Helperize and slightly improve output of arg nodes

lib/opal/nodes/args/extract_kwargs.rb

@@ -20,7 +20,9 @@ class ExtractKwargs < Base
         def compile
           add_temp '$kwargs'
 
-          line '$kwargs = Opal.extract_kwargs($post_args)'
+          helper :extract_kwargs
+
+          push '$kwargs = $extract_kwargs($post_args)'
         end
       end
     end

lib/opal/nodes/args/extract_kwoptarg.rb

@@ -25,7 +25,7 @@ def compile
 
           return if default_value.children[1] == :undefined
 
-          line "if (#{lvar_name} == null) #{lvar_name} = ", expr(default_value)
+          push "if (#{lvar_name} == null) #{lvar_name} = ", expr(default_value)
         end
       end
     end

lib/opal/nodes/args/extract_kwrestarg.rb

@@ -21,7 +21,10 @@ def compile
           name = self.name || '$kw_rest_arg'
 
           add_temp name
-          line "#{name} = Opal.kwrestargs($kwargs, #{used_kwargs});"
+
+          helper :kwrestargs
+
+          push "#{name} = $kwrestargs($kwargs, #{used_kwargs})"
         end
 
         def used_kwargs

lib/opal/nodes/args/extract_optarg.rb

@@ -25,7 +25,7 @@ class ExtractOptargNode < Base
         def compile
           return if default_value.children[1] == :undefined
 
-          line "if (#{name} == null) #{name} = ", expr(default_value), ";"
+          push "if (#{name} == null) #{name} = ", expr(default_value)
         end
       end
     end

lib/opal/nodes/args/extract_post_arg.rb

@@ -17,7 +17,7 @@ def compile
 
           line "#{name} = $post_args.shift();"
 
-          line "if (#{name} == null) #{name} = nil;"
+          push "if (#{name} == null) #{name} = nil"
         end
       end
     end

lib/opal/nodes/args/extract_post_optarg.rb

@@ -28,7 +28,7 @@ def compile
 
           return if default_value.children[1] == :undefined
 
-          line "if (#{name} == null) #{name} = ", expr(default_value), ";"
+          push "if (#{name} == null) #{name} = ", expr(default_value)
         end
       end
     end

lib/opal/nodes/args/extract_restarg.rb

@@ -27,9 +27,9 @@ def compile
 
           if args_to_keep == 0
             # no post-args, we are free to grab everything
-            line "#{name} = $post_args;"
+            push "#{name} = $post_args"
           else
-            line "#{name} = $post_args.splice(0, $post_args.length - #{args_to_keep});"
+            push "#{name} = $post_args.splice(0, $post_args.length - #{args_to_keep})"
           end
         end
       end

lib/opal/nodes/args/initialize_iterarg.rb

@@ -18,7 +18,7 @@ class InitializeIterarg < Base
         children :name
 
         def compile
-          line "if (#{name} == null) #{name} = nil;"
+          push "if (#{name} == null) #{name} = nil"
         end
       end
     end

lib/opal/nodes/args/initialize_shadowarg.rb

@@ -16,7 +16,7 @@ class InitializeShadowarg < Base
         def compile
           scope.locals << name
           scope.add_arg(name)
-          line "#{name} = nil;"
+          push "#{name} = nil"
         end
       end
     end

lib/opal/nodes/args/prepare_post_args.rb

@@ -14,10 +14,12 @@ class PreparePostArgs < Base
         def compile
           add_temp '$post_args'
 
+          helper :slice
+
           if offset == 0
-            line "$post_args = Opal.slice.call(arguments)"
+            push "$post_args = $slice.call(arguments)"
           else
-            line "$post_args = Opal.slice.call(arguments, #{offset})"
+            push "$post_args = $slice.call(arguments, #{offset})"
           end
         end
       end