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We still have a build break. Seems like this is not the only PR in the area path that @eiriktsarpalis merged with /ba-g without running any tests. The other one is #121998. I cannot do a revert of that one from github UI because "Sorry, this pull request couldn’t be reverted automatically. It may have already been reverted, or the content may have changed since it was merged." I assume because these PRs depend on each other.

So I've pushed out a git revert 2916d73755eb875a8803dfbb4d3a72a29cc6bd9b too.

🤖 Copilot Code Review — PR #126624

Holistic Assessment

Motivation: Justified. PRs #121999 (GroupJoin IGrouping<,> overloads) and #121998 (Join/LeftJoin/RightJoin tuple overloads) were merged during a CI outage and introduced a CS0411 type inference ambiguity build error. Reverting both to restore a known-good state on main is the correct response.

Approach: Two clean git revert commits that exactly invert the original additions. All public API surface, implementations, internal helper types, and tests are removed across System.Linq, System.Linq.Queryable, and System.Linq.AsyncEnumerable with no residual artifacts.

Summary: ✅ LGTM. Both reverts are complete and clean. All added surface from #121999 and #121998 is fully removed with no dangling references. The pre-existing overloads (with resultSelector parameters) remain intact and unchanged. The CS0411 build error cited in the PR description is addressed by the second commit's revert of the tuple-returning Join overloads.

Detailed Findings

✅ Revert Completeness — Both PRs fully reverted

Verified that both reverts remove all artifacts:

Commit 1 (796ef57c) — Reverts #121999 (GroupJoin IGrouping overloads):

• 3 ref assemblies updated: removed GroupJoin<TOuter,TInner,TKey> declarations
• 3 src files: removed public methods, private iterators, and internal helper classes (GroupJoinGrouping, AsyncGroupJoinGrouping)
• 3 test files: removed all tests for the reverted overloads

Commit 2 (51a2eb51) — Reverts #121998 (Join/LeftJoin/RightJoin tuple overloads):

• 3 ref assemblies updated: removed tuple-returning Join, LeftJoin, RightJoin declarations
• 6 src files (Join.cs, LeftJoin.cs, RightJoin.cs × 2 libraries): removed public methods and private iterators
• 6 test files: removed all TupleJoin*, TupleLeftJoin*, TupleRightJoin* tests

Confirmed zero remaining references to GroupJoinGrouping, AsyncGroupJoinGrouping, TupleJoin, TupleLeftJoin, or TupleRightJoin in the affected libraries.

✅ No Collateral Damage — Existing overloads untouched

The original resultSelector-based overloads for Join, GroupJoin, LeftJoin, and RightJoin are preserved identically in all three libraries (System.Linq: 5+3+5+5 public methods; AsyncEnumerable: 3+3+3+3 public methods). All existing tests for those overloads are retained. No csproj files were modified — file additions/removals were all within existing source files.

✅ Build Error Addressed — CS0411 resolved

The cited CS0411 error (AsyncEnumerable.Join<TOuter, TInner, TKey> type arguments cannot be inferred) was caused by the tuple-returning Join overloads creating an ambiguity with the resultSelector-based overloads when the compiler attempted type inference. The second commit reverting #121998 directly addresses this.

💡 PR Title and Description — Slightly outdated

The PR title says "Revert 'Add GroupJoin overload returning IGrouping'" and the description only mentions reverting #121999, but the PR now also reverts #121998 (Join/LeftJoin/RightJoin tuple overloads). Consider updating the title/description to reflect both reverts for clarity in the git history.

Generated by Code Review for issue #126624 · ◷

/ba-g wasm legs are broken everywhere, this is unlikely to make them worse since it's a clean revert. the build break is gone.