Remove the equality operation between `Symbol` and strings.

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

12 files changed, 58 insertions, 53 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index aa176c89258..d12240655e6 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -81,12 +81,6 @@ impl PartialEq<Symbol> for Path {
     }
 }
 
-impl<'a> PartialEq<&'a str> for Path {
-    fn eq(&self, string: &&'a str) -> bool {
-        self.segments.len() == 1 && self.segments[0].ident.name == *string
-    }
-}
-
 impl fmt::Debug for Path {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "path({})", pprust::path_to_string(self))
diff --git a/src/libsyntax/attr/builtin.rs b/src/libsyntax/attr/builtin.rs
index a8310c48b96..43de3f74e4a 100644
--- a/src/libsyntax/attr/builtin.rs
+++ b/src/libsyntax/attr/builtin.rs
@@ -185,12 +185,12 @@ fn find_stability_generic<'a, I>(sess: &ParseSess,
 
     'outer: for attr in attrs_iter {
         if ![
-            "rustc_deprecated",
-            "rustc_const_unstable",
-            "unstable",
-            "stable",
-            "rustc_promotable",
-            "rustc_allow_const_fn_ptr",
+            sym::rustc_deprecated,
+            sym::rustc_const_unstable,
+            sym::unstable,
+            sym::stable,
+            sym::rustc_promotable,
+            sym::rustc_allow_const_fn_ptr,
         ].iter().any(|&s| attr.path == s) {
             continue // not a stability level
         }
@@ -199,10 +199,10 @@ fn find_stability_generic<'a, I>(sess: &ParseSess,
 
         let meta = attr.meta();
 
-        if attr.path == "rustc_promotable" {
+        if attr.path == sym::rustc_promotable {
             promotable = true;
         }
-        if attr.path == "rustc_allow_const_fn_ptr" {
+        if attr.path == sym::rustc_allow_const_fn_ptr {
             allow_const_fn_ptr = true;
         }
         // attributes with data
@@ -721,7 +721,7 @@ pub fn find_repr_attrs(sess: &ParseSess, attr: &Attribute) -> Vec<ReprAttr> {
 
     let mut acc = Vec::new();
     let diagnostic = &sess.span_diagnostic;
-    if attr.path == "repr" {
+    if attr.path == sym::repr {
         if let Some(items) = attr.meta_item_list() {
             mark_used(attr);
             for item in items {
@@ -770,14 +770,14 @@ pub fn find_repr_attrs(sess: &ParseSess, attr: &Attribute) -> Vec<ReprAttr> {
                     };
 
                     let mut literal_error = None;
-                    if name == "align" {
+                    if name == sym::align {
                         recognised = true;
                         match parse_alignment(&value.node) {
                             Ok(literal) => acc.push(ReprAlign(literal)),
                             Err(message) => literal_error = Some(message)
                         };
                     }
-                    else if name == "packed" {
+                    else if name == sym::packed {
                         recognised = true;
                         match parse_alignment(&value.node) {
                             Ok(literal) => acc.push(ReprPacked(literal)),
diff --git a/src/libsyntax/entry.rs b/src/libsyntax/entry.rs
index 267f863ce35..0b6cf30bd27 100644
--- a/src/libsyntax/entry.rs
+++ b/src/libsyntax/entry.rs
@@ -19,7 +19,7 @@ pub fn entry_point_type(item: &Item, depth: usize) -> 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 depth == 1 {
                     // This is a top-level function so can be 'main'
                     EntryPointType::MainNamed
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index cc19acb61ad..0a88d2f8824 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -10,7 +10,7 @@ use crate::mut_visit::{self, MutVisitor};
 use crate::parse::{self, parser, DirectoryOwnership};
 use crate::parse::token;
 use crate::ptr::P;
-use crate::symbol::{keywords, Ident, Symbol};
+use crate::symbol::{keywords, Ident, Symbol, sym};
 use crate::ThinVec;
 use crate::tokenstream::{self, TokenStream};
 
@@ -871,7 +871,7 @@ impl<'a> ExtCtxt<'a> {
         let mut last_macro = None;
         loop {
             if ctxt.outer().expn_info().map_or(None, |info| {
-                if info.format.name() == "include" {
+                if info.format.name() == sym::include {
                     // Stop going up the backtrace once include! is encountered
                     return None;
                 }
diff --git a/src/libsyntax/ext/derive.rs b/src/libsyntax/ext/derive.rs
index 6df369133d0..a24e09f127e 100644
--- a/src/libsyntax/ext/derive.rs
+++ b/src/libsyntax/ext/derive.rs
@@ -4,7 +4,7 @@ use crate::source_map::{hygiene, ExpnInfo, ExpnFormat};
 use crate::ext::base::ExtCtxt;
 use crate::ext::build::AstBuilder;
 use crate::parse::parser::PathStyle;
-use crate::symbol::Symbol;
+use crate::symbol::{Symbol, sym};
 
 use syntax_pos::Span;
 
