only add builtins if not already included

Don't inject compiler_builtins in the AST

Author: tgross35

compiler/rustc_builtin_macros/src/standard_library_imports.rs

@@ -19,16 +19,12 @@ pub fn inject(
     let edition = sess.psess.edition;
 
     // the first name in this list is the crate name of the crate with the prelude
-    let names: &[Symbol] = if attr::contains_name(pre_configured_attrs, sym::no_core) {
+    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) {
-        if attr::contains_name(pre_configured_attrs, sym::compiler_builtins) {
-            &[sym::core]
-        } else {
-            &[sym::core, sym::compiler_builtins]
-        }
+        sym::core
     } else {
-        &[sym::std]
+        sym::std
     };
 
     let expn_id = resolver.expansion_for_ast_pass(
@@ -43,37 +39,18 @@ pub fn inject(
     let ecfg = ExpansionConfig::default("std_lib_injection".to_string(), features);
     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_span = if edition >= Edition2018 { span } else { call_site };
-        let item = if name == sym::compiler_builtins {
-            // compiler_builtins is a private implementation detail. We only
-            // need to insert it into the crate graph for linking and should not
-            // expose any of its public API.
-            //
-            // FIXME(#113634) We should inject this during post-processing like
-            // we do for the panic runtime, profiler runtime, etc.
-            cx.item(
-                span,
-                Ident::new(kw::Underscore, ident_span),
-                thin_vec![],
-                ast::ItemKind::ExternCrate(Some(name)),
-            )
-        } else {
-            cx.item(
-                span,
-                Ident::new(name, ident_span),
-                thin_vec![cx.attr_word(sym::macro_use, span)],
-                ast::ItemKind::ExternCrate(None),
-            )
-        };
-        krate.items.insert(0, item);
-    }
+    let ident_span = if edition >= Edition2018 { span } else { call_site };
 
-    // The crates have been injected, the assumption is that the first one is
-    // the one with the prelude.
-    let name = names[0];
+    let item = cx.item(
+        span,
+        Ident::new(name, ident_span),
+        thin_vec![cx.attr_word(sym::macro_use, span)],
+        ast::ItemKind::ExternCrate(None),
+    );
+
+    krate.items.insert(0, item);
 
+    // Inject the relevant crate's prelude.
     let root = (edition == Edition2015).then_some(kw::PathRoot);
 
     let import_path = root

compiler/rustc_metadata/messages.ftl

@@ -47,6 +47,9 @@ metadata_crate_dep_rustc_driver =
 metadata_crate_location_unknown_type =
     extern location for {$crate_name} is of an unknown type: {$path}
 
+metadata_crate_not_compiler_builtins =
+    the crate `{$crate_name}` resolved as `compiler_builtins` but is not `#![compiler_builtins]`
+
 metadata_crate_not_panic_runtime =
     the crate `{$crate_name}` is not a panic runtime
 

compiler/rustc_metadata/src/creader.rs

@@ -685,7 +685,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
 
         match result {
             (LoadResult::Previous(cnum), None) => {
-                info!("library for `{}` was loaded previously", name);
+                info!("library for `{}` was loaded previously, cnum {cnum}", name);
                 // When `private_dep` is none, it indicates the directly dependent crate. If it is
                 // not specified by `--extern` on command line parameters, it may be
                 // `private-dependency` when `register_crate` is called for the first time. Then it must be updated to
@@ -1031,6 +1031,39 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         }
     }
 
+    fn inject_compiler_builtins(&mut self, krate: &ast::Crate) {
+        if attr::contains_name(&krate.attrs, sym::compiler_builtins)
+            || attr::contains_name(&krate.attrs, sym::no_core)
+        {
+            // `compiler_builtins` does not get extern builtins, nor do `#![no_core]` crates
+            info!("`compiler_builtins` unneeded");
+            return;
+        }
+
+        for (cnum, cmeta) in self.cstore.iter_crate_data() {
+            if cmeta.is_compiler_builtins() {
+                info!("`compiler_builtins` already exists (cnum = {cnum}); skipping injection");
+                return;
+            }
+        }
+
+        let Ok(cnum) = self.maybe_resolve_crate(
+            sym::compiler_builtins,
+            CrateDepKind::Implicit,
+            CrateOrigin::Injected,
+        ) else {
+            info!("`compiler_builtins` not resolved");
+            return;
+        };
+
+        let cmeta = self.cstore.get_crate_data(cnum);
+
+        // Sanity check the loaded crate to ensure it is indeed compiler_builtins
+        if !cmeta.is_compiler_builtins() {
+            self.dcx().emit_err(errors::CrateNotCompilerBuiltins { crate_name: cmeta.name() });
+        }
+    }
+
     fn inject_dependency_if(
         &mut self,
         krate: CrateNum,
@@ -1140,6 +1173,8 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
     }
 
     pub fn postprocess(&mut self, krate: &ast::Crate) {
+        info!("POSTPROCESS");
+        self.inject_compiler_builtins(krate);
         self.inject_forced_externs();
         self.inject_profiler_runtime();
         self.inject_allocator_crate(krate);
@@ -1171,6 +1206,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
                     }
                     None => item.ident.name,
                 };
+
                 let dep_kind = if attr::contains_name(&item.attrs, sym::no_link) {
                     CrateDepKind::MacrosOnly
                 } else {

compiler/rustc_metadata/src/errors.rs

@@ -332,6 +332,12 @@ pub struct CrateNotPanicRuntime {
     pub crate_name: Symbol,
 }
 
