1use core::ops::ControlFlow;
2
3use rustc_ast as ast;
4use rustc_ast::mut_visit::MutVisitor;
5use rustc_ast::ptr::P;
6use rustc_ast::visit::{AssocCtxt, Visitor};
7use rustc_ast::{Attribute, HasAttrs, HasTokens, NodeId, mut_visit, visit};
8use rustc_errors::PResult;
9use rustc_expand::base::{Annotatable, ExtCtxt};
10use rustc_expand::config::StripUnconfigured;
11use rustc_expand::configure;
12use rustc_feature::Features;
13use rustc_parse::parser::{ForceCollect, Parser};
14use rustc_session::Session;
15use rustc_span::{Span, sym};
16use smallvec::SmallVec;
17use tracing::instrument;
18
19use crate::util::{check_builtin_macro_attribute, warn_on_duplicate_attribute};
20
21pub(crate) fn expand(
22 ecx: &mut ExtCtxt<'_>,
23 _span: Span,
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)]
30}
31
32pub(crate) fn cfg_eval(
33 sess: &Session,
34 features: &Features,
35 annotatable: Annotatable,
36 lint_node_id: NodeId,
37) -> Annotatable {
38 let features = Some(features);
39 CfgEval(StripUnconfigured { sess, features, config_tokens: true, lint_node_id })
40 .configure_annotatable(annotatable)
41}
42
43struct CfgEval<'a>(StripUnconfigured<'a>);
44
45fn has_cfg_or_cfg_attr(annotatable: &Annotatable) -> bool {
46 struct CfgFinder;
47
48 impl<'ast> visit::Visitor<'ast> for CfgFinder {
49 type Result = ControlFlow<()>;
50 fn visit_attribute(&mut self, attr: &'ast Attribute) -> ControlFlow<()> {
51 if attr
52 .ident()
53 .is_some_and(|ident| ident.name == sym::cfg || ident.name == sym::cfg_attr)
54 {
55 ControlFlow::Break(())
56 } else {
57 ControlFlow::Continue(())
58 }
59 }
60 }
61
62 let res = match annotatable {
63 Annotatable::Item(item) => CfgFinder.visit_item(item),
64 Annotatable::AssocItem(item, ctxt) => CfgFinder.visit_assoc_item(item, *ctxt),
65 Annotatable::ForeignItem(item) => CfgFinder.visit_foreign_item(item),
66 Annotatable::Stmt(stmt) => CfgFinder.visit_stmt(stmt),
67 Annotatable::Expr(expr) => CfgFinder.visit_expr(expr),
68 _ => unreachable!(),
69 };
70 res.is_break()
71}
72
73impl CfgEval<'_> {
74 fn configure<T: HasAttrs + HasTokens>(&mut self, node: T) -> Option<T> {
75 self.0.configure(node)
76 }
77
78 fn configure_annotatable(mut self, annotatable: Annotatable) -> Annotatable {
79 if !has_cfg_or_cfg_attr(&annotatable) {
82 return annotatable;
83 }
84
85 let orig_tokens = annotatable.to_tokens().flattened();
109
110 let mut parser = Parser::new(&self.0.sess.psess, orig_tokens, None);
117 parser.capture_cfg = true;
118 let res: PResult<'_, Annotatable> = try {
119 match annotatable {
120 Annotatable::Item(_) => {
121 let item = parser.parse_item(ForceCollect::Yes)?.unwrap();
122 Annotatable::Item(self.flat_map_item(item).pop().unwrap())
123 }
124 Annotatable::AssocItem(_, ctxt) => {
125 let item = parser.parse_trait_item(ForceCollect::Yes)?.unwrap().unwrap();
126 Annotatable::AssocItem(
127 self.flat_map_assoc_item(item, ctxt).pop().unwrap(),
128 ctxt,
129 )
130 }
131 Annotatable::ForeignItem(_) => {
132 let item = parser.parse_foreign_item(ForceCollect::Yes)?.unwrap().unwrap();
133 Annotatable::ForeignItem(self.flat_map_foreign_item(item).pop().unwrap())
134 }
135 Annotatable::Stmt(_) => {
136 let stmt = parser
137 .parse_stmt_without_recovery(false, ForceCollect::Yes, false)?
138 .unwrap();
139 Annotatable::Stmt(P(self.flat_map_stmt(stmt).pop().unwrap()))
140 }
141 Annotatable::Expr(_) => {
142 let mut expr = parser.parse_expr_force_collect()?;
143 self.visit_expr(&mut expr);
144 Annotatable::Expr(expr)
145 }
146 _ => unreachable!(),
147 }
148 };
149
150 match res {
151 Ok(ann) => ann,
152 Err(err) => {
153 err.emit();
154 annotatable
155 }
156 }
157 }
158}
159
160impl MutVisitor for CfgEval<'_> {
161 #[instrument(level = "trace", skip(self))]
162 fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
163 self.0.configure_expr(expr, false);
164 mut_visit::walk_expr(self, expr);
165 }
166
167 #[instrument(level = "trace", skip(self))]
168 fn visit_method_receiver_expr(&mut self, expr: &mut P<ast::Expr>) {
169 self.0.configure_expr(expr, true);
170 mut_visit::walk_expr(self, expr);
171 }
172
173 fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
174 let mut expr = configure!(self, expr);
175 mut_visit::walk_expr(self, &mut expr);
176 Some(expr)
177 }
178
179 fn flat_map_generic_param(
180 &mut self,
181 param: ast::GenericParam,
182 ) -> SmallVec<[ast::GenericParam; 1]> {
183 let param = configure!(self, param);
184 mut_visit::walk_flat_map_generic_param(self, param)
185 }
186
187 fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
188 let stmt = configure!(self, stmt);
189 mut_visit::walk_flat_map_stmt(self, stmt)
190 }
191
192 fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
193 let item = configure!(self, item);
194 mut_visit::walk_flat_map_item(self, item)
195 }
196
197 fn flat_map_assoc_item(
198 &mut self,
199 item: P<ast::AssocItem>,
200 ctxt: AssocCtxt,
201 ) -> SmallVec<[P<ast::AssocItem>; 1]> {
202 let item = configure!(self, item);
203 mut_visit::walk_flat_map_assoc_item(self, item, ctxt)
204 }
205
206 fn flat_map_foreign_item(
207 &mut self,
208 foreign_item: P<ast::ForeignItem>,
209 ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
210 let foreign_item = configure!(self, foreign_item);
211 mut_visit::walk_flat_map_foreign_item(self, foreign_item)
212 }
213
214 fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
215 let arm = configure!(self, arm);
216 mut_visit::walk_flat_map_arm(self, arm)
217 }
218
219 fn flat_map_expr_field(&mut self, field: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
220 let field = configure!(self, field);
221 mut_visit::walk_flat_map_expr_field(self, field)
222 }
223
224 fn flat_map_pat_field(&mut self, fp: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
225 let fp = configure!(self, fp);
226 mut_visit::walk_flat_map_pat_field(self, fp)
227 }
228
229 fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
230 let p = configure!(self, p);
231 mut_visit::walk_flat_map_param(self, p)
232 }
233
234 fn flat_map_field_def(&mut self, sf: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
235 let sf = configure!(self, sf);
236 mut_visit::walk_flat_map_field_def(self, sf)
237 }
238
239 fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
240 let variant = configure!(self, variant);
241 mut_visit::walk_flat_map_variant(self, variant)
242 }
243}