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fix an invariance bug in limit_type_depth. part of #23786 #23800

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Sep 21, 2017
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fix an invariance bug in limit_type_depth. part of #23786 #23800

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11 changes: 8 additions & 3 deletions base/inference.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -837,7 +837,7 @@ function limit_type_depth(@nospecialize(t), d::Int, cov::Bool, vars::Vector{Type
end
ub = Any
else
ub = limit_type_depth(v.ub, d - 1, true)
ub = limit_type_depth(v.ub, d - 1, cov, vars)
end
if v.lb === Bottom || type_depth(v.lb) > d
# note: lower bounds need to be widened by making them lower
Expand All @@ -855,7 +855,8 @@ function limit_type_depth(@nospecialize(t), d::Int, cov::Bool, vars::Vector{Type
if d < 0
if isvarargtype(t)
# never replace Vararg with non-Vararg
return Vararg{limit_type_depth(P[1], d, cov, vars), P[2]}
# passing depth=0 avoids putting a bare typevar here, for the diagonal rule
return Vararg{limit_type_depth(P[1], 0, cov, vars), P[2]}
end
widert = t.name.wrapper
if !(t <: widert)
Expand All @@ -870,7 +871,11 @@ function limit_type_depth(@nospecialize(t), d::Int, cov::Bool, vars::Vector{Type
return var
end
stillcov = cov && (t.name === Tuple.name)
Q = map(x -> limit_type_depth(x, d - 1, stillcov, vars), P)
newdepth = d - 1
if isvarargtype(t)
newdepth = max(newdepth, 0)
end
Q = map(x -> limit_type_depth(x, newdepth, stillcov, vars), P)
R = t.name.wrapper{Q...}
if cov && !stillcov
for var in vars
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7 changes: 7 additions & 0 deletions test/inference.jl
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Expand Up @@ -1218,3 +1218,10 @@ let c(::Type{T}, x) where {T<:Array} = T,
f() = c(Vector{Any[Int][1]}, [1])
@test f() === Vector{Int}
end

# issue #23786
struct T23786{D<:Tuple{Vararg{Vector{T} where T}}, N}
end
let t = Tuple{Type{T23786{D, N} where N where D<:Tuple{Vararg{Array{T, 1} where T, N} where N}}}
@test Core.Inference.limit_type_depth(t, 4) >: t
end