Auto merge of #60630 - nnethercote:use-Symbol-more, r=petrochenkov

Use `Symbol` more

A `Symbol` can be equated with a string (e.g. `&str`). This involves a
TLS lookup to get the chars (and a Mutex lock in a parallel compiler)
and then a char-by-char comparison. This functionality is convenient but
avoids one of the main benefits of `Symbol`s, which is fast equality
comparisons.

This PR removes the `Symbol`/string equality operations, forcing a lot
of existing string occurrences to become `Symbol`s. Fortunately, these
are almost all static strings (many are attribute names) and we can add
static `Symbol`s as necessary, and very little extra interning occurs.
The benefits are (a) a slight speedup (possibly greater in a parallel
compiler), and (b) the code is a lot more principled about `Symbol` use.
The main downside is verbosity, particularly with more `use
syntax::symbol::symbols` items.

r? @Zoxc

7 files changed, 17 insertions, 15 deletions

diff --git a/src/test/run-pass-fulldeps/auxiliary/custom-derive-plugin-attr.rs b/src/test/run-pass-fulldeps/auxiliary/custom-derive-plugin-attr.rs
index 699972c9a85..c6b33fbc75e 100644
--- a/src/test/run-pass-fulldeps/auxiliary/custom-derive-plugin-attr.rs
+++ b/src/test/run-pass-fulldeps/auxiliary/custom-derive-plugin-attr.rs
@@ -14,7 +14,7 @@ use syntax::ast;
 use syntax::attr;
 use syntax::ext::base::{MultiDecorator, ExtCtxt, Annotatable};
 use syntax::ext::build::AstBuilder;
-use syntax::symbol::Symbol;
+use syntax::symbol::{Symbol, sym};
 use syntax::ptr::P;
 use syntax_ext::deriving::generic::{TraitDef, MethodDef, combine_substructure};
 use syntax_ext::deriving::generic::{Substructure, Struct, EnumMatching};
@@ -71,7 +71,7 @@ fn totalsum_substructure(cx: &mut ExtCtxt, trait_span: Span,
     };
 
     fields.iter().fold(cx.expr_isize(trait_span, 0), |acc, ref item| {
-        if attr::contains_name(&item.attrs, "ignore") {
+        if attr::contains_name(&item.attrs, sym::ignore) {
             acc
         } else {
             cx.expr_binary(item.span, ast::BinOpKind::Add, acc,
diff --git a/src/test/run-pass-fulldeps/auxiliary/issue-40001-plugin.rs b/src/test/run-pass-fulldeps/auxiliary/issue-40001-plugin.rs
index 76d0906f97c..40e0115c623 100644
--- a/src/test/run-pass-fulldeps/auxiliary/issue-40001-plugin.rs
+++ b/src/test/run-pass-fulldeps/auxiliary/issue-40001-plugin.rs
@@ -23,7 +23,7 @@ use syntax::{ast, source_map};
 #[plugin_registrar]
 pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_late_lint_pass(box MissingWhitelistedAttrPass);
-    reg.register_attribute("whitelisted_attr".to_string(), Whitelisted);
+    reg.register_attribute(Symbol::intern("whitelisted_attr"), Whitelisted);
 }
 
 declare_lint! {
@@ -48,7 +48,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingWhitelistedAttrPass {
             _ => cx.tcx.hir().expect_item_by_hir_id(cx.tcx.hir().get_parent_item(id)),
         };
 
-        if !attr::contains_name(&item.attrs, "whitelisted_attr") {
+        if !attr::contains_name(&item.attrs, Symbol::intern("whitelisted_attr")) {
             cx.span_lint(MISSING_WHITELISTED_ATTR, span,
                          "Missing 'whitelisted_attr' attribute");
         }
diff --git a/src/test/run-pass-fulldeps/auxiliary/lint-for-crate.rs b/src/test/run-pass-fulldeps/auxiliary/lint-for-crate.rs
index f34e10218d4..8c7bd7222e7 100644
--- a/src/test/run-pass-fulldeps/auxiliary/lint-for-crate.rs
+++ b/src/test/run-pass-fulldeps/auxiliary/lint-for-crate.rs
@@ -11,6 +11,7 @@ use rustc::lint::{LateContext, LintContext, LintPass, LateLintPass, LateLintPass
 use rustc_plugin::Registry;
 use rustc::hir;
 use syntax::attr;
+use syntax::symbol::Symbol;
 
 macro_rules! fake_lint_pass {
     ($struct:ident, $lints:expr, $($attr:expr),*) => {
@@ -49,19 +50,19 @@ declare_lint!(CRATE_NOT_GREEN, Warn, "crate not marked with #![crate_green]");
 fake_lint_pass! {
     PassOkay,
     lint_array!(CRATE_NOT_OKAY), // Single lint
-    "rustc_crate_okay"
+    Symbol::intern("rustc_crate_okay")
 }
 
 fake_lint_pass! {
     PassRedBlue,
     lint_array!(CRATE_NOT_RED, CRATE_NOT_BLUE), // Multiple lints
-    "rustc_crate_red", "rustc_crate_blue"
+    Symbol::intern("rustc_crate_red"), Symbol::intern("rustc_crate_blue")
 }
 
 fake_lint_pass! {
     PassGreyGreen,
     lint_array!(CRATE_NOT_GREY, CRATE_NOT_GREEN, ), // Trailing comma
-    "rustc_crate_grey", "rustc_crate_green"
+    Symbol::intern("rustc_crate_grey"), Symbol::intern("rustc_crate_green")
 }
 
