Pass the context instance itself instead of its class.

In GWT we can't use Class.isAssignableFrom. We need the original instance so
that we can do (ctx instanceof Map<?,?>).

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

@@ -23,14 +23,14 @@ public class BasicCollector implements Mustache.Collector
     }
 
     @Override
-    public Mustache.VariableFetcher createFetcher (Class<?> cclass, String name)
+    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 (Map.class.isAssignableFrom(cclass)) {
+        if (ctx instanceof Map<?,?>) {
             return MAP_FETCHER;
         }
 

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

@@ -34,11 +34,12 @@ public class DefaultCollector extends BasicCollector
     }
 
     @Override
-    public Mustache.VariableFetcher createFetcher (Class<?> cclass, String name)
+    public Mustache.VariableFetcher createFetcher (Object ctx, String name)
     {
-        Mustache.VariableFetcher fetcher = super.createFetcher(cclass, name);
+        Mustache.VariableFetcher fetcher = super.createFetcher(ctx, name);
         if (fetcher != null) return fetcher;
 
+        Class<?> cclass = ctx.getClass();
         final Method m = getMethod(cclass, name);
         if (m != null) {
             return new Mustache.VariableFetcher() {

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

@@ -144,8 +144,10 @@ public class Mustache
          * not a collection. */
         Iterator<?> toIterator (final Object value);
 
-        /** Creates a fetcher for a so-named variable on instances of the given class. */
+        /** Creates a fetcher for a so-named variable in the supplied context object, which will
-        VariableFetcher createFetcher (Class<?> cclass, String name);
+         * never be null. The fetcher will be cached and reused for future contexts for which
+         * {@code octx.getClass().equals(nctx.getClass()}. */
+        VariableFetcher createFetcher (Object ctx, String name);
     }
 
     /**

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

@@ -186,10 +186,10 @@ public class Template
                 return fetcher.get(data, name);
             } catch (Exception e) {
                 // zoiks! non-monomorphic call site, update the cache and try again
-                fetcher = _compiler.collector.createFetcher(key.cclass, key.name);
+                fetcher = _compiler.collector.createFetcher(data, key.name);
             }
         } else {
-            fetcher = _compiler.collector.createFetcher(key.cclass, key.name);
+            fetcher = _compiler.collector.createFetcher(data, key.name);
         }
 
         // if we were unable to create a fetcher, just return null and our caller can either try