bool is_lvalue(const exprt &expr)
{
if(expr.id()==ID_index)
return is_lvalue(to_index_expr(expr).op0());
else if(expr.id()==ID_member)
return is_lvalue(to_member_expr(expr).op0());
else if(expr.id()==ID_dereference)
return true;
else if(expr.id()==ID_symbol)
return true;
else
return false;
}
exprt make_va_list(const exprt &expr)
{
// we first strip any typecast
if(expr.id()==ID_typecast)
return make_va_list(to_typecast_expr(expr).op());
// if it's an address of an lvalue, we take that
if(expr.id()==ID_address_of &&
expr.operands().size()==1 &&
is_lvalue(expr.op0()))
return expr.op0();
return expr;
}
bool is_xvalue() const noexcept
{ return !is_lvalue(); }
T copy_or_move() const
{
if(is_lvalue()) return *lvalue;
else return std::move(*xvalue);
}
static bool is_lvalue(typecheck_t* t, ast_t* ast, bool need_value)
{
switch(ast_id(ast))
{
case TK_DONTCARE:
// Can only assign to it if we don't need the value.
return !need_value;
case TK_VAR:
case TK_LET:
return assign_id(t, ast_child(ast), ast_id(ast) == TK_LET, need_value);
case TK_VARREF:
{
ast_t* id = ast_child(ast);
return assign_id(t, id, false, need_value);
}
case TK_LETREF:
{
ast_error(ast, "can't assign to a let local");
return false;
}
case TK_FVARREF:
{
AST_GET_CHILDREN(ast, left, right);
if(ast_id(left) == TK_THIS)
return assign_id(t, right, false, need_value);
return true;
}
case TK_FLETREF:
{
AST_GET_CHILDREN(ast, left, right);
if(ast_id(left) != TK_THIS)
{
ast_error(ast, "can't assign to a let field");
return false;
}
if(t->frame->loop_body != NULL)
{
ast_error(ast, "can't assign to a let field in a loop");
return false;
}
return assign_id(t, right, true, need_value);
}
case TK_EMBEDREF:
{
AST_GET_CHILDREN(ast, left, right);
if(ast_id(left) != TK_THIS)
{
ast_error(ast, "can't assign to an embed field");
return false;
}
if(t->frame->loop_body != NULL)
{
ast_error(ast, "can't assign to an embed field in a loop");
return false;
}
return assign_id(t, right, true, need_value);
}
case TK_TUPLE:
{
// A tuple is an lvalue if every component expression is an lvalue.
ast_t* child = ast_child(ast);
while(child != NULL)
{
if(!is_lvalue(t, child, need_value))
return false;
child = ast_sibling(child);
}
return true;
}
case TK_SEQ:
{
// A sequence is an lvalue if it has a single child that is an lvalue.
// This is used because the components of a tuple are sequences.
ast_t* child = ast_child(ast);
if(ast_sibling(child) != NULL)
return false;
return is_lvalue(t, child, need_value);
}
default: {}
}
return false;
}
bool expr_assign(pass_opt_t* opt, ast_t* ast)
{
// Left and right are swapped in the AST to make sure we type check the
// right side before the left. Fetch them in the opposite order.
assert(ast != NULL);
AST_GET_CHILDREN(ast, right, left);
ast_t* l_type = ast_type(left);
if(!is_lvalue(&opt->check, left, is_result_needed(ast)))
{
ast_error(ast, "left side must be something that can be assigned to");
return false;
}
assert(l_type != NULL);
if(!coerce_literals(&right, l_type, opt))
return false;
ast_t* r_type = ast_type(right);
if(is_typecheck_error(r_type))
return false;
if(!infer_locals(left, r_type))
return false;
// Inferring locals may have changed the left type.
l_type = ast_type(left);
// Assignment is based on the alias of the right hand side.
ast_t* a_type = alias(r_type);
if(!is_subtype(a_type, l_type))
{
ast_error(ast, "right side must be a subtype of left side");
ast_error(a_type, "right side type: %s", ast_print_type(a_type));
ast_error(l_type, "left side type: %s", ast_print_type(l_type));
ast_free_unattached(a_type);
return false;
}
if((ast_id(left) == TK_TUPLE) && (ast_id(a_type) != TK_TUPLETYPE))
{
switch(ast_id(a_type))
{
case TK_UNIONTYPE:
ast_error(ast,
"can't destructure a union using assignment, use pattern matching "
"instead");
break;
case TK_ISECTTYPE:
ast_error(ast,
"can't destructure an intersection using assignment, use pattern "
"matching instead");
break;
default:
assert(0);
break;
}
ast_error(a_type, "right side type: %s", ast_print_type(a_type));
ast_free_unattached(a_type);
return false;
}
bool ok_safe = safe_to_write(left, a_type);
if(!ok_safe)
{
if(ast_id(left) == TK_FVARREF && ast_child(left) != NULL &&
ast_id(ast_child(left)) == TK_THIS)
{
// We are writing to a field in this
ast_t* fn = ast_nearest(left, TK_FUN);
if(fn != NULL)
{
ast_t* iso = ast_child(fn);
assert(iso != NULL);
token_id iso_id = ast_id(iso);
if(iso_id == TK_BOX || iso_id == TK_VAL || iso_id == TK_TAG)
{
ast_error(ast, "cannot write to a field in a %s function",
lexer_print(iso_id));
ast_free_unattached(a_type);
return false;
}
}
}
ast_error(ast, "not safe to write right side to left side");
ast_error(a_type, "right side type: %s", ast_print_type(a_type));
ast_free_unattached(a_type);
return false;
}
ast_free_unattached(a_type);
// If it's an embedded field, check for a constructor result.
