Fix type regression

Library/Homebrew/test/utils/inreplace_spec.rb

@@ -7,7 +7,7 @@ describe Utils::Inreplace do
   let(:file) { Tempfile.new("test") }
 
   before do
-    file.write <<~EOS
+    File.binwrite(file, <<~EOS)
       a
       b
       c
@@ -52,4 +52,18 @@ describe Utils::Inreplace do
       end.to raise_error(Utils::Inreplace::Error)
     end
   end
+
+  describe "#gsub!" do
+    it "substitutes pathname within file" do
+      # For a specific instance of this, see https://github.com/Homebrew/homebrew-core/blob/a8b0b10/Formula/loki.rb#L48
+      described_class.inreplace(file.path) do |s|
+        s.gsub!(Pathname("b"), "f")
+      end
+      expect(File.binread(file)).to eq <<~EOS
+        a
+        f
+        c
+      EOS
+    end
+  end
 end

Library/Homebrew/utils/string_inreplace_extension.rb

@@ -31,10 +31,11 @@ class StringInreplaceExtension
   #
   # @api public
   sig {
-    params(before: T.any(Regexp, String), after: String, audit_result: T::Boolean)
+    params(before: T.any(Pathname, Regexp, String), after: String, audit_result: T::Boolean)
       .returns(T.nilable(String))
   }
   def gsub!(before, after, audit_result = true) # rubocop:disable Style/OptionalBooleanParameter
+    before = before.to_s if before.is_a?(Pathname)
     result = inreplace_string.gsub!(before, after)
     errors << "expected replacement of #{before.inspect} with #{after.inspect}" if audit_result && result.nil?
     result