Report left recursion and infinite loops only as "possible"

A semantic predicate can prevent the parser to actually enter infinite
recursion or loop. This is undetectable at compile-time.

lib/compiler/passes/report-infinite-loops.js

@@ -12,13 +12,13 @@ function reportInfiniteLoops(ast) {
   var check = visitor.build({
     zero_or_more: function(node) {
       if (!asts.alwaysConsumesOnSuccess(ast, node.expression)) {
-        throw new GrammarError("Infinite loop detected.", node.location);
+        throw new GrammarError("Possible infinite loop detected.", node.location);
       }
     },
 
     one_or_more: function(node) {
       if (!asts.alwaysConsumesOnSuccess(ast, node.expression)) {
-        throw new GrammarError("Infinite loop detected.", node.location);
+        throw new GrammarError("Possible infinite loop detected.", node.location);
       }
     }
   });

lib/compiler/passes/report-left-recursion.js

@@ -38,7 +38,7 @@ function reportLeftRecursion(ast) {
     rule_ref: function(node) {
       if (arrays.contains(visitedRules, node.name)) {
         throw new GrammarError(
-          "Left recursion detected for rule \"" + node.name + "\".",
+          "Possible left recursion detected for rule \"" + node.name + "\".",
           node.location
         );
       }

spec/unit/compiler/passes/report-infinite-loops.spec.js

@@ -8,7 +8,7 @@ describe("compiler pass |reportInfiniteLoops|", function() {
 
   it("reports infinite loops for zero_or_more", function() {
     expect(pass).toReportError('start = ("")*', {
-      message:  "Infinite loop detected.",
+      message:  "Possible infinite loop detected.",
       location: {
         start: { offset:  8, line: 1, column:  9 },
         end:   { offset: 13, line: 1, column: 14 }
@@ -18,7 +18,7 @@ describe("compiler pass |reportInfiniteLoops|", function() {
 
   it("reports infinite loops for one_or_more", function() {
     expect(pass).toReportError('start = ("")+', {
-      message:  "Infinite loop detected.",
+      message:  "Possible infinite loop detected.",
       location: {
         start: { offset:  8, line: 1, column:  9 },
         end:   { offset: 13, line: 1, column: 14 }

spec/unit/compiler/passes/report-left-recursion.spec.js

@@ -8,7 +8,7 @@ describe("compiler pass |reportLeftRecursion|", function() {
 
   it("reports direct left recursion", function() {
     expect(pass).toReportError('start = start', {
-      message:  'Left recursion detected for rule \"start\".',
+      message:  'Possible left recursion detected for rule \"start\".',
       location: {
         start: { offset:  8, line: 1, column:  9 },
         end:   { offset: 13, line: 1, column: 14 }
@@ -21,7 +21,7 @@ describe("compiler pass |reportLeftRecursion|", function() {
       'start = stop',
       'stop  = start'
     ].join("\n"), {
-      message:  'Left recursion detected for rule \"start\".',
+      message:  'Possible left recursion detected for rule \"start\".',
       location: {
         start: { offset: 21, line: 2, column:  9 },
         end:   { offset: 26, line: 2, column: 14 }