[ruby/irb] Allow assigning and using local variable name conflicting

with command
(https://github.com/ruby/irb/pull/961)

https://github.com/ruby/irb/commit/00603d470f

lib/irb.rb

@@ -1138,6 +1138,8 @@ module IRB
       end
     end
 
+    ASSIGN_OPERATORS_REGEXP = Regexp.union(%w[= += -= *= /= %= **= &= |= &&= ||= ^= <<= >>=])
+
     def parse_command(code)
       command_name, arg = code.strip.split(/\s+/, 2)
       return unless code.lines.size == 1 && command_name
@@ -1149,6 +1151,12 @@ module IRB
         return [alias_name, arg]
       end
 
+      # Assignment-like expression is not a command
+      return if arg.start_with?(ASSIGN_OPERATORS_REGEXP) && !arg.start_with?(/==|=~/)
+
+      # Local variable have precedence over command
+      return if @context.local_variables.include?(command)
+
       # Check visibility
       public_method = !!Kernel.instance_method(:public_method).bind_call(@context.main, command) rescue false
       private_method = !public_method && !!Kernel.instance_method(:method).bind_call(@context.main, command) rescue false

test/irb/command/test_custom_command.rb

@@ -145,5 +145,50 @@ module TestIRB
       assert_include(output, "No description provided.")
       assert_not_include(output, "Maybe IRB bug")
     end
+
+    def test_command_name_local_variable
+      write_ruby <<~RUBY
+        require "irb/command"
+
+        class FooBarCommand < IRB::Command::Base
+          category 'CommandTest'
+          description 'test'
+          def execute(arg)
+            puts "arg=\#{arg.inspect}"
+          end
+        end
+
+        IRB::Command.register(:foo_bar, FooBarCommand)
+
+        binding.irb
+      RUBY
+
+      output = run_ruby_file do
+        type "binding.irb"
+        type "foo_bar == 1 || 1"
+        type "foo_bar =~ /2/ || 2"
+        type "exit"
+        type "binding.irb"
+        type "foo_bar = '3'; foo_bar"
+        type "foo_bar == 4 || '4'"
+        type "foo_bar =~ /5/ || '5'"
+        type "exit"
+        type "binding.irb"
+        type "foo_bar ||= '6'; foo_bar"
+        type "foo_bar == 7 || '7'"
+        type "foo_bar =~ /8/ || '8'"
+        type "exit"
+        type "exit"
+      end
+
+      assert_include(output, 'arg="== 1 || 1"')
+      assert_include(output, 'arg="=~ /2/ || 2"')
+      assert_include(output, '=> "3"')
+      assert_include(output, '=> "4"')
+      assert_include(output, '=> "5"')
+      assert_include(output, '=> "6"')
+      assert_include(output, '=> "7"')
+      assert_include(output, '=> "8"')
+    end
   end
 end