Fix error messages for multiple alias oddities.

asnarnd · Aug 25, 2014 · 466b8ba · 466b8ba
1 parent 126dd5b
commit 466b8ba
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Showing 4 changed files with 24 additions and 13 deletions.
diff --git a/ParserGenerator/ErrorHandler.cs b/ParserGenerator/ErrorHandler.cs
@@ -102,10 +102,12 @@ internal void AddWarning(int code, string msg, LexSpan spn)
         /// <param name="spn">The span to which the error is attached</param>
         /// <param name="num">The error number</param>
         /// <param name="key">The featured string</param>
-        internal void ListError(LexSpan spn, int num, string key, char quote)
-        { ListError(spn, num, key, quote, quote); }
+        internal void ListError( LexSpan spn, int num, string key, char quote ) {
+            string s = (quote == '\0' ? "" : quote.ToString());
+            ListError( spn, num, key, s, s );
+        }
 
-        void ListError(LexSpan spn, int num, string key, char lh, char rh)
+        void ListError(LexSpan spn, int num, string key, string lh, string rh)
         {
             string prefix, suffix, message;
             if (spn == null)
@@ -116,8 +118,9 @@ void ListError(LexSpan spn, int num, string key, char lh, char rh)
                 case 70: prefix = "Invalid string escape"; suffix = ""; break;
                 case 82: prefix = "Character literal"; suffix = "exceeds maximum in imported token type"; break;
                 case 83: prefix = "Key"; suffix = "was not found in token alias list"; break;
-                case 103: prefix = "Highest char literal token"; suffix = "is very large"; break;
+                case 84: prefix = "Ambiguous alias"; suffix = "has multiple definitions "; break;
 
+                case 103: prefix = "Highest char literal token"; suffix = "is very large"; break;
                 default: prefix = "Error " + Convert.ToString(num, CultureInfo.InvariantCulture); suffix = "";
                     break;
             }

diff --git a/ParserGenerator/Grammar.cs b/ParserGenerator/Grammar.cs
@@ -107,18 +107,21 @@ internal Terminal LookupOrDefineTerminal(Token token, string name, string alias,
 
         private void CheckAndSetAlias( string alias, Terminal terminal, LexSpan span ) {
             //
-            // Terminal not known in collection
+            // Check if this alias already known.
             //
             if (aliasTerms.ContainsKey( alias )) {
                 //
-                // It is an error if an alias denotes more than one logical token
+                // If an alias denotes more than one logical token then used 
+                // occurrences of the literal string alias must be disallowed. 
                 //
                 Terminal other = aliasTerms[alias];
-                if (other != terminal)
+                if (other != terminal) {
                     handler.AddWarning( 153,
                             String.Format( CultureInfo.InvariantCulture,
-                            "Alias \"{0}\" also used for previous token: {1}",
-                            alias, other.BaseString()), span );
+                            "Alias \"{0}\" also used for previous token: {1}, used occurrences forbidden",
+                            alias, other.BaseString() ), span ); 
+                    aliasTerms[alias] = Terminal.Ambiguous;
+                }
             }
             else {
                 aliasTerms[alias] = terminal;

diff --git a/ParserGenerator/ParseHelper.cs b/ParserGenerator/ParseHelper.cs
@@ -223,19 +223,22 @@ private void AddSymbolsToProduction( Production prod, List<string> list ) {
                     Symbol symbol = null;
 
                     switch (TokenOf( str )) {
-                        case Token.litchar:
+                        case Token.litchar: // This is a character literal symbol
                             if (GPCG.ImportedTokens && Terminal.BumpsMax( str ))
                                 handler.ListError( this.CurrentLocationSpan, 82, str, '\0' );
                             symbol = grammar.LookupTerminal( Token.litchar, str );
                             break;
-                        case Token.litstring:
+                        case Token.litstring: // This is a uned occurrence of a terminal alias.
                             String s = CharacterUtilities.CanonicalizeAlias( str );
                             if (!grammar.aliasTerms.ContainsKey( s ))
                                 handler.ListError( this.CurrentLocationSpan, 83, str, '\0' );
-                            else
+                            else {
                                 symbol = grammar.aliasTerms[s];
+                                if (symbol == Terminal.Ambiguous) // Use of an ambiguous alias.
+                                    handler.ListError( this.CurrentLocationSpan, 84, str, '\0' );
+                            }                                                
                             break;
-                        case Token.ident:
+                        case Token.ident: // This is a used occurrence of a terminal name.
                             if (grammar.terminals.ContainsKey( str ))
                                 symbol = grammar.terminals[str];
                             else

diff --git a/ParserGenerator/Symbol.cs b/ParserGenerator/Symbol.cs
@@ -86,6 +86,8 @@ internal Terminal(bool symbolic, string name)
 			}
 		}
 
+        internal static readonly Terminal Ambiguous = new Terminal( true, "$Ambiguous$" );
+
         internal Terminal(bool symbolic, string name, string alias) 
             : this(symbolic, name)
         {
-Original file line number
+Diff line change
@@ Expand Up / @@ -86,6 +86,8 @@ internal Terminal(bool symbolic, string name) @@
     			}
     		}
+            internal static readonly Terminal Ambiguous = new Terminal( true, "$Ambiguous$" );
             internal Terminal(bool symbolic, string name, string alias)
                 : this(symbolic, name)
             {
@@ Expand Down @@