[Truffle] - String#capitalize! raises a RuntimeError when self is frozen

Author: lucasallan

spec/truffle/tags/core/string/capitalize_tags.txt

@@ -1,5 +1,4 @@
 fails:String#capitalize taints resulting string when self is tainted
 fails:String#capitalize is locale insensitive (only upcases a-z and only downcases A-Z)
 fails:String#capitalize returns subclass instances when called on a subclass
-fails:String#capitalize! returns nil when no changes are made
-fails:String#capitalize! raises a RuntimeError when self is frozen
+fails:String#capitalize! returns nil when no changes are made

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

@@ -1926,6 +1926,8 @@ public RubyString capitalizeBang(RubyString string) {
             String javaString = string.toString();
             if (javaString.isEmpty()) {
                 return string;
+            } else if (string.isFrozen()) {
+                throw new RaiseException(getContext().getCoreLibrary().runtimeError("can't modify frozen string", this));
             } else {
                 final ByteList byteListString = StringNodesHelper.capitalize(string);