#38002

Committed 06 Feb 2025 06:14AM UTC coverage: 20.322% (-2.4%) from 22.722%

Build # #38002

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push

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web-flow

Commit Message

bpart: Fully switch to partitioned semantics (#57253)

This is the final PR in the binding partitions series (modulo bugs and
tweaks), i.e. it closes #54654 and thus closes #40399, which was the
original design sketch.

This thus activates the full designed semantics for binding partitions,
in particular allowing safe replacement of const bindings. It in
particular allows struct redefinitions. This thus closes
timholy/Revise.jl#18 and also closes #38584.

The biggest semantic change here is probably that this gets rid of the
notion of "resolvedness" of a binding. Previously, a lot of the behavior
of our implementation depended on when bindings were "resolved", which
could happen at basically an arbitrary point (in the compiler, in REPL
completion, in a different thread), making a lot of the semantics around
bindings ill- or at least implementation-defined. There are several
related issues in the bugtracker, so this closes #14055 closes #44604
closes #46354 closes #30277

It is also the last step to close #24569.
It also supports bindings for undef->defined transitions and thus closes
#53958 closes #54733 - however, this is not activated yet for
performance reasons and may need some further optimization.

Since resolvedness no longer exists, we need to replace it with some
hopefully more well-defined semantics. I will describe the semantics
below, but before I do I will make two notes:

1. There are a number of cases where these semantics will behave
slightly differently than the old semantics absent some other task going
around resolving random bindings.
2. The new behavior (except for the replacement stuff) was generally
permissible under the old semantics if the bindings happened to be
resolved at the right time.

With all that said, there are essentially three "strengths" of bindings:

1. Implicit Bindings: Anything implicitly obtained from `using Mod`, "no
binding", plus slightly more exotic corner cases around conflicts

2. Weakly declared bindin... (continued)

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16.3

/base/tuple.jl

# This file is a part of Julia. License is MIT: https://julialang.org/license

# Document NTuple here where we have everything needed for the doc system
"""
    NTuple{N, T}

A compact way of representing the type for a tuple of length `N` where all elements are of type `T`.

# Examples
```jldoctest
julia> isa((1, 2, 3, 4, 5, 6), NTuple{6, Int})
true
```

See also [`ntuple`](@ref).
"""
NTuple

# convenience function for extracting N from a Tuple (if defined)
# else return `nothing` for anything else given (such as Vararg or other non-sized Union)
_counttuple(::Type{<:NTuple{N,Any}}) where {N} = N
_counttuple(::Type) = nothing

## indexing ##

length(@nospecialize t::Tuple) = nfields(t)
firstindex(@nospecialize t::Tuple) = 1
lastindex(@nospecialize t::Tuple) = length(t)
size(@nospecialize(t::Tuple), d::Integer) = (d == 1) ? length(t) : throw(ArgumentError("invalid tuple dimension $d"))
axes(@nospecialize t::Tuple) = (OneTo(length(t)),)
getindex(@nospecialize(t::Tuple), i::Int) = getfield(t, i, @_boundscheck)
getindex(@nospecialize(t::Tuple), i::Integer) = getfield(t, convert(Int, i), @_boundscheck)
__safe_getindex(@nospecialize(t::Tuple), i::Int) = (@_nothrow_noub_meta; getfield(t, i, false))
getindex(t::Tuple, r::AbstractArray{<:Any,1}) = (eltype(t)[t[ri] for ri in r]...,)
getindex(t::Tuple, b::AbstractArray{Bool,1}) = length(b) == length(t) ? getindex(t, findall(b)) : throw(BoundsError(t, b))
getindex(t::Tuple, c::Colon) = t

get(t::Tuple, i::Integer, default) = i in 1:length(t) ? getindex(t, i) : default
get(f::Callable, t::Tuple, i::Integer) = i in 1:length(t) ? getindex(t, i) : f()

# returns new tuple; N.B.: becomes no-op if `i` is out-of-bounds

"""
    setindex(t::Tuple, v, i::Integer)

Creates a new tuple similar to `t` with the value at index `i` set to `v`.
Throws a `BoundsError` when out of bounds.

