src/libsyntax/std_inject.rs

   1 use crate::ast;
   2 use crate::attr;
   3 use crate::edition::Edition;
   4 use crate::ext::hygiene::{ExpnId, MacroKind};
   5 use crate::symbol::{Ident, Symbol, kw, sym};
   6 use crate::source_map::{ExpnInfo, ExpnKind, dummy_spanned, respan};
   7 use crate::ptr::P;
   8 use crate::tokenstream::TokenStream;
   9
  10 use std::cell::Cell;
  11 use std::iter;
  12 use syntax_pos::DUMMY_SP;
  13
  14 pub fn injected_crate_name() -> Option<&'static str> {
  15     INJECTED_CRATE_NAME.with(|name| name.get())
  16 }
  17
  18 thread_local! {
  19     // A `Symbol` might make more sense here, but it doesn't work, probably for
  20     // reasons relating to the use of thread-local storage for the Symbol
  21     // interner.
  22     static INJECTED_CRATE_NAME: Cell<Option<&'static str>> = Cell::new(None);
  23 }
  24
  25 pub fn maybe_inject_crates_ref(
  26     mut krate: ast::Crate,
  27     alt_std_name: Option<&str>,
  28     edition: Edition,
  29 ) -> ast::Crate {
  30     let rust_2018 = edition >= Edition::Edition2018;
  31
  32     // the first name in this list is the crate name of the crate with the prelude
  33     let names: &[&str] = if attr::contains_name(&krate.attrs, sym::no_core) {
  34         return krate;
  35     } else if attr::contains_name(&krate.attrs, sym::no_std) {
  36         if attr::contains_name(&krate.attrs, sym::compiler_builtins) {
  37             &["core"]
  38         } else {
  39             &["core", "compiler_builtins"]
  40         }
  41     } else {
  42         &["std"]
  43     };
  44
  45     // .rev() to preserve ordering above in combination with insert(0, ...)
  46     let alt_std_name = alt_std_name.map(Symbol::intern);
  47     for orig_name_str in names.iter().rev() {
  48         // HACK(eddyb) gensym the injected crates on the Rust 2018 edition,
  49         // so they don't accidentally interfere with the new import paths.
  50         let orig_name_sym = Symbol::intern(orig_name_str);
  51         let orig_name_ident = Ident::with_empty_ctxt(orig_name_sym);
  52         let (rename, orig_name) = if rust_2018 {
  53             (orig_name_ident.gensym(), Some(orig_name_sym))
  54         } else {
  55             (orig_name_ident, None)
  56         };
  57         krate.module.items.insert(0, P(ast::Item {
  58             attrs: vec![attr::mk_attr_outer(
  59                 DUMMY_SP,
  60                 attr::mk_attr_id(),
  61                 attr::mk_word_item(ast::Ident::with_empty_ctxt(sym::macro_use))
  62             )],
  63             vis: dummy_spanned(ast::VisibilityKind::Inherited),
  64             node: ast::ItemKind::ExternCrate(alt_std_name.or(orig_name)),
  65             ident: rename,
  66             id: ast::DUMMY_NODE_ID,
  67             span: DUMMY_SP,
  68             tokens: None,
  69         }));
  70     }
  71
  72     // the crates have been injected, the assumption is that the first one is the one with
  73     // the prelude.
  74     let name = names[0];
  75
  76     INJECTED_CRATE_NAME.with(|opt_name| opt_name.set(Some(name)));
  77
  78     let span = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::allow_unstable(
  79         ExpnKind::Macro(MacroKind::Attr, sym::std_inject), DUMMY_SP, edition,
  80         [sym::prelude_import][..].into(),
  81     ));
  82
  83     krate.module.items.insert(0, P(ast::Item {
  84         attrs: vec![ast::Attribute {
  85             style: ast::AttrStyle::Outer,
  86             path: ast::Path::from_ident(ast::Ident::new(sym::prelude_import, span)),
  87             tokens: TokenStream::empty(),
  88             id: attr::mk_attr_id(),
  89             is_sugared_doc: false,
  90             span,
  91         }],
  92         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
  93         node: ast::ItemKind::Use(P(ast::UseTree {
  94             prefix: ast::Path {
  95                 segments: iter::once(ast::Ident::with_empty_ctxt(kw::PathRoot))
  96                     .chain(
  97                         [name, "prelude", "v1"].iter().cloned()
  98                             .map(ast::Ident::from_str)
  99                     ).map(ast::PathSegment::from_ident).collect(),
 100                 span,
 101             },
 102             kind: ast::UseTreeKind::Glob,
 103             span,
 104         })),
 105         id: ast::DUMMY_NODE_ID,
 106         ident: ast::Ident::invalid(),
 107         span,
 108         tokens: None,
 109     }));
 110
 111     krate
 112 }