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use rustc_ast as ast;
use rustc_expand::base::{ExtCtxt, ResolverExpand};
use rustc_expand::expand::ExpansionConfig;
use rustc_session::Session;
use rustc_span::edition::Edition::*;
use rustc_span::hygiene::AstPass;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::DUMMY_SP;
use thin_vec::thin_vec;
pub fn inject(
mut krate: ast::Crate,
resolver: &mut dyn ResolverExpand,
sess: &Session,
) -> ast::Crate {
let edition = sess.parse_sess.edition;
// the first name in this list is the crate name of the crate with the prelude
let names: &[Symbol] = if sess.contains_name(&krate.attrs, sym::no_core) {
return krate;
} else if sess.contains_name(&krate.attrs, sym::no_std) {
if sess.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.to_expn_id());
let call_site = DUMMY_SP.with_call_site_ctxt(expn_id.to_expn_id());
let ecfg = ExpansionConfig::default("std_lib_injection".to_string());
let cx = ExtCtxt::new(sess, ecfg, resolver, None);
// .rev() to preserve ordering above in combination with insert(0, ...)
for &name in names.iter().rev() {
let ident = if edition >= Edition2018 {
Ident::new(name, span)
} else {
Ident::new(name, call_site)
};
krate.items.insert(
0,
cx.item(
span,
ident,
thin_vec![cx.attr_word(sym::macro_use, span)],
ast::ItemKind::ExternCrate(None),
),
);
}
// The crates have been injected, the assumption is that the first one is
// the one with the prelude.
let name = names[0];
let root = (edition == Edition2015).then_some(kw::PathRoot);
let import_path = root
.iter()
.chain(&[name, sym::prelude])
.chain(&[match edition {
Edition2015 => sym::rust_2015,
Edition2018 => sym::rust_2018,
Edition2021 => sym::rust_2021,
Edition2024 => sym::rust_2024,
}])
.map(|&symbol| Ident::new(symbol, span))
.collect();
let use_item = cx.item(
span,
Ident::empty(),
thin_vec![cx.attr_word(sym::prelude_import, span)],
ast::ItemKind::Use(ast::UseTree {
prefix: cx.path(span, import_path),
kind: ast::UseTreeKind::Glob,
span,
}),
);
krate.items.insert(0, use_item);
krate
}
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