Restore old function names for compatibility; ref #5070

- `mrb_check_intern()` to return `mrb_value`
- `mrb_intern_check()` to return `mrb_sym` [NEW]

Other new functions:

- `mrb_intern_check_cstr()`
- `mrb_intern_check_str()`

1 files changed, 27 insertions, 3 deletions

diff --git a/src/symbol.c b/src/symbol.c
index 9683d2f72..18ea49da5 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -268,7 +268,7 @@ mrb_intern_str(mrb_state *mrb, mrb_value str)
 }
 
 MRB_API mrb_sym
-mrb_check_intern(mrb_state *mrb, const char *name, size_t len)
+mrb_intern_check(mrb_state *mrb, const char *name, size_t len)
 {
   mrb_sym sym;
 
@@ -278,16 +278,40 @@ mrb_check_intern(mrb_state *mrb, const char *name, size_t len)
   return 0;
 }
 
+MRB_API mrb_value
+mrb_check_intern(mrb_state *mrb, const char *name, size_t len)
+{
+  mrb_sym sym = mrb_intern_check(mrb, name, len);
+  if (sym == 0) return mrb_nil_value();
+  return mrb_symbol_value(sym);
+}
+
 MRB_API mrb_sym
+mrb_intern_check_cstr(mrb_state *mrb, const char *name)
+{
+  return mrb_intern_check(mrb, name, strlen(name));
+}
+
+MRB_API mrb_value
 mrb_check_intern_cstr(mrb_state *mrb, const char *name)
 {
-  return mrb_check_intern(mrb, name, strlen(name));
+  mrb_sym sym = mrb_intern_check_cstr(mrb, name);
+  if (sym == 0) return mrb_nil_value();
+  return mrb_symbol_value(sym);
 }
 
 MRB_API mrb_sym
+mrb_intern_check_str(mrb_state *mrb, mrb_value str)
+{
+  return mrb_intern_check(mrb, RSTRING_PTR(str), RSTRING_LEN(str));
+}
+
+MRB_API mrb_value
 mrb_check_intern_str(mrb_state *mrb, mrb_value str)
 {
-  return mrb_check_intern(mrb, RSTRING_PTR(str), RSTRING_LEN(str));
+  mrb_sym sym = mrb_intern_check_str(mrb, str);
+  if (sym == 0) return mrb_nil_value();
+  return mrb_symbol_value(sym);
 }
 
 static const char*