diff --git a/Library/Homebrew/brew.rb b/Library/Homebrew/brew.rb
index f31224ab25..d571f7e5c6 100644
--- a/Library/Homebrew/brew.rb
+++ b/Library/Homebrew/brew.rb
@@ -14,12 +14,13 @@ end
 
 require "pathname"
 HOMEBREW_LIBRARY_PATH = Pathname.new(__FILE__).realpath.parent
+
 require "English"
 unless $LOAD_PATH.include?(HOMEBREW_LIBRARY_PATH.to_s)
   $LOAD_PATH.unshift(HOMEBREW_LIBRARY_PATH.to_s)
 end
+
 require "global"
-require "tap"
 
 if ARGV == %w[--version] || ARGV == %w[-v]
   puts "Homebrew #{HOMEBREW_VERSION}"
diff --git a/Library/Homebrew/build_environment.rb b/Library/Homebrew/build_environment.rb
index 3c494428f0..da7d63cdf7 100644
--- a/Library/Homebrew/build_environment.rb
+++ b/Library/Homebrew/build_environment.rb
@@ -1,4 +1,3 @@
-require "set"
 
 class BuildEnvironment
   def initialize(*settings)
diff --git a/Library/Homebrew/cask/lib/hbc.rb b/Library/Homebrew/cask/lib/hbc.rb
index d865b31f2f..7547ea1e23 100644
--- a/Library/Homebrew/cask/lib/hbc.rb
+++ b/Library/Homebrew/cask/lib/hbc.rb
@@ -1,5 +1,4 @@
 require "hardware"
-require "utils"
 
 require "hbc/artifact"
 require "hbc/audit"
diff --git a/Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb b/Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb
index d299733d89..9776a42ae7 100644
--- a/Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb
+++ b/Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb
@@ -1,4 +1,3 @@
-require "pathname"
 require "timeout"
 
 require "hbc/artifact/abstract_artifact"
diff --git a/Library/Homebrew/cask/lib/hbc/container/bzip2.rb b/Library/Homebrew/cask/lib/hbc/container/bzip2.rb
index 9f2a59bb8a..efa95376a2 100644
--- a/Library/Homebrew/cask/lib/hbc/container/bzip2.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/bzip2.rb
@@ -1,5 +1,3 @@
-require "tmpdir"
-
 require "hbc/container/base"
 
 module Hbc
diff --git a/Library/Homebrew/cask/lib/hbc/container/cab.rb b/Library/Homebrew/cask/lib/hbc/container/cab.rb
index 327aece6ea..403abcc0fd 100644
--- a/Library/Homebrew/cask/lib/hbc/container/cab.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/cab.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/dmg.rb b/Library/Homebrew/cask/lib/hbc/container/dmg.rb
index c0e43f68a0..fcb9b5739d 100644
--- a/Library/Homebrew/cask/lib/hbc/container/dmg.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/dmg.rb
@@ -1,4 +1,3 @@
-require "set"
 require "tempfile"
 
 require "hbc/container/base"
diff --git a/Library/Homebrew/cask/lib/hbc/container/generic_unar.rb b/Library/Homebrew/cask/lib/hbc/container/generic_unar.rb
index 63ab917ea2..6a05edb8d0 100644
--- a/Library/Homebrew/cask/lib/hbc/container/generic_unar.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/generic_unar.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/gpg.rb b/Library/Homebrew/cask/lib/hbc/container/gpg.rb
index 09c75468ac..ae162565e8 100644
--- a/Library/Homebrew/cask/lib/hbc/container/gpg.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/gpg.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/gzip.rb b/Library/Homebrew/cask/lib/hbc/container/gzip.rb
index d3dd7b8fd0..4f91c3879c 100644
--- a/Library/Homebrew/cask/lib/hbc/container/gzip.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/gzip.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/lzma.rb b/Library/Homebrew/cask/lib/hbc/container/lzma.rb
index 1e165ba2a7..7d50199bc8 100644
--- a/Library/Homebrew/cask/lib/hbc/container/lzma.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/lzma.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/tar.rb b/Library/Homebrew/cask/lib/hbc/container/tar.rb
index eb646c816f..f5340174e4 100644
--- a/Library/Homebrew/cask/lib/hbc/container/tar.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/tar.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/xar.rb b/Library/Homebrew/cask/lib/hbc/container/xar.rb
index a0165ca57e..9121e726d8 100644
--- a/Library/Homebrew/cask/lib/hbc/container/xar.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/xar.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/xz.rb b/Library/Homebrew/cask/lib/hbc/container/xz.rb
index 4086ae1886..408e0917a5 100644
--- a/Library/Homebrew/cask/lib/hbc/container/xz.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/xz.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/dsl.rb b/Library/Homebrew/cask/lib/hbc/dsl.rb
index 9a88f1b624..9d229e2880 100644
--- a/Library/Homebrew/cask/lib/hbc/dsl.rb
+++ b/Library/Homebrew/cask/lib/hbc/dsl.rb
@@ -1,4 +1,3 @@
-require "set"
 require "locale"
 
 require "hbc/artifact"
diff --git a/Library/Homebrew/cask/lib/hbc/locations.rb b/Library/Homebrew/cask/lib/hbc/locations.rb
index 40ba2989f0..fea696e5b0 100644
--- a/Library/Homebrew/cask/lib/hbc/locations.rb
+++ b/Library/Homebrew/cask/lib/hbc/locations.rb
@@ -1,4 +1,3 @@
-require "tap"
 
 module Hbc
   module Locations
diff --git a/Library/Homebrew/cask/lib/hbc/macos.rb b/Library/Homebrew/cask/lib/hbc/macos.rb
index d47e04fb24..a9e9e0a243 100644
--- a/Library/Homebrew/cask/lib/hbc/macos.rb
+++ b/Library/Homebrew/cask/lib/hbc/macos.rb
@@ -1,4 +1,3 @@
-require "set"
 
 require "os/mac/version"
 
diff --git a/Library/Homebrew/caveats.rb b/Library/Homebrew/caveats.rb
index a289a12202..9fb788a46f 100644
--- a/Library/Homebrew/caveats.rb
+++ b/Library/Homebrew/caveats.rb
@@ -1,4 +1,3 @@
-require "forwardable"
 require "language/python"
 
 class Caveats
diff --git a/Library/Homebrew/cmd/--repository.rb b/Library/Homebrew/cmd/--repository.rb
index 006d4cd5d3..6f6f8d31ec 100644
--- a/Library/Homebrew/cmd/--repository.rb
+++ b/Library/Homebrew/cmd/--repository.rb
@@ -4,8 +4,6 @@
 #:  * `--repository` <user>`/`<repo>:
 #:    Display where tap <user>`/`<repo>'s directory is located.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/cleanup.rb b/Library/Homebrew/cmd/cleanup.rb
index 290b748de2..2fba06e20f 100644
--- a/Library/Homebrew/cmd/cleanup.rb
+++ b/Library/Homebrew/cmd/cleanup.rb
@@ -12,7 +12,6 @@
 #:    deleted. If you want to delete those too: `rm -rf $(brew --cache)`
 
 require "cleanup"
-require "utils"
 
 module Homebrew
   module_function
diff --git a/Library/Homebrew/cmd/install.rb b/Library/Homebrew/cmd/install.rb
index 392c299a06..8fce1d60a6 100644
--- a/Library/Homebrew/cmd/install.rb
+++ b/Library/Homebrew/cmd/install.rb
@@ -71,7 +71,6 @@ require "missing_formula"
 require "diagnostic"
 require "cmd/search"
 require "formula_installer"
-require "tap"
 require "hardware"
 require "development_tools"
 
diff --git a/Library/Homebrew/cmd/leaves.rb b/Library/Homebrew/cmd/leaves.rb
index 42fa18a28a..ec5238c2a1 100644
--- a/Library/Homebrew/cmd/leaves.rb
+++ b/Library/Homebrew/cmd/leaves.rb
@@ -3,7 +3,6 @@
 
 require "formula"
 require "tab"
-require "set"
 
 module Homebrew
   module_function
diff --git a/Library/Homebrew/cmd/search.rb b/Library/Homebrew/cmd/search.rb
index 4ba5247f12..25c602b124 100644
--- a/Library/Homebrew/cmd/search.rb
+++ b/Library/Homebrew/cmd/search.rb
@@ -15,8 +15,6 @@
 
 require "formula"
 require "missing_formula"
-require "utils"
-require "official_taps"
 require "descriptions"
 
 module Homebrew
diff --git a/Library/Homebrew/cmd/style.rb b/Library/Homebrew/cmd/style.rb
index 76d961a7fe..e41f10f97a 100644
--- a/Library/Homebrew/cmd/style.rb
+++ b/Library/Homebrew/cmd/style.rb
@@ -19,7 +19,6 @@
 #:
 #:    Exits with a non-zero status if any style violations are found.
 
