Ejemplo n.º 1
0
        /** <summary>Attempt to recover from a single missing or extra token.</summary>
         *
         *  EXTRA TOKEN
         *
         *  LA(1) is not what we are looking for.  If LA(2) has the right token,
         *  however, then assume LA(1) is some extra spurious token.  Delete it
         *  and LA(2) as if we were doing a normal match(), which advances the
         *  input.
         *
         *  MISSING TOKEN
         *
         *  If current token is consistent with what could come after
         *  ttype then it is ok to "insert" the missing token, else throw
         *  exception For example, Input "i=(3;" is clearly missing the
         *  ')'.  When the parser returns from the nested call to expr, it
         *  will have call chain:
         *
         *    stat -> expr -> atom
         *
         *  and it will be trying to match the ')' at this point in the
         *  derivation:
         *
         *       => ID '=' '(' INT ')' ('+' atom)* ';'
         *                          ^
         *  match() will see that ';' doesn't match ')' and report a
         *  mismatched token error.  To recover, it sees that LA(1)==';'
         *  is in the set of tokens that can follow the ')' token
         *  reference in rule atom.  It can assume that you forgot the ')'.
         */
        protected virtual object RecoverFromMismatchedToken(IIntStream input, int ttype, BitSet follow)
        {
            RecognitionException e = null;

            // if next token is what we are looking for then "delete" this token
            if (MismatchIsUnwantedToken(input, ttype))
            {
                e = new UnwantedTokenException(ttype, input, TokenNames);

                /*
                 * System.err.println("recoverFromMismatchedToken deleting "+
                 *                 ((TokenStream)input).LT(1)+
                 *                 " since "+((TokenStream)input).LT(2)+" is what we want");
                 */
                BeginResync();
                input.Consume(); // simply delete extra token
                EndResync();
                ReportError(e);  // report after consuming so AW sees the token in the exception
                // we want to return the token we're actually matching
                object matchedSymbol = GetCurrentInputSymbol(input);
                input.Consume(); // move past ttype token as if all were ok
                return(matchedSymbol);
            }
            // can't recover with single token deletion, try insertion
            if (MismatchIsMissingToken(input, follow))
            {
                object inserted = GetMissingSymbol(input, e, ttype, follow);
                e = new MissingTokenException(ttype, input, inserted);
                ReportError(e);    // report after inserting so AW sees the token in the exception
                return(inserted);
            }
            // even that didn't work; must throw the exception
            e = new MismatchedTokenException(ttype, input, TokenNames);
            throw e;
        }
Ejemplo n.º 2
0
        /** <summary>What error message should be generated for the various exception types?</summary>
         *
         *  <remarks>
         *  Not very object-oriented code, but I like having all error message
         *  generation within one method rather than spread among all of the
         *  exception classes. This also makes it much easier for the exception
         *  handling because the exception classes do not have to have pointers back
         *  to this object to access utility routines and so on. Also, changing
         *  the message for an exception type would be difficult because you
         *  would have to subclassing exception, but then somehow get ANTLR
         *  to make those kinds of exception objects instead of the default.
         *  This looks weird, but trust me--it makes the most sense in terms
         *  of flexibility.
         *
         *  For grammar debugging, you will want to override this to add
         *  more information such as the stack frame with
         *  getRuleInvocationStack(e, this.getClass().getName()) and,
         *  for no viable alts, the decision description and state etc...
         *
         *  Override this to change the message generated for one or more
         *  exception types.
         *  </remarks>
         */
        public virtual string GetErrorMessage(RecognitionException e, string[] tokenNames)
        {
            string msg = e.Message;

            if (e is UnwantedTokenException)
            {
                UnwantedTokenException ute = (UnwantedTokenException)e;
                string tokenName           = "<unknown>";
                if (ute.Expecting == TokenTypes.EndOfFile)
                {
                    tokenName = "EndOfFile";
                }
                else
                {
                    tokenName = tokenNames[ute.Expecting];
                }
                msg = "extraneous input " + GetTokenErrorDisplay(ute.UnexpectedToken) +
                      " expecting " + tokenName;
            }
            else if (e is MissingTokenException)
            {
                MissingTokenException mte = (MissingTokenException)e;
                string tokenName          = "<unknown>";
                if (mte.Expecting == TokenTypes.EndOfFile)
                {
                    tokenName = "EndOfFile";
                }
                else
                {
                    tokenName = tokenNames[mte.Expecting];
                }
                msg = "missing " + tokenName + " at " + GetTokenErrorDisplay(e.Token);
            }
            else if (e is MismatchedTokenException)
            {
                MismatchedTokenException mte = (MismatchedTokenException)e;
                string tokenName             = "<unknown>";
                if (mte.Expecting == TokenTypes.EndOfFile)
                {
                    tokenName = "EndOfFile";
                }
                else
                {
                    tokenName = tokenNames[mte.Expecting];
                }
                msg = "mismatched input " + GetTokenErrorDisplay(e.Token) +
                      " expecting " + tokenName;
            }
            else if (e is MismatchedTreeNodeException)
            {
                MismatchedTreeNodeException mtne = (MismatchedTreeNodeException)e;
                string tokenName = "<unknown>";
                if (mtne.Expecting == TokenTypes.EndOfFile)
                {
                    tokenName = "EndOfFile";
                }
                else
                {
                    tokenName = tokenNames[mtne.Expecting];
                }
                // workaround for a .NET framework bug (NullReferenceException)
                string nodeText = (mtne.Node != null) ? mtne.Node.ToString() ?? string.Empty : string.Empty;
                msg = "mismatched tree node: " + nodeText + " expecting " + tokenName;
            }
            else if (e is NoViableAltException)
            {
                //NoViableAltException nvae = (NoViableAltException)e;
                // for development, can add "decision=<<"+nvae.grammarDecisionDescription+">>"
                // and "(decision="+nvae.decisionNumber+") and
                // "state "+nvae.stateNumber
                msg = "no viable alternative at input " + GetTokenErrorDisplay(e.Token);
            }
            else if (e is EarlyExitException)
            {
                //EarlyExitException eee = (EarlyExitException)e;
                // for development, can add "(decision="+eee.decisionNumber+")"
                msg = "required (...)+ loop did not match anything at input " +
                      GetTokenErrorDisplay(e.Token);
            }
            else if (e is MismatchedSetException)
            {
                MismatchedSetException mse = (MismatchedSetException)e;
                msg = "mismatched input " + GetTokenErrorDisplay(e.Token) +
                      " expecting set " + mse.Expecting;
            }
            else if (e is MismatchedNotSetException)
            {
                MismatchedNotSetException mse = (MismatchedNotSetException)e;
                msg = "mismatched input " + GetTokenErrorDisplay(e.Token) +
                      " expecting set " + mse.Expecting;
            }
            else if (e is FailedPredicateException)
            {
                FailedPredicateException fpe = (FailedPredicateException)e;
                msg = "rule " + fpe.RuleName + " failed predicate: {" +
                      fpe.PredicateText + "}?";
            }
            return(msg);
        }