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Subtype: Avoid split y::Union when comparing with a forall var. #48603

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Merged
merged 1 commit into from
Feb 9, 2023
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Subtype: Avoid split y::Union when comparing with a forall var. #48603

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4 changes: 3 additions & 1 deletion src/subtype.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1254,7 +1254,9 @@ static int subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param)
// of unions and vars: if matching `typevar <: union`, first try to match the whole
// union against the variable before trying to take it apart to see if there are any
// variables lurking inside.
ui = pick_union_decision(e, 1);
// note: for forall var, there's no need to split y if it has no free typevars.
jl_varbinding_t *xx = lookup(e, (jl_tvar_t *)x);
ui = ((xx && xx->right) || jl_has_free_typevars(y)) && pick_union_decision(e, 1);
}
if (ui == 1)
y = pick_union_element(y, e, 1);
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4 changes: 4 additions & 0 deletions test/subtype.jl
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Expand Up @@ -2443,3 +2443,7 @@ end
let a = (isodd(i) ? Pair{Char, String} : Pair{String, String} for i in 1:2000)
@test Tuple{Type{Pair{Union{Char, String}, String}}, a...} <: Tuple{Type{Pair{K, V}}, Vararg{Pair{A, B} where B where A}} where V where K
end

#issue 48582
@test !<:(Tuple{Pair{<:T,<:T}, Val{S} where {S}} where {T<:Base.BitInteger},
Tuple{Pair{<:T,<:T}, Val{Int}} where {T<:Base.BitInteger})