style: don't concatenate in string interpolation

Library/Homebrew/dev-cmd/audit.rb

@@ -843,12 +843,6 @@ module Homebrew
         problem "Don't need to interpolate \"#{Regexp.last_match(2)}\" with #{Regexp.last_match(1)}"
       end
 
-      # Check for string concatenation; prefer interpolation
-      if line =~ /(#\{\w+\s*\+\s*['"][^}]+\})/
-        # TODO: check could be in RuboCop
-        problem "Try not to concatenate paths in string interpolation:\n   #{Regexp.last_match(1)}"
-      end
-
       # Prefer formula path shortcuts in Pathname+
       if line =~ %r{\(\s*(prefix\s*\+\s*(['"])(bin|include|libexec|lib|sbin|share|Frameworks)[/'"])}
         # TODO: check could be in RuboCop

Library/Homebrew/rubocops/text.rb

@@ -69,6 +69,15 @@ module RuboCop
             offending_node(m)
             problem "Use separate `make` calls"
           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*['"][^}]+\}/)
+
+              offending_node(interpolation_node)
+              problem "Do not concatenate paths in string interpolation"
+            end
+          end
         end
       end
     end

Library/Homebrew/test/rubocops/text_spec.rb

@@ -226,6 +226,17 @@ describe RuboCop::Cop::FormulaAudit::Text do
         end
       RUBY
     end
+
+    it "When concatenating in string interpolation" do
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          def install
+            ohai "foo \#{bar + "baz"}"
+                      ^^^^^^^^^^^^^^ Do not concatenate paths in string interpolation
+          end
+        end
+      RUBY
+    end
   end
 end