Implement ES6 unicode escapes.

src/scanner.cc

Index: src/scanner.cc
diff --git a/src/scanner.cc b/src/scanner.cc
index ddcd937584d50fc45fa921a25e2a5d21fcf5697e..9da2756b8b68480ca0bfe4446b7a26c03308b604 100644
--- a/src/scanner.cc
+++ b/src/scanner.cc
@@ -694,7 +694,7 @@ bool Scanner::ScanEscape() {
     case 'r' : c = '\r'; break;
     case 't' : c = '\t'; break;
     case 'u' : {
-      c = ScanHexNumber(4);
+      c = ScanUnicodeEscape();
       if (c < 0) return false;
       break;
     }
@@ -887,7 +887,28 @@ uc32 Scanner::ScanIdentifierUnicodeEscape() {
   Advance();
   if (c0_ != 'u') return -1;
   Advance();
-  return ScanHexNumber(4);
+  return ScanUnicodeEscape();
+}
+
+
+uc32 Scanner::ScanUnicodeEscape() {
+  // Accept both \uxxxx and \u{xxxx}. \ and u have already been read.
+  bool has_brace = false;
+  if (c0_ == '{') {
+    has_brace = true;
+    Advance();
+  }
+  uc32 c = ScanHexNumber(4);

[arv (Not doing code reviews), 2014/11/07 16:23:20]

In case of u{ then there is no upper limit for the number of hex digits.

[caitp (gmail), 2014/11/07 16:23:55]

If `has_brace` is true, we want the HexDigits non-terminal, which is not limited
to 4 digits (as I'm reading it) --- as opposed to `Hex4Digits` non-terminal
which should be exactly 4 digits.

I guess arv beat me to it :>

[marja, 2014/11/13 11:53:20]

Done.

+  if (c < 0) {
+    return c;
+  }
+  if (has_brace) {
+    if (c0_ != '}') {
+      return 1;

[caitp (gmail), 2014/11/07 16:50:39]

shouldn't this return -1 so that the scanner knows it's a bad token? otherwise
it looks the same as \u{1}

[marja, 2014/11/13 11:53:20]

Done.

+    }
+    Advance();
+  }
+  return c;
 }