Fix length(::Type{<:NDIndex}) (#61)

see #55 (comment)

Author: Tokazama

Project.toml

@@ -1,7 +1,7 @@
 name = "Static"
 uuid = "aedffcd0-7271-4cad-89d0-dc628f76c6d3"
 authors = ["chriselrod", "ChrisRackauckas", "Tokazama"]
-version = "0.6.4"
+version = "0.6.5"
 
 [deps]
 IfElse = "615f187c-cbe4-4ef1-ba3b-2fcf58d6d173"

src/ndindex.jl

@@ -65,7 +65,7 @@ end
 
 # length
 Base.length(@nospecialize(x::NDIndex))::Int = length(Tuple(x))
-Base.length(@nospecialize(T::Type{<:NDIndex}))::Int = @inbounds(T.parameters[1])
+Base.length(::Type{<:NDIndex{N}}) where {N} = N
 
 # indexing
 @propagate_inbounds function Base.getindex(x::NDIndex{N,T}, i::Int)::Int where {N,T}

test/runtests.jl

@@ -338,6 +338,8 @@ using Test
         @test @inferred(Base.IteratorsMD.split(x, Val(2))) === (NDIndex(1, 2), NDIndex(3,))
         @test @inferred(length(x)) === 3
         @test @inferred(length(typeof(x))) === 3
+        NDIndex2{I<:Tuple{Vararg{Union{StaticInt,Int},2}}} = NDIndex{2, I}
+        @test length(NDIndex2) === 2
         @test @inferred(y[2]) === 2
         @test @inferred(y[static(2)]) === static(2)