# Examples
```jldoctest
julia> Base.setindex((1, 2, 6), 2, 3) == (1, 2, 2)
true
```
"""
function setindex(x::Tuple, v, i::Integer)
    @boundscheck 1 <= i <= length(x) || throw(BoundsError(x, i))
    @inline
    _setindex(v, i, x...)
end

function _setindex(v, i::Integer, args::Vararg{Any,N}) where {N}
    @inline
    return ntuple(j -> ifelse(j == i, v, args[j]), Val{N}())::NTuple{N, Any}
end


## iterating ##

function iterate(@nospecialize(t::Tuple), i::Int=1)
    @inline
    @_nothrow_meta
    return (1 <= i <= length(t)) ? (t[i], i + 1) : nothing
end

keys(@nospecialize t::Tuple) = OneTo(length(t))

"""
    prevind(A, i)

Return the index before `i` in `A`. The returned index is often equivalent to
`i - 1` for an integer `i`. This function can be useful for generic code.

!!! warning
    The returned index might be out of bounds. Consider using
    [`checkbounds`](@ref).

See also: [`nextind`](@ref).

# Examples
```jldoctest
julia> x = [1 2; 3 4]
2×2 Matrix{Int64}:
 1  2
 3  4

julia> prevind(x, 4) # valid result
3

julia> prevind(x, 1) # invalid result
0

julia> prevind(x, CartesianIndex(2, 2)) # valid result
CartesianIndex(1, 2)

julia> prevind(x, CartesianIndex(1, 1)) # invalid result
CartesianIndex(2, 0)
```
"""
function prevind end

"""
    nextind(A, i)

Return the index after `i` in `A`. The returned index is often equivalent to
`i + 1` for an integer `i`. This function can be useful for generic code.

!!! warning
    The returned index might be out of bounds. Consider using
    [`checkbounds`](@ref).

See also: [`prevind`](@ref).

# Examples
```jldoctest
julia> x = [1 2; 3 4]
2×2 Matrix{Int64}:
 1  2
 3  4

julia> nextind(x, 1) # valid result
2

julia> nextind(x, 4) # invalid result
5

julia> nextind(x, CartesianIndex(1, 1)) # valid result
CartesianIndex(2, 1)

julia> nextind(x, CartesianIndex(2, 2)) # invalid result
CartesianIndex(1, 3)
```
"""
function nextind end

prevind(@nospecialize(t::Tuple), i::Integer) = Int(i)-1
nextind(@nospecialize(t::Tuple), i::Integer) = Int(i)+1

function keys(t::Tuple, t2::Tuple...)
    @inline
    OneTo(_maxlength(t, t2...))
end
_maxlength(t::Tuple) = length(t)
function _maxlength(t::Tuple, t2::Tuple, t3::Tuple...)
    @inline
    max(length(t), _maxlength(t2, t3...))
end

# this allows partial evaluation of bounded sequences of next() calls on tuples,
# while reducing to plain next() for arbitrary iterables.
indexed_iterate(t::Tuple, i::Int, state=1) = (@inline; (getfield(t, i), i+1))
indexed_iterate(a::Array, i::Int, state=1) = (@inline; (a[i], i+1))
function indexed_iterate(I, i)
    x = iterate(I)
    x === nothing && throw(BoundsError(I, i))
    x
end
function indexed_iterate(I, i, state)
    x = iterate(I, state)
    x === nothing && throw(BoundsError(I, i))
    x
end

"""
    Base.rest(collection[, itr_state])

Generic function for taking the tail of `collection`, starting from a specific iteration
state `itr_state`. Return a `Tuple`, if `collection` itself is a `Tuple`, a subtype of
`AbstractVector`, if `collection` is an `AbstractArray`, a subtype of `AbstractString`
if `collection` is an `AbstractString`, and an arbitrary iterator, falling back to
`Iterators.rest(collection[, itr_state])`, otherwise.

Can be overloaded for user-defined collection types to customize the behavior of [slurping
in assignments](@ref destructuring-assignment) in final position, like `a, b... = collection`.

!!! compat "Julia 1.6"
    `Base.rest` requires at least Julia 1.6.

See also: [`first`](@ref first), [`Iterators.rest`](@ref), [`Base.split_rest`](@ref).

# Examples
```jldoctest
julia> a = [1 2; 3 4]
2×2 Matrix{Int64}:
 1  2
 3  4

julia> first, state = iterate(a)
(1, 2)

julia> first, Base.rest(a, state)
(1, [3, 2, 4])
```
"""
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::Array, i::Int=1) = a[i:end]
rest(a::Core.SimpleVector, i::Int=1) = a[i:end]
rest(itr, state...) = Iterators.rest(itr, state...)

"""
    Base.split_rest(collection, n::Int[, itr_state]) -> (rest_but_n, last_n)

Generic function for splitting the tail of `collection`, starting from a specific iteration
state `itr_state`. Returns a tuple of two new collections. The first one contains all
elements of the tail but the `n` last ones, which make up the second collection.

The type of the first collection generally follows that of [`Base.rest`](@ref), except that
the fallback case is not lazy, but is collected eagerly into a vector.

Can be overloaded for user-defined collection types to customize the behavior of [slurping
in assignments](@ref destructuring-assignment) in non-final position, like `a, b..., c = collection`.

!!! compat "Julia 1.9"
    `Base.split_rest` requires at least Julia 1.9.

See also: [`Base.rest`](@ref).

# Examples
```jldoctest
julia> a = [1 2; 3 4]
2×2 Matrix{Int64}:
 1  2
 3  4

julia> first, state = iterate(a)
(1, 2)

julia> first, Base.split_rest(a, 1, state)
(1, ([3, 2], [4]))
```
"""
function split_rest end
function split_rest(itr, n::Int, state...)
    if IteratorSize(itr) == IsInfinite()
        throw(ArgumentError("Cannot split an infinite iterator in the middle."))
    end
    return _split_rest(rest(itr, state...), n)
end
_split_rest(itr, n::Int) = _split_rest(collect(itr), n)
function _check_length_split_rest(len, n)
    len < n && throw(ArgumentError(
        "The iterator only contains $len elements, but at least $n were requested."
    ))
end
function _split_rest(a::Union{AbstractArray, Core.SimpleVector}, n::Int)
    _check_length_split_rest(length(a), n)
    return a[begin:end-n], a[end-n+1:end]
end

@eval split_rest(t::Tuple, n::Int, i=1) = ($(Expr(:meta, :aggressive_constprop)); (t[i:end-n], t[end-n+1:end]))

# Use dispatch to avoid a branch in first
first(::Tuple{}) = throw(ArgumentError("tuple must be non-empty"))
first(t::Tuple) = t[1]

# eltype

eltype(::Type{Tuple{}}) = Bottom
# the <: here makes the runtime a bit more complicated (needing to check isdefined), but really helps inference
eltype(t::Type{<:Tuple{Vararg{E}}}) where {E} = @isdefined(E) ? (E isa Type ? E : Union{}) : _compute_eltype(t)
eltype(t::Type{<:Tuple}) = _compute_eltype(t)
function _compute_eltype(@nospecialize t)
    @_total_meta
    has_free_typevars(t) && return Any
    t´ = unwrap_unionall(t)
    # Given t = Tuple{Vararg{S}} where S<:Real, the various
    # unwrapping/wrapping/va-handling here will return Real
    if t´ isa Union
        return promote_typejoin(_compute_eltype(rewrap_unionall(t´.a, t)),
                                _compute_eltype(rewrap_unionall(t´.b, t)))
    end
    p = (t´::DataType).parameters
    length(p) == 0 && return Union{}
    elt = rewrap_unionall(unwrapva(p[1]), t)
    elt isa Type || return Union{} # Tuple{2} is legal as a Type, but the eltype is Union{} since it is uninhabited
    r = elt
    for i in 2:length(p)
        r === Any && return r # if we've already reached Any, it can't widen any more
        elt = rewrap_unionall(unwrapva(p[i]), t)
        elt isa Type || return Union{} # Tuple{2} is legal as a Type, but the eltype is Union{} since it is uninhabited
        r = promote_typejoin(elt, r)
    end
    return r
end

