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_errors::PResult;
11 use rustc_expand::base::{Annotatable, ExtCtxt};
12 use rustc_expand::config::StripUnconfigured;
13 use rustc_expand::configure;
14 use rustc_feature::Features;
15 use rustc_parse::parser::{ForceCollect, Parser};
16 use rustc_session::Session;
17 use rustc_span::symbol::sym;
19 use smallvec::SmallVec;
22 ecx: &mut ExtCtxt<'_>,
24 meta_item: &ast::MetaItem,
25 annotatable: Annotatable,
26 ) -> Vec<Annotatable> {
27 check_builtin_macro_attribute(ecx, meta_item, sym::cfg_eval);
28 warn_on_duplicate_attribute(&ecx, &annotatable, sym::cfg_eval);
29 vec![cfg_eval(ecx.sess, ecx.ecfg.features, annotatable, ecx.current_expansion.lint_node_id)]
32 pub(crate) fn cfg_eval(
34 features: Option<&Features>,
35 annotatable: Annotatable,
38 CfgEval { cfg: &mut StripUnconfigured { sess, features, config_tokens: true, lint_node_id } }
39 .configure_annotatable(annotatable)
40 // Since the item itself has already been configured by the `InvocationCollector`,
41 // we know that fold result vector will contain exactly one element.
45 struct CfgEval<'a, 'b> {
46 cfg: &'a mut StripUnconfigured<'b>,
49 fn flat_map_annotatable(
50 vis: &mut impl MutVisitor,
51 annotatable: Annotatable,
52 ) -> Option<Annotatable> {
54 Annotatable::Item(item) => vis.flat_map_item(item).pop().map(Annotatable::Item),
55 Annotatable::TraitItem(item) => {
56 vis.flat_map_trait_item(item).pop().map(Annotatable::TraitItem)
58 Annotatable::ImplItem(item) => {
59 vis.flat_map_impl_item(item).pop().map(Annotatable::ImplItem)
61 Annotatable::ForeignItem(item) => {
62 vis.flat_map_foreign_item(item).pop().map(Annotatable::ForeignItem)
64 Annotatable::Stmt(stmt) => {
65 vis.flat_map_stmt(stmt.into_inner()).pop().map(P).map(Annotatable::Stmt)
67 Annotatable::Expr(mut expr) => {
68 vis.visit_expr(&mut expr);
69 Some(Annotatable::Expr(expr))
71 Annotatable::Arm(arm) => vis.flat_map_arm(arm).pop().map(Annotatable::Arm),
72 Annotatable::ExprField(field) => {
73 vis.flat_map_expr_field(field).pop().map(Annotatable::ExprField)
75 Annotatable::PatField(fp) => vis.flat_map_pat_field(fp).pop().map(Annotatable::PatField),
76 Annotatable::GenericParam(param) => {
77 vis.flat_map_generic_param(param).pop().map(Annotatable::GenericParam)
79 Annotatable::Param(param) => vis.flat_map_param(param).pop().map(Annotatable::Param),
80 Annotatable::FieldDef(sf) => vis.flat_map_field_def(sf).pop().map(Annotatable::FieldDef),
81 Annotatable::Variant(v) => vis.flat_map_variant(v).pop().map(Annotatable::Variant),
82 Annotatable::Crate(mut krate) => {
83 vis.visit_crate(&mut krate);
84 Some(Annotatable::Crate(krate))
90 has_cfg_or_cfg_attr: bool,
94 fn has_cfg_or_cfg_attr(annotatable: &Annotatable) -> bool {
95 let mut finder = CfgFinder { has_cfg_or_cfg_attr: false };
97 Annotatable::Item(item) => finder.visit_item(&item),
98 Annotatable::TraitItem(item) => finder.visit_assoc_item(&item, visit::AssocCtxt::Trait),
99 Annotatable::ImplItem(item) => finder.visit_assoc_item(&item, visit::AssocCtxt::Impl),
100 Annotatable::ForeignItem(item) => finder.visit_foreign_item(&item),
101 Annotatable::Stmt(stmt) => finder.visit_stmt(&stmt),
102 Annotatable::Expr(expr) => finder.visit_expr(&expr),
103 Annotatable::Arm(arm) => finder.visit_arm(&arm),
104 Annotatable::ExprField(field) => finder.visit_expr_field(&field),
105 Annotatable::PatField(field) => finder.visit_pat_field(&field),
106 Annotatable::GenericParam(param) => finder.visit_generic_param(¶m),
107 Annotatable::Param(param) => finder.visit_param(¶m),
108 Annotatable::FieldDef(field) => finder.visit_field_def(&field),
109 Annotatable::Variant(variant) => finder.visit_variant(&variant),
110 Annotatable::Crate(krate) => finder.visit_crate(krate),
112 finder.has_cfg_or_cfg_attr
116 impl<'ast> visit::Visitor<'ast> for CfgFinder {
117 fn visit_attribute(&mut self, attr: &'ast Attribute) {
118 // We want short-circuiting behavior, so don't use the '|=' operator.
119 self.has_cfg_or_cfg_attr = self.has_cfg_or_cfg_attr
122 .map_or(false, |ident| ident.name == sym::cfg || ident.name == sym::cfg_attr);
126 impl CfgEval<'_, '_> {
127 fn configure<T: HasAttrs + HasTokens>(&mut self, node: T) -> Option<T> {
128 self.cfg.configure(node)
131 fn configure_annotatable(&mut self, mut annotatable: Annotatable) -> Option<Annotatable> {
132 // Tokenizing and re-parsing the `Annotatable` can have a significant
133 // performance impact, so try to avoid it if possible
134 if !CfgFinder::has_cfg_or_cfg_attr(&annotatable) {
135 return Some(annotatable);
138 // The majority of parsed attribute targets will never need to have early cfg-expansion
139 // run (e.g. they are not part of a `#[derive]` or `#[cfg_eval]` macro input).
