make constructors throw when given negative dimension size (#28)

Pointed out by vtjnash.

Author: nsajko

src/FixedSizeArrays.jl

@@ -43,6 +43,9 @@ Base.isassigned(a::FixedSizeArray, i::Int) = isassigned(a.mem, i)
 checked_dims_impl(a::Int, ::Tuple{}) = a
 function checked_dims_impl(a::Int, t::Tuple{Int,Vararg{Int,N}}) where {N}
     b = first(t)
+    if (a < 0) || (b < 0)
+        throw(ArgumentError("array dimension size can't be negative"))
+    end
     (m, o) = Base.Checked.mul_with_overflow(a, b)
     o && throw(ArgumentError("array dimensions too great, can't represent length"))
     r = Base.tail(t)::NTuple{N,Int}

test/runtests.jl

@@ -16,10 +16,29 @@ end
     @testset "Constructors" begin
         @test FixedSizeArray{Float64,0}(undef) isa FixedSizeArray{Float64,0}
         @test FixedSizeArray{Float64,0}(undef, ()) isa FixedSizeArray{Float64,0}
-        @test_throws ArgumentError FixedSizeArray{Float64,1}(undef, typemin(Int))
+        @test_throws ArgumentError FixedSizeArray{Float64,1}(undef, -1)
+        @test_throws ArgumentError FixedSizeArray{Float64,1}(undef, (-1,))
+        @test_throws ArgumentError FixedSizeArray{Float64,2}(undef, -1, -1)
         @test_throws ArgumentError FixedSizeArray{Float64,2}(undef, typemax(Int), typemax(Int))
         @test_throws ArgumentError FixedSizeArray{Float64,3}(undef, typemax(Int), typemax(Int), 2)
         @test_throws ArgumentError FixedSizeArray{Float64,4}(undef, typemax(Int), typemax(Int), 2, 4)
+        @testset "negative dimension size" begin
+            for n ∈ 2:4
+                funs = (
+                    Returns(-1),
+                    (i -> (i == 1) ?  1 : -1),
+                    (i -> (i == 1) ? -1 :  1),
+                    (i -> (i == n) ?  1 : -1),
+                    (i -> (i == n) ? -1 :  1),
+                )
+                fun = f -> ntuple(f, n)
+                sizes = map(fun, funs)
+                for siz ∈ sizes
+                    @test_throws ArgumentError FixedSizeArray{Float64,n}(undef, siz)
+                    @test_throws ArgumentError FixedSizeArray{Float64,n}(undef, siz...)
+                end
+            end
+        end
     end
 
     @testset "safe computation of length from dimensions size" begin