Fix: as.pairlist for pairlist returns copy of the argument

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

@@ -66,6 +66,7 @@ import com.oracle.truffle.r.runtime.builtins.RBuiltin;
 import com.oracle.truffle.r.runtime.data.RDataFactory;
 import com.oracle.truffle.r.runtime.data.RLanguage;
 import com.oracle.truffle.r.runtime.data.RNull;
+import com.oracle.truffle.r.runtime.data.RPairList;
 import com.oracle.truffle.r.runtime.data.RSharingAttributeStorage;
 import com.oracle.truffle.r.runtime.data.RStringVector;
 import com.oracle.truffle.r.runtime.data.RSymbol;
@@ -260,6 +261,12 @@ public abstract class AsVector extends RBuiltinNode.Arg2 {
                 return RNull.instance;
             }
 
+            @Specialization
+            @TruffleBoundary
+            protected Object doPairList(RPairList list) {
+                return list.copy();
+            }
+
             @Fallback
             protected Object castPairlist(Object x) {
                 throw RInternalError.unimplemented("non-list casts to pairlist for " + x.getClass().getSimpleName());

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/data/RPairList.java

@@ -31,6 +31,7 @@ import com.oracle.truffle.r.runtime.RInternalError;
 import com.oracle.truffle.r.runtime.RRuntime;
 import com.oracle.truffle.r.runtime.RType;
 import com.oracle.truffle.r.runtime.Utils;
+import com.oracle.truffle.r.runtime.data.RDataFactory.BaseVectorFactory;
 import com.oracle.truffle.r.runtime.data.model.RAbstractContainer;
 import com.oracle.truffle.r.runtime.data.model.RAbstractVector;
 import com.oracle.truffle.r.runtime.data.nodes.FastPathVectorAccess.FastPathFromListAccess;
@@ -270,16 +271,22 @@ public final class RPairList extends RSharingAttributeStorage implements RAbstra
     }
 
     @Override
-    public RSharingAttributeStorage copy() {
-        RPairList result = new RPairList();
+    public RPairList copy() {
+        BaseVectorFactory dataFactory = RDataFactory.getInstance();
+        RPairList curr = dataFactory.createPairList();
+        RPairList result = curr;
         Object original = this;
-        while (!isNull(original)) {
+        while (true) {
             RPairList origList = (RPairList) original;
-            result.car = origList.car;
-            result.tag = origList.tag;
-            result.cdr = new RPairList();
-            result = (RPairList) result.cdr;
+            curr.car = origList.car;
+            curr.tag = origList.tag;
             original = origList.cdr;
+            if (isNull(original)) {
+                curr.cdr = RNull.instance;
+                break;
+            }
+            curr.cdr = dataFactory.createPairList();
+            curr = (RPairList) curr.cdr;
         }
         if (getAttributes() != null) {
             result.initAttributes(RAttributesLayout.copy(getAttributes()));

com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/builtins/TestBuiltin_asvector.java

@@ -444,6 +444,7 @@ public class TestBuiltin_asvector extends TestBase {
 
         assertEval("as.vector(NULL, mode='pairlist')");
         assertEval("{ as.vector.cls <- function(x, mode) 42; as.vector(structure(c(1,2), class='cls')); }");
+        assertEval("as.pairlist(as.pairlist(c(1,2,3)))");
     }
 
     @Test

com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/runtime/data/RPairListTests.java

@@ -24,6 +24,7 @@ package com.oracle.truffle.r.test.runtime.data;
 
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
 
 import java.util.Iterator;
 
@@ -33,6 +34,7 @@ import com.oracle.truffle.r.runtime.data.RDataFactory;
 import com.oracle.truffle.r.runtime.data.RList;
 import com.oracle.truffle.r.runtime.data.RNull;
 import com.oracle.truffle.r.runtime.data.RPairList;
+import com.oracle.truffle.r.runtime.data.RSharingAttributeStorage;
 
 public class RPairListTests {
     @Test
@@ -52,4 +54,16 @@ public class RPairListTests {
         assertArrayEquals(new String[]{"name1", "name2"}, result.getNames().getReadonlyData());
         assertArrayEquals(new Object[]{1, 2}, result.getDataWithoutCopying());
     }
+
+    @Test
+    public void testCopy() {
+        RPairList pairList = RDataFactory.createPairList(1, RDataFactory.createPairList(2, RNull.instance, "name2"), "name1");
+        RPairList copy = pairList.copy();
+        assertEquals(2, copy.getLength());
+        assertEquals("name1", copy.getTag());
+        assertEquals(1, copy.car());
+        assertEquals("name2", ((RPairList) copy.cdr()).getTag());
+        assertEquals(2, ((RPairList) copy.cdr()).car());
+        assertSame(RNull.instance, ((RPairList) copy.cdr()).cdr());
+    }
 }