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typeintersect: fix another stack overflow caused by circular constraints #54363

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May 7, 2024
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typeintersect: fix another stack overflow caused by circular constraints #54363

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24 changes: 13 additions & 11 deletions src/subtype.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1315,6 +1315,8 @@ static int subtype_tuple(jl_datatype_t *xd, jl_datatype_t *yd, jl_stenv_t *e, in
return ans;
}

static int try_subtype_by_bounds(jl_value_t *a, jl_value_t *b, jl_stenv_t *e);

// `param` means we are currently looking at a parameter of a type constructor
// (as opposed to being outside any type constructor, or comparing variable bounds).
// this is used to record the positions where type variables occur for the
Expand Down Expand Up @@ -1365,7 +1367,8 @@ static int subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param)
if (yy) record_var_occurrence(yy, e, param);
if (yr) {
record_var_occurrence(xx, e, param);
return subtype(xx->lb, yy->ub, e, 0);
int trysub = e->intersection ? try_subtype_by_bounds(xx->lb, yy->ub, e) : 0;
return trysub || subtype(xx->lb, yy->ub, e, 0);
}
return var_lt((jl_tvar_t*)x, y, e, param);
}
Expand Down Expand Up @@ -2497,7 +2500,7 @@ static jl_value_t *bound_var_below(jl_tvar_t *tv, jl_varbinding_t *bb, jl_stenv_

static int subtype_by_bounds(jl_value_t *x, jl_value_t *y, jl_stenv_t *e) JL_NOTSAFEPOINT;

// similar to `subtype_by_bounds`, used to avoid stack-overflow caused by circulation constraints.
// similar to `subtype_by_bounds`, used to avoid stack-overflow caused by circular constraints.
static int try_subtype_by_bounds(jl_value_t *a, jl_value_t *b, jl_stenv_t *e)
{
if (jl_is_uniontype(a))
Expand All @@ -2506,22 +2509,21 @@ static int try_subtype_by_bounds(jl_value_t *a, jl_value_t *b, jl_stenv_t *e)
else if (jl_is_uniontype(b))
return try_subtype_by_bounds(a, ((jl_uniontype_t *)b)->a, e) ||
try_subtype_by_bounds(a, ((jl_uniontype_t *)b)->b, e);
else if (jl_egal(a, b))
else if (a == jl_bottom_type || b == (jl_value_t *)jl_any_type || obviously_egal(a, b))
return 1;
else if (!jl_is_typevar(b))
return 0;
jl_varbinding_t *vb = e->vars;
while (vb != NULL) {
if (subtype_by_bounds(b, (jl_value_t *)vb->var, e) && obviously_in_union(a, vb->ub))
return 1;
vb = vb->prev;
}
return 0;
else if (jl_is_typevar(a) && subtype_by_bounds(a, b, e))
return 1;
// check if `Union{a, ...} <: b`.
jl_varbinding_t *vb = lookup(e, (jl_tvar_t *)b);
jl_value_t *blb = vb ? vb->lb : ((jl_tvar_t *)b)->lb;
return obviously_in_union(a, blb);
}

static int try_subtype_in_env(jl_value_t *a, jl_value_t *b, jl_stenv_t *e)
{
if (a == jl_bottom_type || b == (jl_value_t *)jl_any_type || try_subtype_by_bounds(a, b, e))
if (try_subtype_by_bounds(a, b, e))
return 1;
jl_savedenv_t se;
save_env(e, &se, 1);
Expand Down
13 changes: 10 additions & 3 deletions test/subtype.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -2336,9 +2336,10 @@ T46784{B<:Val, M<:AbstractMatrix} = Tuple{<:Union{B, <:Val{<:B}}, M, Union{Abstr
#issue 36185
let S = Tuple{Type{T},Array{Union{T,Missing},N}} where {T,N},
T = Tuple{Type{T},Array{Union{T,Nothing},N}} where {T,N}
@testintersect(S, T, !Union{})
@test_broken typeintersect(S, T) != S
@test_broken typeintersect(T, S) != T
I = typeintersect(S, T)
@test I == typeintersect(T, S) != Union{}
@test_broken I <: S
@test_broken I <: T
end

#issue 46736
Expand Down Expand Up @@ -2606,3 +2607,9 @@ let S = Type{T53371{A, B, C, D, E}} where {A, B<:R53371{A}, C<:R53371{A}, D<:R53
T = Type{T53371{A, B, C, D, E} where {A, B<:R53371{A}, C<:R53371{A}, D<:R53371{A}, E<:R53371{A}}}
@test !(S <: T)
end

#issue 54356
let S = Tuple{Val{Val{Union{Val{A2}, A2}}}, Val{Val{Union{Val{A2}, Val{A4}, A4}}}} where {A2, A4<:Union{Val{A2}, A2}},
T = Tuple{Vararg{Val{V}}} where {V}
@testintersect(S, T, !Union{})
end