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 std::cell::Cell;
  14 use ext::hygiene::{Mark, SyntaxContext};
  15 use symbol::{Symbol, keywords};
  16 use syntax_pos::{DUMMY_SP, Span};
  17 use codemap::{ExpnInfo, MacroAttribute, dummy_spanned, hygiene, respan};
  18 use ptr::P;
  19 use tokenstream::TokenStream;
  20
  21 /// Craft a span that will be ignored by the stability lint's
  22 /// call to codemap's `is_internal` check.
  23 /// The expanded code uses the unstable `#[prelude_import]` attribute.
  24 fn ignored_span(sp: Span) -> Span {
  25     let mark = Mark::fresh(Mark::root());
  26     mark.set_expn_info(ExpnInfo {
  27         call_site: DUMMY_SP,
  28         def_site: None,
  29         format: MacroAttribute(Symbol::intern("std_inject")),
  30         allow_internal_unstable: true,
  31         allow_internal_unsafe: false,
  32         local_inner_macros: false,
  33         edition: hygiene::default_edition(),
  34     });
  35     sp.with_ctxt(SyntaxContext::empty().apply_mark(mark))
  36 }
  37
  38 pub fn injected_crate_name() -> Option<&'static str> {
  39     INJECTED_CRATE_NAME.with(|name| name.get())
  40 }
  41
  42 thread_local! {
  43     static INJECTED_CRATE_NAME: Cell<Option<&'static str>> = Cell::new(None);
  44 }
  45
  46 pub fn maybe_inject_crates_ref(mut krate: ast::Crate, alt_std_name: Option<&str>) -> ast::Crate {
  47     // the first name in this list is the crate name of the crate with the prelude
  48     let names: &[&str] = if attr::contains_name(&krate.attrs, "no_core") {
  49         return krate;
  50     } else if attr::contains_name(&krate.attrs, "no_std") {
  51         if attr::contains_name(&krate.attrs, "compiler_builtins") {
  52             &["core"]
  53         } else {
  54             &["core", "compiler_builtins"]
  55         }
  56     } else {
  57         &["std"]
  58     };
  59
  60     // .rev() to preserve ordering above in combination with insert(0, ...)
  61     for name in names.iter().rev() {
  62         krate.module.items.insert(0, P(ast::Item {
  63             attrs: vec![attr::mk_attr_outer(DUMMY_SP,
  64                                             attr::mk_attr_id(),
  65                                             attr::mk_word_item(ast::Ident::from_str("macro_use")))],
  66             vis: dummy_spanned(ast::VisibilityKind::Inherited),
  67             node: ast::ItemKind::ExternCrate(alt_std_name.map(Symbol::intern)),
  68             ident: ast::Ident::from_str(name),
  69             id: ast::DUMMY_NODE_ID,
  70             span: DUMMY_SP,
  71             tokens: None,
  72         }));
  73     }
  74
  75     // the crates have been injected, the assumption is that the first one is the one with
  76     // the prelude.
  77     let name = names[0];
  78
  79     INJECTED_CRATE_NAME.with(|opt_name| opt_name.set(Some(name)));
  80
  81     let span = ignored_span(DUMMY_SP);
  82     krate.module.items.insert(0, P(ast::Item {
  83         attrs: vec![ast::Attribute {
  84             style: ast::AttrStyle::Outer,
  85             path: ast::Path::from_ident(ast::Ident::new(Symbol::intern("prelude_import"), span)),
  86             tokens: TokenStream::empty(),
  87             id: attr::mk_attr_id(),
  88             is_sugared_doc: false,
  89             span,
  90         }],
  91         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
  92         node: ast::ItemKind::Use(P(ast::UseTree {
  93             prefix: ast::Path {
  94                 segments: [name, "prelude", "v1"].into_iter().map(|name| {
  95                     ast::PathSegment::from_ident(ast::Ident::from_str(name))
  96                 }).collect(),
  97                 span,
  98             },
  99             kind: ast::UseTreeKind::Glob,
 100             span,
 101         })),
 102         id: ast::DUMMY_NODE_ID,
 103         ident: keywords::Invalid.ident(),
 104         span,
 105         tokens: None,
 106     }));
 107
 108     krate
 109 }