An error while running Performance/RedundantMerge cop

[eyusupov]

When running RuboCop on the sample code attached below, Performance/RedundantMerge cop is failing.

Expected behavior

RuboCop checks the code correctly.

Actual behavior

The following error is shown (when running with -d option):

An error occurred while Performance/RedundantMerge cop was inspecting /home/eyusupov/toptal/toptal/1.rb.
undefined method `name' for #<Parser::Source::Map::Send:0x005605c56b9bc8>
/home/eyusupov/sources/rubocop/lib/rubocop/cop/performance/redundant_merge.rb:31:in `block in on_send'
/home/eyusupov/sources/rubocop/lib/rubocop/cop/performance/redundant_merge.rb:19:in `redundant_merge'
/home/eyusupov/sources/rubocop/lib/rubocop/cop/performance/redundant_merge.rb:25:in `on_send'
/home/eyusupov/sources/rubocop/lib/rubocop/cop/commissioner.rb:42:in `block (2 levels) in on_send'

Steps to reproduce the problem

Create a Ruby file with the following code:

t.each_with_object({}) { |_, r| r[:a].merge!(a: '') }

Run RuboCop on this file.

RuboCop version

$ ./bin/rubocop -V
0.39.0 (using Parser 2.3.0.7, running on ruby 2.2.4 x86_64-linux)