Check_Type errors

error.c

@@ -909,9 +909,9 @@ static const char builtin_types[][10] = {
     "",				/* 0x17 */
     "",				/* 0x18 */
     "",				/* 0x19 */
-    "Memo",			/* internal use: general memo */
-    "Node",			/* internal use: syntax tree node */
-    "iClass",			/* internal use: mixed-in module holder */
+    "<Memo>",			/* internal use: general memo */
+    "<Node>",			/* internal use: syntax tree node */
+    "<iClass>", 		/* internal use: mixed-in module holder */
 };
 
 const char *
@@ -972,7 +972,7 @@ rb_builtin_class_name(VALUE x)
     return etype;
 }
 
-NORETURN(static void unexpected_type(VALUE, int, int));
+COLDFUNC NORETURN(static void unexpected_type(VALUE, int, int));
 #define UNDEF_LEAKED "undef leaked to the Ruby space"
 
 static void
@@ -1001,20 +1001,28 @@ rb_check_type(VALUE x, int t)
 {
     int xt;
 
-    if (x == Qundef) {
+    if (RB_UNLIKELY(x == Qundef)) {
 	rb_bug(UNDEF_LEAKED);
     }
 
     xt = TYPE(x);
     if (xt != t || (xt == T_DATA && RTYPEDDATA_P(x))) {
+        /*
+         * Typed data is not simple `T_DATA`, but in a sense an
+         * extension of `struct RVALUE`, which are incompatible with
+         * each other except when inherited.
+         *
+         * So it is not enough to just check `T_DATA`, it must be
+         * identified by its `type` using `Check_TypedStruct` instead.
+         */
 	unexpected_type(x, xt, t);
     }
 }
 
 void
 rb_unexpected_type(VALUE x, int t)
 {
-    if (x == Qundef) {
+    if (RB_UNLIKELY(x == Qundef)) {
 	rb_bug(UNDEF_LEAKED);
     }
 

include/ruby/internal/value_type.h

@@ -337,25 +337,17 @@ static inline void
 Check_Type(VALUE v, enum ruby_value_type t)
 {
     if (RB_UNLIKELY(! RB_TYPE_P(v, t))) {
-        goto slowpath;
+        goto unexpected_type;
     }
-    else if (t != RUBY_T_DATA) {
-        goto fastpath;
-    }
-    else if (rbimpl_rtypeddata_p(v)) {
-        /* The intention itself is not necessarily clear to me, but at least it
-         * is  intentional   to  rule   out  typed   data  here.    See  commit
-         * a7c32bf81d3391cfb78cfda278f469717d0fb794. */
-        goto slowpath;
+    else if (t == RUBY_T_DATA && rbimpl_rtypeddata_p(v)) {
+        /* Typed data is not simple `T_DATA`, see `rb_check_type` */
+        goto unexpected_type;
     }
     else {
-        goto fastpath;
+        return;
     }
 
-  fastpath:
-    return;
-
-  slowpath: /* <- :TODO: mark this label as cold. */
+  unexpected_type:
     rb_unexpected_type(v, t);
 }