1 use crate::util::{check_builtin_macro_attribute, warn_on_duplicate_attribute};
4 use rustc_ast::mut_visit::MutVisitor;
6 use rustc_ast::visit::Visitor;
8 use rustc_ast::{mut_visit, visit};
9 use rustc_ast::{Attribute, HasAttrs, HasTokens};
10 use rustc_expand::base::{Annotatable, ExtCtxt};
11 use rustc_expand::config::StripUnconfigured;
12 use rustc_expand::configure;
13 use rustc_feature::Features;
14 use rustc_parse::parser::{ForceCollect, Parser};
15 use rustc_session::Session;
16 use rustc_span::symbol::sym;
18 use smallvec::SmallVec;
21 ecx: &mut ExtCtxt<'_>,
23 meta_item: &ast::MetaItem,
24 annotatable: Annotatable,
25 ) -> Vec<Annotatable> {
26 check_builtin_macro_attribute(ecx, meta_item, sym::cfg_eval);
27 warn_on_duplicate_attribute(&ecx, &annotatable, sym::cfg_eval);
28 vec![cfg_eval(ecx.sess, ecx.ecfg.features, annotatable, ecx.current_expansion.lint_node_id)]
31 pub(crate) fn cfg_eval(
33 features: Option<&Features>,
34 annotatable: Annotatable,
37 CfgEval { cfg: &mut StripUnconfigured { sess, features, config_tokens: true, lint_node_id } }
38 .configure_annotatable(annotatable)
39 // Since the item itself has already been configured by the `InvocationCollector`,
40 // we know that fold result vector will contain exactly one element.
44 struct CfgEval<'a, 'b> {
45 cfg: &'a mut StripUnconfigured<'b>,
48 fn flat_map_annotatable(
49 vis: &mut impl MutVisitor,
50 annotatable: Annotatable,
51 ) -> Option<Annotatable> {
53 Annotatable::Item(item) => vis.flat_map_item(item).pop().map(Annotatable::Item),
54 Annotatable::TraitItem(item) => {
55 vis.flat_map_trait_item(item).pop().map(Annotatable::TraitItem)
57 Annotatable::ImplItem(item) => {
58 vis.flat_map_impl_item(item).pop().map(Annotatable::ImplItem)
60 Annotatable::ForeignItem(item) => {
61 vis.flat_map_foreign_item(item).pop().map(Annotatable::ForeignItem)
63 Annotatable::Stmt(stmt) => {
64 vis.flat_map_stmt(stmt.into_inner()).pop().map(P).map(Annotatable::Stmt)
66 Annotatable::Expr(mut expr) => {
67 vis.visit_expr(&mut expr);
68 Some(Annotatable::Expr(expr))
70 Annotatable::Arm(arm) => vis.flat_map_arm(arm).pop().map(Annotatable::Arm),
71 Annotatable::ExprField(field) => {
72 vis.flat_map_expr_field(field).pop().map(Annotatable::ExprField)
74 Annotatable::PatField(fp) => vis.flat_map_pat_field(fp).pop().map(Annotatable::PatField),
75 Annotatable::GenericParam(param) => {
76 vis.flat_map_generic_param(param).pop().map(Annotatable::GenericParam)
78 Annotatable::Param(param) => vis.flat_map_param(param).pop().map(Annotatable::Param),
79 Annotatable::FieldDef(sf) => vis.flat_map_field_def(sf).pop().map(Annotatable::FieldDef),
80 Annotatable::Variant(v) => vis.flat_map_variant(v).pop().map(Annotatable::Variant),
81 Annotatable::Crate(mut krate) => {
82 vis.visit_crate(&mut krate);
83 Some(Annotatable::Crate(krate))
89 has_cfg_or_cfg_attr: bool,
93 fn has_cfg_or_cfg_attr(annotatable: &Annotatable) -> bool {
94 let mut finder = CfgFinder { has_cfg_or_cfg_attr: false };
96 Annotatable::Item(item) => finder.visit_item(&item),
97 Annotatable::TraitItem(item) => finder.visit_assoc_item(&item, visit::AssocCtxt::Trait),
98 Annotatable::ImplItem(item) => finder.visit_assoc_item(&item, visit::AssocCtxt::Impl),
99 Annotatable::ForeignItem(item) => finder.visit_foreign_item(&item),
100 Annotatable::Stmt(stmt) => finder.visit_stmt(&stmt),
101 Annotatable::Expr(expr) => finder.visit_expr(&expr),
102 Annotatable::Arm(arm) => finder.visit_arm(&arm),
103 Annotatable::ExprField(field) => finder.visit_expr_field(&field),
104 Annotatable::PatField(field) => finder.visit_pat_field(&field),
105 Annotatable::GenericParam(param) => finder.visit_generic_param(¶m),
106 Annotatable::Param(param) => finder.visit_param(¶m),
107 Annotatable::FieldDef(field) => finder.visit_field_def(&field),
108 Annotatable::Variant(variant) => finder.visit_variant(&variant),
109 Annotatable::Crate(krate) => finder.visit_crate(krate),
111 finder.has_cfg_or_cfg_attr
115 impl<'ast> visit::Visitor<'ast> for CfgFinder {
116 fn visit_attribute(&mut self, attr: &'ast Attribute) {
117 // We want short-circuiting behavior, so don't use the '|=' operator.
