julia - 为什么这里有一个红色的警告类型？

Question

我在以下 Julia 1.8 代码中收到红色警告

mutable struct S
    X::Int32
    const Children::Vector{Ref{S}}
end

function f2(s::Ref{S})
    x = Int32(0)
    
    chs = s[].Children
    for ch in chs
        add = ch[].X
        x += add
    end

    println("f2: $(x)")
end

function test()
    s = S(3, Vector{Ref{S}}())
    @code_warntype f2(Ref{S}(s))
end
test()

输出:

MethodInstance for f2(::Base.RefValue{S})
  from f2(s::Ref{S}) in Main at example.jl:7
Arguments
  #self#::Core.Const(f2)
  s::Base.RefValue{S}
Locals
  @_3::Union{Nothing, Tuple{Ref{S}, Int64}}      (green)
  chs::Vector{Ref{S}}
  x::Any        (red)
  ch::Ref{S}    (red)
  add::Any      (red)
Body::Nothing
1 ─       (x = Main.Int32(0))
│   %2  = Base.getindex(s)::S      
│         (chs = Base.getproperty(%2, :Children))
│   %4  = chs::Vector{Ref{S}}
│         (@_3 = Base.iterate(%4))
│   %6  = (@_3 === nothing)::Bool
│   %7  = Base.not_int(%6)::Bool
└──       goto #4 if not %7
2 ┄ %9  = @_3::Tuple{Ref{S}, Int64}            (red)
│         (ch = Core.getfield(%9, 1))      
│   %11 = Core.getfield(%9, 2)::Int64      
│   %12 = Base.getindex(ch)::Any               (red)
│         (add = Base.getproperty(%12, :X))
│         (x = x + add)
│         (@_3 = Base.iterate(%4, %11))    
│   %16 = (@_3 === nothing)::Bool
│   %17 = Base.not_int(%16)::Bool
└──       goto #4 if not %17
3 ─       goto #2
4 ┄ %20 = Base.string("f2: ", x)::String        
│   %21 = Main.println(%20)::Core.Const(nothing)
└──       return %21

据我所知，ch 的类型可以在编译时确定。 不应有任何歧义。

Answer 1

Ref 是抽象的。请改用 Base.RefValue 这是它的具体子类型，因为这可能是您想要的:

julia> mutable struct S
           X::Int32
           const Children::Vector{Base.RefValue{S}}
       end

julia> function f2(s::Ref{S})
           x = Int32(0)

           chs = s[].Children
           for ch in chs
               add = ch[].X
               x += add
           end

           println("f2: $(x)")
       end
f2 (generic function with 1 method)

julia> function test()
           s = S(3, Vector{Ref{S}}())
           @code_warntype f2(Ref{S}(s))
       end
test (generic function with 1 method)

julia> test()
MethodInstance for f2(::Base.RefValue{S})
  from f2(s::Ref{S}) @ Main REPL[11]:1
Arguments
  #self#::Core.Const(f2)
  s::Base.RefValue{S}
Locals
  @_3::Union{Nothing, Tuple{Base.RefValue{S}, Int64}}
  chs::Vector{Base.RefValue{S}}
  x::Int32
  ch::Base.RefValue{S}
  add::Int32
Body::Nothing
1 ─       (x = Main.Int32(0))
│   %2  = Base.getindex(s)::S
│         (chs = Base.getproperty(%2, :Children))
│   %4  = chs::Vector{Base.RefValue{S}}
│         (@_3 = Base.iterate(%4))
│   %6  = (@_3 === nothing)::Bool
│   %7  = Base.not_int(%6)::Bool
└──       goto #4 if not %7
2 ┄ %9  = @_3::Tuple{Base.RefValue{S}, Int64}
│         (ch = Core.getfield(%9, 1))
│   %11 = Core.getfield(%9, 2)::Int64
│   %12 = Base.getindex(ch)::S
│         (add = Base.getproperty(%12, :X))
│         (x = x + add)
│         (@_3 = Base.iterate(%4, %11))
│   %16 = (@_3 === nothing)::Bool
│   %17 = Base.not_int(%16)::Bool
└──       goto #4 if not %17
3 ─       goto #2
4 ┄ %20 = Base.string("f2: ", x)::String
│   %21 = Main.println(%20)::Core.Const(nothing)
└──       return %21