if(ast_id(left) == TK_EMBEDREF)
{
if((ast_id(right) != TK_CALL) ||
(ast_id(ast_childidx(right, 2)) != TK_NEWREF))
{
ast_error(ast, "an embedded field must be assigned using a constructor");
return false;
}
}
ast_settype(ast, consume_type(l_type, TK_NONE));
ast_inheritflags(ast);
return true;
}
bool expr_assign(pass_opt_t* opt, ast_t* ast)
{
// Left and right are swapped in the AST to make sure we type check the
// right side before the left. Fetch them in the opposite order.
assert(ast != NULL);
AST_GET_CHILDREN(ast, right, left);
ast_t* l_type = ast_type(left);
if(l_type == NULL || !is_lvalue(opt, left, is_result_needed(ast)))
{
ast_error(opt->check.errors, ast,
"left side must be something that can be assigned to");
return false;
}
if(!coerce_literals(&right, l_type, opt))
return false;
ast_t* r_type = ast_type(right);
if(is_typecheck_error(r_type))
return false;
if(is_control_type(r_type))
{
ast_error(opt->check.errors, ast,
"the right hand side does not return a value");
return false;
}
if(!infer_locals(opt, left, r_type))
return false;
// Inferring locals may have changed the left type.
l_type = ast_type(left);
// Assignment is based on the alias of the right hand side.
ast_t* a_type = alias(r_type);
errorframe_t info = NULL;
if(!is_subtype(a_type, l_type, &info, opt))
{
errorframe_t frame = NULL;
ast_error_frame(&frame, ast, "right side must be a subtype of left side");
errorframe_append(&frame, &info);
errorframe_report(&frame, opt->check.errors);
ast_free_unattached(a_type);
return false;
}
if((ast_id(left) == TK_TUPLE) && (ast_id(a_type) != TK_TUPLETYPE))
{
switch(ast_id(a_type))
{
case TK_UNIONTYPE:
ast_error(opt->check.errors, ast,
"can't destructure a union using assignment, use pattern matching "
"instead");
break;
case TK_ISECTTYPE:
ast_error(opt->check.errors, ast,
"can't destructure an intersection using assignment, use pattern "
"matching instead");
break;
default:
assert(0);
break;
}
ast_free_unattached(a_type);
return false;
}
bool ok_safe = safe_to_write(left, a_type);
if(!ok_safe)
{
if(ast_id(left) == TK_FVARREF && ast_child(left) != NULL &&
ast_id(ast_child(left)) == TK_THIS)
{
// We are writing to a field in this
ast_t* fn = ast_nearest(left, TK_FUN);
if(fn != NULL)
{
ast_t* iso = ast_child(fn);
assert(iso != NULL);
token_id iso_id = ast_id(iso);
if(iso_id == TK_BOX || iso_id == TK_VAL || iso_id == TK_TAG)
{
ast_error(opt->check.errors, ast,
"cannot write to a field in a %s function. If you are trying to "
"change state in a function use fun ref",
lexer_print(iso_id));
ast_free_unattached(a_type);
return false;
}
}
}
ast_error(opt->check.errors, ast,
"not safe to write right side to left side");
ast_error_continue(opt->check.errors, a_type, "right side type: %s",
ast_print_type(a_type));
ast_free_unattached(a_type);
return false;
}
ast_free_unattached(a_type);
if(!check_embed_construction(opt, left, right))
return false;
ast_settype(ast, consume_type(l_type, TK_NONE));
return true;
}
static void emit_expr(struct q *q, const struct node *node)
{
switch (node->tok) {
case '.':
if (node->left->tok == TOK_IDENT)
emit_byte(q, OP_PUSHNS);
emit_expr(q, node->left);
emit_expr(q, node->right);
emit_byte(q, OP_GET);
break;
case '%':
case '*':
case '/':
case '+':
case '-':
emit_expr(q, node->left);
emit_expr(q, node->right);
emit_byte(q, OP_MATH);
emit_byte(q, node->tok);
break;
case '=':
emit_expr(q, node->right);
emit_expr(q, node->left);
if (node->left->tok != TOK_IDENT &&
node->left->tok != '.' && node->left->tok != '=')
die(q, "%s: %d: %s", serr,
node->line_no, "invalid assignment");
emit_byte(q, OP_SET);
break;
case ',':
emit_expr(q, node->left);
emit_expr(q, node->right);
die(q, "%s: %d: %s", serr, node->line_no, "use ';', not ','");
break;
case '(':
emit_function_call(q, node);
break;
case TOK_NIL:
emit_byte(q, OP_PUSH);
emit_byte(q, TYPE_NIL);
break;
case TOK_IDENT:
/*
* Identifier could be either rvalue or lvalue:
* "foo.bar = baz = x.y;"
* Lvalues: bar, baz
* Rvalues: foo, x, y
* Lvalue is a key, for namespace insert.
* Rvalue is always a key for namespace lookup.
*/
if (node->parent == NULL || node->parent->tok != '.')
emit_byte(q, OP_PUSHNS);
emit_ident(q, node);
if (!is_lvalue(node) && !(node->parent != NULL &&
node->parent->tok == '.' && is_lvalue(node->parent)))
emit_byte(q, OP_GET);
break;
case TOK_STR:
emit_string_constant(q, node);
break;
case TOK_NUM:
emit_num(q, strtod(node->vec.ptr, NULL));
break;
case '[':
emit_byte(q, OP_NEWMAP);
assert(node->right != NULL);
if (node->right->tok != TOK_NIL) {
emit_hash_definition(q, node->right, 0);
emit_byte(q, OP_POP);
}
break;
default:
die(q, "%s: %d: %s [%d]", serr, node->line_no,
"internal parser error", node->tok);
break;
}
}
