Rationalize the dispatch type aliases

[ViralBShah]

The Union aliases used for dispatch had grown to 36 across 7 files, with duplicates, near-duplicates that hid semantic differences, and no naming convention. This collects the cross-file ones into one section of abstractsparse.jl, drops the duplicates, reuses LinearAlgebra's aliases where they already exist, and gives the survivors one scheme. Solver scalar-type aliases stay with their solvers.

Before and after

Counting every const X = Union{...} in src:

	main	this PR
All Union aliases	44	32
Solver scalar / C-struct types (ITypes, VTypes, UMFITypes, ...)	10	9
Dispatch aliases	34	23

The 23 dispatch aliases are now: 9 in the shared section of abstractsparse.jl (AbstractSparseVecOrMat, SparseVecOrMat, SparseMatrixCSCOrView, SparseMatrixCSCOrColumnSubset, SparseVectorOrView, two <X>MaybeAdjOrTrans, SparseOrTri, LinAlgLeftQs), 8 local to linalg.jl (DenseMatrixUnion, DenseInputVector, MatrixWrappers, MatrixWrappersOrView, QuasiSparseMatrix, QuasiStridedMatrix, the two kron groups), 3 in CHOLMOD (StridedVecOrMatMaybeAdjOrTrans, SparseVectorOrMatrixCSC, FactorComponentRHS), UMFAdjOrTransLU in UMFPACK, and SparseVecOrMatStyle, SparseOrStructuredMatrix and the two concat groups. Placement follows one rule: used from more than one file goes in the shared section, used across a file goes at the top of that file, used by one section sits at the head of that section. A further three aliases (SparseTriangular, SparseMatrixCSCSymmHerm, CHOLMOD's RealHermSymComplexHermSSL) no longer spell out a Union because they are built on a LinearAlgebra alias.

Consolidation

• SparseVecOrMat / _SparseArraysCSC, StructuredMatrix / _SpecialArrays, _SparseVectorUnion / SparseVectorUnion, DenseViewWrappers / WrapperMatrixTypes, and SparseTriangular / AbstractTriangularSparse each collapse to one alias.
• "X or Adjoint/Transpose of X" is spelled <X>MaybeAdjOrTrans throughout (after LinearAlgebra's StridedMaybeAdjOrTransMat) and built from AdjOrTrans.
• "X or a view of X" is spelled <X>OrView / <X>OrColumnSubset. Alias names use the Sparse family name and accept the abstract tier of their base type; only the concrete CHOLMOD alias says otherwise in its name: SparseMatrixCSCUnion becomes SparseMatrixCSCOrView, SparseMatrixCSCUnion2 becomes SparseMatrixCSCOrColumnSubset, SparseVectorUnion becomes SparseVectorOrView, and AdjOrTransSparseVectorUnion becomes AdjOrTransSparseVectorOrView. The two-tier CSC split stays: the getcolptr-based kernels need a unit-range column view, the nzrange-based ones accept any column subset (Fix performance trap for sparse view multiplication #476).
• SorF is gone; SparseMatrixCSC and FixedSparseCSC each define their accessors.
• The seven one-off kron intermediates are folded into _SparseKronGroup / _DenseKronGroup.
• The inline spellings of the vec-or-mat union in the broadcast style rules, fkeep! and fill! use SparseVecOrMat; the two adjoint/transpose BroadcastStyle rules become one.
• CHOLMOD's concrete SparseVecOrMat is renamed SparseVectorOrMatrixCSC so it no longer shares a name with the top-level abstract alias. It stays concrete because Sparse(B) only accepts those two types.
• The remaining cryptic or misleading local names are renamed: UMFPACK's ATLU becomes UMFAdjOrTransLU, SPVM becomes SparseVecOrMatStyle, and WrapperMatrixTypes (which is MatrixWrappers plus SubArray) becomes MatrixWrappersOrView. The single-use SuiteSparseStruct is inlined.
• SparseOrStructuredMatrix is built on SparseMatrixCSCOrView instead of listing FixedSparseCSC, SparseMatrixCSC and SparseMatrixCSCView explicitly, so map over any AbstractSparseMatrixCSC subtype mixed with structured matrices takes the sparse path. The pre-existing all-sparse map/map! disambiguation methods widen from Vararg{SparseMatrixCSC} to Vararg{AbstractSparseMatrixCSC} to stay more specific than both competing methods.

Reusing LinearAlgebra's names

• BiTriSym was redefined identically; it is now imported from LinearAlgebra.
• HigherOrderFns.StructuredMatrix shadowed the larger LinearAlgebra.StructuredMatrix in the same file. Its set (Diagonal, Bidiagonal, Tridiagonal, SymTridiagonal) is exactly LinearAlgebra.BandedMatrix, which is used instead.
• CHOLMOD's RealHermSymComplexHermSSL is now RealHermSymComplexHerm{Tr,<:SparseMatrixCSC{<:Any,Ti}}; dispatch is unchanged.

