src/libsyntax/parse/attr.rs

   1 use crate::attr;
   2 use crate::ast;
   3 use crate::parse::{SeqSep, PResult};
   4 use crate::parse::token::{self, Nonterminal, DelimToken};
   5 use crate::parse::parser::{Parser, TokenType, PathStyle};
   6 use crate::tokenstream::{TokenStream, TokenTree};
   7
   8 use log::debug;
   9 use smallvec::smallvec;
  10
  11 #[derive(Debug)]
  12 enum InnerAttributeParsePolicy<'a> {
  13     Permitted,
  14     NotPermitted { reason: &'a str },
  15 }
  16
  17 const DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG: &str = "an inner attribute is not \
  18                                                      permitted in this context";
  19
  20 impl<'a> Parser<'a> {
  21     crate fn parse_arg_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
  22         let attrs = self.parse_outer_attributes()?;
  23         attrs.iter().for_each(|a|
  24             self.sess.param_attr_spans.borrow_mut().push(a.span)
  25         );
  26         Ok(attrs)
  27     }
  28
  29     /// Parse attributes that appear before an item
  30     crate fn parse_outer_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
  31         let mut attrs: Vec<ast::Attribute> = Vec::new();
  32         let mut just_parsed_doc_comment = false;
  33         loop {
  34             debug!("parse_outer_attributes: self.token={:?}", self.token);
  35             match self.token.kind {
  36                 token::Pound => {
  37                     let inner_error_reason = if just_parsed_doc_comment {
  38                         "an inner attribute is not permitted following an outer doc comment"
  39                     } else if !attrs.is_empty() {
  40                         "an inner attribute is not permitted following an outer attribute"
  41                     } else {
  42                         DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG
  43                     };
  44                     let inner_parse_policy =
  45                         InnerAttributeParsePolicy::NotPermitted { reason: inner_error_reason };
  46                     let attr = self.parse_attribute_with_inner_parse_policy(inner_parse_policy)?;
  47                     attrs.push(attr);
  48                     just_parsed_doc_comment = false;
  49                 }
  50                 token::DocComment(s) => {
  51                     let attr = attr::mk_sugared_doc_attr(attr::mk_attr_id(), s, self.token.span);
  52                     if attr.style != ast::AttrStyle::Outer {
  53                         let mut err = self.fatal("expected outer doc comment");
  54                         err.note("inner doc comments like this (starting with \
  55                                   `//!` or `/*!`) can only appear before items");
  56                         return Err(err);
  57                     }
  58                     attrs.push(attr);
  59                     self.bump();
  60                     just_parsed_doc_comment = true;
  61                 }
  62                 _ => break,
  63             }
  64         }
  65         Ok(attrs)
  66     }
  67
  68     /// Matches `attribute = # ! [ meta_item ]`
  69     ///
  70     /// If permit_inner is true, then a leading `!` indicates an inner
  71     /// attribute
  72     pub fn parse_attribute(&mut self, permit_inner: bool) -> PResult<'a, ast::Attribute> {
  73         debug!("parse_attribute: permit_inner={:?} self.token={:?}",
  74                permit_inner,
  75                self.token);
  76         let inner_parse_policy = if permit_inner {
  77             InnerAttributeParsePolicy::Permitted
  78         } else {
  79             InnerAttributeParsePolicy::NotPermitted
  80                 { reason: DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG }
  81         };
  82         self.parse_attribute_with_inner_parse_policy(inner_parse_policy)
  83     }
  84
  85     /// The same as `parse_attribute`, except it takes in an `InnerAttributeParsePolicy`
  86     /// that prescribes how to handle inner attributes.
  87     fn parse_attribute_with_inner_parse_policy(&mut self,
  88                                                inner_parse_policy: InnerAttributeParsePolicy<'_>)
  89                                                -> PResult<'a, ast::Attribute> {
  90         debug!("parse_attribute_with_inner_parse_policy: inner_parse_policy={:?} self.token={:?}",
  91                inner_parse_policy,
  92                self.token);
  93         let (span, path, tokens, style) = match self.token.kind {
  94             token::Pound => {
  95                 let lo = self.token.span;
  96                 self.bump();
  97
  98                 if let InnerAttributeParsePolicy::Permitted = inner_parse_policy {
  99                     self.expected_tokens.push(TokenType::Token(token::Not));
 100                 }
 101                 let style = if self.token == token::Not {
 102                     self.bump();
 103                     if let InnerAttributeParsePolicy::NotPermitted { reason } = inner_parse_policy
 104                     {
 105                         let span = self.token.span;
 106                         self.diagnostic()
 107                             .struct_span_err(span, reason)
 108                             .note("inner attributes, like `#![no_std]`, annotate the item \
 109                                    enclosing them, and are usually found at the beginning of \
 110                                    source files. Outer attributes, like `#[test]`, annotate the \
 111                                    item following them.")
