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subtype.c
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// This file is a part of Julia. License is MIT: https://julialang.org/license
/*
subtyping predicate
Uses the algorithm described in section 4.2.2 of https://github.com/JeffBezanson/phdthesis/
This code adds the following features to the core algorithm:
- Type variables can be restricted to range over only concrete types.
This is done by returning false if such a variable's lower bound is not concrete.
- Diagonal rule: a type variable is concrete if it occurs more than once in
covariant position, and never in invariant position. This sounds like a syntactic
property, but actually isn't since it depends on which occurrences of a type
variable the algorithm actually uses.
- Unconstrained type vars (Bottom<:T<:Any) can match non-type values.
- Vararg types have an int-valued length parameter N (in `Vararg{T,N}`).
- Type{T}<:S if isa(T,S). Existing code assumes this, but it's not strictly
correct since a type can equal `T` without having the same representation.
- Free type variables are tolerated. This can hopefully be removed after a
deprecation period.
*/
#include <stdlib.h>
#include <string.h>
#ifdef _OS_WINDOWS_
#include <malloc.h>
#endif
#include "julia.h"
#include "julia_internal.h"
#include "julia_assert.h"
#ifdef __cplusplus
extern "C" {
#endif
// stack of bits to keep track of which combination of Union components we are
// looking at (0 for Union.a, 1 for Union.b). forall_exists_subtype and
// exists_subtype loop over all combinations by updating a binary count in
// this structure.
// Union type decision points are discovered while the algorithm works.
// If a new Union decision is encountered, the `more` flag is set to tell
// the forall/exists loop to grow the stack.
// TODO: the stack probably needs to be artificially large because of some
// deeper problem (see #21191) and could be shrunk once that is fixed
typedef struct {
int depth;
int more;
uint32_t stack[100]; // stack of bits represented as a bit vector
} jl_unionstate_t;
// Linked list storing the type variable environment. A new jl_varbinding_t
// is pushed for each UnionAll type we encounter. `lb` and `ub` are updated
// during the computation.
// Most of the complexity is due to the "diagonal rule", requiring us to
// identify which type vars range over only concrete types.
typedef struct jl_varbinding_t {
jl_tvar_t *var;
jl_value_t *lb;
jl_value_t *ub;
int8_t right; // whether this variable came from the right side of `A <: B`
// if another var that this one depends on is found to be concrete, store it
// here for reference in case that var is popped from the environment before this one.
// TODO: generalize this to multiple variables
jl_tvar_t *concretevar;
int8_t occurs_inv; // occurs in invariant position
int8_t occurs_cov; // # of occurrences in covariant position
int8_t concrete; // 1 if another variable has a constraint forcing this one to be concrete
// in covariant position, we need to try constraining a variable in different ways:
// 0 - unconstrained
// 1 - less than
// 2 - greater than
// 3 - inexpressible - occurs when the var has non-trivial overlap with another type,
// and we would need to return `intersect(var,other)`. in this case
// we choose to over-estimate the intersection by returning the var.
int8_t constraintkind;
int depth0; // # of invariant constructors nested around the UnionAll type for this var
// when this variable's integer value is compared to that of another,
// it equals `other + offset`. used by vararg length parameters.
int offset;
// array of typevars that our bounds depend on, whose UnionAlls need to be
// moved outside ours.
jl_array_t *innervars;
struct jl_varbinding_t *prev;
} jl_varbinding_t;
// subtype algorithm state
typedef struct jl_stenv_t {
// N.B.: varbindings are created on the stack and rooted there
jl_varbinding_t *vars; // type variable environment
jl_unionstate_t Lunions; // union state for unions on the left of A <: B
jl_unionstate_t Runions; // union state for unions on the right
// N.B.: envout is gc-rooted
jl_value_t **envout; // for passing caller the computed bounds of right-side variables
int envsz; // length of envout
int envidx; // current index in envout
int invdepth; // current number of invariant constructors we're nested in
int ignore_free; // treat free vars as black boxes; used during intersection
