[parser] Lift template literal invalid escape restriction

src/parsing/scanner.h

 // Copyright 2011 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.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #ifndef V8_PARSING_SCANNER_H_
 #define V8_PARSING_SCANNER_H_
 
 #include "src/allocation.h"
@@ skipping 191 matching lines @@
   // Returns the next token and advances input.
   Token::Value Next();
   // Returns the token following peek()
   Token::Value PeekAhead();
   // Returns the current token again.
   Token::Value current_token() { return current_.token; }
   // Returns the location information for the current token
   // (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()).
   Token::Value peek() const { return next_.token; }
 
   Location peek_location() const { return next_.location; }
 
   bool literal_contains_escapes() const {
     return LiteralContainsEscapes(current_);
   }
@@ skipping 112 matching lines @@
     ~LiteralScope() {
       if (!complete_) scanner_->DropLiteral();
     }
     void Complete() { complete_ = true; }
 
    private:
     Scanner* 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:
     LiteralBuffer() : is_one_byte_(true), position_(0), backing_store_() {}
 
     ~LiteralBuffer() { backing_store_.Dispose(); }
 
     INLINE(void AddChar(char code_unit)) {
       DCHECK(IsValidAscii(code_unit));
       AddOneByteChar(static_cast<byte>(code_unit));
@@ skipping 101 matching lines @@
     current_.literal_chars = NULL;
     current_.raw_literal_chars = NULL;
     next_.token = Token::UNINITIALIZED;
     next_.literal_chars = NULL;
     next_.raw_literal_chars = NULL;
     next_next_.token = Token::UNINITIALIZED;
     next_next_.literal_chars = NULL;
     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,
                           MessageTemplate::Template error) {
     if (has_error()) return;
     scanner_error_ = error;
     scanner_error_location_ = location;
   }
 
   void ReportScannerError(int pos, MessageTemplate::Template error) {
@@ skipping 270 matching lines @@
   // Whether there is a multi-line comment that contains a
   // line-terminator after the current token, and before the next.
   bool has_multiline_comment_before_next_;
   bool has_line_terminator_after_next_;
 
   // Whether this scanner encountered an HTML comment.
   bool found_html_comment_;
 
   MessageTemplate::Template scanner_error_;
   Location scanner_error_location_;
+
+  MessageTemplate::Template invalid_template_escape_message_;
+  Location invalid_template_escape_location_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_SCANNER_H_