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field/property accessors for StaticSymbol #83

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field/property accessors for StaticSymbol #83

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1ae9796
field/property accessors for StaticSymbol
Tokazama Sep 3, 2022
52427c1
fix ambiguity
Tokazama Sep 3, 2022
48c85a8
Update src/Static.jl
Tokazama Sep 3, 2022
4fa941e
format + more tests
Tokazama Sep 4, 2022
ad58f52
version bump
Tokazama Sep 5, 2022
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37 changes: 28 additions & 9 deletions src/Static.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -437,15 +437,6 @@ Base.real(@nospecialize(x::StaticNumber)) = x
Base.real(@nospecialize(T::Type{<:StaticNumber})) = eltype(T)
Base.imag(@nospecialize(x::StaticNumber)) = zero(x)

"""
field_type(::Type{T}, f)

Functionally equivalent to `fieldtype(T, f)` except `f` may be a static type.
"""
@inline field_type(T::Type, f::Union{Int, Symbol}) = fieldtype(T, f)
@inline field_type(::Type{T}, ::StaticInt{N}) where {T, N} = fieldtype(T, N)
@inline field_type(::Type{T}, ::StaticSymbol{S}) where {T, S} = fieldtype(T, S)

Base.rad2deg(::StaticFloat64{M}) where {M} = StaticFloat64(rad2deg(M))
Base.deg2rad(::StaticFloat64{M}) where {M} = StaticFloat64(deg2rad(M))
@generated Base.cbrt(::StaticFloat64{M}) where {M} = StaticFloat64(cbrt(M))
Expand Down Expand Up @@ -939,4 +930,32 @@ function Base.show(io::IO, m::MIME"text/plain", @nospecialize(x::NDIndex))
show(io, m, Tuple(x))
end

# field and property accessors
"""
field_type(::Type{T}, f)

Functionally equivalent to `fieldtype(T, f)` except `f` may be a static type.
"""
@inline field_type(T::Type, f::Union{Int, Symbol}) = fieldtype(T, f)
@inline field_type(::Type{T}, ::StaticInt{N}) where {T, N} = fieldtype(T, N)
@inline field_type(::Type{T}, ::StaticSymbol{S}) where {T, S} = fieldtype(T, S)

(::Base.Fix2{typeof(getfield),<:Union{StaticSymbol{f},StaticInt{f}}})(x) where {f} = getfield(x, f)
(::Base.Fix2{typeof(fieldtype),<:Union{StaticSymbol{f},StaticInt{f}}})(x) where {f} = fieldtype(x, f)

Base.getproperty(x, ::StaticSymbol{S}) where {S} = getproperty(x, S)
Base.setproperty!(x, ::StaticSymbol{S}, v) where {S} = setproperty!(x, S, v)
Base.hasproperty(x, ::StaticSymbol{S}) where {S} = hasproperty(x, S)

Base.getindex(nt::NamedTuple, ::StaticSymbol{S}) where {S} = getfield(nt, S)
function Base.getindex(nt::NamedTuple, idxs::Tuple{<:StaticSymbol,Vararg{<:StaticSymbol}})
NamedTuple{known(idxs)}(nt)
end
function Base.setindex(nt::NamedTuple, v, ::StaticSymbol{S}) where {S}
merge(nt, NamedTuple{(S,)}((v,)))
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@cscherrer cscherrer Sep 5, 2022 •
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For named tuples, Base.merge is not type-stable for nested structures. It uses if @generated, which seems to allow the compiler to give up very early on type inference.

I've solved this in my packages by defining an alternate function to use instead of merge that's always generated (so no type-unstable fallback). I'd file an issue about this, but I so often see compiler speed favored over strong type inference, so I'm not sure it would be well-received.

Just mentioning in case that could also be an issue here.

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Do you have a mwe example where this fails so I can have a test that avoids this?

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Also worth considering: Should this be

function Base.setindex(nt::NamedTuple{N,T}, v, ::StaticSymbol{S}) where {S,N,T}

?

That would help it to specialize for the NamedTuple, which may help merge instability be a non-issue. Details here in the Julia docs.

The tricky thing with all of this is that the compiler makes so few guarantees. Type stability is very context-dependent, even depending on what's been compiled so far. So code that seems fine when I write it can have subtle problems downstream.

Sorry this comment is so long. As might be obvious, I think there are lots of open questions around this kind of thing.

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Do you have a mwe example where this fails so I can have a test that avoids this?

No, I guess it's more of a "this might bite us". But then again, it may not. That's the problem with lack of compiler guarantees :)

Maybe the best way to handle this is to leave the code as-is, but add a comment to make it easier later in case this becomes a problem. I think I'd point to the specialization link in the docs and mention the fact that if @generated in Base.merge can lead to type instability.

end
function Base.setindex(nt::NamedTuple, vs, idxs::Tuple{Vararg{<:StaticSymbol}})
merge(nt, NamedTuple{known(idxs)}((vs...,)))
end

end
9 changes: 9 additions & 0 deletions test/runtests.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,15 @@ Aqua.test_all(Static)
@test @inferred(StaticSymbol(x, y, z)) === static(:xy1)
@test @inferred(static(nothing)) === nothing
@test_throws ErrorException static([])
nt = (x = 1, y = 2)
@test nt[static(:x)] ===
getproperty(nt, static(:x)) ===
Base.Fix2(getfield, static(:x))(nt) === 1
@test hasproperty(nt, static(:x))
@test Base.setindex((a=1, b=2, c=3), 4, static(:b)) ==
(a = 1, b = 4, c = 3)
@test Base.setindex((a=1, b=2, c=3), (4, 5), (static(:b), static(:d))) ==
(a = 1, b = 4, c = 3, d = 5)
end

@testset "StaticInt" begin
Expand Down