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use rustc_ast::{self as ast, attr};
use rustc_expand::base::{ExtCtxt, ResolverExpand};
use rustc_expand::expand::ExpansionConfig;
use rustc_feature::Features;
use rustc_session::Session;
use rustc_span::edition::Edition::*;
use rustc_span::hygiene::AstPass;
use rustc_span::{DUMMY_SP, Ident, Symbol, kw, sym};
use thin_vec::thin_vec;
pub fn inject(
krate: &mut ast::Crate,
pre_configured_attrs: &[ast::Attribute],
resolver: &mut dyn ResolverExpand,
sess: &Session,
features: &Features,
) -> usize {
let orig_num_items = krate.items.len();
let edition = sess.psess.edition;
// the first name in this list is the crate name of the crate with the prelude
let name: Symbol = if attr::contains_name(pre_configured_attrs, sym::no_core) {
return 0;
} else if attr::contains_name(pre_configured_attrs, sym::no_std) {
sym::core
} 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(sym::std_lib_injection, features);
let cx = ExtCtxt::new(sess, ecfg, resolver, None);
let ident_span = if edition >= Edition2018 { span } else { call_site };
let item = cx.item(
span,
thin_vec![cx.attr_word(sym::macro_use, span)],
ast::ItemKind::ExternCrate(None, Ident::new(name, ident_span)),
);
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,
EditionFuture => sym::rust_future,
}])
.map(|&symbol| Ident::new(symbol, span))
.collect();
// Inject the relevant crate's prelude.
let use_item = cx.item(
span,
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.splice(0..0, [item, use_item]);
krate.items.len() - orig_num_items
}
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