1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // This compiler pass detects constants that refer to themselves
14 use rustc::dep_graph::DepNode;
15 use rustc::hir::map as hir_map;
16 use rustc::session::{CompileResult, Session};
17 use rustc::hir::def::{Def, CtorKind};
18 use rustc::util::nodemap::{NodeMap, NodeSet};
22 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
25 struct CheckCrateVisitor<'a, 'hir: 'a> {
27 hir_map: &'a hir_map::Map<'hir>,
28 // `discriminant_map` is a cache that associates the `NodeId`s of local
29 // variant definitions with the discriminant expression that applies to
30 // each one. If the variant uses the default values (starting from `0`),
31 // then `None` is stored.
32 discriminant_map: NodeMap<Option<hir::BodyId>>,
33 detected_recursive_ids: NodeSet,
36 impl<'a, 'hir: 'a> Visitor<'hir> for CheckCrateVisitor<'a, 'hir> {
37 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'hir> {
38 NestedVisitorMap::None
41 fn visit_item(&mut self, it: &'hir hir::Item) {
44 hir::ItemConst(..) => {
45 let mut recursion_visitor = CheckItemRecursionVisitor::new(self);
46 recursion_visitor.visit_item(it);
48 hir::ItemEnum(ref enum_def, ref generics) => {
49 // We could process the whole enum, but handling the variants
50 // with discriminant expressions one by one gives more specific,
51 // less redundant output.
52 for variant in &enum_def.variants {
53 if let Some(_) = variant.node.disr_expr {
54 let mut recursion_visitor = CheckItemRecursionVisitor::new(self);
55 recursion_visitor.populate_enum_discriminants(enum_def);
56 recursion_visitor.visit_variant(variant, generics, it.id);
62 intravisit::walk_item(self, it)
65 fn visit_trait_item(&mut self, ti: &'hir hir::TraitItem) {
67 hir::TraitItemKind::Const(_, ref default) => {
68 if let Some(_) = *default {
69 let mut recursion_visitor = CheckItemRecursionVisitor::new(self);
70 recursion_visitor.visit_trait_item(ti);
75 intravisit::walk_trait_item(self, ti)
78 fn visit_impl_item(&mut self, ii: &'hir hir::ImplItem) {
80 hir::ImplItemKind::Const(..) => {
81 let mut recursion_visitor = CheckItemRecursionVisitor::new(self);
82 recursion_visitor.visit_impl_item(ii);
86 intravisit::walk_impl_item(self, ii)
90 pub fn check_crate<'hir>(sess: &Session, hir_map: &hir_map::Map<'hir>) -> CompileResult {
91 let _task = hir_map.dep_graph.in_task(DepNode::CheckStaticRecursion);
93 let mut visitor = CheckCrateVisitor {
96 discriminant_map: NodeMap(),
97 detected_recursive_ids: NodeSet(),
99 sess.track_errors(|| {
100 // FIXME(#37712) could use ItemLikeVisitor if trait items were item-like
101 hir_map.krate().visit_all_item_likes(&mut visitor.as_deep_visitor());
105 struct CheckItemRecursionVisitor<'a, 'b: 'a, 'hir: 'b> {
107 hir_map: &'b hir_map::Map<'hir>,
108 discriminant_map: &'a mut NodeMap<Option<hir::BodyId>>,
109 idstack: Vec<ast::NodeId>,
110 detected_recursive_ids: &'a mut NodeSet,
113 impl<'a, 'b: 'a, 'hir: 'b> CheckItemRecursionVisitor<'a, 'b, 'hir> {
114 fn new(v: &'a mut CheckCrateVisitor<'b, 'hir>) -> Self {
115 CheckItemRecursionVisitor {
118 discriminant_map: &mut v.discriminant_map,
120 detected_recursive_ids: &mut v.detected_recursive_ids,
123 fn with_item_id_pushed<F>(&mut self, id: ast::NodeId, f: F, span: Span)
124 where F: Fn(&mut Self)
126 if self.idstack.iter().any(|&x| x == id) {
127 if self.detected_recursive_ids.contains(&id) {
130 self.detected_recursive_ids.insert(id);
131 let any_static = self.idstack.iter().any(|&x| {
132 if let hir_map::NodeItem(item) = self.hir_map.get(x) {
133 if let hir::ItemStatic(..) = item.node {
143 struct_span_err!(self.sess, span, E0265, "recursive constant")
144 .span_label(span, &format!("recursion not allowed in constant"))
149 self.idstack.push(id);
153 // If a variant has an expression specifying its discriminant, then it needs
154 // to be checked just like a static or constant. However, if there are more
155 // variants with no explicitly specified discriminant, those variants will
156 // increment the same expression to get their values.
