Partially revert ed63539 ("Mark dependencies ... private by default")

Remove the portion of ed63539 that automatically sets crates private
based on whether they are dependencies of `std`. Instead, this is
controlled by dependency configuration in `Cargo.toml`.

Author: tgross35

compiler/rustc_metadata/src/creader.rs

@@ -29,7 +29,7 @@ use rustc_session::lint::{self, BuiltinLintDiag};
 use rustc_session::output::validate_crate_name;
 use rustc_session::search_paths::PathKind;
 use rustc_span::edition::Edition;
-use rustc_span::{DUMMY_SP, Ident, STDLIB_STABLE_CRATES, Span, Symbol, sym};
+use rustc_span::{DUMMY_SP, Ident, Span, Symbol, sym};
 use rustc_target::spec::{PanicStrategy, Target, TargetTuple};
 use tracing::{debug, info, trace};
 
@@ -400,29 +400,8 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
     /// Sometimes the directly dependent crate is not specified by `--extern`, in this case,
     /// `private-dep` is none during loading. This is equivalent to the scenario where the
     /// command parameter is set to `public-dependency`
-    fn is_private_dep(
-        &self,
-        name: Symbol,
-        private_dep: Option<bool>,
-        dep_root: Option<&CratePaths>,
-    ) -> bool {
-        // Standard library crates are never private.
-        if STDLIB_STABLE_CRATES.contains(&name) {
-            tracing::info!("returning false for {name} is private");
-            return false;
-        }
-
+    fn is_private_dep(&self, name: Symbol, private_dep: Option<bool>) -> bool {
         let extern_private = self.sess.opts.externs.get(name.as_str()).map(|e| e.is_private_dep);
-
-        // Any descendants of `std` should be private. These crates are usually not marked
-        // private in metadata, so we ignore that field.
-        if extern_private.is_none()
-            && let Some(dep) = dep_root
-            && STDLIB_STABLE_CRATES.contains(&dep.name)
-        {
-            return true;
-        }
-
         match (extern_private, private_dep) {
             // Explicit non-private via `--extern`, explicit non-private from metadata, or
             // unspecified with default to public.
@@ -447,7 +426,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
         let Library { source, metadata } = lib;
         let crate_root = metadata.get_root();
         let host_hash = host_lib.as_ref().map(|lib| lib.metadata.get_root().hash());
-        let private_dep = self.is_private_dep(name, private_dep, dep_root);
+        let private_dep = self.is_private_dep(name, private_dep);
 
         // Claim this crate number and cache it
         let feed = self.cstore.intern_stable_crate_id(&crate_root, self.tcx)?;
@@ -643,7 +622,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
                 // 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
                 // `public-dependency` here.
-                let private_dep = self.is_private_dep(name, private_dep, dep_root);
+                let private_dep = self.is_private_dep(name, private_dep);
                 let data = self.cstore.get_crate_data_mut(cnum);
                 if data.is_proc_macro_crate() {
                     dep_kind = CrateDepKind::MacrosOnly;