allow EnC on ordinary Task-returning methods.

Author: VSadov

src/coreclr/vm/encee.cpp

@@ -344,13 +344,6 @@ HRESULT EditAndContinueModule::UpdateMethod(MethodDesc *pMethod)
     }
     CONTRACTL_END;
 
-    if (pMethod->HasAsyncMethodData())
-    {
-        // TODO: (async) revisit and examine if this can be supported
-        LOG((LF_ENC, LL_INFO100, "**Error** EnC for Async methods is NYI"));
-        return E_FAIL;
-    }
-
     // Notify the debugger of the update
     if (CORDebuggerAttached())
     {

src/coreclr/vm/method.cpp

@@ -3235,6 +3235,19 @@ void MethodDesc::ResetCodeEntryPointForEnC()
             ppCode, pCode));
         *ppCode = (PCODE)NULL;
     }
+
+    // update of a Task-returning method effectively updates both variants,
+    // so reset the entry for the other variant as well.
+    if (IsTaskReturningMethod())
+    {
+        // TODO: (async) revisit and examine if the following is sufficient for actual runtime async methods when EnC is supported.
+        //       for now we only expect to see ordinary Task-returning methods here (not thunks).
+        _ASSERTE(!IsAsyncThunkMethod());
+
+        MethodDesc *otherVariant =  GetAsyncOtherVariantNoCreate();
+        _ASSERTE(otherVariant != NULL);
+        otherVariant->ResetCodeEntryPointForEnC();
+    }
 }
 
 

src/coreclr/vm/method.hpp

@@ -1657,6 +1657,13 @@ class MethodDesc
         return FindOrCreateAssociatedMethodDesc(this, GetMethodTable(), FALSE, GetMethodInstantiation(), allowInstParam, FALSE, TRUE, AsyncVariantLookup::AsyncOtherVariant);
     }
 
+    // same as above, but with allowCreate = FALSE
+    // for rare cases where we cannot allow GC, but we know that the other varaint is already created.
+    MethodDesc* GetAsyncOtherVariantNoCreate(BOOL allowInstParam = TRUE)
+    {
+        return FindOrCreateAssociatedMethodDesc(this, GetMethodTable(), FALSE, GetMethodInstantiation(), allowInstParam, FALSE, FALSE, AsyncVariantLookup::AsyncOtherVariant);
+    }
+
     // True if a MD is an funny BoxedEntryPointStub (not from the method table) or
     // an MD for a generic instantiation...In other words the MethodDescs and the
     // MethodTable are guaranteed to be "tightly-knit", i.e. if one is present in