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use middle::def::*;
use middle::ty;
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<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);
}
fn outside_const<F>(&mut self, f: F) where
F: FnOnce(&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: &ast::Item) {
check_item(self, i);
}
fn visit_pat(&mut self, p: &ast::Pat) {
check_pat(self, p);
}
fn visit_expr(&mut self, ex: &ast::Expr) {
if 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_item(v: &mut CheckCrateVisitor, it: &ast::Item) {
match it.node {
ast::ItemStatic(_, _, ref ex) |
ast::ItemConst(_, ref ex) => {
v.inside_const(|v| v.visit_expr(&**ex));
}
ast::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: &ast::Pat) {
fn is_str(e: &ast::Expr) -> bool {
match e.node {
ast::ExprBox(_, ref expr) => {
match expr.node {
ast::ExprLit(ref lit) => ast_util::lit_is_str(&**lit),
_ => false,
}
}
_ => false,
}
}
match p.node {
ast::PatLit(ref a) => if !is_str(&**a) { v.inside_const(|v| v.visit_expr(&**a)); },
ast::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: &ast::Expr) -> bool {
if !v.in_const { return true }
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");
return false;
}
ast::ExprLit(ref lit) if ast_util::lit_is_str(&**lit) => {}
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(ref pth) => {
if !pth.segments.iter().all(|segment| segment.parameters.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().get(&e.id) {
Some(&DefStatic(..)) |
Some(&DefConst(..)) |
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?!");
}
}
}
ast::ExprCall(ref callee, _) => {
match v.tcx.def_map.borrow().get(&callee.id) {
Some(&DefStruct(..)) |
Some(&DefVariant(..)) => {}
_ => {
span_err!(v.tcx.sess, e.span, E0015,
"function calls in constants are limited to \
struct and enum constructors");
}
}
}
ast::ExprBlock(ref 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 span, _) => {
match span.node {
ast::DeclLocal(_) => block_span_err(span.span),
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?!")
}
}
}
match block.expr {
Some(ref expr) => { check_expr(v, &**expr); }
None => {}
}
}
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 {
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");
return false;
}
}
true
}