src/libsyntax/std_inject.rs

   1 use crate::ast;
   2 use crate::attr;
   3 use crate::edition::Edition;
   4 use crate::ext::hygiene::{Mark, SyntaxContext};
   5 use crate::symbol::{Symbol, keywords};
   6 use crate::source_map::{ExpnInfo, MacroAttribute, dummy_spanned, hygiene, 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, Span};
  13
  14 /// Craft a span that will be ignored by the stability lint's
  15 /// call to source_map's `is_internal` check.
  16 /// The expanded code uses the unstable `#[prelude_import]` attribute.
  17 fn ignored_span(sp: Span) -> Span {
  18     let mark = Mark::fresh(Mark::root());
  19     mark.set_expn_info(ExpnInfo {
  20         call_site: DUMMY_SP,
  21         def_site: None,
  22         format: MacroAttribute(Symbol::intern("std_inject")),
  23         allow_internal_unstable: Some(vec![
  24             Symbol::intern("prelude_import"),
  25         ].into()),
  26         allow_internal_unsafe: false,
  27         local_inner_macros: false,
  28         edition: hygiene::default_edition(),
  29     });
  30     sp.with_ctxt(SyntaxContext::empty().apply_mark(mark))
  31 }
  32
  33 pub fn injected_crate_name() -> Option<&'static str> {
  34     INJECTED_CRATE_NAME.with(|name| name.get())
  35 }
  36
  37 thread_local! {
  38     static INJECTED_CRATE_NAME: Cell<Option<&'static str>> = Cell::new(None);
  39 }
  40
  41 pub fn maybe_inject_crates_ref(
  42     mut krate: ast::Crate,
  43     alt_std_name: Option<&str>,
  44     edition: Edition,
  45 ) -> ast::Crate {
  46     let rust_2018 = edition >= Edition::Edition2018;
  47
  48     // the first name in this list is the crate name of the crate with the prelude
  49     let names: &[&str] = if attr::contains_name(&krate.attrs, "no_core") {
  50         return krate;
  51     } else if attr::contains_name(&krate.attrs, "no_std") {
  52         if attr::contains_name(&krate.attrs, "compiler_builtins") {
  53             &["core"]
  54         } else {
  55             &["core", "compiler_builtins"]
  56         }
  57     } else {
  58         &["std"]
  59     };
  60
  61     // .rev() to preserve ordering above in combination with insert(0, ...)
  62     let alt_std_name = alt_std_name.map(Symbol::intern);
  63     for orig_name in names.iter().rev() {
  64         let orig_name = Symbol::intern(orig_name);
  65         let mut rename = orig_name;
  66         // HACK(eddyb) gensym the injected crates on the Rust 2018 edition,
  67         // so they don't accidentally interfere with the new import paths.
  68         if rust_2018 {
  69             rename = orig_name.gensymed();
  70         }
  71         let orig_name = if rename != orig_name {
  72             Some(orig_name)
  73         } else {
  74             None
  75         };
  76         krate.module.items.insert(0, P(ast::Item {
  77             attrs: vec![attr::mk_attr_outer(DUMMY_SP,
  78                                             attr::mk_attr_id(),
  79                                             attr::mk_word_item(ast::Ident::from_str("macro_use")))],
  80             vis: dummy_spanned(ast::VisibilityKind::Inherited),
  81             node: ast::ItemKind::ExternCrate(alt_std_name.or(orig_name)),
  82             ident: ast::Ident::with_empty_ctxt(rename),
  83             id: ast::DUMMY_NODE_ID,
  84             span: DUMMY_SP,
  85             tokens: None,
  86         }));
  87     }
  88
  89     // the crates have been injected, the assumption is that the first one is the one with
  90     // the prelude.
  91     let name = names[0];
  92
  93     INJECTED_CRATE_NAME.with(|opt_name| opt_name.set(Some(name)));
  94
  95     let span = ignored_span(DUMMY_SP);
  96     krate.module.items.insert(0, P(ast::Item {
  97         attrs: vec![ast::Attribute {
  98             style: ast::AttrStyle::Outer,
  99             path: ast::Path::from_ident(ast::Ident::new(Symbol::intern("prelude_import"), span)),
 100             tokens: TokenStream::empty(),
 101             id: attr::mk_attr_id(),
 102             is_sugared_doc: false,
 103             span,
 104         }],
 105         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
 106         node: ast::ItemKind::Use(P(ast::UseTree {
 107             prefix: ast::Path {
 108                 segments: iter::once(keywords::PathRoot.ident())
 109                     .chain(
 110                         [name, "prelude", "v1"].iter().cloned()
 111                             .map(ast::Ident::from_str)
 112                     ).map(ast::PathSegment::from_ident).collect(),
 113                 span,
 114             },
 115             kind: ast::UseTreeKind::Glob,
 116             span,
 117         })),
 118         id: ast::DUMMY_NODE_ID,
 119         ident: keywords::Invalid.ident(),
 120         span,
 121         tokens: None,
 122     }));
 123
 124     krate
 125 }