[parser] Lift template literal invalid escape restriction

src/parsing/scanner.h

Index: src/parsing/scanner.h
diff --git a/src/parsing/scanner.h b/src/parsing/scanner.h
index 075b9ca6b2ba0c1d9468e7eef7e3598c85a5cd36..3ff7a3c6d76241807fd17842cb735424584c9f47 100644
--- a/src/parsing/scanner.h
+++ b/src/parsing/scanner.h
@@ -209,10 +209,27 @@ class Scanner {
   // (the token last returned by Next()).
   Location location() const { return current_.location; }
 
+  // This error is specifically an invalid hex or unicode escape sequence.
   bool has_error() const { return scanner_error_ != MessageTemplate::kNone; }
   MessageTemplate::Template error() const { return scanner_error_; }
   Location error_location() const { return scanner_error_location_; }
 
+  bool has_invalid_template_escape() const {
+    return invalid_template_escape_message_ != MessageTemplate::kNone;
+  }
+  MessageTemplate::Template invalid_template_escape_message() const {
+    return invalid_template_escape_message_;
+  }
+  Location invalid_template_escape_location() const {
+    return invalid_template_escape_location_;
+  }
+
+  void clear_invalid_template_escape() {
+    DCHECK(has_invalid_template_escape());
+    invalid_template_escape_message_ = MessageTemplate::kNone;
+    invalid_template_escape_location_ = Location::invalid();
+  }
+
   // Similar functions for the upcoming token.
 
   // One token look-ahead (past the token returned by Next()).
@@ -345,6 +362,46 @@ class Scanner {
     bool complete_;
   };
 
+  // Scoped helper for saving & restoring scanner error state.
+  // This is used for tagged template literals, in which normally forbidden
+  // escape sequences are allowed.
+  class ErrorState {

[vogelheim, 2017/02/22 10:03:02]

One more nitpick: I'd prefer if this moved to scanner.cc.


Reason: The current placement is arguably more consistent with what we currently
do; it's just that our current header structure is a bit of a mess. The
LiteralBuffer + LiteralScope etc. helpers are used as class members, and are
used from a whole lot of inline code, which means one can't remove them from the
header without a significant refactoring. But the ErrorState is - at least for
now - only used within a method, and not from inlined cpde, so it doesn't have
to be in the header.

(I'm convinced we can throw out *most* of the inlining, and with that we could
also slim down the header significantly. But figuring out which bits of inlined
code are actually useful is going to be quite a bit of work, unfortunately.)

[bakkot1, 2017/02/22 20:23:53]

Sounds good to me! I'm always happier having less stuff in the headers; I only
put it there for consistency with similar classes. Done.

+   public:
+    ErrorState(MessageTemplate::Template* message_stack,
+               Location* location_stack)
+        : message_stack_(message_stack),
+          old_message_(*message_stack),
+          location_stack_(location_stack),
+          old_location_(*location_stack) {
+      *message_stack_ = MessageTemplate::kNone;
+      *location_stack_ = Location::invalid();
+    }
+
+    ~ErrorState() {
+      *message_stack_ = old_message_;
+      *location_stack_ = old_location_;
+    }
+
+    void MoveErrorTo(MessageTemplate::Template* message_dest,
+                     Location* location_dest) {
+      if (*message_stack_ == MessageTemplate::kNone) {
+        return;
+      }
+      if (*message_dest == MessageTemplate::kNone) {
+        *message_dest = *message_stack_;
+        *location_dest = *location_stack_;
+      }
+      *message_stack_ = MessageTemplate::kNone;
+      *location_stack_ = Location::invalid();
+    }
+
+   private:
+    MessageTemplate::Template* const message_stack_;
+    MessageTemplate::Template const old_message_;
+    Location* const location_stack_;
+    Location const old_location_;
+  };
+
   // LiteralBuffer -  Collector of chars of literals.
   class LiteralBuffer {
    public:
@@ -466,6 +523,7 @@ class Scanner {
     next_next_.raw_literal_chars = NULL;
     found_html_comment_ = false;
     scanner_error_ = MessageTemplate::kNone;
+    invalid_template_escape_message_ = MessageTemplate::kNone;
   }
 
   void ReportScannerError(const Location& location,
@@ -756,6 +814,9 @@ class Scanner {
 
   MessageTemplate::Template scanner_error_;
   Location scanner_error_location_;
+
+  MessageTemplate::Template invalid_template_escape_message_;
+  Location invalid_template_escape_location_;
 };
 
 }  // namespace internal