Remove isWriteHandle() API

Summary: Based on our discussion, this API would be confusing if a reference of ReadHandle is obtained from a WriteHandle. We also don't want to make it virtual because this will increase `sizeof(ReadHandle)` / `sizeof(WriteHandle)` by 8 bytes.

Reviewed By: therealgymmy

Differential Revision: D43667308

fbshipit-source-id: a77a17113f1a23f84332ebfa7ea6772d7647339c

Author: Jiayue Bao

cachelib/allocator/Handle.h

@@ -242,8 +242,6 @@ struct ReadHandleImpl {
     return hdl;
   }
 
-  bool isWriteHandle() const { return false; }
-
  protected:
   // accessor. Calling getInternal() on handle with isReady() == false blocks
   // the thread until the handle is ready.
@@ -571,8 +569,6 @@ struct WriteHandleImpl : public ReadHandleImpl<T> {
   //        creating this item handle.
   WriteHandleImpl clone() const { return WriteHandleImpl{ReadHandle::clone()}; }
 
-  bool isWriteHandle() const { return true; }
-
   // Friends
   friend ReadHandle;
   // Only CacheAllocator and NvmCache can create non-default constructed handles

cachelib/allocator/tests/BaseAllocatorTest.h

@@ -713,35 +713,29 @@ class BaseAllocatorTest : public AllocatorTest<AllocatorT> {
       auto handle = alloc.find("key");
       ASSERT_NE(handle, nullptr);
       ASSERT_TRUE(isConst(handle->getMemory()));
-      ASSERT_EQ(handle.isWriteHandle(), false);
 
       // read handle clone
       auto handle2 = handle.clone();
       ASSERT_TRUE(isConst(handle2->getMemory()));
-      ASSERT_EQ(handle2.isWriteHandle(), false);
 
       // upgrade a read handle to a write handle
       auto handle3 = std::move(handle).toWriteHandle();
       ASSERT_FALSE(isConst(handle3->getMemory()));
-      ASSERT_EQ(handle3.isWriteHandle(), true);
     }
 
     {
       auto handle = alloc.findToWrite("key");
       ASSERT_NE(handle, nullptr);
       ASSERT_FALSE(isConst(handle->getMemory()));
-      ASSERT_EQ(handle.isWriteHandle(), true);
 
       // write handle clone
       auto handle2 = handle.clone();
       ASSERT_FALSE(isConst(handle2->getMemory()));
-      ASSERT_EQ(handle2.isWriteHandle(), true);
 
       // downgrade a write handle to a read handle
       ReadHandle handle3 = handle.clone();
       ASSERT_NE(handle3, nullptr);
       ASSERT_TRUE(isConst(handle3->getMemory()));
-      ASSERT_EQ(handle3.isWriteHandle(), false);
     }
 
     {
@@ -752,7 +746,7 @@ class BaseAllocatorTest : public AllocatorTest<AllocatorT> {
       // This is like doing a "clone" and setting it into wait context
       waitContext->set(alloc.find("key"));
       auto handle2 = std::move(handle).toWriteHandle();
-      ASSERT_EQ(handle2.isWriteHandle(), true);
+      ASSERT_FALSE(isConst(handle2->getMemory()));
     }
   }