src/libsyntax_ext/standard_library_imports.rs

   1 use syntax::{ast, attr};
   2 use syntax::edition::Edition;
   3 use syntax::ext::hygiene::{ExpnId, MacroKind};
   4 use syntax::ptr::P;
   5 use syntax::source_map::{ExpnInfo, ExpnKind, dummy_spanned, respan};
   6 use syntax::symbol::{Ident, Symbol, kw, sym};
   7 use syntax::tokenstream::TokenStream;
   8 use syntax_pos::DUMMY_SP;
   9
  10 use std::iter;
  11
  12 pub fn inject(
  13     mut krate: ast::Crate, alt_std_name: Option<&str>, edition: Edition
  14 ) -> (ast::Crate, Option<Symbol>) {
  15     let rust_2018 = edition >= Edition::Edition2018;
  16
  17     // the first name in this list is the crate name of the crate with the prelude
  18     let names: &[&str] = if attr::contains_name(&krate.attrs, sym::no_core) {
  19         return (krate, None);
  20     } else if attr::contains_name(&krate.attrs, sym::no_std) {
  21         if attr::contains_name(&krate.attrs, sym::compiler_builtins) {
  22             &["core"]
  23         } else {
  24             &["core", "compiler_builtins"]
  25         }
  26     } else {
  27         &["std"]
  28     };
  29
  30     // .rev() to preserve ordering above in combination with insert(0, ...)
  31     let alt_std_name = alt_std_name.map(Symbol::intern);
  32     for orig_name_str in names.iter().rev() {
  33         // HACK(eddyb) gensym the injected crates on the Rust 2018 edition,
  34         // so they don't accidentally interfere with the new import paths.
  35         let orig_name_sym = Symbol::intern(orig_name_str);
  36         let orig_name_ident = Ident::with_empty_ctxt(orig_name_sym);
  37         let (rename, orig_name) = if rust_2018 {
  38             (orig_name_ident.gensym(), Some(orig_name_sym))
  39         } else {
  40             (orig_name_ident, None)
  41         };
  42         krate.module.items.insert(0, P(ast::Item {
  43             attrs: vec![attr::mk_attr_outer(
  44                 DUMMY_SP,
  45                 attr::mk_attr_id(),
  46                 attr::mk_word_item(ast::Ident::with_empty_ctxt(sym::macro_use))
  47             )],
  48             vis: dummy_spanned(ast::VisibilityKind::Inherited),
  49             node: ast::ItemKind::ExternCrate(alt_std_name.or(orig_name)),
  50             ident: rename,
  51             id: ast::DUMMY_NODE_ID,
  52             span: DUMMY_SP,
  53             tokens: None,
  54         }));
  55     }
  56
  57     // the crates have been injected, the assumption is that the first one is the one with
  58     // the prelude.
  59     let name = names[0];
  60
  61     let span = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::allow_unstable(
  62         ExpnKind::Macro(MacroKind::Attr, sym::std_inject), DUMMY_SP, edition,
  63         [sym::prelude_import][..].into(),
  64     ));
  65
  66     krate.module.items.insert(0, P(ast::Item {
  67         attrs: vec![ast::Attribute {
  68             style: ast::AttrStyle::Outer,
  69             path: ast::Path::from_ident(ast::Ident::new(sym::prelude_import, span)),
  70             tokens: TokenStream::empty(),
  71             id: attr::mk_attr_id(),
  72             is_sugared_doc: false,
  73             span,
  74         }],
  75         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
  76         node: ast::ItemKind::Use(P(ast::UseTree {
  77             prefix: ast::Path {
  78                 segments: iter::once(ast::Ident::with_empty_ctxt(kw::PathRoot))
  79                     .chain(
  80                         [name, "prelude", "v1"].iter().cloned()
  81                             .map(ast::Ident::from_str)
  82                     ).map(ast::PathSegment::from_ident).collect(),
  83                 span,
  84             },
  85             kind: ast::UseTreeKind::Glob,
  86             span,
  87         })),
  88         id: ast::DUMMY_NODE_ID,
  89         ident: ast::Ident::invalid(),
  90         span,
  91         tokens: None,
  92     }));
  93
  94     (krate, Some(Symbol::intern(name)))
  95 }