Fix constructor for SVector{0} from Array (#608)

Fixes #520

Author: c42f

src/convert.jl

@@ -23,9 +23,12 @@ end
         dimension_mismatch_fail(SA, a)
     end
 
-    return SA(unroll_tuple(a, Length(SA)))
+    return _convert(SA, a, Length(SA))
 end
 
+@inline _convert(SA, a, ::Length{L}) where L = SA(unroll_tuple(a, Length(SA)))
+@inline _convert(SA, a, ::Length{0}) = similar_type(SA, eltype(a))(())
+
 length_val(a::T) where {T <: StaticArrayLike} = length_val(Size(T))
 length_val(a::Type{T}) where {T<:StaticArrayLike} = length_val(Size(T))
 

test/convert.jl

@@ -5,3 +5,9 @@ using StaticArrays, Test
     SizeM = Size(2,2)(M)
     @test typeof(SizeM)(SizeM).data === M
 end # testset
+
+@testset "Constructors of zero size arrays" begin
+    # Issue #520
+    @testinf SVector{0}(Int8[]) === SVector{0,Int8}()
+    @testinf SMatrix{0,0}(zeros(0,0)) === SMatrix{0,0,Float64}(())
+end