mruby-data (mrb_data_initialize): update argument error conditions

- raise ArgumentError if arguments size differs from data size.
  Previously it accepted smaller argument size.

- the message is updated to "wrong number of arguments". It's not
  "struct" any longer.

mrbgems/mruby-data/src/data.c

@@ -145,31 +145,21 @@ make_data(mrb_state *mrb, mrb_value members, struct RClass *klass)
 
 /*
  *  call-seq:
- *     StructClass.new(arg, ...)             -> obj
- *     StructClass[arg, ...]                 -> obj
+ *     DataClass.new(arg, ...)             -> obj
  *
- *  Creates a new class, named by <i>aString</i>, containing accessor
- *  methods for the given symbols. If the name <i>aString</i> is
- *  omitted, an anonymous structure class will be created. Otherwise,
- *  the name of this struct will appear as a constant in class
- *  <code>Struct</code>, so it must be unique for all
- *  <code>Struct</code>s in the system and should start with a capital
- *  letter. Assigning a structure class to a constant effectively gives
- *  the class the name of the constant.
- *
- *  <code>Struct::new</code> returns a new <code>Class</code> object,
+ *  <code>Data::define</code> returns a new <code>Class</code> object,
  *  which can then be used to create specific instances of the new
- *  structure. The number of actual parameters must be
- *  less than or equal to the number of attributes defined for this
- *  class; unset parameters default to <code>nil</code>.  Passing too many
- *  parameters will raise an <code>ArgumentError</code>.
+ *  data structure. The number of actual parameters must be
+ *  equal to the number of attributes defined for this class.
+ *  Passing too many or too less parameters will raise an
+ *  <code>ArgumentError</code>.
  *
  *  The remaining methods listed in this section (class and instance)
  *  are defined for this generated class.
  *
  *     # Create a structure named by its constant
- *     Customer = Struct.new(:name, :address)     #=> Customer
- *     Customer.new("Dave", "123 Main")           #=> #<struct Customer name="Dave", address="123 Main">
+ *     Customer = Data.new(:name, :address)     #=> Customer
+ *     Customer.new("Dave", "123 Main")         #=> #<data name="Dave", address="123 Main">
  */
 static mrb_value
 mrb_data_s_def(mrb_state *mrb, mrb_value klass)
@@ -219,16 +209,13 @@ mrb_data_initialize(mrb_state *mrb, mrb_value self)
 
   mrb_get_args(mrb, "*!", &argv, &argc);
   n = num_members(mrb, klass);
-  if (n < argc) {
-    mrb_raise(mrb, E_ARGUMENT_ERROR, "struct size differs");
+  if (n != argc) {
+    mrb_raise(mrb, E_ARGUMENT_ERROR, "wrong number of arguments");
   }
 
   for (i = 0; i < argc; i++) {
     mrb_ary_set(mrb, self, i, argv[i]);
   }
-  for (i = argc; i < n; i++) {
-    mrb_ary_set(mrb, self, i, mrb_nil_value());
-  }
   return self;
 }
 
@@ -254,7 +241,7 @@ mrb_data_init_copy(mrb_state *mrb, mrb_value copy)
  *
  *  Equality---Returns <code>true</code> if <i>other_data</i> is
  *  equal to this one: they must be of the same class as generated by
- *  <code>Struct::define</code>, and all values of must be equal
+ *  <code>Data::define</code>, and all values of must be equal
  *  (according to <code>Object#==</code>).
  *
  *     Customer = Data.define(:name, :address, :zip)
@@ -385,15 +372,14 @@ mrb_data_to_s(mrb_state *mrb, mrb_value self)
  *  attributes together, using accessor methods, without having to write
  *  an explicit class.
  *
- *  The <code>Struct</code> class is a generator of specific classes,
+ *  The <code>Data</code> class is a generator of specific classes,
  *  each one of which is defined to hold a set of variables and their
  *  accessors. In these examples, we'll call the generated class
  *  "<i>Customer</i>Class," and we'll show an example instance of that
  *  class as "<i>Customer</i>Inst."
  *
  *  In the descriptions that follow, the parameter <i>symbol</i> refers
- *  to a symbol, which is either a quoted string or a
- *  <code>Symbol</code> (such as <code>:name</code>).
+ *  to a symbol, which is a <code>Symbol</code> (such as <code>:name</code>).
  */
 void
 mrb_mruby_data_gem_init(mrb_state* mrb)