[parser] Lift template literal invalid escape restriction

src/parsing/scanner.cc

Index: src/parsing/scanner.cc
diff --git a/src/parsing/scanner.cc b/src/parsing/scanner.cc
index bfb5e03d68457841d0bb4e72b5632e7b97a77324..21723eb50a5ec4e0e126da79556adba0c793bf67 100644
--- a/src/parsing/scanner.cc
+++ b/src/parsing/scanner.cc
@@ -948,16 +948,12 @@ bool Scanner::ScanEscape() {
       break;
   }
 
-  // According to ECMA-262, section 7.8.4, characters not covered by the
-  // above cases should be illegal, but they are commonly handled as
-  // non-escaped characters by JS VMs.
+  // Other escaped characters are interpreted as their non-escaped version.
   AddLiteralChar(c);
   return true;
 }
 
 
-// Octal escapes of the forms '\0xx' and '\xxx' are not a part of
-// ECMA-262. Other JS VMs support them.
 template <bool capture_raw>
 uc32 Scanner::ScanOctalEscape(uc32 c, int length) {
   uc32 x = c - '0';
@@ -1039,6 +1035,7 @@ Token::Value Scanner::ScanTemplateSpan() {
   // TEMPLATE_TAIL terminates a TemplateLiteral and does not need to be
   // followed by an Expression.
 
+  DCHECK(!has_error());
   Token::Value result = Token::TEMPLATE_SPAN;
   LiteralScope literal(this);
   StartRawLiteral();
@@ -1069,8 +1066,16 @@ Token::Value Scanner::ScanTemplateSpan() {
             AddRawLiteralChar('\n');
           }
         }
-      } else if (!ScanEscape<capture_raw, in_template_literal>()) {
-        return Token::ILLEGAL;
+      } else {
+        ScanEscape<capture_raw, in_template_literal>();

[vogelheim, 2017/02/17 16:33:53]

In a template w/ two invalid escapes, this would record the position of the last
one, right?

[bakkot1, 2017/02/17 20:42:18]

It would. Fixed.

Octal literals actually have the same issue currently: we report the location of
the *last* octal literal in a string or template literal. With this patch, we
report the last in a string the first in a template literal.

Actually, that exposes a bug, which I'll document elsewhere.

+        if (has_error()) {
+          // For templates, invalid escape sequence checking is handled in the
+          // parser.
+          invalid_template_escape_message_ = scanner_error_;
+          invalid_template_escape_location_ = scanner_error_location_;
+          scanner_error_ = MessageTemplate::kNone;
+          scanner_error_location_ = Location();
+        }
       }
     } else if (c < 0) {
       // Unterminated template literal