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c56f49dc34
Use `splice` to avoid shifting the other items twice. Put `extern crate std;` first so it's already resolved when we resolve `::std::prelude::rust_20XX`.
79 lines
2.4 KiB
Rust
79 lines
2.4 KiB
Rust
use rustc_ast::{self as ast, attr};
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use rustc_expand::base::{ExtCtxt, ResolverExpand};
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use rustc_expand::expand::ExpansionConfig;
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use rustc_feature::Features;
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use rustc_session::Session;
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use rustc_span::edition::Edition::*;
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use rustc_span::hygiene::AstPass;
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use rustc_span::{DUMMY_SP, Ident, Symbol, kw, sym};
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use thin_vec::thin_vec;
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pub fn inject(
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krate: &mut ast::Crate,
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pre_configured_attrs: &[ast::Attribute],
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resolver: &mut dyn ResolverExpand,
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sess: &Session,
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features: &Features,
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) -> usize {
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let orig_num_items = krate.items.len();
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let edition = sess.psess.edition;
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// the first name in this list is the crate name of the crate with the prelude
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let name: Symbol = if attr::contains_name(pre_configured_attrs, sym::no_core) {
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return 0;
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} else if attr::contains_name(pre_configured_attrs, sym::no_std) {
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sym::core
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} else {
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sym::std
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};
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let expn_id = resolver.expansion_for_ast_pass(
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DUMMY_SP,
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AstPass::StdImports,
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&[sym::prelude_import],
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None,
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);
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let span = DUMMY_SP.with_def_site_ctxt(expn_id.to_expn_id());
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let call_site = DUMMY_SP.with_call_site_ctxt(expn_id.to_expn_id());
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let ecfg = ExpansionConfig::default(sym::std_lib_injection, features);
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let cx = ExtCtxt::new(sess, ecfg, resolver, None);
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let ident_span = if edition >= Edition2018 { span } else { call_site };
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let item = cx.item(
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span,
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thin_vec![cx.attr_word(sym::macro_use, span)],
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ast::ItemKind::ExternCrate(None, Ident::new(name, ident_span)),
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);
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let root = (edition == Edition2015).then_some(kw::PathRoot);
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let import_path = root
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.iter()
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.chain(&[name, sym::prelude])
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.chain(&[match edition {
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Edition2015 => sym::rust_2015,
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Edition2018 => sym::rust_2018,
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Edition2021 => sym::rust_2021,
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Edition2024 => sym::rust_2024,
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EditionFuture => sym::rust_future,
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}])
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.map(|&symbol| Ident::new(symbol, span))
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.collect();
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// Inject the relevant crate's prelude.
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let use_item = cx.item(
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span,
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thin_vec![cx.attr_word(sym::prelude_import, span)],
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ast::ItemKind::Use(ast::UseTree {
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prefix: cx.path(span, import_path),
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kind: ast::UseTreeKind::Glob,
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span,
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}),
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);
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krate.items.splice(0..0, [item, use_item]);
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krate.items.len() - orig_num_items
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}
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