ module Homebrew
         ]
       end
 
+      # FIXME: Block should be `T.nilable(T.proc.bind(Parser).void)`.
+      # See https://github.com/sorbet/sorbet/issues/498.
+      sig { params(block: T.proc.bind(Parser).void).void.checked(:never) }
       def initialize(&block)
         @parser = OptionParser.new
 
@@ -331,6 +337,7 @@ module Homebrew
         end
       end
 
+      sig { void }
       def formula_options
         @formula_options = true
       end
@@ -367,6 +374,7 @@ module Homebrew
         end
       end
 
+      sig { void }
       def hide_from_man_page!
         @hide_from_man_page = true
       end
@@ -454,20 +462,24 @@ module Homebrew
       end
 
       def check_named_args(args)
-        min_exception = case @min_named_type
-        when :cask
-          Cask::CaskUnspecifiedError
-        when :formula
-          FormulaUnspecifiedError
-        when :formula_or_cask
-          FormulaOrCaskUnspecifiedError
-        when :keg
-          KegUnspecifiedError
-        else
-          MinNamedArgumentsError.new(@min_named_args)
+        exception = if @min_named_args && args.size < @min_named_args
+          case @min_named_type
+          when :cask
+            Cask::CaskUnspecifiedError
+          when :formula
+            FormulaUnspecifiedError
+          when :formula_or_cask
+            FormulaOrCaskUnspecifiedError
+          when :keg
+            KegUnspecifiedError
+          else
+            MinNamedArgumentsError.new(@min_named_args)
+          end
+        elsif @max_named_args && args.size > @max_named_args
+          MaxNamedArgumentsError.new(@max_named_args)
         end
-        raise min_exception if @min_named_args && args.size < @min_named_args
-        raise MaxNamedArgumentsError, @max_named_args if @max_named_args && args.size > @max_named_args
+
+        raise exception if exception
       end
 
       def process_option(*args)
@@ -535,6 +547,9 @@ module Homebrew
     end
 
     class MaxNamedArgumentsError < UsageError
+      extend T::Sig
+
+      sig { params(maximum: Integer).void }
       def initialize(maximum)
         super case maximum
         when 0
@@ -546,6 +561,9 @@ module Homebrew
     end
 
     class MinNamedArgumentsError < UsageError
+      extend T::Sig
+
+      sig { params(minimum: Integer).void }
       def initialize(minimum)
         super "This command requires at least #{minimum} named #{"argument".pluralize(minimum)}."
       end

Library/Homebrew/cmd/--cache.rb

@@ -6,10 +6,13 @@ require "cli/parser"
 require "cask/download"
 
 module Homebrew
+  extend T::Sig
+
   extend Fetch
 
   module_function
 
+  sig { returns(CLI::Parser) }
   def __cache_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/--caskroom.rb

@@ -1,9 +1,12 @@
-# typed: false
+# typed: strict
 # frozen_string_literal: true
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def __caskroom_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS
@@ -17,6 +20,7 @@ module Homebrew
     end
   end
 
+  sig { void }
   def __caskroom
     args = __caskroom_args.parse
 

Library/Homebrew/cmd/--env.rb

@@ -7,8 +7,11 @@ require "utils/shell"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def __env_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/--prefix.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def __prefix_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/--repository.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def __repository_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/--version.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def __version_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/analytics.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def analytics_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/cleanup.rb

@@ -5,8 +5,11 @@ require "cleanup"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def cleanup_args
     Homebrew::CLI::Parser.new do
       days = Homebrew::EnvConfig::ENVS[:HOMEBREW_CLEANUP_MAX_AGE_DAYS][:default]

Library/Homebrew/cmd/commands.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def commands_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/config.rb

@@ -5,8 +5,11 @@ require "system_config"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def config_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/deps.rb

@@ -8,10 +8,13 @@ require "cask/caskroom"
 require "dependencies_helpers"
 
 module Homebrew
+  extend T::Sig
+
   extend DependenciesHelpers
 
   module_function
 
+  sig { returns(CLI::Parser) }
   def deps_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/desc.rb

@@ -7,10 +7,13 @@ require "description_cache_store"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
   extend Search
 
+  sig { returns(CLI::Parser) }
   def desc_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/doctor.rb

