[ruby/irb] Remove keyword exception from Context#evaluate because

the value is always nil
(ruby/irb#617)

ruby/irb@62691384f8

lib/irb.rb

@@ -506,8 +506,6 @@ def run(conf = IRB.conf)
 
     # Evaluates input for this session.
     def eval_input
-      exc = nil
-
       @scanner.set_prompt do
         |ltype, indent, continue, line_no|
         if ltype
@@ -567,18 +565,18 @@ def eval_input
             is_assignment = assignment_expression?(line)
             if IRB.conf[:MEASURE] && !IRB.conf[:MEASURE_CALLBACKS].empty?
               result = nil
-              last_proc = proc{ result = evaluate_line(line, line_no, exception: exc) }
+              last_proc = proc{ result = evaluate_line(line, line_no) }
               IRB.conf[:MEASURE_CALLBACKS].inject(last_proc) { |chain, item|
                 _name, callback, arg = item
                 proc {
-                  callback.(@context, line, line_no, arg, exception: exc) do
+                  callback.(@context, line, line_no, arg) do
                     chain.call
                   end
                 }
               }.call
               @context.set_last_value(result)
             else
-              evaluate_line(line, line_no, exception: exc)
+              evaluate_line(line, line_no)
             end
             if @context.echo?
               if is_assignment
@@ -589,22 +587,17 @@ def eval_input
                 output_value
               end
             end
-          rescue Interrupt => exc
           rescue SystemExit, SignalException
             raise
-          rescue Exception => exc
-          else
-            exc = nil
-            next
+          rescue Interrupt, Exception => exc
+            handle_exception(exc)
+            @context.workspace.local_variable_set(:_, exc)
           end
-          handle_exception(exc)
-          @context.workspace.local_variable_set(:_, exc)
-          exc = nil
         end
       end
     end
 
-    def evaluate_line(line, line_no, exception: nil)
+    def evaluate_line(line, line_no)
       # Transform a non-identifier alias (@, $) or keywords (next, break)
       command, args = line.split(/\s/, 2)
       if original = @context.command_aliases[command.to_sym]
@@ -618,7 +611,7 @@ def evaluate_line(line, line_no, exception: nil)
         line = "#{command} #{command_class.transform_args(args)}"
       end
 
-      @context.evaluate(line, line_no, exception: exception)
+      @context.evaluate(line, line_no)
     end
 
     def convert_invalid_byte_sequence(str, enc)

lib/irb/context.rb

@@ -473,15 +473,8 @@ def inspect_mode=(opt)
       @inspect_mode
     end
 
-    def evaluate(line, line_no, exception: nil) # :nodoc:
+    def evaluate(line, line_no) # :nodoc:
       @line_no = line_no
-
-      if exception
-        line_no -= 1
-        line = "begin ::Kernel.raise _; rescue _.class\n#{line}\n""end"
-        @workspace.local_variable_set(:_, exception)
-      end
-
       set_last_value(@workspace.evaluate(line, irb_path, line_no))
     end
 

test/irb/test_context.rb

@@ -37,20 +37,6 @@ def test_last_value
       assert_same(obj, @context.evaluate('_', 1))
     end
 
-    def test_evaluate_with_exception
-      assert_nil(@context.evaluate("$!", 1))
-      e = assert_raise_with_message(RuntimeError, 'foo') {
-        @context.evaluate("raise 'foo'", 1)
-      }
-      assert_equal('foo', e.message)
-      assert_same(e, @context.evaluate('$!', 1, exception: e))
-      e = assert_raise(SyntaxError) {
-        @context.evaluate("1,2,3", 1, exception: e)
-      }
-      assert_match(/\A\(irb\):1:/, e.message)
-      assert_not_match(/rescue _\.class/, e.message)
-    end
-
     def test_evaluate_with_encoding_error_without_lineno
       assert_raise_with_message(EncodingError, /invalid symbol/) {
         @context.evaluate(%q[:"\xAE"], 1)