fix for issue #641 (#662)

* fix for issue #641

* better disambiguation for hcat/vcat reductions

Author: mateuszbaran

src/mapreduce.jl

@@ -103,9 +103,9 @@ end
         @inbounds return $expr
     end
 end
-    
+
 @generated function _mapreduce(f, op, dims::Colon, nt::NamedTuple{(:init,)},
-                               ::Size{S}, a::StaticArray...) where {S}    
+                               ::Size{S}, a::StaticArray...) where {S}
     expr = :(nt.init)
     for i ∈ 1:prod(S)
         tmp = [:(a[$j][$i]) for j ∈ 1:length(a)]
@@ -138,7 +138,7 @@ end
                                ::Size{S}, a::StaticArray) where {S,D}
     N = length(S)
     Snew = ([n==D ? 1 : S[n] for n = 1:N]...,)
-    
+
     exprs = Array{Expr}(undef, Snew)
     itr = [1:n for n ∈ Snew]
     for i ∈ Base.product(itr...)
@@ -190,6 +190,17 @@ end
 
 @inline reduce(op, a::StaticArray; dims=:, kw...) = _reduce(op, a, dims, kw.data)
 
+# disambiguation
+reduce(::typeof(vcat), A::StaticArray{<:Tuple,<:AbstractVecOrMat}) =
+    Base._typed_vcat(mapreduce(eltype, promote_type, A), A)
+reduce(::typeof(vcat), A::StaticArray{<:Tuple,<:StaticVecOrMatLike}) =
+    _reduce(vcat, A, :, NamedTuple())
+
+reduce(::typeof(hcat), A::StaticArray{<:Tuple,<:AbstractVecOrMat}) =
+    Base._typed_hcat(mapreduce(eltype, promote_type, A), A)
+reduce(::typeof(hcat), A::StaticArray{<:Tuple,<:StaticVecOrMatLike}) =
+    _reduce(hcat, A, :, NamedTuple())
+
 @inline _reduce(op, a::StaticArray, dims, kw::NamedTuple=NamedTuple()) = _mapreduce(identity, op, dims, kw, Size(a), a)
 
 #######################

test/mapreduce.jl

@@ -162,4 +162,13 @@ using Statistics: mean
         v = SVector(SVector(3, 2, 1), SVector(5, 7, 9))
         @test @inferred(v + v) == SVector(SVector(6, 4, 2), SVector(10, 14, 18))
     end
+    @testset "hcat and vcat" begin
+        # issue #641
+        v = SVector([1,2], [3,4])
+        @test reduce(vcat, v) == [1,2,3,4]
+        @test reduce(hcat, v) == [1 3; 2 4]
+        v2 = SVector(SVector(1,2), SVector(3,4))
+        @test @inferred(reduce(vcat, v2)) === @SVector [1,2,3,4]
+        @test @inferred(reduce(hcat, v2)) === @SMatrix [1 3; 2 4]
+    end
 end

test/runtests.jl

@@ -3,7 +3,7 @@ using InteractiveUtils
 
 # Allow no new ambiguities (see #18), unless you fix some old ones first!
 if VERSION >= v"1.0.0"
-    @test length(detect_ambiguities(Base, LinearAlgebra, StaticArrays)) <= 7
+    @test length(detect_ambiguities(Base, LinearAlgebra, StaticArrays)) <= 5
 end
 
 # We generate a lot of matrices using rand(), but unit tests should be