 #[plugin_registrar]
diff --git a/src/test/ui-fulldeps/auxiliary/attr-plugin-test.rs b/src/test/ui-fulldeps/auxiliary/attr-plugin-test.rs
index c83e7bdb998..039124f31ff 100644
--- a/src/test/ui-fulldeps/auxiliary/attr-plugin-test.rs
+++ b/src/test/ui-fulldeps/auxiliary/attr-plugin-test.rs
@@ -8,14 +8,14 @@ extern crate syntax;
 extern crate rustc;
 extern crate rustc_plugin;
 
+use syntax::symbol::Symbol;
 use syntax::feature_gate::AttributeType;
 use rustc_plugin::Registry;
 
 
-
 #[plugin_registrar]
 pub fn plugin_registrar(reg: &mut Registry) {
-    reg.register_attribute("foo".to_owned(), AttributeType::Normal);
-    reg.register_attribute("bar".to_owned(), AttributeType::CrateLevel);
-    reg.register_attribute("baz".to_owned(), AttributeType::Whitelisted);
+    reg.register_attribute(Symbol::intern("foo"), AttributeType::Normal);
+    reg.register_attribute(Symbol::intern("bar"), AttributeType::CrateLevel);
+    reg.register_attribute(Symbol::intern("baz"), AttributeType::Whitelisted);
 }
diff --git a/src/test/ui-fulldeps/auxiliary/lint-for-crate.rs b/src/test/ui-fulldeps/auxiliary/lint-for-crate.rs
index e8f1d2eedf5..7656b15721a 100644
--- a/src/test/ui-fulldeps/auxiliary/lint-for-crate.rs
+++ b/src/test/ui-fulldeps/auxiliary/lint-for-crate.rs
@@ -11,6 +11,7 @@ use rustc::lint::{LateContext, LintContext, LintPass, LateLintPass, LateLintPass
 use rustc_plugin::Registry;
 use rustc::hir;
 use syntax::attr;
+use syntax::symbol::Symbol;
 
 declare_lint! {
     CRATE_NOT_OKAY,
@@ -22,7 +23,7 @@ declare_lint_pass!(Pass => [CRATE_NOT_OKAY]);
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
     fn check_crate(&mut self, cx: &LateContext, krate: &hir::Crate) {
-        if !attr::contains_name(&krate.attrs, "crate_okay") {
+        if !attr::contains_name(&krate.attrs, Symbol::intern("crate_okay")) {
             cx.span_lint(CRATE_NOT_OKAY, krate.span,
                          "crate is not marked with #![crate_okay]");
         }
diff --git a/src/test/ui-fulldeps/auxiliary/lint-plugin-test.rs b/src/test/ui-fulldeps/auxiliary/lint-plugin-test.rs
index 1d204e7bfcf..0deb1bf0915 100644
--- a/src/test/ui-fulldeps/auxiliary/lint-plugin-test.rs
+++ b/src/test/ui-fulldeps/auxiliary/lint-plugin-test.rs
@@ -20,7 +20,7 @@ declare_lint_pass!(Pass => [TEST_LINT]);
 
 impl EarlyLintPass for Pass {
     fn check_item(&mut self, cx: &EarlyContext, it: &ast::Item) {
-        if it.ident.name == "lintme" {
+        if it.ident.name.as_str() == "lintme" {
             cx.span_lint(TEST_LINT, it.span, "item is named 'lintme'");
         }
     }
diff --git a/src/test/ui-fulldeps/auxiliary/lint-tool-test.rs b/src/test/ui-fulldeps/auxiliary/lint-tool-test.rs
index 182d2899da1..64664377cd9 100644
--- a/src/test/ui-fulldeps/auxiliary/lint-tool-test.rs
+++ b/src/test/ui-fulldeps/auxiliary/lint-tool-test.rs
@@ -23,10 +23,10 @@ declare_lint_pass!(Pass => [TEST_LINT, TEST_GROUP]);
 
 impl EarlyLintPass for Pass {
     fn check_item(&mut self, cx: &EarlyContext, it: &ast::Item) {
-        if it.ident.name == "lintme" {
+        if it.ident.name.as_str() == "lintme" {
             cx.span_lint(TEST_LINT, it.span, "item is named 'lintme'");
         }
-        if it.ident.name == "lintmetoo" {
+        if it.ident.name.as_str() == "lintmetoo" {
             cx.span_lint(TEST_GROUP, it.span, "item is named 'lintmetoo'");
         }
     }