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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 middle::def::*;
use middle::ty;
use util::ppaux;
use syntax::ast;
use syntax::visit::{self, Visitor};
struct CheckCrateVisitor<'a, 'tcx: 'a> {
tcx: &'a ty::ctxt<'tcx>,
in_const: bool
}
impl<'a, 'tcx> CheckCrateVisitor<'a, 'tcx> {
fn with_const<F>(&mut self, in_const: bool, f: F) where
F: FnOnce(&mut CheckCrateVisitor<'a, 'tcx>),
{
let was_const = self.in_const;
self.in_const = in_const;
f(self);
self.in_const = was_const;
}
fn inside_const<F>(&mut self, f: F) where
F: FnOnce(&mut CheckCrateVisitor<'a, 'tcx>),
{
self.with_const(true, f);
}
}
impl<'a, 'tcx, 'v> Visitor<'v> for CheckCrateVisitor<'a, 'tcx> {
fn visit_item(&mut self, i: &ast::Item) {
match i.node {
ast::ItemStatic(_, _, ref ex) |
ast::ItemConst(_, ref ex) => {
self.inside_const(|v| v.visit_expr(&**ex));
}
ast::ItemEnum(ref enum_definition, _) => {
self.inside_const(|v| {
for var in enum_definition.variants.iter() {
if let Some(ref ex) = var.node.disr_expr {
v.visit_expr(&**ex);
}
}
});
}
_ => self.with_const(false, |v| visit::walk_item(v, i))
}
}
fn visit_pat(&mut self, p: &ast::Pat) {
let is_const = match p.node {
ast::PatLit(_) | ast::PatRange(..) => true,
_ => false
};
self.with_const(is_const, |v| visit::walk_pat(v, p))
}
fn visit_expr(&mut self, ex: &ast::Expr) {
if self.in_const {
check_expr(self, ex);
}
visit::walk_expr(self, ex);
}
}
pub fn check_crate(tcx: &ty::ctxt) {
visit::walk_crate(&mut CheckCrateVisitor { tcx: tcx, in_const: false },
tcx.map.krate());
tcx.sess.abort_if_errors();
}
fn check_expr(v: &mut CheckCrateVisitor, e: &ast::Expr) {
match e.node {
ast::ExprUnary(ast::UnDeref, _) => {}
ast::ExprUnary(ast::UnUniq, _) => {
span_err!(v.tcx.sess, e.span, E0010,
"cannot do allocations in constant expressions");
}
ast::ExprBinary(..) | ast::ExprUnary(..) => {
let method_call = ty::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");
}
}
ast::ExprLit(_) => {}
ast::ExprCast(ref from, _) => {
let toty = ty::expr_ty(v.tcx, e);
let fromty = ty::expr_ty(v.tcx, &**from);
let is_legal_cast =
ty::type_is_numeric(toty) ||
ty::type_is_unsafe_ptr(toty) ||
(ty::type_is_bare_fn(toty) && ty::type_is_bare_fn_item(fromty));
if !is_legal_cast {
span_err!(v.tcx.sess, e.span, E0012,
"can not cast to `{}` in a constant expression",
ppaux::ty_to_string(v.tcx, toty));
}
if ty::type_is_unsafe_ptr(fromty) && ty::type_is_numeric(toty) {
span_err!(v.tcx.sess, e.span, E0018,
"can not cast a pointer to an integer in a constant \
expression");
}
}
ast::ExprPath(_) => {
match v.tcx.def_map.borrow()[e.id] {
DefStatic(..) | DefConst(..) |
DefFn(..) | DefStaticMethod(..) | DefMethod(..) |
DefStruct(_) | DefVariant(_, _, _) => {}
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");
}
}
}
ast::ExprCall(ref callee, _) => {
match v.tcx.def_map.borrow()[callee.id] {
DefStruct(..) | DefVariant(..) => {} // OK.
_ => {
span_err!(v.tcx.sess, e.span, E0015,
"function calls in constants are limited to \
struct and enum constructors");
}
}
}
ast::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 {
ast::StmtDecl(ref decl, _) => {
match decl.node {
ast::DeclLocal(_) => block_span_err(decl.span),
// Item statements are allowed
ast::DeclItem(_) => {}
}
}
ast::StmtExpr(ref expr, _) => block_span_err(expr.span),
ast::StmtSemi(ref semi, _) => block_span_err(semi.span),
ast::StmtMac(..) => {
v.tcx.sess.span_bug(e.span, "unexpanded statement \
macro in const?!")
}
}
}
}
ast::ExprVec(_) |
ast::ExprAddrOf(ast::MutImmutable, _) |
ast::ExprParen(..) |
ast::ExprField(..) |
ast::ExprTupField(..) |
ast::ExprIndex(..) |
ast::ExprTup(..) |
ast::ExprRepeat(..) |
ast::ExprStruct(..) => {}
ast::ExprAddrOf(_, ref inner) => {
match inner.node {
// Mutable slices are allowed.
ast::ExprVec(_) => {}
_ => span_err!(v.tcx.sess, e.span, E0017,
"references in constants may only refer \
to immutable values")
}
}
_ => span_err!(v.tcx.sess, e.span, E0019,
"constant contains unimplemented expression type")
}
}
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