Prohibit instantiation of immediate objects

src/class.c

@@ -1348,6 +1348,9 @@ mrb_instance_alloc(mrb_state *mrb, mrb_value cv)
     mrb_raise(mrb, E_TYPE_ERROR, "can't create instance of singleton class");
 
   if (ttype == 0) ttype = MRB_TT_OBJECT;
+  if (ttype <= MRB_TT_CPTR) {
+    mrb_raisef(mrb, E_TYPE_ERROR, "can't create instance of %S", cv);
+  }
   o = (struct RObject*)mrb_obj_alloc(mrb, ttype, c);
   return mrb_obj_value(o);
 }

src/numeric.c

@@ -13,6 +13,7 @@
 #include <mruby/array.h>
 #include <mruby/numeric.h>
 #include <mruby/string.h>
+#include <mruby/class.h>
 
 #ifdef MRB_USE_FLOAT
 #define trunc(f) truncf(f)
@@ -1265,6 +1266,7 @@ mrb_init_numeric(mrb_state *mrb)
 
   /* Integer Class */
   integer = mrb_define_class(mrb, "Integer",  numeric);                          /* 15.2.8 */
+  MRB_SET_INSTANCE_TT(integer, MRB_TT_FIXNUM);
   mrb_undef_class_method(mrb, integer, "new");
   mrb_define_method(mrb, integer, "to_i", int_to_i, MRB_ARGS_NONE());            /* 15.2.8.3.24 */
   mrb_define_method(mrb, integer, "to_int", int_to_i, MRB_ARGS_NONE());
@@ -1291,6 +1293,7 @@ mrb_init_numeric(mrb_state *mrb)
 
   /* Float Class */
   mrb->float_class = fl = mrb_define_class(mrb, "Float", numeric);                 /* 15.2.9 */
+  MRB_SET_INSTANCE_TT(fl, MRB_TT_FLOAT);
   mrb_undef_class_method(mrb,  fl, "new");
   mrb_define_method(mrb, fl,      "+",         flo_plus,         MRB_ARGS_REQ(1)); /* 15.2.9.3.1  */
   mrb_define_method(mrb, fl,      "-",         flo_minus,        MRB_ARGS_REQ(1)); /* 15.2.9.3.2  */

src/object.c

@@ -8,6 +8,7 @@
 #include <mruby/class.h>
 #include <mruby/numeric.h>
 #include <mruby/string.h>
+#include <mruby/class.h>
 
 MRB_API mrb_bool
 mrb_obj_eq(mrb_state *mrb, mrb_value v1, mrb_value v2)
@@ -265,6 +266,7 @@ mrb_init_object(mrb_state *mrb)
   struct RClass *f;
 
   mrb->nil_class   = n = mrb_define_class(mrb, "NilClass",   mrb->object_class);
+  MRB_SET_INSTANCE_TT(n, MRB_TT_TRUE);
   mrb_undef_class_method(mrb, n, "new");
   mrb_define_method(mrb, n, "&",    false_and,      MRB_ARGS_REQ(1));  /* 15.2.4.3.1  */
   mrb_define_method(mrb, n, "^",    false_xor,      MRB_ARGS_REQ(1));  /* 15.2.4.3.2  */
@@ -274,6 +276,7 @@ mrb_init_object(mrb_state *mrb)
   mrb_define_method(mrb, n, "inspect", nil_inspect, MRB_ARGS_NONE());
 
   mrb->true_class  = t = mrb_define_class(mrb, "TrueClass",  mrb->object_class);
+  MRB_SET_INSTANCE_TT(t, MRB_TT_TRUE);
   mrb_undef_class_method(mrb, t, "new");
   mrb_define_method(mrb, t, "&",    true_and,       MRB_ARGS_REQ(1));  /* 15.2.5.3.1  */
   mrb_define_method(mrb, t, "^",    true_xor,       MRB_ARGS_REQ(1));  /* 15.2.5.3.2  */
@@ -282,6 +285,7 @@ mrb_init_object(mrb_state *mrb)
   mrb_define_method(mrb, t, "inspect", true_to_s,   MRB_ARGS_NONE());
 
   mrb->false_class = f = mrb_define_class(mrb, "FalseClass", mrb->object_class);
+  MRB_SET_INSTANCE_TT(f, MRB_TT_TRUE);
   mrb_undef_class_method(mrb, f, "new");
   mrb_define_method(mrb, f, "&",    false_and,      MRB_ARGS_REQ(1));  /* 15.2.6.3.1  */
   mrb_define_method(mrb, f, "^",    false_xor,      MRB_ARGS_REQ(1));  /* 15.2.6.3.2  */

src/symbol.c

@@ -10,6 +10,7 @@
 #include <mruby/khash.h>
 #include <mruby/string.h>
 #include <mruby/dump.h>
+#include <mruby/class.h>
 
 /* ------------------------------------------------------ */
 typedef struct symbol_name {
@@ -481,6 +482,8 @@ mrb_init_symbol(mrb_state *mrb)
   struct RClass *sym;
 
   mrb->symbol_class = sym = mrb_define_class(mrb, "Symbol", mrb->object_class);                 /* 15.2.11 */
+  MRB_SET_INSTANCE_TT(sym, MRB_TT_SYMBOL);
+  mrb_undef_class_method(mrb,  sym, "new");
 
   mrb_define_method(mrb, sym, "===",             sym_equal,      MRB_ARGS_REQ(1));              /* 15.2.11.3.1  */
   mrb_define_method(mrb, sym, "id2name",         mrb_sym_to_s,   MRB_ARGS_NONE());              /* 15.2.11.3.2  */