forked from rust-lang/rust
/
check_const.rs
213 lines (199 loc) · 7.43 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 middle::def::*;
use middle::ty;
use middle::typeck;
use util::ppaux;
use syntax::ast::*;
use syntax::ast_util;
use syntax::visit::Visitor;
use syntax::visit;
struct CheckCrateVisitor<'a, 'tcx: 'a> {
tcx: &'a ty::ctxt<'tcx>,
in_const: bool
}
impl<'a, 'tcx> CheckCrateVisitor<'a, 'tcx> {
fn with_const(&mut self, in_const: bool, f: |&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(&mut self, f: |&mut CheckCrateVisitor<'a, 'tcx>|) {
self.with_const(true, f);
}
fn outside_const(&mut self, f: |&mut CheckCrateVisitor<'a, 'tcx>|) {
self.with_const(false, f);
}
}
impl<'a, 'tcx, 'v> Visitor<'v> for CheckCrateVisitor<'a, 'tcx> {
fn visit_item(&mut self, i: &Item) {
check_item(self, i);
}
fn visit_pat(&mut self, p: &Pat) {
check_pat(self, p);
}
fn visit_expr(&mut self, ex: &Expr) {
check_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_item(v: &mut CheckCrateVisitor, it: &Item) {
match it.node {
ItemStatic(_, _, ref ex) => {
v.inside_const(|v| v.visit_expr(&**ex));
}
ItemEnum(ref enum_definition, _) => {
for var in (*enum_definition).variants.iter() {
for ex in var.node.disr_expr.iter() {
v.inside_const(|v| v.visit_expr(&**ex));
}
}
}
_ => v.outside_const(|v| visit::walk_item(v, it))
}
}
fn check_pat(v: &mut CheckCrateVisitor, p: &Pat) {
fn is_str(e: &Expr) -> bool {
match e.node {
ExprBox(_, ref expr) => {
match expr.node {
ExprLit(ref 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.inside_const(|v| v.visit_expr(&**a)); },
PatRange(ref a, ref b) => {
if !is_str(&**a) { v.inside_const(|v| v.visit_expr(&**a)); }
if !is_str(&**b) { v.inside_const(|v| v.visit_expr(&**b)); }
}
_ => v.outside_const(|v| visit::walk_pat(v, p))
}
}
fn check_expr(v: &mut CheckCrateVisitor, e: &Expr) {
if v.in_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(ref 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(ref callee, _) => {
match v.tcx.def_map.borrow().find(&callee.id) {
Some(&DefStruct(..)) |
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),
None => {}
}
}
ExprVec(_) |
ExprAddrOf(MutImmutable, _) |
ExprParen(..) |
ExprField(..) |
ExprTupField(..) |
ExprIndex(..) |
ExprTup(..) |
ExprRepeat(..) |
ExprStruct(..) => { }
ExprAddrOf(_, ref inner) => {
match inner.node {
// Mutable slices are allowed.
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");
return;
}
}
}
visit::walk_expr(v, e);
}