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Add unwrap function to allow wrapper types to avoid over-overloading convert #32613

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Add unwrap function to allow wrapper types to avoid over-overloading convert #32613

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Add unwrap function to allow wrapper types to avoid over-overloading …
quinnj Jul 17, 2019
a8eeb20
Throw a MethodError if unwrap doesn't do anyting. Also add docs for B…
quinnj Jul 26, 2019
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8 changes: 8 additions & 0 deletions base/essentials.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -165,6 +165,14 @@ function convert end

convert(::Type{Any}, @nospecialize(x)) = x
convert(::Type{T}, x::T) where {T} = x

unwrap(x) = x

function convert(::Type{T}, x) where {T}
y = unwrap(x)
return y === x ? x : convert(T, y)
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MethodError if y === x?

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Yeah, I wasn't quite sure on how this should interact (replace?) convert(Any, x), so I just simulated convert to Any

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But convert(T, x) is supposed to return something of type T. Returning x works for Any but not all T.

end

convert(::Type{Type}, x::Type) = x # the ssair optimizer is strongly dependent on this method existing to avoid over-specialization
# in the absence of inlining-enabled
# (due to fields typed as `Type`, which is generally a bad idea)
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