src/librustc/metadata/macro_import.rs

   1 // Copyright 2012-2015 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 //! Used by `rustc` when loading a crate with exported macros.
  12
  13 use session::Session;
  14 use metadata::creader::CrateReader;
  15
  16 use std::collections::{HashSet, HashMap};
  17 use syntax::ast;
  18 use syntax::attr;
  19 use syntax::codemap::Span;
  20 use syntax::parse::token;
  21 use syntax::visit;
  22 use syntax::visit::Visitor;
  23 use syntax::attr::AttrMetaMethods;
  24
  25 struct MacroLoader<'a> {
  26     sess: &'a Session,
  27     span_whitelist: HashSet<Span>,
  28     reader: CrateReader<'a>,
  29     macros: Vec<ast::MacroDef>,
  30 }
  31
  32 impl<'a> MacroLoader<'a> {
  33     fn new(sess: &'a Session) -> MacroLoader<'a> {
  34         MacroLoader {
  35             sess: sess,
  36             span_whitelist: HashSet::new(),
  37             reader: CrateReader::new(sess),
  38             macros: vec![],
  39         }
  40     }
  41 }
  42
  43 /// Read exported macros.
  44 pub fn read_macro_defs(sess: &Session, krate: &ast::Crate) -> Vec<ast::MacroDef> {
  45     let mut loader = MacroLoader::new(sess);
  46
  47     // We need to error on `#[macro_use] extern crate` when it isn't at the
  48     // crate root, because `$crate` won't work properly. Identify these by
  49     // spans, because the crate map isn't set up yet.
  50     for item in &krate.module.items {
  51         if let ast::ItemExternCrate(_) = item.node {
  52             loader.span_whitelist.insert(item.span);
  53         }
  54     }
  55
  56     visit::walk_crate(&mut loader, krate);
  57
  58     loader.macros
  59 }
  60
  61 pub type MacroSelection = HashMap<token::InternedString, Span>;
  62
  63 // note that macros aren't expanded yet, and therefore macros can't add macro imports.
  64 impl<'a, 'v> Visitor<'v> for MacroLoader<'a> {
  65     fn visit_item(&mut self, item: &ast::Item) {
  66         // We're only interested in `extern crate`.
  67         match item.node {
  68             ast::ItemExternCrate(_) => {}
  69             _ => {
  70                 visit::walk_item(self, item);
  71                 return;
  72             }
  73         }
  74
  75         // Parse the attributes relating to macros.
  76         let mut import = Some(HashMap::new());  // None => load all
  77         let mut reexport = HashMap::new();
  78
  79         for attr in &item.attrs {
  80             let mut used = true;
  81             match &attr.name()[..] {
  82                 "macro_use" => {
  83                     let names = attr.meta_item_list();
  84                     if names.is_none() {
  85                         // no names => load all
  86                         import = None;
  87                     }
  88                     if let (Some(sel), Some(names)) = (import.as_mut(), names) {
  89                         for attr in names {
  90                             if let ast::MetaWord(ref name) = attr.node {
  91                                 sel.insert(name.clone(), attr.span);
  92                             } else {
  93                                 self.sess.span_err(attr.span, "bad macro import");
  94                             }
  95                         }
  96                     }
  97                 }
  98                 "macro_reexport" => {
  99                     let names = match attr.meta_item_list() {
 100                         Some(names) => names,
 101                         None => {
 102                             self.sess.span_err(attr.span, "bad macro reexport");
 103                             continue;
 104                         }
 105                     };
 106
 107                     for attr in names {
 108                         if let ast::MetaWord(ref name) = attr.node {
 109                             reexport.insert(name.clone(), attr.span);
 110                         } else {
 111                             self.sess.span_err(attr.span, "bad macro reexport");
 112                         }
 113                     }
 114                 }
 115                 _ => used = false,
 116             }
 117             if used {
 118                 attr::mark_used(attr);
 119             }
 120         }
 121
 122         self.load_macros(item, import, reexport)
 123     }
 124
 125     fn visit_mac(&mut self, _: &ast::Mac) {
 126         // bummer... can't see macro imports inside macros.
 127         // do nothing.
 128     }
 129 }
 130
 131 impl<'a> MacroLoader<'a> {
 132     fn load_macros<'b>(&mut self,
 133                        vi: &ast::Item,
 134                        import: Option<MacroSelection>,
 135                        reexport: MacroSelection) {
 136         if let Some(sel) = import.as_ref() {
 137             if sel.is_empty() && reexport.is_empty() {
 138                 return;
 139             }
 140         }
 141
 142         if !self.span_whitelist.contains(&vi.span) {
 143             self.sess.span_err(vi.span, "an `extern crate` loading macros must be at \
 144                                          the crate root");
 145             return;
 146         }
 147
 148         let macros = self.reader.read_exported_macros(vi);
 149         let mut seen = HashSet::new();
 150
 151         for mut def in macros {
 152             let name = token::get_ident(def.ident);
 153             seen.insert(name.clone());
 154
 155             def.use_locally = match import.as_ref() {
 156                 None => true,
 157                 Some(sel) => sel.contains_key(&name),
 158             };
 159             def.export = reexport.contains_key(&name);
 160             def.allow_internal_unstable = attr::contains_name(&def.attrs,
 161                                                               "allow_internal_unstable");
 162             debug!("load_macros: loaded: {:?}", def);
 163             self.macros.push(def);
 164         }
 165
 166         if let Some(sel) = import.as_ref() {
 167             for (name, span) in sel {
 168                 if !seen.contains(name) {
 169                     self.sess.span_err(*span, "imported macro not found");
 170                 }
 171             }
 172         }
 173
 174         for (name, span) in &reexport {
 175             if !seen.contains(name) {
 176                 self.sess.span_err(*span, "reexported macro not found");
 177             }
 178         }
 179     }
 180 }