update DefBootstrap to handle Error from ClassValue

Author: jdconrad

modules/lang-painless/src/main/java/org/elasticsearch/painless/DefBootstrap.java

@@ -201,6 +201,13 @@ protected MethodHandle computeValue(Class<?> receiverType) {
                     try {
                         return lookup(flavor, name, receiverType).asType(type);
                     } catch (Throwable t) {
+                        // ClassValue.getFromHashMap wraps checked exceptions as Error, but
+                        // we do not want to crash here because we could not process the type
+                        // correctly as part of a script, so we instead unwrap the Error and
+                        // rethrow the original exception
+                        if (t instanceof Error && ((Error) t).getCause() instanceof Exception) {
+                            t = (Exception) ((Error) t).getCause();
+                        }
                         Def.rethrow(t);
                         throw new AssertionError();
                     }