src/libsyntax/parse/attr.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use attr;
  12 use ast;
  13 use codemap::respan;
  14 use parse::common::SeqSep;
  15 use parse::PResult;
  16 use parse::token::{self, Nonterminal};
  17 use parse::parser::{Parser, TokenType, PathStyle};
  18 use tokenstream::TokenStream;
  19
  20 #[derive(PartialEq, Eq, Debug)]
  21 enum InnerAttributeParsePolicy<'a> {
  22     Permitted,
  23     NotPermitted { reason: &'a str },
  24 }
  25
  26 const DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG: &'static str = "an inner attribute is not \
  27                                                              permitted in this context";
  28
  29 impl<'a> Parser<'a> {
  30     /// Parse attributes that appear before an item
  31     pub fn parse_outer_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
  32         let mut attrs: Vec<ast::Attribute> = Vec::new();
  33         let mut just_parsed_doc_comment = false;
  34         loop {
  35             debug!("parse_outer_attributes: self.token={:?}", self.token);
  36             match self.token {
  37                 token::Pound => {
  38                     let inner_error_reason = if just_parsed_doc_comment {
  39                         "an inner attribute is not permitted following an outer doc comment"
  40                     } else if !attrs.is_empty() {
  41                         "an inner attribute is not permitted following an outer attribute"
  42                     } else {
  43                         DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG
  44                     };
  45                     let inner_parse_policy =
  46                         InnerAttributeParsePolicy::NotPermitted { reason: inner_error_reason };
  47                     attrs.push(self.parse_attribute_with_inner_parse_policy(inner_parse_policy)?);
  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.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, mut style) = match self.token {
  94             token::Pound => {
  95                 let lo = self.span;
  96                 self.bump();
  97
  98                 if inner_parse_policy == InnerAttributeParsePolicy::Permitted {
  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.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_path_and_tokens()?;
 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         if inner_parse_policy == InnerAttributeParsePolicy::Permitted &&
 133            self.token == token::Semi {
 134             self.bump();
 135             self.span_warn(span,
 136                            "this inner attribute syntax is deprecated. The new syntax is \
 137                             `#![foo]`, with a bang and no semicolon");
 138             style = ast::AttrStyle::Inner;
 139         }
 140
 141         Ok(ast::Attribute {
 142             id: attr::mk_attr_id(),
 143             style,
 144             path,
 145             tokens,
 146             is_sugared_doc: false,
 147             span,
 148         })
 149     }
 150
 151     pub fn parse_path_and_tokens(&mut self) -> PResult<'a, (ast::Path, TokenStream)> {
 152         let meta = match self.token {
 153             token::Interpolated(ref nt) => match nt.0 {
 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             (ast::Path::from_ident(meta.span, ast::Ident::with_empty_ctxt(meta.name)),
 162              meta.node.tokens(meta.span))
 163         } else {
 164             (self.parse_path(PathStyle::Mod)?, self.parse_tokens())
 165         })
 166     }
 167
 168     /// Parse attributes that appear after the opening of an item. These should
 169     /// be preceded by an exclamation mark, but we accept and warn about one
 170     /// terminated by a semicolon.
 171
 172     /// matches inner_attrs*
 173     pub fn parse_inner_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
 174         let mut attrs: Vec<ast::Attribute> = vec![];
 175         loop {
 176             match self.token {
 177                 token::Pound => {
 178                     // Don't even try to parse if it's not an inner attribute.
 179                     if !self.look_ahead(1, |t| t == &token::Not) {
 180                         break;
 181                     }
 182
 183                     let attr = self.parse_attribute(true)?;
 184                     assert_eq!(attr.style, ast::AttrStyle::Inner);
 185                     attrs.push(attr);
 186                 }
 187                 token::DocComment(s) => {
 188                     // we need to get the position of this token before we bump.
