BREAKING: Remove covariance and LINQ use from Grouping, #1059

[paulirwin]

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Removes the covariance and LINQ use from Grouping, breaks GroupingSearch into subclasses

Fixes #1059

Description

See #1059 for rationale. This PR breaks GroupingSearch into three child classes (with some abstract base classes for common configuration properties) so that we can remove the covariance in the interfaces that were added to get this working in the original port. This keeps most of the interfaces but makes them non-generic (and thus, not covariant) for cases where you might need to have them in a common variable or collection. These were also needed for usage in the tests, where the test code randomly switches implementations that otherwise would not have common generic type parameters.

LINQ was removed, and IEnumerable<T> was changed to ICollection<T>/IList<T> to match the original Java code. This should improve performance a little bit by being able to reference Count etc. directly.

[paulirwin]

This old PR has been rebased against latest main. I intend to merge this this coming weekend if there is no further feedback.

[NightOwl888]

Not a full review, but there are some old comments that I had in a draft that I am posting so they aren't lost.

There was one issue I found on the first pass where it would have made sense to make a method into an extension method so it could expose the underlying type, but I was unable to locate it when I went back to find it again. I am hoping to locate it while this is still a PR.

This is going to take some dedicated time for a full review, though.

[Copilot]

Pull Request Overview

This PR removes covariance and LINQ usage from the Grouping module to align with the original Java code and improve performance. The main changes involve:

• Converting generic covariant interfaces to non-generic interfaces with explicit implementations
• Replacing IEnumerable<T> with ICollection<T>/IList<T> for better performance
• Adding casting adapter classes to bridge type conversions
• Breaking GroupingSearch into specialized subclasses

Reviewed Changes

Copilot reviewed 30 out of 31 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
Support/CastingSetAdapter.cs	New adapter class for type-safe casting between set types
Support/CastingListAdapter.cs	New adapter class for type-safe casting between list types
Support/CastingEnumeratorAdapter.cs	New adapter class for type-safe casting between enumerator types
Support/CastingCollectionAdapter.cs	New adapter class for type-safe casting between collection types
Tests	Updated test files to use concrete types instead of covariant interfaces
Grouping	Refactored interfaces to be non-generic with explicit implementations

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