Missing TypedSlot in boolean if chains #36230
Description
Inference fails to take full advantage of the knowledge that a and b are both Symbols:
julia> function symcmp(vec)
a, b = vec[1], vec[2]
if isa(a, Symbol) && isa(b, Symbol)
return a == b
end
return false
end
symcmp (generic function with 1 method)
julia> code_typed(symcmp, (Vector{Any},))
1-element Array{Any,1}:
CodeInfo(
1 ── %1 = Base.arrayref(true, vec, 1)::Any
│ %2 = Base.arrayref(true, vec, 2)::Any
│ %3 = (%1 isa Main.Symbol)::Bool
└─── goto #3 if not %3
2 ── %5 = (%2 isa Main.Symbol)::Bool
└─── goto #4
3 ── nothing::Nothing
4 ┄─ %8 = φ (#2 => %5, #3 => false)::Bool
└─── goto #11 if not %8
5 ── %10 = π (%2, Symbol)
│ %11 = Main.:(==)::Core.Compiler.Const(==, false)
│ %12 = (isa)(%1, WeakRef)::Bool
└─── goto #7 if not %12
6 ── %14 = π (%1, WeakRef)
│ %15 = invoke %11(%14::WeakRef, %10::Symbol)::Union{Missing, Bool}
└─── goto #10
7 ── %17 = (isa)(%1, Missing)::Bool
└─── goto #9 if not %17
8 ── goto #10
9 ── %20 = (%1 == %10)::Union{Missing, Bool}
└─── goto #10
10 ┄ %22 = φ (#6 => %15, #8 => $(QuoteNode(missing)), #9 => %20)::Union{Missing, Bool}
└─── return %22
11 ─ return false
) => Union{Missing, Bool}Interestingly, the pure && chain does not have the same problem:
julia> function symcmp(vec)
a, b = vec[1], vec[2]
isa(a, Symbol) && isa(b, Symbol) && return a == b
return false
end
symcmp (generic function with 1 method)
julia> code_typed(symcmp, (Vector{Any},))
1-element Array{Any,1}:
CodeInfo(
1 ─ %1 = Base.arrayref(true, vec, 1)::Any
│ %2 = Base.arrayref(true, vec, 2)::Any
│ %3 = (%1 isa Main.Symbol)::Bool
└── goto #5 if not %3
2 ─ %5 = (%2 isa Main.Symbol)::Bool
└── goto #4 if not %5
3 ─ %7 = π (%1, Symbol)
│ %8 = π (%2, Symbol)
│ %9 = (%7 === %8)::Bool
└── return %9
4 ─ nothing::Nothing
5 ┄ return false
) => BoolIt may not be exactly the same issue (it also involves constant-propagation), but this is also not inferred successfully:
julia> code_typed(Meta.isexpr, (Any, Symbol, Int))
1-element Array{Any,1}:
CodeInfo(
1 ─ %1 = (ex isa Base.Meta.Expr)::Bool
└── goto #3 if not %1
2 ─ %3 = π (ex, Expr)
│ %4 = Base.getfield(%3, :head)::Symbol
│ %5 = (%4 === heads)::Bool
└── goto #4
3 ─ goto #4
4 ┄ %8 = φ (#2 => %5, #3 => false)::Bool
└── goto #6 if not %8
5 ─ %10 = Base.getproperty(ex, :args)::Any
│ %11 = Base.Meta.length(%10)::Any
│ %12 = (%11 == n)::Any
└── return %12
6 ─ return false
) => AnyAnd finally, in a dream world, inference would know that a successful isexpr call implies that ex::Expr. This is assumed all over the place, e.g.,
Lines 1038 to 1039 in 38f2c59
item.args is inferred as Any. This affects even the 2-argument form, e.g.,
julia> function useisexpr(ex)
if isexpr(ex, :(=))
lhs, rhs = ex.args[1], ex.args[2]
return lhs
end
return nothing
end
julia> code_typed(useisexpr, (Any,))
1-element Array{Any,1}:
CodeInfo(
1 ─ %1 = (ex isa Base.Meta.Expr)::Bool
└── goto #3 if not %1
2 ─ %3 = π (ex, Expr)
│ %4 = Base.getfield(%3, :head)::Symbol
│ %5 = (%4 === :(=))::Bool
└── goto #4
3 ─ goto #4
4 ┄ %8 = φ (#2 => %5, #3 => false)::Bool
└── goto #6 if not %8
5 ─ %10 = Base.getproperty(ex, :args)::Any
│ %11 = Base.getindex(%10, 1)::Any
│ %12 = Base.getproperty(ex, :args)::Any
│ Base.getindex(%12, 2)::Any
└── return %11
6 ─ return Main.nothing
) => AnyI recognize this might be more than one issue and will be happy to split it up if desired.
I've tagged this with latency because it seems to be a really common source of invalidations for packages like JuliaInterpreter and similar that have to deal with a lot of poorly-typed data. I constantly think I'm being careful, but often it's not working. (Noticed while investigating #36005, though @KristofferC pointed this out to me earlier.)