-require "utils"
 require "json"
 require "open3"
 
diff --git a/Library/Homebrew/cmd/tap-info.rb b/Library/Homebrew/cmd/tap-info.rb
index 26daa1a8ae..b2d9ee5088 100644
--- a/Library/Homebrew/cmd/tap-info.rb
+++ b/Library/Homebrew/cmd/tap-info.rb
@@ -15,8 +15,6 @@
 #:    See the docs for examples of using the JSON output:
 #:    <https://docs.brew.sh/Querying-Brew>
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/tap-pin.rb b/Library/Homebrew/cmd/tap-pin.rb
index 41957f2652..505720f30d 100644
--- a/Library/Homebrew/cmd/tap-pin.rb
+++ b/Library/Homebrew/cmd/tap-pin.rb
@@ -2,8 +2,6 @@
 #:    Pin <tap>, prioritizing its formulae over core when formula names are supplied
 #:    by the user. See also `tap-unpin`.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/tap-unpin.rb b/Library/Homebrew/cmd/tap-unpin.rb
index 05bfc7c8b9..0c7c9ee020 100644
--- a/Library/Homebrew/cmd/tap-unpin.rb
+++ b/Library/Homebrew/cmd/tap-unpin.rb
@@ -1,8 +1,6 @@
 #:  * `tap-unpin` <tap>:
 #:    Unpin <tap> so its formulae are no longer prioritized. See also `tap-pin`.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index 847d355dcf..21d05d768e 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -28,8 +28,6 @@
 #:  * `tap` `--list-pinned`:
 #:    List all pinned taps.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/untap.rb b/Library/Homebrew/cmd/untap.rb
index 0d363b7b58..1b4bf109dd 100644
--- a/Library/Homebrew/cmd/untap.rb
+++ b/Library/Homebrew/cmd/untap.rb
@@ -1,8 +1,6 @@
 #:  * `untap` <tap>:
 #:    Remove a tapped repository.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/update-report.rb b/Library/Homebrew/cmd/update-report.rb
index d241d17b06..b2d5dfdbed 100644
--- a/Library/Homebrew/cmd/update-report.rb
+++ b/Library/Homebrew/cmd/update-report.rb
@@ -7,7 +7,6 @@ require "migrator"
 require "formulary"
 require "descriptions"
 require "cleanup"
-require "utils"
 
 module Homebrew
   module_function
diff --git a/Library/Homebrew/compat/gpg.rb b/Library/Homebrew/compat/gpg.rb
index e802d939cf..cdcbe2018d 100644
--- a/Library/Homebrew/compat/gpg.rb
+++ b/Library/Homebrew/compat/gpg.rb
@@ -1,4 +1,3 @@
-require "utils"
 
 module Gpg
   module_function
diff --git a/Library/Homebrew/compat/tap.rb b/Library/Homebrew/compat/tap.rb
index a1e3ce1727..9f4384da0e 100644
--- a/Library/Homebrew/compat/tap.rb
+++ b/Library/Homebrew/compat/tap.rb
@@ -1,4 +1,3 @@
-require "tap"
 
 class Tap
   def core_formula_repository?
diff --git a/Library/Homebrew/config.rb b/Library/Homebrew/config.rb
index 30b7bc6c9c..38d7c80438 100644
--- a/Library/Homebrew/config.rb
+++ b/Library/Homebrew/config.rb
@@ -2,8 +2,6 @@ unless ENV["HOMEBREW_BREW_FILE"]
   raise "HOMEBREW_BREW_FILE was not exported! Please call bin/brew directly!"
 end
 
-require "constants"
-
 # Path to `bin/brew` main executable in HOMEBREW_PREFIX
 HOMEBREW_BREW_FILE = Pathname.new(ENV["HOMEBREW_BREW_FILE"])
 
diff --git a/Library/Homebrew/dependency_collector.rb b/Library/Homebrew/dependency_collector.rb
index 74f42a6aaf..1a00c72012 100644
--- a/Library/Homebrew/dependency_collector.rb
+++ b/Library/Homebrew/dependency_collector.rb
@@ -2,7 +2,6 @@ require "dependency"
 require "dependencies"
 require "requirement"
 require "requirements"
-require "set"
 require "extend/cachable"
 
 ## A dependency is a formula that another formula needs to install.
diff --git a/Library/Homebrew/descriptions.rb b/Library/Homebrew/descriptions.rb
index bc19826731..4db47e77f1 100644
--- a/Library/Homebrew/descriptions.rb
+++ b/Library/Homebrew/descriptions.rb
@@ -1,4 +1,3 @@
-require "set"
 require "formula"
 require "formula_versions"
 
diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index 5eaffe2afa..99f9fffe77 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -39,11 +39,9 @@
 
 require "formula"
 require "formula_versions"
-require "utils"
 require "utils/curl"
 require "extend/ENV"
 require "formula_cellar_checks"
-require "official_taps"
 require "cmd/search"
 require "cmd/style"
 require "date"
diff --git a/Library/Homebrew/dev-cmd/bottle.rb b/Library/Homebrew/dev-cmd/bottle.rb
index b05277d054..ff01e24beb 100644
--- a/Library/Homebrew/dev-cmd/bottle.rb
+++ b/Library/Homebrew/dev-cmd/bottle.rb
@@ -37,7 +37,6 @@ require "formula_versions"
 require "cli_parser"
 require "utils/inreplace"
 require "erb"
-require "extend/pathname"
 
 BOTTLE_ERB = <<-EOS.freeze
   bottle do
diff --git a/Library/Homebrew/dev-cmd/pull.rb b/Library/Homebrew/dev-cmd/pull.rb
index c8006d7781..318d119aa4 100644
--- a/Library/Homebrew/dev-cmd/pull.rb
+++ b/Library/Homebrew/dev-cmd/pull.rb
@@ -50,12 +50,10 @@
 
 require "net/http"
 require "net/https"
-require "utils"
 require "json"
 require "cli_parser"
 require "formula"
 require "formulary"
-require "tap"
 require "version"
 require "pkg_version"
 
diff --git a/Library/Homebrew/dev-cmd/tap-new.rb b/Library/Homebrew/dev-cmd/tap-new.rb
index 31299d2b0b..b23cdef808 100644
--- a/Library/Homebrew/dev-cmd/tap-new.rb
+++ b/Library/Homebrew/dev-cmd/tap-new.rb
@@ -1,8 +1,6 @@
 #:  * `tap-new` <user>`/`<repo>:
 #:    Generate the template files for a new tap.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/dev-cmd/tests.rb b/Library/Homebrew/dev-cmd/tests.rb
index 57c00dafc7..50c9ca6d15 100644
--- a/Library/Homebrew/dev-cmd/tests.rb
+++ b/Library/Homebrew/dev-cmd/tests.rb
@@ -17,7 +17,6 @@
 
 require "cli_parser"
 require "fileutils"
-require "tap"
 
 module Homebrew
   module_function
diff --git a/Library/Homebrew/download_strategy.rb b/Library/Homebrew/download_strategy.rb
index b50ae317c7..6e637baa35 100644
--- a/Library/Homebrew/download_strategy.rb
+++ b/Library/Homebrew/download_strategy.rb
@@ -22,6 +22,7 @@ class AbstractDownloadStrategy
     @url = resource.url
     @version = resource.version
     @meta = resource.specs
+    @shutup = false
     extend Pourable if meta[:bottle]
   end
 
diff --git a/Library/Homebrew/extend/ENV/shared.rb b/Library/Homebrew/extend/ENV/shared.rb
index 5a6b779d0e..9ba3a244a4 100644
--- a/Library/Homebrew/extend/ENV/shared.rb
+++ b/Library/Homebrew/extend/ENV/shared.rb
@@ -1,7 +1,5 @@
-require "formula"
 require "compilers"
 require "development_tools"
-require "PATH"
 
