libsyntax: use char::is_whitespace instead of custom implementations

Fixes #29590.

src/libsyntax/parse/lexer/mod.rs

@@ -1592,10 +1592,7 @@ impl<'a> StringReader<'a> {
 }
 
 pub fn is_whitespace(c: Option<char>) -> bool {
-    match c.unwrap_or('\x00') { // None can be null for now... it's not whitespace
-        ' ' | '\n' | '\t' | '\r' => true,
-        _ => false,
-    }
+    c.map_or(false, char::is_whitespace)
 }
 
 fn in_range(c: Option<char>, lo: char, hi: char) -> bool {

src/libsyntax/util/parser_testing.rs

@@ -140,9 +140,8 @@ fn scan_for_non_ws_or_end(a : &str, idx: usize) -> usize {
     i
 }
 
-/// Copied from lexer.
 pub fn is_whitespace(c: char) -> bool {
-    return c == ' ' || c == '\t' || c == '\r' || c == '\n';
+    c.is_whitespace()
 }
 
 #[cfg(test)]

src/test/run-pass/parser-unicode-whitespace.rs

@@ -0,0 +1,18 @@
+// Copyright 2015 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.
+
+
+// Beware editing: it has numerous whitespace characters which are important
+pub fn main() {
+    assert_eq!(4 + 　7 * 2
+
+
+/ 3 * 2 , 4 + 7 * 2 / 3 * 2);
+}