Remove the equality operation between Symbol and strings.

And also the equality between `Path` and strings, because `Path` is made
up of `Symbol`s.

src/librustc/hir/lowering.rs

@@ -73,7 +73,7 @@ use syntax_pos::Span;
 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
 
 pub struct LoweringContext<'a> {
-    crate_root: Option<&'static str>,
+    crate_root: Option<Symbol>,
 
     /// Used to assign ids to HIR nodes that do not directly correspond to an AST node.
     sess: &'a Session,
@@ -164,8 +164,8 @@ pub trait Resolver {
     fn resolve_str_path(
         &mut self,
         span: Span,
-        crate_root: Option<&str>,
-        components: &[&str],
+        crate_root: Option<Symbol>,
+        components: &[Symbol],
         is_value: bool,
     ) -> hir::Path;
 }
@@ -228,7 +228,7 @@ pub fn lower_crate(
     dep_graph.assert_ignored();
 
     LoweringContext {
-        crate_root: std_inject::injected_crate_name(),
+        crate_root: std_inject::injected_crate_name().map(Symbol::intern),
         sess,
         cstore,
         resolver,
@@ -1149,7 +1149,7 @@ impl<'a> LoweringContext<'a> {
             ].into()),
         );
         let gen_future = self.expr_std_path(
-            unstable_span, &["future", "from_generator"], None, ThinVec::new());
+            unstable_span, &[sym::future, sym::from_generator], None, ThinVec::new());
         hir::ExprKind::Call(P(gen_future), hir_vec![generator])
     }
 
@@ -2548,7 +2548,7 @@ impl<'a> LoweringContext<'a> {
 
         // ::std::future::Future<future_params>
         let future_path =
-            self.std_path(span, &["future", "Future"], Some(future_params), false);
+            self.std_path(span, &[sym::future, sym::Future], Some(future_params), false);
 
         hir::GenericBound::Trait(
             hir::PolyTraitRef {
@@ -4194,7 +4194,7 @@ impl<'a> LoweringContext<'a> {
                         |x: P<hir::Expr>| x.into_inner(),
                     );
                     block.expr = Some(this.wrap_in_try_constructor(
-                        "from_ok", tail, unstable_span));
+                        sym::from_ok, tail, unstable_span));
                     hir::ExprKind::Block(P(block), None)
                 })
             }
@@ -4336,7 +4336,7 @@ impl<'a> LoweringContext<'a> {
                 self.expr_call_std_assoc_fn(
                     id,
                     e.span,
-                    &["ops", "RangeInclusive"],
+                    &[sym::ops, sym::RangeInclusive],
                     "new",
                     hir_vec![e1, e2],
                 )
@@ -4345,11 +4345,11 @@ impl<'a> LoweringContext<'a> {
                 use syntax::ast::RangeLimits::*;
 
                 let path = match (e1, e2, lims) {
-                    (&None, &None, HalfOpen) => "RangeFull",
-                    (&Some(..), &None, HalfOpen) => "RangeFrom",
-                    (&None, &Some(..), HalfOpen) => "RangeTo",
-                    (&Some(..), &Some(..), HalfOpen) => "Range",
-                    (&None, &Some(..), Closed) => "RangeToInclusive",
+                    (&None, &None, HalfOpen) => sym::RangeFull,
+                    (&Some(..), &None, HalfOpen) => sym::RangeFrom,
+                    (&None, &Some(..), HalfOpen) => sym::RangeTo,
+                    (&Some(..), &Some(..), HalfOpen) => sym::Range,
+                    (&None, &Some(..), Closed) => sym::RangeToInclusive,
                     (&Some(..), &Some(..), Closed) => unreachable!(),
                     (_, &None, Closed) => self.diagnostic()
                         .span_fatal(e.span, "inclusive range with no end")
@@ -4367,7 +4367,7 @@ impl<'a> LoweringContext<'a> {
                     .collect::<P<[hir::Field]>>();
 
                 let is_unit = fields.is_empty();
-                let struct_path = ["ops", path];
+                let struct_path = [sym::ops, path];
                 let struct_path = self.std_path(e.span, &struct_path, None, is_unit);
                 let struct_path = hir::QPath::Resolved(None, P(struct_path));
 
@@ -4656,7 +4656,7 @@ impl<'a> LoweringContext<'a> {
                 let match_expr = {
                     let iter = P(self.expr_ident(head_sp, iter, iter_pat_nid));
                     let ref_mut_iter = self.expr_mut_addr_of(head_sp, iter);
-                    let next_path = &["iter", "Iterator", "next"];
+                    let next_path = &[sym::iter, sym::Iterator, sym::next];
                     let next_expr = P(self.expr_call_std_path(
                         head_sp,
                         next_path,
@@ -4723,7 +4723,8 @@ impl<'a> LoweringContext<'a> {
 