 112                             .emit()
 113                     }
 114                     ast::AttrStyle::Inner
 115                 } else {
 116                     ast::AttrStyle::Outer
 117                 };
 118
 119                 self.expect(&token::OpenDelim(token::Bracket))?;
 120                 let (path, tokens) = self.parse_meta_item_unrestricted()?;
 121                 self.expect(&token::CloseDelim(token::Bracket))?;
 122                 let hi = self.prev_span;
 123
 124                 (lo.to(hi), path, tokens, style)
 125             }
 126             _ => {
 127                 let token_str = self.this_token_to_string();
 128                 return Err(self.fatal(&format!("expected `#`, found `{}`", token_str)));
 129             }
 130         };
 131
 132         Ok(ast::Attribute {
 133             id: attr::mk_attr_id(),
 134             style,
 135             path,
 136             tokens,
 137             is_sugared_doc: false,
 138             span,
 139         })
 140     }
 141
 142     /// Parse an inner part of attribute - path and following tokens.
 143     /// The tokens must be either a delimited token stream, or empty token stream,
 144     /// or the "legacy" key-value form.
 145     /// PATH `(` TOKEN_STREAM `)`
 146     /// PATH `[` TOKEN_STREAM `]`
 147     /// PATH `{` TOKEN_STREAM `}`
 148     /// PATH
 149     /// PATH `=` TOKEN_TREE
 150     /// The delimiters or `=` are still put into the resulting token stream.
 151     crate fn parse_meta_item_unrestricted(&mut self) -> PResult<'a, (ast::Path, TokenStream)> {
 152         let meta = match self.token.kind {
 153             token::Interpolated(ref nt) => match **nt {
 154                 Nonterminal::NtMeta(ref meta) => Some(meta.clone()),
 155                 _ => None,
 156             },
 157             _ => None,
 158         };
 159         Ok(if let Some(meta) = meta {
 160             self.bump();
 161             (meta.path, meta.node.tokens(meta.span))
 162         } else {
 163             let path = self.parse_path(PathStyle::Mod)?;
 164             let tokens = if self.check(&token::OpenDelim(DelimToken::Paren)) ||
 165                self.check(&token::OpenDelim(DelimToken::Bracket)) ||
 166                self.check(&token::OpenDelim(DelimToken::Brace)) {
 167                    self.parse_token_tree().into()
 168             } else if self.eat(&token::Eq) {
 169                 let eq = TokenTree::token(token::Eq, self.prev_span);
 170                 let mut is_interpolated_expr = false;
 171                 if let token::Interpolated(nt) = &self.token.kind {
 172                     if let token::NtExpr(..) = **nt {
 173                         is_interpolated_expr = true;
 174                     }
 175                 }
 176                 let tokens = if is_interpolated_expr {
 177                     // We need to accept arbitrary interpolated expressions to continue
 178                     // supporting things like `doc = $expr` that work on stable.
 179                     // Non-literal interpolated expressions are rejected after expansion.
 180                     self.parse_token_tree().into()
 181                 } else {
 182                     self.parse_unsuffixed_lit()?.tokens()
 183                 };
 184                 TokenStream::from_streams(smallvec![eq.into(), tokens])
 185             } else {
 186                 TokenStream::empty()
 187             };
 188             (path, tokens)
 189         })
 190     }
 191
 192     /// Parse attributes that appear after the opening of an item. These should
 193     /// be preceded by an exclamation mark, but we accept and warn about one
 194     /// terminated by a semicolon.
 195
 196     /// matches inner_attrs*
 197     crate fn parse_inner_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
 198         let mut attrs: Vec<ast::Attribute> = vec![];
 199         loop {
 200             match self.token.kind {
 201                 token::Pound => {
 202                     // Don't even try to parse if it's not an inner attribute.