 # Homebrew extends Ruby's `ENV` to make our code more readable.
 # Implemented in {SharedEnvExtension} and either {Superenv} or
diff --git a/Library/Homebrew/extend/fileutils.rb b/Library/Homebrew/extend/fileutils.rb
index 6286e48c01..ea2d51c01b 100644
--- a/Library/Homebrew/extend/fileutils.rb
+++ b/Library/Homebrew/extend/fileutils.rb
@@ -1,5 +1,4 @@
 require "fileutils"
-require "tmpdir"
 require "etc"
 
 # Homebrew extends Ruby's `FileUtils` to make our code more readable.
diff --git a/Library/Homebrew/extend/module.rb b/Library/Homebrew/extend/module.rb
index f4ea4de55a..b314543739 100644
--- a/Library/Homebrew/extend/module.rb
+++ b/Library/Homebrew/extend/module.rb
@@ -6,7 +6,9 @@ class Module
     attrs.each do |attr|
       module_eval <<-EOS, file, line
         def #{attr}(val=nil)
-          val.nil? ? @#{attr} : @#{attr} = val
+          @#{attr} ||= nil
+          return @#{attr} if val.nil?
+          @#{attr} = val
         end
       EOS
     end
diff --git a/Library/Homebrew/extend/optparse.rb b/Library/Homebrew/extend/optparse.rb
index 784d6d699d..801f7baddd 100644
--- a/Library/Homebrew/extend/optparse.rb
+++ b/Library/Homebrew/extend/optparse.rb
@@ -1,5 +1,4 @@
 require "optparse"
-require "pathname"
 
 OptionParser.accept Pathname do |path|
   Pathname(path).expand_path if path
diff --git a/Library/Homebrew/extend/os/bottles.rb b/Library/Homebrew/extend/os/bottles.rb
index 146b807a4a..6ee9a2146e 100644
--- a/Library/Homebrew/extend/os/bottles.rb
+++ b/Library/Homebrew/extend/os/bottles.rb
@@ -1,2 +1 @@
-require "utils/bottles"
 require "extend/os/mac/utils/bottles" if OS.mac?
diff --git a/Library/Homebrew/extend/os/dependency_collector.rb b/Library/Homebrew/extend/os/dependency_collector.rb
index 56fcad31d0..10131c916d 100644
--- a/Library/Homebrew/extend/os/dependency_collector.rb
+++ b/Library/Homebrew/extend/os/dependency_collector.rb
@@ -1,2 +1 @@
-require "dependency_collector"
 require "extend/os/mac/dependency_collector" if OS.mac?
diff --git a/Library/Homebrew/extend/os/development_tools.rb b/Library/Homebrew/extend/os/development_tools.rb
index 5bd5cb81a0..2d748074d1 100644
--- a/Library/Homebrew/extend/os/development_tools.rb
+++ b/Library/Homebrew/extend/os/development_tools.rb
@@ -1,2 +1 @@
-require "development_tools"
 require "extend/os/mac/development_tools" if OS.mac?
diff --git a/Library/Homebrew/extend/os/diagnostic.rb b/Library/Homebrew/extend/os/diagnostic.rb
index f8f53b1f4f..3e0d104fc4 100644
--- a/Library/Homebrew/extend/os/diagnostic.rb
+++ b/Library/Homebrew/extend/os/diagnostic.rb
@@ -1,2 +1 @@
-require "diagnostic"
 require "extend/os/mac/diagnostic" if OS.mac?
diff --git a/Library/Homebrew/extend/os/emoji.rb b/Library/Homebrew/extend/os/emoji.rb
index 8fd99e1d3e..59efced1d7 100644
--- a/Library/Homebrew/extend/os/emoji.rb
+++ b/Library/Homebrew/extend/os/emoji.rb
@@ -1,3 +1 @@
-require "os"
-require "emoji"
 require "extend/os/mac/emoji" if OS.mac?
diff --git a/Library/Homebrew/extend/os/extend/ENV/shared.rb b/Library/Homebrew/extend/os/extend/ENV/shared.rb
index e9574eb583..405c442912 100644
--- a/Library/Homebrew/extend/os/extend/ENV/shared.rb
+++ b/Library/Homebrew/extend/os/extend/ENV/shared.rb
@@ -1,2 +1 @@
-require "extend/ENV/shared"
 require "extend/os/mac/extend/ENV/shared" if OS.mac?
diff --git a/Library/Homebrew/extend/os/extend/ENV/std.rb b/Library/Homebrew/extend/os/extend/ENV/std.rb
index 18ede5b9ed..7d117c626e 100644
--- a/Library/Homebrew/extend/os/extend/ENV/std.rb
+++ b/Library/Homebrew/extend/os/extend/ENV/std.rb
@@ -1,4 +1,3 @@
-require "extend/ENV/std"
 if OS.mac?
   require "extend/os/mac/extend/ENV/std"
 elsif OS.linux?
diff --git a/Library/Homebrew/extend/os/extend/ENV/super.rb b/Library/Homebrew/extend/os/extend/ENV/super.rb
index 27c49eb849..a04f559f23 100644
--- a/Library/Homebrew/extend/os/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/os/extend/ENV/super.rb
@@ -1,2 +1 @@
-require "extend/ENV/super"
 require "extend/os/mac/extend/ENV/super" if OS.mac?
diff --git a/Library/Homebrew/extend/os/formula_cellar_checks.rb b/Library/Homebrew/extend/os/formula_cellar_checks.rb
index 66b5b80d3d..7198179563 100644
--- a/Library/Homebrew/extend/os/formula_cellar_checks.rb
+++ b/Library/Homebrew/extend/os/formula_cellar_checks.rb
@@ -1,2 +1 @@
-require "formula_cellar_checks"
 require "extend/os/mac/formula_cellar_checks" if OS.mac?
diff --git a/Library/Homebrew/extend/os/keg_relocate.rb b/Library/Homebrew/extend/os/keg_relocate.rb
index 25a74286a4..7c805a7ae1 100644
--- a/Library/Homebrew/extend/os/keg_relocate.rb
+++ b/Library/Homebrew/extend/os/keg_relocate.rb
@@ -1,2 +1 @@
-require "keg_relocate"
 require "extend/os/mac/keg_relocate" if OS.mac?
diff --git a/Library/Homebrew/extend/os/mac/caveats.rb b/Library/Homebrew/extend/os/mac/caveats.rb
index d912a83075..7ddfb5fb4d 100644
--- a/Library/Homebrew/extend/os/mac/caveats.rb
+++ b/Library/Homebrew/extend/os/mac/caveats.rb
@@ -1,4 +1,6 @@
 class Caveats
+  undef plist_caveats
+
   def plist_caveats
     s = []
     if f.plist || (keg&.plist_installed?)
diff --git a/Library/Homebrew/extend/os/mac/cleaner.rb b/Library/Homebrew/extend/os/mac/cleaner.rb
index 74f627b48e..69d82814d7 100644
--- a/Library/Homebrew/extend/os/mac/cleaner.rb
+++ b/Library/Homebrew/extend/os/mac/cleaner.rb
@@ -1,6 +1,8 @@
 class Cleaner
   private
 
+  undef executable_path?
+
   def executable_path?(path)
     path.mach_o_executable? || path.text_executable?
   end
diff --git a/Library/Homebrew/extend/os/mac/dependency_collector.rb b/Library/Homebrew/extend/os/mac/dependency_collector.rb
index a7e5d7ffc8..543c2494ec 100644
--- a/Library/Homebrew/extend/os/mac/dependency_collector.rb
+++ b/Library/Homebrew/extend/os/mac/dependency_collector.rb
@@ -1,6 +1,10 @@
 require "os/mac/ld64_dependency"
 
 class DependencyCollector
+  undef git_dep_if_needed, subversion_dep_if_needed, cvs_dep_if_needed,
+        xz_dep_if_needed, unzip_dep_if_needed, bzip2_dep_if_needed,
+        ld64_dep_if_needed
+
   def git_dep_if_needed(tags)
     return if MacOS.version >= :lion
     Dependency.new("git", tags)
@@ -18,7 +22,7 @@ class DependencyCollector
     Dependency.new("xz", tags)
   end
 
