/
check_const.rs
250 lines (233 loc) · 8.66 KB
/
check_const.rs
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// 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::def::*;
use middle::resolve;
use middle::ty;
use middle::typeck;
use util::ppaux;
use syntax::ast::*;
use syntax::{ast_util, ast_map};
use syntax::visit::Visitor;
use syntax::visit;
pub struct CheckCrateVisitor<'a> {
tcx: &'a ty::ctxt,
}
impl<'a> Visitor<bool> for CheckCrateVisitor<'a> {
fn visit_item(&mut self, i: &Item, env: bool) {
check_item(self, 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, ex, env);
}
}
pub fn check_crate(krate: &Crate, tcx: &ty::ctxt) {
visit::walk_crate(&mut CheckCrateVisitor { tcx: tcx }, krate, false);
tcx.sess.abort_if_errors();
}
fn check_item(v: &mut CheckCrateVisitor, it: &Item, _is_const: bool) {
match it.node {
ItemStatic(_, _, ex) => {
v.visit_expr(&*ex, true);
check_item_recursion(&v.tcx.sess, &v.tcx.map, &v.tcx.def_map, it);
}
ItemEnum(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)
}
}
fn check_pat(v: &mut CheckCrateVisitor, p: &Pat, _is_const: bool) {
fn is_str(e: &Expr) -> bool {
match e.node {
ExprVstore(expr, ExprVstoreUniq) => {
match expr.node {
ExprLit(lit) => ast_util::lit_is_str(lit),
_ => false,
}
}
_ => false,
}
}
match p.node {
// Let through plain ~-string literals here
PatLit(ref a) => if !is_str(&**a) { v.visit_expr(&**a, true); },
PatRange(ref a, ref 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)
}
}
fn check_expr(v: &mut CheckCrateVisitor, e: &Expr, is_const: bool) {
if is_const {
match e.node {
ExprUnary(UnDeref, _) => { }
ExprUnary(UnBox, _) | ExprUnary(UnUniq, _) => {
span_err!(v.tcx.sess, e.span, E0010, "cannot do allocations in constant expressions");
return;
}
ExprLit(lit) if ast_util::lit_is_str(lit) => {}
ExprBinary(..) | ExprUnary(..) => {
let method_call = typeck::MethodCall::expr(e.id);
if v.tcx.method_map.borrow().contains_key(&method_call) {
span_err!(v.tcx.sess, e.span, E0011,
"user-defined operators are not allowed in constant expressions");
}
}
ExprLit(_) => (),
ExprCast(_, _) => {
let ety = ty::expr_ty(v.tcx, e);
if !ty::type_is_numeric(ety) && !ty::type_is_unsafe_ptr(ety) {
span_err!(v.tcx.sess, e.span, E0012,
"can not cast to `{}` in a constant expression",
ppaux::ty_to_string(v.tcx, ety)
);
}
}
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()) {
span_err!(v.tcx.sess, e.span, E0013,
"paths in constants may only refer to items without type parameters");
}
match v.tcx.def_map.borrow().find(&e.id) {
Some(&DefStatic(..)) |
Some(&DefFn(_, _)) |
Some(&DefVariant(_, _, _)) |
Some(&DefStruct(_)) => { }
Some(&def) => {
debug!("(checking const) found bad def: {:?}", def);
span_err!(v.tcx.sess, e.span, E0014,
"paths in constants may only refer to constants or functions");
}
None => {
v.tcx.sess.span_bug(e.span, "unbound path in const?!");
}
}
}
ExprCall(callee, _) => {
match v.tcx.def_map.borrow().find(&callee.id) {
Some(&DefStruct(..)) => {} // OK.
Some(&DefVariant(..)) => {} // OK.
_ => {
span_err!(v.tcx.sess, e.span, E0015,
"function calls in constants are limited to struct and enum constructors");
}
}
}
ExprBlock(ref block) => {
// Check all statements in the block
for stmt in block.stmts.iter() {
let block_span_err = |span|
span_err!(v.tcx.sess, span, E0016,
"blocks in constants are limited to items and tail expressions");
match stmt.node {
StmtDecl(ref span, _) => {
match span.node {
DeclLocal(_) => block_span_err(span.span),
// Item statements are allowed
DeclItem(_) => {}
}
}
StmtExpr(ref expr, _) => block_span_err(expr.span),
StmtSemi(ref semi, _) => block_span_err(semi.span),
StmtMac(..) => v.tcx.sess.span_bug(e.span,
"unexpanded statement macro in const?!")
}
}
match block.expr {
Some(ref expr) => check_expr(v, &**expr, true),
None => {}
}
}
ExprVstore(_, ExprVstoreMutSlice) |
ExprVstore(_, ExprVstoreSlice) |
ExprVec(_) |
ExprAddrOf(MutImmutable, _) |
ExprParen(..) |
ExprField(..) |
ExprIndex(..) |
ExprTup(..) |
ExprRepeat(..) |
ExprStruct(..) => { }
ExprAddrOf(..) => {
span_err!(v.tcx.sess, e.span, E0017,
"references in constants may only refer to immutable values");
},
ExprVstore(_, ExprVstoreUniq) => {
span_err!(v.tcx.sess, e.span, E0018,
"cannot allocate vectors in constant expressions");
},
_ => {
span_err!(v.tcx.sess, e.span, E0019,
"constant contains unimplemented expression type");
return;
}
}
}
visit::walk_expr(v, e, is_const);
}
struct CheckItemRecursionVisitor<'a> {
root_it: &'a Item,
sess: &'a Session,
ast_map: &'a ast_map::Map,
def_map: &'a resolve::DefMap,
idstack: Vec<NodeId> }
// 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<'a>(sess: &'a Session,
ast_map: &'a ast_map::Map,
def_map: &'a resolve::DefMap,
it: &'a Item) {
let mut visitor = CheckItemRecursionVisitor {
root_it: it,
sess: sess,
ast_map: ast_map,
def_map: def_map,
idstack: Vec::new()
};
visitor.visit_item(it, ());
}
impl<'a> Visitor<()> for CheckItemRecursionVisitor<'a> {
fn visit_item(&mut self, it: &Item, _: ()) {
if self.idstack.iter().any(|x| x == &(it.id)) {
self.sess.span_fatal(self.root_it.span, "recursive constant");
}
self.idstack.push(it.id);
visit::walk_item(self, it, ());
self.idstack.pop();
}
fn visit_expr(&mut self, e: &Expr, _: ()) {
match e.node {
ExprPath(..) => {
match self.def_map.borrow().find(&e.id) {
Some(&DefStatic(def_id, _)) if
ast_util::is_local(def_id) => {
self.visit_item(&*self.ast_map.expect_item(def_id.node), ());
}
_ => ()
}
},
_ => ()
}
visit::walk_expr(self, e, ());
}
}