# We'd like to be able to infer eltype(::Tuple), which needs to be able to
# look at these four methods:
#
# julia> methods(Base.eltype, Tuple{Type{<:Tuple}})
# 4 methods for generic function "eltype" from Base:
# [1] eltype(::Type{Union{}})
#  @ abstractarray.jl:234
# [2] eltype(::Type{Tuple{}})
#  @ tuple.jl:199
# [3] eltype(t::Type{<:Tuple{Vararg{E}}}) where E
#  @ tuple.jl:200
# [4] eltype(t::Type{<:Tuple})
#  @ tuple.jl:209
typeof(function eltype end).name.max_methods = UInt8(4)

# key/val types
keytype(@nospecialize t::Tuple) = keytype(typeof(t))
keytype(@nospecialize T::Type{<:Tuple}) = Int

valtype(@nospecialize t::Tuple) = valtype(typeof(t))
valtype(@nospecialize T::Type{<:Tuple}) = eltype(T)

# version of tail that doesn't throw on empty tuples (used in array indexing)
safe_tail(t::Tuple) = tail(t)
safe_tail(t::Tuple{}) = ()

# front (the converse of tail: it skips the last entry)

"""
    front(x::Tuple)::Tuple

Return a `Tuple` consisting of all but the last component of `x`.

See also: [`first`](@ref), [`tail`](@ref Base.tail).

# Examples
```jldoctest
julia> Base.front((1,2,3))
(1, 2)

julia> Base.front(())
ERROR: ArgumentError: Cannot call front on an empty tuple.
```
"""
function front(t::Tuple)
    @inline
    _front(t...)
end
_front() = throw(ArgumentError("Cannot call front on an empty tuple."))
_front(v) = ()
function _front(v, t...)
    @inline
    (v, _front(t...)...)
end

## mapping ##

# 1 argument function
map(f, t::Tuple{})              = ()
map(f, t::Tuple{Any,})          = (@inline; (f(t[1]),))
map(f, t::Tuple{Any, Any})      = (@inline; (f(t[1]), f(t[2])))
map(f, t::Tuple{Any, Any, Any}) = (@inline; (f(t[1]), f(t[2]), f(t[3])))
map(f, t::Tuple)                = (@inline; (f(t[1]), map(f,tail(t))...))
# stop inlining after some number of arguments to avoid code blowup
const Any32{N} = Tuple{Any,Any,Any,Any,Any,Any,Any,Any,
                       Any,Any,Any,Any,Any,Any,Any,Any,
                       Any,Any,Any,Any,Any,Any,Any,Any,
                       Any,Any,Any,Any,Any,Any,Any,Any,
                       Vararg{Any,N}}
const All32{T,N} = Tuple{T,T,T,T,T,T,T,T,
                         T,T,T,T,T,T,T,T,
                         T,T,T,T,T,T,T,T,
                         T,T,T,T,T,T,T,T,
                         Vararg{T,N}}
function map(f, t::Any32)
    n = length(t)
    A = Vector{Any}(undef, n)
    for i=1:n
        A[i] = f(t[i])
    end
    (A...,)
end
# 2 argument function
map(f, t::Tuple{},        s::Tuple{})        = ()
map(f, t::Tuple,          s::Tuple{})        = ()
map(f, t::Tuple{},        s::Tuple)          = ()
map(f, t::Tuple{Any,},    s::Tuple{Any,})    = (@inline; (f(t[1],s[1]),))
map(f, t::Tuple{Any,Any}, s::Tuple{Any,Any}) = (@inline; (f(t[1],s[1]), f(t[2],s[2])))
function map(f, t::Tuple, s::Tuple)
    @inline
    (f(t[1],s[1]), map(f, tail(t), tail(s))...)
end
function map(f, t::Any32, s::Any32)
    n = min(length(t), length(s))
    A = Vector{Any}(undef, n)
    for i = 1:n
        A[i] = f(t[i], s[i])
    end
    (A...,)
end
# n argument function
heads(ts::Tuple...) = map(t -> t[1], ts)
tails(ts::Tuple...) = map(tail, ts)
map(f, ::Tuple{}, ::Tuple{}...) = ()
anyempty(x::Tuple{}, xs...) = true
anyempty(x::Tuple, xs...) = anyempty(xs...)
anyempty() = false
function map(f, t1::Tuple, t2::Tuple, ts::Tuple...)
    @inline
    anyempty(t1, t2, ts...) && return ()
    (f(heads(t1, t2, ts...)...), map(f, tails(t1, t2, ts...)...)...)
end
function map(f, t1::Any32, t2::Any32, ts::Any32...)
    n = min(length(t1), length(t2), minimum(length, ts))
    A = Vector{Any}(undef, n)
    for i = 1:n
        A[i] = f(t1[i], t2[i], map(t -> t[i], ts)...)
    end
    (A...,)
end