-  def zip_dep_if_needed(tags); end
+  def unzip_dep_if_needed(tags); end
 
   def bzip2_dep_if_needed(tags); end
 
diff --git a/Library/Homebrew/extend/os/mac/development_tools.rb b/Library/Homebrew/extend/os/mac/development_tools.rb
index d37e778ca5..ab2cfe90ea 100644
--- a/Library/Homebrew/extend/os/mac/development_tools.rb
+++ b/Library/Homebrew/extend/os/mac/development_tools.rb
@@ -3,10 +3,13 @@ require "os/mac/xcode"
 # @private
 class DevelopmentTools
   class << self
-    alias original_locate locate
+    alias generic_locate locate
+    undef installed?, default_compiler, curl_handles_most_https_certificates?,
+          subversion_handles_most_https_certificates?
+
     def locate(tool)
       (@locate ||= {}).fetch(tool) do |key|
-        @locate[key] = if (located_tool = original_locate(tool))
+        @locate[key] = if (located_tool = generic_locate(tool))
           located_tool
         elsif MacOS.version > :tiger
           path = Utils.popen_read("/usr/bin/xcrun", "-no-cache", "-find", tool, err: :close).chomp
@@ -22,6 +25,35 @@ class DevelopmentTools
       MacOS::Xcode.installed? || MacOS::CLT.installed?
     end
 
+    def default_compiler
+      case default_cc
+      # if GCC 4.2 is installed, e.g. via Tigerbrew, prefer it
+      # over the system's GCC 4.0
+      when /^gcc-4\.0/ then gcc_4_2_build_version ? :gcc_4_2 : :gcc_4_0
+      when /^gcc/ then :gcc_4_2
+      when "clang" then :clang
+      else
+        # guess :(
+        if MacOS::Xcode.version >= "4.3"
+          :clang
+        else
+          :gcc_4_2
+        end
+      end
+    end
+
+    def curl_handles_most_https_certificates?
+      # The system Curl is too old for some modern HTTPS certificates on
+      # older macOS versions.
+      ENV["HOMEBREW_SYSTEM_CURL_TOO_OLD"].nil?
+    end
+
+    def subversion_handles_most_https_certificates?
+      # The system Subversion is too old for some HTTPS certificates on
+      # older macOS versions.
+      MacOS.version >= :sierra
+    end
+
     def installation_instructions
       if MacOS.version >= "10.9"
         <<~EOS
@@ -64,34 +96,5 @@ class DevelopmentTools
         EOS
       end
     end
-
-    def default_compiler
-      case default_cc
-      # if GCC 4.2 is installed, e.g. via Tigerbrew, prefer it
-      # over the system's GCC 4.0
-      when /^gcc-4\.0/ then gcc_4_2_build_version ? :gcc_4_2 : :gcc_4_0
-      when /^gcc/ then :gcc_4_2
-      when "clang" then :clang
-      else
-        # guess :(
-        if MacOS::Xcode.version >= "4.3"
-          :clang
-        else
-          :gcc_4_2
-        end
-      end
-    end
-
-    def curl_handles_most_https_certificates?
-      # The system Curl is too old for some modern HTTPS certificates on
-      # older macOS versions.
-      ENV["HOMEBREW_SYSTEM_CURL_TOO_OLD"].nil?
-    end
-
-    def subversion_handles_most_https_certificates?
-      # The system Subversion is too old for some HTTPS certificates on
-      # older macOS versions.
-      MacOS.version >= :sierra
-    end
   end
 end
diff --git a/Library/Homebrew/extend/os/mac/diagnostic.rb b/Library/Homebrew/extend/os/mac/diagnostic.rb
index 78eeae904e..92fb3f315f 100644
--- a/Library/Homebrew/extend/os/mac/diagnostic.rb
+++ b/Library/Homebrew/extend/os/mac/diagnostic.rb
@@ -1,6 +1,9 @@
 module Homebrew
   module Diagnostic
     class Checks
+      undef development_tools_checks, fatal_development_tools_checks,
+            build_error_checks
+
       def development_tools_checks
         %w[
           check_for_unsupported_macos
diff --git a/Library/Homebrew/extend/os/mac/extend/ENV/std.rb b/Library/Homebrew/extend/os/mac/extend/ENV/std.rb
index 1a6d10f3b6..370bea2cf2 100644
--- a/Library/Homebrew/extend/os/mac/extend/ENV/std.rb
+++ b/Library/Homebrew/extend/os/mac/extend/ENV/std.rb
@@ -1,5 +1,39 @@
 module Stdenv
   # @private
+
+  undef homebrew_extra_pkg_config_paths, x11
+
+  def homebrew_extra_pkg_config_paths
+    ["#{HOMEBREW_LIBRARY}/Homebrew/os/mac/pkgconfig/#{MacOS.version}"]
+  end
+
+  def x11
+    # There are some config scripts here that should go in the PATH
+    append_path "PATH", MacOS::X11.bin.to_s
+
+    # Append these to PKG_CONFIG_LIBDIR so they are searched
+    # *after* our own pkgconfig directories, as we dupe some of the
+    # libs in XQuartz.
+    append_path "PKG_CONFIG_LIBDIR", "#{MacOS::X11.lib}/pkgconfig"
+    append_path "PKG_CONFIG_LIBDIR", "#{MacOS::X11.share}/pkgconfig"
+
+    append "LDFLAGS", "-L#{MacOS::X11.lib}"
+    append_path "CMAKE_PREFIX_PATH", MacOS::X11.prefix.to_s
+    append_path "CMAKE_INCLUDE_PATH", MacOS::X11.include.to_s
+    append_path "CMAKE_INCLUDE_PATH", "#{MacOS::X11.include}/freetype2"
+
+    append "CPPFLAGS", "-I#{MacOS::X11.include}"
+    append "CPPFLAGS", "-I#{MacOS::X11.include}/freetype2"
+
+    append_path "ACLOCAL_PATH", "#{MacOS::X11.share}/aclocal"
+
+    if MacOS::XQuartz.provided_by_apple? && !MacOS::CLT.installed?
+      append_path "CMAKE_PREFIX_PATH", "#{MacOS.sdk_path}/usr/X11"
+    end
+
+    append "CFLAGS", "-I#{MacOS::X11.include}" unless MacOS::CLT.installed?
+  end
+
   def setup_build_environment(formula = nil)
     generic_setup_build_environment formula
 
@@ -29,10 +63,6 @@ module Stdenv
     ld64 if Formula["ld64"].installed?
   end
 
-  def homebrew_extra_pkg_config_paths
-    ["#{HOMEBREW_LIBRARY}/Homebrew/os/mac/pkgconfig/#{MacOS.version}"]
-  end
-
   # Sets architecture-specific flags for every environment variable
   # given in the list `flags`.
   # @private
@@ -110,33 +140,6 @@ module Stdenv
     end
   end
 
-  def x11
-    # There are some config scripts here that should go in the PATH
-    append_path "PATH", MacOS::X11.bin.to_s
-
-    # Append these to PKG_CONFIG_LIBDIR so they are searched
-    # *after* our own pkgconfig directories, as we dupe some of the
-    # libs in XQuartz.
-    append_path "PKG_CONFIG_LIBDIR", "#{MacOS::X11.lib}/pkgconfig"
-    append_path "PKG_CONFIG_LIBDIR", "#{MacOS::X11.share}/pkgconfig"
-
-    append "LDFLAGS", "-L#{MacOS::X11.lib}"
-    append_path "CMAKE_PREFIX_PATH", MacOS::X11.prefix.to_s
-    append_path "CMAKE_INCLUDE_PATH", MacOS::X11.include.to_s
-    append_path "CMAKE_INCLUDE_PATH", "#{MacOS::X11.include}/freetype2"
-
-    append "CPPFLAGS", "-I#{MacOS::X11.include}"
-    append "CPPFLAGS", "-I#{MacOS::X11.include}/freetype2"
-
-    append_path "ACLOCAL_PATH", "#{MacOS::X11.share}/aclocal"
-
-    if MacOS::XQuartz.provided_by_apple? && !MacOS::CLT.installed?
-      append_path "CMAKE_PREFIX_PATH", "#{MacOS.sdk_path}/usr/X11"
-    end
-
-    append "CFLAGS", "-I#{MacOS::X11.include}" unless MacOS::CLT.installed?
-  end
-
   def no_weak_imports
     append "LDFLAGS", "-Wl,-no_weak_imports" if no_weak_imports_support?
   end
diff --git a/Library/Homebrew/extend/os/mac/extend/ENV/super.rb b/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
index f233002ea0..c60c9ab193 100644
--- a/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
@@ -1,16 +1,24 @@
 module Superenv
+  class << self
+    undef bin
+
+    # @private
+    def bin
+      return unless DevelopmentTools.installed?
+
+      (HOMEBREW_SHIMS_PATH/"super").realpath
+    end
+  end
+
   alias x11? x11
 
