Fix bugs relating to . and this.

First, I missed some reference checks when I stopped interning names. Fixed
those.

Second, when iterating over an array which contained null elements, the wrong
thing was happening.

src/main/java/com/samskivert/mustache/BasicCollector.java

@@ -35,9 +35,6 @@ public abstract class BasicCollector implements Mustache.Collector
     }
 
     public Mustache.VariableFetcher createFetcher (Object ctx, String name) {
-        // support both .name and this.name to fetch members
-        if (name == Template.DOT_NAME || name == Template.THIS_NAME) return THIS_FETCHER;
-
         if (ctx instanceof Map<?,?>) return MAP_FETCHER;
 
         // if the name looks like a number, potentially use one of our 'indexing' fetchers
@@ -73,7 +70,7 @@ public abstract class BasicCollector implements Mustache.Collector
             Map<?,?> map = (Map<?,?>)ctx;
             if (map.containsKey(name)) return map.get(name);
             // special case to allow map entry set to be iterated over
-            if (name == "entrySet") return map.entrySet();
+            if ("entrySet".equals(name)) return map.entrySet();
             return Template.NO_FETCHER_FOUND;
         }
         @Override public String toString () {
@@ -113,15 +110,6 @@ public abstract class BasicCollector implements Mustache.Collector
         }
     };
 
-    protected static final Mustache.VariableFetcher THIS_FETCHER = new Mustache.VariableFetcher() {
-        public Object get (Object ctx, String name) throws Exception {
-            return ctx;
-        }
-        @Override public String toString () {
-            return "THIS_FETCHER";
-        }
-    };
-
     protected static abstract class ArrayHelper implements Mustache.VariableFetcher {
         public Object get (Object ctx, String name) throws Exception {
             try {

src/main/java/com/samskivert/mustache/Mustache.java

@@ -856,8 +856,10 @@ public class Mustache {
         @Override public void execute (Template tmpl, Template.Context ctx, Writer out) {
             Object value = tmpl.getValueOrDefault(ctx, _name, _line);
             if (value == null) {
-                throw new MustacheException.Context("No key, method or field with name '" + _name +
+                String msg = Template.isThisName(_name) ?
-                                                    "' on line " + _line, _name, _line);
+                    "Resolved '.' to null (which is disallowed), on line " + _line :
+                    "No key, method or field with name '" + _name + "' on line " + _line;
+                throw new MustacheException.Context(msg, _name, _line);
             }
             write(out, _escaper.escape(_formatter.format(value)));
         }

src/main/java/com/samskivert/mustache/Template.java

@@ -240,7 +240,7 @@ public class Template {
         // if we reach here, we found nothing in this or our parent contexts...
 
         // if we have a compound key, decompose the value and resolve it step by step
-        if (name != DOT_NAME && name.indexOf(DOT_NAME) != -1) {
+        if (!name.equals(DOT_NAME) && name.indexOf(DOT_NAME) != -1) {
             return getCompoundValue(ctx, name, line, missingIsNull);
         } else {
             // otherwise let checkForMissing() decide what to do
@@ -297,6 +297,11 @@ public class Template {
     }
 
     protected Object getValueIn (Object data, String name, int line) {
+        // if we're getting `.` or `this` then just return the whole context; we do this before the
+        // null check because it may be valid for the context to be null (if we're iterating over a
+        // list which contains nulls, for example)
+        if (isThisName(name)) return data;
+
         if (data == null) {
             throw new NullPointerException(
                 "Null context for variable '" + name + "' on line " + line);
@@ -412,6 +417,10 @@ public class Template {
         }
     }
 
+    protected static boolean isThisName (String name) {
+        return DOT_NAME.equals(name) || THIS_NAME.equals(name);
+    }
+
     protected static final String DOT_NAME = ".";
     protected static final String THIS_NAME = "this";
     protected static final String FIRST_NAME = "-first";

src/test/java/com/samskivert/mustache/SharedTests.java

@@ -321,6 +321,12 @@ public abstract class SharedTests extends GWTTestCase
               execute(context("things", Arrays.asList("bar", "baz", "bif"))));
     }
 
+    @Test public void testNestedNullThis () {
+        check("bar!bif", Mustache.compiler().defaultValue("!").
+              compile("{{#things}}{{.}}{{/things}}").
+              execute(context("things", Arrays.asList("bar", null, "bif"))));
+    }
+
     @Test public void testNewlineSkipping () {
         testNewlineSkipping("\n");
     }