similar(::PermutedDimsArray)

Project.toml

@@ -1,6 +1,6 @@
 name = "Compat"
 uuid = "34da2185-b29b-5c13-b0c7-acf172513d20"
-version = "3.8.0"
+version = "3.9.0"
 
 [deps]
 Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"

README.md

@@ -44,6 +44,8 @@ Please check the list below for the specific syntax you need.
 
 ## Supported features
 
+* `similar(::PermutedDimsArray)` now uses the parent ([#35304]). (since Compat 3.9.0)
+
 * `@NamedTuple` macro for convenient `struct`-like syntax for declaring
 `NamedTuple` types via `key::Type` declarations ([#34548]). (since Compat 3.8.0)
 
@@ -137,3 +139,4 @@ Note that you should specify the correct minimum version for `Compat` in the
 [#34548]: https://github.com/JuliaLang/julia/pull/34548
 [#34652]: https://github.com/JuliaLang/julia/issues/34652
 [#34773]: https://github.com/JuliaLang/julia/issues/34773
+[#35304]: https://github.com/JuliaLang/julia/pull/35304

src/Compat.jl

@@ -329,6 +329,11 @@ if VERSION < v"1.4.0-DEV.513"
     export evalpoly
 end
 
+# https://github.com/JuliaLang/julia/pull/35304
+if VERSION < v"1.5.0-DEV.574"
+    Base.similar(A::PermutedDimsArray, T::Type, dims::Base.Dims) = similar(parent(A), T, dims)
+end
+
 # https://github.com/JuliaLang/julia/pull/34548
 if VERSION < v"1.5.0-DEV.314"
     macro NamedTuple(ex)

test/runtests.jl

@@ -298,6 +298,42 @@ end
     @test evalpoly(1+im, [2,]) == 2
 end
 
+# https://github.com/JuliaLang/julia/pull/35298
+begin
+    # A custom linear slow sparse-like array that relies upon Dict for its storage
+    struct TSlow{T,N} <: AbstractArray{T,N}
+        data::Dict{NTuple{N,Int}, T}
+        dims::NTuple{N,Int}
+    end
+    TSlow(::Type{T}, dims::Int...) where {T} = TSlow(T, dims)
+    TSlow(::Type{T}, dims::NTuple{N,Int}) where {T,N} = TSlow{T,N}(Dict{NTuple{N,Int}, T}(), dims)
+
+    TSlow{T,N}(X::TSlow{T,N})         where {T,N  } = X
+    TSlow(     X::AbstractArray{T,N}) where {T,N  } = TSlow{T,N}(X)
+    TSlow{T  }(X::AbstractArray{_,N}) where {T,N,_} = TSlow{T,N}(X)
+    TSlow{T,N}(X::AbstractArray     ) where {T,N  } = begin
+        A = TSlow(T, size(X))
+        for I in CartesianIndices(X)
+            A[Tuple(I)...] = X[Tuple(I)...]
+        end
+        A
+    end
+    Base.size(A::TSlow) = A.dims
+    Base.similar(A::TSlow, ::Type{T}, dims::Dims) where {T} = TSlow(T, dims)
+    Base.IndexStyle(::Type{A}) where {A<:TSlow} = IndexCartesian()
+    Base.getindex(A::TSlow{T,N}, i::Vararg{Int,N}) where {T,N} = get(A.data, i, zero(T))
+    Base.setindex!(A::TSlow{T,N}, v, i::Vararg{Int,N}) where {T,N} = (A.data[i] = v)
+end
+
+# https://github.com/JuliaLang/julia/pull/35304
+@testset "similar(PermutedDimsArray)" begin
+    x = PermutedDimsArray([1 2; 3 4], (2, 1))
+    @test similar(x, 3,3) isa Array
+    z = TSlow([1 2; 3 4])
+    x_slow = PermutedDimsArray(z, (2, 1))
+    @test similar(x_slow, 3,3) isa TSlow
+end
+
 # https://github.com/JuliaLang/julia/pull/34548
 @testset "@NamedTuple" begin
     @test (@NamedTuple {a::Int, b::String}) === NamedTuple{(:a, :b),Tuple{Int,String}} ===