-  # @private
-  def self.bin
-    return unless DevelopmentTools.installed?
-
-    (HOMEBREW_SHIMS_PATH/"super").realpath
-  end
-
-  def effective_sysroot
-    MacOS.sdk_path.to_s if MacOS::Xcode.without_clt?
-  end
+  undef homebrew_extra_paths,
+        homebrew_extra_pkg_config_paths, homebrew_extra_aclocal_paths,
+        homebrew_extra_isystem_paths, homebrew_extra_library_paths,
+        homebrew_extra_cmake_include_paths,
+        homebrew_extra_cmake_library_paths,
+        homebrew_extra_cmake_frameworks_paths,
+        determine_cccfg, set_x11_env_if_installed
 
   def homebrew_extra_paths
     paths = []
@@ -86,6 +94,14 @@ module Superenv
     s
   end
 
+  def effective_sysroot
+    MacOS.sdk_path.to_s if MacOS::Xcode.without_clt?
+  end
+
+  def set_x11_env_if_installed
+    ENV.x11 = MacOS::X11.installed?
+  end
+
   # @private
   def setup_build_environment(formula = nil)
     generic_setup_build_environment(formula)
@@ -115,10 +131,6 @@ module Superenv
     self["HOMEBREW_PREFER_CLT_PROXIES"] = "1" if MacOS.version >= "10.9"
   end
 
-  def set_x11_env_if_installed
-    ENV.x11 = MacOS::X11.installed?
-  end
-
   def no_weak_imports
     append "HOMEBREW_CCCFG", "w" if no_weak_imports_support?
   end
diff --git a/Library/Homebrew/extend/os/mac/hardware/cpu.rb b/Library/Homebrew/extend/os/mac/hardware/cpu.rb
index cc41ae9112..14ee2fd9ae 100644
--- a/Library/Homebrew/extend/os/mac/hardware/cpu.rb
+++ b/Library/Homebrew/extend/os/mac/hardware/cpu.rb
@@ -1,6 +1,9 @@
 module Hardware
   class CPU
     class << self
+      undef optimization_flags, type, family, universal_archs, can_run?,
+            features, sse4?
+
       PPC_OPTIMIZATION_FLAGS = {
         g3: "-mcpu=750",
         g4: "-mcpu=7400",
@@ -8,6 +11,7 @@ module Hardware
         g5: "-mcpu=970",
         g5_64: "-mcpu=970 -arch ppc64",
       }.freeze
+
       def optimization_flags
         OPTIMIZATION_FLAGS.merge(PPC_OPTIMIZATION_FLAGS)
       end
@@ -71,10 +75,6 @@ module Hardware
         end
       end
 
-      def extmodel
-        sysctl_int("machdep.cpu.extmodel")
-      end
-
       # Returns an array that's been extended with ArchitectureListExtension,
       # which provides helpers like #as_arch_flags and #as_cmake_arch_flags.
       def universal_archs
@@ -113,6 +113,14 @@ module Hardware
         ).split(" ").map { |s| s.downcase.to_sym }
       end
 
+      def sse4?
+        sysctl_bool("hw.optional.sse4_1")
+      end
+
+      def extmodel
+        sysctl_int("machdep.cpu.extmodel")
+      end
+
       def aes?
         sysctl_bool("hw.optional.aes")
       end
@@ -137,10 +145,6 @@ module Hardware
         sysctl_bool("hw.optional.supplementalsse3")
       end
 
-      def sse4?
-        sysctl_bool("hw.optional.sse4_1")
-      end
-
       def sse4_2?
         sysctl_bool("hw.optional.sse4_2")
       end
diff --git a/Library/Homebrew/extend/os/mac/keg_relocate.rb b/Library/Homebrew/extend/os/mac/keg_relocate.rb
index 707710be61..f92134e5a4 100644
--- a/Library/Homebrew/extend/os/mac/keg_relocate.rb
+++ b/Library/Homebrew/extend/os/mac/keg_relocate.rb
@@ -1,24 +1,20 @@
 class Keg
-  def fix_dynamic_linkage
-    mach_o_files.each do |file|
-      file.ensure_writable do
-        change_dylib_id(dylib_id_for(file), file) if file.dylib?
+  class << self
+    undef file_linked_libraries
 
-        each_install_name_for(file) do |bad_name|
-          # Don't fix absolute paths unless they are rooted in the build directory
-          next if bad_name.start_with?("/") &&
-                  !bad_name.start_with?(HOMEBREW_TEMP.to_s) &&
-                  !bad_name.start_with?(HOMEBREW_TEMP.realpath.to_s)
-
-          new_name = fixed_name(file, bad_name)
-          change_install_name(bad_name, new_name, file) unless new_name == bad_name
-        end
+    def file_linked_libraries(file, string)
+      # Check dynamic library linkage. Importantly, do not perform for static
+      # libraries, which will falsely report "linkage" to themselves.
+      if file.mach_o_executable? || file.dylib? || file.mach_o_bundle?
+        file.dynamically_linked_libraries.select { |lib| lib.include? string }
+      else
+        []
       end
     end
-
-    generic_fix_dynamic_linkage
   end
 
+  undef relocate_dynamic_linkage, detect_cxx_stdlibs
+
   def relocate_dynamic_linkage(relocation)
     mach_o_files.each do |file|
       file.ensure_writable do
@@ -58,6 +54,26 @@ class Keg
     results.to_a
   end
 
+  def fix_dynamic_linkage
+    mach_o_files.each do |file|
+      file.ensure_writable do
+        change_dylib_id(dylib_id_for(file), file) if file.dylib?
+
+        each_install_name_for(file) do |bad_name|
+          # Don't fix absolute paths unless they are rooted in the build directory
+          next if bad_name.start_with?("/") &&
+                  !bad_name.start_with?(HOMEBREW_TEMP.to_s) &&
+                  !bad_name.start_with?(HOMEBREW_TEMP.realpath.to_s)
+
+          new_name = fixed_name(file, bad_name)
+          change_install_name(bad_name, new_name, file) unless new_name == bad_name
+        end
+      end
+    end
+
+    generic_fix_dynamic_linkage
+  end
+
   # If file is a dylib or bundle itself, look for the dylib named by
   # bad_name relative to the lib directory, so that we can skip the more
   # expensive recursive search if possible.
@@ -130,14 +146,4 @@ class Keg
     # it's wrong. -O is a BSD-grep-only option.
     "-lrO"
   end
-
-  def self.file_linked_libraries(file, string)
-    # Check dynamic library linkage. Importantly, do not perform for static
-    # libraries, which will falsely report "linkage" to themselves.
-    if file.mach_o_executable? || file.dylib? || file.mach_o_bundle?
-      file.dynamically_linked_libraries.select { |lib| lib.include? string }
-    else
-      []
-    end
-  end
 end
diff --git a/Library/Homebrew/extend/os/mac/requirements/java_requirement.rb b/Library/Homebrew/extend/os/mac/requirements/java_requirement.rb
index b8cf502a5e..6f0608fe7a 100644
--- a/Library/Homebrew/extend/os/mac/requirements/java_requirement.rb
+++ b/Library/Homebrew/extend/os/mac/requirements/java_requirement.rb
@@ -20,6 +20,8 @@ class JavaRequirement < Requirement
 
   private
 
+  undef possible_javas, oracle_java_os
+
   JAVA_CASK_MAP = {
     "1.8" => "caskroom/versions/java8",
     "10.0" => "java",
@@ -35,6 +37,10 @@ class JavaRequirement < Requirement
     javas
   end
 
+  def oracle_java_os
+    :darwin
+  end
+
   def java_home_cmd
     return nil unless File.executable?("/usr/libexec/java_home")
     args = %w[--failfast]
@@ -47,8 +53,4 @@ class JavaRequirement < Requirement
   def env_apple
     ENV.append_to_cflags "-I/System/Library/Frameworks/JavaVM.framework/Versions/Current/Headers/"
   end
-
-  def oracle_java_os
-    :darwin
-  end
 end
diff --git a/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb b/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb
index 0c319d1de3..6b1c5b13b4 100644
--- a/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb
+++ b/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb
@@ -4,15 +4,17 @@ class X11Requirement < Requirement
   cask "xquartz"
   download "https://xquartz.macosforge.org"
 
