rust/src/librustc/middle/check_const.rs
2013-12-26 15:54:36 -08:00

278 lines
9.0 KiB
Rust

// Copyright 2012-2013 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 driver::session::Session;
use middle::resolve;
use middle::ty;
use middle::typeck;
use util::ppaux;
use std::cell::RefCell;
use syntax::ast::*;
use syntax::codemap;
use syntax::{ast_util, ast_map};
use syntax::visit::Visitor;
use syntax::visit;
struct CheckCrateVisitor {
sess: Session,
ast_map: ast_map::map,
def_map: resolve::DefMap,
method_map: typeck::method_map,
tcx: ty::ctxt,
}
impl Visitor<bool> for CheckCrateVisitor {
fn visit_item(&mut self, i:@item, env:bool) {
check_item(self, self.sess, self.ast_map, self.def_map, i, env);
}
fn visit_pat(&mut self, p:&Pat, env:bool) {
check_pat(self, p, env);
}
fn visit_expr(&mut self, ex:@Expr, env:bool) {
check_expr(self, self.sess, self.def_map, self.method_map,
self.tcx, ex, env);
}
}
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) {
let mut v = CheckCrateVisitor {
sess: sess,
ast_map: ast_map,
def_map: def_map,
method_map: method_map,
tcx: tcx,
};
visit::walk_crate(&mut v, crate, false);
sess.abort_if_errors();
}
pub fn check_item(v: &mut CheckCrateVisitor,
sess: Session,
ast_map: ast_map::map,
def_map: resolve::DefMap,
it: @item,
_is_const: bool) {
match it.node {
item_static(_, _, ex) => {
v.visit_expr(ex, true);
check_item_recursion(sess, ast_map, def_map, it);
}
item_enum(ref enum_definition, _) => {
for var in (*enum_definition).variants.iter() {
for ex in var.node.disr_expr.iter() {
v.visit_expr(*ex, true);
}
}
}
_ => visit::walk_item(v, it, false)
}
}
pub fn check_pat(v: &mut CheckCrateVisitor, p: &Pat, _is_const: bool) {
fn is_str(e: @Expr) -> bool {
match e.node {
ExprVstore(
@Expr { node: ExprLit(@codemap::Spanned {
node: lit_str(..),
..}),
.. },
ExprVstoreUniq
) => true,
_ => false
}
}
match p.node {
// Let through plain ~-string literals here
PatLit(a) => if !is_str(a) { v.visit_expr(a, true); },
PatRange(a, b) => {
if !is_str(a) { v.visit_expr(a, true); }
if !is_str(b) { v.visit_expr(b, true); }
}
_ => visit::walk_pat(v, p, false)
}
}
pub fn check_expr(v: &mut CheckCrateVisitor,
sess: Session,
def_map: resolve::DefMap,
method_map: typeck::method_map,
tcx: ty::ctxt,
e: @Expr,
is_const: bool) {
if is_const {
match e.node {
ExprUnary(_, UnDeref, _) => { }
ExprUnary(_, UnBox(_), _) | ExprUnary(_, UnUniq, _) => {
sess.span_err(e.span,
"cannot do allocations in constant expressions");
return;
}
ExprLit(@codemap::Spanned {node: lit_str(..), ..}) => { }
ExprBinary(..) | ExprUnary(..) => {
let method_map = method_map.borrow();
if method_map.get().contains_key(&e.id) {
sess.span_err(e.span, "user-defined operators are not \
allowed in constant expressions");
}
}
ExprLit(_) => (),
ExprCast(_, _) => {
let ety = ty::expr_ty(tcx, e);
if !ty::type_is_numeric(ety) && !ty::type_is_unsafe_ptr(ety) {
sess.span_err(e.span, ~"can not cast to `" +
ppaux::ty_to_str(tcx, ety) +
"` in a constant expression");
}
}
ExprPath(ref 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.segments.iter().all(|segment| segment.types.is_empty()) {
sess.span_err(
e.span, "paths in constants may only refer to \
items without type parameters");
}
match def_map.find(&e.id) {
Some(&DefStatic(..)) |
Some(&DefFn(_, _)) |
Some(&DefVariant(_, _, _)) |
Some(&DefStruct(_)) => { }
Some(&def) => {
debug!("(checking const) found bad def: {:?}", def);
sess.span_err(
e.span,
"paths in constants may only refer to \
constants or functions");
}
None => {
sess.span_bug(e.span, "unbound path in const?!");
}
}
}
ExprCall(callee, _, NoSugar) => {
match def_map.find(&callee.id) {
Some(&DefStruct(..)) => {} // OK.
Some(&DefVariant(..)) => {} // OK.
_ => {
sess.span_err(
e.span,
"function calls in constants are limited to \
struct and enum constructors");
}
}
}
ExprParen(e) => { check_expr(v, sess, def_map, method_map,
tcx, e, is_const); }
ExprVstore(_, ExprVstoreSlice) |
ExprVec(_, MutImmutable) |
ExprAddrOf(MutImmutable, _) |
ExprField(..) |
ExprIndex(..) |
ExprTup(..) |
ExprRepeat(..) |
ExprStruct(..) => { }
ExprAddrOf(..) => {
sess.span_err(
e.span,
"borrowed pointers in constants may only refer to \
immutable values");
},
ExprVstore(_, ExprVstoreUniq) |
ExprVstore(_, ExprVstoreBox) |
ExprVstore(_, ExprVstoreMutBox) => {
sess.span_err(e.span, "cannot allocate vectors in constant expressions")
},
_ => {
sess.span_err(e.span,
"constant contains unimplemented expression type");
return;
}
}
}
visit::walk_expr(v, e, is_const);
}
#[deriving(Clone)]
struct env {
root_it: @item,
sess: Session,
ast_map: ast_map::map,
def_map: resolve::DefMap,
idstack: @RefCell<~[NodeId]>,
}
struct CheckItemRecursionVisitor {
env: env,
}
// Make sure a const item doesn't recursively refer to itself
// 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) {
let env = env {
root_it: it,
sess: sess,
ast_map: ast_map,
def_map: def_map,
idstack: @RefCell::new(~[]),
};
let mut visitor = CheckItemRecursionVisitor { env: env };
visitor.visit_item(it, ());
}
impl Visitor<()> for CheckItemRecursionVisitor {
fn visit_item(&mut self, it: @item, _: ()) {
{
let mut idstack = self.env.idstack.borrow_mut();
if idstack.get().iter().any(|x| x == &(it.id)) {
self.env.sess.span_fatal(self.env.root_it.span,
"recursive constant");
}
idstack.get().push(it.id);
}
visit::walk_item(self, it, ());
{
let mut idstack = self.env.idstack.borrow_mut();
idstack.get().pop();
}
}
fn visit_expr(&mut self, e: @Expr, _: ()) {
match e.node {
ExprPath(..) => match self.env.def_map.find(&e.id) {
Some(&DefStatic(def_id, _)) if ast_util::is_local(def_id) =>
match self.env.ast_map.get_copy(&def_id.node) {
ast_map::node_item(it, _) => {
self.visit_item(it, ());
}
_ => fail!("const not bound to an item")
},
_ => ()
},
_ => ()
}
visit::walk_expr(self, e, ());
}
}