src/libsyntax/std_inject.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 ast;
  12 use attr;
  13 use codemap::{DUMMY_SP, Span, ExpnInfo, NameAndSpan, MacroAttribute};
  14 use codemap;
  15 use fold::Folder;
  16 use fold;
  17 use parse::token::InternedString;
  18 use parse::token::special_idents;
  19 use parse::{token, ParseSess};
  20 use ptr::P;
  21 use util::small_vector::SmallVector;
  22
  23 /// Craft a span that will be ignored by the stability lint's
  24 /// call to codemap's is_internal check.
  25 /// The expanded code uses the unstable `#[prelude_import]` attribute.
  26 fn ignored_span(sess: &ParseSess, sp: Span) -> Span {
  27     let info = ExpnInfo {
  28         call_site: DUMMY_SP,
  29         callee: NameAndSpan {
  30             name: "std_inject".to_string(),
  31             format: MacroAttribute,
  32             span: None,
  33             allow_internal_unstable: true,
  34         }
  35     };
  36     let expn_id = sess.codemap().record_expansion(info);
  37     let mut sp = sp;
  38     sp.expn_id = expn_id;
  39     return sp;
  40 }
  41
  42 pub fn maybe_inject_crates_ref(krate: ast::Crate, alt_std_name: Option<String>)
  43                                -> ast::Crate {
  44     if use_std(&krate) {
  45         inject_crates_ref(krate, alt_std_name)
  46     } else {
  47         krate
  48     }
  49 }
  50
  51 pub fn maybe_inject_prelude(sess: &ParseSess, krate: ast::Crate) -> ast::Crate {
  52     if use_std(&krate) {
  53         let mut fold = PreludeInjector {
  54             span: ignored_span(sess, DUMMY_SP)
  55         };
  56         fold.fold_crate(krate)
  57     } else {
  58         krate
  59     }
  60 }
  61
  62 pub fn use_std(krate: &ast::Crate) -> bool {
  63     !attr::contains_name(&krate.attrs, "no_std")
  64 }
  65
  66 fn no_prelude(attrs: &[ast::Attribute]) -> bool {
  67     attr::contains_name(attrs, "no_implicit_prelude")
  68 }
  69
  70 struct StandardLibraryInjector {
  71     alt_std_name: Option<String>,
  72 }
  73
  74 impl fold::Folder for StandardLibraryInjector {
  75     fn fold_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
  76
  77         // The name to use in `extern crate name as std;`
  78         let actual_crate_name = match self.alt_std_name {
  79             Some(ref s) => token::intern(&s),
  80             None => token::intern("std"),
  81         };
  82
  83         krate.module.items.insert(0, P(ast::Item {
  84             id: ast::DUMMY_NODE_ID,
  85             ident: token::str_to_ident("std"),
  86             attrs: vec!(
  87                 attr::mk_attr_outer(attr::mk_attr_id(), attr::mk_word_item(
  88                         InternedString::new("macro_use")))),
  89             node: ast::ItemExternCrate(Some(actual_crate_name)),
  90             vis: ast::Inherited,
  91             span: DUMMY_SP
  92         }));
  93
  94         krate
  95     }
  96 }
  97
  98 fn inject_crates_ref(krate: ast::Crate, alt_std_name: Option<String>) -> ast::Crate {
  99     let mut fold = StandardLibraryInjector {
 100         alt_std_name: alt_std_name
 101     };
 102     fold.fold_crate(krate)
 103 }
 104
 105 struct PreludeInjector {
 106     span: Span
 107 }
 108
 109 impl fold::Folder for PreludeInjector {
 110     fn fold_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 111         // only add `use std::prelude::*;` if there wasn't a
 112         // `#![no_implicit_prelude]` at the crate level.
 113         // fold_mod() will insert glob path.
 114         if !no_prelude(&krate.attrs) {
 115             krate.module = self.fold_mod(krate.module);
 116         }
 117         krate
 118     }
 119
 120     fn fold_item(&mut self, item: P<ast::Item>) -> SmallVector<P<ast::Item>> {
 121         if !no_prelude(&item.attrs) {
 122             // only recur if there wasn't `#![no_implicit_prelude]`
 123             // on this item, i.e. this means that the prelude is not
 124             // implicitly imported though the whole subtree
 125             fold::noop_fold_item(item, self)
 126         } else {
 127             SmallVector::one(item)
 128         }
 129     }
 130
 131     fn fold_mod(&mut self, mut mod_: ast::Mod) -> ast::Mod {
 132         let prelude_path = ast::Path {
 133             span: self.span,
 134             global: false,
 135             segments: vec![
 136                 ast::PathSegment {
 137                     identifier: token::str_to_ident("std"),
 138                     parameters: ast::PathParameters::none(),
 139                 },
 140                 ast::PathSegment {
 141                     identifier: token::str_to_ident("prelude"),
 142                     parameters: ast::PathParameters::none(),
 143                 },
 144                 ast::PathSegment {
 145                     identifier: token::str_to_ident("v1"),
 146                     parameters: ast::PathParameters::none(),
 147                 },
 148             ],
 149         };
 150
 151         let vp = P(codemap::dummy_spanned(ast::ViewPathGlob(prelude_path)));
 152         mod_.items.insert(0, P(ast::Item {
 153             id: ast::DUMMY_NODE_ID,
 154             ident: special_idents::invalid,
 155             node: ast::ItemUse(vp),
 156             attrs: vec![ast::Attribute {
 157                 span: self.span,
 158                 node: ast::Attribute_ {
 159                     id: attr::mk_attr_id(),
 160                     style: ast::AttrOuter,
 161                     value: P(ast::MetaItem {
 162                         span: self.span,
 163                         node: ast::MetaWord(special_idents::prelude_import.name.as_str()),
 164                     }),
 165                     is_sugared_doc: false,
 166                 },
 167             }],
 168             vis: ast::Inherited,
 169             span: self.span,
 170         }));
 171
 172         fold::noop_fold_mod(mod_, self)
 173     }
 174 }