static bool method_application(pass_opt_t* opt, ast_t* ast, bool partial)
{
// TODO: use args to decide unbound type parameters
AST_GET_CHILDREN(ast, positional, namedargs, lhs);
if(!check_type_params(&lhs))
return false;
ast_t* type = ast_type(lhs);
if(is_typecheck_error(type))
return false;
AST_GET_CHILDREN(type, cap, typeparams, params, result);
if(!extend_positional_args(params, positional))
return false;
if(!apply_named_args(params, positional, namedargs))
return false;
bool incomplete = is_this_incomplete(&opt->check, ast);
if(!check_arg_types(opt, params, positional, incomplete, partial))
return false;
switch(ast_id(lhs))
{
case TK_FUNREF:
case TK_FUNAPP:
if(!check_receiver_cap(ast, incomplete))
return false;
break;
default: {}
}
return true;
}
bool expr_this(pass_opt_t* opt, ast_t* ast)
{
typecheck_t* t = &opt->check;
if(t->frame->def_arg != NULL)
{
ast_error(opt->check.errors, ast,
"can't reference 'this' in a default argument");
return false;
}
sym_status_t status;
ast_get(ast, stringtab("this"), &status);
if(status == SYM_CONSUMED)
{
ast_error(opt->check.errors, ast,
"can't use a consumed 'this' in an expression");
return false;
}
assert(status == SYM_NONE);
token_id cap = cap_for_this(t);
if(!cap_sendable(cap) && (t->frame->recover != NULL))
{
ast_t* parent = ast_parent(ast);
if(ast_id(parent) != TK_DOT)
cap = TK_TAG;
}
bool make_arrow = false;
if(cap == TK_BOX)
{
cap = TK_REF;
make_arrow = true;
}
ast_t* type = type_for_this(opt, ast, cap, TK_NONE, false);
if(make_arrow)
{
BUILD(arrow, ast, NODE(TK_ARROW, NODE(TK_THISTYPE) TREE(type)));
type = arrow;
}
// Get the nominal type, which may be the right side of an arrow type.
ast_t* nominal;
bool arrow;
if(ast_id(type) == TK_NOMINAL)
{
nominal = type;
arrow = false;
} else {
nominal = ast_childidx(type, 1);
arrow = true;
}
ast_t* typeargs = ast_childidx(nominal, 2);
ast_t* typearg = ast_child(typeargs);
while(typearg != NULL)
{
if(!expr_nominal(opt, &typearg))
{
ast_error(opt->check.errors, ast, "couldn't create a type for 'this'");
ast_free(type);
return false;
}
typearg = ast_sibling(typearg);
}
if(!expr_nominal(opt, &nominal))
{
ast_error(opt->check.errors, ast, "couldn't create a type for 'this'");
ast_free(type);
return false;
}
// Unless this is a field lookup, treat an incomplete `this` as a tag.
ast_t* parent = ast_parent(ast);
bool incomplete_ok = false;
if((ast_id(parent) == TK_DOT) && (ast_child(parent) == ast))
{
ast_t* right = ast_sibling(ast);
assert(ast_id(right) == TK_ID);
ast_t* find = lookup_try(opt, ast, nominal, ast_name(right));
if(find != NULL)
{
switch(ast_id(find))
{
case TK_FVAR:
case TK_FLET:
case TK_EMBED:
incomplete_ok = true;
break;
default: {}
}
}
}
if(!incomplete_ok && is_this_incomplete(t, ast))
{
ast_t* tag_type = set_cap_and_ephemeral(nominal, TK_TAG, TK_NONE);
ast_replace(&nominal, tag_type);
}
if(arrow)
type = ast_parent(nominal);
else
type = nominal;
ast_settype(ast, type);
return true;
}
bool expr_return(pass_opt_t* opt, ast_t* ast)
{
typecheck_t* t = &opt->check;
// return is always the last expression in a sequence
assert(ast_sibling(ast) == NULL);
if(ast_parent(ast) == t->frame->method_body)
{
ast_error(ast,
"use return only to exit early from a method, not at the end");
return false;
}
ast_t* type = ast_childidx(t->frame->method, 4);
ast_t* body = ast_child(ast);
if(!coerce_literals(&body, type, opt))
return false;
ast_t* body_type = ast_type(body);
if(is_typecheck_error(body_type))
return false;
if(is_control_type(body_type))
{
ast_error(body, "return value cannot be a control statement");
return false;
}
bool ok = true;
switch(ast_id(t->frame->method))
{
case TK_NEW:
if(is_this_incomplete(t, ast))
{
ast_error(ast,
"all fields must be defined before constructor returns");
ok = false;
}
break;
case TK_BE:
assert(is_none(body_type));
break;
default:
{
// The body type must be a subtype of the return type, and an alias of
// the body type must be a subtype of an alias of the return type.
ast_t* a_type = alias(type);
ast_t* a_body_type = alias(body_type);
errorframe_t info = NULL;
if(!is_subtype(body_type, type, &info) ||
!is_subtype(a_body_type, a_type, &info))
{
errorframe_t frame = NULL;
ast_t* last = ast_childlast(body);
ast_error_frame(&frame, last, "returned value isn't the return type");
ast_error_frame(&frame, type, "function return type: %s",
ast_print_type(type));
ast_error_frame(&frame, body_type, "returned value type: %s",
ast_print_type(body_type));
errorframe_append(&frame, &info);
errorframe_report(&frame);
ok = false;
}
ast_free_unattached(a_type);
ast_free_unattached(a_body_type);
}
}
ast_settype(ast, ast_from(ast, TK_RETURN));
ast_inheritflags(ast);
return ok;
}