                 // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
                 let into_iter_expr = {
-                    let into_iter_path = &["iter", "IntoIterator", "into_iter"];
+                    let into_iter_path =
+                        &[sym::iter, sym::IntoIterator, sym::into_iter];
                     P(self.expr_call_std_path(
                         head_sp,
                         into_iter_path,
@@ -4780,7 +4781,7 @@ impl<'a> LoweringContext<'a> {
                     // expand <expr>
                     let sub_expr = self.lower_expr(sub_expr);
 
-                    let path = &["ops", "Try", "into_result"];
+                    let path = &[sym::ops, sym::Try, sym::into_result];
                     P(self.expr_call_std_path(
                         unstable_span,
                         path,
@@ -4822,12 +4823,12 @@ impl<'a> LoweringContext<'a> {
                     let err_ident = self.str_to_ident("err");
                     let (err_local, err_local_nid) = self.pat_ident(try_span, err_ident);
                     let from_expr = {
-                        let from_path = &["convert", "From", "from"];
+                        let from_path = &[sym::convert, sym::From, sym::from];
                         let err_expr = self.expr_ident(try_span, err_ident, err_local_nid);
                         self.expr_call_std_path(try_span, from_path, hir_vec![err_expr])
                     };
                     let from_err_expr =
-                        self.wrap_in_try_constructor("from_error", from_expr, unstable_span);
+                        self.wrap_in_try_constructor(sym::from_error, from_expr, unstable_span);
                     let thin_attrs = ThinVec::from(attrs);
                     let catch_scope = self.catch_scopes.last().map(|x| *x);
                     let ret_expr = if let Some(catch_node) = catch_scope {
@@ -5057,7 +5058,7 @@ impl<'a> LoweringContext<'a> {
     fn expr_call_std_path(
         &mut self,
         span: Span,
-        path_components: &[&str],
+        path_components: &[Symbol],
         args: hir::HirVec<hir::Expr>,
     ) -> hir::Expr {
         let path = P(self.expr_std_path(span, path_components, None, ThinVec::new()));
@@ -5077,7 +5078,7 @@ impl<'a> LoweringContext<'a> {
         &mut self,
         ty_path_id: hir::HirId,
         span: Span,
-        ty_path_components: &[&str],
+        ty_path_components: &[Symbol],
         assoc_fn_name: &str,
         args: hir::HirVec<hir::Expr>,
     ) -> hir::ExprKind {
@@ -5119,7 +5120,7 @@ impl<'a> LoweringContext<'a> {
     fn expr_std_path(
         &mut self,
         span: Span,
-        components: &[&str],
+        components: &[Symbol],
         params: Option<P<hir::GenericArgs>>,
         attrs: ThinVec<Attribute>,
     ) -> hir::Expr {
@@ -5250,25 +5251,25 @@ impl<'a> LoweringContext<'a> {
     }
 
     fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
-        self.pat_std_enum(span, &["result", "Result", "Ok"], hir_vec![pat])
+        self.pat_std_enum(span, &[sym::result, sym::Result, sym::Ok], hir_vec![pat])
     }
 
     fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
-        self.pat_std_enum(span, &["result", "Result", "Err"], hir_vec![pat])
+        self.pat_std_enum(span, &[sym::result, sym::Result, sym::Err], hir_vec![pat])
     }
 
     fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
-        self.pat_std_enum(span, &["option", "Option", "Some"], hir_vec![pat])
+        self.pat_std_enum(span, &[sym::option, sym::Option, sym::Some], hir_vec![pat])
     }
 
     fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
-        self.pat_std_enum(span, &["option", "Option", "None"], hir_vec![])
+        self.pat_std_enum(span, &[sym::option, sym::Option, sym::None], hir_vec![])
     }
 
     fn pat_std_enum(
         &mut self,
         span: Span,
-        components: &[&str],
+        components: &[Symbol],
         subpats: hir::HirVec<P<hir::Pat>>,
     ) -> P<hir::Pat> {
         let path = self.std_path(span, components, None, true);
@@ -5321,7 +5322,7 @@ impl<'a> LoweringContext<'a> {
     fn std_path(
         &mut self,
         span: Span,
-        components: &[&str],
+        components: &[Symbol],
         params: Option<P<hir::GenericArgs>>,
         is_value: bool,
     ) -> hir::Path {
@@ -5520,11 +5521,11 @@ impl<'a> LoweringContext<'a> {
 
