[regexp] parse RegExpUnicodeEscapeSequence according to spec.

test/mjsunit/harmony/unicode-escapes-in-regexps.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // ES6 extends the \uxxxx escape and also allows \u{xxxxx}.
 
 // Flags: --harmony-unicode-regexps --harmony-regexps
 
 function testRegexpHelper(r) {
   assertTrue(r.test("foo"));
@@ skipping 239 matching lines @@
 
 // Quantifier.
 assertTrue(new RegExp("\u{12345}{3}", "u").test("\u{12345}\u{12345}\u{12345}"));
 assertTrue(/\u{12345}{3}/u.test("\u{12345}\u{12345}\u{12345}"));
 assertTrue(new RegExp("\u{12345}{3}").test("\u{12345}\udf45\udf45"));
 assertFalse(/\ud808\udf45{3}/u.test("\u{12345}\udf45\udf45"));
 assertTrue(/\ud808\udf45{3}/u.test("\u{12345}\u{12345}\u{12345}"));
 assertFalse(new RegExp("\u{12345}{3}", "u").test("\u{12345}\udf45\udf45"));
 assertFalse(/\u{12345}{3}/u.test("\u{12345}\udf45\udf45"));
 
-// Mixed escapes and literal surrogates.
+// Literal surrogates.
 assertEquals(["\u{10000}\u{10000}"],
              new RegExp("\ud800\udc00+", "u").exec("\u{10000}\u{10000}"));
 assertEquals(["\u{10000}\u{10000}"],
              new RegExp("\\ud800\\udc00+", "u").exec("\u{10000}\u{10000}"));
-assertEquals(["\u{10000}\u{10000}"],
-             new RegExp("\\ud800\udc00+", "u").exec("\u{10000}\u{10000}"));
-assertEquals(["\u{10000}\u{10000}"],
-             new RegExp("\ud800\\udc00+", "u").exec("\u{10000}\u{10000}"));
 
 assertEquals(["\u{10003}\u{50001}"],
              new RegExp("[\\ud800\\udc03-\\ud900\\udc01\]+", "u").exec(
                  "\u{10003}\u{50001}"));
 assertEquals(["\u{10003}\u{50001}"],
-             new RegExp("[\\ud800\udc03-\ud900\\udc01\]+", "u").exec(
-                 "\u{10003}\u{50001}"));
-assertEquals(["\u{50001}"],
-             new RegExp("[\\ud800\udc03-\ud900\\udc01\]+", "u").exec(
-                 "\u{10002}\u{50001}"));
-assertEquals(["\u{10003}\u{50001}"],
              new RegExp("[\ud800\udc03-\u{50001}\]+", "u").exec(
                  "\u{10003}\u{50001}"));
+
+// Unicode escape sequences to represent a non-BMP character cannot have
+// mixed notation, and must follow the rules for RegExpUnicodeEscapeSequence.
+assertThrows(() => new RegExp("[\\ud800\udc03-\ud900\\udc01\]+", "u"));
+assertThrows(() => new RegExp("[\\ud800\udc03-\ud900\\udc01\]+", "u"));
+assertNull(new RegExp("\\ud800\udc00+", "u").exec("\u{10000}\u{10000}"));
+assertNull(new RegExp("\ud800\\udc00+", "u").exec("\u{10000}\u{10000}"));
+
+assertNull(new RegExp("[\\ud800\udc00]", "u").exec("\u{10000}"));
+assertNull(new RegExp("[\\{ud800}\udc00]", "u").exec("\u{10000}"));
+assertNull(new RegExp("[\ud800\\udc00]", "u").exec("\u{10000}"));
+assertNull(new RegExp("[\ud800\\{udc00}]", "u").exec("\u{10000}"));
+
+assertNull(/\u{d800}\u{dc00}+/u.exec("\ud800\udc00\udc00"));
+assertNull(/\ud800\u{dc00}+/u.exec("\ud800\udc00\udc00"));
+assertNull(/\u{d800}\udc00+/u.exec("\ud800\udc00\udc00"));