fix linear method tests

src/dense/generic_dense.jl

@@ -621,21 +621,21 @@ function _ode_interpolant!(out, Θ, dt, y₀, y₁, k, cache, idxs, T::Type{Val{
     partial_hermite_interpolant!(out, Θ, dt, y₀, y₁, k, cache, idxs, T, differential_vars)
 end
 
-function partial_hermite_interpolant(Θ, dt, y₀::AbstractArray, y₁::AbstractArray, k, cache, idxs::AbstractVector{Int}, T::Type{Val{TI}}, differential_vars) where {TI}
+function partial_hermite_interpolant(Θ, dt, y₀::AbstractArray, y₁::AbstractArray, k, cache, idxs::AbstractArray{Int}, T::Type{Val{TI}}, differential_vars) where {TI}
     sel = differential_vars[idxs]
-    diffidxs = idxs[sel]
-    linidxs = idxs[.!sel]
-    diff = hermite_interpolant(Θ, dt, y₀, y₁, k, Val{cache isa OrdinaryDiffEqMutableCache}, diffidxs, T)
-    lin = linear_interpolant(Θ, dt, y₀, y₁, linidxs, T)
     res = similar(y₀, eltype(y₀), size(sel))
-    res[sel] = diff
-    res[.!sel] = lin
+    res[sel] = hermite_interpolant(Θ, dt, y₀, y₁, k, Val{cache isa OrdinaryDiffEqMutableCache}, idxs[sel], T)
+    res[.!sel] = linear_interpolant(Θ, dt, y₀, y₁, idxs[.!sel], T)
     res
 end
 
 function partial_hermite_interpolant(Θ, dt, y₀::AT, y₁::AT, k, cache, idxs::Nothing, T::Type{Val{TI}}, differential_vars) where {TI, AT <: AbstractArray}
     if ArrayInterface.fast_scalar_indexing(AT)
-        partial_hermite_interpolant(Θ, dt, y₀, y₁, k, cache, eachindex(IndexLinear(), y₀), T, differential_vars)
+        sel = vec(differential_vars)
+        res = similar(y₀)
+        res[differential_vars] = hermite_interpolant(Θ, dt, y₀, y₁, k, Val{cache isa OrdinaryDiffEqMutableCache}, eachindex(y₀)[sel], T)
+        res[.!differential_vars] = linear_interpolant(Θ, dt, y₀, y₁, eachindex(y₀)[.!sel], T)
+        res
     else
         h = hermite_interpolant(Θ, dt, y₀, y₁, k, Val{cache isa OrdinaryDiffEqMutableCache}, idxs, T)
         l = linear_interpolant(Θ, dt, y₀, y₁, idxs, T)
@@ -665,18 +665,16 @@ function partial_hermite_interpolant(Θ, dt, y₀, y₁, k, cache, idxs, T::Type
     hermite_interpolant(Θ, dt, y₀, y₁, k, Val{cache isa OrdinaryDiffEqMutableCache}, idxs, T)
 end
 
-function partial_hermite_interpolant!(out::AbstractArray, Θ, dt, y₀::AbstractArray, y₁::AbstractArray, k, cache, idxs::AbstractVector{Int}, T::Type{Val{TI}}, differential_vars) where {TI}
+function partial_hermite_interpolant!(out::AbstractArray, Θ, dt, y₀::AbstractArray, y₁::AbstractArray, k, cache, idxs::AbstractArray{Int}, T::Type{Val{TI}}, differential_vars) where {TI}
     sel = differential_vars[idxs]
-    diffidxs = idxs[sel]
-    linidxs = idxs[.!sel]
-    hermite_interpolant!(@view(out[sel]), Θ, dt, y₀, y₁, k, diffidxs, T)
-    linear_interpolant!(@view(out[.!sel]), Θ, dt, y₀, y₁, linidxs, T)
+    hermite_interpolant!(@view(out[sel]), Θ, dt, y₀, y₁, k, idxs[sel], T)
+    linear_interpolant!(@view(out[.!sel]), Θ, dt, y₀, y₁, idxs[.!sel], T)
     out
 end
 
-function partial_hermite_interpolant!(out::AbstractArray, Θ, dt, y₀::AT, y₁::AT, k, cache, idxs::Nothing, T::Type{Val{TI}}, differential_vars) where {TI, AT <: AbstractArray}
+function partial_hermite_interpolant!(out::AT, Θ, dt, y₀::AT, y₁::AT, k, cache, idxs::Nothing, T::Type{Val{TI}}, differential_vars) where {TI, AT <: AbstractArray}
     if ArrayInterface.fast_scalar_indexing(AT)
-        partial_hermite_interpolant!(out, Θ, dt, y₀, y₁, k, cache, eachindex(IndexLinear(), y₀), T, differential_vars)
+        partial_hermite_interpolant!(out, Θ, dt, y₀, y₁, k, cache, eachindex(y₀), T, differential_vars)
     else
         h = hermite_interpolant(Θ, dt, y₀, y₁, k, Val{cache isa OrdinaryDiffEqMutableCache}, idxs, T)
         l = linear_interpolant(Θ, dt, y₀, y₁, idxs, T)
@@ -703,7 +701,6 @@ end
 function partial_hermite_interpolant!(out, Θ, dt, y₀, y₁, k, cache, idxs, T::Type{Val{TI}}, differential_vars) where {TI}
     throw("how did we get here")
     @assert all(differential_vars)
-    differential_vars
     hermite_interpolant!(out, Θ, dt, y₀, y₁, k, idxs, T)
 end