[Truffle] - Implements String#chr

Author: lucasallan

core/src/main/java/org/jruby/truffle/nodes/core/StringNodes.java

@@ -1249,7 +1249,6 @@ public RubyString capitalize(RubyString string) {
 
     }
 
-
     @CoreMethod(names = "clear")
     public abstract static class ClearNode extends CoreMethodNode {
 
@@ -1272,4 +1271,30 @@ public RubyString clear(RubyString string) {
         }
     }
 
+    @CoreMethod(names = "chr")
+    public abstract static class ChrNode extends CoreMethodNode {
+
+        public ChrNode(RubyContext context, SourceSection sourceSection) {
+            super(context, sourceSection);
+        }
+
+        public ChrNode(ChrNode prev) {
+            super(prev);
+        }
+
+        @Specialization
+        public RubyString chr(RubyString string) {
+            notDesignedForCompilation();
+            if (string.toString().isEmpty()) {
+                return string;
+            } else {
+                String head = string.toString().substring(0, 1);
+                ByteList byteString = ByteList.create(head);
+                byteString.setEncoding(string.getBytes().getEncoding());
+
+                return string.getContext().makeString(byteString);
+            }
+        }
+    }
+
 }