Add edition keywords, use for async/await

fixes #49610

Author: Manishearth

src/libsyntax/edition.rs

@@ -10,6 +10,7 @@
 
 use std::fmt;
 use std::str::FromStr;
+use symbol::{self, Symbol};
 
 /// The edition of the compiler (RFC 2052)
 #[derive(Clone, Copy, Hash, PartialOrd, Ord, Eq, PartialEq, Debug)]
@@ -56,6 +57,13 @@ impl Edition {
         }
     }
 
+    pub fn is_future_edition_keyword(&self, sym: Symbol) -> bool {
+        match *self {
+            Edition::Edition2015 => symbol::is_future_edition_keyword_2015(sym),
+            Edition::Edition2018 => symbol::is_future_edition_keyword_2018(sym),
+        }
+    }
+
     pub fn feature_name(&self) -> &'static str {
         match *self {
             Edition::Edition2015 => "rust_2015_preview",

src/libsyntax/parse/lexer/mod.rs

@@ -1117,7 +1117,7 @@ impl<'a> StringReader<'a> {
         let c = self.ch;
 
         if ident_start(c) {
-            let (is_ident_start, is_raw_ident) =
+            let (is_ident_start, mut is_raw_ident) =
                 match (c.unwrap(), self.nextch(), self.nextnextch()) {
                     // r# followed by an identifier starter is a raw identifier.
                     // This is an exception to the r# case below.
@@ -1155,9 +1155,13 @@ impl<'a> StringReader<'a> {
                             &format!("`r#{}` is not currently supported.", ident.name)
                         ).raise();
                     }
+
                     if is_raw_ident {
                         let span = self.mk_sp(raw_start, self.pos);
                         self.sess.raw_identifier_spans.borrow_mut().push(span);
+                    } else if self.sess.edition.is_future_edition_keyword(ident.name) {
+                        // we pretend these are raw even if they aren't
+                        is_raw_ident = true;
                     }
                     token::Ident(ident, is_raw_ident)
                 }));

src/libsyntax/parse/token.rs

@@ -148,21 +148,7 @@ pub fn is_raw_guess(ident: ast::Ident) -> bool {
     is_reserved_ident(ident) && !is_path_segment_keyword(ident)
 }
 
-// Returns true for reserved identifiers used internally for elided lifetimes,
-// unnamed method parameters, crate root module, error recovery etc.
-pub fn is_special_ident(id: ast::Ident) -> bool {
-    id.name <= keywords::Underscore.name()
-}
-
-/// Returns `true` if the token is a keyword used in the language.
-pub fn is_used_keyword(id: ast::Ident) -> bool {
-    id.name >= keywords::As.name() && id.name <= keywords::While.name()
-}
-
-/// Returns `true` if the token is a keyword reserved for possible future use.
-pub fn is_unused_keyword(id: ast::Ident) -> bool {
-    id.name >= keywords::Abstract.name() && id.name <= keywords::Yield.name()
-}
+pub use syntax_pos::symbol::{is_special_ident, is_used_keyword, is_unused_keyword};
 
 /// Returns `true` if the token is either a special identifier or a keyword.
 pub fn is_reserved_ident(id: ast::Ident) -> bool {

src/libsyntax_pos/symbol.rs

@@ -325,6 +325,9 @@ declare_keywords! {
     (37, Use,                "use")
     (38, Where,              "where")
     (39, While,              "while")
+    // edition-gated used keywords go here
+    // be sure to update is_used_keyword and
+    // is_future_edition_keyword_* below
 
     // Keywords reserved for future use.
     (40, Abstract,           "abstract")
@@ -343,17 +346,45 @@ declare_keywords! {
     (53, Unsized,            "unsized")
     (54, Virtual,            "virtual")
     (55, Yield,              "yield")
+    // edition-gated reserved keywords
+    // be sure to update is_unused_keyword and
+    // is_future_edition_keyword_* below
+    (56, Async,              "async") // Rust 2018+ only
 
     // Special lifetime names
-    (56, UnderscoreLifetime, "'_")
-    (57, StaticLifetime,     "'static")
+    (57, UnderscoreLifetime, "'_")
+    (58, StaticLifetime,     "'static")
 
     // Weak keywords, have special meaning only in specific contexts.
-    (58, Auto,               "auto")
-    (59, Catch,              "catch")
-    (60, Default,            "default")
-    (61, Dyn,                "dyn")
-    (62, Union,              "union")
+    (59, Auto,               "auto")
+    (60, Catch,              "catch")
+    (61, Default,            "default")
+    (62, Dyn,                "dyn")
+    (63, Union,              "union")
+}
+
+// Returns true for reserved identifiers used internally for elided lifetimes,
+// unnamed method parameters, crate root module, error recovery etc.
+pub fn is_special_ident(id: Ident) -> bool {
+    id.name <= self::keywords::Underscore.name()
+}
+
+/// Returns `true` if the token is a keyword used in the language.
+pub fn is_used_keyword(id: Ident) -> bool {
+    id.name >= self::keywords::As.name() && id.name <= self::keywords::While.name()
+}
+
+/// Returns `true` if the token is a keyword reserved for possible future use.
+pub fn is_unused_keyword(id: Ident) -> bool {
+    id.name >= self::keywords::Abstract.name() && id.name <= self::keywords::Async.name()
+}
+
+pub fn is_future_edition_keyword_2015(sym: Symbol) -> bool {
+    sym == self::keywords::Async.name()
+}
+
+pub fn is_future_edition_keyword_2018(_: Symbol) -> bool {
+    false
 }
 
 // If an interner exists, return it. Otherwise, prepare a fresh one.