experimental.jl

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

"""
    Experimental

!!! warning
    Types, methods, or macros defined in this module are experimental and subject
    to change and will not have deprecations. Caveat emptor.
"""
module Experimental

"""
    Const(A::Array)

Mark an Array as constant/read-only. The invariant guaranteed is that you will not
modify an Array (through another reference) within an `@aliasscope` scope.

!!! warning
    Experimental API. Subject to change without deprecation.
"""
struct Const{T,N} <: DenseArray{T,N}
    a::Array{T,N}
end

Base.IndexStyle(::Type{<:Const}) = IndexLinear()
Base.size(C::Const) = size(C.a)
Base.axes(C::Const) = axes(C.a)
@eval Base.getindex(A::Const, i1::Int) =
    (Base.@_inline_meta; Core.const_arrayref($(Expr(:boundscheck)), A.a, i1))
@eval Base.getindex(A::Const, i1::Int, i2::Int, I::Int...) =
  (Base.@_inline_meta; Core.const_arrayref($(Expr(:boundscheck)), A.a, i1, i2, I...))

"""
    @aliasscope expr

Allows the compiler to assume that all `Const`s are not being modified through stores
within this scope, even if the compiler can't prove this to be the case.

!!! warning
    Experimental API. Subject to change without deprecation.
"""
macro aliasscope(body)
    sym = gensym()
    quote
        $(Expr(:aliasscope))
        $sym = $(esc(body))
        $(Expr(:popaliasscope))
        $sym
    end
end

end