# File vendor/rails/activesupport/lib/active_support/rescuable.rb, line 78
 78:     def handler_for_rescue(exception)
 79:       # We go from right to left because pairs are pushed onto rescue_handlers
 80:       # as rescue_from declarations are found.
 81:       _, rescuer = Array(rescue_handlers).reverse.detect do |klass_name, handler|
 82:         # The purpose of allowing strings in rescue_from is to support the
 83:         # declaration of handler associations for exception classes whose
 84:         # definition is yet unknown.
 85:         #
 86:         # Since this loop needs the constants it would be inconsistent to
 87:         # assume they should exist at this point. An early raised exception
 88:         # could trigger some other handler and the array could include
 89:         # precisely a string whose corresponding constant has not yet been
 90:         # seen. This is why we are tolerant to unknown constants.
 91:         #
 92:         # Note that this tolerance only matters if the exception was given as
 93:         # a string, otherwise a NameError will be raised by the interpreter
 94:         # itself when rescue_from CONSTANT is executed.
 95:         klass = self.class.const_get(klass_name) rescue nil
 96:         klass ||= klass_name.constantize rescue nil
 97:         exception.is_a?(klass) if klass
 98:       end
 99: 
100:       case rescuer
101:       when Symbol
102:         method(rescuer)
103:       when Proc
104:         rescuer.bind(self)
105:       end
106:     end

    # File vendor/rails/activesupport/lib/active_support/rescuable.rb, line 71
71:     def rescue_with_handler(exception)
72:       if handler = handler_for_rescue(exception)
73:         handler.arity != 0 ? handler.call(exception) : handler.call
74:         true # don't rely on the return value of the handler
75:       end
76:     end