[GR-2738] Add several assertions.

com.oracle.truffle.r.nodes/src/com/oracle/truffle/r/nodes/function/ArgumentMatcher.java

@@ -281,6 +281,7 @@ public class ArgumentMatcher {
     }
 
     private static String getErrorForArgument(RNode[] suppliedArgs, ArgumentsSignature suppliedSignature, int index) {
+        CompilerAsserts.neverPartOfCompilation();
         RNode node = suppliedArgs[index];
         if (node instanceof VarArgNode) {
             CompilerAsserts.neverPartOfCompilation();

com.oracle.truffle.r.nodes/src/com/oracle/truffle/r/nodes/function/RMissingHelper.java

@@ -22,6 +22,7 @@
  */
 package com.oracle.truffle.r.nodes.function;
 
+import com.oracle.truffle.api.CompilerAsserts;
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.frame.Frame;
 import com.oracle.truffle.api.frame.FrameSlot;
@@ -84,6 +85,7 @@ public class RMissingHelper {
      *         type is not object.
      */
     public static Object getMissingValue(Frame frame, String name) {
+        CompilerAsserts.neverPartOfCompilation();
         // Check binding
         FrameSlot frameSlot = frame.getFrameDescriptor().findFrameSlot(name);
         if (frameSlot == null) {

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/env/frame/REnvTruffleFrameAccess.java

@@ -66,6 +66,7 @@ public final class REnvTruffleFrameAccess extends REnvFrameAccess {
 
     @Override
     public Object get(String key) {
+        CompilerAsserts.neverPartOfCompilation();
         FrameDescriptor fd = frame.getFrameDescriptor();
         FrameSlot slot = fd.findFrameSlot(key);
         if (slot == null) {