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fix #28915, identity conversion to union of tuple types #28951

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Sep 4, 2018
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fix #28915, identity conversion to union of tuple types #28951

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17 changes: 14 additions & 3 deletions base/essentials.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -264,11 +264,22 @@ function typename(a::Union)
end
typename(union::UnionAll) = typename(union.body)

convert(::Type{T}, x::T) where {T<:Tuple{Any, Vararg{Any}}} = x
convert(::Type{Tuple{}}, x::Tuple{Any, Vararg{Any}}) = throw(MethodError(convert, (Tuple{}, x)))
convert(::Type{T}, x::Tuple{Any, Vararg{Any}}) where {T<:Tuple} =
const AtLeast1 = Tuple{Any, Vararg{Any}}

# converting to empty tuple type
convert(::Type{Tuple{}}, ::Tuple{}) = ()
convert(::Type{Tuple{}}, x::AtLeast1) = throw(MethodError(convert, (Tuple{}, x)))

# converting to tuple types with at least one element
convert(::Type{T}, x::T) where {T<:AtLeast1} = x
convert(::Type{T}, x::AtLeast1) where {T<:AtLeast1} =
(convert(tuple_type_head(T), x[1]), convert(tuple_type_tail(T), tail(x))...)

# converting to Vararg tuple types
convert(::Type{Tuple{Vararg{V}}}, x::Tuple{Vararg{V}}) where {V} = x
convert(T::Type{Tuple{Vararg{V}}}, x::Tuple) where {V} =
(convert(tuple_type_head(T), x[1]), convert(T, tail(x))...)

# TODO: the following definitions are equivalent (behaviorally) to the above method
# I think they may be faster / more efficient for inference,
# if we could enable them, but are they?
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4 changes: 4 additions & 0 deletions test/ambiguous.jl
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Expand Up @@ -273,6 +273,8 @@ end
pop!(need_to_handle_undef_sparam, first(methods(Core.Compiler.same_names)))
pop!(need_to_handle_undef_sparam, which(Core.Compiler.convert, (Type{Union{Core.Compiler.Some{T}, Nothing}} where T, Core.Compiler.Some)))
pop!(need_to_handle_undef_sparam, which(Core.Compiler.convert, (Type{Union{T, Nothing}} where T, Core.Compiler.Some)))
pop!(need_to_handle_undef_sparam, which(Core.Compiler.convert, Tuple{Type{Tuple{Vararg{Int}}}, Tuple{}}))
pop!(need_to_handle_undef_sparam, which(Core.Compiler.convert, Tuple{Type{Tuple{Vararg{Int}}}, Tuple{Int8}}))
@test need_to_handle_undef_sparam == Set()
end
let need_to_handle_undef_sparam =
Expand All @@ -295,6 +297,8 @@ end
pop!(need_to_handle_undef_sparam, which(Base.nonmissingtype, Tuple{Type{Union{Missing, T}} where T}))
pop!(need_to_handle_undef_sparam, which(Base.convert, (Type{Union{Some{T}, Nothing}} where T, Some)))
pop!(need_to_handle_undef_sparam, which(Base.convert, (Type{Union{T, Nothing}} where T, Some)))
pop!(need_to_handle_undef_sparam, which(Base.convert, Tuple{Type{Tuple{Vararg{Int}}}, Tuple{}}))
pop!(need_to_handle_undef_sparam, which(Base.convert, Tuple{Type{Tuple{Vararg{Int}}}, Tuple{Int8}}))
@test need_to_handle_undef_sparam == Set()
end
end
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3 changes: 3 additions & 0 deletions test/tuple.jl
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Expand Up @@ -86,6 +86,9 @@ end
end

@test empty((1, 2.0, "c")) === ()

# issue #28915
@test convert(Union{Tuple{}, Tuple{Int}}, (1,)) === (1,)
end

@testset "size" begin
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