use more type stable cat_t implementation (#92)

src/sparsevector.jl

@@ -1078,10 +1078,11 @@ const _SparseConcatGroup = Union{_DenseConcatGroup, _SparseConcatArrays, _Annota
 _makesparse(x::Number) = x
 _makesparse(x::AbstractArray) = SparseMatrixCSC(issparse(x) ? x : sparse(x))
 
-function Base._cat(dims, Xin::_SparseConcatGroup...)
+# `@constprop :aggressive` allows `dims` to be propagated as constant improving return type inference
+Base.@constprop :aggressive function Base._cat(dims, Xin::_SparseConcatGroup...)
  X = map(_makesparse, Xin)
  T = promote_eltype(Xin...)
- Base.cat_t(T, X...; dims=dims)
+ return Base._cat_t(dims, T, X...)
 end
 function hcat(Xin::_SparseConcatGroup...)
  X = map(_makesparse, Xin)

test/sparsevector.jl

@@ -561,6 +561,11 @@ end
  @test issparse(hvcat((2,), othervecormat, spvec))
  @test issparse(cat(spvec, othervecormat; dims=(1,2)))
  @test issparse(cat(othervecormat, spvec; dims=(1,2)))
+
+ # inferrability (https://github.com/JuliaSparse/SparseArrays.jl/pull/92)
+ cat_with_constdims(args...) = cat(args...; dims=(1,2))
+ @test issparse(@inferred cat_with_constdims(spvec, othervecormat))
+ @test issparse(@inferred cat_with_constdims(othervecormat, spvec))
  end
  # The preceding tests should cover multi-way combinations of those types, but for good
  # measure test a few multi-way combinations involving those types
@@ -572,6 +577,11 @@ end
  @test issparse(hvcat((5,), spvec, densemat, diagmat, densevec, spmat))
  @test issparse(cat(densemat, diagmat, spmat, densevec, spvec; dims=(1,2)))
  @test issparse(cat(spvec, diagmat, densevec, spmat, densemat; dims=(1,2)))
+
+ # inferrability (https://github.com/JuliaSparse/SparseArrays.jl/pull/92)
+ cat_with_constdims(args...) = cat(args...; dims=(1,2))
+ @test issparse(@inferred cat_with_constdims(densemat, diagmat, spmat, densevec, spvec))
+ @test issparse(@inferred cat_with_constdims(spvec, diagmat, densevec, spmat, densemat))
  end
  @testset "vertical concatenation of SparseVectors with different el- and ind-type (#22225)" begin
  spv6464 = SparseVector(0, Int64[], Int64[])