Move standard library injection into libsyntax_ext

src/librustc/hir/lowering.rs

@@ -63,7 +63,6 @@ use syntax::errors;
 use syntax::ext::hygiene::ExpnId;
 use syntax::print::pprust;
 use syntax::source_map::{respan, ExpnInfo, ExpnKind, DesugaringKind, Spanned};
-use syntax::std_inject;
 use syntax::symbol::{kw, sym, Symbol};
 use syntax::tokenstream::{TokenStream, TokenTree};
 use syntax::parse::token::{self, Token};
@@ -241,7 +240,7 @@ pub fn lower_crate(
     dep_graph.assert_ignored();
 
     LoweringContext {
-        crate_root: std_inject::injected_crate_name().map(Symbol::intern),
+        crate_root: sess.parse_sess.injected_crate_name.try_get().copied(),
         sess,
         cstore,
         resolver,

src/librustc_interface/passes.rs

@@ -278,7 +278,12 @@ pub fn register_plugins<'a>(
 
     krate = time(sess, "crate injection", || {
         let alt_std_name = sess.opts.alt_std_name.as_ref().map(|s| &**s);
-        syntax::std_inject::maybe_inject_crates_ref(krate, alt_std_name, sess.edition())
+        let (krate, name) =
+            syntax_ext::standard_library_imports::inject(krate, alt_std_name, sess.edition());
+        if let Some(name) = name {
+            sess.parse_sess.injected_crate_name.set(name);
+        }
+        krate
     });
 
     let registrars = time(sess, "plugin loading", || {

src/librustc_resolve/build_reduced_graph.rs

@@ -34,7 +34,6 @@ use syntax::ext::hygiene::ExpnId;
 use syntax::feature_gate::is_builtin_attr;
 use syntax::parse::token::{self, Token};
 use syntax::span_err;
-use syntax::std_inject::injected_crate_name;
 use syntax::symbol::{kw, sym};
 use syntax::visit::{self, Visitor};
 
@@ -367,8 +366,10 @@ impl<'a> Resolver<'a> {
                 };
 
                 self.populate_module_if_necessary(module);
-                if injected_crate_name().map_or(false, |name| ident.name.as_str() == name) {
-                    self.injected_crate = Some(module);
+                if let Some(name) = self.session.parse_sess.injected_crate_name.try_get() {
+                    if name.as_str() == ident.name.as_str() {
+                        self.injected_crate = Some(module);
+                    }
                 }
 
                 let used = self.process_legacy_macro_imports(item, module, &parent_scope);

src/libsyntax/lib.rs

@@ -153,7 +153,6 @@ pub mod mut_visit;
 pub mod parse;
 pub mod ptr;
 pub mod show_span;
-pub mod std_inject;
 pub use syntax_pos::edition;
 pub use syntax_pos::symbol;
 pub mod tokenstream;

src/libsyntax/parse/mod.rs

@@ -10,9 +10,10 @@ use crate::parse::token::TokenKind;
 use crate::tokenstream::{TokenStream, TokenTree};
 use crate::diagnostics::plugin::ErrorMap;
 use crate::print::pprust;
+use crate::symbol::Symbol;
 
 use errors::{Applicability, FatalError, Level, Handler, ColorConfig, Diagnostic, DiagnosticBuilder};
-use rustc_data_structures::sync::{Lrc, Lock};
+use rustc_data_structures::sync::{Lrc, Lock, Once};
 use syntax_pos::{Span, SourceFile, FileName, MultiSpan};
 use syntax_pos::edition::Edition;
 
@@ -58,6 +59,7 @@ pub struct ParseSess {
     pub let_chains_spans: Lock<Vec<Span>>,
     // Places where `async || ..` exprs were used and should be feature gated.
     pub async_closure_spans: Lock<Vec<Span>>,
+    pub injected_crate_name: Once<Symbol>,
 }
 
 impl ParseSess {
@@ -86,6 +88,7 @@ impl ParseSess {
             param_attr_spans: Lock::new(Vec::new()),
             let_chains_spans: Lock::new(Vec::new()),
             async_closure_spans: Lock::new(Vec::new()),
+            injected_crate_name: Once::new(),
         }
     }
 

src/libsyntax/print/pprust.rs

@@ -10,7 +10,6 @@ use crate::parse::{self, ParseSess};
 use crate::print::pp::{self, Breaks};
 use crate::print::pp::Breaks::{Consistent, Inconsistent};
 use crate::ptr::P;
-use crate::std_inject;
 use crate::symbol::{kw, sym};
 use crate::tokenstream::{self, TokenStream, TokenTree};
 
@@ -114,7 +113,7 @@ pub fn print_crate<'a>(cm: &'a SourceMap,
         is_expanded,
     };
 
-    if is_expanded && std_inject::injected_crate_name().is_some() {
+    if is_expanded && sess.injected_crate_name.try_get().is_some() {
         // We need to print `#![no_std]` (and its feature gate) so that
         // compiling pretty-printed source won't inject libstd again.
         // However we don't want these attributes in the AST because

src/libsyntax_ext/lib.rs

@@ -43,6 +43,7 @@ mod trace_macros;
 
 pub mod plugin_macro_defs;
 pub mod proc_macro_decls;
+pub mod standard_library_imports;
 pub mod test_harness;
 
 pub fn register_builtin_macros(resolver: &mut dyn syntax::ext::base::Resolver, edition: Edition) {

src/libsyntax/std_inject.rs → src/libsyntax_ext/standard_library_imports.rs

@@ -1,37 +1,22 @@
-use crate::ast;
-use crate::attr;
-use crate::edition::Edition;
-use crate::ext::hygiene::{ExpnId, MacroKind};
-use crate::symbol::{Ident, Symbol, kw, sym};
-use crate::source_map::{ExpnInfo, ExpnKind, dummy_spanned, respan};
-use crate::ptr::P;
-use crate::tokenstream::TokenStream;
-
-use std::cell::Cell;
-use std::iter;
+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::tokenstream::TokenStream;
 use syntax_pos::DUMMY_SP;
 
-pub fn injected_crate_name() -> Option<&'static str> {
-    INJECTED_CRATE_NAME.with(|name| name.get())
-}
-
-thread_local! {
-    // A `Symbol` might make more sense here, but it doesn't work, probably for
-    // reasons relating to the use of thread-local storage for the Symbol
-    // interner.
-    static INJECTED_CRATE_NAME: Cell<Option<&'static str>> = Cell::new(None);
-}
+use std::iter;
 
-pub fn maybe_inject_crates_ref(
-    mut krate: ast::Crate,
-    alt_std_name: Option<&str>,
-    edition: Edition,
-) -> ast::Crate {
+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;
+        return (krate, None);
     } else if attr::contains_name(&krate.attrs, sym::no_std) {
         if attr::contains_name(&krate.attrs, sym::compiler_builtins) {
             &["core"]
@@ -73,8 +58,6 @@ pub fn maybe_inject_crates_ref(
     // the prelude.
     let name = names[0];
 
-    INJECTED_CRATE_NAME.with(|opt_name| opt_name.set(Some(name)));
-
     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(),
@@ -108,5 +91,5 @@ pub fn maybe_inject_crates_ref(
         tokens: None,
     }));
 
-    krate
+    (krate, Some(Symbol::intern(name)))
 }