Make hvcats of heterogeneous combinations of dense matrices and vectors yield dense arrays (fixes JuliaLang#17686).

Author: Sacha0

base/array.jl

@@ -689,7 +689,6 @@ vcat{T}(A::Matrix{T}...) = typed_vcat(T, A...)
 hcat(A::Union{Matrix, Vector}...) = typed_hcat(promote_eltype(A...), A...)
 hcat{T}(A::Union{Matrix{T}, Vector{T}}...) = typed_hcat(T, A...)
 
-
 vcat(A::Union{Matrix, Vector}...) = typed_vcat(promote_eltype(A...), A...)
 vcat{T}(A::Union{Matrix{T}, Vector{T}}...) = typed_vcat(T, A...)
 
@@ -699,8 +698,11 @@ hvcat{T}(rows::Tuple{Vararg{Int}}, xs::Vector{T}...) = typed_hvcat(T, rows, xs..
 hvcat(rows::Tuple{Vararg{Int}}, xs::Matrix...) = typed_hvcat(promote_eltype(xs...), rows, xs...)
 hvcat{T}(rows::Tuple{Vararg{Int}}, xs::Matrix{T}...) = typed_hvcat(T, rows, xs...)
 
-cat(catdims, xs::Union{Matrix,Vector}...) = Base.cat_t(catdims, promote_eltype(xs...), xs...)
-cat{T}(catdims, xs::Union{Matrix{T},Vector{T}}...) = Base.cat_t(catdims, T, xs...)
+hvcat(rows::Tuple{Vararg{Int}}, xs::Union{Vector,Matrix}...) = typed_hvcat(promote_eltype(xs...), rows, xs...)
+hvcat{T}(rows::Tuple{Vararg{Int}}, xs::Union{Vector{T},Matrix{T}}...) = typed_hvcat(T, rows, xs...)
+
+cat(catdims, xs::Union{Vector,Matrix}...) = Base.cat_t(catdims, promote_eltype(xs...), xs...)
+cat{T}(catdims, xs::Union{Vector{T},Matrix{T}}...) = Base.cat_t(catdims, T, xs...)
 
 ## find ##
 

test/arrayops.jl

@@ -1703,3 +1703,25 @@ for op in (:.+, :.*, :.÷, :.%, :.<<, :.>>, :.-, :./, :.\, :.//, :.^)
 end
 
 end
+
+# Test that concatenations of dense matrices/vectors yield dense matrices/vectors
+let
+    N = 4
+    densevec = ones(N)
+    densemat = diagm(ones(N))
+    # Test that concatenations of homogeneous pairs of either dense matrices or dense vectors
+    # (i.e., Matrix-Matrix concatenations, and Vector-Vector concatenations) yield dense arrays
+    for densearray in (densevec, densemat)
+        @test isa(vcat(densevec, densevec), Array)
+        @test isa(hcat(densevec, densevec), Array)
+        @test isa(hvcat((2,), densevec, densevec), Array)
+        @test isa(cat((1,2), densevec, densevec), Array)
+    end
+    # Test that concatenations of heterogeneous Matrix-Vector pairs yield dense matrices
+    @test isa(hcat(densemat, densevec), Array)
+    @test isa(hcat(densevec, densemat), Array)
+    @test isa(hvcat((2,), densemat, densevec), Array)
+    @test isa(hvcat((2,), densevec, densemat), Array)
+    @test isa(cat((1,2), densemat, densevec), Array)
+    @test isa(cat((1,2), densevec, densemat), Array)
+end