Turn class variable warnings into exceptions

This changes the following warnings:

* warning: class variable access from toplevel
* warning: class variable @foo of D is overtaken by C

into RuntimeErrors.  Handle defined?(@@foo) at toplevel
by returning nil instead of raising an exception (the previous
behavior warned before returning nil when defined? was used).

Refactor the specs to avoid the warnings even in older versions.
The specs were checking for the warnings, but the purpose of
the related specs as evidenced from their description is to
test for behavior, not for warnings.

Fixes [Bug #14541]

1 files changed, 4 insertions, 4 deletions

diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index a253a222de..2fca2bdd9d 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -989,7 +989,7 @@ vm_get_ev_const(rb_execution_context_t *ec, VALUE orig_klass, ID id, bool allow_
 }
 
 static inline VALUE
-vm_get_cvar_base(const rb_cref_t *cref, rb_control_frame_t *cfp)
+vm_get_cvar_base(const rb_cref_t *cref, rb_control_frame_t *cfp, int top_level_raise)
 {
     VALUE klass;
 
@@ -1002,8 +1002,8 @@ vm_get_cvar_base(const rb_cref_t *cref, rb_control_frame_t *cfp)
 	    CREF_PUSHED_BY_EVAL(cref))) {
 	cref = CREF_NEXT(cref);
     }
-    if (!CREF_NEXT(cref)) {
-	rb_warn("class variable access from toplevel");
+    if (top_level_raise && !CREF_NEXT(cref)) {
+        rb_raise(rb_eRuntimeError, "class variable access from toplevel");
     }
 
     klass = vm_get_iclass(cfp, CREF_CLASS(cref));
@@ -3567,7 +3567,7 @@ vm_defined(rb_execution_context_t *ec, rb_control_frame_t *reg_cfp, rb_num_t op_
 	break;
       case DEFINED_CVAR: {
         const rb_cref_t *cref = vm_get_cref(GET_EP());
-	klass = vm_get_cvar_base(cref, GET_CFP());
+        klass = vm_get_cvar_base(cref, GET_CFP(), 0);
 	if (rb_cvar_defined(klass, SYM2ID(obj))) {
 	    expr_type = DEFINED_CVAR;
 	}