158 // So for every variant, we need to track whether there is an expression
159 // somewhere in the enum definition that controls its discriminant. We do
160 // this by starting from the end and searching backward.
161 fn populate_enum_discriminants(&mut self, enum_definition: &'hir hir::EnumDef) {
162 // Get the map, and return if we already processed this enum or if it
164 match enum_definition.variants.first() {
168 Some(variant) if self.discriminant_map.contains_key(&variant.node.data.id()) => {
174 // Go through all the variants.
175 let mut variant_stack: Vec<ast::NodeId> = Vec::new();
176 for variant in enum_definition.variants.iter().rev() {
177 variant_stack.push(variant.node.data.id());
178 // When we find an expression, every variant currently on the stack
179 // is affected by that expression.
180 if let Some(expr) = variant.node.disr_expr {
181 for id in &variant_stack {
182 self.discriminant_map.insert(*id, Some(expr));
184 variant_stack.clear()
187 // If we are at the top, that always starts at 0, so any variant on the
188 // stack has a default value and does not need to be checked.
189 for id in &variant_stack {
190 self.discriminant_map.insert(*id, None);
195 impl<'a, 'b: 'a, 'hir: 'b> Visitor<'hir> for CheckItemRecursionVisitor<'a, 'b, 'hir> {
196 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'hir> {
197 NestedVisitorMap::OnlyBodies(&self.hir_map)
199 fn visit_item(&mut self, it: &'hir hir::Item) {
200 self.with_item_id_pushed(it.id, |v| intravisit::walk_item(v, it), it.span);
203 fn visit_enum_def(&mut self,
204 enum_definition: &'hir hir::EnumDef,
205 generics: &'hir hir::Generics,
206 item_id: ast::NodeId,
208 self.populate_enum_discriminants(enum_definition);
209 intravisit::walk_enum_def(self, enum_definition, generics, item_id);
212 fn visit_variant(&mut self,
213 variant: &'hir hir::Variant,
214 _: &'hir hir::Generics,
216 let variant_id = variant.node.data.id();
217 let maybe_expr = *self.discriminant_map.get(&variant_id).unwrap_or_else(|| {
218 span_bug!(variant.span,
219 "`check_static_recursion` attempted to visit \
220 variant with unknown discriminant")
222 // If `maybe_expr` is `None`, that's because no discriminant is
223 // specified that affects this variant. Thus, no risk of recursion.
224 if let Some(expr) = maybe_expr {
225 let expr = &self.hir_map.body(expr).value;
226 self.with_item_id_pushed(expr.id, |v| intravisit::walk_expr(v, expr), expr.span);
230 fn visit_trait_item(&mut self, ti: &'hir hir::TraitItem) {
231 self.with_item_id_pushed(ti.id, |v| intravisit::walk_trait_item(v, ti), ti.span);
234 fn visit_impl_item(&mut self, ii: &'hir hir::ImplItem) {
235 self.with_item_id_pushed(ii.id, |v| intravisit::walk_impl_item(v, ii), ii.span);
238 fn visit_path(&mut self, path: &'hir hir::Path, _: ast::NodeId) {
240 Def::Static(def_id, _) |
241 Def::AssociatedConst(def_id) |
242 Def::Const(def_id) => {
243 if let Some(node_id) = self.hir_map.as_local_node_id(def_id) {
244 match self.hir_map.get(node_id) {
245 hir_map::NodeItem(item) => self.visit_item(item),
246 hir_map::NodeTraitItem(item) => self.visit_trait_item(item),
247 hir_map::NodeImplItem(item) => self.visit_impl_item(item),
248 hir_map::NodeForeignItem(_) => {}
251 "expected item, found {}",
252 self.hir_map.node_to_string(node_id));
257 // For variants, we only want to check expressions that
258 // affect the specific variant used, but we need to check
259 // the whole enum definition to see what expression that
260 // might be (if any).
261 Def::VariantCtor(variant_id, CtorKind::Const) => {
262 if let Some(variant_id) = self.hir_map.as_local_node_id(variant_id) {
263 let variant = self.hir_map.expect_variant(variant_id);
264 let enum_id = self.hir_map.get_parent(variant_id);
265 let enum_item = self.hir_map.expect_item(enum_id);
266 if let hir::ItemEnum(ref enum_def, ref generics) = enum_item.node {
267 self.populate_enum_discriminants(enum_def);
268 self.visit_variant(variant, generics, enum_id);
271 "`check_static_recursion` found \
272 non-enum in Def::VariantCtor");
278 intravisit::walk_path(self, path);