Wrapping it up

Library/Homebrew/system_command.rb

@@ -167,7 +167,7 @@ class SystemCommand
       args:         T::Array[T.any(String, Integer, Float, Pathname, URI::Generic)],
       sudo:         T::Boolean,
       sudo_as_root: T::Boolean,
-      env:          T::Hash[String, T.nilable(String)],
+      env:          T::Hash[String, T.any(NilClass, String, T::Boolean)],
       input:        T.any(String, T::Array[String]),
       must_succeed: T::Boolean,
       print_stdout: T.any(T::Boolean, Symbol),
@@ -376,7 +376,7 @@ class SystemCommand
 
   sig {
     params(
-      env:        T::Hash[String, String],
+      env:        T::Hash[String, T.nilable(String)],
       executable: String,
       args:       String,
       options:    T.untyped,

Library/Homebrew/test/dev-cmd/bottle_spec.rb

@@ -440,7 +440,7 @@ RSpec.describe Homebrew::DevCmd::Bottle do
         old_spec = BottleSpecification.new
         old_spec.rebuild(1)
         new_hash = { "rebuild" => 2 }
-        expect(homebrew.merge_bottle_spec(["rebuild"], old_spec, new_hash)).to eq [
+        expect(homebrew.merge_bottle_spec([:rebuild], old_spec, new_hash)).to eq [
           ['rebuild: old: "1", new: "2"'],
           [],
         ]

Library/Homebrew/test/download_strategies/curl_spec.rb

@@ -191,7 +191,7 @@ RSpec.describe CurlDownloadStrategy do
               hash_including(args: array_including_cons("#{artifact_domain}/#{resource_path}")),
             )
             .at_least(:once)
-            .and_return(SystemCommand::Result.new(["curl"], [""], status, secrets: []))
+            .and_return(SystemCommand::Result.new(["curl"], [[:stdout, ""]], status, secrets: []))
 
           strategy.fetch
         end

Library/Homebrew/test/livecheck/strategy/header_match_spec.rb

@@ -110,7 +110,10 @@ RSpec.describe Homebrew::Livecheck::Strategy::HeaderMatch do
 
     it "errors on an invalid return type from a block" do
       expect { header_match.versions_from_headers(headers) { 123 } }
-        .to raise_error(TypeError, Homebrew::Livecheck::Strategy::INVALID_BLOCK_RETURN_VALUE_MSG)
+        .to raise_error(
+          TypeError,
+          /#{Homebrew::Livecheck::Strategy::INVALID_BLOCK_RETURN_VALUE_MSG}|Expected type T::Hash\[String, String\]/o,
+        )
     end
   end
 end