Auto merge of #60827 - oli-obk:late_symbol, r=nnethercote

Use `Symbol` more in lint APIs

r? @nnethercote

This will cause clippy breakage, but super trivial to fix since we can then remove the hacky `match_def_path` function that I added and go back to calling rustc's `match_def_path` method.

src/librustc/lint/context.rs

@@ -759,27 +759,27 @@ pub fn current_lint_root(&self) -> hir::HirId {
     /// # Examples
     ///
     /// ```rust,ignore (no context or def id available)
-    /// if cx.match_def_path(def_id, &["core", "option", "Option"]) {
+    /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
     ///     // The given `def_id` is that of an `Option` type
     /// }
     /// ```
-    pub fn match_def_path(&self, def_id: DefId, path: &[&str]) -> bool {
+    pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
         let names = self.get_def_path(def_id);
 
-        names.len() == path.len() && names.into_iter().zip(path.iter()).all(|(a, &b)| *a == *b)
+        names.len() == path.len() && names.into_iter().zip(path.iter()).all(|(a, &b)| a == b)
     }
 
-    /// Gets the absolute path of `def_id` as a vector of `&str`.
+    /// Gets the absolute path of `def_id` as a vector of `Symbol`.
     ///
     /// # Examples
     ///
     /// ```rust,ignore (no context or def id available)
     /// let def_path = cx.get_def_path(def_id);
-    /// if let &["core", "option", "Option"] = &def_path[..] {
+    /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
     ///     // The given `def_id` is that of an `Option` type
     /// }
     /// ```
-    pub fn get_def_path(&self, def_id: DefId) -> Vec<LocalInternedString> {
+    pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
         pub struct AbsolutePathPrinter<'a, 'tcx> {
             pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
         }
@@ -787,7 +787,7 @@ pub struct AbsolutePathPrinter<'a, 'tcx> {
         impl<'tcx> Printer<'tcx, 'tcx> for AbsolutePathPrinter<'_, 'tcx> {
             type Error = !;
 
-            type Path = Vec<LocalInternedString>;
+            type Path = Vec<Symbol>;
             type Region = ();
             type Type = ();
             type DynExistential = ();
@@ -820,14 +820,14 @@ fn print_const(
             }
 
             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
-                Ok(vec![self.tcx.original_crate_name(cnum).as_str()])
+                Ok(vec![self.tcx.original_crate_name(cnum)])
             }
 
             fn path_qualified(
                 self,
                 self_ty: Ty<'tcx>,
                 trait_ref: Option<ty::TraitRef<'tcx>>,
-                ) -> Result<Self::Path, Self::Error> {
+            ) -> Result<Self::Path, Self::Error> {
                 if trait_ref.is_none() {
                     if let ty::Adt(def, substs) = self_ty.sty {
                         return self.print_def_path(def.did, substs);
@@ -836,8 +836,8 @@ fn path_qualified(
 
                 // This shouldn't ever be needed, but just in case:
                 Ok(vec![match trait_ref {
-                    Some(trait_ref) => LocalInternedString::intern(&format!("{:?}", trait_ref)),
+                    Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
-                    None => LocalInternedString::intern(&format!("<{}>", self_ty)),
+                    None => Symbol::intern(&format!("<{}>", self_ty)),
                 }])
             }
 
@@ -847,16 +847,16 @@ fn path_append_impl(
                 _disambiguated_data: &DisambiguatedDefPathData,
                 self_ty: Ty<'tcx>,
                 trait_ref: Option<ty::TraitRef<'tcx>>,
-                ) -> Result<Self::Path, Self::Error> {
+            ) -> Result<Self::Path, Self::Error> {
                 let mut path = print_prefix(self)?;
 
                 // This shouldn't ever be needed, but just in case:
                 path.push(match trait_ref {
                     Some(trait_ref) => {
-                        LocalInternedString::intern(&format!("<impl {} for {}>", trait_ref,
+                        Symbol::intern(&format!("<impl {} for {}>", trait_ref,
                                                     self_ty))
                     },
-                    None => LocalInternedString::intern(&format!("<impl {}>", self_ty)),
+                    None => Symbol::intern(&format!("<impl {}>", self_ty)),
                 });
 
                 Ok(path)
@@ -866,7 +866,7 @@ fn path_append(
                 self,
                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
                 disambiguated_data: &DisambiguatedDefPathData,
-                ) -> Result<Self::Path, Self::Error> {
+            ) -> Result<Self::Path, Self::Error> {
                 let mut path = print_prefix(self)?;
 
                 // Skip `::{{constructor}}` on tuple/unit structs.
@@ -875,7 +875,7 @@ fn path_append(
                     _ => {}
                 }
 
-                path.push(disambiguated_data.data.as_interned_str().as_str());
+                path.push(disambiguated_data.data.as_interned_str().as_symbol());
                 Ok(path)
             }
 
