Auto merge of #37824 - jseyfried:symbols, r=eddyb

Clean up `ast::Attribute`, `ast::CrateConfig`, and string interning

This PR
 - removes `ast::Attribute_` (changing `Attribute` from `Spanned<Attribute_>` to a struct),
 - moves a `MetaItem`'s name from the `MetaItemKind` variants to a field of `MetaItem`,
 - avoids needlessly wrapping `ast::MetaItem` with `P`,
 - moves string interning into `syntax::symbol` (`ast::Name` is a reexport of `symbol::Symbol` for now),
 - replaces `InternedString` with `Symbol` in the AST, HIR, and various other places, and
 - refactors `ast::CrateConfig` from a `Vec` to a `HashSet`.

r? @eddyb

4 files changed, 11 insertions, 123 deletions

diff --git a/src/libsyntax/util/interner.rs b/src/libsyntax/util/interner.rs
deleted file mode 100644
index f56c6cedcd1..00000000000
--- a/src/libsyntax/util/interner.rs
+++ /dev/null
@@ -1,111 +0,0 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! An "interner" is a data structure that associates values with usize tags and
-//! allows bidirectional lookup; i.e. given a value, one can easily find the
-//! type, and vice versa.
-
-use ast::Name;
-
-use std::collections::HashMap;
-use std::rc::Rc;
-
-#[derive(Default)]
-pub struct Interner {
-    names: HashMap<Rc<str>, Name>,
-    strings: Vec<Rc<str>>,
-}
-
-/// When traits can extend traits, we should extend index<Name,T> to get []
-impl Interner {
-    pub fn new() -> Self {
-        Interner::default()
-    }
-
-    pub fn prefill(init: &[&str]) -> Self {
-        let mut this = Interner::new();
-        for &string in init {
-            this.intern(string);
-        }
-        this
-    }
-
-    pub fn intern(&mut self, string: &str) -> Name {
-        if let Some(&name) = self.names.get(string) {
-            return name;
-        }
-
-        let name = Name(self.strings.len() as u32);
-        let string = Rc::__from_str(string);
-        self.strings.push(string.clone());
-        self.names.insert(string, name);
-        name
-    }
-
-    pub fn gensym(&mut self, string: &str) -> Name {
-        let gensym = Name(self.strings.len() as u32);
-        // leave out of `names` to avoid colliding
-        self.strings.push(Rc::__from_str(string));
-        gensym
-    }
-
-    /// Create a gensym with the same name as an existing entry.
-    pub fn gensym_copy(&mut self, name: Name) -> Name {
-        let gensym = Name(self.strings.len() as u32);
-        // leave out of `names` to avoid colliding
-        let string = self.strings[name.0 as usize].clone();
-        self.strings.push(string);
-        gensym
-    }
-
-    pub fn get(&self, name: Name) -> Rc<str> {
-        self.strings[name.0 as usize].clone()
-    }
-
-    pub fn find(&self, string: &str) -> Option<Name> {
-        self.names.get(string).cloned()
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use ast::Name;
-
-    #[test]
-    fn interner_tests() {
-        let mut i: Interner = Interner::new();
-        // first one is zero:
-        assert_eq!(i.intern("dog"), Name(0));
-        // re-use gets the same entry:
-        assert_eq!(i.intern ("dog"), Name(0));
-        // different string gets a different #:
-        assert_eq!(i.intern("cat"), Name(1));
-        assert_eq!(i.intern("cat"), Name(1));
-        // dog is still at zero
-        assert_eq!(i.intern("dog"), Name(0));
-        // gensym gets 3
-        assert_eq!(i.gensym("zebra"), Name(2));
-        // gensym of same string gets new number :
-        assert_eq!(i.gensym("zebra"), Name(3));
-        // gensym of *existing* string gets new number:
-        assert_eq!(i.gensym("dog"), Name(4));
-        // gensym tests again with gensym_copy:
-        assert_eq!(i.gensym_copy(Name(2)), Name(5));
-        assert_eq!(&*i.get(Name(5)), "zebra");
-        assert_eq!(i.gensym_copy(Name(2)), Name(6));
-        assert_eq!(&*i.get(Name(6)), "zebra");
-        assert_eq!(&*i.get(Name(0)), "dog");
-        assert_eq!(&*i.get(Name(1)), "cat");
-        assert_eq!(&*i.get(Name(2)), "zebra");
-        assert_eq!(&*i.get(Name(3)), "zebra");
-        assert_eq!(&*i.get(Name(4)), "dog");
-    }
-}
diff --git a/src/libsyntax/util/lev_distance.rs b/src/libsyntax/util/lev_distance.rs
index e0796c34e57..a6fff2d7074 100644
--- a/src/libsyntax/util/lev_distance.rs
+++ b/src/libsyntax/util/lev_distance.rs
@@ -8,9 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use ast::Name;
 use std::cmp;
-use parse::token::InternedString;
+use symbol::Symbol;
 
