Some vcat / hcat overloads for Number + StaticArray (#768)

These extra overloads should be helpful for users though it's not really
possible to fix this in generality until the dispatch mechanism in Base
is improved.

Co-authored-by: Mateusz Baran <mateuszbaran89@gmail.com>

src/abstractarray.jl

@@ -230,9 +230,15 @@ end
 
 #--------------------------------------------------
 # Concatenation
-@inline vcat(a::StaticVecOrMatLike) = a
+@inline vcat(a::StaticMatrixLike) = a
 @inline vcat(a::StaticVecOrMatLike, b::StaticVecOrMatLike) = _vcat(Size(a), Size(b), a, b)
 @inline vcat(a::StaticVecOrMatLike, b::StaticVecOrMatLike, c::StaticVecOrMatLike...) = vcat(vcat(a,b), vcat(c...))
+# A couple of hacky overloads to avoid some vcat surprises.
+# We can't really make this work a lot better in general without Base providing
+# a dispatch mechanism for output container type.
+@inline vcat(a::StaticVector) = a
+@inline vcat(a::StaticVector, bs::Number...) = vcat(a, SVector(bs))
+@inline vcat(a::Number, b::StaticVector) = vcat(similar_type(b, typeof(a), Size(1))((a,)), b)
 
 @generated function _vcat(::Size{Sa}, ::Size{Sb}, a::StaticVecOrMatLike, b::StaticVecOrMatLike) where {Sa, Sb}
     if Size(Sa)[2] != Size(Sb)[2]
@@ -261,6 +267,9 @@ end
 @inline hcat(a::StaticMatrixLike) = a
 @inline hcat(a::StaticVecOrMatLike, b::StaticVecOrMatLike) = _hcat(Size(a), Size(b), a, b)
 @inline hcat(a::StaticVecOrMatLike, b::StaticVecOrMatLike, c::StaticVecOrMatLike...) = hcat(hcat(a,b), hcat(c...))
+@inline hcat(a::StaticMatrix{1}) = a # disambiguation
+@inline hcat(a::StaticMatrix{1}, bs::Number...) = hcat(a, SMatrix{1,length(bs)}(bs))
+@inline hcat(a::Number, b::StaticMatrix{1}) = hcat(similar_type(b, typeof(a), Size(1))((a,)), b)
 
 @generated function _hcat(::Size{Sa}, ::Size{Sb}, a::StaticVecOrMatLike, b::StaticVecOrMatLike) where {Sa, Sb}
     if Sa[1] != Sb[1]

test/abstractarray.jl

@@ -260,4 +260,16 @@ end
     let A = Transpose(@SMatrix [1 2; 3 4]), B = Adjoint(@SMatrix [5 6; 7 8])
         @test @inferred(vcat(A, B)) === SMatrix{4, 2}([Matrix(A); Matrix(B)])
     end
+
+    # hcat/vcat + mixtures of Number and SVector / SMatrix
+    @test @inferred(vcat(SA[1,2,3], 4, 5, 6)) === SVector{6}((1,2,3,4,5,6))
+    @test @inferred(vcat(0, SA[1,2,3])) === SVector{4}((0,1,2,3))
+    @test @inferred(hcat(SMatrix{1,3}((1,2,3)), 4, 5, 6)) === SMatrix{1,6}((1,2,3,4,5,6))
+    @test @inferred(hcat(0, SMatrix{1,3}((1,2,3)))) === SMatrix{1,4}((0,1,2,3))
+    @test @inferred(vcat(MVector((1,2,3)), 4, 5, 6))::MVector == [1,2,3,4,5,6]
+
+    @test @inferred(vcat(SA[1,2,3])) === SA[1,2,3]
+    @test @inferred(vcat(SA[1 2 3])) === SA[1 2 3]
+    @test @inferred(hcat(SA[1,2,3])) === SMatrix{3,1}(1,2,3)
+    @test @inferred(hcat(SA[1 2 3])) === SA[1 2 3]
 end