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use syntax::{ast, attr};
use syntax::edition::Edition;
use syntax::ext::hygiene::{ExpnId, MacroKind};
use syntax::ptr::P;
use syntax::source_map::{ExpnInfo, ExpnKind, dummy_spanned, respan};
use syntax::symbol::{Ident, Symbol, kw, sym};
use syntax_pos::DUMMY_SP;
use std::iter;
pub fn inject(
mut krate: ast::Crate, alt_std_name: Option<&str>, edition: Edition
) -> (ast::Crate, Option<Symbol>) {
let rust_2018 = edition >= Edition::Edition2018;
// the first name in this list is the crate name of the crate with the prelude
let names: &[&str] = if attr::contains_name(&krate.attrs, sym::no_core) {
return (krate, None);
} else if attr::contains_name(&krate.attrs, sym::no_std) {
if attr::contains_name(&krate.attrs, sym::compiler_builtins) {
&["core"]
} else {
&["core", "compiler_builtins"]
}
} else {
&["std"]
};
// .rev() to preserve ordering above in combination with insert(0, ...)
let alt_std_name = alt_std_name.map(Symbol::intern);
for orig_name_str in names.iter().rev() {
// HACK(eddyb) gensym the injected crates on the Rust 2018 edition,
// so they don't accidentally interfere with the new import paths.
let orig_name_sym = Symbol::intern(orig_name_str);
let orig_name_ident = Ident::with_empty_ctxt(orig_name_sym);
let (rename, orig_name) = if rust_2018 {
(orig_name_ident.gensym(), Some(orig_name_sym))
} else {
(orig_name_ident, None)
};
krate.module.items.insert(0, P(ast::Item {
attrs: vec![attr::mk_attr_outer(
attr::mk_word_item(ast::Ident::with_empty_ctxt(sym::macro_use))
)],
vis: dummy_spanned(ast::VisibilityKind::Inherited),
node: ast::ItemKind::ExternCrate(alt_std_name.or(orig_name)),
ident: rename,
id: ast::DUMMY_NODE_ID,
span: DUMMY_SP,
tokens: None,
}));
}
// the crates have been injected, the assumption is that the first one is the one with
// the prelude.
let name = names[0];
let span = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::allow_unstable(
ExpnKind::Macro(MacroKind::Attr, sym::std_inject), DUMMY_SP, edition,
[sym::prelude_import][..].into(),
));
krate.module.items.insert(0, P(ast::Item {
attrs: vec![attr::mk_attr_outer(
attr::mk_word_item(ast::Ident::new(sym::prelude_import, span)))],
vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
node: ast::ItemKind::Use(P(ast::UseTree {
prefix: ast::Path {
segments: iter::once(ast::Ident::with_empty_ctxt(kw::PathRoot))
.chain(
[name, "prelude", "v1"].iter().cloned()
.map(ast::Ident::from_str)
).map(ast::PathSegment::from_ident).collect(),
span,
},
kind: ast::UseTreeKind::Glob,
span,
})),
id: ast::DUMMY_NODE_ID,
ident: ast::Ident::invalid(),
span,
tokens: None,
}));
(krate, Some(Symbol::intern(name)))
}
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