Rollup merge of #138682 - Alexendoo:extra-symbols, r=fee1-dead

Allow drivers to supply a list of extra symbols to intern

Allows adding new symbols as `const`s in external drivers, desirable in Clippy so we can use them in patterns to replace code like 75530e9f72/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs (L66)

The Clippy change adds a couple symbols as a demo, the exact `clippy_utils` API and replacing other usages can be done on the Clippy side to minimise sync conflicts

---

try-job: aarch64-gnu

compiler/rustc_span/src/lib.rs

@@ -116,9 +116,13 @@ pub struct SessionGlobals {
 }
 
 impl SessionGlobals {
-    pub fn new(edition: Edition, sm_inputs: Option<SourceMapInputs>) -> SessionGlobals {
+    pub fn new(
+        edition: Edition,
+        extra_symbols: &[&'static str],
+        sm_inputs: Option<SourceMapInputs>,
+    ) -> SessionGlobals {
         SessionGlobals {
-            symbol_interner: symbol::Interner::fresh(),
+            symbol_interner: symbol::Interner::with_extra_symbols(extra_symbols),
             span_interner: Lock::new(span_encoding::SpanInterner::default()),
             metavar_spans: Default::default(),
             hygiene_data: Lock::new(hygiene::HygieneData::new(edition)),
@@ -129,6 +133,7 @@ impl SessionGlobals {
 
 pub fn create_session_globals_then<R>(
     edition: Edition,
+    extra_symbols: &[&'static str],
     sm_inputs: Option<SourceMapInputs>,
     f: impl FnOnce() -> R,
 ) -> R {
@@ -137,7 +142,7 @@ pub fn create_session_globals_then<R>(
         "SESSION_GLOBALS should never be overwritten! \
          Use another thread if you need another SessionGlobals"
     );
-    let session_globals = SessionGlobals::new(edition, sm_inputs);
+    let session_globals = SessionGlobals::new(edition, extra_symbols, sm_inputs);
     SESSION_GLOBALS.set(&session_globals, f)
 }
 
@@ -156,7 +161,7 @@ where
     F: FnOnce(&SessionGlobals) -> R,
 {
     if !SESSION_GLOBALS.is_set() {
-        let session_globals = SessionGlobals::new(edition, None);
+        let session_globals = SessionGlobals::new(edition, &[], None);
         SESSION_GLOBALS.set(&session_globals, || SESSION_GLOBALS.with(f))
     } else {
         SESSION_GLOBALS.with(f)
@@ -172,7 +177,7 @@ where
 
 /// Default edition, no source map.
 pub fn create_default_session_globals_then<R>(f: impl FnOnce() -> R) -> R {
-    create_session_globals_then(edition::DEFAULT_EDITION, None, f)
+    create_session_globals_then(edition::DEFAULT_EDITION, &[], None, f)
 }
 
 // If this ever becomes non thread-local, `decode_syntax_context`

compiler/rustc_span/src/symbol.rs

@@ -2540,15 +2540,10 @@ rustc_index::newtype_index! {
 }
 
 impl Symbol {
-    const fn new(n: u32) -> Self {
+    pub const fn new(n: u32) -> Self {
         Symbol(SymbolIndex::from_u32(n))
     }
 
-    /// for use in Decoder only
-    pub fn new_from_decoded(n: u32) -> Self {
-        Self::new(n)
-    }
-
     /// Maps a string to its interned representation.
     #[rustc_diagnostic_item = "SymbolIntern"]
     pub fn intern(string: &str) -> Self {
@@ -2634,11 +2629,14 @@ struct InternerInner {
 }
 
 impl Interner {
-    fn prefill(init: &[&'static str]) -> Self {
-        Interner(Lock::new(InternerInner {
-            arena: Default::default(),
-            strings: init.iter().copied().collect(),
-        }))
+    fn prefill(init: &[&'static str], extra: &[&'static str]) -> Self {
+        let strings = FxIndexSet::from_iter(init.iter().copied().chain(extra.iter().copied()));
+        assert_eq!(
+            strings.len(),
+            init.len() + extra.len(),
+            "`init` or `extra` contain duplicate symbols",
+        );
+        Interner(Lock::new(InternerInner { arena: Default::default(), strings }))
     }
 
     #[inline]
@@ -2762,9 +2760,9 @@ impl Symbol {
         self != kw::Empty && self != kw::Underscore && !self.is_path_segment_keyword()
     }
 
-    /// Is this symbol was interned in compiler's `symbols!` macro
-    pub fn is_preinterned(self) -> bool {
-        self.as_u32() < PREINTERNED_SYMBOLS_COUNT
+    /// Was this symbol predefined in the compiler's `symbols!` macro
+    pub fn is_predefined(self) -> bool {
+        self.as_u32() < PREDEFINED_SYMBOLS_COUNT
     }
 }
 

compiler/rustc_span/src/symbol/tests.rs

@@ -3,7 +3,7 @@ use crate::create_default_session_globals_then;
 
 #[test]
 fn interner_tests() {
-    let i = Interner::prefill(&[]);
+    let i = Interner::prefill(&[], &[]);
     // first one is zero:
     assert_eq!(i.intern("dog"), Symbol::new(0));
     // re-use gets the same entry: