linkage_checker: typed: strict

[cho-m]

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Part of

• Use Sorbet typed: strict in all (non-package) files in Homebrew organisation #17297

[Copilot]

Pull request overview

This PR upgrades the linkage_checker.rb file to Sorbet's typed: strict mode as part of a broader effort tracked in issue #17297. The changes add comprehensive type annotations and make necessary code adjustments to satisfy strict type checking requirements while maintaining the existing functionality.

Key changes:

• Upgraded from typed: true to typed: strict with complete type signatures for all methods and attributes
• Added explicit type annotations using T.let for all instance variables with appropriate generic types
• Refactored display_items method to use array operations instead of string concatenation, improving readability and removing dead code

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[MikeMcQuaid]

Looks good so far! Most of the T.must though don't seem to be guaranteed to be the case?

[cho-m]

Most of the T.must though don't seem to be guaranteed to be the case?

Added commits to remove some of the T.must. They should have worked based on existing code, but cleaner to refactor in a way that Sorbet can track types.

The ones currently left are:

1. String <=> String - will always return an Integer but Sorbet can't narrow the return type. T.must is one option. Could alternatively do .to_i. Both should perform similarly as they will require a function call to essentially a no-op.
2. .split("/").last should not be nil for reasonable formula names. Would require something unexpected like an empty name which would be a bug elsewhere

   brew(main):001> "".split("/").last
   => nil
   brew(main):002> "/".split("/").last
   => nil

   An alternative is .split("/").fetch(-1) if we just want to avoid nil return type

   brew(main):003> "/".split("/").fetch(-1)
   (brew):3:in 'Array#fetch': index -1 outside of array bounds: 0...0 (IndexError)

   I don't think we want to do next if name.nil? as that should be unreachable code so we won't be able to hit it as part of test code coverage.