int intersection; // true iff subtype is being called from intersection
int emptiness_only; // true iff intersection only needs to test for emptiness
} jl_stenv_t;
// state manipulation utilities
// look up a type variable in an environment
#ifdef __clang_analyzer__
static jl_varbinding_t *lookup(jl_stenv_t *e, jl_tvar_t *v) JL_GLOBALLY_ROOTED JL_NOTSAFEPOINT;
#else
static jl_varbinding_t *lookup(jl_stenv_t *e, jl_tvar_t *v) JL_GLOBALLY_ROOTED JL_NOTSAFEPOINT
{
jl_varbinding_t *b = e->vars;
while (b != NULL) {
if (b->var == v) return b;
b = b->prev;
}
return b;
}
#endif
static int statestack_get(jl_unionstate_t *st, int i) JL_NOTSAFEPOINT
{
assert(i >= 0 && i < sizeof(st->stack) * 8);
// get the `i`th bit in an array of 32-bit words
return (st->stack[i>>5] & (1<<(i&31))) != 0;
}
static void statestack_set(jl_unionstate_t *st, int i, int val) JL_NOTSAFEPOINT
{
assert(i >= 0 && i < sizeof(st->stack) * 8);
if (val)
st->stack[i>>5] |= (1<<(i&31));
else
st->stack[i>>5] &= ~(1<<(i&31));
}
typedef struct {
int8_t *buf;
int rdepth;
} jl_savedenv_t;
static void save_env(jl_stenv_t *e, jl_value_t **root, jl_savedenv_t *se)
{
jl_varbinding_t *v = e->vars;
int len=0;
while (v != NULL) {
len++;
v = v->prev;
}
*root = (jl_value_t*)jl_alloc_svec(len*3);
se->buf = (int8_t*)(len ? malloc(len*2) : NULL);
#ifdef __clang_analyzer__
if (len)
memset(se->buf, 0, len*2);
#endif
int i=0, j=0; v = e->vars;
while (v != NULL) {
jl_svecset(*root, i++, v->lb);
jl_svecset(*root, i++, v->ub);
jl_svecset(*root, i++, (jl_value_t*)v->innervars);
se->buf[j++] = v->occurs_inv;
se->buf[j++] = v->occurs_cov;
v = v->prev;
}
se->rdepth = e->Runions.depth;
}
static void restore_env(jl_stenv_t *e, jl_value_t *root, jl_savedenv_t *se) JL_NOTSAFEPOINT
{
jl_varbinding_t *v = e->vars;
int i = 0, j = 0;
while (v != NULL) {
if (root) v->lb = jl_svecref(root, i);
i++;
if (root) v->ub = jl_svecref(root, i);
i++;
if (root) v->innervars = (jl_array_t*)jl_svecref(root, i);
i++;
assert(se->buf);
v->occurs_inv = se->buf[j++];
v->occurs_cov = se->buf[j++];
v = v->prev;
}
e->Runions.depth = se->rdepth;
if (e->envout && e->envidx < e->envsz)
memset(&e->envout[e->envidx], 0, (e->envsz - e->envidx)*sizeof(void*));
}
// type utilities
// quickly test that two types are identical
static int obviously_egal(jl_value_t *a, jl_value_t *b)
{
if (a == b) return 1;
if (jl_typeof(a) != jl_typeof(b)) return 0;
if (jl_is_datatype(a)) {
jl_datatype_t *ad = (jl_datatype_t*)a, *bd = (jl_datatype_t*)b;
if (ad->name != bd->name) return 0;
size_t i, np = jl_nparams(ad);
if (np != jl_nparams(bd)) return 0;
for(i=0; i < np; i++) {
if (!obviously_egal(jl_tparam(ad,i), jl_tparam(bd,i)))
return 0;
}
return 1;
}
if (jl_is_uniontype(a)) {
return obviously_egal(((jl_uniontype_t*)a)->a, ((jl_uniontype_t*)b)->a) &&
obviously_egal(((jl_uniontype_t*)a)->b, ((jl_uniontype_t*)b)->b);
}
if (jl_is_unionall(a)) {
return ((jl_unionall_t*)a)->var == ((jl_unionall_t*)b)->var &&
obviously_egal(((jl_unionall_t*)a)->body, ((jl_unionall_t*)b)->body);
}
if (jl_is_typevar(a)) return 0;
return !jl_is_type(a) && jl_egal(a,b);
}
static int obviously_unequal(jl_value_t *a, jl_value_t *b)
{
if (a == b)
return 0;
if (jl_is_concrete_type(a) || jl_is_concrete_type(b))
return 1;
if (jl_is_unionall(a)) a = jl_unwrap_unionall(a);
if (jl_is_unionall(b)) b = jl_unwrap_unionall(b);
if (jl_is_datatype(a)) {
if (b == jl_bottom_type) return 1;
if (jl_is_datatype(b)) {
jl_datatype_t *ad = (jl_datatype_t*)a, *bd = (jl_datatype_t*)b;
if (ad->name != bd->name)
return 1;
size_t i, np = jl_nparams(ad);
if (np != jl_nparams(bd)) return 1;
for(i=0; i < np; i++) {
if (obviously_unequal(jl_tparam(ad,i), jl_tparam(bd,i)))
return 1;
}
}
}
else if (a == jl_bottom_type && jl_is_datatype(b)) {
return 1;
}
if (jl_is_typevar(a) && jl_is_typevar(b) && obviously_unequal(((jl_tvar_t*)a)->ub, ((jl_tvar_t*)b)->ub))
return 1;
if (jl_is_long(a)) {
if (jl_is_long(b) && jl_unbox_long(a) != jl_unbox_long(b))
return 1;
}
else if (jl_is_long(b)) return 1;
if ((jl_is_symbol(a) || jl_is_symbol(b)) && a != b)
return 1;
return 0;
}
int jl_obviously_unequal(jl_value_t *a, jl_value_t *b)
{
return obviously_unequal(a, b);
}
static int in_union(jl_value_t *u, jl_value_t *x)
{
if (u == x) return 1;
if (!jl_is_uniontype(u)) return 0;
return in_union(((jl_uniontype_t*)u)->a, x) || in_union(((jl_uniontype_t*)u)->b, x);
}
static int obviously_disjoint(jl_value_t *a, jl_value_t *b, int specificity)
{
if (a == b || a == (jl_value_t*)jl_any_type || b == (jl_value_t*)jl_any_type)
return 0;
if (specificity && a == (jl_value_t*)jl_typeofbottom_type)
return 0;
if (jl_is_concrete_type(a) && jl_is_concrete_type(b) &&
// TODO: remove these 2 lines if and when Tuple{Union{}} === Union{}
(((jl_datatype_t*)a)->name != jl_tuple_typename ||
((jl_datatype_t*)b)->name != jl_tuple_typename))
return 1;
if (jl_is_unionall(a)) a = jl_unwrap_unionall(a);
if (jl_is_unionall(b)) b = jl_unwrap_unionall(b);
if (jl_is_datatype(a) && jl_is_datatype(b)) {
jl_datatype_t *ad = (jl_datatype_t*)a, *bd = (jl_datatype_t*)b;
if (ad->name != bd->name) {
jl_datatype_t *temp = ad;
while (temp != jl_any_type && temp->name != bd->name)
temp = temp->super;
if (temp == jl_any_type) {
temp = bd;
while (temp != jl_any_type && temp->name != ad->name)
temp = temp->super;
if (temp == jl_any_type)
return 1;
bd = temp;
}
else {
ad = temp;
}
if (specificity) {
// account for declared subtypes taking priority (issue #21710)
return 0;
}
}
int istuple = (ad->name == jl_tuple_typename);
size_t np;
if (istuple) {
size_t na = jl_nparams(ad), nb = jl_nparams(bd);
if (jl_is_va_tuple(ad)) {
na -= 1;
if (jl_is_va_tuple(bd))
nb -= 1;
}
else if (jl_is_va_tuple(bd)) {
nb -= 1;
}
else if (!specificity && na != nb) {
// note: some disjoint types (e.g. tuples of different lengths) can be more specific
return 1;
}
np = na < nb ? na : nb;
}
else {
np = jl_nparams(ad);
}
size_t i;
for(i=0; i < np; i++) {
jl_value_t *ai = jl_tparam(ad,i);
jl_value_t *bi = jl_tparam(bd,i);
if (!istuple && specificity && jl_has_free_typevars(ai)) {
// X{<:SomeDataType} and X{Union{Y,Z,...}} need to be disjoint to
// avoid this transitivity problem:
// A = Tuple{Type{LinearIndices{N,R}}, LinearIndices{N}} where {N,R}
// B = Tuple{Type{T},T} where T<:AbstractArray
// C = Tuple{Type{Union{Nothing, T}}, Union{Nothing, T}} where T
// A is more specific than B. It would be easy to think B is more specific
// than C, but we can't have that since A should not be more specific than C.
jl_value_t *aub = jl_is_typevar(ai) ? ((jl_tvar_t*)ai)->ub : ai;
jl_value_t *bub = jl_is_typevar(bi) ? ((jl_tvar_t*)bi)->ub : bi;
aub = jl_unwrap_unionall(aub);
bub = jl_unwrap_unionall(bub);
if ((jl_is_typevar(ai) + jl_is_typevar(bi) < 2) &&
aub != (jl_value_t*)jl_any_type && bub != (jl_value_t*)jl_any_type &&
((jl_is_uniontype(aub) && jl_is_datatype(bub) && !in_union(aub, bub) &&
(jl_is_typevar(bi) || !jl_is_typevar(ai))) ||
(jl_is_uniontype(bub) && jl_is_datatype(aub) && !in_union(bub, aub) &&
(jl_is_typevar(ai) || !jl_is_typevar(bi)))))
return 1;
}
if (jl_is_typevar(ai) || jl_is_typevar(bi))
continue;
if (jl_is_type(ai)) {
if (jl_is_type(bi)) {
if (istuple && (ai == jl_bottom_type || bi == jl_bottom_type))
; // TODO: this can return 1 if and when Tuple{Union{}} === Union{}
else if (obviously_disjoint(ai, bi, specificity))
return 1;
}
else if (!specificity) {
// Tuple{1} is more specific than Tuple{Any}
return 1;
}
}
else if (jl_is_type(bi)) {
if (!specificity)
return 1;
}
else if (!jl_egal(ai, bi)) {
return 1;
}
}
}
else if (a == jl_bottom_type || b == jl_bottom_type) {
return 1;
}
return 0;
}
// compute a least upper bound of `a` and `b`
static jl_value_t *simple_join(jl_value_t *a, jl_value_t *b)
{
if (a == jl_bottom_type || b == (jl_value_t*)jl_any_type || obviously_egal(a,b))
return b;
if (b == jl_bottom_type || a == (jl_value_t*)jl_any_type)
return a;
if (!(jl_is_type(a) || jl_is_typevar(a)) || !(jl_is_type(b) || jl_is_typevar(b)))
return (jl_value_t*)jl_any_type;
if (jl_is_uniontype(a) && in_union(a, b))
return a;
if (jl_is_uniontype(b) && in_union(b, a))
return b;
if (jl_is_kind(a) && jl_is_type_type(b) && jl_typeof(jl_tparam0(b)) == a)
return a;
if (jl_is_kind(b) && jl_is_type_type(a) && jl_typeof(jl_tparam0(a)) == b)
return b;
if (jl_is_typevar(a) && obviously_egal(b, ((jl_tvar_t*)a)->lb))
return a;
if (jl_is_typevar(b) && obviously_egal(a, ((jl_tvar_t*)b)->lb))
return b;
if (!jl_has_free_typevars(a) && !jl_has_free_typevars(b) &&
// issue #24521: don't merge Type{T} where typeof(T) varies
!(jl_is_type_type(a) && jl_is_type_type(b) && jl_typeof(jl_tparam0(a)) != jl_typeof(jl_tparam0(b)))) {
if (jl_subtype(a, b)) return b;
if (jl_subtype(b, a)) return a;
}
return jl_new_struct(jl_uniontype_type, a, b);
}
// compute a greatest lower bound of `a` and `b`
// in many cases, we need to over-estimate this by returning `b`.
static jl_value_t *simple_meet(jl_value_t *a, jl_value_t *b)
{
if (a == (jl_value_t*)jl_any_type || b == jl_bottom_type || obviously_egal(a,b))
return b;
if (b == (jl_value_t*)jl_any_type || a == jl_bottom_type)
return a;
if (!(jl_is_type(a) || jl_is_typevar(a)) || !(jl_is_type(b) || jl_is_typevar(b)))
return jl_bottom_type;
if (jl_is_uniontype(a) && in_union(a, b))
return b;
if (jl_is_uniontype(b) && in_union(b, a))
return a;
if (jl_is_kind(a) && jl_is_type_type(b) && jl_typeof(jl_tparam0(b)) == a)
return b;
if (jl_is_kind(b) && jl_is_type_type(a) && jl_typeof(jl_tparam0(a)) == b)
return a;
if (jl_is_typevar(a) && obviously_egal(b, ((jl_tvar_t*)a)->ub))
return a;
if (jl_is_typevar(b) && obviously_egal(a, ((jl_tvar_t*)b)->ub))
return b;
if (obviously_disjoint(a, b, 0))
return jl_bottom_type;
if (!jl_has_free_typevars(a) && !jl_has_free_typevars(b)) {
if (jl_subtype(a, b)) return a;
if (jl_subtype(b, a)) return b;
}
return b;
}
static jl_unionall_t *rename_unionall(jl_unionall_t *u)
{
jl_tvar_t *v = jl_new_typevar(u->var->name, u->var->lb, u->var->ub);
jl_value_t *t = NULL;
JL_GC_PUSH2(&v, &t);
t = jl_instantiate_unionall(u, (jl_value_t*)v);
t = jl_new_struct(jl_unionall_type, v, t);
JL_GC_POP();
return (jl_unionall_t*)t;
}
// main subtyping algorithm
static int subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param);
static jl_value_t *pick_union_element(jl_value_t *u JL_PROPAGATES_ROOT, jl_stenv_t *e, int8_t R) JL_NOTSAFEPOINT
{
jl_unionstate_t *state = R ? &e->Runions : &e->Lunions;
do {
int ui = statestack_get(state, state->depth);
state->depth++;
if (ui == 0) {
state->more = state->depth; // memorize that this was the deepest available choice
u = ((jl_uniontype_t*)u)->a;
}
else {
u = ((jl_uniontype_t*)u)->b;
}
} while (jl_is_uniontype(u));
return u;
}
static int forall_exists_subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param);
// subtype for variable bounds consistency check. needs its own forall/exists environment.
static int subtype_ccheck(jl_value_t *x, jl_value_t *y, jl_stenv_t *e)
{
if (x == y)
return 1;
if (x == jl_bottom_type && jl_is_type(y))
return 1;
if (y == (jl_value_t*)jl_any_type && jl_is_type(x))
return 1;
if (jl_is_uniontype(x) && jl_is_uniontype(y) && jl_egal(x,y))
return 1;
if (x == (jl_value_t*)jl_any_type && jl_is_datatype(y))
return 0;
jl_unionstate_t oldLunions = e->Lunions;
jl_unionstate_t oldRunions = e->Runions;
int sub;
memset(e->Lunions.stack, 0, sizeof(e->Lunions.stack));
memset(e->Runions.stack, 0, sizeof(e->Runions.stack));
e->Runions.depth = 0;
e->Runions.more = 0;
e->Lunions.depth = 0;
e->Lunions.more = 0;
sub = forall_exists_subtype(x, y, e, 0);
e->Runions = oldRunions;
e->Lunions = oldLunions;
return sub;
}
// use the current context to record where a variable occurred, for the purpose
// of determining whether the variable is concrete.
static void record_var_occurrence(jl_varbinding_t *vb, jl_stenv_t *e, int param) JL_NOTSAFEPOINT
{
if (vb != NULL && param) {
// saturate counters at 2; we don't need values bigger than that
if (param == 2 && e->invdepth > vb->depth0 && vb->occurs_inv < 2)
vb->occurs_inv++;
else if (vb->occurs_cov < 2)
vb->occurs_cov++;
}
}
// is var x's quantifier outside y's in nesting order
static int var_outside(jl_stenv_t *e, jl_tvar_t *x, jl_tvar_t *y)
{
jl_varbinding_t *btemp = e->vars;
while (btemp != NULL) {
if (btemp->var == x) return 0;
if (btemp->var == y) return 1;
btemp = btemp->prev;
}
return 0;
}
static jl_value_t *intersect_aside(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int depth);
// check that type var `b` is <: `a`, and update b's upper bound.
static int var_lt(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int param)
{
jl_varbinding_t *bb = lookup(e, b);
if (bb == NULL)
return e->ignore_free || subtype_ccheck(b->ub, a, e);
record_var_occurrence(bb, e, param);
if (!bb->right) // check ∀b . b<:a
return subtype_ccheck(bb->ub, a, e);
if (bb->ub == a)
return 1;
if (!((bb->lb == jl_bottom_type && !jl_is_type(a) && !jl_is_typevar(a)) || subtype_ccheck(bb->lb, a, e)))
return 0;
// for this to work we need to compute issub(left,right) before issub(right,left),
// since otherwise the issub(a, bb.ub) check in var_gt becomes vacuous.
if (e->intersection) {
jl_value_t *ub = intersect_aside(bb->ub, a, e, bb->depth0);
if (ub != (jl_value_t*)b)
bb->ub = ub;
}
else {
bb->ub = simple_meet(bb->ub, a);
}
assert(bb->ub != (jl_value_t*)b);
if (jl_is_typevar(a)) {
jl_varbinding_t *aa = lookup(e, (jl_tvar_t*)a);
if (aa && !aa->right && in_union(bb->lb, a) && bb->depth0 != aa->depth0 && var_outside(e, b, (jl_tvar_t*)a)) {
// an "exists" var cannot equal a "forall" var inside it unless the forall
// var has equal bounds.
return subtype_ccheck(aa->ub, aa->lb, e);
}
}
return 1;
}
// check that type var `b` is >: `a`, and update b's lower bound.
static int var_gt(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int param)
{
jl_varbinding_t *bb = lookup(e, b);
if (bb == NULL)
return e->ignore_free || subtype_ccheck(a, b->lb, e);
record_var_occurrence(bb, e, param);
if (!bb->right) // check ∀b . b>:a
return subtype_ccheck(a, bb->lb, e);
if (bb->lb == bb->ub) {
if (jl_is_typevar(bb->lb) && !jl_is_type(a) && !jl_is_typevar(a))
return var_gt((jl_tvar_t*)bb->lb, a, e, param);
if (jl_is_typevar(a) && !jl_is_type(bb->lb) && !jl_is_typevar(bb->lb))
return var_lt((jl_tvar_t*)a, bb->lb, e, param);
}
if (!((bb->ub == (jl_value_t*)jl_any_type && !jl_is_type(a) && !jl_is_typevar(a)) || subtype_ccheck(a, bb->ub, e)))
return 0;
bb->lb = simple_join(bb->lb, a);
assert(bb->lb != (jl_value_t*)b);
return 1;
}
// check that a type is concrete or quasi-concrete (Type{T}).
// this is used to check concrete typevars:
// issubtype is false if the lower bound of a concrete type var is not concrete.
static int is_leaf_bound(jl_value_t *v) JL_NOTSAFEPOINT
{
if (v == jl_bottom_type)
return 1;
if (jl_is_datatype(v)) {
if (((jl_datatype_t*)v)->abstract) {
if (jl_is_type_type(v))
return 1;//!jl_has_free_typevars(jl_tparam0(v));
return 0;
}
return ((jl_datatype_t*)v)->isconcretetype;
}
return !jl_is_type(v) && !jl_is_typevar(v);
}
static int is_leaf_typevar(jl_tvar_t *v) JL_NOTSAFEPOINT
{
return is_leaf_bound(v->lb);
}
static jl_value_t *widen_Type(jl_value_t *t JL_PROPAGATES_ROOT) JL_NOTSAFEPOINT
{
if (jl_is_type_type(t) && !jl_is_typevar(jl_tparam0(t)))
return jl_typeof(jl_tparam0(t));
if (jl_is_uniontype(t)) {
jl_value_t *a = widen_Type(((jl_uniontype_t*)t)->a);
jl_value_t *b = widen_Type(((jl_uniontype_t*)t)->b);
if (a == b)
return a;
}
return t;
}
JL_DLLEXPORT jl_array_t *jl_find_free_typevars(jl_value_t *v);
// convert a type with free variables to a typevar bounded by a UnionAll-wrapped
// version of that type.
// TODO: This loses some inference precision. For example in a case where a
// variable bound is `Vector{_}`, we could potentially infer `Type{Vector{_}} where _`,
// but this causes us to infer the larger `Type{T} where T<:Vector` instead.
// However this is needed because many contexts check `isa(sp, TypeVar)` to determine
// when a static parameter value is not known exactly.
static jl_value_t *fix_inferred_var_bound(jl_tvar_t *var, jl_value_t *ty JL_MAYBE_UNROOTED)
{
if (!jl_is_typevar(ty) && jl_has_free_typevars(ty)) {
jl_value_t *ans = ty;
jl_array_t *vs = NULL;
JL_GC_PUSH2(&ans, &vs);
vs = jl_find_free_typevars(ty);
int i;
for (i = 0; i < jl_array_len(vs); i++) {
ans = jl_type_unionall((jl_tvar_t*)jl_array_ptr_ref(vs, i), ans);
}
ans = (jl_value_t*)jl_new_typevar(var->name, jl_bottom_type, ans);
JL_GC_POP();
return ans;
}
return ty;
}
static int var_occurs_inside(jl_value_t *v, jl_tvar_t *var, int inside, int want_inv) JL_NOTSAFEPOINT;
// compare UnionAll type `u` to `t`. `R==1` if `u` came from the right side of A <: B.
static int subtype_unionall(jl_value_t *t, jl_unionall_t *u, jl_stenv_t *e, int8_t R, int param)
{
jl_varbinding_t *btemp = e->vars;
// if the var for this unionall (based on identity) already appears somewhere
// in the environment, rename to get a fresh var.
while (btemp != NULL) {
if (btemp->var == u->var ||
// outer var can only refer to inner var if bounds changed
(btemp->lb != btemp->var->lb && jl_has_typevar(btemp->lb, u->var)) ||
(btemp->ub != btemp->var->ub && jl_has_typevar(btemp->ub, u->var))) {
u = rename_unionall(u);
break;
}
btemp = btemp->prev;
}
jl_varbinding_t vb = { u->var, u->var->lb, u->var->ub, R, NULL, 0, 0, 0, 0, e->invdepth, 0, NULL, e->vars };
JL_GC_PUSH4(&u, &vb.lb, &vb.ub, &vb.innervars);
e->vars = &vb;
int ans;
if (R) {
e->envidx++;
ans = subtype(t, u->body, e, param);
e->envidx--;
// widen Type{x} to typeof(x) in argument position
if (!vb.occurs_inv)
vb.lb = widen_Type(vb.lb);
// fill variable values into `envout` up to `envsz`
if (e->envidx < e->envsz) {
jl_value_t *val;
if (!vb.occurs_inv && vb.lb != jl_bottom_type)
val = is_leaf_bound(vb.lb) ? vb.lb : (jl_value_t*)jl_new_typevar(u->var->name, jl_bottom_type, vb.lb);
else if (vb.lb == vb.ub)
val = vb.lb;
else if (vb.lb != jl_bottom_type)
// TODO: for now return the least solution, which is what
// method parameters expect.
val = vb.lb;
else if (vb.lb == u->var->lb && vb.ub == u->var->ub)
val = (jl_value_t*)u->var;
else
val = (jl_value_t*)jl_new_typevar(u->var->name, vb.lb, vb.ub);
jl_value_t *oldval = e->envout[e->envidx];
// if we try to assign different variable values (due to checking
// multiple union members), consider the value unknown.
if (oldval && !jl_egal(oldval, val))
e->envout[e->envidx] = (jl_value_t*)u->var;
else
e->envout[e->envidx] = fix_inferred_var_bound(u->var, val);
// TODO: substitute the value (if any) of this variable into previous envout entries
}
}
else {
ans = subtype(u->body, t, e, param);
}
// handle the "diagonal dispatch" rule, which says that a type var occurring more
// than once, and only in covariant position, is constrained to concrete types. E.g.
// ( Tuple{Int, Int} <: Tuple{T, T} where T) but
// !( Tuple{Int, String} <: Tuple{T, T} where T)
// Then check concreteness by checking that the lower bound is not an abstract type.
int diagonal = !vb.occurs_inv && vb.occurs_cov > 1;
if (ans && (vb.concrete || (diagonal && is_leaf_typevar(u->var)))) {
if (vb.concrete && !diagonal && !is_leaf_bound(vb.ub)) {
// a non-diagonal var can only be a subtype of a diagonal var if its
// upper bound is concrete.
ans = 0;
}
else if (jl_is_typevar(vb.lb)) {
jl_tvar_t *v = (jl_tvar_t*)vb.lb;
jl_varbinding_t *vlb = lookup(e, v);
if (vlb)
vlb->concrete = 1;
//else // TODO handle multiple variables in vb.concretevar
// ans = (v == vb.concretevar);
}
else if (!is_leaf_bound(vb.lb)) {
ans = 0;
}
if (ans) {
// if we occur as another var's lower bound, record the fact that we
// were concrete so that subtype can return true for that var.
/*
btemp = vb.prev;
while (btemp != NULL) {
if (btemp->lb == (jl_value_t*)u->var)
btemp->concretevar = u->var;
btemp = btemp->prev;
}
*/
}
}
e->vars = vb.prev;
btemp = e->vars;
if (vb.lb != vb.ub) {
while (btemp != NULL) {
jl_value_t *vu = btemp->ub;
jl_value_t *vl = btemp->lb;
// TODO: this takes a significant amount of time
if (btemp->depth0 != vb.depth0 &&
((vu != (jl_value_t*)vb.var && btemp->var->ub != vu && var_occurs_inside(vu, vb.var, 0, 1)) ||
(vl != (jl_value_t*)vb.var && btemp->var->lb != vl && var_occurs_inside(vl, vb.var, 0, 1)))) {
ans = 0; break;
}
btemp = btemp->prev;
}
}
JL_GC_POP();
return ans;
}
// unwrap <=2 layers of UnionAlls, leaving the vars in *p1 and *p2 and returning the body
static jl_value_t *unwrap_2_unionall(jl_value_t *t, jl_tvar_t **p1, jl_tvar_t **p2) JL_NOTSAFEPOINT
{
assert(t);
if (jl_is_unionall(t)) {
*p1 = ((jl_unionall_t*)t)->var;
t = ((jl_unionall_t*)t)->body;
if (jl_is_unionall(t)) {
*p2 = ((jl_unionall_t*)t)->var;
t = ((jl_unionall_t*)t)->body;
}
}
return t;
}
// check n <: (length of vararg type v)
static int check_vararg_length(jl_value_t *v, ssize_t n, jl_stenv_t *e)
{
jl_tvar_t *va_p1=NULL, *va_p2=NULL;
jl_value_t *tail = unwrap_2_unionall(v, &va_p1, &va_p2);
assert(jl_is_datatype(tail));
jl_value_t *N = jl_tparam1(tail);
// only do the check if N is free in the tuple type's last parameter
if (N != (jl_value_t*)va_p1 && N != (jl_value_t*)va_p2) {
jl_value_t *nn = jl_box_long(n);
JL_GC_PUSH1(&nn);
e->invdepth++;
int ans = subtype(nn, N, e, 2) && subtype(N, nn, e, 0);
e->invdepth--;
JL_GC_POP();
if (!ans)
return 0;
}
return 1;
}
static int subtype_tuple(jl_datatype_t *xd, jl_datatype_t *yd, jl_stenv_t *e, int param)
{
size_t lx = jl_nparams(xd), ly = jl_nparams(yd);
if (lx == 0 && ly == 0)
return 1;
size_t i=0, j=0;
int vx=0, vy=0, vvx = (lx > 0 && jl_is_vararg_type(jl_tparam(xd, lx-1)));
int vvy = (ly > 0 && jl_is_vararg_type(jl_tparam(yd, ly-1)));
if (vvx) {
if ((vvy && ly > lx) || (!vvy && ly < lx-1))
return 0;
}
else if ((vvy && ly > lx+1) || (!vvy && lx != ly)) {
return 0;
}
param = (param == 0 ? 1 : param);
jl_value_t *lastx=NULL, *lasty=NULL;
while (i < lx) {
jl_value_t *xi = jl_tparam(xd, i);
if (i == lx-1 && vvx) vx = 1;
jl_value_t *yi = NULL;
if (j < ly) {
yi = jl_tparam(yd, j);
if (j == ly-1 && vvy) vy = 1;
}
if (vx && !vy) {
if (!check_vararg_length(xi, ly+1-lx, e))
return 0;
jl_tvar_t *p1=NULL, *p2=NULL;
xi = unwrap_2_unionall(xi, &p1, &p2);
jl_value_t *N = jl_tparam1(xi);
if (N == (jl_value_t*)p1 || N == (jl_value_t*)p2)
return 0;
if (j >= ly) return 1;
xi = jl_tparam0(xi);
}
else if (j >= ly) {
return 0;
}
if (!vx && vy) {
jl_tvar_t *p1=NULL, *p2=NULL;
yi = jl_tparam0(unwrap_2_unionall(yi, &p1, &p2));
if (yi == (jl_value_t*)p1 || yi == (jl_value_t*)p2)
yi = ((jl_tvar_t*)yi)->ub;
if (!vvx && yi == (jl_value_t*)jl_any_type)
break; // if y ends in `Vararg{Any}` skip checking everything
}
if (vx && vy) {
jl_tvar_t *yp1=NULL, *yp2=NULL;
jl_value_t *yva = unwrap_2_unionall(yi, &yp1, &yp2);
jl_tvar_t *xp1=NULL, *xp2=NULL;
jl_value_t *xva = unwrap_2_unionall(xi, &xp1, &xp2);
if ((jl_value_t*)xp1 == jl_tparam1(xva) || (jl_value_t*)xp2 == jl_tparam1(xva)) {
// check for unconstrained vararg on left, constrained on right
if (jl_is_long(jl_tparam1(yva)))
return 0;
if (jl_is_typevar(jl_tparam1(yva))) {
jl_varbinding_t *ylv = lookup(e, (jl_tvar_t*)jl_tparam1(yva));
if (ylv && jl_is_long(ylv->lb))
return 0;
}
}
// skip testing element type if vararg lengths are 0
if (jl_is_datatype(xi)) {
jl_value_t *xl = jl_tparam1(xi);
if (jl_is_typevar(xl)) {
jl_varbinding_t *xlv = lookup(e, (jl_tvar_t*)xl);
if (xlv && jl_is_long(xlv->lb) && jl_unbox_long(xlv->lb) == 0)
break;
}
}
if (jl_is_datatype(yi)) {
jl_value_t *yl = jl_tparam1(yi);
if (jl_is_typevar(yl)) {
jl_varbinding_t *ylv = lookup(e, (jl_tvar_t*)yl);
if (ylv && jl_is_long(ylv->lb) && jl_unbox_long(ylv->lb) == 0)
break;
}
}
}
if (xi == lastx &&
((yi == lasty && !jl_has_free_typevars(xi) && !jl_has_free_typevars(yi)) ||
(yi == lasty && !vx && vy && jl_is_concrete_type(xi)))) {
// fast path for repeated elements
}
else if (e->Runions.depth == 0 && e->Lunions.depth == 0 && !jl_has_free_typevars(xi) && !jl_has_free_typevars(yi)) {
// fast path for separable sub-formulas
if (!jl_subtype(xi, yi))
return 0;
}
else if (!subtype(xi, yi, e, param)) {
return 0;
}
if (vx && vy) break;
lastx = xi; lasty = yi;
if (i < lx-1 || !vx)
i++;
if (j < ly-1 || !vy)
j++;
}
// TODO: handle Vararg with explicit integer length parameter
vy = vy || (j < ly && jl_is_vararg_type(jl_tparam(yd,j)));
if (vy && !vx && lx+1 >= ly) {
// in Tuple{...,tn} <: Tuple{...,Vararg{T,N}}, check (lx+1-ly) <: N
if (!check_vararg_length(jl_tparam(yd,ly-1), lx+1-ly, e))
return 0;
}
return (lx==ly && vx==vy) || (vy && (lx >= (vx ? ly : (ly-1))));
}
static int forall_exists_equal(jl_value_t *x, jl_value_t *y, 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
// diagonal rule (record_var_occurrence).
