Remove the Cow from Directory.

The previous commit wrapped `Parser` within a `Cow` for the hot macro
parsing path. As a result, there's no need for the `Cow` within
`Directory`, because it lies within `Parser`.

src/librustc_expand/mbe/macro_rules.rs

@@ -260,7 +260,7 @@ fn generic_extension<'cx>(
                 }
 
                 let directory = Directory {
-                    path: Cow::from(cx.current_expansion.module.directory.as_path()),
+                    path: cx.current_expansion.module.directory.clone(),
                     ownership: cx.current_expansion.directory_ownership,
                 };
                 let mut p = Parser::new(cx.parse_sess(), tts, Some(directory), true, false, None);
@@ -1218,7 +1218,7 @@ fn base_parser_from_cx<'cx>(
     tts: TokenStream,
 ) -> Parser<'cx> {
     let directory = Directory {
-        path: Cow::from(current_expansion.module.directory.as_path()),
+        path: current_expansion.module.directory.clone(),
         ownership: current_expansion.directory_ownership,
     };
     Parser::new(sess, tts, Some(directory), true, true, rustc_parse::MACRO_ARGUMENTS)

src/librustc_parse/lib.rs

@@ -12,8 +12,7 @@ use syntax::ast;
 use syntax::token::{self, Nonterminal};
 use syntax::tokenstream::{self, TokenStream, TokenTree};
 
-use std::borrow::Cow;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::str;
 
 use log::info;
@@ -29,8 +28,8 @@ pub mod validate_attr;
 pub mod config;
 
 #[derive(Clone)]
-pub struct Directory<'a> {
-    pub path: Cow<'a, Path>,
+pub struct Directory {
+    pub path: PathBuf,
     pub ownership: DirectoryOwnership,
 }
 
@@ -274,7 +273,7 @@ pub fn stream_to_parser<'a>(
 pub fn stream_to_parser_with_base_dir<'a>(
     sess: &'a ParseSess,
     stream: TokenStream,
-    base_dir: Directory<'a>,
+    base_dir: Directory,
 ) -> Parser<'a> {
     Parser::new(sess, stream, Some(base_dir), true, false, None)
 }

src/librustc_parse/parser/mod.rs

@@ -29,7 +29,6 @@ use syntax::token::{self, DelimToken, Token, TokenKind};
 use syntax::tokenstream::{self, DelimSpan, TokenStream, TokenTree, TreeAndJoint};
 use syntax::util::comments::{doc_comment_style, strip_doc_comment_decoration};
 
-use std::borrow::Cow;
 use std::path::PathBuf;
 use std::{cmp, mem, slice};
 
@@ -114,7 +113,7 @@ pub struct Parser<'a> {
     prev_token_kind: PrevTokenKind,
     restrictions: Restrictions,
     /// Used to determine the path to externally loaded source files.
-    pub(super) directory: Directory<'a>,
+    pub(super) directory: Directory,
     /// `true` to parse sub-modules in other files.
     // Public for rustfmt usage.
     pub recurse_into_file_modules: bool,
@@ -376,7 +375,7 @@ impl<'a> Parser<'a> {
     pub fn new(
         sess: &'a ParseSess,
         tokens: TokenStream,
-        directory: Option<Directory<'a>>,
+        directory: Option<Directory>,
         recurse_into_file_modules: bool,
         desugar_doc_comments: bool,
         subparser_name: Option<&'static str>,
@@ -390,7 +389,7 @@ impl<'a> Parser<'a> {
             restrictions: Restrictions::empty(),
             recurse_into_file_modules,
             directory: Directory {
-                path: Cow::from(PathBuf::new()),
+                path: PathBuf::new(),
                 ownership: DirectoryOwnership::Owned { relative: None },
             },
             root_module_name: None,
@@ -418,7 +417,7 @@ impl<'a> Parser<'a> {
                 &sess.source_map().lookup_char_pos(parser.token.span.lo()).file.unmapped_path
             {
                 if let Some(directory_path) = path.parent() {
-                    parser.directory.path = Cow::from(directory_path.to_path_buf());
+                    parser.directory.path = directory_path.to_path_buf();
                 }
             }
         }

src/librustc_parse/parser/module.rs

@@ -285,7 +285,7 @@ impl<'a> Parser<'a> {
 
     fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
         if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
-            self.directory.path.to_mut().push(&*path.as_str());
+            self.directory.path.push(&*path.as_str());
             self.directory.ownership = DirectoryOwnership::Owned { relative: None };
         } else {
             // We have to push on the current module name in the case of relative
@@ -297,10 +297,10 @@ impl<'a> Parser<'a> {
             if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
                 if let Some(ident) = relative.take() {
                     // remove the relative offset
-                    self.directory.path.to_mut().push(&*ident.as_str());
+                    self.directory.path.push(&*ident.as_str());
                 }
             }
-            self.directory.path.to_mut().push(&*id.as_str());
+            self.directory.path.push(&*id.as_str());
         }
     }
 }