-  def min_version
-    MacOS::XQuartz.minimum_version
-  end
-
   satisfy build_env: false do
     next false unless MacOS::XQuartz.installed?
     min_version <= MacOS::XQuartz.version
   end
 
+  undef min_version, message
+
+  def min_version
+    MacOS::XQuartz.minimum_version
+  end
+
   def message
     "XQuartz #{min_version} (or newer) is required to install this formula. #{super}"
   end
diff --git a/Library/Homebrew/extend/os/mac/system_config.rb b/Library/Homebrew/extend/os/mac/system_config.rb
index 66a96bd659..20f04c0abd 100644
--- a/Library/Homebrew/extend/os/mac/system_config.rb
+++ b/Library/Homebrew/extend/os/mac/system_config.rb
@@ -1,24 +1,6 @@
 class SystemConfig
   class << self
-    def xcode
-      @xcode ||= if MacOS::Xcode.installed?
-        xcode = MacOS::Xcode.version.to_s
-        xcode += " => #{MacOS::Xcode.prefix}" unless MacOS::Xcode.default_prefix?
-        xcode
-      end
-    end
-
-    def clt
-      @clt ||= if MacOS::CLT.installed? && MacOS::Xcode.version >= "4.3"
-        MacOS::CLT.version
-      end
-    end
-
-    def xquartz
-      @xquartz ||= if MacOS::XQuartz.installed?
-        "#{MacOS::XQuartz.version} => #{describe_path(MacOS::XQuartz.prefix)}"
-      end
-    end
+    undef describe_java, describe_homebrew_ruby
 
     def describe_java
       # java_home doesn't exist on all macOSs; it might be missing on older versions.
@@ -43,6 +25,26 @@ class SystemConfig
       end
     end
 
+    def xcode
+      @xcode ||= if MacOS::Xcode.installed?
+        xcode = MacOS::Xcode.version.to_s
+        xcode += " => #{MacOS::Xcode.prefix}" unless MacOS::Xcode.default_prefix?
+        xcode
+      end
+    end
+
+    def clt
+      @clt ||= if MacOS::CLT.installed? && MacOS::Xcode.version >= "4.3"
+        MacOS::CLT.version
+      end
+    end
+
+    def xquartz
+      @xquartz ||= if MacOS::XQuartz.installed?
+        "#{MacOS::XQuartz.version} => #{describe_path(MacOS::XQuartz.prefix)}"
+      end
+    end
+
     def dump_verbose_config(f = $stdout)
       dump_generic_verbose_config(f)
       f.puts "macOS: #{MacOS.full_version}-#{kernel}"
diff --git a/Library/Homebrew/extend/os/mac/utils/bottles.rb b/Library/Homebrew/extend/os/mac/utils/bottles.rb
index 03980aab0c..80d6afe78a 100644
--- a/Library/Homebrew/extend/os/mac/utils/bottles.rb
+++ b/Library/Homebrew/extend/os/mac/utils/bottles.rb
@@ -1,6 +1,8 @@
 module Utils
   class Bottles
     class << self
+      undef tag
+
       def tag
         if MacOS.version >= :lion
           MacOS.cat
@@ -21,9 +23,10 @@ module Utils
     class Collector
       private
 
-      alias original_find_matching_tag find_matching_tag
+      alias generic_find_matching_tag find_matching_tag
+
       def find_matching_tag(tag)
-        original_find_matching_tag(tag) || find_altivec_tag(tag) || find_or_later_tag(tag)
+        generic_find_matching_tag(tag) || find_altivec_tag(tag) || find_or_later_tag(tag)
       end
 
       # This allows generic Altivec PPC bottles to be supported in some
diff --git a/Library/Homebrew/extend/os/missing_formula.rb b/Library/Homebrew/extend/os/missing_formula.rb
index 02c59f4e4c..c589925764 100644
--- a/Library/Homebrew/extend/os/missing_formula.rb
+++ b/Library/Homebrew/extend/os/missing_formula.rb
@@ -1,2 +1 @@
-require "missing_formula"
 require "extend/os/mac/missing_formula" if OS.mac?
diff --git a/Library/Homebrew/extend/os/requirements/java_requirement.rb b/Library/Homebrew/extend/os/requirements/java_requirement.rb
index b512ada476..673d53079b 100644
--- a/Library/Homebrew/extend/os/requirements/java_requirement.rb
+++ b/Library/Homebrew/extend/os/requirements/java_requirement.rb
@@ -1,5 +1,3 @@
-require "requirements/java_requirement"
-
 if OS.mac?
   require "extend/os/mac/requirements/java_requirement"
 elsif OS.linux?
diff --git a/Library/Homebrew/extend/os/requirements/osxfuse_requirement.rb b/Library/Homebrew/extend/os/requirements/osxfuse_requirement.rb
index 5f56d48c4a..ab491aa1e4 100644
--- a/Library/Homebrew/extend/os/requirements/osxfuse_requirement.rb
+++ b/Library/Homebrew/extend/os/requirements/osxfuse_requirement.rb
@@ -1,5 +1,3 @@
-require "requirements/osxfuse_requirement"
-
 if OS.mac?
   require "extend/os/mac/requirements/osxfuse_requirement"
 elsif OS.linux?
diff --git a/Library/Homebrew/extend/os/system_config.rb b/Library/Homebrew/extend/os/system_config.rb
index fec31f1fa6..b80eec5e8e 100644
--- a/Library/Homebrew/extend/os/system_config.rb
+++ b/Library/Homebrew/extend/os/system_config.rb
@@ -1,5 +1,3 @@
-require "system_config"
-
 if OS.mac?
   require "extend/os/mac/system_config"
 elsif OS.linux?
diff --git a/Library/Homebrew/extend/pathname.rb b/Library/Homebrew/extend/pathname.rb
index baf47b2764..159c90d198 100644
--- a/Library/Homebrew/extend/pathname.rb
+++ b/Library/Homebrew/extend/pathname.rb
@@ -1,7 +1,5 @@
-require "pathname"
 require "resource"
 require "metafiles"
-require "utils"
 
 module DiskUsageExtension
   def disk_usage
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 9078557890..157dad1fca 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -10,7 +10,6 @@ require "formulary"
 require "software_spec"
 require "install_renamed"
 require "pkg_version"
-require "tap"
 require "keg"
 require "migrator"
 require "extend/ENV"
@@ -173,7 +172,9 @@ class Formula
     @name = name
     @path = path
     @alias_path = alias_path
-    @alias_name = File.basename(alias_path) if alias_path
+    @alias_name = if alias_path
+      File.basename(alias_path)
+    end
     @revision = self.class.revision || 0
     @version_scheme = self.class.version_scheme || 0
 
@@ -203,6 +204,7 @@ class Formula
     @pin = FormulaPin.new(self)
     @follow_installed_alias = true
     @prefix_returns_versioned_prefix = false
+    @oldname_lock = nil
   end
 
   # @private
diff --git a/Library/Homebrew/formula_cellar_checks.rb b/Library/Homebrew/formula_cellar_checks.rb
index 471a5ea2fe..91a559dfad 100644
--- a/Library/Homebrew/formula_cellar_checks.rb
+++ b/Library/Homebrew/formula_cellar_checks.rb
@@ -154,6 +154,8 @@ module FormulaCellarChecks
   end
 
   def audit_installed
+    @new_formula ||= false
+
     problem_if_output(check_manpages)
     problem_if_output(check_infopages)
     problem_if_output(check_jars)
diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index 8c7efc978b..7ed473ee89 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -1,5 +1,4 @@
 require "cxxstdlib"
-require "exceptions"
 require "formula"
 require "keg"
 require "tab"
@@ -59,7 +58,8 @@ class FormulaInstaller
     @invalid_option_names = []
     @requirement_messages = []
     @poured_bottle = false
-    @pour_failed   = false
+    @pour_failed = false
+    @start_time = nil
   end
 
   def self.attempted
diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index 5f6ae0723b..508611ac80 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -1,5 +1,4 @@
 require "digest/md5"
-require "tap"
 require "extend/cachable"
 
 # The Formulary is responsible for creating instances of Formula.
diff --git a/Library/Homebrew/global.rb b/Library/Homebrew/global.rb
index 32b5377a0e..70707b247a 100644
--- a/Library/Homebrew/global.rb
+++ b/Library/Homebrew/global.rb
@@ -1,21 +1,9 @@
-require "forwardable"
-require "extend/module"
-require "extend/predicable"
-require "extend/fileutils"
-require "extend/pathname"
-require "extend/git_repository"
-require "extend/ARGV"
-require "PATH"
-require "extend/string"
-require "os"
-require "utils"
-require "exceptions"
-require "set"
-require "rbconfig"
-require "official_taps"
-require "pp"
+require "pathname"
 require "English"
 
+require "pp"
+require "extend/ARGV"
+
 ARGV.extend(HomebrewArgvExtension)
 
 HOMEBREW_PRODUCT = ENV["HOMEBREW_PRODUCT"]
@@ -23,9 +11,12 @@ HOMEBREW_VERSION = ENV["HOMEBREW_VERSION"]
 HOMEBREW_WWW = "https://brew.sh".freeze
 
 require "config"
+require "extend/git_repository"
 
 HOMEBREW_REPOSITORY.extend(GitRepositoryExtension)
 
+require "rbconfig"
+
 RUBY_PATH = Pathname.new(RbConfig.ruby)
 RUBY_BIN = RUBY_PATH.dirname
 
@@ -33,7 +24,7 @@ HOMEBREW_USER_AGENT_CURL = ENV["HOMEBREW_USER_AGENT_CURL"]
 HOMEBREW_USER_AGENT_RUBY = "#{ENV["HOMEBREW_USER_AGENT"]} ruby/#{RUBY_VERSION}-p#{RUBY_PATCHLEVEL}".freeze
 HOMEBREW_USER_AGENT_FAKE_SAFARI = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/602.4.8 (KHTML, like Gecko) Version/10.0.3 Safari/602.4.8".freeze
 
-require "tap_constants"
+require "extend/fileutils"
 
 module Homebrew
   extend FileUtils
@@ -42,6 +33,7 @@ module Homebrew
     attr_writer :failed
 
     def failed?
+      @failed ||= false
       @failed == true
     end
 
@@ -60,7 +52,8 @@ end
 HOMEBREW_PULL_API_REGEX = %r{https://api\.github\.com/repos/([\w-]+)/([\w-]+)?/pulls/(\d+)}
 HOMEBREW_PULL_OR_COMMIT_URL_REGEX = %r[https://github\.com/([\w-]+)/([\w-]+)?/(?:pull/(\d+)|commit/[0-9a-fA-F]{4,40})]
 
-require "compat" unless ARGV.include?("--no-compat") || ENV["HOMEBREW_NO_COMPAT"]
+require "forwardable"
+require "PATH"
 
 ENV["HOMEBREW_PATH"] ||= ENV["PATH"]
 ORIGINAL_PATHS = PATH.new(ENV["HOMEBREW_PATH"]).map do |p|
@@ -88,3 +81,24 @@ HOMEBREW_INTERNAL_COMMAND_ALIASES = {
   "environment" => "--env",
   "--config" => "config",
 }.freeze
+
+require "set"
+
+require "os"
+require "extend/pathname"
+
+require "extend/module"
+require "extend/predicable"
+require "extend/string"
+
+require "constants"
+require "exceptions"
+require "utils"
+
+require "official_taps"
+require "tap"
+require "tap_constants"
+
+if !ARGV.include?("--no-compat") && !ENV["HOMEBREW_NO_COMPAT"]
+  require "compat"
+end
diff --git a/Library/Homebrew/hardware.rb b/Library/Homebrew/hardware.rb
index 0559ae694c..b2a559d59c 100644
--- a/Library/Homebrew/hardware.rb
+++ b/Library/Homebrew/hardware.rb
@@ -1,5 +1,3 @@
-require "os"
-
 module Hardware
   class CPU
     INTEL_32BIT_ARCHS = [:i386].freeze
diff --git a/Library/Homebrew/keg.rb b/Library/Homebrew/keg.rb
index d40be299c1..cf8d1b177e 100644
--- a/Library/Homebrew/keg.rb
+++ b/Library/Homebrew/keg.rb
@@ -1,4 +1,3 @@
-require "extend/pathname"
 require "keg_relocate"
 require "lock_file"
 require "ostruct"
diff --git a/Library/Homebrew/language/python.rb b/Library/Homebrew/language/python.rb
index de373efda4..171d7e8244 100644
--- a/Library/Homebrew/language/python.rb
+++ b/Library/Homebrew/language/python.rb
@@ -1,4 +1,3 @@
-require "utils"
 require "language/python_virtualenv_constants"
 
 module Language
diff --git a/Library/Homebrew/linkage_checker.rb b/Library/Homebrew/linkage_checker.rb
index a33454a039..f77a6c4a6b 100644
--- a/Library/Homebrew/linkage_checker.rb
+++ b/Library/Homebrew/linkage_checker.rb
@@ -1,4 +1,3 @@
-require "set"
 require "keg"
 require "formula"
 
diff --git a/Library/Homebrew/metafiles.rb b/Library/Homebrew/metafiles.rb
index 96fa086f49..51d64ad8d0 100644
--- a/Library/Homebrew/metafiles.rb
+++ b/Library/Homebrew/metafiles.rb
@@ -1,4 +1,3 @@
-require "set"
 
 module Metafiles
   # https://github.com/github/markup#markups
diff --git a/Library/Homebrew/migrator.rb b/Library/Homebrew/migrator.rb
index 503f889852..9b295c1a43 100644
--- a/Library/Homebrew/migrator.rb
+++ b/Library/Homebrew/migrator.rb
@@ -1,4 +1,3 @@
-require "formula"
 require "lock_file"
 require "keg"
 require "tab"
diff --git a/Library/Homebrew/missing_formula.rb b/Library/Homebrew/missing_formula.rb
index 31dfa94efa..8a80e90d57 100644
--- a/Library/Homebrew/missing_formula.rb
+++ b/Library/Homebrew/missing_formula.rb
@@ -1,6 +1,4 @@
 require "formulary"
-require "tap"
-require "utils"
 
 module Homebrew
   module MissingFormula
diff --git a/Library/Homebrew/options.rb b/Library/Homebrew/options.rb
index 05dd643ffe..11f8df3a54 100644
--- a/Library/Homebrew/options.rb
+++ b/Library/Homebrew/options.rb
@@ -1,4 +1,3 @@
-require "set"
 
 class Option
   attr_reader :name, :description, :flag
diff --git a/Library/Homebrew/os.rb b/Library/Homebrew/os.rb
index cc6c865375..ed12ea734f 100644
--- a/Library/Homebrew/os.rb
+++ b/Library/Homebrew/os.rb
@@ -1,5 +1,3 @@
-require "rbconfig"
-
 module OS
   def self.mac?
     return false if ENV["HOMEBREW_TEST_GENERIC_OS"]
diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index ade801c42a..c299d2816a 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -1,5 +1,3 @@
-require "hardware"
-require "development_tools"
 require "os/mac/version"
 require "os/mac/xcode"
 require "os/mac/xquartz"
diff --git a/Library/Homebrew/os/mac/architecture_list.rb b/Library/Homebrew/os/mac/architecture_list.rb
index 6f498c51f6..6373aed44d 100644
--- a/Library/Homebrew/os/mac/architecture_list.rb
+++ b/Library/Homebrew/os/mac/architecture_list.rb
@@ -1,4 +1,4 @@
-require "extend/os/hardware"
+require "hardware"
 
 module ArchitectureListExtension
   # @private
diff --git a/Library/Homebrew/readall.rb b/Library/Homebrew/readall.rb
index 1b6ae016e0..249987b33b 100644
--- a/Library/Homebrew/readall.rb
+++ b/Library/Homebrew/readall.rb
@@ -1,5 +1,4 @@
 require "formula"
-require "tap"
 
 module Readall
   class << self
diff --git a/Library/Homebrew/software_spec.rb b/Library/Homebrew/software_spec.rb
index df7b86770c..9ef63adbaf 100644
--- a/Library/Homebrew/software_spec.rb
+++ b/Library/Homebrew/software_spec.rb
@@ -42,6 +42,7 @@ class SoftwareSpec
     @deprecated_options = []
     @build = BuildOptions.new(Options.create(@flags), options)
     @compiler_failures = []
+    @bottle_disable_reason = nil
   end
 
