Ensure the name given to Module#set_temporary_name is not a valid constant path

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

common.mk

@@ -17548,6 +17548,7 @@ variable.$(OBJEXT): {$(VPATH)}rubyparser.h
 variable.$(OBJEXT): {$(VPATH)}shape.h
 variable.$(OBJEXT): {$(VPATH)}st.h
 variable.$(OBJEXT): {$(VPATH)}subst.h
+variable.$(OBJEXT): {$(VPATH)}symbol.h
 variable.$(OBJEXT): {$(VPATH)}thread_$(THREAD_MODEL).h
 variable.$(OBJEXT): {$(VPATH)}thread_native.h
 variable.$(OBJEXT): {$(VPATH)}transient_heap.h

spec/ruby/core/module/set_temporary_name_spec.rb

@@ -1,5 +1,4 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/module'
 
 ruby_version_is "3.3" do
   describe "Module#set_temporary_name" do
@@ -14,6 +13,15 @@ ruby_version_is "3.3" do
       m.name.should be_nil
     end
 
+    it "can assign a temporary name which is not a valid constant path" do
+      m = Module.new
+      m.set_temporary_name("a::B")
+      m.name.should == "a::B"
+
+      m.set_temporary_name("Template['foo.rb']")
+      m.name.should == "Template['foo.rb']"
+    end
+
     it "can't assign empty string as name" do
       m = Module.new
       -> { m.set_temporary_name("") }.should raise_error(ArgumentError, "empty class/module name")
@@ -21,7 +29,14 @@ ruby_version_is "3.3" do
 
     it "can't assign a constant name as a temporary name" do
       m = Module.new
-      -> { m.set_temporary_name("Object") }.should raise_error(ArgumentError, "name must not be valid constant name")
+      -> { m.set_temporary_name("Object") }.should raise_error(ArgumentError, "name must not be valid constant path")
+    end
+
+    it "can't assign a constant path as a temporary name" do
+      m = Module.new
+      -> { m.set_temporary_name("A::B") }.should raise_error(ArgumentError, "name must not be valid constant path")
+      -> { m.set_temporary_name("::A") }.should raise_error(ArgumentError, "name must not be valid constant path")
+      -> { m.set_temporary_name("::A::B") }.should raise_error(ArgumentError, "name must not be valid constant path")
     end
 
     it "can't assign name to permanent module" do

variable.c

@@ -35,6 +35,7 @@
 #include "ruby/util.h"
 #include "transient_heap.h"
 #include "shape.h"
+#include "symbol.h"
 #include "variable.h"
 #include "vm_core.h"
 #include "ractor_core.h"
@@ -134,6 +135,38 @@ rb_mod_name(VALUE mod)
     return classname(mod, &permanent);
 }
 
+// Similar to logic in rb_mod_const_get()
+static bool
+is_constant_path(VALUE name)
+{
+    const char *path = RSTRING_PTR(name);
+    const char *pend = RSTRING_END(name);
+    rb_encoding *enc = rb_enc_get(name);
+
+    const char *p = path;
+
+    if (p >= pend || !*p) {
+        return false;
+    }
+
+    while (p < pend) {
+        if (p + 2 <= pend && p[0] == ':' && p[1] == ':') {
+            p += 2;
+        }
+
+        const char *pbeg = p;
+        while (p < pend && *p != ':') p++;
+
+        if (pbeg == p) return false;
+
+        if (rb_enc_symname_type(pbeg, p - pbeg, enc, 0) != ID_CONST) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
 /*
  *  call-seq:
  *     mod.set_temporary_name(string) -> self
@@ -196,8 +229,8 @@ rb_mod_set_temporary_name(VALUE mod, VALUE name)
             rb_raise(rb_eArgError, "empty class/module name");
         }
 
-        if (rb_is_const_name(name)) {
-            rb_raise(rb_eArgError, "name must not be valid constant name");
+        if (is_constant_path(name)) {
+            rb_raise(rb_eArgError, "name must not be valid constant path");
         }
 
         // Set the temporary classpath to the given name: