static bool is_nominal_sub_interface(ast_t* sub, ast_t* super)
{
ast_t* sub_def = (ast_t*)ast_data(sub);
ast_t* super_def = (ast_t*)ast_data(super);
ast_t* sub_typeargs = ast_childidx(sub, 2);
ast_t* super_typeargs = ast_childidx(super, 2);
ast_t* sub_typeparams = ast_childidx(sub_def, 1);
ast_t* super_typeparams = ast_childidx(super_def, 1);
ast_t* super_members = ast_childidx(super_def, 4);
ast_t* super_member = ast_child(super_members);
while(super_member != NULL)
{
ast_t* super_member_id = ast_childidx(super_member, 1);
ast_t* sub_member = ast_get(sub_def, ast_name(super_member_id), NULL);
if(sub_member == NULL)
return false;
ast_t* r_sub_member = reify(sub_typeargs, sub_member, sub_typeparams,
sub_typeargs);
if(r_sub_member== NULL)
return false;
ast_t* r_super_member = reify(super_typeargs, super_member,
super_typeparams, super_typeargs);
if(r_super_member == NULL)
{
ast_free_unattached(r_sub_member);
return false;
}
bool ok = is_fun_sub_fun(r_sub_member, r_super_member, sub, super);
ast_free_unattached(r_sub_member);
ast_free_unattached(r_super_member);
if(!ok)
return false;
super_member = ast_sibling(super_member);
}
return true;
}
bool is_subtype(ast_t* sub, ast_t* super)
{
assert(sub != NULL);
assert(super != NULL);
if(ast_id(super) == TK_DONTCARE)
return true;
switch(ast_id(sub))
{
case TK_UNIONTYPE:
return is_union_subtype(sub, super);
case TK_ISECTTYPE:
return is_isect_subtype(sub, super);
case TK_TUPLETYPE:
return is_tuple_subtype(sub, super);
case TK_NOMINAL:
return is_nominal_subtype(sub, super);
case TK_TYPEPARAMREF:
return is_typeparam_subtype(sub, super);
case TK_ARROW:
return is_arrow_subtype(sub, super);
case TK_FUNTYPE:
case TK_INFERTYPE:
case TK_ERRORTYPE:
return false;
case TK_NEW:
case TK_BE:
case TK_FUN:
return is_fun_sub_fun(sub, super, NULL, NULL);
default: {}
}
assert(0);
return false;
}
static bool is_nominal_sub_interface(ast_t* sub, ast_t* super,
errorframe_t* errors)
{
// implements(N, I)
// k <: k'
// ---
// N k <: I k
ast_t* sub_def = (ast_t*)ast_data(sub);
ast_t* super_def = (ast_t*)ast_data(super);
// Add an assumption: sub <: super
if(push_assume(sub, super))
return true;
bool ret = true;
// A struct has no descriptor, so can't be a subtype of an interface.
if(ast_id(sub_def) == TK_STRUCT)
{
ret = false;
if(errors != NULL)
{
ast_error_frame(errors, sub,
"%s is not a subtype of %s: a struct can't be a subtype of an "
"interface",
ast_print_type(sub), ast_print_type(super));
}
}
if(!is_sub_cap_and_eph(sub, super, errors))
ret = false;
ast_t* sub_typeargs = ast_childidx(sub, 2);
ast_t* sub_typeparams = ast_childidx(sub_def, 1);
ast_t* super_typeargs = ast_childidx(super, 2);
ast_t* super_typeparams = ast_childidx(super_def, 1);
ast_t* super_members = ast_childidx(super_def, 4);
ast_t* super_member = ast_child(super_members);
while(super_member != NULL)
{
ast_t* super_member_id = ast_childidx(super_member, 1);
ast_t* sub_member = ast_get(sub_def, ast_name(super_member_id), NULL);
// If we don't provide a method, we aren't a subtype.
if(sub_member == NULL)
{
if(errors != NULL)
{
ast_error_frame(errors, sub,
"%s is not a subtype of %s: it has no method %s",
ast_print_type(sub), ast_print_type(super),
ast_name(super_member_id));
}
ret = false;
super_member = ast_sibling(super_member);
continue;
}
// Reify the method on the subtype.
ast_t* r_sub_member = reify(sub_member, sub_typeparams, sub_typeargs);
assert(r_sub_member != NULL);
// Reify the method on the supertype.
ast_t* r_super_member = reify(super_member, super_typeparams,
super_typeargs);
assert(r_super_member != NULL);
// Check the reified methods.
bool ok = is_fun_sub_fun(r_sub_member, r_super_member, errors);
ast_free_unattached(r_sub_member);
ast_free_unattached(r_super_member);
if(!ok)
{
ret = false;
if(errors != NULL)
{
ast_error_frame(errors, sub_member,
"%s is not a subtype of %s: method %s has an incompatible signature",
ast_print_type(sub), ast_print_type(super),
ast_name(super_member_id));
}
}
super_member = ast_sibling(super_member);
}
pop_assume();
return ret;
}
