Support unicode superscripts

src/doc/grammar.md

@@ -108,7 +108,7 @@ the following form:
   gated. This is expected to improve soon.
 
 - The first character has property `XID_start`
-- The remaining characters have property `XID_continue`
+- The remaining characters have property `XID_continue` or is a superscript
 
 that does _not_ occur in the set of [keywords](#keywords).
 
@@ -281,7 +281,7 @@ type_path_tail : '<' type_expr [ ',' type_expr ] + '>'
 ## Macros
 
 ```antlr
-expr_macro_rules : "macro_rules" '!' ident '(' macro_rule * ')' ';' 
+expr_macro_rules : "macro_rules" '!' ident '(' macro_rule * ')' ';'
                  | "macro_rules" '!' ident '{' macro_rule * '}' ;
 macro_rule : '(' matcher * ')' "=>" '(' transcriber * ')' ';' ;
 matcher : '(' matcher * ')' | '[' matcher * ']'

src/libfmt_macros/lib.rs

@@ -402,7 +402,7 @@ impl<'a> Parser<'a> {
         let mut end;
         loop {
             match self.cur.clone().next() {
-                Some((_, c)) if c.is_xid_continue() => {
+                Some((_, c)) if c.is_xid_continue() || c.is_superscript() => {
                     self.cur.next();
                 }
                 Some((pos, _)) => { end = pos; break }

src/librustc_unicode/char.rs

@@ -385,6 +385,14 @@ impl char {
     #[inline]
     pub fn is_xid_continue(self) -> bool { derived_property::XID_Continue(self) }
 
+    /// Returns whether the specified `char` is a superscript character in the
+    /// ['Superscripts and Subscripts' unicode block]
+    /// (https://en.wikipedia.org/wiki/Superscripts_and_Subscripts)
+    #[unstable(feature = "unicode",
+               reason = "mainly needed for compiler internals")]
+    #[inline]
+    pub fn is_superscript(self) -> bool { derived_property::Superscript(self) }
+
     /// Indicates whether a character is in lowercase.
     ///
     /// This is defined according to the terms of the Unicode Derived Core

src/librustc_unicode/tables.rs

@@ -1147,6 +1147,14 @@ pub mod derived_property {
         super::bsearch_range_table(c, XID_Start_table)
     }
 
+    pub const Superscript_table: &'static [(char, char)] = &[
+        ('\u{b2}', '\u{b3}'), ('\u{b9}', '\u{b9}'), ('\u{2070}', '\u{2071}'),
+        ('\u{2074}', '\u{207f}')
+    ];
+
+    pub fn Superscript(c: char) -> bool {
+        super::bsearch_range_table(c, Superscript_table)
+    }
 }
 
 pub mod property {

src/libsyntax/parse/lexer/mod.rs

@@ -1396,7 +1396,7 @@ fn ident_continue(c: Option<char>) -> bool {
         || (c >= 'A' && c <= 'Z')
         || (c >= '0' && c <= '9')
         || c == '_'
-        || (c > '\x7f' && c.is_xid_continue())
+        || (c > '\x7f' && (c.is_xid_continue() || c.is_superscript()))
 }
 
 #[cfg(test)]

src/test/run-pass/unicode-superscripts.rs

@@ -0,0 +1,25 @@
+// 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.
+
+#![allow(unused_variables)]
+#![feature(non_ascii_idents)]
+
+pub fn main() {
+    let σ⁰ = 2;
+    let σ¹ = 2;
+    let σ² = 1;
+    let σ³ = 2;
+    let σ⁴ = 2;
+    let σ⁵ = 2;
+    let σ⁶ = 2;
+    let σ⁷ = 2;
+    let σ⁸ = 2;
+    let σ⁹ = 2;
+}