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Prevent TOML invalidation by pirates of T[elements...] #39252

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Jan 15, 2021
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Prevent TOML invalidation by pirates of T[elements...] #39252

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9 changes: 8 additions & 1 deletion base/toml_parser.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -657,13 +657,20 @@ end
#########

function push!!(v::Vector, el)
# Since these types are typically non-inferrable, they are a big invalidation risk,
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@Sacha0 Sacha0 Jan 15, 2021

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Fantastic comment! :)

# and since it's used by the package-loading infrastructure the cost of invalidation
# is high. Therefore, this is written to reduce the "exposed surface area": e.g., rather
# than writing `T[el]` we write it as `push!(Vector{T}(undef, 1), el)` so that there
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@ericphanson ericphanson Jan 16, 2021

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tiny nit, but push!(Vector{T}(undef, 1), el) should be push!(Vector{T}(undef, 0), el) or the version in the code, right?

# is no ambiguity about what types of objects will be created.
T = eltype(v)
t = typeof(el)
if el isa T || t === T
push!(v, el::T)
return v
elseif T === Union{}
return t[el]
out = Vector{t}(undef, 1)
out[1] = el
return out
else
if typeof(T) === Union
newT = Any
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