1 use std::panic::{catch_unwind, AssertUnwindSafe};
4 use rustc_ast::token::{Delimiter, TokenKind};
5 use rustc_parse::parser::ForceCollect;
6 use rustc_span::symbol::kw;
8 use crate::parse::macros::build_stream_parser;
9 use crate::parse::session::ParseSess;
11 pub(crate) fn parse_cfg_if<'a>(
13 mac: &'a ast::MacCall,
14 ) -> Result<Vec<ast::Item>, &'static str> {
15 match catch_unwind(AssertUnwindSafe(|| parse_cfg_if_inner(sess, mac))) {
16 Ok(Ok(items)) => Ok(items),
17 Ok(err @ Err(_)) => err,
18 Err(..) => Err("failed to parse cfg_if!"),
22 fn parse_cfg_if_inner<'a>(
24 mac: &'a ast::MacCall,
25 ) -> Result<Vec<ast::Item>, &'static str> {
26 let ts = mac.args.inner_tokens();
27 let mut parser = build_stream_parser(sess.inner(), ts);
29 let mut items = vec![];
30 let mut process_if_cfg = true;
32 while parser.token.kind != TokenKind::Eof {
34 if !parser.eat_keyword(kw::If) {
35 return Err("Expected `if`");
37 // Inner attributes are not actually syntactically permitted here, but we don't
38 // care about inner vs outer attributes in this position. Our purpose with this
39 // special case parsing of cfg_if macros is to ensure we can correctly resolve
40 // imported modules that may have a custom `path` defined.
42 // As such, we just need to advance the parser past the attribute and up to
43 // to the opening brace.
44 // See also https://github.com/rust-lang/rust/pull/79433
46 .parse_attribute(rustc_parse::parser::attr::InnerAttrPolicy::Permitted)
47 .map_err(|_| "Failed to parse attributes")?;
50 if !parser.eat(&TokenKind::OpenDelim(Delimiter::Brace)) {
51 return Err("Expected an opening brace");
54 while parser.token != TokenKind::CloseDelim(Delimiter::Brace)
55 && parser.token.kind != TokenKind::Eof
57 let item = match parser.parse_item(ForceCollect::No) {
58 Ok(Some(item_ptr)) => item_ptr.into_inner(),
62 parser.sess.span_diagnostic.reset_err_count();
64 "Expected item inside cfg_if block, but failed to parse it as an item",
68 if let ast::ItemKind::Mod(..) = item.kind {
73 if !parser.eat(&TokenKind::CloseDelim(Delimiter::Brace)) {
74 return Err("Expected a closing brace");
77 if parser.eat(&TokenKind::Eof) {
81 if !parser.eat_keyword(kw::Else) {
82 return Err("Expected `else`");
85 process_if_cfg = parser.token.is_keyword(kw::If);