 /// To find the Levenshtein distance between two strings
 pub fn lev_distance(a: &str, b: &str) -> usize {
@@ -48,14 +47,14 @@ pub fn lev_distance(a: &str, b: &str) -> usize {
 /// to one-third of the given word
 pub fn find_best_match_for_name<'a, T>(iter_names: T,
                                        lookup: &str,
-                                       dist: Option<usize>) -> Option<InternedString>
-    where T: Iterator<Item = &'a Name> {
+                                       dist: Option<usize>) -> Option<Symbol>
+    where T: Iterator<Item = &'a Symbol> {
     let max_dist = dist.map_or_else(|| cmp::max(lookup.len(), 3) / 3, |d| d);
     iter_names
-    .filter_map(|name| {
+    .filter_map(|&name| {
         let dist = lev_distance(lookup, &name.as_str());
         match dist <= max_dist {    // filter the unwanted cases
-            true => Some((name.as_str(), dist)),
+            true => Some((name, dist)),
             false => None,
         }
     })
diff --git a/src/libsyntax/util/parser.rs b/src/libsyntax/util/parser.rs
index df4eb1c9ed7..ce24fe1eb61 100644
--- a/src/libsyntax/util/parser.rs
+++ b/src/libsyntax/util/parser.rs
@@ -7,7 +7,8 @@
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
-use parse::token::{Token, BinOpToken, keywords};
+use parse::token::{Token, BinOpToken};
+use symbol::keywords;
 use ast::BinOpKind;
 
 /// Associative operator with precedence.
diff --git a/src/libsyntax/util/parser_testing.rs b/src/libsyntax/util/parser_testing.rs
index 76d3f2a063c..e703dc6b419 100644
--- a/src/libsyntax/util/parser_testing.rs
+++ b/src/libsyntax/util/parser_testing.rs
@@ -8,11 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use ast;
+use ast::{self, Ident};
 use parse::{ParseSess,PResult,filemap_to_tts};
 use parse::{lexer, new_parser_from_source_str};
 use parse::parser::Parser;
-use parse::token;
 use ptr::P;
 use tokenstream;
 use std::iter::Peekable;
@@ -78,9 +77,9 @@ pub fn string_to_pat(source_str: String) -> P<ast::Pat> {
     })
 }
 
-/// Convert a vector of strings to a vector of ast::Ident's
-pub fn strs_to_idents(ids: Vec<&str> ) -> Vec<ast::Ident> {
-    ids.iter().map(|u| token::str_to_ident(*u)).collect()
+/// Convert a vector of strings to a vector of Ident's
+pub fn strs_to_idents(ids: Vec<&str> ) -> Vec<Ident> {
+    ids.iter().map(|u| Ident::from_str(*u)).collect()
 }
 
 /// Does the given string match the pattern? whitespace in the first string