PEG.buildParser reports missing referenced rules.

lib/compiler.js

@@ -38,6 +38,9 @@ PEG.buildParser = function(grammar, startRule) {
       throw new PEG.Grammar.GrammarError("Grammar must be object or string.");
   }
 
+  for (var key in ast) {
+    ast[key].checkReferencedRulesExist(ast);
+  }
   if (ast[startRule] === undefined) {
     throw new PEG.Grammar.GrammarError("Missing \"" + startRule + "\" rule.");
   }
@@ -97,6 +100,46 @@ PEG.Grammar.Action = function(expression, action) {
   this._action   = action;
 };
 
+/* ===== Referenced Rule Existence Checks ===== */
+
+PEG.Grammar.Rule.prototype.checkReferencedRulesExist = function(grammar) {
+  this._expression.checkReferencedRulesExist(grammar);
+};
+
+PEG.Grammar.Literal.prototype.checkReferencedRulesExist = function(grammar) {};
+
+PEG.Grammar.Any.prototype.checkReferencedRulesExist = function(grammar) {};
+
+PEG.Grammar.Sequence.prototype.checkReferencedRulesExist = function(grammar) {
+  PEG.ArrayUtils.each(this._elements, function(element) {
+    element.checkReferencedRulesExist(grammar);
+  });
+};
+
+PEG.Grammar.Choice.prototype.checkReferencedRulesExist = function(grammar) {
+  PEG.ArrayUtils.each(this._alternatives, function(alternative) {
+    alternative.checkReferencedRulesExist(grammar);
+  });
+};
+
+PEG.Grammar.ZeroOrMore.prototype.checkReferencedRulesExist = function(grammar) {
+  this._element.checkReferencedRulesExist(grammar);
+};
+
+PEG.Grammar.NotPredicate.prototype.checkReferencedRulesExist = function(grammar) {
+  this._expression.checkReferencedRulesExist(grammar);
+};
+
+PEG.Grammar.RuleRef.prototype.checkReferencedRulesExist = function(grammar) {
+  if (grammar[this._name] === undefined) {
+    throw new PEG.Grammar.GrammarError("Referenced rule \"" + this._name + "\" does not exist.");
+  }
+};
+
+PEG.Grammar.Action.prototype.checkReferencedRulesExist = function(grammar) {
+  this._expression.checkReferencedRulesExist(grammar);
+};
+
 /* ===== PEG.Compiler ===== */
 
 PEG.Compiler = {

test/compiler-test.js

@@ -113,6 +113,24 @@ test("buildParser reports missing start rule", function() {
   throws(function() { PEG.buildParser({}); }, PEG.Grammar.GrammarError);
 });
 
+test("buildParser reports missing referenced rules", function() {
+  var grammars = [
+    'start: missing',
+    'start: missing "a" "b"',
+    'start: "a" "b" missing',
+    'start: missing | "a" | "b"',
+    'start: "a" | "b" | missing',
+    'start: missing*',
+    'start: !missing',
+    'start: &missing',
+    'start: missing { }'
+  ];
+
+  PEG.ArrayUtils.each(grammars, function(grammar) {
+    throws(function() { PEG.buildParser(grammar); }, PEG.Grammar.GrammarError);
+  });
+});
+
 test("buildParser allows custom start rule", function() {
   var parser = PEG.buildParser('s: "abcd"', "s");
   parses(parser, "abcd", "abcd");