[parser] Fix parsing of escaped line terminator sequences.

R=marja@chromium.org
CC=adamk@chromium.org
Bug=v8:6401

Change-Id: Iac47c149d8c9136f4d0f5ef9844d2eaa95c2e497
Reviewed-on: https://chromium-review.googlesource.com/508696
Commit-Queue: Daniel Vogelheim <vogelheim@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45741}

src/parsing/scanner.cc

@@ -983,10 +983,8 @@ bool Scanner::ScanEscape() {
   // Skip escaped newlines.
   if (!in_template_literal && c0_ != kEndOfInput &&
       unicode_cache_->IsLineTerminator(c)) {
-    // Allow CR+LF newlines in multiline string literals.
+    // Allow escaped CR+LF newlines in multiline string literals.
     if (IsCarriageReturn(c) && IsLineFeed(c0_)) Advance<capture_raw>();
-    // Allow LF+CR newlines in multiline string literals.
-    if (IsLineFeed(c) && IsCarriageReturn(c0_)) Advance<capture_raw>();
     return true;
   }
 

test/mjsunit/newline-in-string.js

@@ -35,10 +35,14 @@ var str = 'asdf\
 ';
 assertEquals('asdf\nasdf\rasdf\tasdf\\', str);
 
-// Allow CR+LF in multiline string literals.
+// Allow escaped CR+LF in multiline string literals.
 var code = "'asdf\\" + String.fromCharCode(0xD) + String.fromCharCode(0xA) + "asdf'";
-assertEquals('asdfasdf', eval(code));
+assertEquals("asdfasdf", eval(code));
 
-// Allow LF+CR in multiline string literals.
+// Allow individually escaped LF+CR in multiline string literals.
+code = "'asdf\\" + String.fromCharCode(0xA) + "\\" + String.fromCharCode(0xD) + "asdf'";
+assertEquals("asdfasdf", eval(code));
+
+// Do not allow LF+CR in multiline string literals. (crbug.com/v8/6401)
 code = "'asdf\\" + String.fromCharCode(0xA) + String.fromCharCode(0xD) + "asdf'";
-assertEquals('asdfasdf', eval(code));
+assertThrows(code);