@@ -6,8 +6,11 @@ require "cli/parser"
 require "cask/caskroom"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def doctor_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/fetch.rb

@@ -6,10 +6,13 @@ require "fetch"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   extend Fetch
 
   module_function
 
+  sig { returns(CLI::Parser) }
   def fetch_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/gist-logs.rb

@@ -9,10 +9,13 @@ require "socket"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   extend Install
 
   module_function
 
+  sig { returns(CLI::Parser) }
   def gist_logs_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/home.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def home_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/info.rb

@@ -13,12 +13,15 @@ require "utils/spdx"
 require "deprecate_disable"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
   VALID_DAYS = %w[30 90 365].freeze
   VALID_FORMULA_CATEGORIES = %w[install install-on-request build-error].freeze
   VALID_CATEGORIES = (VALID_FORMULA_CATEGORIES + %w[cask-install os-version]).freeze
 
+  sig { returns(CLI::Parser) }
   def info_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/install.rb

@@ -14,10 +14,13 @@ require "cli/parser"
 require "upgrade"
 
 module Homebrew
+  extend T::Sig
+
   extend Search
 
   module_function
 
+  sig { returns(CLI::Parser) }
   def install_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/leaves.rb

@@ -5,8 +5,11 @@ require "formula"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def leaves_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/link.rb

@@ -7,8 +7,11 @@ require "cli/parser"
 require "unlink"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def link_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/list.rb

@@ -7,8 +7,11 @@ require "cli/parser"
 require "cask/cmd"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def list_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/log.rb

@@ -5,8 +5,11 @@ require "formula"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def log_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/migrate.rb

@@ -5,8 +5,11 @@ require "migrator"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def migrate_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/missing.rb

@@ -7,8 +7,11 @@ require "diagnostic"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def missing_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/options.rb

@@ -7,8 +7,11 @@ require "cli/parser"
 require "commands"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def options_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/outdated.rb

@@ -8,8 +8,11 @@ require "cask/cmd"
 require "cask/caskroom"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def outdated_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/pin.rb

@@ -5,8 +5,11 @@ require "formula"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def pin_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/postinstall.rb

@@ -6,8 +6,11 @@ require "formula_installer"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def postinstall_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/readall.rb

@@ -5,8 +5,11 @@ require "readall"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def readall_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/reinstall.rb

@@ -14,8 +14,11 @@ require "cask/macos"
 require "upgrade"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def reinstall_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/search.rb

@@ -8,6 +8,8 @@ require "cli/parser"
 require "search"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
   extend Search
@@ -25,6 +27,7 @@ module Homebrew
     },
   }.freeze
 
+  sig { returns(CLI::Parser) }
   def search_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/switch.rb

@@ -6,8 +6,11 @@ require "keg"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def switch_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/tap-info.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def tap_info_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/tap.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def tap_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/uninstall.rb

@@ -11,8 +11,11 @@ require "cask/cask_loader"
 require "uninstall"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def uninstall_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/unlink.rb

@@ -6,8 +6,11 @@ require "cli/parser"
 require "unlink"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def unlink_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/unpin.rb

@@ -5,8 +5,11 @@ require "formula"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def unpin_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/untap.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def untap_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/update-report.rb

@@ -10,6 +10,8 @@ require "description_cache_store"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
   def update_preinstall_header(args:)
@@ -19,6 +21,7 @@ module Homebrew
     end
   end
 
+  sig { returns(CLI::Parser) }
   def update_report_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS
@@ -413,10 +416,13 @@ class Reporter
 end
 
 class ReporterHub
+  extend T::Sig
+
   extend Forwardable
 
   attr_reader :reporters
 
+  sig { void }
   def initialize
     @hash = {}
     @reporters = []

Library/Homebrew/cmd/upgrade.rb

@@ -10,8 +10,11 @@ require "cask/utils"
 require "cask/macos"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def upgrade_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/cmd/uses.rb

@@ -11,10 +11,13 @@ require "cask/caskroom"
 require "dependencies_helpers"
 
 module Homebrew
+  extend T::Sig
+
   extend DependenciesHelpers
 
   module_function
 
+  sig { returns(CLI::Parser) }
   def uses_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/config.rb

@@ -4,28 +4,36 @@
 raise "HOMEBREW_BREW_FILE was not exported! Please call bin/brew directly!" unless ENV["HOMEBREW_BREW_FILE"]
 