     fn wrap_in_try_constructor(
         &mut self,
-        method: &'static str,
+        method: Symbol,
         e: hir::Expr,
         unstable_span: Span,
     ) -> P<hir::Expr> {
-        let path = &["ops", "Try", method];
+        let path = &[sym::ops, sym::Try, method];
         let from_err = P(self.expr_std_path(unstable_span, path, None,
                                             ThinVec::new()));
         P(self.expr_call(e.span, from_err, hir_vec![e]))
@@ -5594,15 +5595,15 @@ impl<'a> LoweringContext<'a> {
             let new_unchecked_expr_kind = self.expr_call_std_assoc_fn(
                 pin_ty_id,
                 span,
-                &["pin", "Pin"],
+                &[sym::pin, sym::Pin],
                 "new_unchecked",
                 hir_vec![ref_mut_pinned],
             );
             let new_unchecked = P(self.expr(span, new_unchecked_expr_kind, ThinVec::new()));
             let unsafe_expr = self.expr_unsafe(new_unchecked);
             P(self.expr_call_std_path(
                 gen_future_span,
-                &["future", "poll_with_tls_context"],
+                &[sym::future, sym::poll_with_tls_context],
                 hir_vec![unsafe_expr],
             ))
         };
@@ -5616,7 +5617,7 @@ impl<'a> LoweringContext<'a> {
             let x_expr = P(self.expr_ident(span, x_ident, x_pat_hid));
             let ready_pat = self.pat_std_enum(
                 span,
-                &["task", "Poll", "Ready"],
+                &[sym::task, sym::Poll, sym::Ready],
                 hir_vec![x_pat],
             );
             let break_x = self.with_loop_scope(loop_node_id, |this| {
@@ -5633,7 +5634,7 @@ impl<'a> LoweringContext<'a> {
         let pending_arm = {
             let pending_pat = self.pat_std_enum(
                 span,
-                &["task", "Poll", "Pending"],
+                &[sym::task, sym::Poll, sym::Pending],
                 hir_vec![],
             );
             let empty_block = P(self.expr_block_empty(span));

src/librustc/hir/map/mod.rs

@@ -1146,7 +1146,7 @@ impl<'a> NodesMatchingSuffix<'a> {
                 None => return false,
                 Some((node_id, name)) => (node_id, name),
             };
-            if mod_name != &**part {
+            if mod_name.as_str() != *part {
                 return false;
             }
             cursor = self.map.get_parent_item(mod_id);
@@ -1183,7 +1183,7 @@ impl<'a> NodesMatchingSuffix<'a> {
     // We are looking at some node `n` with a given name and parent
     // id; do their names match what I am seeking?
     fn matches_names(&self, parent_of_n: HirId, name: Name) -> bool {
-        name == &**self.item_name && self.suffix_matches(parent_of_n)
+        name.as_str() == *self.item_name && self.suffix_matches(parent_of_n)
     }
 
     fn matches_suffix(&self, hir: HirId) -> bool {

src/librustc/lint/levels.rs

@@ -221,7 +221,7 @@ impl<'a> LintLevelsBuilder<'a> {
                 match item.node {
                     ast::MetaItemKind::Word => {}  // actual lint names handled later
                     ast::MetaItemKind::NameValue(ref name_value) => {
-                        if item.path == "reason" {
+                        if item.path == sym::reason {
                             // found reason, reslice meta list to exclude it
                             metas = &metas[0..metas.len()-1];
                             // FIXME (#55112): issue unused-attributes lint if we thereby
@@ -261,7 +261,7 @@ impl<'a> LintLevelsBuilder<'a> {
                         let mut err = bad_attr(li.span());
                         if let Some(item) = li.meta_item() {
                             if let ast::MetaItemKind::NameValue(_) = item.node {
-                                if item.path == "reason" {
+                                if item.path == sym::reason {
                                     err.help("reason in lint attribute must come last");
                                 }
                             }

src/librustc/middle/entry.rs

@@ -86,7 +86,7 @@ fn entry_point_type(item: &Item, at_root: bool) -> EntryPointType {
                 EntryPointType::Start
             } else if attr::contains_name(&item.attrs, sym::main) {
                 EntryPointType::MainAttr
-            } else if item.ident.name == "main" {
+            } else if item.ident.name == sym::main {
                 if at_root {
                     // This is a top-level function so can be 'main'.
                     EntryPointType::MainNamed

src/librustc/middle/lib_features.rs

@@ -76,7 +76,7 @@ impl<'a, 'tcx> LibFeatureCollector<'a, 'tcx> {
                     // This additional check for stability is to make sure we
                     // don't emit additional, irrelevant errors for malformed
                     // attributes.
-                    if *stab_attr != "stable" || since.is_some() {
+                    if *stab_attr != sym::stable || since.is_some() {
                         return Some((feature, since, attr.span));
                     }
                 }

src/librustc/middle/stability.rs

@@ -686,7 +686,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 // the `-Z force-unstable-if-unmarked` flag present (we're
                 // compiling a compiler crate), then let this missing feature
                 // annotation slide.
-                if feature == "rustc_private" && issue == 27812 {
+                if feature == sym::rustc_private && issue == 27812 {
                     if self.sess.opts.debugging_opts.force_unstable_if_unmarked {
                         return EvalResult::Allow;
                     }

src/librustc/middle/weak_lang_items.rs

@@ -6,7 +6,7 @@ use crate::middle::lang_items;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_target::spec::PanicStrategy;
 use syntax::ast;
-use syntax::symbol::Symbol;
+use syntax::symbol::{Symbol, sym};
 use syntax_pos::Span;
 use crate::hir::def_id::DefId;
 use crate::hir::intravisit::{Visitor, NestedVisitorMap};
@@ -46,8 +46,8 @@ pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
 pub fn link_name(attrs: &[ast::Attribute]) -> Option<Symbol> {
     lang_items::extract(attrs).and_then(|(name, _)| {
-        $(if name == stringify!($name) {
-            Some(Symbol::intern(stringify!($sym)))
+        $(if name == sym::$name {
+            Some(sym::$sym)
         } else)* {
             None
         }

src/librustc/session/config.rs

@@ -2753,6 +2753,7 @@ mod tests {
     // another --cfg test
     #[test]
     fn test_switch_implies_cfg_test_unless_cfg_test() {
+        use syntax::symbol::sym;
         syntax::with_globals(|| {
             let matches = &match optgroups().parse(&["--test".to_string(),
                                                      "--cfg=test".to_string()]) {
@@ -2763,7 +2764,7 @@ mod tests {
             let (sessopts, cfg) = build_session_options_and_crate_config(matches);
             let sess = build_session(sessopts, None, registry);
             let cfg = build_configuration(&sess, to_crate_config(cfg));
-            let mut test_items = cfg.iter().filter(|&&(name, _)| name == "test");
+            let mut test_items = cfg.iter().filter(|&&(name, _)| name == sym::test);
             assert!(test_items.next().is_some());
             assert!(test_items.next().is_none());
         });

src/librustc/traits/project.rs

@@ -19,6 +19,7 @@ use crate::mir::interpret::{GlobalId, ConstValue};
 use rustc_data_structures::snapshot_map::{Snapshot, SnapshotMap};
 use rustc_macros::HashStable;
 use syntax::ast::Ident;
+use syntax::symbol::sym;
 use crate::ty::subst::{Subst, InternalSubsts};
 use crate::ty::{self, ToPredicate, ToPolyTraitRef, Ty, TyCtxt};
 use crate::ty::fold::{TypeFoldable, TypeFolder};
@@ -1318,9 +1319,9 @@ fn confirm_generator_candidate<'cx, 'gcx, 'tcx>(
                                             gen_sig)
         .map_bound(|(trait_ref, yield_ty, return_ty)| {
             let name = tcx.associated_item(obligation.predicate.item_def_id).ident.name;
-            let ty = if name == "Return" {
+            let ty = if name == sym::Return {
                 return_ty
-            } else if name == "Yield" {
+            } else if name == sym::Yield {
                 yield_ty
             } else {
                 bug!()

src/librustc_codegen_ssa/back/write.rs

@@ -386,7 +386,7 @@ pub fn start_async_codegen<B: ExtraBackendMethods>(
     let subsystem = attr::first_attr_value_str_by_name(&tcx.hir().krate().attrs,
                                                        sym::windows_subsystem);
     let windows_subsystem = subsystem.map(|subsystem| {
-        if subsystem != "windows" && subsystem != "console" {
+        if subsystem != sym::windows && subsystem != sym::console {
             tcx.sess.fatal(&format!("invalid windows subsystem `{}`, only \
                                      `windows` and `console` are allowed",
                                     subsystem));

src/librustc_codegen_utils/link.rs

@@ -56,7 +56,7 @@ pub fn find_crate_name(sess: Option<&Session>,
     if let Some(sess) = sess {
         if let Some(ref s) = sess.opts.crate_name {
             if let Some((attr, name)) = attr_crate_name {
-                if name != &**s {
+                if name.as_str() != *s {
                     let msg = format!("--crate-name and #[crate_name] are \
                                        required to match, but `{}` != `{}`",
                                       s, name);