Ensure that StaticArrays rules are loaded correctly

Project.toml

@@ -6,6 +6,7 @@ version = "1.5.3"
 [deps]
 LaTeXStrings = "b964fa9f-0449-5b57-a5c2-d3ea65f4040f"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 PrecompileTools = "aea7be01-6a6a-4083-8856-8a6e6704d82a"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Requires = "ae029012-a4dd-5104-9daa-d747884805df"
@@ -23,8 +24,8 @@ Symbolics = "0c5d862f-8b57-4792-8d23-62f2024744c7"
 QuaternionicChainRulesCoreExt = "ChainRulesCore"
 QuaternionicFastDifferentiationExt = "FastDifferentiation"
 QuaternionicForwardDiffExt = "ForwardDiff"
-QuaternionicSymbolicsExt = "Symbolics"
 QuaternionicLatexifyExt = "Latexify"
+QuaternionicSymbolicsExt = "Symbolics"
 
 [compat]
 ChainRulesCore = "1"
@@ -34,6 +35,7 @@ GenericLinearAlgebra = "0.3.11"
 LaTeXStrings = "1"
 Latexify = "0.15, 0.16"
 LinearAlgebra = "1"
+Pkg = "1.11.0"
 PrecompileTools = "1.1.1"
 Random = "1"
 Requires = "1"

ext/QuaternionicChainRulesCoreExt.jl

@@ -1,5 +1,6 @@
 module QuaternionicChainRulesCoreExt
 
+using Pkg
 using Quaternionic
 import Quaternionic: _sincu, _cossu
 using StaticArrays
@@ -12,26 +13,31 @@ isdefined(Base, :get_extension) ?
 # It's likely that StaticArrays will have its own ChainRulesCore extension someday, so we
 # need to check if there is already a ProjectTo defined for SArray.  If so, we'll use that.
 # If not, we'll define one here.
-@info [repr(method) for method in methods(ProjectTo) if occursin("SArray", repr(method.sig))]
-@show any(method->occursin("SArray", repr(method.sig)), methods(ProjectTo))
-if !any(method->occursin("SArray", repr(method.sig)), methods(ProjectTo))
-    @info "Defining ProjectTo for SArray"
+staticarrays_info = Pkg.dependencies()[Base.UUID("90137ffa-7385-5640-81b9-e52037218182")]
+if staticarrays_info.version < v"1.8.1"
     # These are ripped from https://github.com/JuliaArrays/StaticArrays.jl/pull/1068
     function (project::ProjectTo{<:Tangent{<:Tuple}})(dx::SArray)
         dy = reshape(dx, axes(project.elements))  # allows for dx::OffsetArray
         dz = ntuple(i -> project.elements[i](dy[i]), length(project.elements))
         return ChainRulesCore.project_type(project)(dz...)
     end
     function ProjectTo(x::SArray{S,T}) where {S, T}
-        return ProjectTo{SArray}(; element=ChainRulesCore._eltype_projectto(T), axes=S)
-    end
-    function (project::ProjectTo{SArray})(dx::AbstractArray{S,M}) where {S,M}
-        return SArray{project.axes}(dx)
+        return ProjectTo{SArray}(;
+            element=ChainRulesCore._eltype_projectto(T),
+            axes=axes(x), size=StaticArrays.Size(x)
+        )
     end
-    function rrule(::Type{T}, x::Tuple) where {T<:SArray}
+    @inline _sarray_from_array(::Size{T}, dx::AbstractArray) where {T} = SArray{Tuple{T...}}(dx)
+    (project::ProjectTo{SArray})(dx::AbstractArray) = _sarray_from_array(project.size, dx)
+    function rrule(::Type{T}, x::Tuple) where {T <: SArray}
         project_x = ProjectTo(x)
-        Array_pullback(ȳ) = (NoTangent(), project_x(ȳ))
-        return T(x), Array_pullback
+        ∇Array(∂y) = (NoTangent(), project_x(∂y))
+        return T(x), ∇Array
+    end
+    function rrule(::Type{T}, xs::Number...) where {T <: SVector}
+        project_x = ProjectTo(xs)
+        ∇Array(∂y) = (NoTangent(), project_x(∂y)...)
+        return T(xs...), ∇Array
     end
 end