Ensuring the content of CharSXP is always interned.

Author: Palez

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

@@ -50,7 +50,7 @@ public final class RSymbol extends RAttributeStorage {
     private CharSXPWrapper nameWrapper;
 
     private RSymbol(String name) {
-        this.nameWrapper = CharSXPWrapper.create(name);
+        this.nameWrapper = CharSXPWrapper.createInterned(name);
     }
 
     @TruffleBoundary

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/nodes/RSyntaxLookup.java

@@ -82,6 +82,7 @@ default boolean isPromiseLookup() {
      * section.
      */
     static RSyntaxLookup createDummyLookup(SourceSection source, String identifier, boolean isFunctionLookup) {
+        assert Utils.isInterned(identifier);
         return new RSyntaxLookup() {
             @Override
             public SourceSection getLazySourceSection() {