Downstream-facing names

SparseMatrixCSCView, SparseColumnView and SparseVectorView are unchanged and used both internally and by downstream packages (LowRankOpt, IntervalMDP, Distances, and unregistered ones). SparseMatrixCSCUnion (Enzyme, SparseLinearAlgebra) and SparseVectorUnion (FillArrays, ArrayLayouts, Distances, FrankWolfe, SparseLinearAlgebra) are no longer used internally but are kept as aliases of the new names, with a note that they may be deprecated in a future release. AdjOrTransSparseVectorUnion has no external user on GitHub or JuliaHub and is dropped.

Behavior changes

• SparseTriangular now uses UpperOrLowerTriangular, so UnitUpperTriangular/UnitLowerTriangular wrappers of sparse matrices take the Gustavson product path like the non-unit ones (they are materialized via sparse(A) first; the temporary widens to Int indices when the added diagonal would not fit the parent's index type, and the result keeps the operands' index type). Tri × Tri products keep LinearAlgebra's result wrapper, including UnitUpper * UnitUpper staying unit.
• The sparse-vector fast path dispatches on SparseVectorOrView rather than AbstractSparseVector, so custom AbstractSparseVector types outside the kernel's supported set take the generic product. This also fixes UpperTriangular(S) * v for such vectors, a MethodError on main.
• nnz and indtype are extended to triangular wrappers of column-range views. On main, UpperTriangular(view(S, :, 1:n)) * S and 14 similar combinations throw MethodError; they now return correct sparse results.

A scratchpad probe of 1652 product, kron, dot, broadcast, conversion and solve combinations across sparse, view, wrapper and dense operands shows no result-type or correctness change for anything that worked on main, plus the 15 former MethodErrors now passing. Full suite and Aqua/ambiguity check pass locally, and CI is green on all platforms after rebasing onto main past #813, #817 and #819 (the all-sparse map! disambiguation now carries #813's _unaliasargs).

🤖 Generated with Claude Code

https://claude.ai/code/session_01MFPoSXGFJAGgJrHT98z2AY

[codecov]

Codecov Report

❌ Patch coverage is 87.90323% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.61%. Comparing base (6096fc0) to head (9dd7c61).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/solvers/cholmod.jl	69.23%	4 Missing ⚠️
src/higherorderfns.jl	81.25%	3 Missing ⚠️
src/linalg.jl	90.90%	3 Missing ⚠️
src/solvers/umfpack.jl	0.00%	3 Missing ⚠️
src/sparsematrix.jl	96.55%	1 Missing ⚠️
src/sparsevector.jl	96.29%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #816      +/-   ##
==========================================
+ Coverage   92.55%   92.61%   +0.05%     
==========================================
  Files          12       12              
  Lines        8501     8514      +13     
==========================================
+ Hits         7868     7885      +17     
+ Misses        633      629       -4     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[ViralBShah]

Found two P2 regressions in the expanded unit-triangular multiplication path, reproduced against base revision 6096fc0.

Validation: the linalg, higherorderfns, and fixed suites passed 9,033 tests, with one marked broken. Additional alias and custom-CSC mapping checks passed.

[Copilot]

🔵 Needs a closer look

The broad cross-file dispatch changes and new triangular multiplication paths warrant final human validation.

Pull request overview

Consolidates sparse dispatch aliases, removes duplicates, and reuses LinearAlgebra aliases while extending triangular sparse-view multiplication.

Changes:

• Centralizes shared dispatch aliases in abstractsparse.jl.
• Renames and simplifies local aliases across linear algebra and solver code.
• Adds coverage for triangular sparse matrices and column views.

File summaries

File	Description
src/abstractsparse.jl	Centralizes shared aliases.
src/SparseArrays.jl	Imports LinearAlgebra aliases.
src/sparsematrix.jl	Migrates CSC dispatch aliases.
src/sparsevector.jl	Migrates sparse-vector aliases.
src/sparseconvert.jl	Reuses shared wrapper aliases.
src/linalg.jl	Consolidates multiplication and kron dispatch.
src/higherorderfns.jl	Simplifies broadcast and map dispatch.
src/solvers/cholmod.jl	Renames CHOLMOD-local aliases.
src/solvers/umfpack.jl	Renames the UMFPACK wrapper alias.
test/linalg.jl	Tests triangular sparse-view multiplication.

Review details

• Files reviewed: 10/10 changed files
• Comments generated: 1
• Review effort level: Balanced

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.