# type-stable padding
fill_to_length(t::NTuple{N,Any}, val, ::Val{N}) where {N} = t
fill_to_length(t::Tuple{}, val, ::Val{1}) = (val,)
fill_to_length(t::Tuple{Any}, val, ::Val{2}) = (t..., val)
fill_to_length(t::Tuple{}, val, ::Val{2}) = (val, val)
#function fill_to_length(t::Tuple, val, ::Val{N}) where {N}
#    @inline
#    return (t..., ntuple(i -> val, N - length(t))...)
#end

# constructing from an iterator

function tuple_type_tail(T::Type)
    @_foldable_meta # TODO: this method is wrong (and not :foldable)
    if isa(T, UnionAll)
        return UnionAll(T.var, tuple_type_tail(T.body))
    elseif isa(T, Union)
        return Union{tuple_type_tail(T.a), tuple_type_tail(T.b)}
    else
        T.name === Tuple.name || throw(MethodError(tuple_type_tail, (T,)))
        if isvatuple(T) && length(T.parameters) == 1
            va = unwrap_unionall(T.parameters[1])::Core.TypeofVararg
            (isdefined(va, :N) && isa(va.N, Int)) || return T
            return Tuple{Vararg{va.T, va.N-1}}
        end
        return Tuple{argtail(T.parameters...)...}
    end
end

(::Type{T})(x::Tuple) where {T<:Tuple} = x isa T ? x : convert(T, x)  # still use `convert` for tuples

Tuple(x::Ref) = tuple(getindex(x))  # faster than iterator for one element
Tuple(x::Array{T,0}) where {T} = tuple(getindex(x))

(::Type{T})(itr) where {T<:Tuple} = _totuple(T, itr)

_totuple(::Type{Tuple{}}, itr, s...) = ()

function _totuple_err(@nospecialize T)
    @noinline
    throw(ArgumentError(LazyString("too few elements for tuple type ", T)))
end

function _totuple(::Type{T}, itr, s::Vararg{Any,N}) where {T,N}
    @inline
    y = iterate(itr, s...)
    y === nothing && _totuple_err(T)
    T1 = fieldtype(T, 1)
    y1 = y[1]
    t1 = y1 isa T1 ? y1 : convert(T1, y1)::T1
    # inference may give up in recursive calls, so annotate here to force accurate return type to be propagated
    rT = tuple_type_tail(T)
    ts = _totuple(rT, itr, y[2])::rT
    return (t1, ts...)::T
end

# use iterative algorithm for long tuples
function _totuple(T::Type{All32{E,N}}, itr) where {E,N}
    len = N+32
    elts = collect(E, Iterators.take(itr,len))
    if length(elts) != len
        _totuple_err(T)
    end
    (elts...,)
end

_totuple(::Type{Tuple{Vararg{E}}}, itr, s...) where {E} = (collect(E, Iterators.rest(itr,s...))...,)