 # Path to `bin/brew` main executable in `HOMEBREW_PREFIX`
-HOMEBREW_BREW_FILE = Pathname.new(ENV["HOMEBREW_BREW_FILE"]).freeze
+HOMEBREW_BREW_FILE = Pathname(ENV["HOMEBREW_BREW_FILE"]).freeze
 
 class MissingEnvironmentVariables < RuntimeError; end
 
-def get_env_or_raise(env)
-  raise MissingEnvironmentVariables, "#{env} was not exported!" unless ENV[env]
+# Helper module for getting environment variables which must be set.
+#
+# @api private
+module EnvVar
+  extend T::Sig
 
-  ENV[env]
+  sig { params(env: String).returns(String) }
+  def self.[](env)
+    raise MissingEnvironmentVariables, "#{env} was not exported!" unless ENV[env]
+
+    ENV.fetch(env)
+  end
 end
 
 require "extend/git_repository"
 
 # Where we link under
-HOMEBREW_PREFIX = Pathname.new(get_env_or_raise("HOMEBREW_PREFIX")).freeze
+HOMEBREW_PREFIX = Pathname(EnvVar["HOMEBREW_PREFIX"]).freeze
 
 # Where `.git` is found
-HOMEBREW_REPOSITORY = Pathname.new(get_env_or_raise("HOMEBREW_REPOSITORY"))
-                              .extend(GitRepositoryExtension)
-                              .freeze
+HOMEBREW_REPOSITORY = Pathname(EnvVar["HOMEBREW_REPOSITORY"])
+                      .extend(GitRepositoryExtension)
+                      .freeze
 
 # Where we store most of Homebrew, taps, and various metadata
-HOMEBREW_LIBRARY = Pathname.new(get_env_or_raise("HOMEBREW_LIBRARY")).freeze
+HOMEBREW_LIBRARY = Pathname(EnvVar["HOMEBREW_LIBRARY"]).freeze
 
 # Where shim scripts for various build and SCM tools are stored
 HOMEBREW_SHIMS_PATH = (HOMEBREW_LIBRARY/"Homebrew/shims").freeze
@@ -43,19 +51,19 @@ HOMEBREW_PINNED_KEGS = (HOMEBREW_PREFIX/"var/homebrew/pinned").freeze
 HOMEBREW_LOCKS = (HOMEBREW_PREFIX/"var/homebrew/locks").freeze
 
 # Where we store built products
-HOMEBREW_CELLAR = Pathname.new(get_env_or_raise("HOMEBREW_CELLAR")).freeze
+HOMEBREW_CELLAR = Pathname(EnvVar["HOMEBREW_CELLAR"]).freeze
 
 # Where downloads (bottles, source tarballs, etc.) are cached
-HOMEBREW_CACHE = Pathname.new(get_env_or_raise("HOMEBREW_CACHE")).freeze
+HOMEBREW_CACHE = Pathname(EnvVar["HOMEBREW_CACHE"]).freeze
 
 # Where brews installed via URL are cached
 HOMEBREW_CACHE_FORMULA = (HOMEBREW_CACHE/"Formula").freeze
 
 # Where build, postinstall, and test logs of formulae are written to
-HOMEBREW_LOGS = Pathname.new(get_env_or_raise("HOMEBREW_LOGS")).expand_path.freeze
+HOMEBREW_LOGS = Pathname(EnvVar["HOMEBREW_LOGS"]).expand_path.freeze
 
 # Must use `/tmp` instead of `TMPDIR` because long paths break Unix domain sockets
-HOMEBREW_TEMP = Pathname.new(get_env_or_raise("HOMEBREW_TEMP")).yield_self do |tmp|
+HOMEBREW_TEMP = Pathname(EnvVar["HOMEBREW_TEMP"]).yield_self do |tmp|
   tmp.mkpath unless tmp.exist?
   tmp.realpath
 end.freeze

Library/Homebrew/cxxstdlib.rb

@@ -5,6 +5,8 @@ require "compilers"
 
 # Combination of C++ standard library and compiler.
 class CxxStdlib
+  extend T::Sig
+
   include CompilerConstants
 
   # Error for when a formula's dependency was built with a different C++ standard library.
@@ -72,6 +74,7 @@ class CxxStdlib
     type.to_s.gsub(/cxx$/, "c++")
   end
 
