Ignore lambdas whose target interfaces have multiple methods

This currently accounts for those with default methods, and those which re-declare as
abstract methods inherited from Object, such as equals(Object). In the future we should
distinguish and disregard these methods as candidates for the intended lambda method.

Author: smowton

jbmc/src/java_bytecode/lambda_synthesis.cpp

@@ -134,6 +134,19 @@ void create_invokedynamic_synthetic_classes(
                     << messaget::eom;
         continue;
       }
+      else if(implemented_interface_type.methods().size() != 1)
+      {
+        log.debug() << "ignoring invokedynamic at " << method_identifier
+                    << " address " << instruction.address
+                    << " which produces type "
+                    << implemented_interface_tag.get_identifier()
+                    << " which should have exactly one abstract method but "
+                    << " actually has "
+                    << implemented_interface_type.methods().size()
+                    << ". Note default methods are not supported yet."
+                    << messaget::eom;
+        continue;
+      }
 
       log.debug() << "identified invokedynamic at " << method_identifier
                   << " address " << instruction.address