src/tools/rustfmt/src/parse/macros/cfg_if.rs

   1 use std::panic::{catch_unwind, AssertUnwindSafe};
   2
   3 use rustc_ast::ast;
   4 use rustc_ast::token::{DelimToken, TokenKind};
   5 use rustc_parse::parser::ForceCollect;
   6 use rustc_span::symbol::kw;
   7
   8 use crate::parse::macros::build_stream_parser;
   9 use crate::parse::session::ParseSess;
  10
  11 pub(crate) fn parse_cfg_if<'a>(
  12     sess: &'a ParseSess,
  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!"),
  19     }
  20 }
  21
  22 fn parse_cfg_if_inner<'a>(
  23     sess: &'a ParseSess,
  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);
  28
  29     let mut items = vec![];
  30     let mut process_if_cfg = true;
  31
  32     while parser.token.kind != TokenKind::Eof {
  33         if process_if_cfg {
  34             if !parser.eat_keyword(kw::If) {
  35                 return Err("Expected `if`");
  36             }
  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.
  41             //
  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
  45             parser
  46                 .parse_attribute(rustc_parse::parser::attr::InnerAttrPolicy::Permitted)
  47                 .map_err(|_| "Failed to parse attributes")?;
  48         }
  49
  50         if !parser.eat(&TokenKind::OpenDelim(DelimToken::Brace)) {
  51             return Err("Expected an opening brace");
  52         }
  53
  54         while parser.token != TokenKind::CloseDelim(DelimToken::Brace)
  55             && parser.token.kind != TokenKind::Eof
  56         {
  57             let item = match parser.parse_item(ForceCollect::No) {
  58                 Ok(Some(item_ptr)) => item_ptr.into_inner(),
  59                 Ok(None) => continue,
  60                 Err(err) => {
  61                     err.cancel();
  62                     parser.sess.span_diagnostic.reset_err_count();
  63                     return Err(
  64                         "Expected item inside cfg_if block, but failed to parse it as an item",
  65                     );
  66                 }
  67             };
  68             if let ast::ItemKind::Mod(..) = item.kind {
  69                 items.push(item);
  70             }
  71         }
  72
  73         if !parser.eat(&TokenKind::CloseDelim(DelimToken::Brace)) {
  74             return Err("Expected a closing brace");
  75         }
  76
  77         if parser.eat(&TokenKind::Eof) {
  78             break;
  79         }
  80
  81         if !parser.eat_keyword(kw::Else) {
  82             return Err("Expected `else`");
  83         }
  84
  85         process_if_cfg = parser.token.is_keyword(kw::If);
  86     }
  87
  88     Ok(items)
  89 }