+  sig { returns(String) }
   def inspect
     "#<#{self.class.name}: #{compiler} #{type}>"
   end

Library/Homebrew/debrew.rb

@@ -41,10 +41,13 @@ module Debrew
 
   # Module for displaying a debugging menu.
   class Menu
+    extend T::Sig
+
     Entry = Struct.new(:name, :action)
 
     attr_accessor :prompt, :entries
 
+    sig { void }
     def initialize
       @entries = []
     end

Library/Homebrew/dependencies.rb

@@ -8,6 +8,8 @@ require "cask_dependent"
 #
 # @api private
 class Dependencies < SimpleDelegator
+  extend T::Sig
+
   def initialize(*args)
     super(args)
   end
@@ -34,6 +36,7 @@ class Dependencies < SimpleDelegator
     build + required + recommended
   end
 
+  sig { returns(String) }
   def inspect
     "#<#{self.class.name}: #{to_a}>"
   end
@@ -43,6 +46,8 @@ end
 #
 # @api private
 class Requirements < SimpleDelegator
+  extend T::Sig
+
   def initialize(*args)
     super(Set.new(args))
   end
@@ -59,6 +64,7 @@ class Requirements < SimpleDelegator
     self
   end
 
+  sig { returns(String) }
   def inspect
     "#<#{self.class.name}: {#{to_a.join(", ")}}>"
   end

Library/Homebrew/dependency.rb

@@ -7,6 +7,8 @@ require "dependable"
 #
 # @api private
 class Dependency
+  extend T::Sig
+
   extend Forwardable
   include Dependable
 
@@ -64,6 +66,7 @@ class Dependency
     env_proc&.call
   end
 
+  sig { returns(String) }
   def inspect
     "#<#{self.class.name}: #{name.inspect} #{tags.inspect}>"
   end
@@ -78,6 +81,8 @@ class Dependency
   end
 
   class << self
+    extend T::Sig
+
     # Expand the dependencies of each dependent recursively, optionally yielding
     # `[dependent, dep]` pairs to allow callers to apply arbitrary filters to
     # the list.
@@ -126,16 +131,19 @@ class Dependency
     end
 
     # Prune a dependency and its dependencies recursively.
+    sig { void }
     def prune
       throw(:action, :prune)
     end
 
     # Prune a single dependency but do not prune its dependencies.
+    sig { void }
     def skip
       throw(:action, :skip)
     end
 
     # Keep a dependency, but prune its dependencies.
+    sig { void }
     def keep_but_prune_recursive_deps
       throw(:action, :keep_but_prune_recursive_deps)
     end

Library/Homebrew/dependency_collector.rb

@@ -18,10 +18,13 @@ require "extend/cachable"
 # This class is used by `depends_on` in the formula DSL to turn dependency
 # specifications into the proper kinds of dependencies and requirements.
 class DependencyCollector
+  extend T::Sig
+
   extend Cachable
 
   attr_reader :deps, :requirements
 
+  sig { void }
   def initialize
     @deps = Dependencies.new
     @requirements = Requirements.new

Library/Homebrew/dev-cmd/audit.rb

@@ -18,8 +18,11 @@ require "cli/parser"
 require "json"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def audit_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/dev-cmd/bottle.rb

@@ -40,8 +40,11 @@ EOS
 MAXIMUM_STRING_MATCHES = 100
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def bottle_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/dev-cmd/bump-cask-pr.rb

@@ -6,8 +6,11 @@ require "cli/parser"
 require "utils/tar"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def bump_cask_pr_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/dev-cmd/bump-formula-pr.rb

@@ -7,8 +7,11 @@ require "utils/pypi"
 require "utils/tar"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def bump_formula_pr_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/dev-cmd/bump-revision.rb

@@ -5,8 +5,11 @@ require "formula"
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def bump_revision_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS

Library/Homebrew/dev-cmd/bump.rb

@@ -4,8 +4,11 @@
 require "cli/parser"
 
 module Homebrew
+  extend T::Sig
+
   module_function
 
+  sig { returns(CLI::Parser) }
   def bump_args
     Homebrew::CLI::Parser.new do
       usage_banner <<~EOS