140 // Therefore, we normally do not capture the necessary information about `#[cfg]`
141 // and `#[cfg_attr]` attributes during parsing.
143 // Therefore, when we actually *do* run early cfg-expansion, we need to tokenize
144 // and re-parse the attribute target, this time capturing information about
145 // the location of `#[cfg]` and `#[cfg_attr]` in the token stream. The tokenization
146 // process is lossless, so this process is invisible to proc-macros.
148 let parse_annotatable_with: for<'a> fn(&mut Parser<'a>) -> PResult<'a, _> =
150 Annotatable::Item(_) => {
151 |parser| Ok(Annotatable::Item(parser.parse_item(ForceCollect::Yes)?.unwrap()))
153 Annotatable::TraitItem(_) => |parser| {
154 Ok(Annotatable::TraitItem(
155 parser.parse_trait_item(ForceCollect::Yes)?.unwrap().unwrap(),
158 Annotatable::ImplItem(_) => |parser| {
159 Ok(Annotatable::ImplItem(
160 parser.parse_impl_item(ForceCollect::Yes)?.unwrap().unwrap(),
163 Annotatable::ForeignItem(_) => |parser| {
164 Ok(Annotatable::ForeignItem(
165 parser.parse_foreign_item(ForceCollect::Yes)?.unwrap().unwrap(),
168 Annotatable::Stmt(_) => |parser| {
169 Ok(Annotatable::Stmt(P(parser.parse_stmt(ForceCollect::Yes)?.unwrap())))
171 Annotatable::Expr(_) => {
172 |parser| Ok(Annotatable::Expr(parser.parse_expr_force_collect()?))
177 // 'Flatten' all nonterminals (i.e. `TokenKind::Interpolated`)
178 // to `None`-delimited groups containing the corresponding tokens. This
179 // is normally delayed until the proc-macro server actually needs to
180 // provide a `TokenKind::Interpolated` to a proc-macro. We do this earlier,
181 // so that we can handle cases like:
184 // #[cfg_eval] #[cfg] $item
187 // where `$item` is `#[cfg_attr] struct Foo {}`. We want to make
188 // sure to evaluate *all* `#[cfg]` and `#[cfg_attr]` attributes - the simplest
189 // way to do this is to do a single parse of a stream without any nonterminals.
190 let orig_tokens = annotatable.to_tokens().flattened();
192 // Re-parse the tokens, setting the `capture_cfg` flag to save extra information
193 // to the captured `AttrTokenStream` (specifically, we capture
194 // `AttrTokenTree::AttributesData` for all occurrences of `#[cfg]` and `#[cfg_attr]`)
196 rustc_parse::stream_to_parser(&self.cfg.sess.parse_sess, orig_tokens, None);
197 parser.capture_cfg = true;
198 match parse_annotatable_with(&mut parser) {
199 Ok(a) => annotatable = a,
202 return Some(annotatable);
206 // Now that we have our re-parsed `AttrTokenStream`, recursively configuring
207 // our attribute target will correctly the tokens as well.
208 flat_map_annotatable(self, annotatable)
212 impl MutVisitor for CfgEval<'_, '_> {
213 #[instrument(level = "trace", skip(self))]
214 fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
215 self.cfg.configure_expr(expr, false);
216 mut_visit::noop_visit_expr(expr, self);
219 #[instrument(level = "trace", skip(self))]
220 fn visit_method_receiver_expr(&mut self, expr: &mut P<ast::Expr>) {
221 self.cfg.configure_expr(expr, true);
222 mut_visit::noop_visit_expr(expr, self);
225 fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
226 let mut expr = configure!(self, expr);
227 mut_visit::noop_visit_expr(&mut expr, self);
231 fn flat_map_generic_param(
233 param: ast::GenericParam,
234 ) -> SmallVec<[ast::GenericParam; 1]> {
235 mut_visit::noop_flat_map_generic_param(configure!(self, param), self)
238 fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
239 mut_visit::noop_flat_map_stmt(configure!(self, stmt), self)
242 fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
243 mut_visit::noop_flat_map_item(configure!(self, item), self)
246 fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
247 mut_visit::noop_flat_map_assoc_item(configure!(self, item), self)
250 fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
251 mut_visit::noop_flat_map_assoc_item(configure!(self, item), self)
254 fn flat_map_foreign_item(
256 foreign_item: P<ast::ForeignItem>,
257 ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
258 mut_visit::noop_flat_map_foreign_item(configure!(self, foreign_item), self)
261 fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
262 mut_visit::noop_flat_map_arm(configure!(self, arm), self)
265 fn flat_map_expr_field(&mut self, field: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
266 mut_visit::noop_flat_map_expr_field(configure!(self, field), self)
269 fn flat_map_pat_field(&mut self, fp: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
270 mut_visit::noop_flat_map_pat_field(configure!(self, fp), self)
273 fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
274 mut_visit::noop_flat_map_param(configure!(self, p), self)
277 fn flat_map_field_def(&mut self, sf: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
278 mut_visit::noop_flat_map_field_def(configure!(self, sf), self)
281 fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
282 mut_visit::noop_flat_map_variant(configure!(self, variant), self)