 189                     let attr = attr::mk_sugared_doc_attr(attr::mk_attr_id(), s, self.span);
 190                     if attr.style == ast::AttrStyle::Inner {
 191                         attrs.push(attr);
 192                         self.bump();
 193                     } else {
 194                         break;
 195                     }
 196                 }
 197                 _ => break,
 198             }
 199         }
 200         Ok(attrs)
 201     }
 202
 203     fn parse_unsuffixed_lit(&mut self) -> PResult<'a, ast::Lit> {
 204         let lit = self.parse_lit()?;
 205         debug!("Checking if {:?} is unusuffixed.", lit);
 206
 207         if !lit.node.is_unsuffixed() {
 208             let msg = "suffixed literals are not allowed in attributes";
 209             self.diagnostic().struct_span_err(lit.span, msg)
 210                              .help("instead of using a suffixed literal \
 211                                     (1u8, 1.0f32, etc.), use an unsuffixed version \
 212                                     (1, 1.0, etc.).")
 213                              .emit()
 214         }
 215
 216         Ok(lit)
 217     }
 218
 219     /// Per RFC#1559, matches the following grammar:
 220     ///
 221     /// meta_item : IDENT ( '=' UNSUFFIXED_LIT | '(' meta_item_inner? ')' )? ;
 222     /// meta_item_inner : (meta_item | UNSUFFIXED_LIT) (',' meta_item_inner)? ;
 223     pub fn parse_meta_item(&mut self) -> PResult<'a, ast::MetaItem> {
 224         let nt_meta = match self.token {
 225             token::Interpolated(ref nt) => match nt.0 {
 226                 token::NtMeta(ref e) => Some(e.clone()),
 227                 _ => None,
 228             },
 229             _ => None,
 230         };
 231
 232         if let Some(meta) = nt_meta {
 233             self.bump();
 234             return Ok(meta);
 235         }
 236
 237         let lo = self.span;
 238         let ident = self.parse_ident()?;
 239         let node = self.parse_meta_item_kind()?;
 240         Ok(ast::MetaItem { name: ident.name, node: node, span: lo.to(self.prev_span) })
 241     }
 242
 243     pub fn parse_meta_item_kind(&mut self) -> PResult<'a, ast::MetaItemKind> {
 244         Ok(if self.eat(&token::Eq) {
 245             ast::MetaItemKind::NameValue(self.parse_unsuffixed_lit()?)
 246         } else if self.eat(&token::OpenDelim(token::Paren)) {
 247             ast::MetaItemKind::List(self.parse_meta_seq()?)
 248         } else {
 249             ast::MetaItemKind::Word
 250         })
 251     }
 252
 253     /// matches meta_item_inner : (meta_item | UNSUFFIXED_LIT) ;
 254     fn parse_meta_item_inner(&mut self) -> PResult<'a, ast::NestedMetaItem> {
 255         let lo = self.span;
 256
 257         match self.parse_unsuffixed_lit() {
 258             Ok(lit) => {
 259                 return Ok(respan(lo.to(self.prev_span), ast::NestedMetaItemKind::Literal(lit)))
 260             }
 261             Err(ref mut err) => self.diagnostic().cancel(err)
 262         }
 263
 264         match self.parse_meta_item() {
 265             Ok(mi) => {
 266                 return Ok(respan(lo.to(self.prev_span), ast::NestedMetaItemKind::MetaItem(mi)))
 267             }
 268             Err(ref mut err) => self.diagnostic().cancel(err)
 269         }
 270
 271         let found = self.this_token_to_string();
 272         let msg = format!("expected unsuffixed literal or identifier, found {}", found);
 273         Err(self.diagnostic().struct_span_err(lo, &msg))
 274     }
 275
 276     /// matches meta_seq = ( COMMASEP(meta_item_inner) )
 277     fn parse_meta_seq(&mut self) -> PResult<'a, Vec<ast::NestedMetaItem>> {
 278         self.parse_seq_to_end(&token::CloseDelim(token::Paren),
 279                               SeqSep::trailing_allowed(token::Comma),
 280                               |p: &mut Parser<'a>| p.parse_meta_item_inner())
 281     }
 282 }