More effectively guard against infinite recursion in Type.toString

Issue #523

Author: marijnh

lib/infer.js

@@ -498,7 +498,8 @@
   Obj.prototype = extend(Type.prototype, {
     constructor: Obj,
     toString: function(maxDepth) {
-      if (!maxDepth && this.name) return this.name;
+      if (maxDepth == null) maxDepth = 0;
+      if (maxDepth <= 0 && this.name) return this.name;
       var props = [], etc = false;
       for (var prop in this.props) if (prop != "<i>") {
         if (props.length > 5) { etc = true; break; }
@@ -626,17 +627,17 @@
   Fn.prototype = extend(Obj.prototype, {
     constructor: Fn,
     toString: function(maxDepth) {
-      if (maxDepth) maxDepth--;
+      if (maxDepth == null) maxDepth = 0;
       var str = "fn(";
       for (var i = 0; i < this.args.length; ++i) {
         if (i) str += ", ";
         var name = this.argNames[i];
         if (name && name != "?") str += name + ": ";
-        str += toString(this.args[i], maxDepth, this);
+        str += maxDepth > -3 ? toString(this.args[i], maxDepth - 1, this) : "?";
       }
       str += ")";
       if (!this.retval.isEmpty())
-        str += " -> " + toString(this.retval, maxDepth, this);
+        str += " -> " + (maxDepth > -3 ? toString(this.retval, maxDepth - 1, this) : "?");
       return str;
     },
     getProp: function(prop) {
@@ -674,7 +675,8 @@
   Arr.prototype = extend(Obj.prototype, {
     constructor: Arr,
     toString: function(maxDepth) {
-      return "[" + toString(this.getProp("<i>"), maxDepth, this) + "]";
+      if (maxDepth == null) maxDepth = 0;
+      return "[" + (maxDepth > -3 ? toString(this.getProp("<i>"), maxDepth - 1, this) : "?") + "]";
     }
   });