 203                     if !self.look_ahead(1, |t| t == &token::Not) {
 204                         break;
 205                     }
 206
 207                     let attr = self.parse_attribute(true)?;
 208                     assert_eq!(attr.style, ast::AttrStyle::Inner);
 209                     attrs.push(attr);
 210                 }
 211                 token::DocComment(s) => {
 212                     // we need to get the position of this token before we bump.
 213                     let attr = attr::mk_sugared_doc_attr(attr::mk_attr_id(), s, self.token.span);
 214                     if attr.style == ast::AttrStyle::Inner {
 215                         attrs.push(attr);
 216                         self.bump();
 217                     } else {
 218                         break;
 219                     }
 220                 }
 221                 _ => break,
 222             }
 223         }
 224         Ok(attrs)
 225     }
 226
 227     fn parse_unsuffixed_lit(&mut self) -> PResult<'a, ast::Lit> {
 228         let lit = self.parse_lit()?;
 229         debug!("Checking if {:?} is unusuffixed.", lit);
 230
 231         if !lit.node.is_unsuffixed() {
 232             let msg = "suffixed literals are not allowed in attributes";
 233             self.diagnostic().struct_span_err(lit.span, msg)
 234                              .help("instead of using a suffixed literal \
 235                                     (1u8, 1.0f32, etc.), use an unsuffixed version \
 236                                     (1, 1.0, etc.).")
 237                              .emit()
 238         }
 239
 240         Ok(lit)
 241     }
 242
 243     /// Per RFC#1559, matches the following grammar:
 244     ///
 245     /// meta_item : IDENT ( '=' UNSUFFIXED_LIT | '(' meta_item_inner? ')' )? ;
 246     /// meta_item_inner : (meta_item | UNSUFFIXED_LIT) (',' meta_item_inner)? ;
 247     pub fn parse_meta_item(&mut self) -> PResult<'a, ast::MetaItem> {
 248         let nt_meta = match self.token.kind {
 249             token::Interpolated(ref nt) => match **nt {
 250                 token::NtMeta(ref e) => Some(e.clone()),
 251                 _ => None,
 252             },
 253             _ => None,
 254         };
 255
 256         if let Some(meta) = nt_meta {
 257             self.bump();
 258             return Ok(meta);
 259         }
 260
 261         let lo = self.token.span;
 262         let path = self.parse_path(PathStyle::Mod)?;
 263         let node = self.parse_meta_item_kind()?;
 264         let span = lo.to(self.prev_span);
 265         Ok(ast::MetaItem { path, node, span })
 266     }
 267
 268     crate fn parse_meta_item_kind(&mut self) -> PResult<'a, ast::MetaItemKind> {
 269         Ok(if self.eat(&token::Eq) {
 270             ast::MetaItemKind::NameValue(self.parse_unsuffixed_lit()?)
 271         } else if self.eat(&token::OpenDelim(token::Paren)) {
 272             ast::MetaItemKind::List(self.parse_meta_seq()?)
 273         } else {
 274             ast::MetaItemKind::Word
 275         })
 276     }
 277
 278     /// matches meta_item_inner : (meta_item | UNSUFFIXED_LIT) ;
 279     fn parse_meta_item_inner(&mut self) -> PResult<'a, ast::NestedMetaItem> {
 280         match self.parse_unsuffixed_lit() {
 281             Ok(lit) => {
 282                 return Ok(ast::NestedMetaItem::Literal(lit))
 283             }
 284             Err(ref mut err) => self.diagnostic().cancel(err)
 285         }
 286
 287         match self.parse_meta_item() {
 288             Ok(mi) => {
 289                 return Ok(ast::NestedMetaItem::MetaItem(mi))
 290             }
 291             Err(ref mut err) => self.diagnostic().cancel(err)
 292         }
 293
 294         let found = self.this_token_to_string();
 295         let msg = format!("expected unsuffixed literal or identifier, found `{}`", found);
 296         Err(self.diagnostic().struct_span_err(self.token.span, &msg))
 297     }
 298
 299     /// matches meta_seq = ( COMMASEP(meta_item_inner) )
 300     fn parse_meta_seq(&mut self) -> PResult<'a, Vec<ast::NestedMetaItem>> {
 301         self.parse_seq_to_end(&token::CloseDelim(token::Paren),
 302                               SeqSep::trailing_allowed(token::Comma),
 303                               |p: &mut Parser<'a>| p.parse_meta_item_inner())
 304     }
 305 }