[parser] fix token end position for regexp literals

Make the end position of a regexp literal the first character following the regexp. This matches the behaviour of number literals and string literals, as well as single-character tokens.

This change corrects the lazy-parsing of arrow functions with concise bodies, whose last token is a regular expression literal.

BUG=v8:4474
LOG=N
R=wingo@igalia.com, adamk@chromium.org, rossberg@chromium.org

Review URL: https://codereview.chromium.org/1389313003

Cr-Commit-Position: refs/heads/master@{#31189}

src/scanner.cc

@@ -1395,7 +1395,7 @@ bool Scanner::ScanRegExpFlags() {
   }
   literal.Complete();
 
-  next_.location.end_pos = source_pos() - 1;
+  next_.location.end_pos = source_pos();
   return true;
 }
 

test/mjsunit/es6/arrow-functions.js

@@ -68,3 +68,16 @@ assertEquals([5, 10], fives);
   assertThrows(function() { return arrowFn.caller; }, TypeError);
   assertThrows(function() { arrowFn.caller = {}; }, TypeError);
 })();
+
+
+// v8:4474
+(function testConciseBodyReturnsRegexp() {
+  var arrow1 = () => /foo/
+  var arrow2 = () => /foo/;
+  var arrow3 = () => /foo/i
+  var arrow4 = () => /foo/i;
+  assertEquals(arrow1.toString(), "() => /foo/");
+  assertEquals(arrow2.toString(), "() => /foo/");
+  assertEquals(arrow3.toString(), "() => /foo/i");
+  assertEquals(arrow4.toString(), "() => /foo/i");
+});