@@ -13,7 +13,7 @@ use rustc_data_structures::fx::FxHashSet;
 pub fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>) -> Vec<ast::Path> {
     let mut result = Vec::new();
     attrs.retain(|attr| {
-        if attr.path != "derive" {
+        if attr.path != sym::derive {
             return true;
         }
         if !attr.is_meta_item_list() {
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 7ebfcfd176a..a286fd83e3c 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -376,7 +376,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     }
 
                     let mut item = self.fully_configure(item);
-                    item.visit_attrs(|attrs| attrs.retain(|a| a.path != "derive"));
+                    item.visit_attrs(|attrs| attrs.retain(|a| a.path != sym::derive));
                     let mut item_with_markers = item.clone();
                     add_derived_markers(&mut self.cx, item.span(), &traits, &mut item_with_markers);
                     let derives = derives.entry(invoc.expansion_data.mark).or_default();
@@ -1109,7 +1109,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                        -> Option<ast::Attribute> {
         let attr = attrs.iter()
                         .position(|a| {
-                            if a.path == "derive" {
+                            if a.path == sym::derive {
                                 *after_derive = true;
                             }
                             !attr::is_known(a) && !is_builtin_attr(a)
@@ -1117,7 +1117,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                         .map(|i| attrs.remove(i));
         if let Some(attr) = &attr {
             if !self.cx.ecfg.enable_custom_inner_attributes() &&
-               attr.style == ast::AttrStyle::Inner && attr.path != "test" {
+               attr.style == ast::AttrStyle::Inner && attr.path != sym::test {
                 emit_feature_err(&self.cx.parse_sess, sym::custom_inner_attributes,
                                  attr.span, GateIssue::Language,
                                  "non-builtin inner attributes are unstable");
@@ -1167,7 +1167,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
             self.check_attribute_inner(attr, features);
 
             // macros are expanded before any lint passes so this warning has to be hardcoded
-            if attr.path == "derive" {
+            if attr.path == sym::derive {
                 self.cx.struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
                     .note("this may become a hard error in a future release")
                     .emit();
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 55596210093..06651750de7 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -13,7 +13,7 @@ use crate::parse::{Directory, ParseSess};
 use crate::parse::parser::Parser;
 use crate::parse::token::{self, NtTT};
 use crate::parse::token::Token::*;
-use crate::symbol::{Symbol, sym};
+use crate::symbol::{Symbol, keywords, sym};
 use crate::tokenstream::{DelimSpan, TokenStream, TokenTree};
 
 use errors::FatalError;
@@ -467,7 +467,7 @@ fn check_lhs_no_empty_seq(sess: &ParseSess, tts: &[quoted::TokenTree]) -> bool {
             TokenTree::Sequence(span, ref seq) => {
                 if seq.separator.is_none() && seq.tts.iter().all(|seq_tt| {
                     match *seq_tt {
-                        TokenTree::MetaVarDecl(_, _, id) => id.name == "vis",
+                        TokenTree::MetaVarDecl(_, _, id) => id.name == sym::vis,
                         TokenTree::Sequence(_, ref sub_seq) =>
                             sub_seq.op == quoted::KleeneOp::ZeroOrMore
                             || sub_seq.op == quoted::KleeneOp::ZeroOrOne,
@@ -1046,7 +1046,8 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
                 match *tok {
                     TokenTree::Token(_, ref tok) => match *tok {
                         FatArrow | Comma | Eq | BinOp(token::Or) => IsInFollow::Yes,
-                        Ident(i, false) if i.name == "if" || i.name == "in" => IsInFollow::Yes,
+                        Ident(i, false) if i.name == keywords::If.name() ||
+                                           i.name == keywords::In.name() => IsInFollow::Yes,
                         _ => IsInFollow::No(tokens),
                     },
                     _ => IsInFollow::No(tokens),
@@ -1063,10 +1064,12 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
                         OpenDelim(token::DelimToken::Bracket) |
                         Comma | FatArrow | Colon | Eq | Gt | BinOp(token::Shr) | Semi |
                         BinOp(token::Or) => IsInFollow::Yes,
-                        Ident(i, false) if i.name == "as" || i.name == "where" => IsInFollow::Yes,
+                        Ident(i, false) if i.name == keywords::As.name() ||
+                                           i.name == keywords::Where.name() => IsInFollow::Yes,
                         _ => IsInFollow::No(tokens),
                     },
-                    TokenTree::MetaVarDecl(_, _, frag) if frag.name == "block" => IsInFollow::Yes,
+                    TokenTree::MetaVarDecl(_, _, frag) if frag.name == sym::block =>
+                        IsInFollow::Yes,
                     _ => IsInFollow::No(tokens),
                 }
             },
@@ -1089,16 +1092,18 @@ fn is_in_follow(tok: &quoted::TokenTree, frag: &str) -> IsInFollow {
                 match *tok {
                     TokenTree::Token(_, ref tok) => match *tok {
                         Comma => IsInFollow::Yes,
-                        Ident(i, is_raw) if is_raw || i.name != "priv" => IsInFollow::Yes,
+                        Ident(i, is_raw) if is_raw || i.name != keywords::Priv.name() =>
+                            IsInFollow::Yes,
                         ref tok => if tok.can_begin_type() {
                             IsInFollow::Yes
                         } else {
                             IsInFollow::No(tokens)
                         }
                     },
-                    TokenTree::MetaVarDecl(_, _, frag) if frag.name == "ident"
-                                                       || frag.name == "ty"
-                                                       || frag.name == "path" => IsInFollow::Yes,
+                    TokenTree::MetaVarDecl(_, _, frag) if frag.name == sym::ident
+                                                       || frag.name == sym::ty
+                                                       || frag.name == sym::path =>
+                        IsInFollow::Yes,
                     _ => IsInFollow::No(tokens),
                 }
             },
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 53ecb0762ab..e7740f1835b 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -22,13 +22,13 @@ use crate::source_map::Spanned;
 use crate::edition::{ALL_EDITIONS, Edition};
 use crate::visit::{self, FnKind, Visitor};
 use crate::parse::{token, ParseSess};
-use crate::symbol::Symbol;
+use crate::symbol::{Symbol, keywords, sym};
 use crate::tokenstream::TokenTree;
 
