Migrated attachment for Guice issue 83, comment 6

GenericProviderMethods.patch

Index: com/google/inject/ProviderMethods.java
===================================================================
--- com/google/inject/ProviderMethods.java	(revision 332)
+++ com/google/inject/ProviderMethods.java	(working copy)
@@ -112,7 +112,29 @@
       };
 
       // TODO: Fix type warnings.
-      Class type = method.getReturnType();
+      TypeLiteral literalType = null;
+
+      Type genericType = method.getGenericReturnType();
+      if (genericType != null) {
+          Type[] params = method.getDeclaringClass().getTypeParameters();
+          for (int i = 0; i < params.length; i++)
+          {
+              if ( genericType.equals( params[i] ))
+              {
+                  Type superclass = providers.getClass().getGenericSuperclass();
+                  Type actualType = ((java.lang.reflect.ParameterizedType) superclass).getActualTypeArguments()[i];
+                  literalType = TypeLiteral.get( actualType );
+                  break;
+              }
+          }
+      }
+
+      if ( null == literalType ) {
+          literalType = TypeLiteral.get(method.getReturnType());
+      }
+
+      TypeLiteral<Object> type = literalType;
+
       if (scopeAnnotation == null && bindingAnnotation == null) {
         bind(type).toProvider(provider);
       } else if (scopeAnnotation == null) {