Implement Parser#arg1 for C_LABEL, C_GOTO, C_IF

Author: leocassarani

lib/parser.rb

@@ -37,10 +37,10 @@ def command_type
 
   def arg1
     case command_type
-    when C_PUSH, C_POP
-      current.split[1]
-    else
+    when C_ARITHMETIC
       current
+    else
+      current.split[1]
     end
   end
 

spec/unit/parser_spec.rb

@@ -211,23 +211,23 @@
     context 'when the current command is a label' do
       let(:input) { 'label LOOP_START' }
 
-      it 'returns the first argument', :pending do
+      it 'returns the first argument' do
         expect(parser.arg1).to eq 'LOOP_START'
       end
     end
 
     context 'when the current command is a goto' do
       let(:input) { 'goto WHILE' }
 
-      it 'returns the first argument', :pending do
+      it 'returns the first argument' do
         expect(parser.arg1).to eq 'WHILE'
       end
     end
 
     context 'when the current command is an if-goto' do
       let(:input) { 'if-goto COMPUTE_ELEMENT' }
 
-      it 'returns the first argument', :pending do
+      it 'returns the first argument' do
         expect(parser.arg1).to eq 'COMPUTE_ELEMENT'
       end
     end