 use errors::{DiagnosticBuilder, Handler};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_target::spec::abi::Abi;
-use syntax_pos::{Span, DUMMY_SP, sym};
+use syntax_pos::{Span, DUMMY_SP};
 use log::debug;
 use lazy_static::lazy_static;
 
@@ -562,9 +562,9 @@ declare_features! (
 // Some features are known to be incomplete and using them is likely to have
 // unanticipated results, such as compiler crashes. We warn the user about these
 // to alert them.
-const INCOMPLETE_FEATURES: &[&str] = &[
-    "generic_associated_types",
-    "const_generics"
+const INCOMPLETE_FEATURES: &[Symbol] = &[
+    sym::generic_associated_types,
+    sym::const_generics
 ];
 
 declare_features! (
@@ -1947,7 +1947,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     fn visit_item(&mut self, i: &'a ast::Item) {
         match i.node {
             ast::ItemKind::Const(_,_) => {
-                if i.ident.name == "_" {
+                if i.ident.name == keywords::Underscore.name() {
                     gate_feature_post!(&self, underscore_const_names, i.span,
                                         "naming constants with `_` is unstable");
                 }
@@ -2304,7 +2304,7 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
         if edition <= crate_edition {
             // The `crate_edition` implies its respective umbrella feature-gate
             // (i.e., `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
-            edition_enabled_features.insert(Symbol::intern(edition.feature_name()), edition);
+            edition_enabled_features.insert(edition.feature_name(), edition);
         }
     }
 
@@ -2335,7 +2335,7 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
             }
 
             let name = mi.name_or_empty();
-            if INCOMPLETE_FEATURES.iter().any(|f| name == *f) {
+            if INCOMPLETE_FEATURES.iter().any(|f| name == f.as_str()) {
                 span_handler.struct_span_warn(
                     mi.span(),
                     &format!(
@@ -2345,7 +2345,7 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
                 ).emit();
             }
 
