rust/src/librustc/middle/check_const.rs

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// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use core::prelude::*;
use driver::session::Session;
use middle::resolve;
use middle::ty;
use middle::typeck;
use util::ppaux;
use core::dvec::DVec;
use core::option;
use std::oldmap::HashMap;
use syntax::ast::*;
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use syntax::codemap;
use syntax::{visit, ast_util, ast_map};
pub fn check_crate(sess: Session,
crate: @crate,
ast_map: ast_map::map,
def_map: resolve::DefMap,
method_map: typeck::method_map,
tcx: ty::ctxt) {
visit::visit_crate(*crate, false, visit::mk_vt(@visit::Visitor {
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visit_item: |a,b,c| check_item(sess, ast_map, def_map, a, b, c),
visit_pat: check_pat,
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visit_expr: |a,b,c|
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check_expr(sess, def_map, method_map, tcx, a, b, c),
.. *visit::default_visitor()
}));
sess.abort_if_errors();
}
pub fn check_item(sess: Session,
ast_map: ast_map::map,
def_map: resolve::DefMap,
it: @item,
&&_is_const: bool,
v: visit::vt<bool>) {
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match it.node {
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item_const(_, ex) => {
(v.visit_expr)(ex, true, v);
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check_item_recursion(sess, ast_map, def_map, it);
}
item_enum(ref enum_definition, _) => {
for (*enum_definition).variants.each |var| {
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do option::iter(&var.node.disr_expr) |ex| {
(v.visit_expr)(*ex, true, v);
}
}
}
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_ => visit::visit_item(it, false, v)
}
}
pub fn check_pat(p: @pat, &&_is_const: bool, v: visit::vt<bool>) {
fn is_str(e: @expr) -> bool {
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match e.node {
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expr_vstore(
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@expr { node: expr_lit(@codemap::spanned {
node: lit_str(_),
_}),
_ },
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expr_vstore_uniq
) => true,
_ => false
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}
}
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match p.node {
// Let through plain ~-string literals here
pat_lit(a) => if !is_str(a) { (v.visit_expr)(a, true, v); },
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pat_range(a, b) => {
if !is_str(a) { (v.visit_expr)(a, true, v); }
if !is_str(b) { (v.visit_expr)(b, true, v); }
}
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_ => visit::visit_pat(p, false, v)
}
}
pub fn check_expr(sess: Session,
def_map: resolve::DefMap,
method_map: typeck::method_map,
tcx: ty::ctxt,
e: @expr,
&&is_const: bool,
v: visit::vt<bool>) {
if is_const {
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match e.node {
expr_unary(box(_), _) | expr_unary(uniq(_), _) |
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expr_unary(deref, _) => {
sess.span_err(e.span,
~"disallowed operator in constant expression");
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return;
}
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expr_lit(@codemap::spanned {node: lit_str(_), _}) => { }
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expr_binary(_, _, _) | expr_unary(_, _) => {
if method_map.contains_key(&e.id) {
sess.span_err(e.span, ~"user-defined operators are not \
allowed in constant expressions");
}
}
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expr_lit(_) => (),
expr_cast(_, _) => {
let ety = ty::expr_ty(tcx, e);
if !ty::type_is_numeric(ety) {
sess.span_err(e.span, ~"can not cast to `" +
ppaux::ty_to_str(tcx, ety) +
~"` in a constant expression");
}
}
expr_path(pth) => {
// NB: In the future you might wish to relax this slightly
// to handle on-demand instantiation of functions via
// foo::<bar> in a const. Currently that is only done on
// a path in trans::callee that only works in block contexts.
if pth.types.len() != 0 {
sess.span_err(
e.span, ~"paths in constants may only refer to \
items without type parameters");
}
match def_map.find(&e.id) {
Some(def_variant(_, _)) |
Some(def_struct(_)) => { }
Some(def_const(def_id)) |
Some(def_fn(def_id, _)) => {
if !ast_util::is_local(def_id) {
sess.span_err(
e.span, ~"paths in constants may only refer to \
crate-local constants or functions");
}
}
Some(def) => {
debug!("(checking const) found bad def: %?", def);
sess.span_err(
e.span,
fmt!("paths in constants may only refer to \
constants or functions"));
}
None => {
sess.span_bug(e.span, ~"unbound path in const?!");
}
}
}
expr_call(callee, _, NoSugar) => {
match def_map.find(&callee.id) {
Some(def_struct(*)) => {} // OK.
Some(def_variant(*)) => {} // OK.
_ => {
sess.span_err(
e.span,
~"function calls in constants are limited to \
struct and enum constructors");
}
}
}
expr_paren(e) => { check_expr(sess, def_map, method_map,
tcx, e, is_const, v); }
expr_vstore(_, expr_vstore_slice) |
expr_vstore(_, expr_vstore_fixed(_)) |
expr_vec(_, m_imm) |
expr_addr_of(m_imm, _) |
expr_field(*) |
expr_index(*) |
expr_tup(*) |
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expr_struct(*) |
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expr_rec(*) => { }
expr_addr_of(*) => {
sess.span_err(
e.span,
~"borrowed pointers in constants may only refer to \
immutable values");
}
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_ => {
sess.span_err(e.span,
~"constant contains unimplemented expression type");
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return;
}
}
}
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match e.node {
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expr_lit(@codemap::spanned {node: lit_int(v, t), _}) => {
if t != ty_char {
if (v as u64) > ast_util::int_ty_max(
if t == ty_i { sess.targ_cfg.int_type } else { t }) {
sess.span_err(e.span, ~"literal out of range for its type");
}
}
}
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expr_lit(@codemap::spanned {node: lit_uint(v, t), _}) => {
if v > ast_util::uint_ty_max(
if t == ty_u { sess.targ_cfg.uint_type } else { t }) {
sess.span_err(e.span, ~"literal out of range for its type");
}
}
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_ => ()
}
visit::visit_expr(e, is_const, v);
}
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// Make sure a const item doesn't recursively refer to itself
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// FIXME: Should use the dependency graph when it's available (#1356)
pub fn check_item_recursion(sess: Session,
ast_map: ast_map::map,
def_map: resolve::DefMap,
it: @item) {
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type env = {
root_it: @item,
sess: Session,
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ast_map: ast_map::map,
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def_map: resolve::DefMap,
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idstack: @DVec<node_id>,
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};
let env = {
root_it: it,
sess: sess,
ast_map: ast_map,
def_map: def_map,
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idstack: @DVec()
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};
let visitor = visit::mk_vt(@visit::Visitor {
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visit_item: visit_item,
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visit_expr: visit_expr,
.. *visit::default_visitor()
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});
(visitor.visit_item)(it, env, visitor);
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fn visit_item(it: @item, &&env: env, v: visit::vt<env>) {
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if (*env.idstack).contains(&(it.id)) {
env.sess.span_fatal(env.root_it.span, ~"recursive constant");
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}
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(*env.idstack).push(it.id);
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visit::visit_item(it, env, v);
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(*env.idstack).pop();
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}
fn visit_expr(e: @expr, &&env: env, v: visit::vt<env>) {
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match e.node {
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expr_path(*) => {
match env.def_map.find(&e.id) {
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Some(def_const(def_id)) => {
match env.ast_map.get(&def_id.node) {
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ast_map::node_item(it, _) => {
(v.visit_item)(it, env, v);
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}
_ => die!(~"const not bound to an item")
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}
}
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_ => ()
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}
}
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_ => ()
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}
visit::visit_expr(e, env, v);
}
}
// Local Variables:
// mode: rust
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// End: