cask_reason will suggest brew cask uninstall

Library/Homebrew/extend/ARGV.rb

@@ -42,6 +42,7 @@ module HomebrewArgvExtension
   def kegs
     require "keg"
     require "formula"
+    require "missing_formula"
     # TODO: use @instance variable to ||= cache when moving to CLI::Parser
     downcased_unique_named.map do |name|
       raise UsageError if name.empty?
@@ -50,7 +51,12 @@ module HomebrewArgvExtension
 
       dirs = rack.directory? ? rack.subdirs : []
 
-      raise NoSuchKegError, rack.basename if dirs.empty?
+      if dirs.empty?
+        if (reason = Homebrew::MissingFormula.suggest_command(name, "uninstall"))
+          $stderr.puts reason
+        end
+        raise NoSuchKegError, rack.basename
+      end
 
       linked_keg_ref = HOMEBREW_LINKED_KEGS/rack.basename
       opt_prefix = HOMEBREW_PREFIX/"opt/#{rack.basename}"

Library/Homebrew/extend/os/mac/missing_formula.rb

@@ -1,5 +1,10 @@
 # frozen_string_literal: true
 
+require "cask/cmd/abstract_command"
+require "cask/cmd/info"
+require "cask/cask_loader"
+require "cask/caskroom"
+
 module Homebrew
   module MissingFormula
     class << self
@@ -17,14 +22,32 @@ module Homebrew
       def cask_reason(name, silent: false, show_info: false)
         return if silent
 
-        cask = Cask::CaskLoader.load(name)
+        suggest_command(name, show_info ? "info" : "install")
-        reason = +"Found a cask named \"#{name}\" instead.\n"
-        if show_info
-          reason << Cask::Cmd::Info.get_info(cask)
-        else
-          reason << "Did you mean to type \"brew cask install #{name}\"?\n"
       end
-        reason.freeze
+
+      def suggest_command(name, command)
+        suggestion = <<~EOS
+          Found a cask named "#{name}" instead. Try
+            brew cask #{command} #{name}
+
+        EOS
+        case command
+        when "install"
+          Cask::CaskLoader.load(name)
+        when "uninstall"
+          cask = Cask::Caskroom.casks.find { |installed_cask| installed_cask.to_s == name }
+          raise Cask::CaskUnavailableError, name if cask.nil?
+        when "info"
+          cask = Cask::CaskLoader.load(name)
+          suggestion = <<~EOS
+            Found a cask named "#{name}" instead.
+
+            #{Cask::Cmd::Info.get_info(cask)}
+          EOS
+        else
+          return
+        end
+        suggestion
       rescue Cask::CaskUnavailableError
         nil
       end

Library/Homebrew/missing_formula.rb

@@ -1,9 +1,6 @@
 # frozen_string_literal: true
 
 require "formulary"
-require "cask/cmd/abstract_command"
-require "cask/cmd/info"
-require "cask/cask_loader"
 
 module Homebrew
   module MissingFormula
@@ -198,6 +195,8 @@ module Homebrew
 
       def cask_reason(name, silent: false, show_info: false); end
 
+      def suggest_command(name, command); end
+
       require "extend/os/missing_formula"
     end
   end

Library/Homebrew/test/missing_formula_spec.rb

@@ -100,14 +100,14 @@ describe Homebrew::MissingFormula do
       let(:show_info) { false }
 
       it { is_expected.to match(/Found a cask named "local-caffeine" instead./) }
-      it { is_expected.to match(/Did you mean to type "brew cask install local-caffeine"?/) }
+      it { is_expected.to match(/Try\n  brew cask install local-caffeine/) }
     end
 
     context "with a formula name that is a cask and show_info: true" do
       let(:formula) { "local-caffeine" }
       let(:show_info) { true }
 
-      it { is_expected.to match(/Found a cask named "local-caffeine" instead.\nlocal-caffeine: 1.2.3\n/) }
+      it { is_expected.to match(/Found a cask named "local-caffeine" instead.\n\nlocal-caffeine: 1.2.3\n/) }
     end
 
     context "with a formula name that is not a cask" do
@@ -117,4 +117,40 @@ describe Homebrew::MissingFormula do
       it { is_expected.to be_nil }
     end
   end
+
+  describe "::suggest_command", :cask do
+    subject { described_class.suggest_command(name, command) }
+
+    context "brew install" do
+      let(:name) { "local-caffeine" }
+      let(:command) { "install" }
+
+      it { is_expected.to match(/Found a cask named "local-caffeine" instead./) }
+      it { is_expected.to match(/Try\n  brew cask install local-caffeine/) }
+    end
+
+    context "brew uninstall" do
+      let(:name) { "local-caffeine" }
+      let(:command) { "uninstall" }
+
+      it { is_expected.to be_nil }
+
+      context "with described cask installed" do
+        before do
+          allow(Cask::Caskroom).to receive(:casks).and_return(["local-caffeine"])
+        end
+
+        it { is_expected.to match(/Found a cask named "local-caffeine" instead./) }
+        it { is_expected.to match(/Try\n  brew cask uninstall local-caffeine/) }
+      end
+    end
+
+    context "brew info" do
+      let(:name) { "local-caffeine" }
+      let(:command) { "info" }
+
+      it { is_expected.to match(/Found a cask named "local-caffeine" instead./) }
+      it { is_expected.to match(/local-caffeine: 1.2.3/) }
+    end
+  end
 end