-            if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
+            if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name().as_str()) {
                 if *edition <= crate_edition {
                     continue;
                 }
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 64f3704e808..655baafcd2d 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -391,6 +391,8 @@ mod tests {
     #[test]
     fn string_to_tts_macro () {
         with_globals(|| {
+            use crate::symbol::sym;
+
             let tts: Vec<_> =
                 string_to_stream("macro_rules! zip (($a)=>($a))".to_string()).trees().collect();
             let tts: &[TokenTree] = &tts[..];
@@ -403,8 +405,8 @@ mod tests {
                     Some(&TokenTree::Token(_, token::Ident(name_zip, false))),
                     Some(&TokenTree::Delimited(_, macro_delim, ref macro_tts)),
                 )
-                if name_macro_rules.name == "macro_rules"
-                && name_zip.name == "zip" => {
+                if name_macro_rules.name == sym::macro_rules
+                && name_zip.name.as_str() == "zip" => {
                     let tts = &macro_tts.trees().collect::<Vec<_>>();
                     match (tts.len(), tts.get(0), tts.get(1), tts.get(2)) {
                         (
@@ -421,7 +423,7 @@ mod tests {
                                     Some(&TokenTree::Token(_, token::Dollar)),
                                     Some(&TokenTree::Token(_, token::Ident(ident, false))),
                                 )
-                                if first_delim == token::Paren && ident.name == "a" => {},
+                                if first_delim == token::Paren && ident.name.as_str() == "a" => {},
                                 _ => panic!("value 3: {:?} {:?}", first_delim, first_tts),
                             }
                             let tts = &second_tts.trees().collect::<Vec<_>>();
@@ -431,7 +433,7 @@ mod tests {
                                     Some(&TokenTree::Token(_, token::Dollar)),
                                     Some(&TokenTree::Token(_, token::Ident(ident, false))),
                                 )
-                                if second_delim == token::Paren && ident.name == "a" => {},
+                                if second_delim == token::Paren && ident.name.as_str() == "a" => {},
                                 _ => panic!("value 4: {:?} {:?}", second_delim, second_tts),
                             }
                         },
@@ -584,13 +586,13 @@ mod tests {
             let item = parse_item_from_source_str(name_1, source, &sess)
                 .unwrap().unwrap();
             let doc = first_attr_value_str_by_name(&item.attrs, sym::doc).unwrap();
-            assert_eq!(doc, "/// doc comment");
+            assert_eq!(doc.as_str(), "/// doc comment");
 
             let name_2 = FileName::Custom("crlf_source_2".to_string());
             let source = "/// doc comment\r\n/// line 2\r\nfn foo() {}".to_string();
             let item = parse_item_from_source_str(name_2, source, &sess)
                 .unwrap().unwrap();
-            let docs = item.attrs.iter().filter(|a| a.path == "doc")
+            let docs = item.attrs.iter().filter(|a| a.path == sym::doc)
                         .map(|a| a.value_str().unwrap().to_string()).collect::<Vec<_>>();
             let b: &[_] = &["/// doc comment".to_string(), "/// line 2".to_string()];
             assert_eq!(&docs[..], b);
@@ -599,7 +601,7 @@ mod tests {
             let source = "/** doc comment\r\n *  with CRLF */\r\nfn foo() {}".to_string();
             let item = parse_item_from_source_str(name_3, source, &sess).unwrap().unwrap();
             let doc = first_attr_value_str_by_name(&item.attrs, sym::doc).unwrap();
-            assert_eq!(doc, "/** doc comment\n *  with CRLF */");
+            assert_eq!(doc.as_str(), "/** doc comment\n *  with CRLF */");
         });
     }
 
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index d3dd6bb1e01..c0f3c358e98 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -5099,7 +5099,7 @@ impl<'a> Parser<'a> {
 
                 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
             }
-            token::Ident(ident, _) if ident.name == "macro_rules" &&
+            token::Ident(ident, _) if ident.name == sym::macro_rules &&
                                    self.look_ahead(1, |t| *t == token::Not) => {
                 let prev_span = self.prev_span;
                 self.complain_if_pub_macro(&vis.node, prev_span);
diff --git a/src/libsyntax/std_inject.rs b/src/libsyntax/std_inject.rs
index 42ca8b7c23c..f08fdcc6fb5 100644
--- a/src/libsyntax/std_inject.rs
+++ b/src/libsyntax/std_inject.rs
@@ -35,6 +35,9 @@ pub fn injected_crate_name() -> Option<&'static str> {
 }
 
 thread_local! {
+    // A `Symbol` might make more sense here, but it doesn't work, probably for
+    // reasons relating to the use of thread-local storage for the Symbol
+    // interner.
     static INJECTED_CRATE_NAME: Cell<Option<&'static str>> = Cell::new(None);
 }
 
diff --git a/src/libsyntax/test.rs b/src/libsyntax/test.rs
index 8e5e594ce9a..21bc236d00e 100644
--- a/src/libsyntax/test.rs
+++ b/src/libsyntax/test.rs
@@ -272,7 +272,8 @@ fn generate_test_harness(sess: &ParseSess,
         test_cases: Vec::new(),
         reexport_test_harness_main,
         // N.B., doesn't consider the value of `--crate-name` passed on the command line.
-        is_libtest: attr::find_crate_name(&krate.attrs).map(|s| s == "test").unwrap_or(false),
+        is_libtest: attr::find_crate_name(&krate.attrs)
+            .map(|s| s == sym::test).unwrap_or(false),
         toplevel_reexport: None,
         ctxt: SyntaxContext::empty().apply_mark(mark),
         features,