Fix inference regression on 1.7

[N5N3]

Since AbstractInterpolation <: AbstractArray, there's no need to define ndims and eltype ourself. gridtype is broken, (and unused), so I remove it. itptype is modified to avoid the recursive call of supertype.

[codecov[bot]]

Codecov Report

Merging #471 (d517db8) into master (827895e) will increase coverage by 8.98%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #471      +/-   ##
==========================================
+ Coverage   76.42%   85.41%   +8.98%     
==========================================
  Files          26       26              
  Lines        1421     1741     +320     
==========================================
+ Hits         1086     1487     +401     
+ Misses        335      254      -81     

Impacted Files	Coverage Δ
src/Interpolations.jl	79.36% <100.00%> (+11.82%)	:arrow_up:
src/filter1d.jl	91.66% <0.00%> (-2.88%)	:arrow_down:
src/io.jl	95.29% <0.00%> (-0.66%)	:arrow_down:
src/deprecations.jl	2.56% <0.00%> (-0.38%)	:arrow_down:
src/rewrite.jl	0.00% <0.00%> (ø)
src/lanczos/lanczos.jl	100.00% <0.00%> (ø)
src/chainrules/chainrules.jl	100.00% <0.00%> (ø)
src/monotonic/monotonic.jl	94.57% <0.00%> (+1.05%)	:arrow_up:
src/gridded/indexing.jl	75.21% <0.00%> (+3.30%)	:arrow_up:
src/iterate.jl	100.00% <0.00%> (+3.44%)	:arrow_up:
... and 16 more

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[mkitti]

Also tracking https://github.com/JuliaLang/julia/issues/43368 https://github.com/JuliaLang/julia/issues/43296

[N5N3]

This PR should be enough as a temporary fix. Do we need test for itptype? looks like it is used only in count_interp_dims. Edit: Well, looks like the count_interp_dims api is also insufficient.

julia> itp = CubicSplineInterpolation((1:100,1:100),randn(100,100));

julia> Interpolations.count_interp_dims(typeof(itp))
ERROR: MethodError: no method matching count_interp_dims(::Type{BSpline{Cubic{Line{OnGrid}}}})
Closest candidates are:
  count_interp_dims(::Type{IT}, ::Any) where IT<:Interpolations.InterpolationType at C:\Users\MYJ\.julia\packages\Interpolations\3gTQB\src\Interpolations.jl:164  count_interp_dims(::Type{IT}, ::Any) where {N, IT<:Tuple{Vararg{Interpolations.InterpolationType, N}}} at C:\Users\MYJ\.julia\packages\Interpolations\3gTQB\src\Interpolations.jl:165
  count_interp_dims(::Type{BSI}, ::Any) where BSI<:Interpolations.BSplineInterpolation at C:\Users\MYJ\.julia\packages\Interpolations\3gTQB\src\b-splines\b-splines.jl:157
  ...
Stacktrace:
 [1] count_interp_dims(#unused#::Type{BSpline{Cubic{Line{OnGrid}}}}, n::Int64)
   @ Interpolations C:\Users\MYJ\.julia\packages\Interpolations\3gTQB\src\Interpolations.jl:164
 [2] count_interp_dims(#unused#::Type{Interpolations.Extrapolation{Float64, 2, ScaledInterpolation{Float64, 2, Interpolations.BSplineInterpolation{Float64, 2, OffsetArrays.OffsetMatrix{Float64, Matrix{Float64}}, BSpline{Cubic{Line{OnGrid}}}, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, BSpline{Cubic{Line{OnGrid}}}, Tuple{UnitRange{Int64}, UnitRange{Int64}}}, BSpline{Cubic{Line{OnGrid}}}, Throw{Nothing}}})
   @ Interpolations C:\Users\MYJ\.julia\packages\Interpolations\3gTQB\src\Interpolations.jl:163
 [3] top-level scope
   @ REPL[21]:1

[mkitti]

Can you write a test for the one line you added?

[N5N3]

test added

[mkitti]

Merging