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::hir::map as hir_map;
15 use rustc::session::{CompileResult, Session};
16 use rustc::hir::def::{Def, CtorKind};
17 use rustc::util::nodemap::{NodeMap, NodeSet};
21 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
24 struct CheckCrateVisitor<'a, 'hir: 'a> {
26 hir_map: &'a hir_map::Map<'hir>,
27 // `discriminant_map` is a cache that associates the `NodeId`s of local
28 // variant definitions with the discriminant expression that applies to
29 // each one. If the variant uses the default values (starting from `0`),
30 // then `None` is stored.
31 discriminant_map: NodeMap<Option<hir::BodyId>>,
32 detected_recursive_ids: NodeSet,
35 impl<'a, 'hir: 'a> Visitor<'hir> for CheckCrateVisitor<'a, 'hir> {
36 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'hir> {
37 NestedVisitorMap::None
40 fn visit_item(&mut self, it: &'hir hir::Item) {
43 hir::ItemConst(..) => {
44 let mut recursion_visitor = CheckItemRecursionVisitor::new(self);
45 recursion_visitor.visit_item(it);
47 hir::ItemEnum(ref enum_def, ref generics) => {
48 // We could process the whole enum, but handling the variants
49 // with discriminant expressions one by one gives more specific,
50 // less redundant output.
51 for variant in &enum_def.variants {
52 if let Some(_) = variant.node.disr_expr {
53 let mut recursion_visitor = CheckItemRecursionVisitor::new(self);
54 recursion_visitor.populate_enum_discriminants(enum_def);
55 recursion_visitor.visit_variant(variant, generics, it.id);
61 intravisit::walk_item(self, it)
64 fn visit_trait_item(&mut self, ti: &'hir hir::TraitItem) {
66 hir::TraitItemKind::Const(_, ref default) => {
67 if let Some(_) = *default {
68 let mut recursion_visitor = CheckItemRecursionVisitor::new(self);
69 recursion_visitor.visit_trait_item(ti);
74 intravisit::walk_trait_item(self, ti)
77 fn visit_impl_item(&mut self, ii: &'hir hir::ImplItem) {
79 hir::ImplItemKind::Const(..) => {
80 let mut recursion_visitor = CheckItemRecursionVisitor::new(self);
81 recursion_visitor.visit_impl_item(ii);
85 intravisit::walk_impl_item(self, ii)
89 pub fn check_crate<'hir>(sess: &Session, hir_map: &hir_map::Map<'hir>) -> CompileResult {
90 let mut visitor = CheckCrateVisitor {
93 discriminant_map: NodeMap(),
94 detected_recursive_ids: NodeSet(),
96 sess.track_errors(|| {
97 // FIXME(#37712) could use ItemLikeVisitor if trait items were item-like
98 hir_map.krate().visit_all_item_likes(&mut visitor.as_deep_visitor());
102 struct CheckItemRecursionVisitor<'a, 'b: 'a, 'hir: 'b> {
104 hir_map: &'b hir_map::Map<'hir>,
105 discriminant_map: &'a mut NodeMap<Option<hir::BodyId>>,
106 idstack: Vec<ast::NodeId>,
107 detected_recursive_ids: &'a mut NodeSet,
110 impl<'a, 'b: 'a, 'hir: 'b> CheckItemRecursionVisitor<'a, 'b, 'hir> {
111 fn new(v: &'a mut CheckCrateVisitor<'b, 'hir>) -> Self {
112 CheckItemRecursionVisitor {
115 discriminant_map: &mut v.discriminant_map,
117 detected_recursive_ids: &mut v.detected_recursive_ids,
120 fn with_item_id_pushed<F>(&mut self, id: ast::NodeId, f: F, span: Span)
121 where F: Fn(&mut Self)
123 if self.idstack.iter().any(|&x| x == id) {
124 if self.detected_recursive_ids.contains(&id) {
127 self.detected_recursive_ids.insert(id);
128 let any_static = self.idstack.iter().any(|&x| {
129 if let hir_map::NodeItem(item) = self.hir_map.get(x) {
130 if let hir::ItemStatic(..) = item.node {
140 struct_span_err!(self.sess, span, E0265, "recursive constant")
141 .span_label(span, &format!("recursion not allowed in constant"))
146 self.idstack.push(id);
150 // If a variant has an expression specifying its discriminant, then it needs
151 // to be checked just like a static or constant. However, if there are more
152 // variants with no explicitly specified discriminant, those variants will
153 // increment the same expression to get their values.