+#[derive(Diagnostic)]
+#[diag(metadata_crate_not_compiler_builtins)]
+pub struct CrateNotCompilerBuiltins {
+    pub crate_name: Symbol,
+}
+
 #[derive(Diagnostic)]
 #[diag(metadata_no_panic_strategy)]
 pub struct NoPanicStrategy {

compiler/rustc_metadata/src/locator.rs

@@ -260,7 +260,7 @@ pub(crate) struct CrateLocator<'a> {
     crate_rejections: CrateRejections,
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub(crate) struct CratePaths {
     pub(crate) name: Symbol,
     source: CrateSource,
@@ -272,7 +272,7 @@ impl CratePaths {
     }
 }
 
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 pub(crate) enum CrateFlavor {
     Rlib,
     Rmeta,
@@ -893,13 +893,13 @@ fn get_flavor_from_path(path: &Path) -> CrateFlavor {
 
 // ------------------------------------------ Error reporting -------------------------------------
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 struct CrateMismatch {
     path: PathBuf,
     got: String,
 }
 
-#[derive(Clone, Default)]
+#[derive(Clone, Debug, Default)]
 struct CrateRejections {
     via_hash: Vec<CrateMismatch>,
     via_triple: Vec<CrateMismatch>,
@@ -912,6 +912,7 @@ struct CrateRejections {
 /// Candidate rejection reasons collected during crate search.
 /// If no candidate is accepted, then these reasons are presented to the user,
 /// otherwise they are ignored.
+#[derive(Debug)]
 pub(crate) struct CombinedLocatorError {
     crate_name: Symbol,
     dep_root: Option<CratePaths>,
@@ -921,6 +922,7 @@ pub(crate) struct CombinedLocatorError {
     crate_rejections: CrateRejections,
 }
 
+#[derive(Debug)]
 pub(crate) enum CrateError {
     NonAsciiName(Symbol),
     ExternLocationNotExist(Symbol, PathBuf),

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1928,6 +1928,10 @@ impl CrateMetadata {
         self.root.profiler_runtime
     }
 
+    pub(crate) fn is_compiler_builtins(&self) -> bool {
+        self.root.compiler_builtins
+    }
+
     pub(crate) fn needs_allocator(&self) -> bool {
         self.root.needs_allocator
     }

compiler/rustc_middle/src/middle/stability.rs

@@ -408,6 +408,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 inspecting def_id={:?} span={:?} of stability={:?}",
             def_id, span, stability
         );
+        tracing::info!("stability table: {:#?}", self.stability());
 
         match stability {
             Some(Stability {

tests/ui/proc-macro/issue-59191-replace-root-with-fn.stderr

@@ -1,4 +1,11 @@
+error: `#[panic_handler]` function required, but not found
+
+error: unwinding panics are not supported without std
+   |
+   = help: using nightly cargo, use -Zbuild-std with panic="abort" to avoid unwinding
+   = note: since the core library is usually precompiled with panic="unwind", rebuilding your crate with panic="abort" may not be enough to fix the problem
+
 error: requires `sized` lang_item
 
-error: aborting due to 1 previous error
+error: aborting due to 3 previous errors
 

tests/ui/proc-macro/meta-macro-hygiene.stdout

@@ -20,7 +20,6 @@ Respanned: TokenStream [Ident { ident: "$crate", span: $DIR/auxiliary/make-macro
 use core /* 0#1 */::prelude /* 0#1 */::rust_2018 /* 0#1 */::*;
 #[macro_use /* 0#1 */]
 extern crate core /* 0#1 */;
-extern crate compiler_builtins /* NNN */ as _ /* 0#1 */;
 // Don't load unnecessary hygiene information from std
 extern crate std /* 0#0 */;
 

tests/ui/proc-macro/nonterminal-token-hygiene.stdout

@@ -39,7 +39,6 @@ PRINT-BANG INPUT (DEBUG): TokenStream [
 use ::core /* 0#1 */::prelude /* 0#1 */::rust_2015 /* 0#1 */::*;
 #[macro_use /* 0#1 */]
 extern crate core /* 0#2 */;
-extern crate compiler_builtins /* NNN */ as _ /* 0#2 */;
 // Don't load unnecessary hygiene information from std
 extern crate std /* 0#0 */;