rubocops/text: Prefer lib/"string" over lib+"string"

- I found a few occurrences of this pattern from
  https://github.com/orgs/Homebrew/projects/5?pane=issue&itemId=97021840,
  that is an automated style request for:
  `core: use / instead of + operator in e.g. (lib+"lv").install "lv.hlp"`.
- Upon adding tests I realised that there's also the `prefix + "bin"`
  case that's already handled differently, so let's combine the handling
  given it's the same `+` that's wrong.

Library/Homebrew/rubocops/text.rb

@@ -90,6 +90,30 @@ module RuboCop
             problem "Use separate `make` calls"
           end
 
+          find_every_method_call_by_name(body_node, :+).each do |plus_node|
+            next unless plus_node.receiver&.send_type?
+            next unless plus_node.first_argument&.str_type?
+
+            receiver_method = plus_node.receiver.method_name
+            path_arg = plus_node.first_argument.str_content
+
+            case receiver_method
+            when :prefix
+              next unless (match = path_arg.match(%r{^(bin|include|libexec|lib|sbin|share|Frameworks)(?:/| |$)}))
+
+              offending_node(plus_node)
+              problem "Use `#{match[1].downcase}` instead of `prefix + \"#{match[1]}\"`"
+            when :bin, :include, :libexec, :lib, :sbin, :share
+              next if path_arg.empty?
+
+              offending_node(plus_node)
+              good = "#{receiver_method}/\"#{path_arg}\""
+              problem "Use `#{good}` instead of `#{plus_node.source}`" do |corrector|
+                corrector.replace(plus_node.loc.expression, good)
+              end
+            end
+          end
+
           body_node.each_descendant(:dstr) do |dstr_node|
             dstr_node.each_descendant(:begin) do |interpolation_node|
               next unless interpolation_node.source.match?(/#\{\w+\s*\+\s*['"][^}]+\}/)
@@ -98,20 +122,8 @@ module RuboCop
               problem "Do not concatenate paths in string interpolation"
             end
           end
-
-          prefix_path(body_node) do |prefix_node, path|
-            next unless (match = path.match(%r{^(bin|include|libexec|lib|sbin|share|Frameworks)(?:/| |$)}))
-
-            offending_node(prefix_node)
-            problem "Use `#{match[1].downcase}` instead of `prefix + \"#{match[1]}\"`"
         end
       end
-
-        # Find: prefix + "foo"
-        def_node_search :prefix_path, <<~EOS
-          $(send (send nil? :prefix) :+ (str $_))
-        EOS
-      end
     end
 
     module FormulaAuditStrict

Library/Homebrew/test/rubocops/text_spec.rb

@@ -231,6 +231,19 @@ RSpec.describe RuboCop::Cop::FormulaAudit::Text do
       RUBY
     end
 
+    it 'reports offenses if eg `lib+"thing"` is present' do
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          def install
+            (lib+"foo").install
+             ^^^^^^^^^ FormulaAudit/Text: Use `lib/"foo"` instead of `lib+"foo"`
+            (bin+"foobar").install
+             ^^^^^^^^^^^^ FormulaAudit/Text: Use `bin/"foobar"` instead of `bin+"foobar"`
+          end
+        end
+      RUBY
+    end
+
     it 'reports an offense if `prefix + "bin"` is present' do
       expect_offense(<<~RUBY)
         class Foo < Formula