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use syntax::{ast, attr};
use syntax::edition::Edition;
use syntax::ext::expand::ExpansionConfig;
use syntax::ext::hygiene::AstPass;
use syntax::ext::base::{ExtCtxt, Resolver};
use syntax::parse::ParseSess;
use syntax::ptr::P;
use syntax::symbol::{Ident, Symbol, kw, sym};
use syntax_pos::DUMMY_SP;
pub fn inject(
mut krate: ast::Crate,
resolver: &mut dyn Resolver,
sess: &ParseSess,
alt_std_name: Option<Symbol>,
) -> (ast::Crate, Option<Symbol>) {
let rust_2018 = sess.edition >= Edition::Edition2018;
// the first name in this list is the crate name of the crate with the prelude
let names: &[Symbol] = 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) {
&[sym::core]
} else {
&[sym::core, sym::compiler_builtins]
}
} else {
&[sym::std]
};
let expn_id = resolver.expansion_for_ast_pass(
DUMMY_SP,
AstPass::StdImports,
&[sym::prelude_import],
None,
);
let span = DUMMY_SP.with_def_site_ctxt(expn_id);
let call_site = DUMMY_SP.with_call_site_ctxt(expn_id);
let ecfg = ExpansionConfig::default("std_lib_injection".to_string());
let cx = ExtCtxt::new(sess, ecfg, resolver);
// .rev() to preserve ordering above in combination with insert(0, ...)
for &name in names.iter().rev() {
let ident = if rust_2018 {
Ident::new(name, span)
} else {
Ident::new(name, call_site)
};
krate.module.items.insert(0, cx.item(
span,
ident,
vec![cx.attribute(cx.meta_word(span, sym::macro_use))],
ast::ItemKind::ExternCrate(alt_std_name),
));
}
// The crates have been injected, the assumption is that the first one is
// the one with the prelude.
let name = names[0];
let import_path = if rust_2018 {
[name, sym::prelude, sym::v1].iter()
.map(|symbol| ast::Ident::new(*symbol, span)).collect()
} else {
[kw::PathRoot, name, sym::prelude, sym::v1].iter()
.map(|symbol| ast::Ident::new(*symbol, span)).collect()
};
let use_item = cx.item(
span,
ast::Ident::invalid(),
vec![cx.attribute(cx.meta_word(span, sym::prelude_import))],
ast::ItemKind::Use(P(ast::UseTree {
prefix: cx.path(span, import_path),
kind: ast::UseTreeKind::Glob,
span,
})),
);
krate.module.items.insert(0, use_item);
(krate, Some(name))
}
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