_totuple(::Type{Tuple}, itr, s...) = (collect(Iterators.rest(itr,s...))...,)

# for types that `apply` knows about, just splatting is faster than collecting first
_totuple(::Type{Tuple}, itr::Array) = (itr...,)
_totuple(::Type{Tuple}, itr::SimpleVector) = (itr...,)
_totuple(::Type{Tuple}, itr::NamedTuple) = (itr...,)
_totuple(::Type{Tuple}, p::Pair) = (p.first, p.second)
_totuple(::Type{Tuple}, x::Number) = (x,) # to make Tuple(x) inferable

## find ##

_findfirst_rec(f, i::Int, ::Tuple{}) = nothing
_findfirst_rec(f, i::Int, t::Tuple) = (@inline; f(first(t)) ? i : _findfirst_rec(f, i+1, tail(t)))
function _findfirst_loop(f::Function, t)
    for i in eachindex(t)
        f(t[i]) && return i
    end
    return nothing
end
findfirst(f::Function, t::Tuple) = length(t) < 32 ? _findfirst_rec(f, 1, t) : _findfirst_loop(f, t)

findlast(f::Function, t::Tuple) = length(t) < 32 ? _findlast_rec(f, t) : _findlast_loop(f, t)
function _findlast_rec(f::Function, x::Tuple)
    r = findfirst(f, reverse(x))
    return isnothing(r) ? r : length(x) - r + 1
end
function _findlast_loop(f::Function, t)
    for i in reverse(1:length(t))
        f(t[i]) && return i
    end
    return nothing
end

## filter ##

filter_rec(f, xs::Tuple) = afoldl((ys, x) -> f(x) ? (ys..., x) : ys, (), xs...)

# use Array for long tuples
filter(f, t::Tuple) = length(t) < 32 ? filter_rec(f, t) : Tuple(filter(f, collect(t)))

## comparison ##

isequal(t1::Tuple, t2::Tuple) = length(t1) == length(t2) && _isequal(t1, t2)
_isequal(::Tuple{}, ::Tuple{}) = true
function _isequal(t1::Tuple{Any,Vararg{Any}}, t2::Tuple{Any,Vararg{Any}})
    return isequal(t1[1], t2[1]) && _isequal(tail(t1), tail(t2))
end
function _isequal(t1::Any32, t2::Any32)
    for i in eachindex(t1, t2)
        if !isequal(t1[i], t2[i])
            return false
        end
    end
    return true
end

==(t1::Tuple, t2::Tuple) = (length(t1) == length(t2)) && _eq(t1, t2)
_eq(t1::Tuple{}, t2::Tuple{}) = true
_eq_missing(t1::Tuple{}, t2::Tuple{}) = missing
function _eq(t1::Tuple, t2::Tuple)
    eq = t1[1] == t2[1]
    if eq === false
        return false
    elseif ismissing(eq)
        return _eq_missing(tail(t1), tail(t2))
    else
        return _eq(tail(t1), tail(t2))
    end
end
function _eq_missing(t1::Tuple, t2::Tuple)
    eq = t1[1] == t2[1]
    if eq === false
        return false
    else
        return _eq_missing(tail(t1), tail(t2))
    end
end
function _eq(t1::Any32, t2::Any32)
    anymissing = false
    for i in eachindex(t1, t2)
        eq = (t1[i] == t2[i])
        if ismissing(eq)
            anymissing = true
        elseif !eq
           return false
       end
    end
    return anymissing ? missing : true
end

const tuplehash_seed = UInt === UInt64 ? 0x77cfa1eef01bca90 : 0xf01bca90
hash(::Tuple{}, h::UInt) = h + tuplehash_seed
hash(t::Tuple, h::UInt) = hash(t[1], hash(tail(t), h))
function hash(t::Any32, h::UInt)
    out = h + tuplehash_seed
    for i = length(t):-1:1
        out = hash(t[i], out)
    end
    return out
end