@@ -883,7 +883,7 @@ fn path_generic_args(
                 self,
                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
                 _args: &[Kind<'tcx>],
-                ) -> Result<Self::Path, Self::Error> {
+            ) -> Result<Self::Path, Self::Error> {
                 print_prefix(self)
             }
         }

src/librustc/lint/internal.rs

@@ -8,6 +8,7 @@
 use errors::Applicability;
 use rustc_data_structures::fx::FxHashMap;
 use syntax::ast::Ident;
+use syntax::symbol::{sym, Symbol};
 
 declare_lint! {
     pub DEFAULT_HASH_TYPES,
@@ -16,14 +17,16 @@
 }
 
 pub struct DefaultHashTypes {
-    map: FxHashMap<String, String>,
+    map: FxHashMap<Symbol, Symbol>,
 }
 
 impl DefaultHashTypes {
+    // we are allowed to use `HashMap` and `HashSet` as identifiers for implementing the lint itself
+    #[allow(internal)]
     pub fn new() -> Self {
         let mut map = FxHashMap::default();
-        map.insert("HashMap".to_string(), "FxHashMap".to_string());
+        map.insert(sym::HashMap, sym::FxHashMap);
-        map.insert("HashSet".to_string(), "FxHashSet".to_string());
+        map.insert(sym::HashSet, sym::FxHashSet);
         Self { map }
     }
 }
@@ -32,11 +35,10 @@ pub fn new() -> Self {
 
 impl EarlyLintPass for DefaultHashTypes {
     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
-        let ident_string = ident.to_string();
+        if let Some(replace) = self.map.get(&ident.name) {
-        if let Some(replace) = self.map.get(&ident_string) {
             let msg = format!(
                 "Prefer {} over {}, it has better performance",
-                replace, ident_string
+                replace, ident
             );
             let mut db = cx.struct_span_lint(DEFAULT_HASH_TYPES, ident.span, &msg);
             db.span_suggestion(
@@ -169,10 +171,10 @@ fn check_ty(&mut self, cx: &LateContext<'_, '_>, ty: &'tcx Ty) {
 }
 
 fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment) -> bool {
-    if segment.ident.as_str() == "TyKind" {
+    if segment.ident.name == sym::TyKind {
         if let Some(res) = segment.res {
             if let Some(did) = res.opt_def_id() {
-                return cx.match_def_path(did, &["rustc", "ty", "sty", "TyKind"]);
+                return cx.match_def_path(did, TYKIND_PATH);
             }
         }
     }
@@ -180,14 +182,18 @@ fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment) -> bool {
     false
 }
 
+const TYKIND_PATH: &[Symbol] = &[sym::rustc, sym::ty, sym::sty, sym::TyKind];
+const TY_PATH: &[Symbol] = &[sym::rustc, sym::ty, sym::Ty];
+const TYCTXT_PATH: &[Symbol] = &[sym::rustc, sym::ty, sym::context, sym::TyCtxt];
+
 fn is_ty_or_ty_ctxt(cx: &LateContext<'_, '_>, ty: &Ty) -> Option<String> {
     match &ty.node {
         TyKind::Path(qpath) => {
             if let QPath::Resolved(_, path) = qpath {
                 let did = path.res.opt_def_id()?;
-                if cx.match_def_path(did, &["rustc", "ty", "Ty"]) {
+                if cx.match_def_path(did, TY_PATH) {
                     return Some(format!("Ty{}", gen_args(path.segments.last().unwrap())));
-                } else if cx.match_def_path(did, &["rustc", "ty", "context", "TyCtxt"]) {
+                } else if cx.match_def_path(did, TYCTXT_PATH) {
                     return Some(format!("TyCtxt{}", gen_args(path.segments.last().unwrap())));
                 }
             }

src/libsyntax_pos/symbol.rs

@@ -194,6 +194,7 @@
         const_raw_ptr_to_usize_cast,
         const_transmute,
         contents,
+        context,
         convert,
         copy_closures,
         core,
@@ -282,6 +283,8 @@
         fundamental,
         future,
         Future,
+        FxHashSet,
+        FxHashMap,
         gen_future,
         generators,
         generic_associated_types,
@@ -291,6 +294,8 @@
         globs,
         hash,
         Hash,
+        HashSet,
+        HashMap,
         hexagon_target_feature,
         hidden,
         homogeneous_aggregate,
@@ -505,6 +510,7 @@
         rust_2015_preview,
         rust_2018_preview,
         rust_begin_unwind,
+        rustc,
         rustc_allocator_nounwind,
         rustc_allow_const_fn_ptr,
         rustc_args_required_const,
@@ -590,6 +596,7 @@
         struct_inherit,
         structural_match,
         struct_variant,
+        sty,
         suggestion,
         target_feature,
         target_has_atomic,
@@ -618,7 +625,10 @@
         try_trait,
         tt,
         tuple_indexing,
+        Ty,
         ty,
+        TyCtxt,
+        TyKind,
         type_alias_enum_variants,
         type_ascription,
         type_length_limit,