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improve nongeneric methods of Base.rest #59549

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Merged
oscardssmith merged 7 commits into from
Feb 1, 2026
Merged

improve nongeneric methods of Base.rest #59549

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25c21c7
improve nongeneric methods of `Base.rest`, `Base.indexed_iterate`
nsajko Sep 13, 2025
e9ac257
Merge branch 'master' into better-dispatch-for-rest-and-indexed_iterate
nsajko Jan 27, 2026
8ed0bc2
Merge branch 'master' into better-dispatch-for-rest-and-indexed_iterate
nsajko Jan 27, 2026
c443d54
revert `indexed_iterate`-related changes
nsajko Jan 28, 2026
b653a2b
Merge branch 'master' into better-dispatch-for-rest-and-indexed_iterate
nsajko Jan 28, 2026
11bc933
Merge branch 'master' into better-dispatch-for-rest-and-indexed_iterate
nsajko Jan 29, 2026
3c8cd84
style
nsajko Jan 29, 2026
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2 changes: 1 addition & 1 deletion base/namedtuple.jl
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Expand Up @@ -159,7 +159,7 @@ end
length(t::NamedTuple) = nfields(t)
iterate(t::NamedTuple, iter=1) = iter > nfields(t) ? nothing : (getfield(t, iter), iter + 1)
rest(t::NamedTuple) = t
@inline rest(t::NamedTuple{names}, i::Int) where {names} = NamedTuple{rest(names,i)}(t)
@inline rest(t::NamedTuple{names}, i) where {names} = NamedTuple{rest(names,i::Int)}(t)
firstindex(t::NamedTuple) = 1
lastindex(t::NamedTuple) = nfields(t)
getindex(t::NamedTuple, i::Int) = getfield(t, i)
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8 changes: 6 additions & 2 deletions base/tuple.jl
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Expand Up @@ -206,8 +206,12 @@ julia> first, Base.rest(a, state)
"""
function rest end
rest(t::Tuple) = t
rest(t::Tuple, i::Int) = ntuple(x -> getfield(t, x+i-1), length(t)-i+1)
rest(a::Union{Array,Memory,Core.SimpleVector}, i::Int=1) = a[i:end]
function rest(t::Tuple, i)
let i = i::Int
ntuple(x -> getfield(t, x+i-1), length(t)-i+1)
end
end
rest(a::Union{Array,Memory,Core.SimpleVector}, i=1) = a[(i::Int):end]
rest(itr, state...) = Iterators.rest(itr, state...)

"""
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19 changes: 19 additions & 0 deletions test/core.jl
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Expand Up @@ -8193,6 +8193,25 @@ foo46503(a::Int, b::Nothing) = @invoke foo46503(a::Any, b)
foo46503(@nospecialize(a), b::Union{Nothing, Float64}) = rand() + 10
@test 10 <= foo46503(1, nothing) <= 11

@testset "inference for `rest` with unknown state argument types" begin
@testset "`Array`, `Memory`" begin
for typ in (Vector{Float32}, Matrix{Float32}, Memory{Float32})
@test (isconcretetype ∘ Base.infer_return_type)(Base.rest, Tuple{typ, Any})
for e in (Base.Compiler.is_terminates, Base.Compiler.is_notaskstate, Base.Compiler.is_nonoverlayed)
@test (e ∘ Base.infer_effects)(Base.rest, Tuple{typ, Any})
end
end
end
@testset "`Tuple`" begin
typ = NTuple{5, Float32}
@test Base.infer_return_type(Base.rest, Tuple{typ, Any}) <: Tuple
end
@testset "`NamedTuple`" begin
typ = NamedTuple{(:a, :b, :c, :d, :e), NTuple{5, Float32}}
@test Base.infer_return_type(Base.rest, Tuple{typ, Any}) <: NamedTuple
end
end

@testset "effect override on Symbol(::String)" begin
@test Core.Compiler.is_foldable(Base.infer_effects(Symbol, (String,)))
end
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