Add a list of symbols for stable standard library crates

There are a few locations where the crate name is checked against an
enumerated list of `std`, `core`, `alloc`, and `proc_macro`, or some
subset thereof. In most of these cases, all four crates should likely be
treated the same. Change this so the crates are listed in one place, and
that list is used wherever a list of `std` crates is needed.

`test` could be considered relevant in some of these cases, but
generally treating it separate from the others seems preferable while it
is unstable.

There are also a few places that Clippy will be able to use this.

compiler/rustc_expand/src/config.rs

@@ -18,7 +18,7 @@ use rustc_lint_defs::BuiltinLintDiag;
 use rustc_parse::validate_attr;
 use rustc_session::Session;
 use rustc_session::parse::feature_err;
-use rustc_span::{Span, Symbol, sym};
+use rustc_span::{STDLIB_STABLE_CRATES, Span, Symbol, sym};
 use thin_vec::ThinVec;
 use tracing::instrument;
 
@@ -107,14 +107,11 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -
 
             // If the enabled feature is unstable, record it.
             if UNSTABLE_LANG_FEATURES.iter().find(|f| name == f.name).is_some() {
-                // When the ICE comes from core, alloc or std (approximation of the standard
-                // library), there's a chance that the person hitting the ICE may be using
-                // -Zbuild-std or similar with an untested target. The bug is probably in the
-                // standard library and not the compiler in that case, but that doesn't really
-                // matter - we want a bug report.
-                if features.internal(name)
-                    && ![sym::core, sym::alloc, sym::std].contains(&crate_name)
-                {
+                // When the ICE comes a standard library crate, there's a chance that the person
+                // hitting the ICE may be using -Zbuild-std or similar with an untested target.
+                // The bug is probably in the standard library and not the compiler in that case,
+                // but that doesn't really matter - we want a bug report.
+                if features.internal(name) && !STDLIB_STABLE_CRATES.contains(&crate_name) {
                     sess.using_internal_features.store(true, std::sync::atomic::Ordering::Relaxed);
                 }
 
@@ -133,7 +130,7 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute], crate_name: Symbol) -
 
             // Similar to above, detect internal lib features to suppress
             // the ICE message that asks for a report.
-            if features.internal(name) && ![sym::core, sym::alloc, sym::std].contains(&crate_name) {
+            if features.internal(name) && !STDLIB_STABLE_CRATES.contains(&crate_name) {
                 sess.using_internal_features.store(true, std::sync::atomic::Ordering::Relaxed);
             }
         }

compiler/rustc_hir_typeck/src/method/prelude_edition_lints.rs

@@ -8,7 +8,7 @@ use rustc_lint::{ARRAY_INTO_ITER, BOXED_SLICE_INTO_ITER};
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, Ty};
 use rustc_session::lint::builtin::{RUST_2021_PRELUDE_COLLISIONS, RUST_2024_PRELUDE_COLLISIONS};
-use rustc_span::{Ident, Span, kw, sym};
+use rustc_span::{Ident, STDLIB_STABLE_CRATES, Span, kw, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use tracing::debug;
 
@@ -76,7 +76,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         // No need to lint if method came from std/core, as that will now be in the prelude
-        if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) {
+        if STDLIB_STABLE_CRATES.contains(&self.tcx.crate_name(pick.item.def_id.krate)) {
             return;
         }
 
@@ -252,7 +252,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         // No need to lint if method came from std/core, as that will now be in the prelude
-        if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) {
+        if STDLIB_STABLE_CRATES.contains(&self.tcx.crate_name(pick.item.def_id.krate)) {
             return;
         }
 

compiler/rustc_span/src/lib.rs

@@ -67,7 +67,7 @@ mod span_encoding;
 pub use span_encoding::{DUMMY_SP, Span};
 
 pub mod symbol;
-pub use symbol::{Ident, MacroRulesNormalizedIdent, Symbol, kw, sym};
+pub use symbol::{Ident, MacroRulesNormalizedIdent, STDLIB_STABLE_CRATES, Symbol, kw, sym};
 
 mod analyze_source_file;
 pub mod fatal_error;

compiler/rustc_span/src/symbol.rs

@@ -2240,6 +2240,10 @@ symbols! {
     }
 }
 
+/// Symbols for crates that are part of the stable standard library: `std`, `core`, `alloc`, and
+/// `proc_macro`.
+pub const STDLIB_STABLE_CRATES: &[Symbol] = &[sym::std, sym::core, sym::alloc, sym::proc_macro];
+
 #[derive(Copy, Clone, Eq, HashStable_Generic, Encodable, Decodable)]
 pub struct Ident {
     pub name: Symbol,

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -27,7 +27,7 @@ use rustc_middle::ty::{
     self, ToPolyTraitRef, TraitRef, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, Upcast,
 };
 use rustc_middle::{bug, span_bug};
-use rustc_span::{BytePos, DUMMY_SP, Span, Symbol, sym};
+use rustc_span::{BytePos, DUMMY_SP, STDLIB_STABLE_CRATES, Span, Symbol, sym};
 use tracing::{debug, instrument};
 
 use super::on_unimplemented::{AppendConstMessage, OnUnimplementedNote};
@@ -520,7 +520,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             match obligation.cause.span.ctxt().outer_expn_data().macro_def_id {
                                 Some(macro_def_id) => {
                                     let crate_name = tcx.crate_name(macro_def_id.krate);
-                                    crate_name == sym::std || crate_name == sym::core
+                                    STDLIB_STABLE_CRATES.contains(&crate_name)
                                 }
                                 None => false,
                             };