   def owner=(owner)
diff --git a/Library/Homebrew/system_config.rb b/Library/Homebrew/system_config.rb
index 1cbd774de6..f42572add0 100644
--- a/Library/Homebrew/system_config.rb
+++ b/Library/Homebrew/system_config.rb
@@ -1,7 +1,6 @@
 require "hardware"
 require "software_spec"
 require "rexml/document"
-require "tap"
 require "development_tools"
 
 class SystemConfig
@@ -116,6 +115,7 @@ class SystemConfig
         HOMEBREW_REPOSITORY: "/usr/local/Homebrew",
         HOMEBREW_CELLAR: "/usr/local/Cellar",
         HOMEBREW_CACHE: "#{ENV["HOME"]}/Library/Caches/Homebrew",
+        HOMEBREW_RUBY_WARNINGS: "-W0",
       }.freeze
       boring_keys = %w[
         HOMEBREW_BROWSER
@@ -131,7 +131,6 @@ class SystemConfig
         HOMEBREW_LIBRARY
         HOMEBREW_MACOS_VERSION
         HOMEBREW_RUBY_PATH
-        HOMEBREW_RUBY_WARNINGS
         HOMEBREW_SYSTEM
         HOMEBREW_OS_VERSION
         HOMEBREW_PATH
@@ -151,6 +150,9 @@ class SystemConfig
       if defaults_hash[:HOMEBREW_CACHE] != HOMEBREW_CACHE.to_s
         f.puts "HOMEBREW_CACHE: #{HOMEBREW_CACHE}"
       end
+      if defaults_hash[:HOMEBREW_RUBY_WARNINGS] != ENV["HOMEBREW_RUBY_WARNINGS"].to_s
+        f.puts "HOMEBREW_RUBY_WARNINGS: #{ENV["HOMEBREW_RUBY_WARNINGS"]}"
+      end
       unless ENV["HOMEBREW_ENV"]
         ENV.sort.each do |key, value|
           next unless key.start_with?("HOMEBREW_")
diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index e13b9af754..48288e0081 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -1,4 +1,3 @@
-require "extend/string"
 require "extend/cachable"
 require "readall"
 
@@ -78,6 +77,8 @@ class Tap
     @full_name = "#{@user}/homebrew-#{@repo}"
     @path = TAP_DIRECTORY/@full_name.downcase
     @path.extend(GitRepositoryExtension)
+    @alias_table = nil
+    @alias_reverse_table = nil
   end
 
   # clear internal cache
diff --git a/Library/Homebrew/test/cleanup_spec.rb b/Library/Homebrew/test/cleanup_spec.rb
index 9ec3a30479..40ab4280b7 100644
--- a/Library/Homebrew/test/cleanup_spec.rb
+++ b/Library/Homebrew/test/cleanup_spec.rb
@@ -1,7 +1,6 @@
 require "test/support/fixtures/testball"
 require "cleanup"
 require "fileutils"
-require "pathname"
 
 describe Homebrew::Cleanup do
   let(:ds_store) { Pathname.new("#{HOMEBREW_PREFIX}/Library/.DS_Store") }
diff --git a/Library/Homebrew/test/cmd/search_spec.rb b/Library/Homebrew/test/cmd/search_spec.rb
index c55a51e4fe..15c66cba31 100644
--- a/Library/Homebrew/test/cmd/search_spec.rb
+++ b/Library/Homebrew/test/cmd/search_spec.rb
@@ -1,7 +1,6 @@
 describe "brew search", :integration_test do
   before do
     setup_test_formula "testball"
-    setup_remote_tap "caskroom/cask"
   end
 
   it "lists all available Formulae when no argument is given" do
@@ -26,6 +25,8 @@ describe "brew search", :integration_test do
   end
 
   it "falls back to a GitHub tap search when no formula is found", :needs_network, retry: 3 do
+    setup_remote_tap "caskroom/cask"
+
     expect { brew "search", "caskroom/cask/firefox" }
       .to output(/firefox/).to_stdout
       .and output(/Searching/).to_stderr
diff --git a/Library/Homebrew/test/pathname_spec.rb b/Library/Homebrew/test/pathname_spec.rb
index ac568d27fb..090897f6a3 100644
--- a/Library/Homebrew/test/pathname_spec.rb
+++ b/Library/Homebrew/test/pathname_spec.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 require "extend/pathname"
 require "install_renamed"
 
diff --git a/Library/Homebrew/test/spec_helper.rb b/Library/Homebrew/test/spec_helper.rb
index cba530736a..8719c6e584 100644
--- a/Library/Homebrew/test/spec_helper.rb
+++ b/Library/Homebrew/test/spec_helper.rb
@@ -1,13 +1,3 @@
-require "find"
-require "pathname"
-require "rspec/its"
-require "rspec/wait"
-require "rspec/retry"
-require "rubocop"
-require "rubocop/rspec/support"
-require "set"
-require "support/no_seed_progress_formatter"
-
 if ENV["HOMEBREW_TESTS_COVERAGE"]
   require "simplecov"
 
@@ -17,12 +7,19 @@ if ENV["HOMEBREW_TESTS_COVERAGE"]
   end
 end
 
+require "rspec/its"
+require "rspec/wait"
+require "rspec/retry"
+require "rubocop"
+require "rubocop/rspec/support"
+require "find"
+
 $LOAD_PATH.unshift(File.expand_path("#{ENV["HOMEBREW_LIBRARY"]}/Homebrew"))
 $LOAD_PATH.unshift(File.expand_path("#{ENV["HOMEBREW_LIBRARY"]}/Homebrew/test/support/lib"))
 
 require "global"
-require "tap"
 
+require "test/support/no_seed_progress_formatter"
 require "test/support/helper/fixtures"
 require "test/support/helper/formula"
 require "test/support/helper/mktmpdir"
diff --git a/Library/Homebrew/test/support/lib/config.rb b/Library/Homebrew/test/support/lib/config.rb
index a59d80c995..7408b3e34a 100644
--- a/Library/Homebrew/test/support/lib/config.rb
+++ b/Library/Homebrew/test/support/lib/config.rb
@@ -2,9 +2,6 @@ unless ENV["HOMEBREW_BREW_FILE"]
   raise "HOMEBREW_BREW_FILE was not exported! Please call bin/brew directly!"
 end
 
-require "constants"
-
-require "tmpdir"
 require "pathname"
 
 HOMEBREW_BREW_FILE = Pathname.new(ENV["HOMEBREW_BREW_FILE"])
diff --git a/Library/Homebrew/test/utils/tty_spec.rb b/Library/Homebrew/test/utils/tty_spec.rb
index e4b61a61ca..4489b818a9 100644
--- a/Library/Homebrew/test/utils/tty_spec.rb
+++ b/Library/Homebrew/test/utils/tty_spec.rb
@@ -1,4 +1,3 @@
-require "utils"
 
 describe Tty do
   describe "::strip_ansi" do
diff --git a/Library/Homebrew/test/utils_spec.rb b/Library/Homebrew/test/utils_spec.rb
index 21fcc3249f..dbfd1c3859 100644
--- a/Library/Homebrew/test/utils_spec.rb
+++ b/Library/Homebrew/test/utils_spec.rb
@@ -1,4 +1,3 @@
-require "utils"
 
 describe "globally-scoped helper methods" do
   let(:dir) { mktmpdir }
diff --git a/Library/Homebrew/utils.rb b/Library/Homebrew/utils.rb
index dcc69ecb30..84eb8aa8cc 100644
--- a/Library/Homebrew/utils.rb
+++ b/Library/Homebrew/utils.rb
@@ -1,6 +1,4 @@
-require "pathname"
 require "emoji"
-require "exceptions"
 require "utils/analytics"
 require "utils/curl"
 require "utils/fork"
diff --git a/Library/Homebrew/utils/curl.rb b/Library/Homebrew/utils/curl.rb
index 7b2488ec72..673e7457ff 100644
--- a/Library/Homebrew/utils/curl.rb
+++ b/Library/Homebrew/utils/curl.rb
@@ -1,4 +1,3 @@
-require "pathname"
 require "open3"
 
 def curl_executable