static int subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param)
{
if (jl_is_uniontype(x)) {
if (x == y) return 1;
x = pick_union_element(x, e, 0);
}
if (jl_is_uniontype(y)) {
if (x == ((jl_uniontype_t*)y)->a || x == ((jl_uniontype_t*)y)->b)
return 1;
if (jl_is_unionall(x))
return subtype_unionall(y, (jl_unionall_t*)x, e, 0, param);
int ui = 1;
if (jl_is_typevar(x)) {
// The `convert(Type{T},T)` pattern, where T is a Union, required changing priority
// 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.
jl_unionstate_t *state = &e->Runions;
ui = statestack_get(state, state->depth);
state->depth++;
if (ui == 0)
state->more = state->depth; // memorize that this was the deepest available choice
}
if (ui == 1)
y = pick_union_element(y, e, 1);
}
if (jl_is_typevar(x)) {
if (jl_is_typevar(y)) {
if (x == y) return 1;
jl_varbinding_t *xx = lookup(e, (jl_tvar_t*)x);
jl_varbinding_t *yy = lookup(e, (jl_tvar_t*)y);
jl_value_t *xub = xx ? xx->ub : ((jl_tvar_t*)x)->ub;
jl_value_t *ylb = yy ? yy->lb : ((jl_tvar_t*)y)->lb;
if (e->intersection) {
jl_value_t *xlb = xx ? xx->lb : ((jl_tvar_t*)x)->lb;
jl_value_t *yub = yy ? yy->ub : ((jl_tvar_t*)y)->ub;
// find equivalence class for typevars during intersection
if (xub == xlb && jl_is_typevar(xub))
return subtype(xub, y, e, param);
if (yub == ylb && jl_is_typevar(yub))
return subtype(x, yub, e, param);
}
int xr = xx && xx->right; // treat free variables as "forall" (left)
int yr = yy && yy->right;
if (xr) {
if (yy) record_var_occurrence(yy, e, param);
if (yr) {
if (xx) record_var_occurrence(xx, e, param);
return subtype(xx->lb, yy->ub, e, 0);
}
return var_lt((jl_tvar_t*)x, y, e, param);
}
else if (yr) {
if (xx) record_var_occurrence(xx, e, param);
return var_gt((jl_tvar_t*)y, x, e, param);
}
// check ∀x,y . x<:y
// the bounds of left-side variables never change, and can only lead
// to other left-side variables, so using || here is safe.
return subtype(xub, y, e, param) || subtype(x, ylb, e, param);
}
return var_lt((jl_tvar_t*)x, y, e, param);
}
if (jl_is_typevar(y))
return var_gt((jl_tvar_t*)y, x, e, param);
if (y == (jl_value_t*)jl_any_type && !jl_has_free_typevars(x))
return 1;
jl_value_t *ux = jl_unwrap_unionall(x);
jl_value_t *uy = jl_unwrap_unionall(y);
if ((x != ux || y != uy) && y != (jl_value_t*)jl_any_type && jl_is_datatype(ux) && jl_is_datatype(uy)) {
assert(ux);
jl_datatype_t *xd = (jl_datatype_t*)ux, *yd = (jl_datatype_t*)uy;
while (xd != NULL && xd != jl_any_type && xd->name != yd->name) {
xd = xd->super;
}
if (xd == jl_any_type && !jl_is_type_type(ux)) {
return 0;
}
}
// handle forall ("left") vars first
if (jl_is_unionall(x)) {
if (x == y && !(e->envidx < e->envsz))
return 1;
return subtype_unionall(y, (jl_unionall_t*)x, e, 0, param);
}
if (jl_is_unionall(y))