155 // So for every variant, we need to track whether there is an expression
156 // somewhere in the enum definition that controls its discriminant. We do
157 // this by starting from the end and searching backward.
158 fn populate_enum_discriminants(&mut self, enum_definition: &'hir hir::EnumDef) {
159 // Get the map, and return if we already processed this enum or if it
161 match enum_definition.variants.first() {
165 Some(variant) if self.discriminant_map.contains_key(&variant.node.data.id()) => {
171 // Go through all the variants.
172 let mut variant_stack: Vec<ast::NodeId> = Vec::new();
173 for variant in enum_definition.variants.iter().rev() {
174 variant_stack.push(variant.node.data.id());
175 // When we find an expression, every variant currently on the stack
176 // is affected by that expression.
177 if let Some(expr) = variant.node.disr_expr {
178 for id in &variant_stack {
179 self.discriminant_map.insert(*id, Some(expr));
181 variant_stack.clear()
184 // If we are at the top, that always starts at 0, so any variant on the
185 // stack has a default value and does not need to be checked.
186 for id in &variant_stack {
187 self.discriminant_map.insert(*id, None);
192 impl<'a, 'b: 'a, 'hir: 'b> Visitor<'hir> for CheckItemRecursionVisitor<'a, 'b, 'hir> {
193 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'hir> {
194 NestedVisitorMap::OnlyBodies(&self.hir_map)
196 fn visit_item(&mut self, it: &'hir hir::Item) {
197 self.with_item_id_pushed(it.id, |v| intravisit::walk_item(v, it), it.span);
200 fn visit_enum_def(&mut self,
201 enum_definition: &'hir hir::EnumDef,
202 generics: &'hir hir::Generics,
203 item_id: ast::NodeId,
205 self.populate_enum_discriminants(enum_definition);
206 intravisit::walk_enum_def(self, enum_definition, generics, item_id);
209 fn visit_variant(&mut self,
210 variant: &'hir hir::Variant,
211 _: &'hir hir::Generics,
213 let variant_id = variant.node.data.id();
214 let maybe_expr = *self.discriminant_map.get(&variant_id).unwrap_or_else(|| {
215 span_bug!(variant.span,
216 "`check_static_recursion` attempted to visit \
217 variant with unknown discriminant")
219 // If `maybe_expr` is `None`, that's because no discriminant is
220 // specified that affects this variant. Thus, no risk of recursion.
221 if let Some(expr) = maybe_expr {
222 let expr = &self.hir_map.body(expr).value;
223 self.with_item_id_pushed(expr.id, |v| intravisit::walk_expr(v, expr), expr.span);
227 fn visit_trait_item(&mut self, ti: &'hir hir::TraitItem) {
228 self.with_item_id_pushed(ti.id, |v| intravisit::walk_trait_item(v, ti), ti.span);
231 fn visit_impl_item(&mut self, ii: &'hir hir::ImplItem) {
232 self.with_item_id_pushed(ii.id, |v| intravisit::walk_impl_item(v, ii), ii.span);
235 fn visit_path(&mut self, path: &'hir hir::Path, _: ast::NodeId) {
237 Def::Static(def_id, _) |
238 Def::AssociatedConst(def_id) |
239 Def::Const(def_id) => {
240 if let Some(node_id) = self.hir_map.as_local_node_id(def_id) {
241 match self.hir_map.get(node_id) {
242 hir_map::NodeItem(item) => self.visit_item(item),
243 hir_map::NodeTraitItem(item) => self.visit_trait_item(item),
244 hir_map::NodeImplItem(item) => self.visit_impl_item(item),
245 hir_map::NodeForeignItem(_) => {}
248 "expected item, found {}",
249 self.hir_map.node_to_string(node_id));
254 // For variants, we only want to check expressions that
255 // affect the specific variant used, but we need to check
256 // the whole enum definition to see what expression that
257 // might be (if any).
258 Def::VariantCtor(variant_id, CtorKind::Const) => {
259 if let Some(variant_id) = self.hir_map.as_local_node_id(variant_id) {
260 let variant = self.hir_map.expect_variant(variant_id);
261 let enum_id = self.hir_map.get_parent(variant_id);
262 let enum_item = self.hir_map.expect_item(enum_id);
263 if let hir::ItemEnum(ref enum_def, ref generics) = enum_item.node {
264 self.populate_enum_discriminants(enum_def);
265 self.visit_variant(variant, generics, enum_id);
268 "`check_static_recursion` found \
269 non-enum in Def::VariantCtor");
275 intravisit::walk_path(self, path);