Remove generic AbstractArray fallbacks for position (#26)

Author: mtfishman

Project.toml

@@ -1,7 +1,7 @@
 name = "TypeParameterAccessors"
 uuid = "7e5a90cf-f82e-492e-a09b-e3e26432c138"
 authors = ["ITensor developers <[email protected]> and contributors"]
-version = "0.2.2"
+version = "0.3.0"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/TypeParameterAccessors.jl

@@ -18,7 +18,6 @@ include("type_parameters.jl")
 include("ndims.jl")
 include("base/abstractarray.jl")
 include("base/similartype.jl")
-include("base/array.jl")
 include("base/linearalgebra.jl")
 
 end

src/base/abstractarray.jl

@@ -1,3 +1,14 @@
+position(::Type{AbstractArray}, ::typeof(eltype)) = Position(1)
+position(::Type{AbstractArray}, ::typeof(ndims)) = Position(2)
+default_type_parameters(::Type{AbstractArray}) = (Float64, 1)
+
+position(::Type{<:Array}, ::typeof(eltype)) = Position(1)
+position(::Type{<:Array}, ::typeof(ndims)) = Position(2)
+default_type_parameters(::Type{<:Array}) = (Float64, 1)
+
+position(::Type{<:BitArray}, ::typeof(ndims)) = Position(1)
+default_type_parameters(::Type{<:BitArray}) = (1,)
+
 struct Self end
 position(a, ::Self) = Position(0)
 position(::Type{T}, ::Self) where {T} = Position(0)
@@ -70,18 +81,6 @@ end
   return set_type_parameters(type, eltype, param)
 end
 
-# These are generic fallback definitions. By convention,
-# this is very commonly true of `AbstractArray` subtypes
-# but it may not be correct, but it is very convenient
-# to define this to make more operations "just work"
-# on most AbstractArrays.
-# TODO: evaluate if this is actually the case, and weigh up the benefits of ease of use
-# against not having a helpful error thrown
-position(type::Type{<:AbstractArray}, ::typeof(eltype)) = Position(1)
-position(type::Type{<:AbstractArray}, ::typeof(ndims)) = Position(2)
-
-default_type_parameters(::Type{<:AbstractArray}) = (Float64, 1)
-
 for wrapper in [:PermutedDimsArray, :(Base.ReshapedArray), :SubArray]
   @eval begin
     position(type::Type{<:$wrapper}, ::typeof(eltype)) = Position(1)

src/base/array.jl

@@ -27,7 +27,11 @@ function position end
 position(object, name) = position(typeof(object), name)
 position(::Type, pos::Int) = Position(pos)
 position(::Type, pos::Position) = pos
-position(type::Type, pos) = throw(MethodError(position, (type, pos)))
+function position(type::Type, name)
+  base_type = unspecify_type_parameters(type)
+  base_type === type && error("`position` not defined for $type and $name.")
+  return position(base_type, name)
+end
 
 function positions(::Type{T}, pos::Tuple) where {T}
   return ntuple(length(pos)) do i