reject numbered parameters from Binding#local_variables

Also, Binding#local_variable_get and #local_variable_set rejects an
access to numbered parameters.

[Bug #20965] [Bug #21049]

proc.c

@@ -499,6 +499,12 @@ bind_local_variables(VALUE bindval)
     return rb_vm_env_local_variables(env);
 }
 
+int
+rb_numparam_id_p(ID id)
+{
+    return (tNUMPARAM_1 << ID_SCOPE_SHIFT) <= id && id < ((tNUMPARAM_1 + 10) << ID_SCOPE_SHIFT);
+}
+
 /*
  *  call-seq:
  *     binding.local_variable_get(symbol) -> obj
@@ -525,6 +531,10 @@ bind_local_variable_get(VALUE bindval, VALUE sym)
     const rb_env_t *env;
 
     if (!lid) goto undefined;
+    if (rb_numparam_id_p(lid)) {
+        rb_name_err_raise("numbered parameter '%1$s' is not a local variable",
+                          bindval, ID2SYM(lid));
+    }
 
     GetBindingPtr(bindval, bind);
 
@@ -574,6 +584,10 @@ bind_local_variable_set(VALUE bindval, VALUE sym, VALUE val)
     const rb_env_t *env;
 
     if (!lid) lid = rb_intern_str(sym);
+    if (rb_numparam_id_p(lid)) {
+        rb_name_err_raise("numbered parameter '%1$s' is not a local variable",
+                          bindval, ID2SYM(lid));
+    }
 
     GetBindingPtr(bindval, bind);
     env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));

spec/ruby/language/numbered_parameters_spec.rb

@@ -90,9 +90,18 @@ describe "Numbered parameters" do
     proc { _2 }.parameters.should == [[:opt, :_1], [:opt, :_2]]
   end
 
-  it "affects binding local variables" do
+  ruby_version_is "".."3.4" do
-    -> { _1; binding.local_variables }.call("a").should == [:_1]
+    it "affects binding local variables" do
-    -> { _2; binding.local_variables }.call("a", "b").should == [:_1, :_2]
+      -> { _1; binding.local_variables }.call("a").should == [:_1]
+      -> { _2; binding.local_variables }.call("a", "b").should == [:_1, :_2]
+    end
+  end
+
+  ruby_version_is "3.5" do
+    it "does not affect binding local variables" do
+      -> { _1; binding.local_variables }.call("a").should == []
+      -> { _2; binding.local_variables }.call("a", "b").should == []
+    end
   end
 
   it "does not work in methods" do

vm.c

@@ -1106,6 +1106,21 @@ rb_vm_env_local_variables(const rb_env_t *env)
     return local_var_list_finish(&vars);
 }
 
+VALUE
+rb_vm_env_numbered_parameters(const rb_env_t *env)
+{
+    struct local_var_list vars;
+    local_var_list_init(&vars);
+    // if (VM_ENV_FLAGS(env->ep, VM_ENV_FLAG_ISOLATED)) break; // TODO: is this needed?
+    const rb_iseq_t *iseq = env->iseq;
+    unsigned int i;
+    if (!iseq) return 0;
+    for (i = 0; i < ISEQ_BODY(iseq)->local_table_size; i++) {
+        numparam_list_add(&vars, ISEQ_BODY(iseq)->local_table[i]);
+    }
+    return local_var_list_finish(&vars);
+}
+
 VALUE
 rb_iseq_local_variables(const rb_iseq_t *iseq)
 {

vm_core.h

@@ -1853,6 +1853,7 @@ rb_vm_make_lambda(const rb_execution_context_t *ec, const struct rb_captured_blo
 
 VALUE rb_vm_make_binding(const rb_execution_context_t *ec, const rb_control_frame_t *src_cfp);
 VALUE rb_vm_env_local_variables(const rb_env_t *env);
+VALUE rb_vm_env_numbered_parameters(const rb_env_t *env);
 const rb_env_t *rb_vm_env_prev_env(const rb_env_t *env);
 const VALUE *rb_binding_add_dynavars(VALUE bindval, rb_binding_t *bind, int dyncount, const ID *dynvars);
 void rb_vm_inc_const_missing_count(void);

vm_eval.c

@@ -2661,11 +2661,31 @@ local_var_list_update(st_data_t *key, st_data_t *value, st_data_t arg, int exist
     return ST_CONTINUE;
 }
 
+extern int rb_numparam_id_p(ID id);
+
 static void
 local_var_list_add(const struct local_var_list *vars, ID lid)
 {
-    if (lid && rb_is_local_id(lid)) {
+    /* should skip temporary variable */
-        /* should skip temporary variable */
+    if (!lid) return;
+    if (!rb_is_local_id(lid)) return;
+
+    /* should skip numbered parameters as well */
+    if (rb_numparam_id_p(lid)) return;
+
+    st_data_t idx = 0;	/* tbl->num_entries */
+    rb_hash_stlike_update(vars->tbl, ID2SYM(lid), local_var_list_update, idx);
+}
+
+static void
+numparam_list_add(const struct local_var_list *vars, ID lid)
+{
+    /* should skip temporary variable */
+    if (!lid) return;
+    if (!rb_is_local_id(lid)) return;
+
+    /* should skip anything but numbered parameters */
+    if (rb_numparam_id_p(lid)) {
         st_data_t idx = 0;	/* tbl->num_entries */
         rb_hash_stlike_update(vars->tbl, ID2SYM(lid), local_var_list_update, idx);
     }