Fix S3 dispatches according to the first non-missing argument

com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/S3DispatchFunctions.java

@@ -48,6 +48,7 @@ import com.oracle.truffle.r.runtime.ReturnException;
 import com.oracle.truffle.r.runtime.Utils;
 import com.oracle.truffle.r.runtime.data.RArgsValuesAndNames;
 import com.oracle.truffle.r.runtime.data.RAttributeProfiles;
+import com.oracle.truffle.r.runtime.data.RDataFactory;
 import com.oracle.truffle.r.runtime.data.RMissing;
 import com.oracle.truffle.r.runtime.data.RNull;
 import com.oracle.truffle.r.runtime.data.RPromise;
@@ -98,6 +99,7 @@ public abstract class S3DispatchFunctions extends RBuiltinNode {
         @Child private PromiseCheckHelperNode promiseCheckHelper;
 
         private final BranchProfile errorProfile = BranchProfile.create();
+        private final BranchProfile firstArgMissing = BranchProfile.create();
         private final ConditionProfile argMissingProfile = ConditionProfile.createBinaryProfile();
         private final ConditionProfile argsValueAndNamesProfile = ConditionProfile.createBinaryProfile();
 
@@ -107,7 +109,6 @@ public abstract class S3DispatchFunctions extends RBuiltinNode {
 
         @Specialization
         protected Object execute(VirtualFrame frame, String generic, Object arg) {
-
             Object dispatchedObject;
             if (argMissingProfile.profile(arg == RMissing.instance)) {
                 // For S3Dispatch, we have to evaluate the the first argument
@@ -116,7 +117,7 @@ public abstract class S3DispatchFunctions extends RBuiltinNode {
                 dispatchedObject = arg;
             }
 
-            RStringVector type = classHierarchyNode.execute(dispatchedObject);
+            RStringVector type = dispatchedObject == null ? RDataFactory.createEmptyStringVector() : classHierarchyNode.execute(dispatchedObject);
             MaterializedFrame callerFrame = getCallerFrame(frame);
             MaterializedFrame genericDefFrame = RArguments.getEnclosingFrame(frame);
 
@@ -128,7 +129,8 @@ public abstract class S3DispatchFunctions extends RBuiltinNode {
 
         /**
          * Get the first (logical) argument in the frame, and handle {@link RPromise}s and
-         * {@link RArgsValuesAndNames}.
+         * {@link RArgsValuesAndNames}. If there is no actual argument, returns null. If there are
+         * no formal arguments, throws the appropriate error.
          */
         private Object getEnclosingArg(VirtualFrame frame, String generic) {
             if (RArguments.getArgumentsLength(frame) == 0 || RArguments.getArgument(frame, 0) == null) {
@@ -137,20 +139,37 @@ public abstract class S3DispatchFunctions extends RBuiltinNode {
             }
             Object enclosingArg = RArguments.getArgument(frame, 0);
             if (argsValueAndNamesProfile.profile(enclosingArg instanceof RArgsValuesAndNames)) {
-                // The GnuR "1. argument" might be hidden inside a "..."! Unwrap for proper dispatch
-                RArgsValuesAndNames varArgs = (RArgsValuesAndNames) enclosingArg;
-                if (varArgs.isEmpty()) {
-                    errorProfile.enter();
-                    throw RError.error(this, RError.Message.UNKNOWN_FUNCTION_USE_METHOD, generic, RRuntime.toString(RNull.instance));
+                enclosingArg = getFirstVarArg((RArgsValuesAndNames) enclosingArg);
+            } else if (enclosingArg == RMissing.instance) {
+                firstArgMissing.enter();
+                enclosingArg = getFirstNonMissingArg(frame, 1);
+                if (enclosingArg == null) {
+                    return null;
                 }
-                enclosingArg = varArgs.getArgument(0);
             }
+
             if (promiseCheckHelper == null) {
                 CompilerDirectives.transferToInterpreterAndInvalidate();
                 promiseCheckHelper = insert(new PromiseCheckHelperNode());
             }
             return promiseCheckHelper.checkEvaluate(frame, enclosingArg);
         }
+
+        private Object getFirstNonMissingArg(VirtualFrame frame, int startIdx) {
+            for (int i = startIdx; i < RArguments.getArgumentsLength(frame); i++) {
+                Object arg = RArguments.getArgument(frame, i);
+                if (arg instanceof RArgsValuesAndNames) {
+                    return getFirstVarArg((RArgsValuesAndNames) arg);
+                } else if (arg != RMissing.instance) {
+                    return arg;
+                }
+            }
+            return null;
+        }
+
+        private Object getFirstVarArg(RArgsValuesAndNames varArgs) {
+            return varArgs.isEmpty() ? null : varArgs.getArgument(0);
+        }
     }
 
     @RBuiltin(name = "NextMethod", visibility = RVisibility.CUSTOM, kind = SUBSTITUTE, parameterNames = {"generic", "object", "..."})