118 self.has_cfg_or_cfg_attr = self.has_cfg_or_cfg_attr
121 .map_or(false, |ident| ident.name == sym::cfg || ident.name == sym::cfg_attr);
125 impl CfgEval<'_, '_> {
126 fn configure<T: HasAttrs + HasTokens>(&mut self, node: T) -> Option<T> {
127 self.cfg.configure(node)
130 fn configure_annotatable(&mut self, mut annotatable: Annotatable) -> Option<Annotatable> {
131 // Tokenizing and re-parsing the `Annotatable` can have a significant
132 // performance impact, so try to avoid it if possible
133 if !CfgFinder::has_cfg_or_cfg_attr(&annotatable) {
134 return Some(annotatable);
137 // The majority of parsed attribute targets will never need to have early cfg-expansion
138 // run (e.g. they are not part of a `#[derive]` or `#[cfg_eval]` macro input).
139 // Therefore, we normally do not capture the necessary information about `#[cfg]`
140 // and `#[cfg_attr]` attributes during parsing.
142 // Therefore, when we actually *do* run early cfg-expansion, we need to tokenize
143 // and re-parse the attribute target, this time capturing information about
144 // the location of `#[cfg]` and `#[cfg_attr]` in the token stream. The tokenization
145 // process is lossless, so this process is invisible to proc-macros.
147 let parse_annotatable_with: fn(&mut Parser<'_>) -> _ = match annotatable {
148 Annotatable::Item(_) => {
149 |parser| Annotatable::Item(parser.parse_item(ForceCollect::Yes).unwrap().unwrap())
151 Annotatable::TraitItem(_) => |parser| {
152 Annotatable::TraitItem(
153 parser.parse_trait_item(ForceCollect::Yes).unwrap().unwrap().unwrap(),
156 Annotatable::ImplItem(_) => |parser| {
157 Annotatable::ImplItem(
158 parser.parse_impl_item(ForceCollect::Yes).unwrap().unwrap().unwrap(),
161 Annotatable::ForeignItem(_) => |parser| {
162 Annotatable::ForeignItem(
163 parser.parse_foreign_item(ForceCollect::Yes).unwrap().unwrap().unwrap(),
166 Annotatable::Stmt(_) => |parser| {
167 Annotatable::Stmt(P(parser.parse_stmt(ForceCollect::Yes).unwrap().unwrap()))
169 Annotatable::Expr(_) => {
170 |parser| Annotatable::Expr(parser.parse_expr_force_collect().unwrap())
175 // 'Flatten' all nonterminals (i.e. `TokenKind::Interpolated`)
176 // to `None`-delimited groups containing the corresponding tokens. This
177 // is normally delayed until the proc-macro server actually needs to
178 // provide a `TokenKind::Interpolated` to a proc-macro. We do this earlier,
179 // so that we can handle cases like:
182 // #[cfg_eval] #[cfg] $item
185 // where `$item` is `#[cfg_attr] struct Foo {}`. We want to make
186 // sure to evaluate *all* `#[cfg]` and `#[cfg_attr]` attributes - the simplest
187 // way to do this is to do a single parse of a stream without any nonterminals.
188 let orig_tokens = annotatable.to_tokens().flattened();
190 // Re-parse the tokens, setting the `capture_cfg` flag to save extra information
191 // to the captured `AttrAnnotatedTokenStream` (specifically, we capture
192 // `AttrAnnotatedTokenTree::AttributesData` for all occurrences of `#[cfg]` and `#[cfg_attr]`)
194 rustc_parse::stream_to_parser(&self.cfg.sess.parse_sess, orig_tokens, None);
195 parser.capture_cfg = true;
196 annotatable = parse_annotatable_with(&mut parser);
198 // Now that we have our re-parsed `AttrAnnotatedTokenStream`, recursively configuring
199 // our attribute target will correctly the tokens as well.
200 flat_map_annotatable(self, annotatable)
204 impl MutVisitor for CfgEval<'_, '_> {
205 fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
206 self.cfg.configure_expr(expr);
207 mut_visit::noop_visit_expr(expr, self);
210 fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
211 let mut expr = configure!(self, expr);
212 mut_visit::noop_visit_expr(&mut expr, self);
216 fn flat_map_generic_param(
218 param: ast::GenericParam,
219 ) -> SmallVec<[ast::GenericParam; 1]> {
220 mut_visit::noop_flat_map_generic_param(configure!(self, param), self)
223 fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
224 mut_visit::noop_flat_map_stmt(configure!(self, stmt), self)
227 fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
228 mut_visit::noop_flat_map_item(configure!(self, item), self)
231 fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
232 mut_visit::noop_flat_map_assoc_item(configure!(self, item), self)
235 fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
236 mut_visit::noop_flat_map_assoc_item(configure!(self, item), self)
239 fn flat_map_foreign_item(
241 foreign_item: P<ast::ForeignItem>,
242 ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
243 mut_visit::noop_flat_map_foreign_item(configure!(self, foreign_item), self)
246 fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
247 mut_visit::noop_flat_map_arm(configure!(self, arm), self)
250 fn flat_map_expr_field(&mut self, field: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
251 mut_visit::noop_flat_map_expr_field(configure!(self, field), self)
254 fn flat_map_pat_field(&mut self, fp: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
255 mut_visit::noop_flat_map_pat_field(configure!(self, fp), self)
258 fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
259 mut_visit::noop_flat_map_param(configure!(self, p), self)
262 fn flat_map_field_def(&mut self, sf: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
263 mut_visit::noop_flat_map_field_def(configure!(self, sf), self)
266 fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
267 mut_visit::noop_flat_map_variant(configure!(self, variant), self)