<(::Tuple{}, ::Tuple{}) = false
<(::Tuple{}, ::Tuple) = true
<(::Tuple, ::Tuple{}) = false
function <(t1::Tuple, t2::Tuple)
    a, b = t1[1], t2[1]
    eq = (a == b)
    if ismissing(eq)
        return missing
    elseif !eq
        return a < b
    end
    return tail(t1) < tail(t2)
end
function <(t1::Any32, t2::Any32)
    n1, n2 = length(t1), length(t2)
    for i = 1:min(n1, n2)
        a, b = t1[i], t2[i]
        eq = (a == b)
        if ismissing(eq)
            return missing
        elseif !eq
           return a < b
        end
    end
    return n1 < n2
end

isless(::Tuple{}, ::Tuple{}) = false
isless(::Tuple{}, ::Tuple) = true
isless(::Tuple, ::Tuple{}) = false

"""
    isless(t1::Tuple, t2::Tuple)

Return `true` when `t1` is less than `t2` in lexicographic order.
"""
function isless(t1::Tuple, t2::Tuple)
    a, b = t1[1], t2[1]
    isless(a, b) || (isequal(a, b) && isless(tail(t1), tail(t2)))
end
function isless(t1::Any32, t2::Any32)
    n1, n2 = length(t1), length(t2)
    for i = 1:min(n1, n2)
        a, b = t1[i], t2[i]
        if !isequal(a, b)
            return isless(a, b)
        end
    end
    return n1 < n2
end

## functions ##

isempty(x::Tuple{}) = true
isempty(@nospecialize x::Tuple) = false

revargs() = ()
revargs(x, r...) = (revargs(r...)..., x)

reverse(t::Tuple) = revargs(t...)

## specialized reduction ##

prod(x::Tuple{}) = 1
# This is consistent with the regular prod because there is no need for size promotion
# if all elements in the tuple are of system size.
# It is defined here separately in order to support bootstrap, because it's needed earlier
# than the general prod definition is available.
prod(x::Tuple{Int, Vararg{Int}}) = *(x...)

all(x::Tuple{}) = true
all(x::Tuple{Bool}) = x[1]
all(x::Tuple{Bool, Bool}) = x[1]&x[2]
all(x::Tuple{Bool, Bool, Bool}) = x[1]&x[2]&x[3]
all(x::Tuple{Any}) = x[1] || return false
all(f, x::Tuple{}) = true
all(f, x::Tuple{Any}) = all((f(x[1]),))

any(x::Tuple{}) = false
any(x::Tuple{Bool}) = x[1]
any(x::Tuple{Bool, Bool}) = x[1]|x[2]
any(x::Tuple{Bool, Bool, Bool}) = x[1]|x[2]|x[3]

# a version of `in` esp. for NamedTuple, to make it pure, and not compiled for each tuple length
function sym_in(x::Symbol, itr::Tuple{Vararg{Symbol}})
    @noinline
    @_total_meta
    for y in itr
        y === x && return true
    end
    return false
end
in(x::Symbol, itr::Tuple{Vararg{Symbol}}) = sym_in(x, itr)


"""
    empty(x::Tuple)

Return an empty tuple, `()`.
"""
empty(@nospecialize x::Tuple) = ()

foreach(f, itr::Tuple) = foldl((_, x) -> (f(x); nothing), itr, init=nothing)
foreach(f, itr::Tuple, itrs::Tuple...) = foldl((_, xs) -> (f(xs...); nothing), zip(itr, itrs...), init=nothing)

circshift((@nospecialize t::Union{Tuple{},Tuple{Any}}), @nospecialize _::Integer) = t
circshift(t::Tuple{Any,Any}, shift::Integer) = iseven(shift) ? t : reverse(t)
function circshift(x::Tuple{Any,Any,Any,Vararg{Any,N}}, shift::Integer) where {N}
    @inline
    len = N + 3
    j = mod1(shift, len)
    ntuple(k -> getindex(x, k-j+ifelse(k>j,0,len)), Val(len))::Tuple
end

JuliaLang / julia / #38002

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